CHAPTER 2: Surface Treatment of Rubber Waste

This chapter deals with the study of different approaches to improve the compatibility of waste rubber with polymeric matrixes of high density polyethylene (HDPE) by using surface treatments to increase adhesion. Different surface treatments such as etching with sulphuric and nitric acids, the use of a silane as a coupling agent and chlorination with trichloroisocyanuric acid (TCI) have been applied. The modification of waste rubber by grafting has also been studied. This process is based on the dynamical crosslinking of ethylene propylene diene monomer (EPDM) with peroxides. The mechanical properties of the resulting materials were studied and compared. The chemical modifications that occurred on the waste rubber were monitored by Fourier-transform infrared spectroscopy (FTIR). The behaviour of the materials at the fracture was assessed by means of scanning electron microscopy (SEM). The results of treated and untreated samples were compared with neat HDPE. Waste rubber, added to HDPE in small quantities, acts as a filler, improving the stiffness and providing a more brittle behaviour. Treatment with TCI gave poor mechanical properties obtaining lower values than neat HDPE in some cases, and in general worst properties than the other methods. The most interesting mechanical properties have been obtained by a grafting process based on EPDM dynamically crosslinked with a mixture of peroxides T-311 and dicumyl peroxide (DCP).