Poly degradation behavior monomer

Photophysical Processes and Photodegradation of Poly(ethylene terephthalate-co-2,6-naphtha1enedi carboxyl ate) Copolymers. We have recently reported the photophysical processes and the photo-degradative behavior of Doly(ethylene terephthalate-co-2,6-naphthalenedicarboxyl ate), PET-2,6-ND, copolymer yarns containing 0.5 - 4.0 mole percent 2,6-naphthalenedicarboxyl ate, 2,6-ND (1) and the parent naphthalenedicarboxyl ate monomer, Figure 3 and 4. 

The solution behavior of poly(amic acids) was until recently, probably the least understood aspect of the soluble polyimide precursor. However, the advent of sophisticated laser light scattering and size exclusion chromatography instrumentation has allowed elucidation of the solution behavior of poly(amic adds). In the early days of polyimide chemistry, when most molecular weight characterization was based on viscosity determinations, a decrease in viscosity was associated with molecular weight degradation [15, 28, 29]. Upon combination of the two monomers an increase in the viscosity to the stoichiometric equivalence point is observed, followed by a decrease in the solution viscosity as a... 

After the examination of the PS photooxidation mechanism, a comparison of the photochemical behavior of PS with that of some of its copolymers and blends is reported in this chapter. The copolymers studied include styrene-stat-acrylo-nitrile (SAN) and acrylonitrile-butadiene-styrene (ABS). The blends studied are AES (acrylonitrile-EPDM-styrene) (EPDM = ethylene-propylene-diene-monomer) and a blend of poly(vinyl methyl ether) (PVME) and PS (PVME-PS). The components of the copolymers are chemically bonded. In the case of the blends, PS and one or more polymers are mixed. The copolymers or the blends can be homogeneous (miscible components) or phase separated. The potential interactions occurring during the photodegradation of the various components may be different if they are chemically bonded or not, homogeneously dispersed or spatially separated. Another important aspect is the nature, the proportions and the behavior towards the photooxidation of the components added to PS. How will a component which is less or more photodegradable than PS influence the degradation of the copolymer or the blend We show in this chapter how the... 

The same authors have also studied the effects of particle size on the rate of production of monomer during thermal degradation of poly(methyl methacrylate) and observed that the rate increases with particle size for particles smaller than about 50 mesh but it does fall away for larger particles. The study of the effect of layer thickness on the rate of mononrer production has also revealed the similar pattern of behavior of the polymer towards (tegradation. Several reasons for this behavior of the (tegradation are mentioned. "ITiese are ... 

A third pyrolysis behavior is evidenced by polymers such as poly(methyl methacrylate). Because of the structure of methacrylate polymers (structure Vll), the favored degradation is essentially a reversion to the monomer. 

The TG/GC/MS experiments were even more revealing. The experiments were identical to those described earlier except that the volatiles formed from degradation of the polymer were carried onto the GC column prior to the mass selective detector. Again, the head-to-head sample lost very little mass at 280 °C for 80 min. The behavior of the conventional polymer stands in sharp contrast to that of the head-to-head polymer. The TG/GC/MS chromatogram is shown in Figure 11.4. The only volatile compound formed from initial degradation of conventional poly(styrene) at 280 C is styrene monomer. 

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