ABSTRACT: Mechanical and thermal properties of materials prepared by curing epoxidized soybean oil with various cyclic acid anhydrides in the presence of tertiary amines were investigated by dynamic mechanical thermal analysis and thermogravimetry. All samples presented thermoset material characteristics that were dependent upon the type of anhydride, the anhydride/epoxy molar ratio, and epoxy group content. The thermosets obtained from anhydrides with rigid structures as such phthalic, maleic, and hexahydrophthalic showed higher glass transition temperatures (Tg) and cross-linking densities. As expected, the Tg decreased as the anhydride/epoxy ratio decreased. The influence of the degree of epoxidation of soybean oil on the mechanical properties and Tg was also investigated. It was found that the higher the epoxy group amount, the higher the Tg and hardness. Cured resins exhibited thermal stability up to 300°C, except for those prepared with dodecenylsuccinic anhydride, which began to decompose at lower temperature. They presented excellent chemical resistance when immersed in 1% wt/vol NaOH and 3% wt/vol H 2 SO 4 solutions but poor chemical resistance in the presence of organic solvents. Paper no. J10209 in JAOCS 79, 797-802 (August 2002). KEY WORDS: Chemical resistance, dynamical mechanical properties, epoxidized soybean oil, epoxy resins, thermogravimetric analysis, thermosetting polymers. Vegetable oils represent an interesting renewable source for the production of useful chemicals and new materials (1). Soybean oil is readily available in bulk and is mainly composed of TG molecules derived from unsaturated acids, such as oleic acid (22%), linoleic acid (55%), and linolenic acid (7%). Although unsaturated acids possess double bonds, which are the reactive sites for coatings and paints, they need to be functionalized by the introduction of epoxy, hydroxyl, or carboxyl groups in order to be used for preparation of polymeric materials. Soybean oil can be epoxidized by different methods (2-4) yielding conversions and selectivities higher than 90%. Industrially, it is used mainly as a polyvinyl chloride additive to improve stability and flexibility. New applications have been made possible by the use of photochemically initiated cationic curing (5) and by the preparation of thermosetting materials such as epoxy resins. Epoxy resins are widely used as adhesives and as matrices in composite materials because of their good physical and chemical properties. Toughness and other properties of epoxy resins can be significantly improved by the modification of classical epoxy resins, such as those based on diglycidylether of bisphenol A (DGEBA). Epoxidized vegetable oils prepared from the most unsaturated oils, e.g., soybean oil or linseed oil, can be used for such purpose. In this work we report dynamic mechanical properties of different materials prepared by curing fully and partially epoxidized soybean oil (ESO) with various cyclic acid anhydrides in the presence of tertiary amines. Thermal and chemical resistance were also investigated. MATERIALS AND METHODS Phthalic anhydride (PA), hexahydrophthalic anhydride (CH), maleic anhydride (MAL), and N,N′-dimethylaniline (ARO) were purchased from Aldrich Chemical Co. (Milwaukee, WI) and purified just before use by standard methods. Succinic anhydride (SUC) was purchased from Sigma Co. (St. Louis, MO) and recrystallized from chloroform. Triethylamine (TEA) was purchased from Merck (Darmstadt, Germany) and distilled before use. Dodecenylsuccinic anhydride (DDS) (Sigma Co.) and 1,4-diazabicyclo[2.2.2]octane (DABCO) (Aldrich Chemical Co.) were used without further purification. Fully ESO was supplied by CBM Indústria, Comércio e Distribuição Ltda. (Cachoeirinha, RS, Brazil) and contained 4.1 mmol epoxide/g determined by the oxirane oxygen standard method (AOCS Cd 9-57) (6). On average, ESO has a M.W. of about 929 g/mol and contains about 3.8 epoxy groups per TG. Partially ESO were prepared using the methyltrioxorhenium-CH 2 Cl 2 /H 2 O 2 system (4). The degree of epoxidation was calculated by integrating the signals in the 2.9-3.1 ppm region of the 1 H NMR spectra, corresponding to the cis epoxy hydrogens. Dynamic mechanical properties were measured on Polymer Laboratory-Dynamic Mechanical Thermal Analysis equipment operating in single cantilever mode. The measurements were performed from −60 to 100°C at a heating rate of 2°C/min and frequency of 1 Hz. The glass transition temperature (Tg) was determined as the temperature at the maximum of the tan δ vs. temperature curve. A TA Instruments model 2050 thermogravimeter was used to measure the weight loss of the polymeric materials in an N 2 atmosphere. The samples were heated from 30 to 800°C at a heating rate of 10°C/min
