Laminates From the Soy-Based Polyurethanes and Natural and Synthetic Fibers
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Laminates From The Soy-Based Polyurethanes and Natural and Synthetic Fibers. Zoran S. Petrović, Wei Zhang, Ivan Javni and Andrew Guo, Kansas Polymer Research Center, Pittsburg State University, Pittsburg, KS 66762 ABSTRACT Two polyols were prepared from soybean oil, one by epoxidation route and the other via hydroformylation. The polyol obtained by epoxidation has secondary groups and has a gel time of more than one hour when reacted with crude MDI to produce polyurethanes. Hydroformylated polyol has a gel time with MDI of several minutes and is more suitable for reinforced reaction injection molding (RRIM). The first group of polyurethanes had a glass transition close to 80 0C while the hydroformylated gave about 30 degrees lower Tg and comparable strength but higher elongation. Adding glycerin as the crosslinker could increase both Tg and strength. Two series of laminates were prepared using several types of glass fabric, carbon fiber, polyester, cotton and jute fabrics r as reinforcements. Hydroformylated polyol based polyurethane composites were softer, with lower Tg, modulus and strength. Composites with organic fibers were lighter and more flexible than the glass reinforced samples. For comparison glass reinforced epoxy and polyester were prepared and tested. Organic fibers gave lower stiffness and strength than the corresponding glass or carbon fiber. Although the neat polyester and epoxy resins had somewhat higher strengths than the polyurethanes from soybean oil, mainly due to the higher crosslinking density, the composites from the soy oil-based resin displayed comparable or better properties. Glass transition and mechanical properties of the soy-based polyurethanes was varied from about 70 0C to 140 0C with added crosslinkers. Processing time of the soy-polyurethanes resins was shorter than that of the other two resins. INTRODUCTION Polymers from renewable resources can be useful matrix binders for composites. They must compete with petrochemical resins on price and performance. In this work we will describe the properties of polyurethane resins and composites obtained from vegetable oils and different reinforcing agents. Vegetable oils impart high hydrophobicity and good thermal properties as well as excellent electrical properties to the polyurethanes. These resins also have good processability (good flow properties suitable for machine applications, and adjustable gel and curing time). Our objective was to examine the interaction of two soy-based resins with high strength reinforcements (carbon and glass fibers) and all-organic reinforcements (polyester, cotton, jute). Our research group is specialized in the synthesis and application of polymers from vegetable oils. We have developed different types of polyols (containing secondary OH groups, from epoxidized soybean oil, or primary OH groups, via hydroformylation technology- Fig. 1), oxazolidone prepolymers, and urethane prepolymers from soybean oil. The polyols have been used to prepare rigid urethane foams and casting resins for electrical insulatio
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