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1. Hydroxyl value: The amount of hydroxyl group (-OH) contained in 1 g of the polymer polyol corresponds to the number of milligrams of KOH in units of mgKOH/g.

2. Equivalent: the average molecular weight of a functional group.

3, isocyanate content: the content of isocyanate in the molecule

4. Isocyanate index: indicates the degree of excess of isocyanate in the polyurethane formulation, usually indicated by the letter R.

5. Chain extender: refers to low molecular weight alcohols and amine compounds which can extend, expand or form spatial network crosslinks.

6. Hard segment: a segment formed by the reaction of isocyanate, chain extender and crosslinker on the main chain of polyurethane. These groups have larger cohesive energy, larger space and greater rigidity.

7. Soft segment: Carbon-carbon backbone polymer polyol, which has good flexibility and is a flexible segment in the polyurethane main chain.

8. One-step method: refers to a method in which an oligomer polyol, a diisocyanate, a chain extender, and a catalyst are simultaneously mixed and directly injected into a mold to be solidified at a certain temperature.

9. Prepolymer method: Firstly, the oligomer polyol and the diisocyanate are prepolymerized to form a NCO-based polyurethane prepolymer, and the prepolymer is reacted with a chain extender to prepare a polyurethane elastomer. The method is called the prepolymer method.

10. Semi-prepolymer method: The difference between the semi-prepolymer method and the prepolymer method is that a part of the polyester polyol or the polyether polyol is added to the prepolymer as a mixture with a chain extender, a catalyst or the like.

11. Reaction injection molding: also known as reaction injection molding RIM (Reaction Injection Moulding), which is measured by liquid molecular form of oligomers with a small molecular weight, which is injected into the mold while mixing instantaneously, and reacts rapidly in the cavity. The process of rapidly increasing the molecular weight to produce a completely new polymer containing a new characteristic group structure at an extremely fast rate.

12. Foaming index: The fraction of water equivalent to 100 parts of polyether is defined as the foaming index (IF).

13. Foaming reaction: Generally speaking, there is a reaction in which water reacts with isocyanate to form a substituted urea and emits CO2.

14. Gel reaction: generally refers to the formation reaction of carbamate.

15. Gel time: The time required for a liquid substance to form a gel under certain conditions.

16. Opal time: At the end of the I zone, the milky white phenomenon appears in the liquid polyurethane mixture. This time is referred to as the cream time in the formation of the polyurethane foam.

17. Chain extension coefficient: refers to the ratio of the amount of amino group and hydroxyl group (unit: mo1) in the chain extender component (including mixed chain extender) to the amount of NCO in the prepolymer, that is, active hydrogen group and NCO. The number of moles (equivalents) ratio.

18, low unsaturation polyether: mainly for PTMG development, PPG price, unsaturation reduced to 0.05mol / kg, close to the performance of PTMG, using DMC catalyst, the main variety Bayer Acclaim series products.

19. Urethane ester solvent: The solvent used for the production of polyurethane should consider the solvent and volatilization speed. However, the solvent used in the production of polyurethane should focus on the weight of the NC0 base in the polyurethane. A solvent such as an alcohol or an ether oxime which reacts with the NCO group cannot be used. The solvent can not contain impurities such as water and alcohol, and cannot contain alkali substances, which will deteriorate the polyurethane.

Ester solvents are not allowed to contain moisture, nor contain free acids and alcohols, which react with NCO groups. For the ester solvent used in polyurethane, a "urethane ester solvent" with a high purity should be used. That is, the solvent was reacted with an excess of isocyanate, and the amount of unreacted isocyanate was measured by dibutylamine to examine whether it was used in combination. The principle is that the consumption of isocyanate is not suitable, because it indicates that the total value of the isocyanate is consumed by the water, alcohol and acid in the ester. If the number of grams of solvent required to consume the leqNCO group is expressed, the value is larger and the stability is better. .

An isocyanate equivalent of less than 2,500 or less is not used as a urethane solvent.

The polarity of the solvent has a great influence on the reaction of the resulting resin. The higher the polarity, the slower the reaction, such as the difference between toluene and methyl ethyl ketone by 24 times. The solvent molecule has a large polarity and can form a hydrogen bond with the hydroxyl group of the alcohol to make the reaction slow.

The polychlorinated solvent is preferably an aromatic hydrocarbon solvent, and the reaction speed thereof is faster than that of an ester or a ketone, such as xylene. In the construction of double-bond polyurethane, ester and ketone solvents can be used to extend the service life. In the production of coatings, the "urethane-grade solvent" mentioned above is advantageous for storage stabilizers.

The ester solvent has strong dissolving power, moderate volatilization speed, low toxicity and more use, and cyclohexanone is also used frequently. The hydrocarbon solvent has low solid solubility, and is used less separately, and is used in combination with other solvents.

20. Physical foaming agent: The physical foaming agent is a foam pore which is formed by the change of the physical form of a certain substance, that is, by the expansion of a compressed gas, the volatilization of a liquid or the dissolution of a solid.

