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Biodegradable poly(-lactide) (PLA)/silica (SiO) nanocomposites were prepared by melt compounding to investigate the effect of spherical nanofillers on the thermal stability of PLA. The nanocomposites displayed improved thermal stability both under nitrogen and in air. The stabilization mechanism was attributed mainly to the barrier effect of the network formed, which was demonstrated by the improved barrier properties and rheological performance. The dispersion of nanofiller and matrix-nanoparticle interactions were investigated to evaluate the dependence of the network on SiO loadings. Fourier transform infrared spectroscopy and thermogravimetric analysis indicated that hydroxyl groups on SiO surfaces and PLA chain-ends reacted during melt processing. The resulting grafted SiO and entangled PLA chains formed a dense network, which hindered the diffusion of oxygen and volatile decomposition products. Furthermore, the improvement in thermal stability resulted from the restraining effect on the mobility of active hydroxyl end-groups, so that some related thermal decomposition reactions were inhibited, which was confirmed from gel permeation chromatography measurements. Copyright © 2010 Society of Chemical Industry The hydroxyl groups on SiO surfaces and poly(-lactide) (PLA) chains reacted during melt processing, forming a dense network to improve the thermal stability of the PLA matrix. [ABSTRACT FROM AUTHOR]

Poly(ɛ‐caprolactone) (PCL), a saturated polyester, derived from ring‐opening polymerization of ɛ‐caprolactone, was chemically crosslinked with various amounts of benzoyl peroxide (BPO) by a two‐step method by first evenly dispersing the BPO into the PCL matrix and then crosslinking at elevated temperature. The gel fraction increased with an increase in BPO content. The modified Charlesby–Pinner equation was used to calculate the ratio of chain scission and crosslinking. The results showed that both scission and crosslinking occurred, and that crosslinking predominated over scission. The number‐average molecular weight between the crosslinks determined by the rubber elasticity theory using the hot set test showed a decrease with increasing BPO content. The melting temperature and crystallinity decreased with an increase in BPO content, and the crystallization temperature increased after crosslinking. Dynamic mechanical analysis results showed a decrease in the glass transition temperature as a result of chemical crosslinking of PCL. This was explained by the observed reduction in crystallinity and the increase in free volume due to restrictions in chain packing. Moreover, Young's modulus and elongation at break generally decreased with an increase in BPO content, but the tensile strength first increased with BPO content up to 1.0 wt%, reached a maximum, and then decreased. Copyright © 2007 Society of Chemical Industry [ABSTRACT FROM AUTHOR]