1, hydroxyl value: The amount of hydroxyl groups contained in 1 gram of polymer polyol corresponds to the milligrams of KOH in mg KOH / g.
2, equivalent: The average molecular weight of a functional group.
3, Isocyanate content: Isocyanate content in the molecule
4, isocyanate index: The degree of excess isocyanate in a polyurethane formulation, usually indicated by the letter R.
5, chain extender: Refers to the molecular chain can extend, expand or form a network of cross-linked low molecular weight alcohols, amines.
6, hard segment: Polyurethane molecules in the main chain by the isocyanate, chain extender, cross-linking agent formed by the segment, the cohesive energy of these groups larger space larger, more rigid.
7, soft section : Carbon-carbon backbone polymer polyol, better flexibility, flexible segment in the polyurethane backbone.
8, one-step method : Refers to the oligomer polyol, diisocyanate, chain extender and catalyst mixed at the same time directly into the mold, at a certain temperature curing molding method.
9, prepolymer method: First, the oligomer polyol and diisocyanate prepolymerization reaction to produce NCO-terminated polyurethane prepolymer, pouring and then prepolymer and chain extender, the preparation of polyurethane elastomer method, called the prepolymerization Material law.
10, semi-prepolymer method: The difference between the semi-prepolymer method and the prepolymer method is that part of the polyester polyol or polyether polyol is added to the prepolymer as a mixture with a chain extender, a catalyst and the like.
11, reaction injection molding: Also known as reaction injection molding RIM (Reaction Injection Molding), is a low molecular weight oligomers in liquid form of measurement, instantaneous mixing while injected into the mold, and rapid reaction in the mold cavity, the material molecular weight increased rapidly to extremely Fast process of producing new polymers containing new, characteristic group structures.
12, foam index: That is, the fraction of water equivalent to 100 parts of polyether is defined as the foam index (IF).
13, foam reaction: Generally refers to the reaction of water and isocyanate to generate substituted urea, and emit CO2 reaction.
14, gel reaction: Generally refers to the urethane formation reaction.
15, gel time: Under certain conditions, the time required for the liquid substance to form a gel.
16, white time: Toward the end of Zone I, milky phenomena appear in the liquid phase polyurethane blend, which time is referred to as the cream time in polyurethane foam formation.
17, chain expansion coefficient: Refers to the ratio of the amount of amino groups and hydroxyl groups (unit: mo1) in the chain extender component (including the mixed chain extender) to the amount of NCO in the prepolymer, that is, the number of moles of active hydrogen groups to NCO )ratio.
18, low unsaturation polyether: Mainly for the development of PTMG, PPG price, unsaturation reduced to 0.05mol / kg, close to the performance of PTMG, the use of DMC catalyst, the main species Bayer Acclaim products.
19, urethane grade solvent: Production of polyurethane solvent selection to consider the dissolution rate, the rate of evaporation, but the solvent used in the production of polyurethane, should be taken into account the weight of the polyurethane NC0 base can not be used with the reaction of the NCO alcohol, ether alcohol Lou solvent can not contain water , Alcohol and other impurities, can not contain alkali substances, these will make the polyurethane deterioration.
Ester solvents are not allowed to contain water, nor contain free acids and alcohols, it will react with the NCO group. Ester solvents used in polyurethanes should be of high purity "urethane grade solvent." The solvent is reacted with an excess of isocyanate, and then The amount of unreacted isocyanate was measured with dibutylamine and tested for suitability.The principle is that more isocyanates are not suitable because it indicates that the water, alcohol, and acid contained in the ester will consume the total isocyanate value, LeqNCO based on the number of grams of solvent said, the larger the value of good stability.
The isocyanate equivalent of less than 2500 is not used as a polyurethane solvent.
The polarity of the solvent has a great influence on the resin reaction, the larger the polarity is, the slower the reaction is. For example, the difference between toluene and methyl ethyl ketone is 24 times, and the solvent molecule has a large polarity and can form a hydrogen bond with the hydroxyl of the alcohol to make the reaction slow.
Aromatic solvents are preferred solvents for polychlorinated solvents, and their reaction rates are faster than those of esters and ketones, such as xylene. Use of esters and ketones prolongs the pot life of Polyurethanes, When selecting the aforementioned "urethane grade solvent", it is advantageous for the stored stabilizer.
