70 basic polyurethane concepts to get a thorough understanding of it!

1, hydroxy value:
1 g polymer polyol contains hydroxyl (-OH) equivalent to the number of milligrams of KOH, units mgKOH/g.
2, equivalent:
the average molecular weight of a group of officials.
3, isocyanate root content:
molecule isocyanate root content
4, isocyanate index:
indicates the degree of isocyanate overdose in polyurethane formula, usually with the letter R for
Ced china
.
5, chain expansion agent:
refers to the molecular chain can extend, expand or form a spatial mesh crosslink of low molecular weight alcohols, amine compounds.
6, hard segment:
polyurethane molecule main chain by isocyanate, chain expansion agent, crosslinker reaction formed by the chain segment, these groups of poly energy is larger, space volume is larger, rigid larger.
7, soft
: carbon carbon main chain polymer polyol, smoothness is better, in the main polyurethane chain for flexible chain segment.
8, one-step method
: refers to the low-polyol, isocyanate, chain expansion agent and catalyst, etc. mixed at the same time directly into the mold, at a certain temperature curing molding method.
9, pre-polyurethane method:
first of all, low-polyphur polyol and isocyanate pre-polyurethane pre-polypulestion reaction, the generation of end NCO-based polyurethane pre-polypulgate, pouring will be pre-polyp and chaining agent reaction, the preparation of polyurethane elastomer method, called pre-polyurethane method.
10, semi-prejudgment method: the difference between
semi-prejudgment method and pre-polyurethane method is to add some polyester polyols or polyether polyols with chaining agents, catalysts, etc. in the form of a mixture to the pre-polyurethane.
11, reaction injection molding:
, also known as reaction injection molding RIM (React Injection Moulding), is a process by which small molecular weight polymers are measured in liquid form, instantaneously mixed and injected into the mold, while reacting quickly in the mold cavity, the molecular weight of the material increases rapidly, generating a new polymer with new properties of the base structure at an extremely fast rate.
12, foaming index:
that is, the equivalent of 100 polyethers used in the number of parts of water defined as foam index (IF).
13, foaming reaction:
generally refers to the water and isocyanate reaction to produce a replacement for radon, and release CO2 reaction.
14, gel reaction:
generally refers to the formation of amino acid reaction.
15, Gel Time:
under certain conditions, liquid materials need to form gel time.
16, milk white time:
in area I near the end, in the liquid polyurethane mixture material appears milk white phenomenon. This time is called cream time in polyurethane foam production.
17, chain expansion coefficient:
refers to the ratio of amino, hydroxyl (unit: mo1) and NCO in the chain expander component (including mixed chain agent), i.e. the ratio of the active hydrogen group to the number of moles (equivalents) of the NCO.
18, low unsaturated polyether:
is mainly for PTMG development, PPG price, unsaturated to 0.05mol/kg, close to the performance of PTMG, using DMC catalyst, the main variety Bayer Acclaim series products.
19, urethane-grade solvents:
production of polyurethane selected solvents to consider the solubility, volatility speed, but the production of polyurethane solvents, should focus on the polyurethane weight NC0 base. It is not able to select solvents such as alcohols and ether alcohols that react with the NCO base. Solvents can not contain water, alcohol and other impurities, can not contain alkalis, these will make polyurethane desury.
solvents do not allow moisture or free acids and alcohols, which react with NCO-based reactions. The urethane solvents used in polyurethanes should be "urethane-grade solvents" with high purity. The solvent reacts with excess isocyanate, and then the amount of unresponsive isocyanate is determined with butamine to check whether it is common. The principle is that the consumption of isocyanate is not applicable, because it indicates that the ester contains water, alcohol, acid will consume isocyanate total value, if the consumption of leqNCO base needs solvent grams, the value of large stability is good.
used as a polyurethane solvent if the isocyanate equivalent is less than 2500.
the polarity of the solvent has a great effect on the reaction of the resin. The greater the polarity, the slower the reaction, such as toluene and methyl ethyl ketone difference of 24 times, the solvent molecule polarity is large, can form a hydrogen bond with the hydroxyl alcohol and make the reaction slow.
the use of aromatic solvents for polychloride solvents, they react faster than esters, ketones, such as xylene. In the construction of double new polyurethane, the use of ester and ketone solvents can extend its life. In the production of coatings, the "urethane-grade solvent" mentioned earlier in the selection is beneficial to the storage of stable parts.
ester solvent solubility is strong, the volatility speed is moderate, low toxicity and use more, cyclosterone is also used more, hydrocarbon solvent solid solubility capacity is low, less alone use, more with other solvents.
