The effect of weld-lines on the morphology and mechanical properties of amorphous polyamide/poly(ethylene-ran-propylene) blend with various amounts of an in situ compatibilizer
Jk. Kim et al., The effect of weld-lines on the morphology and mechanical properties of amorphous polyamide/poly(ethylene-ran-propylene) blend with various amounts of an in situ compatibilizer, POLYMER, 42(5), 2001, pp. 2209-2221
The effect of weld-lines on the morphology and mechanical properties of 80/
20 (wt/wt) amorphous polyamide and poly(ethylene-ran-propylene) (EPR) blend
with various amounts of maleic anhydride grafted EPR (EPR-M) as an in situ
compatibilizer was investigated. In this blend, the effect of crystallizat
ion on weld-line strength was completely excluded; thus mechanical properti
es depend upon the blend morphology and interfacial adhesion strength. As t
he amount of EPR-M was increased, the dispersed domain sizes were reduced,
whereas the sheer modulus and the viscosity of the blend increased. We have
shown that the injection-molded blend without weld-lines exhibited traditi
onal skin-core morphology. Namely, the dispersed domains at sub-skin layers
are strongly elongated toward the flow direction, while those at core regi
ons are not deformed. The sub-skin layer of specimens without weld-lines wa
s significantly reduced with increasing amount of EPR-M. For specimens with
weld-lines, the dispersed domains of the blend without EPR-M at sub-skin l
ayer are elongated perpendicularly to the dow direction. However, with incr
easing EPR-M content, very fine and isotropic morphology is observed.
Both the elongation at the break and Izod impact strength of the weld-speci
men increased steadily with increasing amount of EPR-M. But these values ar
e still lower than those of non-weld specimens, even for blends with large
amounts of EPR-M. This is because some dispersed domains in weld specimens
are elongated perpendicularly to the tensile (or impact) direction. However
, the 'V-notch' found at the weld-line of specimens does not affect the mec
hanical properties. (C) 2000 Published by Elsevier Science Ltd.