Strong solvent esterification, volatile moderate speed, low toxicity and more use of cyclohexanone are also used, solid solvent hydrocarbon solvent with low ability to use less alone, and more with other solvents.
20, physical blowing agent : Physical foaming agents are foam pores that are formed by the physical form of a substance that is formed by the expansion of a compressed gas, the volatilization of a liquid, or the dissolution of a solid.
21, chemical blowing agent: Chemical blowing agents are compounds that, upon thermal decomposition, release gases such as carbon dioxide and nitrogen and form fine pores in the polymer composition.
22, physical crosslinking: Part of the rigid chain in the polymer soft chain has the same physical properties as those of the chemically crosslinked vulcanizate at temperatures below the softening point or melting point.
23, chemical cross-linking:Refers to the light, heat, high-energy radiation, mechanical force, ultrasound and cross-linking agent under the action of the chemical bond between the macromolecular chains linked together to form a mesh or body structure of the polymer process.
24, foam index: The fraction of water equivalent to 100 parts of polyether is defined as the Foaming Index (IF).
25 commonly used isocyanates from the structural point of what kind?
A: Aliphatic: HDI, alicyclic: IPDI, HTDI, HMDI, aromatic: TDI, MDI, PAPI, PPDI, NDI.
26. What kinds of isocyanates are commonly used? Write the formula
A: Toluene diisocyanate (TDI), diphenylmethane-4,4'-diisocyanate (MDI), polyphenylmethane polyisocyanate (PAPI), liquefied MDI, hexamethylene diisocyanate (HDI).
27. TDI-100 and TDI-80 mean?
A: TDI-100 refers to toluene diisocyanate all composed of 2,4 structure; TDI-80 refers to a mixture of 80% 2,4-structure toluene diisocyanate and 20% 2,6 structure.
28. TDI and MDI in the synthesis of polyurethane materials have their own characteristics?
A: Reactivity for 2,4-TDI and 2,6-TDI 2,4-TDI is several times more reactive than 2,6-TDI because the 4-position NCO in 2,4-TDI 2 NCO and methyl far away, almost no steric hindrance, and 2,6-TDI NCO by the ortho-methyl steric hindrance effect, reactivity affected.
The two NCO groups of MDI are far apart and have no substituents around. Therefore, the activity of both NCOs is relatively large. Even if one of the NCOs participates in the reaction, the remaining NCO activity decreases. In general, Activity is still large, so the reactivity of MDI polyurethane prepolymer than TDI prepolymer.
29.HDI, IPDI, MDI, TDI, NDI yellowing which is better?
A: HDI (a constant yellow aliphatic diisocyanate), IPDI (made of polyurethane resin has excellent optical stability and chemical resistance, generally used in the manufacture of high-grade non-discolouring polyurethane resin).
30.MDI modification purposes and commonly used methods of modification
A liquefied MDI: liquefaction MDI is liquefied modified MDI, it overcomes some of the shortcomings of pure MDI (solid at room temperature, the use should be melted, repeated heating affect performance), but also for the MDI-based polyurethane material Performance improvements and improvements provide the basis for a wide range of modifications.
method:
① urethane modified liquefied MDI.
② carbodiimide (carbodiimide) and uretonimine (uretonimine) modified liquefied MDI.
31. Commonly used polymer polyols which categories?
A: polyester polyols, polyether polyols
32. Polyester Polyols industrial production methods are several?
A: A, vacuum melting method B, carrier gas melting method C, azeotropic distillation method
33. Polyester, polyether polyol molecular backbones What are the special structure?
A: Polyester polyols: Macromolecular alcohols containing an ester group at the main chain of the molecule and a hydroxyl group (-OH) at the terminal group Polyether polyol: An ether bond (-O -), polymers or oligomers with (-OH) or amine groups (-NH2) at the end.
34. According to the characteristics of polyether polyol divided into several categories?
A: High activity polyether polyols, grafted polyether polyols, flame retardant polyether polyols, heterocyclic modified polyether polyols, polytetrahydrofuran polyols.
35. According to the initiator divided into ordinary polyether several?
A: Polyoxypropylene glycol, polyoxypropylene triol, rigid foam polyether polyol, low unsaturation polyether polyol.
36. Hydroxy-terminated polyether and amine-terminated polyether What is the difference?
Terminal amine-based polyethers are polyoxypropylene ethers whose terminal hydroxyl groups are substituted by amine groups.