20, physical foaming agent
: physical foaming agent is the foam fine hole is through the physical form of a substance changes, that is, through the expansion of compressed gas, liquid volatilization or solid dissolution.
21, chemical foaming agent:
chemical foaming agent is those after heating and decomposition can release carbon dioxide and nitrogen and other gases, and in the polymer composition of the formation of fine holes in the compound compounds.
22, physical crosslinking:
in the high-polymer soft chain has a part of the hard chain, the hard chain in the softening point or melting point below the temperature has the same physical properties as chemical cross-linking of vulcanized rubber phenomenon.
23, chemical crosslinking:
refers to the process of forming a mesh or body structure polymer between large molecular chains through chemical bonds under the action of light, heat, high-energy radiation, mechanical force, ultrasonic waves and crosslinkers.
24, Foaming Index:
defines the number of parts equivalent to water used in 100 polyethers as the foaming index (IF).
25. What are the types of isocyanates commonly used in terms of structure?
: Fats: HDI, Lipids: IPDI, HTDI, HMDI, Aromatics: TDI, MDI, PAPI, PPDI, NDI.
26. What are the commonly used isocyanates? Write out structural
: toluene isocyanate (TDI), dibenzene methane-4,4'-diocyanate (MDI), polyphenyl methane polyseocyanate (PAPI), liquefied MDI, hemethyl dicycyanate (HDI).
27.TDI-100 and TDI-80 meaning?
: TDI-100 refers to all by 2,4 structures of toluene diocyanate; TDI-80 refers to a mixture of 80% 2,4 structures of toluene diocyanate and 20% of 2,6 structures.
28.TDI and MDI have their own characteristics in the synthesis of polyurethane materials?
: Reaction activity for 2, 4-TDI and 2,6-TDI. The reaction activity of 2,4-TDI is several times higher than that of 2,6-TDI, because 4 NCO in 2,4-TDI is far away from 2-bit NCO and methyl, with virtually no bit resistance, while NCO in 2,6-TDI is subject to a greater bit resistance effect of neighboring methyl, and reaction activity is affected.
MDI's two NCO groups are far apart, and there is no replacement base around, so the activity of these two ICOs are larger, even if one of the NCO participated in the reaction, so that the remaining NCO activity decreased, the overall activity is still larger, so the reaction activity of MDI polyurethane pre-polymer is larger than TDI pre-polymer.
29.HDI, IPDI, MDI, TDI, NDI in the yellowing resistance which is better?
: HDI (belongs to the same yellow fat family diocyanate), IPDI (made of polyurethane resin with excellent optical stability and chemical resistance, generally used in the manufacture of high-grade invarant polyurethane resin).
30.MDI modified purpose and commonly used modified method
A: liquefatured MDI: modified purpose: liquefaciated pure MDI is liquefied modified MDI, it overcomes some defects of pure MDI (solids at room temperature, use to melt, multiple heating affect performance), but also for MDI urethane material performance improvement and improvement provides a large-scale basis for change.
:
(1) urethane modified liquefied MDI.
(2) carbodiimide and uretonimine modified liquefied MDI.
31. What are the commonly used types of polymer polyols?
: Polyester polyols, polyether polyols
32. Polyester polyol industrial production methods are mainly several?
: A, vacuum melting method B, gas fusion method C, co-boiling distillation method
33. Polyester, polyether polyol molecular main chain what are the special structures?
: Polyester polyols: large molecular alcohol compounds containing ester-based, hydroxyl (-OH) on the end-base. Polyether polyols: Polymers or polymers containing ether bonds (-O-), end-based polymers with (-OH) or amine-based (-NH2) on the structure of the molecular main chain.
