In the present study, the physical, chemical, thermal and mechanical properties of
polyesters used in the production of composite materials were investigated by using
initiators at different ratios. In scope of the study, orthophtalic and isophtalic
resins were used. Methyl ethyl keton peroxide (MEKP) has been used as initiator with
different ratio; 1,0%, 1,5%, 2,0% and 2,5% (v/v). Cobalt octaoate (C16H30CoO4) was
added as catalyst in the rate of 1% to increase curing rate and yield of polymerization.
Gelation temperature, gelation time, peak exotherm temperature and viscosity analysis
were carried out to determine those physical parameters. Thermal stabilities were
determined with Thermogravimetric analyzes (TGA). Fourier transform Infrared Spectroscopy
(FT-IR) was used to investigate the molecular interaction in the end of the polymerization.
Mechanical properties (tensile strength, elastic modulus, flexture strength and flexture
modulus) were determined with the Universal Test Machine. As the result, the mechanical
properties of the unsaturated polyester resin changed based on the initiator ratio.
When the relation between initiator ratio and the mechanical properties is examined,
mechanical strengths of the composites composed of the isophthalic resin have generally
higher than the composites composed of the orthophtalic resin. Optimum initiator ratio
for mechanical strength values were determined as 1% for the composites obtained from
isophtalic and orthophtalic resins.