37. What are the commonly used polyurethane catalysts? What are the several commonly used varieties?
A: The tertiary amine catalyst, commonly used varieties are: triethylenediamine, dimethylethanolamine, N-methylmorpholine, N, N-dimethylcyclohexanamine
Metal alkyl compounds, commonly used varieties are: organic tin catalyst can be divided into stannous octoate, stannous oleate, dibutyltin dilaurate.
38. commonly used polyurethane chain extenders or cross-linking agents have?
A: polyols (1,4-butanediol), alicyclic alcohols, aromatic alcohols, diamines, alcohol amines (ethanolamine, diethanolamine)
39. Isocyanate reaction mechanism
A: The reaction of isocyanates with active hydrogen compounds is caused by attack of NCO-based carbon atoms by the nucleophilic centers in the molecules of active hydrogen compounds. The reaction mechanism is as follows:
How does the isocyanate structure affect the reactivity of NCO groups?
A: Electronegativity of AR groups: If the R group is an electron-withdrawing group, the electron density of the C atom in the -NCO group is further reduced and is more susceptible to attack by nucleophiles, that is, it is easier to react with compounds such as alcohols and amines Nucleophilic reaction.If R is an electron donating group, the electron cloud passing through the electron cloud will increase the electron cloud density of the C atom in the -NCO group, making it less susceptible to the attack of the nucleophile and reacting with the active hydrogen-containing compound B. Induced effect: As the aromatic diisocyanate contains two NCO groups, when the first -NCO gene to participate in the reaction, due to the aromatic ring of the conjugation effect, not participate in the reaction of the -NCO group will play To the role of electron-withdrawing group, so that the first NCO group reactivity increased, this effect is the induction effect C. Sterically hindered effect: In the aromatic diisocyanate molecules, if the two -NCO groups at the same time An aromatic ring, then one of the NCO group on the other NCO group reactivity is often more significant, but when the two NCO groups are located in the same molecule in different aromatic rings, or they are hydrocarbon chain or Aromatic ring separated, so that the phase between them Influence is not large, and increases with increasing length of the hydrocarbon chain or an aromatic ring number is reduced.
41. Active hydrogen compound species and NCO reactivity
A: Aliphatic NH2> Aromatic NH2> Drunk OH> Water> Secondary OH> Phenols OH> Carboxyl> Substituted ureas> Amides> Carbamates. (If the electron density at the nucleophilic center is greater, its electronegativity The stronger it is, the higher its reactivity with isocyanates is, the faster the reaction rate is; otherwise, the activity is low.
42. The effect of hydroxy compounds on its reactivity with isocyanates
A: The reactivity of active hydrogen compounds (ROH or RNH2) is related to the nature of R. When R is the electron-withdrawing group (electronegativity is low), the transfer of hydrogen atoms is difficult and the reaction of active hydrogen compounds with NCO is more difficult. If R is an electron-donating substituent, the reactivity of an active hydrogen compound and NCO can be improved.
43. What is the reaction of isocyanate with water?
A: It is one of the basic reactions to prepare polyurethane foam. The reaction between them first generates unstable carbamic acid and then decomposes to CO2 and amine. If the isocyanate is excessive, the resulting amine will react with the isocyanate to form urea.
44. In polyurethane elastomer preparation, polymer polyol water content should be strictly controlled
A: The elastomer, paint, fiber requirements can not have bubbles, so the moisture content of raw materials must be strictly controlled, usually less than 0.05%.
45. Amines, tin catalyst for the catalytic reaction of isocyanate differences
A: The tertiary amine catalyst for the reaction of isocyanate and water catalytic efficiency, while the tin catalyst for isocyanate and hydroxyl catalytic efficiency.
46. Why polyurethane resin can be regarded as a kind of block polymer, what are the characteristics of the segment structure?
A: Because the polyurethane resin segment is a hard segment and soft segment composition, the hard segment refers to the main chain of polyurethane molecules formed by the reaction of isocyanate, chain extender, cross-linking agent segment, these groups cohesive energy Larger, larger space, more rigid, while the soft segment refers to the carbon-carbon backbone polymer polyol, good flexibility in the polyurethane backbone of the flexible segment.
47. What are the factors that affect the performance of polyurethane materials?
A: The cohesive energy of the group, hydrogen bonding, crystallinity, degree of crosslinking, molecular weight, hard segment, soft segment.
