Polyols curatives

Polyurethane systems can be produced to have near-equal or easy mixing component ratios (by either weight or volume). The prepolymers in this type of system are called quasiprepolymers. Quasiprepolymers are normally taken as having at least a fourfold molar excess of isocyanate in the isocyanate side of the system. The other side contains the remainder of the polyol, curative, and any catalysts. 

A one-part, heat-curing polyurethane adhesive has recently been introduced in which the curative is incompatible, and hence nonreactive, with an isocyanate prepolymer. Upon heating, the finely dispersed polyol curative becomes reactive towards the prepolymer and curing takes place. 

Blocked isocyanate, for our purposes, will refer to the reaction product of a diisocyanate or isocyanate-terminated prepolymer in which the isocyanate functionality has been reacted with a blocking agent . Once blocked , the diisocyanate can be added to polyols or certain chain extenders, and these materials will not react at room temperature. The concept is shown in the sixth item of Fig. 1. An adhesive formulated with a blocked isocyanate is basically a two-component adhesive that does not react until heated to the activation temperature. When an adhesive is made with a blocked isocyanate together with hydroxyl-containing curatives, the adhesive has a good long shelf life at room temperature. However, once heated... 

The blocked isocyanate systems (with curative present) are latent cure systems. In order to create a latent curing adhesive, the blocked isocyanate is added to a catalyzed polyol component without a reaction occurring at room temperature. In theory, the blocked adhesive system is relatively stable at room temperature. When this system is heated to the unblocking temperature, the chemical reaction, which... 

A study was done measuring the thermal oxidative stability of polyurethanes made from PPG polyols, varying the isocyanate curative. Oxygen absorption was... 

There are two approaches to forming urethane-acrylic hybrids. First, an acrylate terminated urethane oligomer can be used [147]. Alternatively, polyisocyanate and benzoyl peroxide can be combined in one side of the adhesive, and methacrylate monomers and urethane curatives (especially polyols) in the other [148]. 

Linear polyols of various molecular weights can be used in the chain extension of prepolymers. Their main use is to adjust the hardness of the final compound. They act as a reactive plasticizer, and their functionality and molecular weight must be taken into account in the curative calculations. Either polyether or polyester polyols can be used. The most important point is that they must be dry. 

The high exotherm and the number of feeds have led to the popularity of the quasiprepolymer variation of the one-shot technique. Quasiprepolymers are a version of the standard prepolymer method, where some of the polyol is reacted with an excess of diisocyanate. This is later reacted with the remainder of the polyols, including the chain extender and some catalysts. The advantage of this scheme is that the exotherm is spread between the preparation of the quasiprepolymer and the final cured part. In MD1 systems, BDO is often used as the curative. As the molecular weight of BDOs is low, the amount added is low. By dissolving it in the polyol, a more even mix ratio can be obtained. 

In the preparation of the polyol or "B side," the curative is dissolved in the remainder of the polyol. Care must be taken that the curative (often BDO) is fully soluble in the remainder of the polyol at all temperatures. It is essential to examine the material over time to check for any phase separation. Manufacturers provide solubility data for BDO in various polyols, but it is best to check your own system. 

When these materials are processed, two reactions take place. The polyol side will react with the isocyanate, and the curative will extend the polymer chains to their maximum length. 

Gel time For polyurethanes, the interval of time between mixing together the polyol and diisocyanate or prepolymer and curative and the formation of a nonflowing, semisolid, jelly-like system. 

Chem. Descrip. Highly branched hydroxyl-terminated polyester polyol Uses Polyester for hard, durable exterior coatings and one-shot castables Features Lowm.w. for reaction with isocyanates, alkylated melamines, and other hydroxyl reactive curatives hydrolysis, heal, and chemical resistance, high hardness Rucoflex S-101 [Bayer]... 

Uses Functional polyol for polyurethane industry for industrial/consumer RIM and structural polymers, dynamic elastomers, adhesives, binders, coatings, and sealants reactive diluent, dispersant for solvent coatings, etc. flexibilizerfor PU PU curative and crosslinker ManufJDistrib. Allchem Ind. BASF Bayer Huntsman Polyurethanes Witco... 

Polyol, rigid Polyoxypropyleneamine Polyoxypropylene triol Uses Functional polyol for polyurethane industry for industrial/consumer RIM and structural polymers, dynamic elastomers, adhesives, binders, coatings, and sealants reactive diluent, dispersant for solvent coatings, etc. flexibilizer for PU PU curative and crossiinker Manuf./Distrib. Aiichem Ind. http //www.aiichem.com] BASF http //www.basf.com] Bayer http //www.bayerus.com] Huntsman Poiyurethanes http //www.icipu. com] http //www. rubinate. com Trade Name Synonyms Adeka Polyether PR-3007 [Asahi Denka Kogyo http //www.adk.co.jp]] Baycoll ND 1110 [Bayer/Fiber, Addits., Rubber http //www.bayerus.com]] Baycoll ND 2060 [Bayer/Fiber, Addits., Rubber http //www.bayerus.com]] Baycoll NT 1380 [Bayer/Fiber, Addits., Rubber http //www.bayerus.com]] Baycoll NT 5028 [Bayer/Fiber, Addits., Rubber http //WWW. bayerus. com]... 

Curatives for polyols, isocyanates or isocyanurates play a role of curatives prepolymers are cured either by polyols (frequently multifunctional to obtain tridimensional networks) or by amines considering that amines are very reactive with isocyanate groups, amines are frequently used in a blocked form of ketimines and aldomines which require moisture to hydrolyze them to free reactive amines and this slows curing process up to the extent that frequently catalytic systems have to be used to bring reaction to a required rate ... 

Typical concentration of residual monomer ppm full conversion If Isocyanate would not react with polyol component or curative. It will react with water Spirkova, M Pavlicevic, J Strachota, A Poremba, R Bera, O Kapralkova, L Baldrian, J Slouf, M Lazic, N BudInskl-SImendIc, J, Eur. Polym.J., 47, 959-72,2011. 

Many polyurethane systems commonly are based on reacting either a polyester or polyether polyol with a diisocyanate. Then this isocyanate-terminated prepolymer is later crosslinked with a curative or chain extender, which is typically a diol, triol, or diamine. 

Compatible with a wide range of polyols, co-curatives and all other polyurethane chemicals... 

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