Evaluation of Eco-Friendly Hemp-Fiber-Reinforced Recycled HDPE Composites

Abstract

The exploitation of natural fibers to reinforce polymers is a promising practice. Thus, biocomposites have gained increased attention in automotive, construction, and agricultural sectors, among others. The present work reports the reinforcement of recycled high-density polyethylene (r-HDPE) with hemp fibers to afford composite materials as sustainable analogues to conventional wood/plastic composite (WPC) products. HDPE bottles (postconsumer waste) were used as r-HDPE and further reinforced by the addition of hemp fibers. For the synthetic part, thirteen composite materials with different filler concentrations (10–75% wt. in hemp fibers) using either Joncryl or polyethylene-grafted maleic anhydride (PE-g-MA) as compatibilizers were prepared via melt mixing. Materials with good integrity were obtained with a fiber load as high as 75% wt. The structural, thermal, mechanical, and antioxidant properties of the r-HDPE/hemp composites were evaluated using multiple complementary characterization techniques. Stereoscopic microscope images demonstrated the satisfactory dispersion of the hemp fibers into the polymeric matrix, while scanning electron microscopy microphotographs revealed an improved adhesion between the filler and the polymeric matrix in the presence of compatibilizers. The incorporation of hemp fibers contributed to the improvement of the elastic modulus of the composites (almost up to threefold increase). The results showed that as the hemp fiber content increased, the antioxidant properties as well as the degradability of the composites increased. It is noteworthy that composites containing 75% wt. hemp fibers neutralized 80% of 2,2-diphenyil-1-picrylhydrazyl radicals within 45 min (DPPH assay). In conclusion, the present research work demonstrates that thermally recycled HDPE reinforced with biomass fibers received from agricultural waste is a valid alternative for the preparation of commodity products with an eco-friendly character compared to conventional wood/plastic composites.

Improvement in the Thermomechanical Properties and Adhesion of Wood Fibers to the Polyamide 6 Matrix by Sequential Ball Milling Technique

“…Notably, composites reinforced with 30 wt % PFs exhibited a remarkable 160% increase in Young’s modulus compared to PA6 matrices. Unlike numerous studies in the existing literature, ,− , this exceptional tensile characteristic was achieved without resorting to expensive or laborious chemical modifications of PFs. The notable improvements were primarily observed in PA6-based composites, supporting the favorable compatibility of the pulp fibers with PA6 when prepared by using the premixing ball milling method.…”

“…Furthermore, the weight loss in this phase corresponds to the different reinforcement loads of the fibers. Other authors have also reported these ternary degradation profiles for PA6-based composites loaded with other cellulose-based fibers. , When incorporating high quantities of PFs, the onset thermal degradation temperature drops shown in the specific 30 wt % case cause a temperature drop from 387 to 344 °C, due to the conversion of cellulose into acetaldehyde, propenal, methanol, and acetic acid . Espinach et al explored the thermal properties of polymer composites that were reinforced with bleached kraft softwood.…”

“…One approach to mitigate the issue of thermal degradation is to use chemically modified pulp fibers to improve their dispersion and thermal stability . For example, cellulose fibers can be treated with cross-linking agents or other chemical treatments to improve their thermal stability. ,− However, there are potential negative effects that must be carefully considered in chemical treatment such as reduced fiber strength, increased production costs and processing steps, environmental impact, and reduced biodegradability . Another approach involves incorporating pulp fibers into the high-melting-temperature matrix using a melt compounding process with lower temperatures and shorter processing times than traditional melt processing, which minimizes the thermal degradation of the pulp fibers. ,, However, achieving good dispersion of the fibers within the polymer matrix is still problematic with this method.…”

Use of Post-Consumer Plastics in the Production of Wood-Plastic Composites for Building Components: A Systematic Review

“…Analyzing the studies in the systematic review found that different types of postconsumer plastics were used as waste in the evaluated experiments. Among the most prevalent typologies, polypropylene (PP) was highlighted in five studies [14][15][16]19,22], and high-density polyethylene (HDPE) in another five studies [16,[19][20][21][22]. Additionally, polyethylene terephthalate (PET) was used in a specific study [24].…”

“…Additionally, plant-based fillers, such as crushed wood waste, pine nut shells, corn husks, hemp fibers, and wood chips, were incorporated to improve mechanical properties and reduce reliance on virgin materials. and high-density polyethylene (HDPE) in another five studies [16,[19][20][21][22]. Addi polyethylene terephthalate (PET) was used in a specific study [24].…”