I. Definition
1, hydroxyl value: 1 gram of polymer polyol contains the amount of hydroxyl (-OH) equivalent to the number of milligrams of KOH, unit mgKOH/g.
2、Equivalent amount: Equivalent amount = 56100/hydroxyl value
3、Isocyanate content.
4、Isocyanate index: It indicates the degree of excess of isocyanate in polyurethane formulation, usually expressed by the letter R.
5、Chain extender: It is a low molecular weight alcohol and amine compound that can make the molecular chain extend, expand or form a spatial network crosslink.
6、Hard segment: The chain segment formed by the reaction of isocyanate, chain extender and cross-linker on the main chain of polyurethane molecule, these groups have higher internal aggregation energy, larger space volume and higher rigidity.
7、Soft segment: Carbon-carbon main chain polymer polyol with better flexibility, which is a flexible segment in the main chain of polyurethane.
8、Foaming index: the number of parts of water equivalent to that used in 100 parts of polyether is defined as the foaming index (IF).
9、One-step method: It refers to the method of mixing oligomeric polyol, diisocyanate, chain extender and catalyst at the same time and then injecting them directly into the mold and curing them at a certain temperature.
10、Prepolymer method: Firstly, the oligomeric polyol is prepolymerized with diisocyanate to produce polyurethane prepolymer with end NCO group, and then the prepolymer is reacted with chain extender when casting to prepare polyurethane elastomer, which is called prepolymer method.
11、Semi-prepolymer method: The difference between semi-prepolymer method and prepolymer method is that part of polyester polyol or polyether polyol is added to the prepolymer in the form of mixture with chain extender and catalyst.
12, reaction injection molding: also known as reaction injection molding RIM (Reaction Injection Moulding), is measured by the molecular weight of the zwitterionic material in liquid form, instantaneous mixing while injected into the mold, and rapid reaction in the mold cavity, the material molecular weight increased rapidly to generate a new polymer containing a new structure of characteristic groups at a very fast rate of the process.
13、Foaming index：That is, the number of parts of water used in 100 parts of polyether is defined as the foaming index (IF).
14、Foaming reaction: Generally, it refers to the reaction of water and isocyanate to generate substituted urea and release CO2.
15, gel reaction: generally refers to the formation of carbamate reaction.
16, gel time: under certain conditions, the time required to form a gel of liquid material.
17、Milk time: When the I zone is about to end, the milky phenomenon appears in the liquid-phase polyurethane mixture. The time in the generation of polyurethane foam is called the cream time (cream time).
18、Chain expansion factor: It is the ratio of the amount of amino and hydroxyl groups (unit: mo1) in the chain expander component (including mixed chain expander) to the amount of NCO in the prepolymer, which is the ratio of the molarity (equivalent number) of active hydrogen groups to NCO.
19、Low unsaturation polyether: mainly developed for PTMG, the price of PPG, unsaturation reduced to 0.05mol/kg, close to the performance of PTMG, using DMC catalyst, the main varieties of Bayer Acclaim series.
20、Urethane grade solvents.
21, physical blowing agent: physical blowing agent is the foam fine pore is formed by a change in the physical form of a substance, that is, through the expansion of compressed gas, the volatilization of liquid or dissolution of solid
22, chemical blowing agent: chemical blowing agent is those heated decomposition can release carbon dioxide and nitrogen and other gases, and the formation of fine pores in the polymer composition of the compound
23, physical cross-linking: in the polymer soft chain has part of the hard chain, hard chain in the softening point or melting point below the temperature with the same physical properties of chemical cross-linking of vulcanized rubber phenomenon.
24、Chemical cross-linking: refers to the process of forming a net or body-shaped structure polymer by chemical bonding between macromolecular chains under the action of light, heat, high-energy radiation, mechanical force, ultrasonic waves and cross-linking agents.
II. Short answer
1、Which types of isocyanates are commonly used from the structural point of view?
A: Aliphatic, alicyclic, aromatic
2、Which kinds of isocyanates are commonly used? Write the structural formula
A: Toluene diisocyanate (TDI), diphenylmethane-4,4′-diisocyanate (MDI), polyphenylmethane polyisocyanate (PAPI), liquefied MDI, hexamethylene diisocyanate (HDI), hydrogenated TDI
3、What do TDI-100 and TDI-80 mean?
A: TDI-100 means it is all composed of 2,4 structured toluene diisocyanate; TDI-80 means it is a mixture of 80% 2,4 structured toluene diisocyanate and 20% 2,6 structured.
4、What are the characteristics of each of TDI and MDI in the synthesis of polyurethane materials?
A: For the reactivity of 2,4-TDI and 2,6-TDI, the reactivity of 2,4-TDI is several times higher than that of 2,6-TDI because, the 4-position NCO in 2,4-TDI is far away from the 2-position NCO and methyl group, and there is almost no site resistance, while the 2,6-TDI NCO is subjected to a larger site-blocking effect by the neighboring methyl group, and the reactivity is affected.
