Polystyrene mechanical strength

The Polystyrene Family. After 1945 there was a drastic drop in the demand for styrene monomer because the need for synthetic rubber suddenly declined. On the other hand, a big demand existed for goods in the civilian sector and this provided a strong impetus to the expansion of polystyrene. In many cases, however, the mechanical strength of polystyrene was inadequate and this initiated numerous research efforts, especially in the immediate postwar period. 

The major features for advanced photo-systems relative to the base film are a small-size thrust cartridge and return inside the cartridge. These features require low core-set curl values and high mechanical strength. The cellulose triacetate (CTA), polycarbonate and PET materials currently used in the photographic industry are not able to satisfy these requirements. Some newly developed film materials, such as modified-PET and syndiotactic polystyrene, were also unable to satisfy such requirements. It is known that annealing films just below the Tg (BTA treatment) could reduce core-set curl tendencies. BTA treatments of... 

The lack of mechanical strength for thermoplastic hyperbranched polymers makes them more suitable as additives in thermoplast applications. Hyperbranched polyphenylenes have been shown to act successfully as rheology modifiers when processing linear thermoplastics. A small amount added to polystyrene resulted in reduced melt viscosity [31]. (Sect> 3.1). 

PB—RDX (Plastic-Bonded RDX) was developed by Los Alamos Scientific Laboratory of the University of California for use as a mechanical strength expl. It consisted of RDX 90, polystyrene 8.5 dioctylphthalate 1.5% (Ref 70,... 

Berlin and coworkers (5,56) desired to obtain a material with an increased mechanical strength. They carried out a plasticization of bulk ami emulsion polystyrene molecular weight 80000 and 200000 respectively at 150-160° C, with polyisobutylene, butyl rubber, polychloroprene, polybutadiene, styrene rubber (SKS-30) and nitrile rubber (SKN 18 and SKN 40). The best results were obtained with the blends polystyrene-styrene rubber and polystyrene-nitrile rubber. An increase of rubber content above 20-25% was not useful, as the strength properties were lowered. An increase in the content of the polar comonomer, acrylonitrile, prevents the reaction with polystyrene and decreases the probability of macroradical combination. This feature lowers the strength, see Fig. 14. It was also observed that certain dyes acts as macroradical acceptors, due to the mobile atoms of hydrogen of halogens in the dye, AX ... 

Among the plastics which in addition to being combustible ingredients of these mixtures serve also as binders imparting mechanical strength to the charges, the following substances have recently become of considerable interest methyl methacrylate, polystyrene. 

In order to prepare non-styrenic polymer-supported organotin chlorides, which are expected to show physical properties such as mechanical strength, polarity and porosity different from those of polystyrene-based supports, Deleuze and coworkers copolymerised dibutyl[3-(allyloxy)propyl]tin chloride with N-phenylmaleimide (PMI) and l,l/-(methylene-4,l-phenylene)bismaleimide (MPBMI) to prepare the polymers 88a and 88b180. 

Neither PVC nor polystyrene is very crystalline and polystyrene often has poor mechanical strength. Both of these maybe results of the stereorandom nature of the polymerization process. The substituents (Cl or Ph) are randomly to one side or other of the polymer chain and so the polymer is a mixture of many diastereoisomers as well as having a range of chain lengths. Such polymers are called atactic. In some polymerizations, it is possible to control stereochemistry, giving (instead of atactic polymers) isotactic (where all substituents are on the same side of the zig-zag chain) or syn-diotactic (where they alternate) polymers. 

In a previous study we established that classical peroxydes could not play the major role in interfacial bonding. Bulk reactions, especially in polystyrene matrix, lead to chain degradation and related decrease of mechanical strength. Therefore,... 

One signiflcant problem which is associated with the convenhonal polystyrene supports is that of low mechanical strength and often poor thermo-oxidahve stability. The immobilization of TADDOL derivatives on mechanically stable and chemically inert polyethylene (PE) fibers by means of electron beam-induced grafting has also been investigated. The TADDOL-containing fibers 15 obtained were transformed into the htanium TADDOLate and used for the asymmetric ethylation of benzaldehyde in quanti tative yield and 94% ee [12]. 

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