34. According to the characteristics of polyether polyols divided into several categories?
answer: highly active polyether polyol, branched polyether polyol, flame retardant polyether polyol, hemeric modified polyether polyol, polytide furan polyol.
35. How many common polyethers are divided according to the starting agent?
: polyoxidizing propylene glycol, polypropylene glycol, hard bubble polyether polyol, low unsaturated polyether polyol.
is the difference between 36.end hydroxyl ether and end amine-based polyether?
end amine-based polyether is the end hydroxyl is replaced by amine-based polypropylene ether.
37. What are the commonly used polyurethane catalysts? Which common varieties are included?
: Schoamine catalysts, commonly used varieties are: triethylethylene, methamphetamine, N-methyl morphine, N, N-methyl cycloamine
metal alkyl compounds, commonly used varieties are: organotin catalysts, can be divided into octalic acid tin, lysine lysine, titrate february laurel esters.
38. What are the common polyurethane chaining agents or crosslinkers?
: Polyols (1,4-butyl glycol), lipocycline, aromatics, damines, alcoholamines (ethanolamine, diethanolamines)
39. Isocyanate reaction
A: isocyanate and live hydrogen reaction, is caused by the active hydrogen molecules in the pro-nuclear center attack NCO-based carbon atoms. The reaction structure is as follows:
40. How does the isocyanate structure affect the reaction activity of the NCO group?
: A.R.-based electron negative: If the R-base is electron-absorbent, - NCO Group C atomic electron cloud density is more reduced, more susceptible to pro-nuclear reagents, that is, more easily and alcohol, amines and other compounds for pro-nuclear reaction. If R is an electron base, transmitted through an electron cloud, it will increase the density of the electron cloud of the C atom in the -NCO group, making it less susculent to pro-nuclear reagents, and its ability to react with active hydrogen compounds decreases. B. Induction effect: Because aromatic isocyanate contains two NCO groups, when the first -NCO gene participates in the reaction, due to the conjugate effect of the aromatic ring, the non-reaction-NCO group will act as an electron-absorbing base, so that the first NCO group reaction activity is enhanced, this effect is the induction effect. C. Spatial bit resistance effect: In aromatic isocyanate molecules, if two -NCO groups are in one aromatic ring at the same time, the effect of one NCO base on the reaction activity of the other NCO base is often more significant. However, when two NCO-based systems are located on different aroma rings in the same molecule, or they are separated by hydrocarbon chains or aromatic rings, the interaction between them is less and decreases with the increase in the length of the chain hydrocarbons or the number of aromatic rings.
41. Lively hydrogen compound type and NCO reaction activity
A: fat family NH2> Aromatic NH2> Bo drunk OH> water> Zhong OH>phenol OH>phenol OH> replacing ceretin >amide> amethane. (If the higher the density of the electron cloud in the pro-nuclear center, the stronger its electron negative, the higher its reaction activity with isocyanate, the faster the reaction speed;
42. Effects of hydroxyl compounds on their reaction activity with isocyanates
A: The reactivity of live hydrogen compounds (ROH or RNH2) is related to the nature of R, when R is electron-absorbent (low electron negative), hydrogen atom transfer is difficult, active hydrogen compounds and NCO reaction is more difficult;
43. What is the use of isocyanate and water reaction
Answer: is one of the basic reactions to the preparation of polyurethane foam. The reaction between them first produces unstable amino acid, which is then broken down into CO2 and amines, and if isocyanate is excessive, the resulting amine reacts with isocyanate to produce pyrethroids.
44. When preparing the polyurethane elastic system, the water content of polymer polyols should be strictly controlled
A: for elastomers, coatings, fiber requirements can not have bubbles, so the water content of raw materials must be strictly controlled, usually less than 0.05%.
45. The catalytic effect of amine and tin catalysts on isocyanate reactions is different
A: the catalytic efficiency of isocyanate and water reaction of isocyanide catalysts is large, while the catalytic efficiency of isocyanate and hydroxyl reactions of tin catalysts is large.
46. Why can polyurethane resin be regarded as a segment polymer, what are the characteristics of the chain segment structure?
: Because the chain segment of polyurethane resin is composed of hard segment and soft segment, hard segment refers to the main polyurethane molecule