The two NCO groups of MDI are far away from each other and there is no substituent around, so the activity of both NCOs is larger. Even if one of the NCOs participates in the reaction, the activity of the remaining NCO decreases, but the overall activity is still larger.
5、Which of HDI, IPDI, MDI, TDI and NDI is better in yellowing resistance?
A: HDI (non-yellowing aliphatic diisocyanate), IPDI (polyurethane resin with excellent optical stability and chemical resistance, generally used in the manufacture of high-grade non-discolored polyurethane resin)
6、The purpose of MDI modification and the common modification methods.
A: Liquefied MDI: purpose of modification: liquefied pure MDI is the MDI modified by liquefaction, which overcomes some defects of pure MDI (solid at room temperature, melting when used, and affecting performance by repeated heating), and also provides the basis for the improvement and enhancement of the performance of MDI-based polyurethane materials with a wide range of modification. Methods: ① Urethane modified liquefied MDI, ② Carbodiimide and uretonimine type modified liquefied MDI, ③ Doped liquefied MDI
Hydrogenated TDI, scientifically known as methyl ring has been based diisocyanate, aliphatic isocyanate, which is stable to light and does not produce yellowing chromogenic group
7、Which types of polymer polyols are commonly used?
A: polyester polyol, polyether polyol
8, polyester polyol industrial production methods are mainly several?
A: A, vacuum melting method B, carrier gas melting method C, azeotropic distillation method
9, polyester, polyether polyol molecules on the main chain of what special structure?
A: polyester polyol: in the main chain of the molecule contains ester groups, in the end groups with hydroxyl (-OH) of large molecules of alcohol compounds. Polyether polyols: polymers or zwitterions that contain ether bonds (-O-), end groups with (-OH) or amine groups (-NH2) in the main chain structure of the molecule.
10、How many types of polyether polyols are there according to their characteristics?
A: Highly reactive polyether polyol, graft polyether polyol, flame retardant polyether polyol, heterocyclic modified polyether polyol, polytetrahydrofuran polyol
11、How many kinds of common polyethers are there according to the starting agent?
A: Poly(propylene oxide diol), poly(propylene oxide triol), hard foam polyether polyol, low unsaturated polyether polyol
12、Which types of polyurethane catalysts are commonly used? Which common varieties are included in each?
A: Tertiary amine catalysts, commonly used varieties include: triethylenediamine, dimethylethanolamine, N-methylmorpholine, N,N-dimethylcyclohexylamine
Metal alkyl compounds, commonly used varieties include: organotin catalysts, which can be divided into stannous octanoate, stannous oleate, dibutyltin dilaurate
13、What are the commonly used polyurethane chain extenders or cross-linking agents?
A: Polyols (1,4-butanediol), alicyclic alcohols, aromatic alcohols, diamines, alcohols and amines (ethanolamine, diethanolamine)
14、The reaction mechanism of isocyanate
A: The reaction between isocyanate and active hydrogen compounds is caused by the nucleophilic center of the active hydrogen compound molecule attacking the carbon atom of the NCO group. The reaction mechanism is as follows.
15. How does the structure of isocyanate affect the reactivity of the NCO group?
A. Electronegativity of R group: If R group is electron-absorbing group, the electron cloud density of C atom in -NCO group is more reduced and more easily attacked by nucleophilic reagents, i.e. more easily nucleophilic reaction with alcohols, amines and other compounds. If R is an electron donor group, through electron cloud transfer, it will increase the electron cloud density of C atoms in the -NCO group, making it less susceptible to attack by nucleophilic reagents, and its ability to react with compounds containing active hydrogen decreases. b. Induced effect: Since aromatic diisocyanates contain two NCO groups, when an -NCO gene C. Spatial site blocking effect: In aromatic diisocyanate molecules, if two -NCO groups are on an aromatic ring at the same time, then one of the NCO groups has an effect on the reactivity of the aromatic ring. Then one of the NCO group on the other NCO group reaction activity is often more significant. However, when the two NCO groups are in the same molecule on different aromatic rings, or they are separated by hydrocarbon chains or aromatic rings, so that the interaction between them is not much, and with the increase in the length of the chain hydrocarbon or aromatic ring number increases and decreases.
16、Reactive hydrogen compound species and NCO reactivity
A: Aliphatic NH2＞Aromatic NH2＞Po drunken OH＞Water＞Secondary OH＞Phenol OH＞Carboxyl＞Substituted urea＞Amide＞Carbamate. (If the electron cloud density of the nucleophilic center is greater, the stronger its electronegativity, the higher its reaction activity with isocyanate, and the faster the reaction speed; vice versa, the activity is low.)
17、Common reactions of isocyanate and active hydrogen compounds
A: React with alcohol to produce carbamate.
Reaction with water:One of the basic reactions for the preparation of polyurethane foam. The reaction between them firstly produces unstable carbamic acid, then decomposes into CO2 and amine. If there is an excess of isocyanate, the generated amine will react with isocyanate to form urea.
