PUR vs. PIR: Know the Difference

by Manufacturers, Producers, Suppliers Apr 15, 2023

Insulation panels PIR (Polyisocyanurate)
Insulation panels PIR (Polyisocyanurate) are systems for continuous lamination lines for the production of sandwich panels (refrigerators, isothermal chambers, industrial insulation)

Close relatives share a family history, but rarely have the same personality. Insulation is similar in that PUR and PIR are close in chemical composition but vary in performance. While their composition makes them different, some properties that make them similar are that they both are lightweight with low thermal conductivity, and, therefore, help improve the energy efficiency of buildings by significantly reducing energy needs associated with heating and cooling.

PUR foams are essentially made by reacting a “polyol” component and an “iso” component in which the OH groups of the polyol component chemically balance the NCO groups of the iso component and form urethane linkages. In PIR foams, the iso components react with each other in trimerization reactions to form isocyanurates. Excess iso reacts with polyol to form urethane linkages as well.

Anyone who makes insulation boards for cold storage will know about polyurethane insulation boards. So here we will introduce PIR foam and PUR foam to everyone,
PIR
PIR, full name Polyisocyanate Foam, Chinese name is “polyisocyanate”, also known as “polyisocyanurate”, also known as “polyisocyanurate foam PIR” or “tri polyester PIR”. PIR is a kind of foaming material made by reacting isothio cyanate with polyether through catalyst, which has better physical and fire resistance than ordinary polyurethane. It is an ideal organic low-temperature insulation material with low thermal conductivity, lightweight shock resistance, and strong adaptability. Widely used for thermal insulation in refineries, chemical plants, ethylene, fertilizers, cold storage, and construction industries. Also known as a protein database.
PUR
PUR, full name Polyurethane (polyurethane), is a polymer with carbamate chain segment repeating structural units, which is made by the reaction of isocyanate and polyol. It has excellent material performance, wide applications, and a wide variety of products, among which PUR foam is the most widely used. PUR products are divided into foam products and non foam products. Foam products include soft, hard and semi hard PUR foam plastics; Non foaming products include coatings, adhesives, synthetic leather, elastomers, and elastic fibers.
PIR performance is superior to PUR
The fire resistance of 1PIR is superior to that of PUR and the mechanism behind the difference in fire resistance performance:
PUR and PIR are two foam systems. Polyols are divided into polyester polyols and polyether polyols. PUR is a foam system formed by the reaction of polyether polyols and isocyanates. PIR is formed by the reaction of polyester polyols and isocyanates. The isocyanate index of PUR board is usually between 110 and 120, and the crosslinking degree of PUR foam system mainly depends on the functionality of polyether polyol. However, with the increasingly strict requirements for fire rating, PUR foam is facing a huge challenge in the fire prevention specification. Usually, in order to meet the requirements of fire prevention specifications, a large number of flame retardants will be added to the formula system, but at the same time, it will affect the compression strength, dimensional stability and other physical properties of foam, and increase the cost of the product.
The degree of crosslinking of PIR system depends on the trimerization of excessive isocyanate. Generally, the isocyanate index reaches 200~300. Under the action of the corresponding catalyst, the excessive isocyanate can self react to form six membered rings, provide crosslinking for the foam collective, and at the same time promote combustion and coking through its own six membered ring molecular structure, so as to improve the fire resistance of the foam system

PIR reaction is simple and can use low-cost raw materials
3 PIR can provide products with better high and low temperature dimensional stability, lower thermal decomposition rate, and form a protective carbon layer during the combustion process
The mechanical strength of PIR is better than that of PUR
The production efficiency of 5 PIR is relatively high.
The shortcomings of PIR compared to PUR
High brittleness, lower fluidity than PUR
Poor adhesion, with a bonding force of only 1/2 of PUR to the painting material
3 PIR has a rapid secondary foaming performance, which can affect the surface performance of the board
Poor surface ripening, late post ripening
The process range is relatively narrow (production temperature above 60 ℃), making production difficult to control. In the continuous PIR sheet production, the control of equipment and external environment is crucial to the quality of the final product. It is necessary to conduct good temperature control for various chemical raw materials, because it has a huge impact on the stability of the entire chemical reaction process and the entire foam forming process

The creation of PUR and PIR

PIR and PUR are both derived from , a plastic material invented by German scientist Otto Bayer and his colleagues in 1937. In 1954, the accidental introduction of water resulted in rigid polyurethane (PUR).

Just 13 years later in 1967, scientists improved upon PUR’s thermal stability and flame resistance to create polyisocyanurate (PIR). In order to create the new type of insulation, scientists induced a chemical reaction at a higher temperature.

The foaming of PUR and PIR occurs with the use of expanding agents: freon, pentane, HFC 245fa, CO2 or water. Additives whith spraying PUR and PIR foams can be used: flame retardants, fillers, dyes, chain extenders, free fluorine gas agents.

PUR was the most prone to decarbonylation (=release of CO), followed by ether PU and PIR.

Which products are suitable for the production of insulation materials?
Sustainability and resource conservation are becoming increasingly important to consumers and manufacturing companies. Consumers are looking for household appliances with the highest possible energy efficiency and for building insulation to save heating energy. It is therefore not surprising that the market for insulation and thus insulating materials is growing.

Two of the key industrially produced insulation materials are made of Polyurethane (PU) and Polystyrene (PS). In order for these to have an insulating effect, they must first be foamed. For this purpose, there are Pentanes on the one hand, and Fluorinated Olefins (HFOs) on the other. Both, but especially the Pentanes, have replaced the partially halogenated hydrocarbons (HCFC), which are particularly harmful to the environment. The alternatives to these two products are only suitable to a limited extent or are not yet available on a large scale.

Although chlorofluorocarbons (CFCs) and hydrochlorofluorocarbons (HCFCs) are no longer permitted in the EU under the Montreal Protocol, HFOs may still be used. In contrast to pentanes, they are not equally available worldwide because they have to be manufactured in a complex way, which only very few manufacturers are able to do. This effort is also reflected in the price. Pentanes and HFOs can be mixed to optimise costs and foam properties, especially energy efficiency.

