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Composite materials were prepared by mixing fly ash obtained from biomass combustion as filler and isotactic polypropylene (PP) as matrix. Three silane‐type coupling agents mainly differing in the size of their functional groups were used to improve the compatibility between both components. Uniaxial tensile tests showed that the incorporation of untreated ash into PP led to stiffer but also more brittle and weaker materials, as Young's modulus significantly increased and tensile strength and elongation at break decreased. Furthermore, an enhancement in storage and loss moduli as well as in composite viscosity was observed with the addition of fly ash. Hardness tests and thermal and fracture surface analyzes revealed tensile test results similar to those mentioned earlier. In summary, after analyzing the effects of the three silanes on mechanical, thermal, morphological, and rheological properties, the silane containing the vinyl functional group (XL10) was selected as the most appropriate for the PP/ash composites investigated. POLYM. COMPOS., 31:1722–1730, 2010. © 2010 Society of Plastics Engineers.

ABSTRACT:The properties of two polyethylenes [a highdensity polyethylene (HDPE) and a low-density polyethylene (LDPE)] were studied after several extrusion cycles. To reduce the degradation effects during the reprocessing, a mixture of two stabilizers was added to the formulations. The predominant degradation mechanism was chain scission for the HDPE and chain branching and crosslinking for the LDPE. For both polyethylenes the FTIR spectra exhibited a growth in the number of carbonyl groups as a function of the number of extrusion cycles. Their tensile properties were degraded with the reprocessing but both polyethylenes maintained their nearly constant thermal behavior and crystallinity. The addition of a primary phenolic antioxidant and a secondary phosphite antioxidant preserved the melt behavior of virgin materials after the reprocessing and reduced the degradation effects. From the tensile tests, the efficiency of the antioxidants in the LDPE was very high and, after the reprocessing, the material retained the mechanical properties of virgin LDPE. The efficiency of the antioxidants for the HDPE was not significant.

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