synopsisA number of terpolymers, incorporating as the elastomer phase polybutadiene, polyisoprene, poly-2,3-dimethylbutadiene, poly (butadiene-co-styrene), and poly (butadieneco-2-methyl-kinylpyridine), were studied. Matrices were composed of poly(styreneco-acrylonitrile) (SAN), poly(a-methylstyrene-co-acrylonitrile), and poly(styrene-coacenaphthylene). At constant elastomer content and elastomer molecular weight in systems employing a SAN matrix, Izod impact resistance was found to vary inversely with rising elastomer-glass transition temperature. In systems of various matrix composition, using a polybutadiene elastomer, heat deflection temperatures were found to vary directly and impact resistance inversely with rising matrix-glass transition temperature. In acrylonitrile-butadene-styrene (ABS), systems of constant matrix composition and elastomer content, varying the elastomer molecular weight, from 0.6 to 2.6 x 106 resulted in increasing the Izod impact resistance from 0.67 to 12.8 fblb/in. of notch.

Several brittle thermoplastic materials, including polystyrene, SAN, and PMMA, were tested in tension using a spectrum of testing rates up to 15,000 in./min (630 cm/sec). At test velocities below 7000 in./min (294 cm/sec), the materials behaved “classically” with strength properties increasing, elongation decreasing, and single fractures generally forming. At rates between 7000 and 9000 in./min (294 and 378 cm/sec), a transition from classical to stress wave‐initiated fracture was observed. The mechanical properties, the nature of the fracture, and the nature of the crazing preceding fracture were shown to be profoundly affected when the materials were strained at rates sufficient to initiate stress wave fracture. Under these conditions, the apparent load‐carrying capabilities of the materials were reduced by an order of magnitude.

SynopsisFour commercial grades of ABS of varying physicomechanical properties were fractured in tension at three straining rates. Photomicrographs of the fracture surfaces were used to qualitatively describe the effects of straining rate on craze growth. Based on a micrograph of what is assumed to be the first stress-activated state of craze formation, a model describing the function of the elastomer phase in these materials is presented.

Ethyl 3,4,5-trimethoxymandelate (IV) (7). A solution of 3 grams (0.0134 mole) of (I) (vacuum dried) in 20 ml. of anhydrous ethanol was saturated with dry hydrogen chloride at 0-5°and refrigerated (4°) over night. Excess solvent was removed from the purple semi-solid mass at the water pump and 50 ml. of water added. Solid barium carbonate was added in excess to neutralize the acid, the mixture kept for 2 hours in the dark, filtered, and the filtrate extracted with four 30-ml. portions of ethyl acetate, using the first two portions of solvent to extract also the filter cake. The combined extracts were dried with sodium sulfate, and the solvent was removed under vacuum to give a yellow oil which crystallized slowly on standing. Recrystallization from ethanol-water gave 1.91 grams (53%) of (IV), m.p. 83-5°.

synopsisA number of terpolymers, incorporating as the elastomer phase polybutadiene, polyisoprene, poly-2,3-dimethylbutadiene, poly (butadiene-co-styrene), and poly (butadieneco-2-methyl-kinylpyridine), were studied. Matrices were composed of poly(styreneco-acrylonitrile) (SAN), poly(a-methylstyrene-co-acrylonitrile), and poly(styrene-coacenaphthylene). At constant elastomer content and elastomer molecular weight in systems employing a SAN matrix, Izod impact resistance was found to vary inversely with rising elastomer-glass transition temperature. In systems of various matrix composition, using a polybutadiene elastomer, heat deflection temperatures were found to vary directly and impact resistance inversely with rising matrix-glass transition temperature. In acrylonitrile-butadene-styrene (ABS), systems of constant matrix composition and elastomer content, varying the elastomer molecular weight, from 0.6 to 2.6 x 106 resulted in increasing the Izod impact resistance from 0.67 to 12.8 fblb/in. of notch.