Ground tire rubber based polymer composite materials: Synthesis, surface modification, characterization and applications

This dissertation focuses on the functionalization and reactive recycling of readily available cryogenically ground, recycled ground tire rubber particles (GTR) and the cost effective utilization of these materials as a green renewable resource. This study encompasses raw material characterization, surface chemical modifications and applications of the GTR particles as a functional filler for various polymeric matrices. A good understanding of raw material composition and morphology plays a vital role during the material modification and end use applications. Recycling approaches are attempted by functionalizing GTR particles as a functional filler material and its incorporation to a epoxy resin matrix and vinylester resin for example. A unique finding during the raw material characterization using electron paramagnetic spectroscopy (EPR, or electron spin resonance, ESR) was the confirmation of the presence ofree radicals in these GTR particles. GTR/epoxy composites were prepared and the mechanical properties were studied and shown to exhibit enhanced mechanical properties, such as an increased tensile strength of 125%, flexural strength of 120% and flexural modulus of 140% compared to neat epoxy composites. The second part of the recycling project involved the development of a novel surface chemical modification of the engineered GTR particles. This work focuses on the use of the recycled GTR particles as a free radical initiator in the free radical polymerization of any acrylic monomers. Auto-initiated free radical polymerization of acrylic acid (AA) was successfully carried out to create poly acrylic acid grafted GTR (PAA-g-GTR). This synthesized material was then used as a new filler material for an epoxy matrix. Epoxy composites using the PAA-g-GTR as fillers were prepared and their mechanical properties were studied. The PAA-g-GTR/epoxy composites showed higher mechanical properties with an increase of modulus up to 180% as compared to the neat GTR/epoxy composite. The effect of particle size on the mechanical properties of cured epoxy resin composites was also studied by using 80 (177&mgr;m) and 300 mesh (44&mgr;m) GTR particles and comparing results.;Surface modification of the GTR particles was carried out using a direct fluorination reaction with fluorine/nitrogen gas mixture in a self-designed reactor system. Novel surface fluorinated GTR (FGTR) particles were produced and mechanical properties on FGTR/Epoxy composites were studied. The raw materials, synthesized surface chemical modified GTR particles and all the composites were characterized by ATR-FTIR, XPS, TGA, SEM, DSC, DMA, Universal Testing Machine (UTM). Surface fluorination of carbon based materials such as graphene oxide (GO) was carried out. The surface characterization and the possibility of fluorinated GO for optoelectronic application as well as semiconductor devices for the energy harvesting are discussed.