Poly weight loss changes

Figure 2.6 Weight loss changes of initially amorphous PLAiqoa and semi-crystalline PLAiqqc during in vitro degradation. PLA, poly(lactic acid).

Sulfone-hased polymers show a very good resistance to prolonged chlorine exposure at elevated temperatures. The weight change after an exposure of 6 months to static chlorinated water at 60°C at chlorine levels of up to 30 ppm is essentially zero for Udel , whereas e.g., poly(acetal) exhibits a weight loss of ca. 5% at 30 ppm chlorine in water after 6 months. This property suggests applications in water delivery systems. 

Thermal degradation of poly(caprolactone) at 220 0 was recently investigated (23). It proceeds by a zipping-off mechanism yielding monomeric caprolactone without change in reduced viscosity up to a weight loss of 53%. This means that the rate of random dissociation is small as compared to the rate of depropagation and an active species once formed will disappear immediately. 

Fig. 7 - In vivo degradation of racemic poly(lactide) films (rabbits) Change in viscosity of excised implants. Weight loss indicated.

Also, the high molecular weight poly(anhydride)s are melt processable under inert atmospheric conditions at temperatures greater than 200°C. The high molecular weight poly(anhydride)s are also stable to Cobalt irradiation without loss of mechanical properties, molecular weight, or changes in chemical structure. 

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