Isocyanate plastic

Isocyanates Plastic foam, synthetic inks, paints and adhesives... 

Isocyanate plastics Group of plastics produced by the condensation of organic isocyanates with other plastics. Examples are the urethane plastics. 

The pulmonary agent phosgene was used extensively as a chemical weapon in WW I. Nowadays, it is an important intermediate for industrial production of insecticides, isocyanates, plastics, aniline dyes and resins, with an estimated yearly production of almost 1 billion pounds. Reliable diagnosis of exposure to phosgene, other than observation of the developing edema by means of chest roentgenology, is not available. 

There may be more than one cause for this syndrome. Complement activation by bioincompatible membranes (H4) hypersensitivity to the ethylene oxide used in dialyzer sterilization, to phthalic anhydride, or to isocyanates (plasticizers) used in potting compounds present in the dialyzer caps and entry of bacterial endotoxin from the dialysate into the bloodstream may each play a role (B22, H4, 12). Hypoxemia and high serum levels of the C3a and C5a complement fragments would suggest complement activation (C2, H4), and peripheral blood eosinophilia and high plasma IgE levels would point to a hypersensitivity reactions. Fever and chills, on the other hand, would incriminate endotoxemia. 

A typical polyurethane sealant formulation may contain a urethane prepolymei an isocyanate, plasticizer, fillers (including carbon black), and several other components. An important criterion is the concentration of residual isocyanate functionality available for further reaction. This may be established by reaction with... 

Isocyanate plastic n. A plastic based on polymers made by the polycondensation of organic isocyanates with other compounds. Reaction of isocyanates with hydroxyl-containing compounds produces polyurethanes having the urethane group -NHC (=0)0-. Reaction of isocyanates with amine-containing compounds produces... 

Ammonia is used in the fibers and plastic industry as the source of nitrogen for the production of caprolactam, the monomer for nylon 6. Oxidation of propylene with ammonia gives acrylonitrile (qv), used for the manufacture of acryHc fibers, resins, and elastomers. Hexamethylenetetramine (HMTA), produced from ammonia and formaldehyde, is used in the manufacture of phenoHc thermosetting resins (see Phenolic resins). Toluene 2,4-cHisocyanate (TDI), employed in the production of polyurethane foam, indirectly consumes ammonia because nitric acid is a raw material in the TDI manufacturing process (see Amines Isocyanates). Urea, which is produced from ammonia, is used in the manufacture of urea—formaldehyde synthetic resins (see Amino resins). Melamine is produced by polymerization of dicyanodiamine and high pressure, high temperature pyrolysis of urea, both in the presence of ammonia (see Cyanamides). 

The amine groups thus formed can also react vigorously with the isocyanate groups to continue the chain extension and cross-linking reactions. Hence, ia the systems there are simultaneous foaming, polymerization, and cross-linking reactions, which produce foam elastomers (or plastics). 

Chain extenders are usually low molecular weight symmetrical diols or diamines. Chain extenders react with isocyanates in the same way as polyols do, but because they are low molecular weight, a high concentration of hydrogen-bonded molecules can associate and phase out of the polyol to form plastic-like domains called hard segments . Hard segments will be discussed in Section 4. Some of the more common diol and diamine chain extenders are shown in Table 3. 

The morphology of a typical urethane adhesive was previously shown in Fig. 3. The continuous phase usually comprises the largest part of the adhesive, and the adhesion characteristics of the urethane are usually controlled by this phase. From a chemical standpoint, this continuous phase is usually comprised of the polyol and the small amount of isocyanate needed to react the polyol chain ends. A wide variety of polyols is commercially available. A few of the polyols most commonly used in urethane adhesives are shown in Table 2. As a first approximation, assuming a properly prepared bonding surface, it is wise to try to match the solubility parameters of the continuous phase with that of the substrate to be bonded. The adhesion properties of the urethane are controlled to a great extent by the continuous phase. Adhesion to medium polarity plastics, such as... 

Group of plastics composed of resins derived from the condensation of organic isocyanates with compounds containing hydroxyl groups. 

The basic RIM process is illustrated in Fig. 4.47. A range of plastics lend themselves to the type of fast polymerisation reaction which is required in this process - polyesters, epoxies, nylons and vinyl monomers. However, by far the most commonly used material is polyurethane. The components A and B are an isocyanate and a polyol and these are kept circulating in their separate systems until an injection shot is required. At this point the two reactants are brought together in the mixing head and injected into the mould. 

The mechanical properties of composites reinforced with wood fibers and PVC or PS as resin can be improved by an isocyanate treatment of those cellulose fibers [41,50] or the polymer matrix [50]. Polymethylene-polyphenyl-isocianate (PMPPIC) in pure state or solution in plasticizer can be used. PMPPIC is chemically linked to the cellulose matrix through strong covalent bonds (Fig. 8). 

---