Partial replacement of NR by GTR in thermoplastic elastomer based on LLDPE/NR through using reactive blending: Its effects on morphology, rheological, and mechanical properties
Abstract:Attempts have been made to use different amount of ground tire rubber (GTR) powder as a partial substitute for natural rubber (NR) in thermoplastic elastomer based on linear low-density polyethylene (LLDPE, 60 wt%) and NR (40wt%). Maleic anhydride (MA) and dicumyl peroxide (DCP) were used, during melt mixing of the compound, to modify GTR and vulcanize the rubber phases of the blends. Morphology of the blends was studied by scanning electron microscopy and rheological behavior investigated through rheomechanic… Show more
“…29 Improved compatibility between RR and compatibilizer is related to chemical bonds formed between the unsaturated C = C bonds on the rubber surface and the maleic anhydride group of MAPE. 41,42 Contrary to R45F and R60F, no fiber pull-out is detected in R45F* and R60F*, so RTF are also well embedded in the matrix suggesting more affinity between the components (reduced surface energy), thereby increased failure resistance through effective load transfer can be expected. 22,25 This special morphology is also expected to improve all the mechanical properties, especially the elongation at break and impact strength as described next.Figure 7.Scanning electron microscope micrographs of: (a and b) R45F* and (c and d) R60F* composites at different magnifications.…”
In this work, recycled high density polyethylene (rHDPE) was compounded with regenerated tire rubber (RR) (35–80 wt.%) and reinforced with recycled tire textile fiber (RTF) (20 wt.%) as a first step. The materials were compounded by melt extrusion, injection molded, and characterized in terms of morphological, mechanical, physical, and thermal properties. Although, replacement of the rubber phase with RTF compensated for tensile/flexural moduli losses of rHDPE/RR/RTF blends because of the more rigid nature of fibers increasing the composites stiffness, the impact strength substantially decreased. So, a new approach is proposed for impact modification by adding a blend of maleic anhydride grafted polyethylene (MAPE)/RR (70/30) into a fiber-reinforced rubberized composite. As in this case, a more homogeneous distribution of the fillers was observed due to better compatibility between MAPE, rHDPE, and RR. The tensile properties were improved as the elongation at break increased up to 173% because of better interfacial adhesion. Impact modification of the resulting thermoplastic elastomer (TPE) composites based on rHDPE/(RR/MAPE)/RTF was successfully performed (improved toughness by 60%) via encapsulation of the rubber phase by MAPE forming a thick/soft interphase decreasing interfacial stress concentration slowing down fracture. Finally, the thermal stability of rubberized fiber-reinforced TPE also revealed the positive effect of MAPE addition on molecular entanglements and strong bonding yielding lower weight loss, while the microstructure and crystallinity degree did not significantly change up to 60 wt.% RR/MAPE (70/30).
“…29 Improved compatibility between RR and compatibilizer is related to chemical bonds formed between the unsaturated C = C bonds on the rubber surface and the maleic anhydride group of MAPE. 41,42 Contrary to R45F and R60F, no fiber pull-out is detected in R45F* and R60F*, so RTF are also well embedded in the matrix suggesting more affinity between the components (reduced surface energy), thereby increased failure resistance through effective load transfer can be expected. 22,25 This special morphology is also expected to improve all the mechanical properties, especially the elongation at break and impact strength as described next.Figure 7.Scanning electron microscope micrographs of: (a and b) R45F* and (c and d) R60F* composites at different magnifications.…”
In this work, recycled high density polyethylene (rHDPE) was compounded with regenerated tire rubber (RR) (35–80 wt.%) and reinforced with recycled tire textile fiber (RTF) (20 wt.%) as a first step. The materials were compounded by melt extrusion, injection molded, and characterized in terms of morphological, mechanical, physical, and thermal properties. Although, replacement of the rubber phase with RTF compensated for tensile/flexural moduli losses of rHDPE/RR/RTF blends because of the more rigid nature of fibers increasing the composites stiffness, the impact strength substantially decreased. So, a new approach is proposed for impact modification by adding a blend of maleic anhydride grafted polyethylene (MAPE)/RR (70/30) into a fiber-reinforced rubberized composite. As in this case, a more homogeneous distribution of the fillers was observed due to better compatibility between MAPE, rHDPE, and RR. The tensile properties were improved as the elongation at break increased up to 173% because of better interfacial adhesion. Impact modification of the resulting thermoplastic elastomer (TPE) composites based on rHDPE/(RR/MAPE)/RTF was successfully performed (improved toughness by 60%) via encapsulation of the rubber phase by MAPE forming a thick/soft interphase decreasing interfacial stress concentration slowing down fracture. Finally, the thermal stability of rubberized fiber-reinforced TPE also revealed the positive effect of MAPE addition on molecular entanglements and strong bonding yielding lower weight loss, while the microstructure and crystallinity degree did not significantly change up to 60 wt.% RR/MAPE (70/30).
“…The properties of these materials depend on the concentration of the recycled material, as well as the adhesion between the phases [7,8] . On the other hand, the adhesion between GTR and the polymer matrix is usually very weak as consequence of the three-dimensional structure generated by cross-linkings, in the case of blends in which the GTR is just ground [9][10][11] . Cañavate et al [6] report that the lack of adhesion between phases is a consequence of the large particle size of GTR, superficial characteristics and cross-linked structure, which hamper its adsorption by the thermoplastic matrix molecules.…”
SbstractThe main objective of this work is to study the influence of clay addition on dynamically revulcanized blends of Ground Tire Rubber (GTR)/High Density Polyethylene (HDPE). GTR was previously devulcanized in a system comprised of a conventional microwave oven adapted with a motorized stirring, with a fixed microwave power and at various exposure times. The influence of clay addition on the final properties of the blends was evaluated in terms of mechanical, viscoelastic, thermal and rheological properties, with morphology being also analyzed. The results depict that the clay can modify the rheological behavior of the GTR phase, in addition to the thermal and mechanical properties of some blends.
“…To compatibilize GRPs with the thermoplastic polymer matrix, GRP surface modification has been extensively studied using both reactive and nonreactive compatibilizers. To modify the chemistry or polarity of GRP surface, reagents such as acrylamide, allylamine, maleic anhydride, and others , are often used alongside radiation to promote reaction with the GRP surface; in many cases, dicumyl peroxide is used as a photoinitiator. , Chemically modifying the GRP surface can enhance interfacial adhesion with the polymer matrix, improve particle dispersion, and provide a reactive group for subsequent covalent bonding. , To further increase adhesion between GRPs and the surrounding thermoplastic matrix, a third polymer is often added to the blend as a compatibilizer. Adding copolymers such as methacrylic anhydride-grafted polypropylene or ethylene , and ethylene-1-octene , to TPVs significantly enhances mechanical properties.…”
A simple and cost-effective adhesive-based rubber recycling process was designed as an alternative to devulcanization. Interfacial bonding between vulcanized and virgin rubbers is improved by incorporating adhesives and coating processes during rubber reblending and reducing interfacial defects that cause premature failure. In flat laminates, the bond strength between vulcanized and virgin materials doubles when a vulcanizing fluid and thin adhesive layer are introduced. These components are combined into single-component adhesives (SCAs), which improve bond strength sixfold over no treatment, using half the raw material as the multilayer adhesive. When SCAs are coated onto vulcanized rubber particles prior to reblending, the best rubbers exhibit nearly 50% increases in mechanical strength and toughness vs the untreated control and statistically identical extensibility; all treatments improved mechanical strength. This simple, inexpensive, and scalable process can be implemented with one step beyond standard reblending and curing, providing a promising alternative to devulcanization for polymer recycling.
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