Thermoplast Mixtures

M. W. Meszaros, Advances in plastics recycling, thermal depolymerization of thermoplastic mixtures, ACS Symposium Series, 609, 170-182 (1995). 

Figure 6. Schematic phase diagram of a liquid crystal thermoplastic mixture.

Because of the heterogeneous nature of the mixture, and presence of contaminants, the articles produced should have large cross-sections, so that small imperfections do not hinder the mechanical performance of the products. Products can be manufactured by continuous extrusion, compression molding, or by Klobbie-based intrusion processes. Intrusion process is a cross between conventional injection molding and extrusion. In this, the extruder first works and softens the thermoplastic mixture, which is poured into one of the molds without using screen packs or nozzles. Today s recycling equipments are capable of processing most types of mixed thermoplastic material, even with up to 30 to 40 percent contamination as unmelted polymers or nonpolymer materials such... 

Bituminous materials are dark brown or black, semi-solid or liquid, thermoplastic mixtures of hydrocarbons derived from natural or synthetic processes in which hydrocarbon mixtures have lost their volatile components leaving a denser residue. Natural bitumens come from exposed and weathered petroleum and rock deposits. Synthetic bitumens come from the residue remaining after the distillation of petroleum, coal tar, and other organic materials like wood and peat. The complexity of the high molecular weight hydrocarbon oils and resins bitumens contain make complete chemical characterization impossible. The terms bitumen, tar (8007-45-2), pitch (61789-60-4), and asphalt (8052-42-4) apply to any of these substances, although pitch and tar also describe the sticky resins that exude from various trees. 

Thermoplastics are most often used in conjunction with a curing agent such as an amine, but in some instances amine terminated elastomers have been employed. It is known that initially epoxy - thermoplastic mixtures are homogeneous, but at a certain point during curing the thermoplastic may begin to phase separate. 

We noted above that the presence of monomer with a functionality greater than 2 results in branched polymer chains. This in turn produces a three-dimensional network of polymer under certain circumstances. The solubility and mechanical behavior of such materials depend critically on whether the extent of polymerization is above or below the threshold for the formation of this network. The threshold is described as the gel point, since the reaction mixture sets up or gels at this point. We have previously introduced the term thermosetting to describe these cross-linked polymeric materials. Because their mechanical properties are largely unaffected by temperature variations-in contrast to thermoplastic materials which become more fluid on heating-step-growth polymers that exceed the gel point are widely used as engineering materials. 

Cycloahphatic diamines which have reacted with diacids to form polyamides generate performance polymers whose physical properties are dependent on the diamine geometric isomers. (58,74). Proprietary transparent thermoplastic polyadipamides have been optimized by selecting the proper mixtures of PDCHA geometric isomers (32—34) for incorporation (75) ... 

Isomer mixtures are generally obtained. Chlorosulfonation is used to produce chlorosulfonated polyethylene, a curable thermoplastic. Preformed sulfuryl chloride may also be used. 

The problem of solvent selection is most difficult for high molecular-weight polymers such as thermoplastic acryHcs and nitrocellulose in lacquers. As molecular weight decreases, the range of solvents in which resins are soluble broadens. Even though solubihty parameters are inadequate for predicting ah. solubhities, they can be useful in performing computer calculations to determine possible solvent mixtures as replacements for a solvent mixture that is known to be satisfactory for a formulation. 

Commercial engineering thermoplastic nylons are mainly crystalline resins. Nylon-6,6 [32131 -17-2] is the largest volume resin, followed by nylon-6 (48). Other commercially available but much lower volume crystalline nylons are -6,9, -6,10, -6,12, -11, and -12. The crystallinity of the molded part decreases with chain size (49). A few truly amorphous commercial nylon resins contain both aromatic and ahphatic monomer constituents (50). For example, Trogamid T resin is made from a mixture of 2,2,4- and 2,4,4-trimethylhexamethylenediamines and terephthahc acid (51). 

The term epoxy is familiar to nonchemists because of the widespread use of epoxy glues and resins. These are crosslinked polyether thermoplastics made from a liquid resin which is typically a mixture of bisphenol A diglycidyl ether (70) and a polymer (71 Scheme 86). The liquid resin is cured or hardened to the final resin by mixing with a crosslinking reagent, which can be an acid, a di- or poly-alcohol, or a di- or poly-amine (Scheme 86). 

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