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.

This study evaluates the effect of recycled thermoplastic polyurethane (RTPU) on the Izod impact resistance of polypropylene (PP) compounds with 50% coconut fibers arranged randomly. The Izod impact resistance was compared to the performance of a commercial coupling agent (CCA) of maleic anhydride grafted PP copolymer (MAPP). The PP compounds were made with 0, 2.5, and 5% by weight of RTPU or CCA, and with 50% of short or long coconut fibers, in the form of plates molded by thermo-compression, where the plastic components were previously extruded in the form of filaments. The morphology of the resulting materials was studied by scanning electron microscopy (SEM). The functional groups and their possible interactions present were determined by Fourier transform infrared spectroscopy (FTIR). Furthermore, the interfacial shear strength between the polymeric matrix and the coconut fiber was determined. The results showed a higher Izod impact resistance and a higher adhesion between long coconut fiber and PP when they contain 5% RTPU. This is explained by the higher interfacial shear strength between them given by the chemical and/or physical interaction between functional groups such as the lignin of coconut fibers and the isocyanate groups of RTPU, which in turn determined the shortest critical length of coconut fiber. The impact resistance values ranged from 19.8 to 24.4 J/m for mixtures of PP with short coconut fibers and 39.9–71.7 J/m for PP with long coconut fibers.

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This work presents a study on the use of wood and plastic wastes generated in abundance in Merida, Mexico, to help to reduce them in order to mitigate environmental deterioration. The use of these wastes is proposed to obtain a low-cost building material. So, the escalation process (i.e., extrusion) at the pilot level to obtain a prototype of a wood–plastic composite (WPC) corrugated sheet to evaluate the technical feasibility to make a low-cost product is reported. A corrugated sheet with recycled high-density polyethylene (R-HDPE) was produced. The R-HDPE was collected from Merida’s Separation Plant. The wood came from the trimmings of different varieties of trees and shrubs that are periodically pruned. WPC sheets with virgin HDPE were prepared to assess its effect on the materials’ mechanical performance. The wood/HDPE weight ratio was 40/60. The performance of the WPC sheets was compared with that of commercial products with similar characteristics, namely acrylic and polyester sheets reinforced with fibreglass, and black asphalt-saturated cardboard sheets. Thus, the effect of natural weathering on the maximum tensile tearing force and on the maximum flexural load of the different types of sheets was evaluated. Although the mechanical performance of the WPC sheets was lower than that of the acrylic and polyacrylic sheets, their performance was much better than that of the cheap black asphalt-saturated cardboard sheets. So, they are a good option to be used as low-cost temporary roofing.

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A scanning experimental design that uses Taguchi methodology allowed to apply an orthogonal type model L12 to determine the optimal formulation and process variables—in two levels—to obtain extruded polyethylene (PE) composites with Tetra Pak multilayer cartons. The variables of the first type were the following: types of PE and mixtures of ethylenic copolymer processing aids; particle size; content of milled Tetra Pak containers, zinc oxide lubricant, mixtures of ethylenic copolymer processing aids, calcium carbonate, stearic acid, and titanate coupling agent. The variables of the second type were the speed and temperature profile of the extruder. This methodology applied two criteria for the evaluation of results, the separate analysis and the evaluation of multiple criteria of response parameters. The results showed the most important independent variables that affected the response parameters, being the extrusion speed with 49.8%, the type of PE with 18.4%, and the mixture of ethylenic copolymer processing aids with 8.1%. The optimal run showed the expected favorable results, such as plasticity with 89.6 cm/cm, mass flow with 0.80 kg/h, density with 1.11 kg/m3, torque with 574 mg, molten mass pressure of 111 lbf/in2, temperature of fusion of 149°C, impact resistance of 32 J/m, tensile strength of 11 MPa, and flexural modulus of 314 MPa.

Recycling printed polypropylene (PP) labels and printed polyolefins (PO) caps as a chemical foaming agent to produce foam products is studied. An experimental Taguchi L16 design with seven experimental variables involved is used: talc content and screw angular velocity, at four experimental levels; extrusion temperature profile and extruded formulations, at three levels; and, type of label washing process, the use of metal mesh and the type of label drying process, at two levels. As control variables, the morphology of the cells and the density of the foamed products are utilized. The labels/caps mixture was composed of 21% printed PP labels and 79% printed polyolefin caps. Part of the pigments from the ink labels and some polar groups of low-molecular-weight materials present in the molten polymer were partially decomposed at the PP processing temperatures, which contributes to the cell formation and growth of the extruded foams. The labels/caps mixture generated large ellipsoidal and elongated cells (740 µm) oriented in the extrusion direction because of the presence of high density polyethylene (HDPE) and EVA in the recycled PP caps and labels. The experimental factors that influenced the foam density were the screw angular velocity and temperature, and the cell morphology depended on the matrix crystallinity and melt strength.

This study evaluates the effect of incorporating chemical agents with green polyethylene terephthalate (PET) bottles on extrudate color change and other properties. First, the best type of chemical agent that decolorizes recycled green PET bottles (RGPB) with good processability was determined. RGPB-chemical agent mixtures were evaluated, reducing, photoinitiator, or oxidant, where the best one turned out to be the oxidizing agent, a dicumyl peroxide. Then new mixtures of RGPB-oxidizing agent, dicumyl or benzoyl, were made in a reactive extrusion process employing a drying hopper to avoid hydrolytic degradation. The intrinsic viscosity, crystallinity, and color change of extrudates were determined. It was determined by SEM with EDS that the dye is possibly a chlorinated copper phthalocyanine. The final results show an increase in the intrinsic viscosity of the PET handling dicumyl peroxide, a partial whitening of the extrudates, and an increase in the crystallinity of the PET, which contributed to a decrease the hue and saturation of the green color of RGPB. Where the dicumyl peroxide present in mixtures with RGPB interacts with chlorinated copper phthalocyanine to produce phthalamide or phthalic acid, which are white.