Degree Name

Master of Science (MS)

Semester of Degree Completion


Thesis Director

Ping Liu


In order to promote applications of recycled automobile tires, composite materials of recycled rubber tire particles with ethylene co-vinyl acetate (EVA), polybutadiene (PB), and Primacor were studied in the thesis. The composites were processed using a single screw extruder and a pelletizer. Compression molding was used to form specimens for hardness and impact tests. Mechanical properties of the composites were investigated in terms of tensile strength, percent elongation, Durometer hardness, and impact energy.

In this study, the content of recycled rubber was between 0 and 40 percent. Various matrices were processed using a combination of EVA, PB, or Primacor to combine the recycled rubber tire particles. The effects of EVA, PB, and Primacor were studied on the mechanical properties of composite containing recycled rubber tire particles. The morphology of the blends or composites was studied using an optical microscope.

The results of this thesis showed that increasing recycled rubber content decreased the strength of the composites. The percent elongation of composites containing recycled rubber decreased drastically when the amount of recycled rubber exceeded 10%. When 10% PB was added to composites containing EVA, PB, and 10% recycled rubber, PB was beneficial to the percent elongation and the impact energy of the composite. Increasing the amount of PB in a composite decreased the hardness of the composite. When containing Primacor and EVA, the mechanical properties of the composites were better than those containing only EVA or Primacor. It was found that a composite with a matrix containing a 90:10 ratio of Primacor to Eva offered the best mechanical properties. The useful range for Primacor in a matrix would be 90% to 70% with 10% to 30% EVA.

After viewing composite materials under an optical or stereo microscope it was found that blends containing Primacor and EVA displayed no phase separation, while blends of EVA and PB showed distinct boundaries. Also, blends of Primacor and EVA are able to bond and interlock with recycled rubber particles, while the matrix of EVA and PB did not bond tightly with the rubber particles.