Heterogeneous polyamide 66/syndiotactic polystyrene blends: Phase structure and thermal and mechanical properties

Abstract

ABSTRACT:The structural and physical properties of polyamide 66 (PA66)/syndiotactic polystyrene (sPS) blends were studied with electron microscopy, wide-angle X-ray scattering (WAXS), differential scanning calorimetry (DSC), dynamic mechanical thermal analysis, and tensile creep, stress-strain, and impact measurements. Attention was primarily concentrated on blends with sPS weight fractions (w 2 ) in the range of 0 Ͻ w 2 Յ 0.50. DSC and WAXS showed that the integral crystallinity of the PA66 and sPS components in the blends was virtually unaffected by the blend composition. Polymorphism of sPS was observed for blends with w 2 Ն 0.50. Blends with 0.40 Յ w 2 Յ 0.60 consisted of partially cocontinuous components; otherwise, particles of the minority component were dispersed in the continuous majority component. The compatibilizer enhanced interfacial adhesion so that no debonding of the components in the fractured blends was observed. The compliance and creep rate of the blends at room temperature decreased proportionally to the sPS fraction; a corresponding increase in the storage modulus (EЈ) was observed in the 25-100°C interval. However, EЈ (125°C) noticeably declined with w 2 and thus showed that sPS did not improve the dimensional stability of the blends at elevated temperatures. The yield strength consistently grew with w 2 , whereas the yield strain dropped markedly; blends with w 2 Ն 0.60 were brittle, showing very low values of the ultimate properties. The stress at break, strain at break, and tensile energy to break displayed some local maxima at 0.25 Յ w 2 Յ 0.30, whereas the tensile impact strength steeply decreased.

Strong synergistic improvement of mechanical properties in HDPE/COC blends with fibrillar morphology

“…If the interfacial adhesion is weak, the fracture propagates along the interphase and, as a result, both phases are clearly distinguishable on the fracture surfaces . If the interfacial adhesion is strong, the fracture propagates straight through the strongly adhering phases and, consequently, the two phases are hard to differentiate , which was observed in the HDPE/COC blends (Fig. ).…”

“…and ). Although the fracture was performed at liquid nitrogen temperature, that is, far below the T g of blend components, the fracture surface was not completely brittle (no sharp fracture lines ) and HDPE phase exhibited typical microplastic deformations, which develop due to local overheating during the fracture .…”

“…The specimens for SEM were prepared in two ways. First, the fracturing under liquid nitrogen was employed in order to prepare samples for the estimation of the interfacial adhesion . Second, the combination of cutting, smoothing and etching was used for precise visualization of phase morphology .…”

Predictions of Storage Modulus of Glass Bead-Filled Low-Density-Polyethylene Composites

“…In addition, dynamic mechanical measurements over a range of temperatures provide valuable insight into the structure, morphology and properties of polymeric blends and composites. A lot of dynamic mechanical analyses on polymeric blends and composites have been done [1][2][3][4]. Zhang et al [1] measured dynamic mechanical properties of composites filled with SMA particles and short fibers, and found that the storage modulus reaches the maximum at the SMA phase transformation temperature of approximate 120˚C.…”

“…The results showed that a higher storage modulus enhancement was obtained when the organo-clay nanoplatelets were delaminated and more homogeneously dispersed. Kolarik [4] researched the Phase structure and thermal and mechanical properties of heterogeneous polyamide 66/syndiotactic polystyrene blends, and found that storage modulus (125˚C) noticeably declined with weight fraction and thus showed that sPS did not improve the dimensional stability of the blends at elevated temperatures. Since 1998, Liang et al [5][6][7][8][9] have investigated the effects of glass bead content and size on the viscoelastic properties of filled polyolefin composites, and get some useful findings.…”