N Naderi - M.Sc. student, South Tehran branch, Islamic Azad University, Faculty of graduate studies
M.H. Beheshty - Associate Professor, Iran Polymer and Petrochemical Institute
S Mazinani۳ - Assistant Professor, Amirkabir Nanotechnology Research Institute (ANTRI),

The curing behavior and cure kinetic parameters of an unsaturated polyester resin (UP) containing organically treated Na-Montmorillonite (Cloisite® 30B) was investigated by SPI test method and dynamic differential scanning calorimetry (DSC). The state of dispersion of the nanoclay was investigated by small angle X-ray scattering (SAXS) and transmission electron microscopy (TEM). The exothermic peak temperature and gel time was measured by using SPI test method according to ISO 584 at 80°C. Dual initiators system composed of benzoyl peroxide (BPO) and tertiary butyl perbenzoate (TBPB) were used as initiators. TBPB peroxide works well at high temperature and it has higher half-life compared to BPO which decompose around 80°C. Analyzing the curing curves based on SPI test method showed the low exothermic heat, long gel time and low cure rate as expected for BPO/UP resin cured containing TBPB. The addition of 1, 3 and 5% (w/w) of nanoclay resulted in decrease the gel time, exothermic peak and increase the cure rate compared to those obtained from the pure unsaturated polyester resin. Dynamic DSC with heating rate of 10°C/min was used to study the curing behavior of UP/ Cloisite®30B and pure UP system. The curing kinetic parameters were determined by using Borchardt-Daniels method. It was observed that curing reaction starting temperature and activation energy decreased in the system including UP/ Cloisite®30B compared to the pure resin. Results showed in UP/ Cloisite®30B systems higher reaction rate and more conversion ratio besides shorter cycle has been achieved. SAXS was used to determine the degree of intercalation and/or exfoliation of clay platelets via determination of the inter-platelets spacing. SAXS analysis results proved that the nanocomposite including 1 and 3 wt% Cloisite®30B showed exfloliation morphology and in 5 wt% Cloisite®30B showed intercalation. The TEM micrographs of the nanocomposite including 3 wt% Cloisite®30B depicted the exfoliation morphology and were in agreement with the SAXS analysis information

Unsaturated polyester resin, Hot cure, Dual initiators, Nanocomposites, Morphology,DSC, SAXS