New soybean oil-styrene-divinylbenzene thermosetting copolymers. II. Dynamic mechanical properties

A variety of new polymeric materials ranging from soft rubbers to hard, tou gh, and brittle plastics were prepared from the cationic copolymerization o f regular soybean oil, low saturation soybean oil (LoSatSoy oil), or conjug ated LoSatSoy oil with styrene and divinylbenzene initiated by boron triflu oride diethyl etherate (BF3. OEt2) or related modified initiators. The rela tionship between the dynamic mechanical properties of the Various polymers obtained and the stoichiometry, the types of soybean oils and crosslinking agents, and the different modified initiators was investigated. The room-te mperature storage moduli ranged from 6 x 10(6) to 2 x 10(9) Pa, whereas the single glass-transition temperatures (T-g) varied from approximately 0 to 105 degrees C. These properties were comparable to those of commercially av ailable rubbery materials and conventional plastics. The crosslinking densi ties of the new polymers were largely dependent on the concentration of the crosslinking agent and the type of soybean oil employed and varied from 74 to 4 x 10(4) mol/m(3). The T-g increased and the intensity of the loss fac tor decreased irregularly with an increase in the logarithmic crosslinking densities of the polymers. Empirical equations were established to describe the effect of crosslinking on the loss factor in these new polymeric mater ials. The polymers based on conjugated LoSatSoy oil, styrene, and divinylbe nzene possessed the highest room-temperature moduli and T-g's. These new so ybean oil polymers appear promising as replacements for petroleum-based pol ymeric materials. (C) 2000 John Wiley & Sons, Inc.