The production of insulation materials with Pentanes
Pentanes have long been used as blowing agents in Polyurethane (PU) and Polyisocyanurate (PIR) formulations. They have a proven track record and now account for more than 50% of the global market share.

Advantages of Pentanes and Pentane Blends:

High performance
No measurable ozone depletion potential (ODP)
Low impact on global warming (GWP) compared to other blowing agents
Three different isomers can be found on the global market: n-Pentane, iso-Pentane and Cyclopentane. All three have physical differences and are therefore chosen for different applications in the field of insulation.

Based on the polyol components, rigid PUR/PIR foams were produced in the laboratory by mixing 0.3 dm 3 of a reaction mixture in a paper cup. To this end, the respective polyol component, the flame retardant, the foam stabilizer, catalysts and c/i-pentane (30:70) as blowing agent were added and the mixture was stirred briefly.

The benefits of PUR

PUR insulation can be injected into wall cavities to create an energy efficient barrier. The foam is able to reach small spaces to create an air-tight seal. According to the , PUR provides “the best thermal performance of all practical full cavity insulants.”

PUR foam can be continuously sprayed onto any type of surface. It is generally less expensive than other materials, making it ideal for renovations.

In flood prone areas, PUR’s high water resistance can minimize the impact of water damage in wall cavities, since it is a material that does not hold moisture.

The benefits of PIR

Despite PUR’s benefits, PIR insulation builds upon them. PIR (polyisocyanurate), typically cut into boards, can be used in insulated metal panels, wall cavities and as insulated plasterboard. PIR has such a , it requires only half the thickness of other mineral-based insulation products.

PIR, like PUR, is known for use as a low-moisture barrier. The most notable differentiating factor for PIR is its . PIR slows the spread of flames and reduces the smoke emitted from the fire when compared to PUR products.

The future of insulation

While PIR and PUR have been used for decades, there’s another advanced insulation that outshines both in fire protection and thermal performance.

With 11 percent better thermal performance than PIR and up to 60 percent improvement over PUR, it is unrivaled in the market. Its fire resistance meets the highest insurance and regulatory standards.

Thermal_insulation_materials_made_of_rigid_polyurethane_foam

The overall performance of pentane blown rigid polyurethane foams in terms of insulation value and mechanical properties is demonstrated. The low vapor pressure of both normal-pentane and cyclopentane is shown to induce condensation effects. The consequences of condensation in terms of thermal conductivity and dimensional stability are discussed. The effects on the cell gas pressure of the pentane solubility in the polymer matrix are demonstrated and compared with sorption measurements. The solubility is shown not to deteriorate the foam mechanical properties as a function of time. The ageing characteristics of normal -and cyclopentane blown laminates in terms of the thermal insulation value are discussed. Mixtures of normal- and cyclopentane are suggested to be advantageous in view of their ageing profile.

blowing agent, Expandable Polystyrene, PE - POLYETHYLENE, polystyrene foam, polyurethane and polyisocyanurate foam, phenolic foam, polyolefin foam, and elastomeric foam., Polystyrene Manufacturers, Polyurethane

What is the difference between EPS fire resistance levels A, B, and B1?

by Manufacturers, Producers, Suppliers Apr 15, 2023

The difference between EPS fire resistance grades A, B, and B1:

Fire resistance coefficient: Class A is non combustible; Level B is further divided into three levels, with B1, B2, and B3 having different levels of combustion.
Flammability: Class A has zero flammability;, B1 is flame retardant, B2 is flammable, and B3 is flammable.
At present, the common A-grade products in the market include phenolic aldehyde, rock wool, insulation mortar, foam ceramics, foam glass, and foam concrete. At present, the most advantageous A-grade material is foamed concrete, also known as foamed cement.
EPS polystyrene board itself is a flammable material, so it is not a fireproof material in terms of fire rating. So it’s not at all A-level or B1 level. The fire resistance rating of polystyrene boards on the market is only B2 (flammable) and B3 (flammable).
Extended Information:
EPS physical and mechanical properties:
Density
The density of EPS is determined by the expansion ratio of polystyrene particles during the forming stage, which is generally between 10 and 45kg/m3. As EPS used in engineering, its apparent density is generally between 15 and 30kg/m3.
At present, the density of EPS used as lightweight filling material in road engineering is 20kg/m3, which is 1% to 2% of that of ordinary road filling material. Density is an important indicator of EPS, and its mechanical properties are almost directly proportional to its density.
Deformation characteristics
When the confining pressure exceeds 60KPa, the yield strength significantly decreases, which is clearly different from the variation law of the soil. When axial strain ε When a ≤ 5%, regardless of the confining pressure, the volumetric strain ε V is close to axial strain ε a. The lateral deformation of EPS is small, which means the Poisson’s ratio is small.
To minimize post construction settlement, after laying the EPS material layer, fill 1.2m of soil on it for preloading. The average compressive settlement of the EPS material layer is 32mm, and it can be calculated that the elastic modulus of EPS is 2.4MPa, and the EPS material is still in the elastic deformation stage.
Self-reliance
The self-sustaining nature of EPS is very beneficial for the stability of high slopes. Due to the small lateral pressure generated by the vertical compression of EPS, the use of EPS as filling material for the roadbed at the bridge head can greatly reduce the soil pressure behind the abutment, which is very beneficial for the stability of the abutment.
The friction coefficient f between EPS block and sand is 0.58 (dense)~0.46 (loose) for dry sand and 0.52 (dense)~0.25 (loose) for wet sand; The range of f between EPS blocks is between 0.6 and 0.7.
Water and temperature characteristics
The closed cavity structure of EPS determines its good insulation performance. Its biggest characteristic when used as insulation material is its extremely low thermal conductivity, with various specifications of EPS boards having thermal conductivity ranging from 0.024W/m.K to 0.041W/m.K. EPS is a thermoplastic resin that should be used below 70 ℃ to avoid thermal deformation and strength reduction.
Simultaneously utilizing this feature, electric heating wire processing can be used. Flame retardants can be added in production to form flame retardant EPS. Flame retardant EPS extinguishes itself within 3 seconds after leaving the ignition source. Due to the much lower bulk density of EPS compared to soil, the 1% to 10% increase in bulk density caused by water absorption can have negligible impact on engineering.
Durability
EPS has stable chemical properties in water and soil, and cannot be decomposed by microorganisms; The cavity structure of EPS also makes water infiltration extremely slow; If exposed to ultraviolet radiation for a long time, the surface of EPS will change from white to yellow, and the material will appear brittle to some extent; EPS has stable properties in most solvents, but can be dissolved in organic solvents such as gasoline, diesel, kerosene, toluene, acetone, etc. This indicates that EPS fillers require a good protective layer.

