Morphology-induced mechanical grafting in immiscible polymer blends

Immiscible polymer blends are a class of composite materials in which morphology development is critical to the establishment of good mechanical properties since little or no chemical bonding occurs across the polymer domain interfaces. Morphology evolution was studied in several binary blend groups containing an amorphous polymer and a semi-crystalline polymer. Co-continuity development and the role of such morphologies in property development were examined with regard to defining structure-property relationships for selected mechanical properties. The degree to which these morphological structures affect molecular configurations, i.e. crystallinity and chain orientation, was also studied by thermal and spectroscopic analysis.; The effect of blend morphology on crystallinity development, studied via thermal analyses measurements, showed that crystallinity is suppressed for blends with co-continuous morphologies. Mechanical properties also depended on domain morphology and subtle differences in co-continuity generated by varied processing methods were reflected in interesting and revealing variations in certain mechanical properties.; Crystallinity suppression observations indicate that co-continuous morphologies are crucial to the establishment of an interlocked structure where molecular rearrangements are suppressed during crystallization owing to shear-induced orientation coupled with morphological hindrance. The enhanced continuity observations and moderately improved mechanical properties of certain blends processed with advanced extruder mixing elements was a major finding of this thesis. This process, which includes unusually high levels of elongational shear mixing is a novel approach to the improvement of mechanical properties in single screw extrusion.; Raman spectroscopic observations revealed an anomalous increase in the in-phase (1128 cm-1) and out-of-phase (1061 cm-1) stretching vibrational intensities of polyethylene molecules that normally arise from their crystalline conformations, but which in this study were found in low crystallinity co-continuous regions. This anomaly is indicative of an unusual orientation of the molecules in those compositions, one in which the simultaneous crystallinity reduction and enhancement of the crystalline Raman intensities has been used to establish the mechanics of the grafting process in co-continuous morphologies of immiscible polymer blends.; Advances in the interpretation of image analysis data developed as part of this thesis to quantify developing continuity in immiscible blends has enhanced the scientific understanding and engineering design of these blends.