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SynopsisThe tensile behaviors of polystyrene (PS), poly(styrene/acrylonitrile) (SAN), high-impact polystyrene (HIPS), and poly(acrylonitrile/butadiene/styrene) (ABS) were examined systematically in the wide range of strain rate, 1.7 X 10-4-13.1 m/s. When glassy and brittle PS was a criterion, the incorporation of a polar group (SAN) only strengthened the hardness, and the fracture mode was the same as for PS. The introduction of dispersed rubber particles (HIPS) weakened the hardness a little but offered a new deformation mechanism, i.e., microcrazing (whitening), and contributed to the improvement of impact strength. In the heterogeneous system, the enhancement of matrix strength [e.g., preorientation or blending with poly(pheny1ene oxide) for HIPS] makes possible another deformation mechanism, i.e., shear band formation (cold drawing), which is superior to microcrazing for achieving higher impact strength, ABS, which incorporates concurrently two factors (polar group to matrix phase and dispersed rubber particles), can be regarded as an enhancement of the matrix strength of HIPS, In spite of the remarkable magnitude of its impact strength compared with that of the other three polymers, the deformation mechanism of ABS was limited to microcrazing. This indicated that only the introduction of a polar group (as nitrile group) could not strengthen the matrix as much as preorientation or blending with poly(pheny1ene oxide). INTRODUCTIONThe homopolymer of styrene (PS) exhibits brittle fracture and low impact toughness at room temperature. To make up for this deficiency, two measures are taken. First, the breaking stress is reinforced by the introduction of polar groups. For example, styrene and acrylonitrile are copolymerized (SAN). Secondly, the strain up to fracture is increased without an accompanying lowering of strength. This can be performed by the addition of rubber in particle form to polystyrene. It is important that the dispersed rubber particles are grafted onto polystyrene chains (not a simple milling-in of rubber with PS matrix). Poly(acrylonitrile/butadiene/styrene) (ABS) is a two-phase material consisting of elastomer particles in a glassy polymer matrix of SAN. ABS can be interpreted as a polymer in which the two measures described above are combined.Correlations among the chemical components of PS, SAN, HIPS, and ABS are schematized (Fig. 1).The aim of the present study is to investigate how the mechanical properties of a polymer change (1) by the introduction of a polar group, (2) with the incorJournal of Applied Polymer Science, Vol. 28,2209Vol. 28, -2216Vol. 28, (1983 poration of dispersed rubber particles which are grafted onto the matrix polymer chains, and (3) by the concurrent introduction of the factors (1) and (2), when polystyrene is primarily a criterion of the mechanical properties. The mechanical testing was limited to measurements of tensile and impact tensile properties at room temperature, where the shape of specimen and the deformation mode were all the same in the wide range of de...

SynopsisIn previous articles, we reported the change in physical properties of hydrophobic polymers caused by ahsorption of a very small amount of water. This article describes the changes in physical properties of three polyesters owing to absorption of water. The tested polymers were poly(ethy1ene terephthalate) (PET), poly(buty1ene terephthalate) (PBT), and polyethylene 2,6-naphthalate (PEN). P B T has more flexible main chains than that of PET, and P E N has more rigid main chains. The dielectric measurements revealed that water absorption results in shortening the relaxation time for PET, while the relaxation time for moist P B T becomes longer. The larger amount of absorbed water yields the higher density of PET and the lower density of PBT. The water absorption of the polyesters also yields increments in dielectric constants and relaxation strength. Distribution of relaxation time of the polyesters is narrowed by absorption of water.

SynopsisIn this paper, we report the changes in physical properties of polycarbonate caused by absorbed water and supply basic data for the application of this effect. Absorbed water increases monotonously with increase in relative humidity. Along with the increase in absorbed water, the relaxation time of the 6 process increases, the glass transition temperature rises, the area of the endothermic peak at the glass transition temperature increases, and the dynamic Young's modulus decreases. We conclude that the absorbed water fills holes but does not function as a crosslinking agent.

SynopsisThe orientation factor by infrared dichroism of polypropylene film was compared with the other orientation factors. After the correction of imperfect polarization and the suitable choice of the base line, it was found that infrared dichroism is a reliable indicator of the orientation factor. Orientation factors obtained from the 998 and 842 cm.-l bands agreed with the x-ray orientation factor, and that from the 975 cm.-l band agreed with the optical orientation factor.