Reference Source: JUNYUAN PETROLEUM GROUP – EPS Blowing Agent Department (Folystyrene Foam)

Expandable polystyrene (EPS)

Revolutionary patented polystyrene production method

Expandable polystyrene (EPS) consists of polystyrene micro-pellets or beads containing a blowing agent and other additives for foaming. We have developed a continuous production process in which the blowing agent is directly injected into the melt, combined with subsequent underwater pelletization.

Commercial EPS is manufactured with the addition of a blowing agent, typically a chlorinated hydrocarbon or a low-boiling petroleum-derived agent with the presence of pentane. These substances are highly flammable; by reducing the amount of flame retardant due to the addition of gypsum, they ignited during the flame propagation test, increasing the burn rate of the GPS.

Main benefits

The patented EPS process is economical, compact, and easy to operate
Continuous process for consistent product quality
Dispersing a wide range of additives and pigments is possible
Minimized waste production
Reduction of wastewater and process water
Recycling possibility for waste EPS pellets/beads/foam
Process allows developing innovative applications

Main applications

Expandable Polystyrene

EPS Panel

The self-extinguishing, fire-retardant EPS Panel foam is manufactured from 100% virgin bead and oven-cured after manufacture to ensure the resulting blocks are completely dry and free from all residual pentane.

EPS Panel is a lightweight, CFC-free, non-brittle, closed cell insulator with more consistent thermal performance over time. It has a high dimensional stability and low water vapor transmission.

A special chemical coated to the Expanded Polystyrene beads (raw material) distinguished it from standard/common EPS Panel. Fire-Retardant EPS Panel is a self-extinguishing, non-combustible material.

Fire-retardant EPS Panel with a density of 15 kg/m3 is used for clean rooms, food processing facilities and modular buildings, while the 20 kg/m3 is used for industrial and commercial cold storage.

Core

Width (cover mm)
Thickness (mm)
Length
Exterior Facing Skin
Internal Facing Skin
Standard Colors
Joint System
Finishes
Type of SkinEPS
(Expanded Polystyrene)
1,160
50, 75, 100, 125, 150, 200, 250
Up to 12 meters
0.5mm, 0.6mm G300 CRP Steel
0.5mm, 0.6mm G300 CRP Steel
Off White
Slip Joint
Plain, Ribbed, Diamond
Anti Bacterial (AB)
Food Grade (FG)
Xterior Roof and Wall (XRW)

Features and Advantages

Fire retardant
Meets safety requirements
Energy saving
Longer lifetime
Resistant to termites and rodents
Customized design
Easy to install saving cost of installation time
High performance on insulated panel

Polyurethane

Pentane as Blowing Agent in PUR foam and PU Market in China

by Manufacturers, Producers, Suppliers Sep 12, 2022

Preface

Pentane as blowing agent in PUR foam: in polyurethane foaming, the main function of foaming agent is to generate gas and form fine bubbles evenly distributed in polyurethane. The blowing agent itself does not participate in the chemical reaction between the polyisocyanate and the combined polyether. The foaming process using freon (such as R11 and R12) as foaming agent is called fluorofoaming. The foaming process in which the foaming agent does not contain Freon is called fluorine-free foaming. Such as Cyclopentane foaming.

Polyurethane

Polyurethane (PU), with the full name of polyurethane, is a polymer compound. It was made by Otto Bayer in 1937. Polyurethane is divided into polyester type and polyether type. They can be made into polyurethane plastics (mainly foamed plastics), polyurethane fibers (called spandex in China), polyurethane rubber and elastomers.

Soft polyurethane mainly has a thermoplastic linear structure. It has better stability, chemical resistance, resilience and mechanical properties than PVC foam materials, and has less compression deformation. Good heat insulation, sound insulation, earthquake resistance and anti-virus performance. Therefore, it is used as packaging, sound insulation and filtering material. Rigid polyurethane plastic is light, sound insulation, excellent thermal insulation performance, chemical resistance, good electrical performance, easy to process, and low water absorption. It is mainly used as structural material for building, automobile, aviation industry and thermal insulation. The performance of polyurethane elastomer is between plastic and rubber, which is oil resistant, wear-resistant, low-temperature resistant, aging resistant, high hardness and elasticity. It is mainly used in the shoemaking industry and medical industry. Polyurethane can also be used to make adhesives, coatings, synthetic leather, etc.

Polyurethane appeared in the 1930s. After nearly 80 years of technological development, this material has been widely used in the field of home, construction, daily necessities, transportation, home appliances and so on.

Name in Chinese: 聚氨酯
English Name: Polyurethane
Abbreviation: PU
Main products: polyurethane foam, spandex, polyurethane coatings, adhesives, etc
Characteristics: oil resistance, wear resistance, low temperature resistance, aging resistance, high hardness and elasticity
Applications: home, construction, daily necessities, transportation, home appliances, etc

Pu Development Overview

Polyurethane (PU) was first developed by German scientists in the 1930s. German scientists polycondensated liquid isocyanate and liquid polyether or glycol polyester to form a new material. The physical performance parameters of this material are different from those of polyolefin materials at that time. Scientists named it polyurethane. With the end of the Second World War, the chemical manufacturing industry in the United States flourished, and polyurethane soft foam was synthesized in the 1950s. This was an important landmark research in the chemical industry at that time, and provided a solid technical foundation for the development of the polyurethane industry in the future.

