Toluene diisocyanate, chain

These foams are produced from long-chain, Hghtiy branched polyols reacting with a diisocyanate, usuaUy toluene diisocyanate [1321 -38-6] (TDI), to form an open-ceUed stmcture with free air dow during dexure. During manufacture these foams are closely controUed for proper density, ranging from 13 to 80 kg/m (0.8—5 lbs/ft ), to achieve the desired physical properties and cost. 

Another class of hydrocarbon binders used in propints are the carboxy-terminated polybutadiene polymers which are cross-linked with either tris[l-(2-methyl)aziridinyl] phosphine oxide (MAPO) or combinations with phenyl bis [l -(2-methyl)aziridinyl] phosphine oxide (Phenyl MAPO). Phenyl MAPO is a difunctional counterpart of MAPO which makes possible chain extension of polymers with two carboxylic acid groups. A typical propint formulation with ballistic properties is in Table 11 (Ref 83) Another class of composites includes those using hydroxy-terminated polybutadienes cross-linked with toluene diisocyanate as binders. The following simplified equations illustrate typical reactions involved in binder formation... 

Biodegradable poly(phosphoester-urethanes) containing bisglycophosphite as the chain extender were synthesized. Methylene bis-4-phenyl isocyanate (MDI) and toluene diisocyanate (TDI) were initially used as diisocyanates. Since there was a concern that the degradation products could be toxic, the ethyl 2,6-diisocyanatohexanoate (LDI) was synthesized and replaced the MDI (or TDI). The hydrolytic stability and solubility of these polymers were tested. Preliminary release studies of 5-fluorouracil from MDI based poly(phosphoester-urethane) and methotrexate from LDI based poly(phosphoester-urethane) are also reported. 

Considering supply-chain systems, the use of relatively non-hazardous raw materials is envisaged. Hazardous products should be used only locally and intermediately. If both products and raw materials are hazardous for a given process, it is recommended to include further processes until returning to non-hazardous raw materials. In this case, an entire sequence of plants is needed. In this context, Rinard outlines a supply-chain system for the manufacture of toluene diisocyanate. Although chlorine is used in the system, it is not present in either the starting raw materials or the product. 

Following the early developments using NDI, it was found that by using TDI instead, a far more stable prepolymer could be made. Stable prepolymers are normally made using either polyesters or polyethers that have been reacted with a slight excess of a diisocyanate such as toluene diisocyanate (TDI) or methylene diisocyanate (MDI). Provided the storage is moisture free, the stable prepolymer may be kept for months before use. The polyurethane is prepared by chain extension with diols or diamines. 

There are regulatory and handling problems in using methylene bis(2-chloroaniline) as a chain extender (curative or cross-linker) for toluene diisocyanate (TDI)-terminated prepolymers, to produce urethane elastomers (1,2). There is, therefore, a strong interest in achieving similar elastomer properties with other curatives and methylene diphenyl diisocyanate (MDI)-terminated prepolymers(3,4). 

A number of different hindered diamines have been investigated as a substitute for MOCA (1). In addition to diamine curing agents, which are used most frequently with elastomers based on polyether polyols and toluene diisocyanate (TDI), prepolymers based on polyether or polyester polyols and 4,4 -diphenylmethane diisocyanate (MDI), can be cured with diols to yield elastomers with similar properties to those of diamine-cured polyester-TDI elastomers. The most common chain extender is butanediol. However, to achieve improved mechanical properties, especially at elevated temperatures, aromatic diols are often used. The most common one is hydroquinone di-(beta-hydroxy-ethyl) ether (HEQ). 

Type I. The soft segment consists only of polyether chains (of one kind) connected at each end to a hard-segment triad consisting of diisocyanate-diamine-diisocyanate, where the diisocyanate is either toluene diisocyanate (TDI) or isophorone diisocyanate (IPDI). 

