Poly (Lactic Acid)/Ground Tire Rubber Blends Using Peroxide Vulcanization

Abstract

Poly (Lactic Acid) (PLA)/Ground Tire Rubber (GTR) blends using Dicumyl peroxide (DCP) as a crosslinking agent were prepared with the following aims: propose a new route to recycle wastes rubber from the automotive industry and improve the toughness and impact strength of the inherently brittle bio-based PLA. The GTR were subjected to two types of grinding process (cryo- and dry ambient grinding). Swelling measurements revealed the grinding to be associated with a mechanical damage of the rubber chains, independently on the type of grinding or on the GTR size (from <400 µm to <63 µm). Moreover, the finest GTR contains the largest amount of reinforcing elements (carbon black, clay) that can be advantageously used in PLA/GTR blends. Indeed, the use of the finest cryo-grinded GTR in the presence of DCP showed the least decrease of the tensile strength (−30%); maintenance of the tensile modulus and the largest improvement of the strain at break (+80%), energy at break (+60%) and impact strength (+90%) as compared to the neat PLA. The results were attributed to the good dispersion of both fine GTR and clay particles into the PLA matrix. Moreover, a possible re-crosslinking of the GTR particles and/or co-crosslinking at PLA/GTR interface in presence of DCP is expected to contribute to such improved ductility and impact strength.

Dynamically vulcanized polylactic acid/natural rubber/waste rubber blends: Effect of the crosslinking agent on the morphology and tensile properties

“…The elastic modulus (Figure 7a), that derives from the stiffness of both rubbery phase and glassy PLA phase, is found in the range 0.5–1 GPa, that is expectedly lower that the one of the neat PLA (3.3 MPa 21 ). The elastic modulus in the vulcanized blends show an optimum at DCP contents of 3–3.75 wt% that is interestingly correlated with the minimum swelling ratio (Figure 3).…”

“…The ultimate tensile strength in both binary and ternary blends is found between 7 and 17 MPa (Figure 8a), that is expectedly significantly lower as compared to the one of the neat PLA (55 MPa 21 ). The effect of DCP on the ultimate tensile strength follows similar trend as compared to the one of elastic modulus confirming the beneficial effect of DCP on tensile properties for DCP contents of 3–3.75 wt%.…”

“…19,20 Another solution is the use of dynamic vulcanization to enhance the compatibility between PLA and wastes rubber, with a 1-fold increase of the impact strength of the resulting vulcanized PLA/GTR blend as compared to the unvulcanized PLA/GTR. 21 However, these blends show drop in the properties at wastes content at and above 30 wt%, due to wastes particle aggregation. Dynamical vulcanization of PLA/GTR blends is hence promising toughening strategy but associated with a limited amount of recycled material.…”

Temperature Dependent Mechanical Properties of Natural and Synthetic Rubber in Practical Structures

“…During vulcanizing increases the secondary cross linking reaction which initiate to cracks. Bearing pad rubber is usually cured with oxide of zinc, magnesium and lead for improving the quality of rubber [29,30]. From the figure it can be seen that the spread of filler is evenly distributed, due to the good interaction between the filler and rubber.…”

Mechanochemical Treatment in High-Shear Thermokinetic Mixer as an Alternative for Tire Recycling

“…Other approaches include the use of GTR in polymer blends. These mixtures are prepared with thermoplastics such as polyethylene (PE), polypropylene (PP), ethylene-vinyl acetate copolymer (EVA) [ 3 ], and polylactic acid (PLA) [ 4 ]. This approach allows for better-quality blends when devulcanization occurs [ 5 ].…”