Global PU Market

The global polyurethane market is mainly distributed in developed countries in Europe and America, and the Asia Pacific region is mainly represented by China, Japan and South Korea. The above countries and regions account for 90% of the global polyurethane market, of which China’s total polyurethane consumption accounts for half of the world. There are many kinds of polyurethane products in the world and they are applied in various fields. By the end of 2016, the total global output of polyurethane had reached about 22 million tons.

PU market in China

China’s polyurethane industry is mainly concentrated in the Yangtze River Delta. In recent years, with the continuous development of industrial manufacturing technology, the Bohai Sea Rim production area, the Pearl River Delta production area and the northwest manufacturing industry base centered on Yantai are all booming. Under the pressure of China’s environmental protection, various enterprises began to seek transformation, taking the creation of a green and environmentally friendly polyurethane production process as the main development direction, and gradually eliminating backward production capacity. It is estimated that in the next few years, China’s polyurethane products will be mainly used in the construction field, furniture field and sports field. By 2016, China’s Polyurethane consumption has reached 11 million tons, creating about 350 billion yuan of direct economic benefits for China.

Market Overview of Main Raw Materials

The main raw materials of polyurethane include diphenylmethane diisocyanate (MDI), toluene diisocyanate (TDI) and polypropylene glycol (PPG), which have become international commodities. The production technology and equipment of these raw materials are very complex, and the product competition is quite fierce. As a result of long-term development, the production is relatively concentrated.

Isocyanate is the general name of various esters of isocyanate. If classified by the number of – NCO groups, it includes monoisocyanates R-N = C = O, diisocyanates o = C = n-r-n = C = O and polyisocyanates; It can also be divided into aliphatic isocyanates and aromatic isocyanates. At present, aromatic isocyanates are used most, such as MDI and TDI.

（1）MDI

MDI’s production technology and equipment requirements are relatively complex, and the production technology is controlled by several giant enterprises in the world. More than 95% of the world’s MDI production enterprises are concentrated in Asia and Europe. Compared with the two, the growth rate of the European market is not as fast as that of Asia, but its MDI industry started early and the market is relatively mature.
On June 1, 2015, the China South Korea free trade agreement was formally signed, which changed the tariff rate of polyurethane raw materials. The export tariff rate of China’s polymerized MDI fell faster than the import tariff rate. With the increase of domestic aggregate MDI market capacity and output, import dependence will decrease and export dependence will increase. The implementation of China South Korea free trade agreement will have a greater impact on China’s aggregate MDI exports than on aggregate MDI imports.

（2）TDI

In 2015, the trend of TDI prices in various regions of China fluctuated greatly, and the firm offer of manufacturers became the only driving force for the rise of TDI prices. However, affected by demand, the trend declined several times and broke new lows repeatedly. The price range in 2015 was lower than that in the previous two years, and the high level of TDI market no longer exists. In addition, the overall operating rate of domestic TDI manufacturers in 2015 was lower than that in 2014, which led to a much smaller output.

（3）PPG

PPG is one of the main raw materials for the production of polyurethane products, and its use in polyurethane foam can reach more than 90%, accounting for the largest proportion. Due to the large scale of polyether polyol production units, the production capacity is mainly concentrated in several large multinational companies such as BASF, Bayer, Dow Chemical and shell. China’s polyether polyol manufacturers have only formed a certain scale through technology introduction and independent research and development. In recent years, with the expansion of production of large manufacturers, the varieties and specifications of polyether polyols are basically complete, and the product quality and stability are also greatly improved.

Pu Product Classification

Polyurethane products mainly include the following: foamed plastics, elastomers, fiber plastics, fibers, leather shoe resins, coatings, adhesives and sealants, among which foamed plastics account for the largest proportion.

Polyurethane Foam
Polyurethane foam is divided into hard foam and soft foam, which have excellent elasticity, elongation, compressive strength and softness, as well as good chemical stability. In addition, polyurethane foam has excellent processability, adhesiveness, thermal insulation and other properties, which belongs to the buffer material with excellent performance.

The production of polyurethane materials has spread all over North America. It is reported that the overall average annual growth rate of polyurethane foam Market in North America is expected to reach about 6%. It is estimated that by 2020, the growth areas will mainly focus on the market of spraying polyurethane foam applications in residential and industrial areas, as well as military applications. In addition, polyurethane will also be used in the medical industry to treat wounds in a timely and effective manner.

Polyurethane Elastomer
Polyurethane elastomer has soft and hard segments in its structure, so it can give materials excellent properties such as high strength, good toughness, wear resistance and oil resistance through the design of molecular chains. Polyurethane, known as “wear-resistant rubber”, has both the high elasticity of rubber and the rigidity of plastic.

In the past year, due to the sharp drop in crude oil prices, and against the background of the global economic depression, the year-on-year growth of China’s polyurethane elastomer market was slower than that of previous years. The imbalance between supply and demand led to a serious downturn in the price of polyurethane elastomer. However, this phenomenon only occurs in traditional polyurethane products. The market prospect of elastomer products with high scientific and technological content and high innovation degree, such as nano polyurethane elastomer materials, is still very considerable.

Polyurethane Fiber Plastic

In 2015, the overall price of the spandex market fell all the way, and the price of all specifications of spandex silk has fallen to the lowest point in history, and has even broken the new low in history. By the end of 2015, the mainstream quotation of 40d spandex was as low as about 36000 yuan / T, a decrease of 25.47% over the beginning of the year, creating a new historical low in the cycle.

From the upstream and downstream of the industrial chain, the current situation of polyurethane fiber plastics is constrained by the continued depression of the economic environment, and the production and sales in the downstream manufacturing field are not strong, with supply exceeding demand and serious pressure on goods; On the other hand, it is also due to the sharp decline in raw material prices.

The price of spandex has fallen all the way, leading to a decline in industry profits. The continuous release of new intelligent production capacity has caused oversupply, which has also strongly impacted the spandex market. Coupled with the shortage of funds in the downstream industry of spandex and the vicious circle of the industrial chain, the import volume of spandex in China plummeted from January to November 2015, and the contradiction between supply and demand has become a hard wound of the decline in spandex prices.

