Polycarbonate degradation mechanisms

McNeill, I.C. and Leiper, H.A. (1985) Degradation studies of some polyesters and polycarbonates 2. Polylactide Degradation under isothermal conditions, thermal degradation mechanism and photolysis of the polymer. Polymer Degradation and Stability, 11,309-326. 

FTIR techniques in combination with or as complement to other measurement techniques have been used in a wide range of photochemistry studies on polymers. These include bisphenol-A polycarbonate [173], polycarbonate coatings on mirrors [174], PMMA [175], poly( -butyl acrylate) [176] and polypropylene [177]. DSC and FTIR studies have been used in conjunction to investigate the nature of y-radiation-induced degradation and its effect on the 19°C and 30°C phase transitions in PTFE [178]. IR studies of the hydrolysis of melamine-formaldehyde crosslinked acrylic copolymer films have shown that copolymer-melamine formaldehyde crosslinks are broken and that crosslinks between melamine molecules are formed [179]. The thermal and photo-degradation mechanisms in an IR study of cured epoxy resins were found to be related to the autoxidative degradation processes for aliphatic hydrocarbons [180]. 

If a polymer contains structures that can absorb terrestrial sunUght wavelengths (>290-300 nm), which leads to chemistry causing changes in molecular structure, photolysis can be an important degradation mechanism. Norrish I and II of carbonyl, ester, or amide containing polymers (e.g., oxidized PE, PES, and PAs) and the photo-Fries reaction in bi-sphenol A polycarbonate (BPA-PC) are well-known photolytic reactions [52]. These reactions are shown in Schemes 18.4-18.6. 

Uyar et al. recently demonstrated with the support of DPMS that both the phase structures and the properties of polymer blends can be modified by processing with cyclodextrines (CDs). In fact, thermal stabilities and thermal degradation mechanisms of mixed blends of polycarbonate/PMMA (PC/PMMA), PC/PVAc and PMMA/... 

Patterson, P.H., Sloan, J.M., Hsieh, A.J. Photo degradation mechanisms of layered silicate/polycarbonate nanocomposites. In Annual Technical Conference of the Society of Plastics Engineering, p. 3936 (2002)... 

Our results of GPC and Raman Spectroscopy confirm polymer degradation in the reprocessed resins. Additional analysis would have to be made to determine more specific information about the degradation mechanisms, particularly for polycarbonate. In both of the samples, significant sample contamination was found due to resin reuse and regrinding in the case of the Nylon 6,6 samples. 

K.H. Pawlowski and B. Schartel, Flame retardancy mechanisms of aryl phosphates incombination with boehmite in bisphenol A polycarbonate/acrylonitrile butadiene styrene blends, Polym. Degrad. Stabil., 2008, 93 657-667. 

Some polymers show discoloration as well as reduction of the mechanical properties (e.g. aromatic polyesters, aromatic polyamides, polycarbonate, polyurethanes, poly (phenylene oxide, polysulphone), others show only a deterioration of the mechanical properties (polypropylene, cotton) or mainly yellowing (wool, poly(vinyl chloride)). This degradation may be less pronounced when an ultraviolet absorber is incorporated into the polymer. The role of the UV-absorbers (usually o-hydroxybenzophenones or o-hydroxyphenylbenzotriazoles) is to absorb the radiation in the 300-400 nm region and dissipate the energy in a manner harmless to the material to be protected. UV-protection of polymers can be well achieved by the use of additives (e.g. nickel chelates) that, by a transfer of excitation energy, are capable of quenching electronically excited states of impurities (e.g. carbonyl groups) present in the polymer (e.g. polypropylene). 

Mechanisms of degradation in condensation polymers, and the stabilisation of these polymers and non-polyolefin polymers such as poly(vinyl chloride) using organophosphites is discussed in terms of the stability of colour, thermal properties and molecular weight. Stabilisation of poly(ethylene terephthalate) and polycarbonate by organophosphites was studied experimentally. 5 refs. 

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