Formulations for thermoplastic vulcanizates based on high density polyethylene, ethylene-propylene-diene monomer, and ground tyre rubber

Abstract

Thermoplastic vulcanizates (TPVs) are a specific group of the so called thermoplastic elastomers. The main characteristic is the existence of a crosslinked rubber phase obtained by dynamic vulcanization in the presence of the thermoplastic matrix. This article studies TPVs based on ground tyre rubber (GTR), high-density polyethylene, and ethylene propylene diene monomer rubber. Vulcanization is performed by a new peroxide developed to resist high temperatures and an standard one. The aim of this study is optimize the formulation in order to include GTR, while maintaining a good balance of properties in the final TPV material. The use of GTR would improve the possibilities of recovering tyre waste. A detailed study regarding the influence of each component in the final mechanical properties has been carried out. The swelling properties, ATR infrared spectroscopy, TGA, and DSC analysis indicated a high degree of crosslink and good adhesion between the matrix and the rubber phase. Morphology of the composites was assessed by scanning electron microscopy. A composite containing a combination of peroxides and 40/30/30 of HDPE, EPDM, and GTR was found to show a good balance of characteristics regarding mechanical properties, crosslinking, and adhesion between phases.

Relationship among Vulcanization, Mechanical Properties and Morphology of Blends Containing Recycled EPDM

“…The literature has shown [41] that the lack of adhesion among phases in blends containing recycled elastomers is due to the large particles of elastomers, their superficial characteristics, and the structure of the cross-linkings, which hinder its absorption by molecules of the matrix as the use of only ground elastomer in blends makes the processing a difficult step [42], as observed in this work.…”

Improving the properties of reclaimed waste tire rubber by blending with poly(ethylene‐co‐vinyl acetate) and electron beam irradiation

“…Also, studies utilizing GTR in thermoplastic elastomer observed the encapsulation of GTR by the rubber component and observed good mechanical properties (Naskar et al, 2001, Cañavate et al, 2011, Abou Zeid et al, 2008, Li et al, 2003b. In this study, low molecular weight liquid styrene butadiene rubber (LR) was used instead of a high molecular weight rubber, to improve the adhesion between RTR and EVA.…”

Blends of ground tire rubber devulcanized by microwaves/HDPE - Part B: influence of clay addition

“…Rubber requires a long period to degrade naturally due to its cross-linked structure and the presence of stabilizers and other additives [1,2] , what consequently reduce its processability [3,4] . Many efforts have been made regarding the preparation and characterization of polymer blends containing GTR and various thermoplastics, as a recycling alternative [5,6] . 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. In the production of thermoplastic vulcanized blends (TPVs) containing recycled rubbers, the addition of a virgin rubber or the promotion of the rubber devulcanization (at least partial) are pre-requisites to obtain resultant good mechanical properties [12] .…”