PU Coating

Application Status

Since the 1950s, China began to develop and apply polyurethane coatings. With the continuous improvement and improvement of the material living standards of the public, the development speed of a series of industries such as automobile processing, furniture manufacturing and processing, petrochemical industry, machinery industry, bridges and ships is constantly improving. Polyurethane coatings, with its outstanding performance advantages, have begun to enter a new stage of rapid development. According to statistical data, from 1980 to 2004, the use of polyurethane coatings in various industries showed a very rapid development trend. The total use of polyurethane coatings has achieved a breakthrough development from 1,700 to 200,000 tons. The output of polyurethane coatings is second only to alkyd resin coatings, acrylic resin coatings and phenolic resin coatings, and has become the fourth largest variety in the coating field, And this development trend continues to this day, and its output and use range still maintain a very rapid development trend.

Among the production and processing enterprises of polyurethane coatings, the enterprises responsible for the R & D and application of polyurethane coatings are mostly concentrated in the Pearl River Delta and Yangtze River Delta. Up to now, more than 60 kinds of polyurethane coatings have been developed. It should be noted that, influenced by factors such as capital investment and technological development, most of the development enterprises related to polyurethane coatings are mainly joint ventures, wholly foreign-owned enterprises and domestic large-scale production enterprises. The market positioning is mainly middle and high-grade goods, while township enterprises are mostly low-grade products.

Polyurethane Coating

From the perspective of the R & D and application of polyurethane coatings, the most mainstream is still the two-component polyurethane coatings, whose application range in wood furniture coating and other fields is constantly expanding and improving. In addition, one-component polyurethane coatings still have very strong application advantages in the fields of automobile processing, basement waterproofing and so on. This kind of coatings takes polyurethane as the main material and has very good application value in the production of various paints and varnishes. The newly developed acrylic polyurethane paint uses biuret as curing agent, and its application value in automotive repair paint is quite reliable. Especially for light vehicles, large buses and vans, the coating function in vehicle processing is very worthy of recognition, and the market prospect is considerable. A variety of new polyurethane coatings developed on the basis of acrylic polyurethane coatings can also play an application value in other manufacturing and processing fields to meet the processing quality requirements of processed goods such as household appliances and trains.

In addition, special polyurethane coatings that can be applied to floor coating, machine tool coating, aerospace equipment surface coating and other fields are in the accelerated development and research stage. In relevant reports, the classification, characteristics and application fields of polyurethane coatings are reviewed and analyzed.

R & D Progress

(1) Waterborne polyurethane coating

In 1942, shlack successfully prepared cationic waterborne polyurethane for the first time. In the 1970s, the industrial production of waterborne polyurethane began. Now, the annual output of waterborne polyurethane esters in the world is about 50000-60000 tons. Water is selected as the dispersion medium of waterborne polyurethane coatings, and there are few organic solvents in the whole polyurethane coating structure system, which meets the energy conservation and emission reduction requirements of the current environmental protection in the coating field. Therefore, the application and development of waterborne polyurethane coatings in related fields are increasingly concerned and valued by people in the industry. Up to now, although the application proportion of polyurethane coatings in the whole coating field in China is only about 4%, the engineering application of water-borne polyurethane coatings is maintaining a growth rate of nearly 10% in recent years. In general, the waterborne polyurethane coating does not need to add additional dispersant or emulsifier, and the molecular size and molecular structure can be adjusted as appropriate. In view of this feature, compared with latex coatings widely used in the traditional sense, waterborne polyurethane coatings can have better low-temperature film-forming characteristics, without adding plasticizers and film-forming AIDS in the same proportion. Compared with other coatings, waterborne polyurethane coatings not only have a good appearance, but also have a short drying time, which shows unique advantages in the field of wood coatings. The traditional solvent based acrylic leather coating has been gradually replaced by waterborne polyurethane leather coating. With its advantages in chemical resistance and low temperature resistance, it has attracted the attention of people in the field of leather coating. In addition, this kind of material also plays a very precise application value in the fields of plastics, vehicles, industry and corrosion protection, and has a very broad development space.

There are still some limitations in the performance of waterborne polyurethane coatings, and the lack of water resistance is one of the most important factors affecting the application of waterborne polyurethane coatings in practice. In addition, there are also some problems in the application of water-based polyurethane coatings during the construction of the project. For example, for the two-component water-based polyurethane coatings, the drying speed is relatively slow after being mixed into the construction raw materials, which requires a long time of maintenance. The carbon dioxide bubbles generated during the reaction between the waterborne polyurethane coating and water may remain in the coating film in large quantities, affecting its performance. Moreover, the high cost has also become one of the main factors affecting the industrial application of waterborne polyurethane coatings. More importantly, in water-based polyurethane coatings, a large amount of water-based coatings may affect the iron base materials in engineering buildings, resulting in flash corrosion, and even affecting the wettability and appearance performance of surface coatings. In view of the above problems, in order to promote the further development of water-based polyurethane coatings, composite modified water dispersion polyurethane coatings should be taken as the development direction and research focus in the future, and some molecular structures with special functions, such as silicon-containing polymer chains and fluoropolymer chains, should be introduced into the polyurethane chains to improve the comprehensive performance of the film and give play to its advantages in high temperature resistance, water resistance and weather resistance. Low VOC and high-performance two-component waterborne polyurethane coatings can also be taken as the focus of research and development to reduce the cost of polyurethane coatings and improve the efficiency of use.

