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A preliminary study on the use of wood and plastic wastes generated in Merida, Mexico to assess their potential for the development of building materials is reported. Composites based on recycled, high-density polyethylene (R-HDPE) loaded with wood particles were prepared. The R-HDPE was collected from Merida's Separation Plant, where it was sorted from other residues, either organic or inorganic. Composites based on virgin, high-density polyethylene (V-HDPE) were also prepared to assess the effect of the R-HDPE on the composite's mechanical properties. The wood came from the trims of different varieties of the city's trees that are periodically pruned as part of the cleaning and urbanising programmes implemented by the City Council. A batch of this material was selected at random to incorporate into both the R-HDPE and V-HDPE. Different wood particle sizes were experimented with to obtain extruded composites with contents of 50% and 60% by weight of wood that were characterized under tension and impact. Flat wood-plastic extrudates with reasonable good appearance were also produced at the laboratory level as a first step to find an adequate route to scale-up the process to a pilot level to evaluate the feasibility of producing alternative building materials.

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Electrical monitoring of strain and damage in multiscale hierarchical composites comprising unidirectional aramid fibers modified by multiwall carbon nanotubes and polypropylene as matrix is investigated. The key factor for electrical self-sensing in these thermoplastic composites is the formation of a multiwall carbon nanotube network, which is achieved by using two material architectures. In the first architecture, the multiwall carbon nanotubes are dispersed within the polypropylene matrix, while aramid fibers remain unmodified. The second architecture uses also multiwall carbon nanotube-modified polypropylene matrix, but the aramid fibers are also modified by depositing multiwall carbon nanotubes. Under tensile loading, the electrical response is nonlinear with strain ( ε), and the piezoresistive sensitivity was quantified by gage factors corresponding to low ( ε < 0.25%) and high ( ε > 0.3%) strain regimes. Such gage factors were 4.83 (for ε < 0.25%) and 13.2 (for ε > 0.3%) for composites containing multiwall carbon nanotubes only in the polypropylene matrix. The composites containing multiwall carbon nanotubes in the matrix and fibers presented higher piezoresistive sensitivity, with average gage factors of 9.24 ( ε < 0.25%) and 14.0 ( ε > 0.3%). The higher sensitivity to strain and damage for a specific material architecture was also evident during cyclic and constant strain loading programs and is attributed to the preferential localization of multiwall carbon nanotubes in the hierarchical composite.