Polycarbonates Subject

With the exception of the 30% TCBA copolymer, the same was essentially true for the polycarbonates subjected to UV aging as well. Of all the polymers tested only the mixed TCBF copolymer showed some resistemce to attack by ammonium hydroxide. The 70% TCBF copolymer possessed the highest glass transition temperature (190 C.) of any of the polycarbonates studied. 

The infrared spectrum of the residue of polycarbonates subjected to pyrolysis at 500°C contains no bands characteristic of methyl groups the intensity of the absorption bands of the ester groups -C = O and -C-O-C-is significantly reduced, and the absorption bands corresponding to the benzene ring are intensified. 

Fig. 157. Kinetics of the thermal destruction of samples of polycarbonate, subjected to oxidation of varying duration. 1) Without preliminary oxidation 2) oxidation for 50 min 3) 90 min 4)...

A comparison of the data on the change in chemical properties and molecular weight of polycarbonate subjected to reprocessing under the conditions of various systems (Fig. 155) showed that the drop in strength is due to a decrease in the molecular weight of the polymer. 

Materials made from polycarbonates are transparent, strong, and heat-and break-resistant. However, these materials are subject to stress crack-... 

In terms of tonnage the bulk of plastics produced are thermoplastics, a group which includes polyethylene, polyvinyl chloride (p.v.c.), the nylons, polycarbonates and cellulose acetate. There is however a second class of materials, the thermosetting plastics. They are supplied by the manufacturer either as long-chain molecules, similar to a typical thermoplastic molecule or as rather small branched molecules. They are shaped and then subjected to either heat or chemical reaction, or both, in such a way that the molecules link one with another to form a cross-linked network (Fig. 18.6). As the molecules are now interconnected they can no longer slide extensively one past the other and the material has set, cured or cross linked. Plastics materials behaving in this way are spoken of as thermosetting plastics, a term which is now used to include those materials which can in fact cross link with suitable catalysts at room temperature. 

The photochemical degradation of bisphenol-A polycarbonate (PC) has been the subject of a number of investigations.-3 ... 

The polycarbonate glazing is modeled as a simply supported plate subjected to nonlinear center deflections up to 15 times the pane thickness. Using the finite element solution of Moore (Reference 4), the resistance function is generated for each pane under consideration. Typically, the resistance is concave up, as illustrated for typical pane sizes in Figure 1. This occurs because membrane stresses induced by the stretching of the neutral axis of the pane become more pronounced as the ratio of the center pane deflection to the pane... 

Some nonconductors, such as the polymers polycarbonates and polystyrenes, must be subjected to a surface treatment prior to activation to ensure good adhesion of palladium nuclei. Surface treatment can include the use of chemical etchants for plastics or reactive gas plasma treatments (66). 

Industry estimates indicate that up to 5% of the total resin production finds its way into prototype or mill shape plastic products. By mill shapes is meant those primary uniform configuration subject to established cross-sectional and length tolerances. While this estimate is necessarily conjectural, the best available information indicates that this range is accurate. Modem Plastics magazine estimated mill shape production for 1968 in acrylics, cellulose, nylon, acetal, polycarbonate, high density polyethylene, polypropylene, poly(vinyl chloride), and copolymers to approach 336.4 million pounds. Total United States resin production for 1968 slightly exceeded 16 billion pounds. 

Polymers are large molecules (macromolecules) that consist of one or two small molecules (monomers) joined to each other in long, often highly branched, chains in a process called polymerization. Both natural and synthetic polymers exist. Some examples of natural polymers are starch, cellulose, chitin (the material of which shells are made), nucleic acids, and proteins. Synthetic polymers, the subject of this chapter, include polyethylene, polypropylene, polystyrene, polyesters, polycarbonates, and polyurethanes. In their raw, unprocessed form, synthetic polymers are sometimes referred to as resins. Polymers are formed in two general ways by addition or by condensation. 

Blending of polymers is an attractive method of producing new materials with better properties. Blends of aliphatic polyesters, especially of poly(e-CL), have been investigated extensively and have been the subject of a recent review paper [170]. Poly(e-CL) has been reported to be miscible with several polymers such as PVC, chlorinated polyethylene, SAN, bisphenol A polycarbonate, random copolymers of Vdc and VC, Vdc and AN, and Vdc/VAc, etc. A single composition-dependent Tg was obtained in the blends of each of these polymers with poly(e-CL). This is of interest as a polymeric plasticizer in these polymers. Blends of PVC and poly(e-CL) with less than 50 wt % of poly(e-CL) were homogeneous and exhibited a single Tg. These blends were soft and pliable because the inherent crystallinity of poly(e-CL) was destroyed and PVC was plasticized... 

Polycarbonate is very strong and as transparent as glass. It is subject to reactions from bases and strong acids and can be dissolved in some solvents. 

Among the contrarians, Bayer has had for historical reasons a different approach to the problem of remaining a well-rounded producer of chemicals. It has always been a leader in such specialty chemicals as plastics and rubber additives and supplies master batches through its subsidiary Rhein Chemie. Its polymers are mainly centered on synthetic elastomers and specialty plastics like polyurethanes and polycarbonates that Bayer itself develops. These are not subjected to the cutthroat competition that commodity thermoplastics are. Bayer has remained involved in aroma chemicals with a well-known subsidiary, Haarmann Reimer. In pharmaceuticals the company occupies an honorable rank, although in the future its management may want to separate that branch from the rest of its activities in preparation for further alliances. Like BASF, Bayer considers its agrochemical line as a core business. However, unlike BASF, it is less interested in integrating upstream production to oil raw... 

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