A novel acrylic resin has been developed for injection molded precision lenses. This resin is a copolymer of tricyclodecyl methacrylate (TCDMA) with other acrylic monomers.

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SYNOPSISIn order to improve the weatherability of acryonitrile-styrene-butadiene rubber graft polymer (ABS resin), a n attempt was made to develop a resin (AAS resin) in which acrylic rubber of good weatherability was used instead of butadiene rubber. First, by copolymerizing dicyclopentenyl-methacrylate (DCP-MA, 3% ) with butyl acrylate, crosslinked acrylic rubber was obtained. This also introduced grafting sites into the rubber. Next, methods of graft copolymerizing styrene and acrylonitrile with this rubber were examined. An emulsionsuspension polymerization method was developed in which the initial stage of the polymerization, emulsion polymerization, changed into suspension polymerization during the process. By this method of polymerization, rubber particles were combined and enlarged, bringing about a graft-type resin with high impact resistance. This polymerization method is industrially useful because particle-shaped resins are obtained without the need of a salting-out process. The AAS resin, obtained in this way, has much improved weatherability over ABS resin and shows strength equal to that of ABS resin.

Plate type specimens were prepared by the injection molding of rubber modified plastics such as acrylonitrile-butadiene-styrene terpolymer (ABS resin) and acrylonitrile-acrylic elastmer-styrene terpolymer (AAS resin). With these specimens the effect of the orientation of rubber particles in these resins on their strength anisotropy was examined. It was found from the experimental results of strength anisotropy that spots with strong anisotropy of tensile strength inside the molding plate tended to show lower dart fall impact values. It was also found that the orientation showing high tensile strength at each measuring spot coincided nearly with the orientation giving the biggest cracks in the dart fall impact tests. An examination was also made on the relationship between the orientation of rubber particles and the anisotropy of the tensile strength, or the dart fall impact value. The results showed that the anisotropy of the tensile strength increased and the dart fall impact value decreased as the orientation of rubber particles increased. Further more, it became clear that the effect of the rubber particle orientation on the strength differed with the kind of resins and that the AAS resin was less affected by the orientation than the ABS resin.

Acrylonitrile‐acrylic elastomer‐styrene terpolymer (AAS resin) was developed to improve weatherability of acrylonitrile‐butadiene‐styrene terpolymer (ABS resin). To compare thermal stability of both resins, test parts of AAS and ABS resins were injection molded at various temperatures and the Izod impact value of the resulting moldings was measured. A study was then made to find the relationship between this value and deterioration of the resins. AAS resin was molded at temperatures from 180°C to 280°C. The impact value of the resulting moldings was almost constant for temperatures up to 260°C, with the first major decrease occurring at 280°C. In contrast, the impact value of conventional ABS resin moldings constantly decreased as the molding temperature was elevated. To explain this phenomenon in both resins, two types of test program steps were undertaken: (1) The cause of the change in characteristics of the AAS resin was determined by obtaining its stress‐strain curve in a high‐speed flexural strength test; measuring its infrared absorption spectrum; and determining its flow properties with a constant‐pressure extrusion type rheometer; (2) the distribution of elastomer in the resin was observed with an electron microscope. It was found that the decrease of impact values of both resins at high temperatures is caused by deterionration of the elastomer. Also, it was found that the different relationships between the impact value and molding temperatures for AAS and ABS resins are due to the difference between the rates of thermal degradation of the acrylic elastomer and butadiene elastomer.