Thermoplastic elastomers based on recycled high-density polyethylene/ground tire rubber/ethylene vinyl acetate: Effect of ground tire rubber regeneration on morphological and mechanical properties

Cross-Linking, Morphology, and Physico-Mechanical Properties of GTR/SBS Blends: Dicumyl Peroxide vs. Sulfur System

In this work, ground tire rubber and styrene-butadiene block copolymer (GTR/SBS) blends at the ratio of 50/50 wt%, with the application of four different SBS copolymer grades (linear and radial) and two types of cross-linking agent (a sulfur-based system and dicumyl peroxide), were prepared by melt compounding. The rheological and cross-linking behavior, physico-mechanical parameters (i.e., tensile properties, abrasion resistance, hardness, swelling degree, and density), thermal stability, and morphology of the prepared materials were characterized. The results showed that the selected SBS copolymers improved the processability of the GTR/SBS blends without any noticeable effects on their cross-linking behavior-which, in turn, was influenced by the type of cross-linking agent used. On the other hand, it was observed that the tensile strength, elongation at break, and abrasion resistance of the GTR/SBS blends cured with the sulfur system (6.1-8.4 MPa, 184-283%, and 235-303 mm3, respectively) were better than those cross-linked by dicumyl peroxide (4.0-7.8 MPa, 80-165%, and 351-414 mm3, respectively). Furthermore, it was found that the SBS copolymers improved the thermal stability of GTR, while the increasing viscosity of the used SBS copolymer also enhanced the interfacial adhesion between the GTR and SBS copolymers, as confirmed by microstructure evaluation.

RECYCLING, MODIFICATION AND DEVELOPMENT OF NEW COMPOSITE MATERIALS BASED ON POLYMER WASTE

The review article considers the current problem of environmental pollution with polymer waste. To solve one of the highest priority tasks, their recycling is considered, which is advisable from an economic, practical and scientific point of view. An assessment of the resources of secondary polymeric raw materials was made. The main ways of utilization of polymeric waste are given. The features of polymer waste recycling methods are determined. The issues of modification of polymer wastes are considered and the main methods of compatibilization of polymer mixtures are shown. Particular attention is paid to the methods and mechanisms of compatibilization of polymer composites based on recycled thermoplastics and crumb rubber from waste tires as a means of obtaining new composite polymer materials with valuable performance properties. The dependence of the properties of polymer composites on the filler concentration, particle size and shape, surface treatment methods, type and content, modifying additives and compatibilizers is shown. The creation of polymer composites based on secondary polymers and fillers of various nature contributes to the solution of social and economic problems of polymer waste.

Sustainable Reuse of Waste Tire Textile Fibers (WTTF) as Reinforcements

Waste tire textile fibers (WTTF), as a by-product (10-15% by weight of tires) of end-of-life tires (ELT) mechanical recycling (grinding), are classified as hazardous wastes and traditionally burnt (thermal recycling) or buried (landfilling), leading to several environmental and ecological issues. Thus, WTTF still represent an important challenge in today's material recycling streams. It is vital to provide practical and economical solutions to convert WTTF into a source of inexpensive and valuable raw materials. In recent years, tire textile fibers have attracted significant attention to be used as a promising substitute to the commonly used natural/synthetic reinforcement fibers in geotechnical engineering applications, construction/civil structures, insulation materials, and polymer composites. However, the results available in the literature are limited, and practical aspects such as fiber contamination (~65% rubber particles) remain unsolved, limiting WTTF as an inexpensive reinforcement. This study provides a comprehensive review on WTTF treatments to separate rubber and impurities and discusses potential applications in expansive soils, cement and concrete, asphalt mixtures, rubber aerogels and polymer composites.

Recycled HDPE/Natural Fiber Composites Modified with Waste Tire Rubber: A Comparison between Injection and Compression Molding

With the objective of turning wastes into added-value materials, sustainable and fully recycled wood-plastic composites were reinforced by waste tire rubber particles to show balanced properties and potentially low-cost materials. Recycled high density polyethylene (rHDPE) was compounded (melt extrusion) with flax fiber (FF) and waste regenerated tire rubber (RR) to investigate the effect of mixing ratio, coupling agent (maleated polyethylene, MAPE) and molding process (injection and compression molding) on the properties of hybrid composites. In particular, a complete set of characterization was performed including thermal stability, phase morphology and mechanical properties in terms of tension, flexion and impact, as well as hardness and density. Adding 40 wt.% of flax fibers (FF) increased the tensile (17%) and flexural (15%) modulus of rHDPE, while the impact strength decreased by 58%. Substitution of FF by waste rubber particles improved by 75% the impact strength due to the elasticity and energy absorption of the rubber phase. The effects of impact modification were more pronounced for rHDPE/(FF/RR) compatibilized with MAPE (10 wt.%) due to highly improved interfacial adhesion and compatibility. The results also suggest that, for a fixed hybrid composition (FF/RR, 25/55 wt.%), the injection molded composites have a more homogenous morphology with a uniform distribution of well embedded reinforcements in the matrix. This better morphology produced higher tensile strain at break (12%) and impact strength (9%) compared to compression molded samples.