Thermoplastic degradation products

Thermosets and thermoplastics behave differently from each other in fires. Thermosets do not melt when heated but may well undergo further crosslinking. The presence of such additional crosslinks hinders movement of any volatile degradation products through the polymer matrix. Hence the combustion zone tends to be starved of fuel and for this reason thermosets tend to be relatively non-flammable. 

Bart and co-workers [25] and others [34, 101, 163] have reviewed the application of TG-MS for the study of polymeric materials, thermoplastics, thermosets and elastomers. This thermoanalytical technique is used for the structural characterisation of homopolymers, copolymers, polymeric blends and composites and finds application in the detection of monomeric residuals, solvents, additives, (toxic) degradation products, etc. Information is... 

This section presents information and data related to thermal stability of resins and basic properties as a function of temperature. Thermal stability of fluoropolymers has special importance because of the high processing temperatures required by these thermoplastics and the toxic and corrosive nature of their degradation products. Fluoroplastics have useful properties at temperature extremes above and below ambient conditions. 

Aranjo, M. A., Cunha, A. M., and Mota, M. (2004). Enzymatic degradation of starch based thermoplastic compounds used in protheses Identification of the degradation products in solution,... 

Figure 3.5 Programmed TGA to 800 °C under nitrogen at 5 °C/min of stoichiometric thermoset resins based on DGEBA. DDM resin cured with diamino diphenyl methane, mPDA resin cured with m-phenylene diamine, pPDA resin cured with p-phenylene diamine, mXDA resin cured with weto-xyylene diamine, AN the stoichiometric thermoplastic reaction product of DGEBA and aniline (included for comparison). Reproduced with permission from T. Dyakonov, P.J. Mann, Y. Chen and W.T.K. Stevenson, Polymer Degradation and Stability, 1996,...

Azodicarbonamide (AZC) is by far the most widely used CBA. It can foam PVC, including plasticised PVC, as well as the polyolefins, the styrenics, polyamides, PPO and some thermoplastic elastomers. AZC decomposes exothermically at around 210 °C to give nitrogen gas, along with other degradation products such as mea, cyanuric acid and cyamelide as solid by-products. Another possible residue is semicarbazide, traces of which have been found in foamed gaskets made of PVC blown with azodicarbonamide (see Chapter 7). 

EarUer studies on polythioacetals, mainly aliphatics, revealed limited possibilities to utilize these materials as potential industrial thermoplastics because of their instability in the molten state as well as an offensive odor of some monomers and degradation products (2,259-261). Aromatic polythioacetals (262-264) and thiacrown ethers bearing thioacetal linkages (36,37,262,265-267) have recently received increasing attention. 

With the renewed interest in environmentally friendly products, ceUulose esters are being re-evaluated as a natural source of biodegradable thermoplastics. CeUulose acetates are potentiaUy biodegradable (152). Films prepared from a ceUulose acetate with a DS of 2.5 were shown to require only a 10—12 day incubation period for extensive degradation in an in vitro enrichment assay. Similarly, films prepared from a ceUulose acetate with a DS of 1.7 saw 70% degradation in 27 days in a wastewater treatment facUity, whereas films prepared from a ceUulose acetate with a DS of 2.5 required approximately 10 weeks for similar degradation to occur. The results of this work demonstrate that ceUulose acetate fibers and films are potentiaUy environmentally nonpersistant. 

Advantages The major advantages of the thermoplastic-based disposal systems are by dispiosin of the waste in a dry condition, the overall volume of the waste is greatly reduced most thermoplastic matrix materials are resistant to attack by aqueous solutions microbial degradation is minimal most matrices adhere well to incorporated materials, therefore, the final product has good strength and materials embedded in a thermoplastic matrix can be reclaimed if needed. 

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