BIO-BASED REACTIVE DILUENTS AND THIOL-ENE PHOTOPOLYMERIZATION FOR ENVIRONMENTALLY BENIGN COATINGS
Tung oil was used as diene for modification via a Diels-Alder reaction with acrylate dienophiles. Tung oil was modified with three different acrylate molecules: 3-methacryloxypropyl trimethoxysilane (MAS), 2,2,2-trifluoroethyl methacrylate (TFM) and triallyl ether acrylate (TAEA) at atmospheric pressure. The modified tung oils were characterized using 1H NMR, 13C NMR, and FT-IR. The molecular weight and distribution were characterized using GPC, and MALDI-TOF. The effects of new acrylate modified tung oils on the properties of alkyd-based coatings film were investigated including hardness, solvent resistance, flexibility, gloss, impact resistance, contact angle, tensile, and thermo-mechanical properties. Viscosity of the alkyd can be greatly reduced by the introduction of modified tung oils. Drying time study showed that drying time can be altered by types and level of diluent added. All the results revealed that modified tung oils can be used as volatile organic compound (VOC) compliant in alkyd systems. Synthetic methods were developed to prepare thiols and mercaptopropionate thiols for thiol-ene photopolymerization. New thiols were characterized by 1H NMR, 13C NMR, Fourier transform infrared spectroscopy (FT-IR), and elemental analysis (C, H, S, O). Photopolymerization kinetics of the thiols with representative alkenes were investigated by time resolved Fourier transform infrared spectroscopy (FT-IR) with and without photoinitiator. It was proposed that steric hinderance of thiol structures lower the initial reaction rate of photopolymerization. An experiment was planned according to ternary mixture design to investigate the influence the three thiols on the thermo-mechanical and coatings properties of thiol-ene photopolymerizable materials. It was found that the steric and rigidity of the double cycloaliphatic structure of thiol enhanced the tensile strength, tensile modulus, glass transition temperature (Tg) and pencil hardness with loss of crosslink density of the film. The result suggested that steric and rigidity of thiols structures played an important role in both kinetics and material properties on thiol-ene photopolymerization. A thiol colloid oligomer was prepared via sol-gel method from mercaptopropyl- trimethoxysilane (MPTS). The thiol colloid oligomer was characterized using 1H NMR, 29Si NMR, FT-IR, GPC, and MALDI-TOF mass spectroscopy. The thiol colloid was attempted to photopolymerize with triallyl ether modified tung oil (TAETO) as a bio-based alkene via thiol-ene photopolymerization. However, kinetics results via time-resolved FT-IR indicated that MPTS colloid oligomer did not affect the initial reaction rate and final conversion of MPTS/TAETO system due to the immiscibility between TAETO and MPTS oligomer.
School:The University of Akron
School Location:USA - Ohio
Source Type:Master's Thesis
Keywords:tung oil diels alder reaction thiol ene photopolymerization
Date of Publication:01/01/2007