Polystyrene -polyethylene compositions

Kung, E. Lesser, A. J. McCarthy, T. J. Morphology and Mechanical Performance of Polystyrene/Polyethylene Composites Prepared in Supercritical Carbon Dioxide. Macromolecules 1998, 31, 4160. 

There are a couple of polyethylene-based composites that have shown some success in solid-phase organic synthesis. Merrifield and co-workers [32] introduced a polystyrene-polyethylene composite support in the form of a sheet for solid-phase peptide synthesis, which exhibited an amine loading level of 1.0 mmol amine/g. This material has since been molded into various shapes, including tubing for a continuous-flow peptide synthesizer (reported loading=0.21 mmol amine/m tube or 0.67 mmol amine/g) [33], Geysen and coworkers [34,35] synthesized a poly ethylene-polymethaciy late copolymer which was molded... 

E Kung, AJ Lesser, TJ McCarthy. Morphology and mechanical performance of polystyrene/polyethylene composites prepared in supercritical carbon dioxide. Macromolecules 1998 31 4160 169. 

Electric discharge methods are known [31] to be very effective for nonactive polymer substrates such as polystyrene, polyethylene, polypropylene, etc. They are successfully used for cellulose-fiber modification to decrease the melt viscosity of cellulose-polyethylene composites [32] and to improve the mechanical properties of cellulose-polypropylene composites [28]. 

Composition Polymethyl- methacrylate Polyvinylidene chloride Polystyrene Polyethylene Polytetra fluoroethylene Organo polysiloxane... 

Hydrophobic polymers (polyolefins, polystyrene, polyethylene terephtha-late, pentaplast, fluoroplasts) contain small amounts of polar groups in their macromolecular composition able to interact with water and electrolytes. To that extent, the permeability mechanism of electrol3des in hydrophobic polymers is similar to that of gases. 

Hong et al. [231] have used this simple technique for the synthesis of ZnO-low-density polyethylene composites. ZnO nanoparticles and branched low-density polyethylene was melt-compounded in a high-shear mixer to prepare polymer nanocomposites with an improved resistance to thermal degradation. They also mixed submicron-sized ZnO particles with low-density polyethylene for a comparison and reported that the surface properties of nanoparticles (<100 nm) resulted in an increased thermal stability of nanocomposites. Ma et al. [232] also used melt blending for the synthesis of silane-modified ZnO-polystyrene resin nanocomposites. Incorporation of ZnO nanoparticles results in an increased flexural... 

Many binder systems are used in ceramic injection molding, and they can be classified into five types, based on the composition of the major binder phase (1) thermoplastic compounds, (2) thermosetting compounds, (3) water-based systems, (4) gelation systems, and (5) inorganics. Of these, the thamoplastic compounds are the most widely used and understood. They include most of the common commercial polymers, such as polystyrene, polyethylene, polypropylene, poly(vinylacetate), and poly(methyl methacrylate). Examples of materials used for thermoplastic binder systems are given in Table 6.13. 

A review of the work found above with the preparation of polyethyl-ene-montmorillonite composites, polypropylene (polyethylene with pendant methyl groups)-montmorillonite composites, and polystyrene (polyethylene with pendant phenyl groups)-montmorillonite composites indicates that one can balance the hydrophilic-hydrophobic balance of polyethylene and polypropylene with polar functionality with the hydrophilic-hydrophobic balance of organomontmorillonite more effectively than with a similar strategy as regards polystyrene. 

Zihlif and Ragosta produced short (1-3 mm) BF-reinforced polystyrene (PS) composite plates and found that the strength of the composite went through a maximum whereas both Young s modulus and the impact resistance increased monotonically with increasing BF content. Bashtannik et alP investigated the fiber-matrix interfacial adhesion in BF composites with high density polyethylene (HDPE) matrix. It was found that the properties of BF-reinforced polymer composites were much more sensitive to the BF surface treatment than traditional fiber-reinforced systems. 

Quaternary ammonium (3) and phosphonium ions (61), crown ethers such as (62), cryptands such as (63) and poly(ethylene glycol) ethers (64) bound to PS are catalysts for reactions of water insoluble organic compounds with organic insoluble inorganic salts. " Silica gel, alumina, polystyrene-polypropylene composite fibers, nylon capsule membranes, and polyethylene (Mn 1000-3000) have also been used as supports. The reactions are called phase-transfer-catalyzed because one or both of the reactants are transported from the normal liquid or solid phase into a polymer phase, where the reaction proceeds. 

Starch-thermoplastic polymer composites have also been prepared by graft polymerization. Chemical treatment of starch leads to the development of free radicals in the starch backbone, and these can act in the presence of various polymers (polystyrene, polyethylene, and poly(vinyl halides)) as macroinitiators to yield polymer grafts of high molecular weight [6-8]. 

J. Joshi, Lehman, R., Nosker, T., "Selected physical characteristics of polystyrene/high density polyethylene composites prepared from virgin and recycled materials," J. Appl Polym Sci 99, 2044-2051 (2005). 

There are at the present time many thousands of grades of commercial plastics materials offered for sale throughout the world. Only rarely are the properties of any two of these grades identical, for although the number of chemically distinct species (e.g. polyethylenes, polystyrenes) is limited, there are many variations within each group. Such variations can arise through differences in molecular structure, differences in physical form, the presence of impurities and also in the nature and amount of additives which may have been incorporated into the base polymer. One of the aims of this book is to show how the many different materials arise, to discuss their properties and to show how these properties can to a large extent be explained by consideration of the composition of a plastics material and in particular the molecular structure of the base polymer employed. 

The properties of a polymer depend not only on its gross chemical composition but also on its molecular weight distribution, copolymer composition distribution, branch length distribution, and so on. The same monomer(s) can be converted to widely differing polymers depending on the polymerization mechanism and reactor type. This is an example of product by process, and no single product is best for all applications. Thus, there are several commercial varieties each of polyethylene, polystyrene, and polyvinyl chloride that are made by distinctly different processes. 

Recycling polymers is one way to minimize the disposal problem, but not much recycling occurs at present. Only about 25% of the plastic made in the United States is recycled each year, compared with 55% of the aluminum and 40% of the paper. A major obstacle to recycling plastics is the great variation in the composition of polymeric material. Polyethylene and polystyrene have different properties, and a mixture of the two is inferior to either. Recyclers must either separate different types of plastics or process the recycled material for less specialized uses. Manufacturers label plastic containers with numbers that indicate their polymer type and make it easier to recycle these materials. Table 13-5 shows the recycling number scheme. 

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