Calcareous phosphate ore can be utilized as a cost-effective alternate to other inorganic fillers for polymer-based composites. In this study, composites of high-density polyethylene and phosphate rock ore particles were prepared by melt blending and injection-molding techniques. The thermomechanical, rheological, and mechanical properties of these composites were studied to investigate the effect of filler loading on their functionality. The reduction in the crystallinity of phosphate ore/high-density polyethylene composites was observed compared to that of the neat high-density polyethylene. The relative crystallinity of the neat high-density polyethylene decreases from 53 to 30% by the addition of 2.5–15 wt% of ore, respectively. Comparison of the linear dynamic viscoelasticity for the neat high-density polyethylene and the ore-filled composites shows t a monotonic increase in both storage modulus and loss modulus with the increasing frequency. The viscoelastic behavior at high frequencies remains unaffected. However, at lower frequencies, both G′ and G″ exhibit diminished frequency dependence. It was also observed that higher filler content decreased the tensile and impact strength, whereas the Young's modulus of the composites increased. The morphological analysis shows relatively weak interaction between the fillers and the matrix because of agglomeration which in turn adversely affects the mechanical properties of the composites. 相似文献
Summary: The rheological behavior of polyethylenes is mainly dominated by the molecular weight, the molecular weight distribution and by the type, the amount and the distribution of the chain branches. In this work a linear metallocene catalyzed polyethylene (m‐PE), a branched metallocene catalyzed polyethylene (m‐bPE), a conventional linear low density polyethylene (LLDPE) and a low density polyethylene (LDPE) have been investigated in order to compare their rheological behavior in shear and in elongational flow. The four samples have similar melt flow index and in particular a value typical of film blowing grade. The melt viscosity has been studied both in shear and in isothermal and non‐isothermal elongational flow. The most important features of the results are that in shear flow the m‐PE sample shows less pronounced non Newtonian behavior while in the elongational flow the behavior of m‐PE is very similar to that of the linear low density polyethylene: the narrower molecular weight distribution and the better homogeneity of the branching distribution are reasonably responsible for this behavior. Of course the most pronounced non‐linear behavior is shown, as expected, by the LDPE sample and by the branched metallocene sample. This similar behavior has to be attributed to the presence of branching. Similar comments hold in non‐isothermal elongational flow; the LDPE sample shows the highest values of the melt strength and the other two samples show very similar values. As for the breaking stretching ratio the opposite is true for LDPE while m‐PE and LLDPE show higher values. The transient isothermal elongational viscosity curves show that the branched samples show a strain hardening effect, while LLDPE and m‐PE samples present a linear behavior.
Dimensionless flow curves of different polyethylene samples. 相似文献
