Sustainable valorization of recycled low-density polyethylene and cocoa biomass for composite production

Mining waste and coconut fibers as an eco-friendly reinforcement for the production of concrete blocks

Using mineral and agro-industrial wastes associated with the cement matrix can add value and guarantee suitable properties for reinforced composites. This research aimed to evaluate the effect of the incorporation of quartzite and coconut fibers on masonry blocks' physical, mechanical, and thermal properties. Quartzite was evaluated replacing 0%, 25%, 50%, 75%, and 100% of the sand, whereas the coconut fibers were added in a proportion of 2.5% of the volume of gravel. Quartzite residues were analyzed regarding their granulometry, chemical composition, and pozzolanicity. The block initial formulation (control) was: 8.2% cement, 45.9% sand, and 45.9% gravel. The cement was cured at room temperature for 28 days. Subsequently, the blocks were subjected to the characterization of physical, mechanical, and thermal properties. Coconut fibers presented a low percentage of extractives, with a low inhibition index (1.93%), reducing their effect on cement hardening. The increase in the content of quartzite incorporated provided a reduction in bulk density and an increase in porosity (from 11.7 to 16.0%) and water absorption after 24 h (from 7.0 to 8.5%). The compressive strength was reduced from 50% with the insertion of the quartzite. The quartzite and coconut fibers reduced the concrete's thermal conductivity, providing essential reflections for the performance of the blocks in terms of thermal comfort in built environments. Further, incorporating these materials provided the potential to obtain blocks with characteristics of resistance and offering possible thermal comfort, besides contributing as an option for a destination for these mineral and agro-industrial wastes.

Synthesis of Poly(Hexamethylene Succinate-Co-Ethylene Succinate) Copolymers With Different Physical Properties and Enzymatic Hydrolyzability by Regulating the Ratio of Monomer

Poly(hexylene succinate) (PHS), poly(ethylene succinate) (PES), and their random copolyesters, poly(hexylene succinate-co-ethylene succinate) ((P(HS-co-ES)), were synthesized by melting polycondensation. Simply varying the ratios of HS/ES afforded control over the copolymer crystallinity, thermal and mechanical properties, wettability, and enzymatic hydrolyzability as shown by X-ray diffraction (XRD), differential scanning calorimetry (DSC), tensile tests, and water contact angle (WCA) measurements. The enzymatic hydrolysis rates of all prepared copolyesters were higher than those of the corresponding homopolyesters. The hydrolysis rates were affected by crystallinity, melting temperature, and hydrophobicity of the copolyesters, and therefore, the degradation rates could be tuned along with the ES content. The library of copolymers prepared here with tunable degradation rates, ranging from HS-enriched to ES-enriched copolyesters, is promising for a variety of different applications. The P(HS-co-ES51) copolyester that did not fully degrade is particularly promising for use in long-term storage applications, whereas P(HS-co-ES13) and P(HS-co-ES76) that rapidly degrade are good for use in very short-term applications.

Chemical Treatment of Bio-Derived Industrial Waste Filled Recycled Low-Density Polyethylene: A Comparative Evaluation

The search for renewable alternatives for petroleum products that can be used in industrial applications is increasing. Each year, several tons of bio-derived industrial waste is produced and most of it is burned or placed in landfills. Olive pits (OP) have unique characteristics such as abundance, renewability, and biodegradability, which can be utilized to develop new types of biocomposites. One of the most promising uses of OP is that they can reinforce the mechanical properties of polymeric biocomposites. This study describes the preparation of recycled low-density polyethylene (rLDPE) that is filled with OP flour (10, 20, 30, and 40 wt.%) using a twin-screw extruder. The effects of the chemical treatment of the OP surface (sodium hydroxide (NaOH) and dimethyl sulfoxide (DMSO)) on the bio-filler/polymer compatibility along with the produced composite's chemical, physical, mechanical, and thermal properties have been explored. Overall, the reinforced composites that were obtained with alkali-treated OP have better biocomposite properties. This indicates an improved compatibility between the bio-filler and matrix. The results are promising in terms of using OP flour in developing green composites.