48. Polyurethane material molecules in the main chain of soft segment, hard segment each from what raw materials
A: The soft segment consists of oligomers polyols (polyesters, polyether diols, etc.), hard segments consist of polyisocyanates or their combination with small molecule chain extenders.
49 soft section, hard section how to affect the performance of polyurethane materials?
A: soft segments: (1) the soft segment of the molecular weight: Assuming the same molecular weight of polyurethane, the soft segment if the polyester, the polyurethane strength increases as the molecular weight of polyester diol increased; if the soft segment is polyether, then The strength of polyurethane decreases with the increase of the molecular weight of polyether glycol, but the elongation increases. (2) The softness of the soft segment: It contributes greatly to the crystallinity of the linear polyurethane segments. Generally speaking, the crystallinity It is advantageous to improve the properties of the polyurethane article, but sometimes crystallization reduces the low temperature flexibility of the material, and the crystalline polymer is often opaque.
Hard segments: hard segments usually affect the softening temperature and high temperature properties of the polymer.Polyurethane prepared from aromatic isocyanates has a hard segment with a rigid aromatic ring, which increases the hard segment cohesion strength and generally has a higher strength than the aliphatic isocyanates Polyurethane large, but poor UV degradation, easy to yellow, aliphatic polyurethane will not yellow.
50. Polyurethane foam classification
A: (1) rigid foam and soft foam, ⑵ high density and low density foam, ⑶ polyester, polyether foam, ⑷ TDI, MDI foam, ⑸ polyurethane foam and polyisocyanurate foam, ⑹ step France and prepolymerization production, ⑺ continuous and batch production, ⑻ massive foam and molded foam.
51. Basic reaction to foam preparation
A: Refers to the reaction of -NCO with -OH, -NH2, H2O, and the reaction of polyol, the foaming process of the 'gel reaction' generally refers to the formation of urethane reaction because the foam material using multi-functional Degree of raw materials, is the cross-linked network, which makes the foam system can gel quickly.
Foaming in the presence of water foaming system, the so-called 'foaming reaction', generally refers to the reaction of water and isocyanate to produce substituted urea, and emit CO2.
52. bubble nucleation mechanism
Raw materials react in the liquid or rely on the temperature of the reaction to produce gas and volatilize the gas.With the reaction proceeds and the reaction of a large amount of heat generated, the amount of gas and the amount of volatility continues to increase.When the gas concentration increases over the saturation concentration, Bubbles that begin to form in the solution phase begin to rise.
53. The role of foam stabilizer in polyurethane foam preparation
A: With the emulsifying effect, the mutual solubility between the components of the foam material is enhanced. After the addition of the silicone surfactant, since it greatly reduces the surface tension γ of the liquid, the increase of the free energy required for gas dispersion is reduced and the dispersion The air in the raw material is more easily nucleated during the mixing process, which helps to generate fine bubbles and improve the stability of the foam.
54. Foam stability mechanism
A: The addition of a suitable surfactant helps to create a fine bubble dispersion.
55. Open-cell foam and closed-cell foam formation mechanism
A: The formation of open-cell foam mechanism: In most cases is the maximum pressure in the bubble when the bubble formed by the gel reaction of the wall strength is not high, can not withstand the gas pressure caused by the expansion of the wall film, bubble wall membrane was pulled Break, the gas escaped from the rupture, forming an open cell foam.
Closed-cell foam formation mechanism: For the rigid foam system, due to the use of multi-functional, low molecular weight polyether polyol and polyisocyanate reaction, the gel speed is relatively fast, in the cell gas can not break the bubble wall to form Closed-cell foam.
56. Physical foaming agent and chemical foaming agent foaming mechanism
A: Physical foaming agents: Physical foaming agents are foams. Foam pores are formed by physical changes in a substance, ie, expansion of compressed gas, evaporation of a liquid, or dissolution of a solid.
Chemical foaming agents: Chemical foaming agents are those compounds that, upon thermal decomposition, release gases such as carbon dioxide and nitrogen and form fine pores in the polymer composition.
57. Preparation of flexible polyurethane foam
A: One-step method and prepolymer method
Prepolymer method: Firstly, polyether polyols and excess TDI are reacted to prepare prepolymer containing free NCO groups, and then mixed with water, catalyst, stabilizer and so on to make foam. One - step method: Calculation directly into the mixing head mixing, one-step manufacturing foam, can be divided into continuous and intermittent.