Amine compounds can only react with isocyanate at a moderate rate at higher temperatures (e.g. >100°C) to form acylureas.
Amines react with isocyanates to produce substituted urea structures.
18、The effect of hydroxyl compounds on their reaction activity with isocyanate
A: The reactivity of active hydrogen compounds (ROH or RNH2) is related to the nature of R. When R is an electron-absorbing group (low electronegativity), it is difficult to transfer out the hydrogen atom, and the reaction of active hydrogen compounds with NCO is more difficult; if R is an electron-donating substituent, it can improve the reactivity of active hydrogen compounds with NCO.
19、What is the use of the reaction of isocyanate with water
A: It is one of the basic reactions for the preparation of polyurethane foam. The reaction between them firstly generates unstable carbamic acid and then decomposes into CO2 and amine. If there is an excess of isocyanate, the generated amine will react with isocyanate to form urea.
20、When preparing polyurethane elastomer, the water content of polymer polyol should be strictly controlled
A: For elastomers, coatings and fibers require that there should be no air bubbles, so the water content in raw materials must be strictly controlled, usually requiring less than 0.05%.
21、The reaction of isocyanate with carbamate and urea group
22、Difference of catalytic effect of amine and tin catalysts on isocyanate reaction
A: The catalytic efficiency of tertiary amine catalyst for the reaction of isocyanate with water is large, while the catalytic efficiency of tin catalyst for the reaction of isocyanate with hydroxyl group is large.
23、Why can polyurethane resin be regarded as a block polymer and what are the characteristics of chain segment structure?
A: The chain segment of polyurethane resin is composed of hard segment and soft segment. Hard segment refers to the chain segment formed by the reaction of isocyanate, chain extender and cross-linker on the main chain of polyurethane molecule, and these groups have higher internal aggregation energy, larger space volume and higher rigidity. And the soft segment refers to the carbon-carbon main chain polymer polyol, which is more flexible and is a flexible segment in the main chain of polyurethane.
24、What are the factors affecting the performance of polyurethane materials?
A: cohesion energy of groups, hydrogen bonding, crystallinity, cross-linking, molecular weight, hard segment, soft segment
25、Which raw materials are the soft and hard segments in the main chain of polyurethane material?
A: Soft segment is composed of oligomeric polyol (polyester, polyether glycol, etc.) and hard segment is composed of polyisocyanate or its chain extender with small molecules.
26、How do the soft and hard segments affect the performance of polyurethane materials?
A: Soft segment: (1) Molecular weight of soft segment: assuming the same molecular weight of polyurethane, if the soft segment is polyester, the strength of polyurethane increases with the increase of molecular weight of polyester diol; if the soft segment is polyether, the strength of polyurethane decreases with the increase of molecular weight of polyether diol, but the elongation increases. (2) Crystallinity of soft segment: It has a greater contribution to the crystallinity of linear polyurethane chain segment. In general, crystallinity is beneficial to improve the performance of polyurethane products, but sometimes crystallization reduces the low temperature flexibility of the material and crystalline polymers are often opaque.
Hard segments: Hard chain segments usually affect the softening melt temperature and high temperature properties of the polymer. Polyurethanes prepared from aromatic isocyanates contain rigid aromatic rings in the hard segment, which increases the cohesive strength of the hard segment and generally makes the material stronger than aliphatic isocyanate polyurethanes, but they are less resistant to UV degradation and are prone to yellowing. Aliphatic polyurethane does not yellow.
27、Urethane foam classification
A: (1) Rigid and soft foam, (2) high-density and low-density foam, (3) polyester-type and polyether-type foam, (4) TDI-type and MDI-type foam, (5) polyurethane foam and polyisocyanurate foam, (6) one-step and pre-polymerization production, (7) continuous and intermittent production, (8) block foam and molded foam
28、The basic reaction of foam preparation
A: It refers to the reaction of -NCO with -OH, -NH2, H2O, and the reaction with polyol, and the “gel reaction” in the foaming process generally refers to the formation of carbamate. Because the foam is made of polyfunctional raw materials, a cross-linked network is obtained, which makes the foaming system gel rapidly. The reaction formula of the group is as follows.
In a foaming system where water is present, a foaming reaction is generated. The so-called “foaming reaction” generally refers to the reaction between water and isocyanate to produce substituted urea, and the release of CO2.
29、The role of foam stabilizer in the preparation of polyurethane foam
A: It has emulsifying effect, so that the mutual solubility between the components of the foam material is enhanced; after adding silicone surfactant, because it greatly reduces the surface tension of the liquid γ, the free energy required for gas dispersion is reduced, so that the air dispersed in the raw material is easier to nucleate in the mixing process, which helps the generation of small bubbles and improves the stability of the foam.
30、The stabilization mechanism of foam
A: The addition of appropriate surfactants facilitates the generation of fine bubble dispersions.
