Study On The Properties And Morphology Of Nano-CaCO₃/Elastomer/PVC Ternary-Phase Composites

Improvement of tensile strength and toughness of polymers has been one ofthe important research topics and priorities in materials science and engineering.Nano-CaCO3 becomes an attractive candidate for modified polymer applicationsbecause of its size effect, large surface/volume ratio and high surface activity. CPE,an uncrosslinked rubber impact modifier for rigid PVC, allows the processor tosignificantly increase the filler concentration without suffering loss of impactstrength or processibility. This thesis mainly dealt with the effect of changes inprocessing PVC blends and compositions on impact strength and tensile strength.The main work is shown as follows: Firstly, the results showed that the CPE coats the calcium carbonate panicleduring the process, resulting in an increase of the impact strength of the PVCalloys, compared to those separation structures formed by filling CPE and thecalcium carbonate panicles directly. In addition, coverage of the high energysurface of the calcium carbonate panicles with an organic compound results inbetter impact strength of the PVC blends than those filled with non-treatedcalcium carbonate panicle, which leads to decreased surface free energy andaggregation, improved homogeneity, ease of processing and better surface quality.Moreover, it's shown that PVC compounds increased impact strength of masterbatch and reduced particle size of calcium carbonate, proving that CPE can accepthigher concentration of calcium carbonate without causing loss in impact strength.Furthermore, Ternary composites containing encapsulated fillers have somewhathigher impact strength and tensile strength than those containing only CPEmodifier thanks to synergy effect. Improvement of mechanical properties of theblend system was maximized,when the ratio of CPE to nano-CaCO3 in the masterbatch is 1:2. Extensive analysis of the properties of ternary-phase PVC composites is also - IV -北京化工大学硕士毕业论文carried out. The phase morphology by TEM revealed a good dispersion ofcore/shell compositions in PVC matrix. Elastomer encapsulation of filler particlesshowed significant influence on the dispersion and interaction of the filler andpolymer components. CPE/NBR/ nano-CaCO3/PVC blends yield a markedincrease in the mechanical properties, compared to those blends mentioned aboveif NBR was used instead of CPE. In the case of low non-Newtonian shearingrate, PVC composites filled nano-CaCO3 exhibited an increase of viscosity, butas the non-Newtonian shearing rate rise, viscosity decreased, due to theshear-thinning effect and decrease in non-Newtonian parameters. To sum up, the master batch processed by nano-CaCO3 whose surface wasmodified by elastomer such as CPE, have both theoretical and practicalsignificances due to the increased processblity , impact strength and stiffness.