(2) Modified polyurethane coating

For the relatively single polyurethane coating, in the process of industrial production and application, its shape, gloss, water resistance and hardness still have certain limitations, so we can try to improve its performance level by developing modified polyurethane coating. At the current technical level, there are two types of modification methods that can be applied to polyurethane materials: the first is to make polyurethane coatings have two or more characteristics through chemical intervention; The second is to mix two or more kinds of resin materials with complementary characteristics through physical intervention, so that polyurethane coatings can have diverse properties. Among them, for silicone materials, this material has a series of characteristics and advantages such as non-corrosion, non-toxic, flame resistance, ozone resistance, weather aging resistance, electrical insulation, etc., and has a very good application value in the modification processing of polyurethane coatings. Bayer company took the lead in the basic research and development of polyurethane powder coatings, and successfully developed a closed isocyanate crosslinking system. The commonly used IPDI curing system closed by caprolactam has a curing temperature of more than 170 ℃. This high-temperature curing is conducive to the high leveling of the coating film and is a variety without volatile by-products. Previous reports also pointed out that trying to combine silicone materials with polyurethane coatings and applying appropriate methods to modify and process can obviously overcome the performance defects of polyurethane materials, which has a very definite value for expanding the application field of polyurethane materials. At the same time, polysiloxane has a special chemical structure, which shows excellent stability, biocompatibility, electrical insulation and high and low temperature resistance. It has been widely used in industrial production practice since the 1940s. In the research and development process of modified polyurethane materials, polysiloxane can be used as a soft segment to synthesize polysiloxane polyurethane block copolymer, so as to highlight the advantages of polyurethane and polysiloxane, and highlight the outstanding advantages of the modified polyurethane coating in surface enrichment, dielectric property and biocompatibility, It has great application space and development potential.

(3) Environmental friendly polyurethane coating

Affected by the requirements of environmental protection and the sustainable development of the entire coating industry, relevant personnel in the industry must actively explore and develop polyurethane coating products with environmental protection benefits, such as UV curable polyurethane coatings, high solid content and low viscosity polyurethane materials, and powder polyurethane materials. The polyurethane coating presented in the form of powder can have good physical and mechanical properties and chemical resistance, and also show good appearance. Compared with other polymer materials, waterborne polyurethane dispersion resin materials have a lot of advantages, and meet the requirements of environmental protection. It can be dispersed in water, without favorable isocyanate, non-toxic, and has good adhesion to the substrate. The waterborne two-component polyurethane coating is composed of water-based polyol containing – OH group and low viscosity polyisocyanate curing agent containing – NCO group. The coating performance is mainly determined by the composition and structure of hydroxyl resin.

One component waterborne polyurethane coating is a kind of coating based on waterborne polyurethane resin and water as dispersion medium. The waterborne polyurethane coating modified by crosslinking has good storage stability, film mechanical properties, water resistance, solvent resistance and aging resistance, and is similar to the traditional solvent based polyurethane coating. It should be one of the very important development directions of environmental friendly polyurethane coating. From the perspective of future development trend, polyurethane powder coating has become one of the most mainstream development directions in the whole coating field, and its proportion in various powder coatings and even polyurethane coatings is constantly increasing. For example, for the automotive coating processing market, in the process of coating product development, polyurethane powder coating should be the best choice and development direction. At the same time, through technological innovation and research and development, a new generation of polyurethane powder coating with good adaptability to low temperature environment and no volatile by-products should be developed. This new powder coating has good similarity with two-component solvent-based polyurethane coating in performance, It can be applied to the coating manufacturing and processing field of the new generation of automobile production lines. While ensuring the coating performance, it reflects good environmental protection benefits and has very considerable comprehensive benefits.

PU Adhesive

The synthesis of polyurethane adhesive is based on the unique chemical properties of isocyanate. Isocyanates are compounds containing isocyanate groups (-nco) in their molecules, which have a highly unsaturated bond structure with overlapping double bond arrangement and can react with various compounds containing active hydrogen. In the field of polyurethane adhesives, isocyanates containing two or more NCO characteristic groups are mainly used. Polyurethane adhesives are divided into general-purpose isocyanate polyurethane adhesives and yellowing resistant isocyanate polyurethane adhesives according to whether products yellowing occurs under light.

Universal PU Adhesive

General purpose isocyanates, that is, aromatic isocyanates, are the most widely used isocyanates in the polyurethane industry at present. Because the methylene group connected to the benzene ring in the structure is easy to be oxidized to form quinone chromophores, the material will turn yellow. The commonly used general-purpose isocyanates include TDI, MDI and polymethyl polyphenylene isocyanate (Papi). TDI is liquid at normal temperature and is easy to use. It is the earliest isocyanate used in the polyurethane industry.

Yellowing Resistant PU Adhesive
In order to improve the yellowing of polyurethane materials caused by universal isocyanates, the generation of chromophores with benzene ring conjugated quinone structure should be avoided in addition to the use of relevant additives. For this reason, researchers have developed many yellowing resistant isocyanates, such as benzylidene diisocyanate (XDI), hexamethylene diisocyanate (HDI), isophorone isocyanate (IPDI), etc.

Modification of PU Adhesive

Although polyurethane adhesive has excellent performance, it is easy to be affected by external environment such as light, heat, oxygen, water and so on, which reduces its use value. With the development of society, the single performance of polyurethane adhesive can not meet the application needs. The research on the modification of polyurethane adhesive has become a hot field, of which physical modification and chemical modification are the main modification methods.

(1) Physical Modification

Physical modification is mainly a method to improve the performance of polyurethane adhesive by doping some fillers and additives under certain conditions in the preparation process of polyurethane adhesive. Quartz powder has good compatibility with polyurethane adhesive system, which can significantly improve the tensile strength, elongation at break and tear strength of polyurethane adhesive products. The polyurethane adhesive film for food packaging was prepared by ultrasonic dispersing nano boron nitride (BN) in polyol and then reacting with MDI. Compared with the adhesive without nano BN, the water vapor transmission of the film was reduced by 50%, the adhesive strength was increased by 37%, and the peel strength was increased by 7.14%. When SiO2 nanofibers were added to the polyurethane matrix, it was found that the hydroxyl groups on the surface of SiO2 nanofibers formed a close cross-linked structure with polyurethane, which improved the adhesion of the adhesive, the hardness and tensile strength of the adhesive film, but also increased the viscosity of the colloid.

(2) Chemical Modification

Chemical modification is a modification method that changes the type of atoms or atomic groups on the molecular chain and their binding modes through chemical reactions of polymers. Among them, block and graft are common chemical modification methods of polyurethane adhesives. Among them, high-performance epoxy resin modified polyurethane adhesive, acrylate modified polyurethane adhesive and silicone resin modified polyurethane adhesive are the competitive development goals in the industry. Epoxy resin has many advantages, such as good adhesion, corrosion resistance, high strength, etc., but its toughness is poor. Introducing epoxy into polyurethane system can obtain products with better performance. Silane modified polyurethane adhesive can not only improve flexibility, but also avoid the shortcomings of traditional polyurethane adhesive, such as easy foaming after curing and poor adhesion to smooth substrate.