21. Chemical foaming agent: A chemical foaming agent is a compound which releases a gas such as carbon dioxide and nitrogen after being decomposed by heating, and forms pores in the polymer composition.

22. Physical crosslinking: There are some hard chains in the soft chain of the polymer, and the hard chain has the same physical properties as the vulcanized rubber after chemical crosslinking at a temperature below the softening point or below the melting point.

23. Chemical cross-linking: refers to the process of forming macro-molecular chains by chemical bonds under the action of light, heat, high-energy radiation, mechanical force, ultrasonic waves and cross-linking agents to form a network of mesh or body structures.

24. Foaming Index: The fraction of water equivalent to 100 parts of polyether is defined as the foaming index (IF).

25. What types of commonly used isocyanates are structurally considered?

A: Aliphatic: HDI, alicyclic: IPDI, HTDI, HMDI, aromatic: TDI, MDI, PAPI, PPDI, NDI.

26. What kinds of commonly used isocyanates? Write the structure

A: Toluene diisocyanate (TDI), diphenylmethane-4,4'-diisocyanate (MDI), polyphenylmethane polyisocyanate (PAPI), liquefied MDI, hexamethylene diisocyanate (HDI).

27. What does TDI-100 and TDI-80 mean?

A: TDI-100 means all consisting of toluene diisocyanate of 2,4 structure; TDI-80 means a mixture of 80% of 2,4 structure toluene diisocyanate and 20% of 2,6 structure.

28. What are the characteristics of TDI and MDI in the synthesis of polyurethane materials?

A: Reactivity for 2,4-TDI and 2,6-TDI. The reactivity of 2,4-TDI is several times higher than that of 2,6-TDI. This is because the 4 NCO in 2,4-TDI is far from the 2 NCO and methyl group, almost no steric hindrance, and 2,6 The NCO of -TDI is more affected by the steric hindrance of the ortho-methyl group, and the reactivity is affected.

The two NCO groups of MDI are far apart and have no substituents around them, so the activity of these two NCOs is large, even if one of the NCOs participates in the reaction, the remaining NCO activity is reduced, in general The activity is still large, so the reactivity of the MDI type polyurethane prepolymer is larger than that of the TDI prepolymer.

29. Which kinds of yellowing resistance are better in HDI, IPDI, MDI, TDI, and NDI?

A: HDI (which is a non-yellowing aliphatic diisocyanate), IPDI (made of polyurethane resin with excellent optical stability and chemical resistance, generally used to make high-grade non-discoloring polyurethane resin).

30. The purpose of MDI modification and commonly used modification methods,

Answer: Liquefied MDI: Modification purpose: liquefied pure MDI is liquefied MDI, which overcomes some defects of pure MDI (solid at normal temperature, used to melt, multiple heating affects performance), also MDI-based polyurethane material Improvements and improvements in performance provide the basis for a wide range of modifications.

method:

1 urethane modified liquefied MDI.

2 carbodiimide and uretonimine type modified liquefied MDI.

31. What types of commonly used polymer polyols?

A: Polyester polyol, polyether polyol

32. What are the main industrial production methods for polyester polyols?

Answer: A, vacuum melting method B, carrier gas melting method C, azeotropic distillation method

33. What are the special structures on the molecular backbone of polyester and polyether polyols?

A: Polyester polyol: a macromolecular alcohol compound having an ester group in a molecular main chain and a hydroxyl group (-OH) at a terminal group. Polyether polyol: A polymer or oligomer having an ether bond (-O-) on a molecular backbone structure and an (-OH) or amine group (-NH2) at the end group.

34. According to the characteristics of polyether polyols in several categories?

A: Highly active polyether polyol, grafted polyether polyol, flame retardant polyether polyol, heterocyclic modified polyether polyol, polytetrahydrofuran polyol.

35. According to the starting agent, there are several kinds of ordinary polyethers?

A: Polyoxypropylene diol, polyoxypropylene triol, hard foam polyether polyol, low unsaturation polyether polyol.

36. What is the difference between a hydroxyl terminated polyether and a terminal amino polyether?

The terminal aminopolyether is a polyoxypropylene ether in which a terminal hydroxyl group is substituted with an amine group.

37. What kinds of commonly used polyurethane catalysts, including which common varieties?

Answer: Tertiary amine catalysts, commonly used varieties are: triethylenediamine, dimethylethanolamine, N-methylmorpholine, N,N-dimethylcyclohexylamine

Metal alkyl compounds, commonly used varieties are: organotin catalysts, which can be divided into stannous octoate, stannous oleate, dibutyltin dilaurate.