As compared to metallic compounds used as shape memory materials, shape memory polymers have low density, high shape recoverability, easy processability, and low cost. Since the discovery by Mitsubishi in 1988, polyurethane SMPs have attracted a great deal of attention due to their unique properties, such as a wide range of shape recovery temperatures (— 30°C to 70°C) and excellent biocompatibility, besides the usual advantages of plastics. A series of shape memory polyurethanes (SPMUs), prepared from polycaprolactone diols (PCL), 1,4-butanediol (BDO) (chain extender), and 4,4 -diphenylmethane diisocyanate (MDI) or toluene diisocyanate (TDI) have recently been introduced [200—202]. 

Waterborne polyurethane resins are produced from maleinised monoglyceride (MMG) of sunflower oil, hydroxy-terminated polybutadiene, toluene diisocyanate and ethylene diamine. The carboxylic acid groups of MMG are neutralised by triethyl amine, making the resin water dispersible. The monoalkylated castor oil (MCO) or dehydrated castor oil (DCO) is treated with a polyether glycol at 120°C, followed by the addition of IPDI and DBTDL. To obtain a series of aqueous polyurethanes, butane diol and dimethylol propionic acids (DMPA) are added and the mixture heated to 70°C for two hours to produce a NCO-terminated pre-polymer which forms salt with triethylamine, giving a water-soluble polymer. The reaction mixture is dispersed in water and a chain extender, ethylene diamine, is added. Two aqueous polyurethanes, MCPU and DCPU, are finally obtained from MCO and DCO, respectively. 

Effects of various chemical treatments such as sodium hydroxide, isocyanate, permanganate, and peroxide on the tensile properties of sisal fiber-reinforced low-density polyethylene (LDPE) composites were investigated. Sodium hydroxide treated fiber composites showed better tensile properties than xmtreated composites, and the enhancement was attributed to their rough surface topography and increased aspect ratio. It was reported that long chain structured cardanol derivative of toluene diisocyanate (CTDIC) treatment reduces the hydrophilic nature of the sisal fiber resulting in improved compatibility and dispersion. It was also reported that peroxide treatment of fiber showed maximum interfacial interactions [33]. 

Cross-bnking agents Molecules that have two or more groups capable of reacting with the functional groups of polymer chains, where such a reaction connects or links the chains 2-Mercaptobenzothiazole, benzoyl peroxide, dicumyl peroxide, sulfur, toluene diisocyanate... 

Chain extender choice influences elastomer properties considerably. When a diamine is employed as extender, a higher level of physical properties usually results than if a diol were used, probably due to the introduction of urea linkages which enter into strong hydrogen-bonded interactions. A diamine is usually chosen as the chain extender when a relatively unsymmetrical diisocyanate is employed this is particularly true of polymers made by the prepolymer route and applies especially to the use of mixed toluene diisocyanates and to methylene diisocyanates whose bulky or hindered structure and, to some extent, their stereo configurations (see Fig. 3.5), limit the linearity in the polymer chain which is an essential feature of strength and elasticity in all rubber materials. 

However it is also established that the commonly used diphenylmethane and naphthalene diisocyanate-based elastomers are frequently chain-extended with glycols. Table 3.12 contrasts the effects of diamine and glycol chain extenders with a toluene diisocyanate/polyether-based prepolymer, Adiprene LI00. With the unsymmetrical diisocyanates, such as TDI and MDI, polyol chain extenders give elastomers of poorer properties than diamines, and it is usually desirable to introduce additional crosslinking into diol-extender elastomers by the use of a proportion of a triol such as... 

DIAMINE CHAIN-EXTENDER CONTROL OF THE PHYSICAL PROPERTIES OF TOLUENE DIISOCYANATE-BASED ELASTOMERS... 

When a rigid and bulky diol is used as the chain extender, harder elastomers of higher modulus are produced. It can be seen in Table 3.14 that a toluene diisocyanate-based composition (A) from the bulky diol 1,4-dihydroxy-1,2,3,4-tetrahydronaphthalene is inferior in tensile properties to the diphenylmethane diisocyanate-based material (C), although composition (A) is superior to the elastomer from 1,4-butane diol (B). A similar situation can be seen with composition (E), where a,a -dihydroxyxylene was used, compared with composition (D) based on 1,4-butane diol. 

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