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This study concerns the preparation of ecocomposites based on natural fibers coming from wood and subproducts (rice husks) and products (kenaf) of annually grown plants. The matrices used were of two types: a biopolymer (PLA) and a petroleum-derived polymer (HDPE). Results showed that natural fibers markedly increase the tensile and flexural properties of both polymers by extending the field of application of these materials with less use of nonrenewable resources. The properties obtained are comparable to commercially available fiber-filled composites. Moreover, processing can easily be carried out in one step below a critical fiber volume. Fire and durability performance of the composites can be also improved by adding typical fire retardants and pigments.

Several composites of poly(L‐lactic acid) (PLLA) with natural fibers (kenaf and rice straw) and pigments have been prepared and analyzed. The study of the thermal behavior has shown a rather important nucleation ability of these fillers for the crystallization of the PLLA component in the composites. Thus, the cooling from the melt of pure PLLA at 10°C/min leads to an almost completely amorphous sample, while a high crystallinity (around 60%) is exhibited by the sample PLLA and rice straw (PLLA‐RS)‐yellow under those conditions. The analysis of the isothermal crystallization from the melt indicates that a maximum rate of crystallization is obtained for all the samples at around 105°C, although the rate is three times faster for samples PLLA and kenaf fiber (PLLA‐KF), PLLA‐KF‐red, and PLLA‐RS, in comparison with pure PLLA. The rate is increased by another factor of three for sample PLLA‐RS‐yellow. The analysis of the melting temperatures and crystallinities as a function of the crystallization temperature shows that there is a break at around 115°C, which seems to be related to the formation of ordered crystals at higher temperatures and disordered ones at lower temperatures. Besides, the natural fibers are environmentally friendly and nonexpensive materials, and the higher crystallization rates of the composites will result in shorter production cycles of end‐use articles. POLYM. COMPOS., 2010. © 2009 Society of Plastics Engineers

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Over the last decade the intense activity of the building sector has generated large quantities of construction and demolition waste (CDW). In particular, in Europe around 890 million tons of CDW is generated every year; however, only 50% of them are recycled. In Spain, over the last years 40 millions of tons of construction and demolition waste have been generated. On the other hand, since the implementation of the Technical Building Code regulation the use of mineral wools as building insulation materials has become a widespread solution in both rehabilitation and new construction works, and because of that, this kind of insulation waste is increasing. This research analyzes the potential of a new composite (gypsum and fiber waste) including several mineral wools waste into a plaster matrix. For this purpose, an experimental plan, characterizing the physical and mechanical behaviour as well as the Shore C hardness of the new composite, was elaborated fulfilling UNE Standards.