38. What are the commonly used polyurethane chain extenders or crosslinkers?

A: Polyols (1,4-butanediol), alicyclic alcohols, aromatic alcohols, diamines, alcohol amines (ethanolamine, diethanolamine)

39. Reaction mechanism of isocyanate

A: The reaction of isocyanate with an active hydrogen compound is caused by the attack of the NCO-based carbon atom by the nucleophilic center in the active hydrogen compound molecule. The reaction mechanism is as follows:

40. How does the isocyanate structure affect the reactivity of the NCO group?

Answer: The electronegativity of AR-based: If the R-based group is an electron-withdrawing group, the density of C-electron electrons in the -NCO group is further reduced, and it is more susceptible to attack by nucleophiles, which is easier to carry out with alcohols, amines and other compounds. Nucleophilic reaction. If R is an electron donating group, passing through the electron cloud will increase the electron cloud density of the C atom in the -NCO group, making it less susceptible to attack by nucleophiles, and its ability to react with active hydrogen compounds is reduced. B. Inductive effect: Since the aromatic diisocyanate contains two NCO groups, when the first -NCO gene participates in the reaction, the -NCO group that does not participate in the reaction will function as an electron withdrawing due to the conjugation effect of the aromatic ring. The role of the base is to increase the reactivity of the first NCO group, which is the induction effect. C. steric hindrance effect: In the aromatic diisocyanate molecule, if two -NCO groups are simultaneously on one aromatic ring, the influence of one NCO group on the other NCO group reaction is often significant. . But when the two NCO groups are on different aromatic rings in the same molecule, or they are separated by a hydrocarbon chain or an aromatic ring, the interaction between them is small, and the length of the chain hydrocarbon increases or The number of rings increases as the number increases.

41. Active hydrogen compound species and NCO reactivity

A: Aliphatic NH2>Aromatic NH2>Bo drunk OH>Water>Second OH>Phenol OH>Carboxy>Substituted urea>Amide>Carbamate. (If the electron cloud density of the nucleophilic center is greater, the electronegativity is stronger, the higher the reactivity with isocyanate, the faster the reaction rate; otherwise, the lower the activity.)

42. Effect of hydroxy compounds on its reactivity with isocyanates

Answer: The reactivity of active hydrogen compounds (ROH or RNH2) is related to the nature of R. When R is an electron withdrawing group (low electronegativity), the transfer of hydrogen atoms is difficult, and the reaction of active hydrogen compounds with NCO is difficult; When R is an electron-donating substituent, the reactivity of the active hydrogen compound with NCO can be increased.

43. What is the use of the reaction of isocyanate with water?

A: It is one of the basic reactions in the preparation of polyurethane foam. The reaction between them first generates unstable carbamic acid and then decomposes into CO2 and an amine. If the isocyanate is excessive, the resulting amine will react with the isocyanate to form urea.

44. When preparing polyurethane elastomer, the water content of polymer polyol should be strictly controlled.

Answer: There is no requirement for bubbles in elastomers, coatings and fibers, so the water content in the raw materials must be strictly controlled, usually less than 0.05%.

45. Differences in the catalytic effect of amines and tin catalysts on isocyanate reaction

Answer: The tertiary amine catalyst has a high catalytic efficiency for the reaction of isocyanate with water, and the tin catalyst has a high catalytic efficiency for the reaction of isocyanate with hydroxyl.

46. ​​Why can polyurethane resin be regarded as a block polymer, what are the characteristics of the segment structure?

Answer: Because the segment of polyurethane resin is composed of hard segment and soft segment, the hard segment refers to the segment formed by the reaction of isocyanate, chain extender and crosslinker on the main chain of polyurethane. The cohesive energy of these groups Larger, larger in space and more rigid. The soft segment refers to a carbon-carbon backbone polymer polyol, which has good flexibility and is a flexible segment in the polyurethane backbone.

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. What are the raw materials from the soft and hard segments of the molecular chain of the polyurethane material?

A: The soft segment consists of an oligomer polyol (polyester, polyether diol, etc.) and the hard segment consists of a polyisocyanate or a small molecule chain extender.

49. How do soft and hard segments affect the performance of polyurethane materials?

Answer: Soft segment: (1) Molecular weight of soft segment: Assuming that the polyurethane has the same molecular weight, if the soft segment is polyester, the strength of the polyurethane increases with the molecular weight of the polyester diol; if the soft segment is a polyether, then The strength of the polyurethane decreases as the molecular weight of the polyether diol increases, but the elongation increases. (2) Crystallinity of the soft segment: a large contribution to the crystallinity of the linear polyurethane segment. In general, crystallinity is advantageous for improving the properties of polyurethane articles, but sometimes crystallization reduces the low temperature flexibility of the material, and crystalline polymers are often opaque.

Hard segments: Hard segments generally affect the softening melt temperature and high temperature properties of the polymer. Polyurethane prepared by aromatic isocyanate has a rigid segment containing a rigid aromatic ring, so that the cohesive strength of the hard segment is increased, and the material strength is generally larger than that of the aliphatic isocyanate polyurethane, but the ultraviolet degradation resistance is poor and the yellowing is easy. Aliphatic polyurethanes do not yellow.

50. Polyurethane foam classification

Answer: (1) hard foam and soft foam, (2) high density and low density foam, (3) polyester type, polyether type foam, (4) TDI type, MDI type foam, (5) polyurethane foam and polyisocyanurate foam, (6) one step Production by method and prepolymerization, (7) continuous and batch production, (8) slabstock foam and molded foam.

51. Basic reaction of foam preparation

Answer: Refers to the reaction of -NCO with -OH, -NH2, H2O, and the reaction during the foaming process.