Molding high molecular weight

Thermoplasticity. High molecular weight poly(ethylene oxide) can be molded, extmded, or calendered by means of conventional thermoplastic processing equipment (13). Films of poly(ethylene oxide) can be produced by the blown-film extmsion process and, in addition to complete water solubiUty, have the typical physical properties shown in Table 3. Films of poly(ethylene oxide) tend to orient under stress, resulting in high strength in the draw direction. The physical properties, melting behavior, and crystallinity of drawn films have been studied by several researchers (14—17). 

The largest use for 2,4-dicumylphenol is in a production of a uv stabilizer of the benzotriazole class, 2-(2 -hydroxy-3, 5 -dicumylphenyl)benzotriazole [70321-86-7] which is used in engineering thermoplastics where high molding temperatures are encountered (67). The high molecular weight of... 

Because plastics are almost invariably modified with one or more additives, there are three components of chemical analysis the high molecular weight portion, ie, the polymer the additives, ie, plasticizer and mold-release agent and the residuals remaining from the polymerization process. The high... 

Amine-terminated siloxane oligomers have also been utilized in the synthesis of various siloxane-amide and siloxane-imide copolymers, High molecular weight siloxane-amide copolymers have been synthesized by the solution or interfacial co-polymerization of siloxane oligomers with sebacoyl chloride or terephthaloyl chloride respectively 1S5,165). In some reactions diamine chain extenders have also been utilized. Thermal and dynamic mechanical characterization of these copolymers have shown the formation of multiphase systems160). Compression molded films displayed very good elastomeric properties. 

Even though PBT does not generally stick to tooling, a low level of mold release added to the polymer has been shown to improve molding performance in some instances. High-molecular-weight aliphatic esters, amides or polyolefins are commonly used to enhance mold-release properties. 

Minnick, L. A., Reinforced molding composition based on poly(l,4-cyclohexylenedimethylene terephthalate) containing a high molecular weight aliphatic polyester, US Patent 5 242 967, 1992. 

Requirements for CD-quality material are polycarbonate with low levels of chemical impurities, low particle levels, thermal stability, excellent mold release, excellent clarity, as well as constant flow and constant mechanical behavior (for reproducibility). There exists a time/cost balance. High molecular weight polycarbonate offers a little increase in physical property but the flow rate is slow, making rapid production of CDs difficult. The molecular weight where good mechanical strength and reasonable flow occurs, and that allows for short cycles, is in the range of 16,000-28,000 Da. 

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