58. Horizontal foam and vertical foam characteristics
A: The level of foam Features: Edge membrane lifting method: This method is based on the original level of foam machine to increase the traction side of the paper device, so that the foam edge and the central up foam, resulting in nearly flat-top foam block. Balance plate method: The feature is the use of the top paper and the top cover. Overflow tank method: characterized by the use of overflow tank and conveyor landing board.
Vertical foam Features: Small flow can get a large cross-sectional area of the foam block, and usually horizontal foam machine to get the same cross-section of the block, the flow level than vertical foam 3 to 5 times larger; due to foam Block cross-section is large, there is no upper and lower skin, side skin is thin, thus greatly reducing the cutting loss; equipment covers an area of ?? small, plant height of about 12 ~ 13m, plant and equipment investment costs lower than the level of foam technology; Cylindrical or rectangular foams can be produced conveniently by changing the hopper and the mold, in particular for the production of circular cut foam blanks.
59. Soft foam preparation of raw materials to choose the basic points
A: Polyol: polyether polyol used for ordinary block foam, the molecular weight is generally 3000 ~ 4000, mainly polyether triol.High rebound foam is the use of polyether triol with a molecular weight of 4500 ~ 6000. When the molecular weight is increased, the tensile strength, elongation and resilience of the foam increase; the reactivity of the same kind of polyether decreases. When the functionality of the polyether is increased, the reaction is relatively faster and the degree of crosslinking of the resulting polyurethane is increased. (TDI-80), while relatively low activity TDI-65 is only used for polyester polyurethane foam or special polyether Type catalyst: the catalyst for the massive soft foam foaming can be roughly divided into two categories: one is the organometallic compounds, most commonly stannous octoate; the other is a tertiary amine, bis (dimethylaminoethyl ) Ether commonly used.Steam stabilizer: In the polyester polyurethane block foam non-silicone surfactant-based, polyether block foam mainly silicone-alkylene oxide copolymer.Foaming agent: Generally in the manufacture of density greater than 21 kg per cubic meter When soft urethane foam blocks, using only water as a blowing agent; only using dichloromethane (MC) and other low-boiling compounds in the formulation as an auxiliary blowing agent of low density.
60. Environmental conditions on the block foam physical properties
A: The effect of temperature: The foaming reaction of polyurethane accelerates with the rise of the temperature of the material, which can cause the danger of burning and ignition in sensitive formulations. Effect of air humidity: With the increase of humidity, The group part reacts with the moisture in the air, the hardness of the foam decreases, and the elongation increases; the tensile strength of the foam increases due to the increase of the urea group. Effects of Atmospheric Pressure: For the same formula, High density foam, the density was significantly reduced.
61. The main difference between raw material systems for cold molded and hot molded foams
A: The raw materials used in cold-curing molding have high reactivity and do not require external heating when curing. The curing reaction can be basically completed in a short period of time by the heat generated by the system, and the raw material can be released within a few minutes after the injection molding. The raw material of the maturation molding foam has low reactivity, and the reaction mixture needs to be heated together with the mold after the foaming in the mold is completed. The foam product can be demolded only after aging in the drying tunnel completely.
62. What are the characteristics of cold molded soft foam compared to hot molded foam
A: The production process without the need to provide external heat, can save a lot of heat; The sigma coefficient (depression ratio) high, comfortable performance, high rebound rate, ④ without flame retardant foam also has some flame retardant ; ⑤ short production cycle, saving mold, cost savings.
63. soft foam and rigid bubble their own characteristics and uses
A: The characteristics of soft foam: Most of the foam structure of polyurethane soft foam is perforated, generally with the features of low density, good elastic recovery, sound absorption, breathability and thermal insulation etc. Uses: Mainly used as furniture, mat material, vehicle seats Cushion materials, various soft cushion laminated composite materials, industrial and civilian soft foam also used as filter materials, noise insulation materials, earthquake-resistant materials, decorative materials, packaging materials and thermal insulation materials.
