Multicomponent systems thermoplastic

For thermoplastic composites, results of flammability tests are generally reported on the basis of oxygen index values and/or UL-94 ratings (e.g. (11-12). The general problems associated with composites and multicomponent systems have not been addressed in depth and published data pertain primarily to specific glass-filled resins offered by manufacturers, or to composite systems designed to meet the specifications of a particular end use. 

In composite, multicomponent systems, 2H NMR is particularly suited to investigate interfacial properties. This is illustrated in filled rubbers, semicrystalline and thermoplastic elastomers, based on copolymers (Section 15.5). 

Important aspects relating to the development of phase morphologies in polymer-based multicomponent systems were discussed. Focus is made on the co-continuous phase morphology in binary and ternary thermoplastics blends. 

Abstract Multicomponent materials based on synthetic polymers were designed and used in a wide variety of common and hi-tech applications, including the outdoor applications as well. Therefore, their response to the UV radiation and complex weathering conditions (temperature, seasonal or freeze—thaw cycles, humidity, pH, pollutants, ozone, microorganisms) is a matter of utmost importance in terms of operational reliability and lifetime, protection of the environment and health safety. This chapter offers an overview of this subject and a critical assessment of more particular topics related to this issue. Thus, various types of multicomponent systems based on thermoplastic and thermosetting polymer matrices were subjected to natural and/or simulated UV radiation and/or weathering conditions. Their behavior was evaluated in correlation with their complex formulation and taking into consideration that the overall effect is a sum of the individual responses and interactions between components. The nature and type of the matrix, the nature, type and size distribution of the filler, the formation of the interphase and its characteristics, the interfacial adhesion and specific interfacial interactions, they all were considered as factors that influenced the materials behavior, and, at the same time, were used as classification criteria for this review. 

Particulate inorganic fillers, such as clays, mica, talc, calcium carbonate, graphite or graphite oxide, have attracted some attention in the study of photochemical behavior of multicomponent systems as they were considered a possible solution to protect these materials from the UV degradation. In this section, only microscale composites based on thermoplastic matrices were considered. 

Torque rheometers are multipurpose instruments well suited for formulating multicomponent polymer systems, studying flow behavior, thermal sensitivity, shear sensitivity, batch compounding, and so on. The instrument is applicable to thermoplastics, rubber (compounding, cure, scorch tests), thermoset materials, and liquid materials. 

This year s U.S. production of thermoplastics, thermosets, and synthetic rubber is expected to be 29 billion pounds. About 80% of this is based on only a few common monomers. To improve performance, the polymer industry rarely changes to a new, probably more expensive polymer, but instead it shifts from mere homopolymers to copolymers, polyblends, or composites. These three types of multicomponent polymer systems are closely inter-related. They are intended to toughen brittle polymers with elastomers, to reinforce rubbers with active fillers, or to strengthen or stiffen plastics with fibers or minerals. 

Multiphase or multicomponent polymers can clearly be more complex structurally than single phase materials, for there is the distribution of the various phases to describe as well as their internal structure. Most polymer blends, block and graft copolymers and interpenetrating networks are multiphase systems. A major commercial set of multiphase polymer systems are the toughened, high impact or impact modified polymers. These are combinations of polymers with dispersed elastomer (rubber) particles in a continuous matrix. Most commonly the matrix is a glassy amorphous thermoplastic, but it can also be crystalline or a thermoset. The impact modified materials may be blends, block or graft copolymers or even all of these at once. 

Commingled plastics belonging to different chemical families, e.g., mixtures of PO s with either PA s or PEST s, or multicomponent mixtures comprising PO, PS, PVC, and en neering thermoplastics, etc. Usually these systems need extensive compatibilization and impact modification. 

Three main types of multicomponent polymer systems will be discussed (1) combinations of two or more semicrystalline polymers, (2) impact modified thermoplastics and (3) impact modified thermosets. The microstructure of semi-crystalline multicomponent polymers can often be determined by polarized light microscopy of thin... 

It should be emphasized that the molecular theories presented in this chapter are valid only for flexible homopolymers and thus they cannot describe the rheological behavior of stmctured polymer systems, including multicomponent and/or multiphase polymers, such as block copolymers, liquid-crystalline polymers, thermoplastic polyurethanes, immiscible polymer blends, highly filled polymers, and nanocomposites. We discuss this subject in the remaining chapters of this volume. 

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