PU Product Applications in Industrial Fields

Furniture Industry

In the furniture industry, wood like materials are one of the main application directions of polyurethane rigid foam. Wood like materials are light in weight and have the same density and strength as wood. When using this material to make furniture, not only will there be no cracks after molding, but also the cost of production and manufacturing can be reduced. With the increasing awareness of national environmental protection, wood like materials will be more applied in the furniture industry, thus replacing the status of natural wood in furniture.

China is a big country in furniture production and processing in the world. According to the total consumption of polyurethane in the furniture industry during the 12th Five Year Plan period; During the “13th five year plan” period, China’s furniture industry still focuses on expanding domestic demand and stimulating urban consumption. With the continuous tightening of China’s real estate policy, the construction speed of affordable housing and low rent housing will continue to accelerate. China’s furniture industry will not be impacted, and the public’s demand for polyurethane will grow at a rate of 5% every year.

Construction Industry

Polyurethane rigid foam is the preferred material used in the field of building insulation. It has simple structure, long product life, high construction efficiency, high fire resistance rating and low comprehensive cost. [3] With the continuous implementation of China’s energy conservation and environmental protection policies, the construction industry will face more severe tests during the 13th Five Year Plan period, and polyurethane rigid foam will be widely used in the field of building insulation. In addition, as an important waterproof coating, polyurethane is widely used in building roofs, exterior walls, roof slabs, basements, kitchen and bathroom rooms, roads and bridges, etc. with the continuous development of rail transit and high-speed railway in China, polyurethane waterproof coating will also be widely used in railway construction. At present (2015), the consumption of polyurethane in China’s construction industry is about 1.25 million tons, accounting for 20% of the total consumption, while the total consumption of developed countries in the same industry is 35%. Combined with data analysis, it is not difficult to find that China’s polyurethane rigid foam still has a great development space in the construction industry.

Footwear and Leather Industry
China is the world’s largest exporter and production base of footwear products, accounting for 60% of the world’s total footwear output. Polyurethane (PU) materials are one kind of polyurethane. In addition, sizing is mainly used to manufacture artificial leather, synthetic leather and other related products.

Current Application Fields of PU Products

Furniture Industry

In the furniture industry, wood like materials are one of the main application directions of polyurethane rigid foam. Wood like materials are light in weight and have the same density and strength as wood. When using this material to make furniture, not only will there be no cracks after molding, but also the cost of production and manufacturing can be reduced. With the increasing awareness of national environmental protection, wood like materials will be more applied in the furniture industry, thus replacing the status of natural wood in furniture.

China is a big country in furniture production and processing in the world. According to the total consumption of polyurethane in the furniture industry during the 12th Five Year Plan period; During the “13th five year plan” period, China’s furniture industry still focuses on expanding domestic demand and stimulating urban consumption. With the continuous tightening of China’s real estate policy, the construction speed of affordable housing and low rent housing will continue to accelerate. China’s furniture industry will not be impacted, and the public’s demand for polyurethane will grow at a rate of 5% every year.

Construction Industry

Polyurethane rigid foam is the preferred material used in the field of building insulation. It has simple structure, long product life, high construction efficiency, high fire resistance rating and low comprehensive cost. With the continuous implementation of China’s energy conservation and environmental protection policies, the construction industry will face more severe tests during the 13th Five Year Plan period, and polyurethane rigid foam will be widely used in the field of building insulation. In addition, as an important waterproof coating, polyurethane is widely used in building roofs, exterior walls, roof slabs, basements, kitchen and bathroom rooms, roads and bridges, etc. with the continuous development of rail transit and high-speed railway in China, polyurethane waterproof coating will also be widely used in railway construction. At present (2015), the consumption of polyurethane in China’s construction industry is about 1.25 million tons, accounting for 20% of the total consumption, while the total consumption of developed countries in the same industry is 35%. Combined with data analysis, it is not difficult to find that China’s polyurethane rigid foam still has a great development space in the construction industry.

Footwear and Leather Industry

China is the world’s largest exporter and production base of footwear products, accounting for 60% of the world’s total footwear output. Polyurethane (PU) materials are one kind of polyurethane. In addition, sizing is mainly used to manufacture artificial leather, synthetic leather and other related products. At present (2015), less than 10% of the polyurethane slurry is used in the sole, which cannot reach the average level of developed countries.

However, with the continuous improvement of China’s industrial production technology, the manufacturing cost of polyurethane slurry will continue to decrease, and its development potential is beyond doubt.

Transportation Industry

There is also a lot of polyurethane in the transportation industry, which mainly includes soft, hard and semi-hard foams, as well as polyurethane elastomers, polyurethane adhesives, polyurethane sealants and polyurethane coatings. The total amount of polyurethane required for a formed car is about 30kg. The use of high-quality polyurethane products in cars is also one of the important factors to measure the grade of cars. China is a big automobile country, ranking first in the world in terms of both the manufacturing quantity of the automobile industry and the car ownership. According to relevant statistics, the annual consumption of polyurethane used in China’s automobile industry is nearly 400000 tons. With the continuous introduction of new energy vehicles, polyurethane consumption in the automotive industry will have a broader growth space.
In addition to the automobile industry, China’s cold chain transportation industry is also another field of polyurethane development. With the continuous improvement of people’s living standards in China, more and more people’s demand for flowers and aquatic products has soared, which has driven the development of China’s cold chain transportation industry. The transport vehicles in the cold chain transportation industry usually use polyurethane hard foam sandwich panels as heat insulation materials. At the same time, a large number of polyurethane heat insulation materials are also required in the construction of cold storage, which is also a great advantage for China’s polyurethane industry.