Rigid foam Features: Polyurethane foam with light weight, high strength, good dimensional stability; polyurethane foam superior thermal insulation properties; strong adhesion; aging performance, long heat insulation life; reaction mixture has good fluidity, can Smoothly filled with complex shapes of cavities or spaces; Polyurethane rigid foam production of high reactivity of raw materials, you can achieve rapid curing, in the factory to achieve high efficiency, high-volume production.
Uses: used as refrigerators, freezers, refrigerated containers, cold storage and other insulation materials, oil pipelines and hot water pipe insulation, building walls and roof insulation, insulation sandwich panels, and so on.
64. foam formula design points
A: Polyols: Polyether polyols used in rigid foam formulations are generally high-functionality, high-OHP (low molecular weight) polyoxypropylene polyols; isocyanates: the most commonly used isocyanates for rigid foams are polymethylene poly (1) CFC blowing agent (2) HCFC and HFC blowing agent (3) Pentane blowing agent (4) Water; Phenyl polyisocyanate Foam Stabilizers: Foam stabilizers used in polyurethane foam formulations are generally block polymers of polydimethylsiloxane and polyalkylene oxide. Most foam stabilizers currently dominate the Si-C type. Catalysts: Hard The formula of the catalyst to tertiary amine-based, in special occasions can be used organic tin catalyst; Other additives: According to polyurethane foam products for different purposes and requirements, but also in the formula by adding flame retardants, cell opener, hair Smoke inhibitors, antioxidants, fungicides, toughening agents and other additives.
65. Whole skin molding foam preparation principle
A: The integral skin foam (also referred to as ISF), also known as self skinning foam (self skinning foam), is produced in the manufacture of their own dense skin foam.
66. Polyurethane microporous elastomer characteristics and uses
A: Features: Polyurethane elastomer is a kind of block polymer, which is composed of soft long chain of oligomer polyols, soft segment composed of diisocyanate and chain extender, hard segments and soft segments are alternately arranged to form repeat In addition to containing urethane groups, polyurethanes can form hydrogen bonds in and between molecules, and soft and hard segments can form micro-phase regions and produce microscopic phase separation.
67. What are the main performance characteristics of polyurethane elastomer
A: Features: 1, high strength and flexibility, can be in a wide range of hardness (Shore A10 ~ Shore D75) to maintain high flexibility; generally without the need for plasticizers to achieve the desired low hardness, So no plasticizer migration problems; 2, under the same hardness, higher than other elastomers bearing capacity; 3, excellent wear resistance, the wear resistance of natural rubber is 2 to 10 times; 4, resistance Oil and chemical resistance; aromatic polyurethane radiation resistance; excellent oxygen and ozone resistance; 5, high impact resistance, fatigue resistance and good shock resistance, suitable for high frequency flexion applications; 6, low temperature Good flexibility; 7, ordinary polyurethane can not be used above 100 ℃, but the use of special formula can withstand 140 ℃ high temperature; 8, the molding and processing costs are relatively low.
68. Polyurethane elastomers are classified according to polyols, isocyanates, manufacturing processes, and the like
A: 1. According to oligomer polyol raw material points, polyurethane elastomer can be divided into polyester, polyether, polyolefin type, polycarbonate type, polyether type according to the specific species can be divided polytetrahydrofuran type , Polyoxypropylene type, etc .; 2. According to the different diisocyanates, aliphatic and aromatic elastomers can be divided into TDI type, MDI type, IPDI type, NDI type; from the manufacturing process, the traditional On the polyurethane elastomer is divided into casting (CPU), thermoplastic (TPU), mixing type (MPU) three categories.
69 molecular structure from the impact of polyurethane elastomer performance factors?
A: From the molecular structure point of view, polyurethane elastomer is a block polymer, generally composed of soft long chain of oligomers polyol soft segment, diisocyanate and chain extender to form a hard segment, alternating hard and soft segments In addition to containing urethane groups, the formation of hydrogen bonds within and between molecules of polyurethane, soft and hard segments can form micro-phase region and produce micro-phase separation of these structural features makes the polyurethane elastomer with Excellent wear resistance and toughness, known as 'wear-resistant rubber'.
70. General polyester and polytetrahydrofuran ether elastomer performance differences
A: Polyester molecules contain more polar ester groups (-COO-), can form a strong intramolecular hydrogen bond, which polyester polyurethane has high strength, wear resistance and oil resistance.
Elastomers made from polyether polyols have good hydrolytic stability, weatherability, low temperature flexibility and resistance to mold and other properties.