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Nanoscale reinforcements have strong promise in designing ecofriendly green bionanocomposites by combining (natural/bio) fibers with biodegradable polymers. However, the poor fire resistance of these organic materials restricts their applications in some industrial fields such as the textile, electric and electronics industries. Indeed, the textile industry is probably the first ones to point out the durability of flame retardancy as a major issue. In this paper, fibers of poly(lactic acid)/cellulose nanowhiskers (PLA/CNW), and poly(lactic acid)/cellulose microcrystalline (PLA/MCC) were prepared by melt spinning at filler content of 1 and 3 wt%, in the presence of 7 wt% of PLA-grafted-maleic anhydride (PLA-g-MA) used as the compatibilizer. The flame retardancy properties of the samples were investigated by Pyrolysis Combustion Flow Calorimeter (PCFC) test. The results showed that the addition of MCC and CNW to PLA fibers led to the formation of a protective char layer, which protects the bionanocomposite sample from the action of heat flux and flame during combustion. Furthermore, the incorporation of 1 wt% of CNW to PLA resulted in better flame retardancy properties than MCC due to better morphology as well as dispersion of CNW in the polymer. [ABSTRACT FROM AUTHOR]

The objective of the work was to investigate the effects of gamma irradiation at absorbed dose of 75 kGy on the chemical structure and crystallinity of PHBV/PLA blend (50/50 w/w) without and with Cloisite 30B (C30B) incorporated at 3 wt %. IRTF spectra showed that gamma irradiation induced changes in the chemical structure of PHBV/PLA blends due to oxidation reactions involving the transformation of ester groups to hydroperoxides. However, the addition of C30B in the polymer blend had no influence on the nature of the degradation process. GPC data showed that the value of the average number of chain scission (nt) of irradiated PHBV/PLA/C30B sample is lower than that of the virgin blend highlighting the role of C30B as a retardant of the chain scission mechanism. WAXS analysis indicated an increase in the crystallinity of all irradiated samples at 75 kGy. [ABSTRACT FROM AUTHOR]

The effects of unmodified vermiculite (UMVC) clay on the photooxidation of polyamide 11 (PA11) were investigated by accelerated UV test up to 600 h. The clay was incorporated to the polymer at a content ratio of 5 wt. %. The film samples were prepared by melt compounding using cast extrusion process. The study showed that accelerated photo-oxidation induced changes in the chemical structure of both PA11 and PA11 nanocomposite resulting in the formation of imides and carboxylic acids as the main carbonyl products. Furthermore, the carbonyl index increased linearly in the first 360 h of exposure indicating a fast oxidation process before decreasing. The stability of the irradiated samples was also evaluated by the onset oxidation temperature (OOT) determined by DSC and the results corroborated well those obtained by FTIR spectroscopy. [ABSTRACT FROM AUTHOR]

Dimer fatty acid polyamide nanocomposites based on flake- or needle-shaped nanoparticles were prepared via melt compounding. Transmission electron microscopy showed the presence of both individually dispersed particles and particle agglomerates in the polymer matrix. Dynamic mechanical analysis suggests that three stiffening mechanisms were operating. The reinforcing effect of the high stiffness inorganic filler particles is the primary contributor. Together with the chain confinement effect, that expresses itself in an apparent increase in the glass transition temperature, this provided an adequate rationalization of the stiffness variation below Tg. However, an additional stiffening effect is indicated at temperatures above Tg. The mechanism may involve dynamic network formation based on fluctuating hydrogen bonding interactions between the polymer chains and the filler particles. [ABSTRACT FROM AUTHOR]