Enhanced polycarbonate toughness. II: Mechanisms

Abstract

Glassy shell-rubbery core polymer particles, 0.1 to 0.2 pm in diameter, increase the plane strain J,, values of 3.175 mm thick polycarbonate from 3.05 kJ/m2 (no particles) to 9.5 W/m2 (7.5 phr particles) at 23°C. Some modest decreases in these values are caused by tests at -20°C in samples 9.525 and 3.175 mm thick. If only the particle concentration is varied, J,, increases monotonically to 7.5 phr (by wt), then levels off or decreases slightly at 10.0 phr. The total volume of 1 to 2 pm diameter cavities formed in the matrix by the apparently unbonded particles behaves similarly; cavity volume and J,, are directly related. With increasing particle concentration the tensile modulus is unchanged, the yield stress and strain decrease modestly, the strain at fracture decreases appreciably, and the heat recoverable orientation in the fractured samples decreases. Few cavities are formed. The particles reduce the extent of shear deformation in the tensile samples.

Micromechanics, macromechanics and constitutive modeling of the elasto-viscoplastic deformation of rubber-toughened glassy polymers

“…For example, well-dispersed particles have been observed to increase the toughness of the blend, whereas poorly dispersed particles can actually increase the brittleness of the blend (Cheng, et al. [18], Kim, et al [40]). It is also important to determine the specific modes of local fracture under a given mode of applied deformation; whether the polycarbonate matrix displayed brittle crack propagation, or if the onset of macroscopic 148 R, 8 fracture was associated with large levels of plastic stretches leading to localized matrix ligament drawing and subsequent chain scission events.…”

“…Kim [40] found that these particles are effective in enhancing toughness of polycarbonate. In summary, the major factors that influence the ductile-to-brittle transition in rubber-toughened polycarbonate are * dispersion of the rubber particles in the polycarbonate matrix.…”

“…[18], Kim, et al [40] and Johnson [38]. Figure (1-4) shows experimentally-obtained uniaxial compression data for different rubber-toughened polycarbonate blends at room temperature and constant axial strain-rate (Eaxiai = -0.01s') (Johnson [38]).…”

Photo‐fabrication of surface relief gratings on polymer films

“…Recently we have reported in a number of publications the direct formation of large amplitude surface relief gratings on epoxy-based nonlinear optical (NLO) polymer films containing azobenzene groups (Ref. [7][8][9][10]. The surface relief gratings were produced upon exposure to an interference pattern of Ar+ laser beams at modest intensities (3-100 mW/cm2) in a single step.…”

“…We have observed that p-polarized recording beams induced large surface relief gratings while s-polarized recording beams gave rise to almost negligible surface change (Ref. [8][9][10]. This implies that the photoinduced orientation of the azobenzene chromophores has a very important role in surface modulation process.…”