Home Appliance Industry

Refrigerators and freezers mainly use polyurethane hard foam as the heat insulation material of household appliances. Under the same volume condition, this material can effectively increase the internal volume of refrigerators and freezers and reduce the total amount of external shell materials. It can not only reduce the production cost, but also reduce the weight of refrigerators and improve the heat insulation performance. In China, the weight of polyurethane rigid foam is about 6-8kg to make a refrigerator with standard volume, and about 11kg rigid foam is required for a freezer. China is a big refrigerator manufacturing country, and has gradually become the world’s integrated base of refrigerator R & D, production and transportation; The total amount of polyurethane rigid foam used in refrigerator manufacturing industry in China is about 800000 tons every year. With the continuous implementation of the policy of “energy saving and emission reduction” for household appliances in China, the total amount of polyurethane used in refrigerators will show a downward trend, and all manufacturing enterprises will move towards the development route of “green and environmental protection”.

In addition, the thermal insulation material of solar water heater is also polyurethane rigid foam. China’s solar energy industry is an emerging industry. With the continuous optimization of the energy structure, the solar energy industry will be further developed and polyurethane industrial products will be more favored.

Sports Industry

Polyurethane pavement materials are widely used in the pavement construction of plastic runways, indoor basketball courts and volleyball courts in stadiums and public sports venues. A few years ago, the “toxic runway” incident continued to ferment, resulting in the whole industry being in a low-end and poor competitive state, and many small enterprises operating without licenses wantonly seek profits; With the continuous improvement of the quality of China’s polyurethane industrial products, the quality of polyurethane pavement materials has been greatly improved, and enterprises are constantly on the road to environmentally friendly pavement products.

Other Industries

Polyurethane can also be used for the packaging of fragile goods, especially in the transportation packaging of some precision instruments, handicrafts, fragile goods, etc; This kind of products can also be used in the fields of aviation, aerospace, automobile manufacturing, LNG carrier (ship) manufacturing, etc. (2015), the polyurethane slurry used in the sole is less than 10%, which can not reach the average level of developed countries.

However, with the continuous improvement of China’s industrial production technology, the manufacturing cost of polyurethane slurry will continue to decrease, and its development potential is beyond doubt.

Transportation Industry

There is also a lot of polyurethane in the transportation industry, which mainly includes soft, hard and semi-hard foams, as well as polyurethane elastomers, polyurethane adhesives, polyurethane sealants and polyurethane coatings. The total amount of polyurethane required for a formed car is about 30kg. The use of high-quality polyurethane products in cars is also one of the important factors to measure the grade of cars. China is a big automobile country, ranking first in the world in terms of both the manufacturing quantity of the automobile industry and the car ownership. According to relevant statistics, the annual consumption of polyurethane used in China’s automobile industry is nearly 400000 tons. With the continuous introduction of new energy vehicles, polyurethane consumption in the automotive industry will have a broader growth space.
In addition to the automobile industry, China’s cold chain transportation industry is also another field of polyurethane development. With the continuous improvement of people’s living standards in China, more and more people’s demand for flowers and aquatic products has soared, which has driven the development of China’s cold chain transportation industry. The transport vehicles in the cold chain transportation industry usually use polyurethane hard foam sandwich panels as heat insulation materials. At the same time, a large number of polyurethane heat insulation materials are also required in the construction of cold storage, which is also a great advantage for China’s polyurethane industry.

Home Appliance Industry

Refrigerators and freezers mainly use polyurethane hard foam as the heat insulation material of household appliances. Under the same volume condition, this material can effectively increase the internal volume of refrigerators and freezers and reduce the total amount of external shell materials. It can not only reduce the production cost, but also reduce the weight of refrigerators and improve the heat insulation performance. In China, the weight of polyurethane rigid foam is about 6-8kg to make a refrigerator with standard volume, and about 11kg rigid foam is required for a freezer. China is a big refrigerator manufacturing country, and has gradually become the world’s integrated base of refrigerator R & D, production and transportation; The total amount of polyurethane rigid foam used in refrigerator manufacturing industry in China is about 800000 tons every year. With the continuous implementation of the policy of “energy saving and emission reduction” for household appliances in China, the total amount of polyurethane used in refrigerators will show a downward trend, and all manufacturing enterprises will move towards the development route of “green and environmental protection”.
In addition, the thermal insulation material of solar water heater is also polyurethane rigid foam. China’s solar energy industry is an emerging industry. With the continuous optimization of the energy structure, the solar energy industry will be further developed and polyurethane industrial products will be more favored.

Sports Industry

Polyurethane pavement materials are widely used in the pavement construction of plastic runways, indoor basketball courts and volleyball courts in stadiums and public sports venues. A few years ago, the “toxic runway” incident continued to ferment, resulting in the whole industry being in a low-end and poor competitive state, and many small enterprises operating without licenses wantonly seek profits; With the continuous improvement of the quality of China’s polyurethane industrial products, the quality of polyurethane pavement materials has been greatly improved, and enterprises are constantly on the road to environmentally friendly pavement products.

Other Industries

Polyurethane can also be used for the packaging of fragile goods, especially in the transportation packaging of some precision instruments, handicrafts, fragile goods, etc; This kind of products can also be used in the fields of aviation, aerospace, automobile manufacturing, LNG carrier (ship) manufacturing, etc.

References

Xu Liyi, Zhou Yi. Encyclopedia knowledge data dictionary. Qingdao: Qingdao publishing house. 2008
Wang Daquan. Dictionary of fine chemicals. Beijing: Chemical Industry Press. 1998, pp. 344-345
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Li Cheng, Wu Zigang, Wang Xiaotong, Yan Jing, Shao Kai. Current situation and development trend of polyurethane industry [J]. Bonding, 2016,37 (11): 63-67
Su Yong, Du Wengong, Liu Na, Chen Yaoqing, Wang Weike, Hu Mei. Research status and development exploration of polyurethane coatings [J]. Henan chemical industry, 2018,35 (10): 9-14
Li guozun, Gao Zhixiang, Li Shixue, Li Jianwu, Chen Yu, Zhao Miao. Research progress, synthesis, modification and application of polyurethane adhesive [J]. Bonding, 2019,40 (05): 177-180