Surface Modification Of Inorganic Rigid Particles And Its Application In Polyethylene

Polyethylene has the advantages of high rigidity,easy processing and low cost.However,its own shortcomings have limited its development to a certain extent,such as poor heat aging resistance and poor toughness.Elasto-mers are often added to polymers to improve their performance,but often at the expense of reduced tensile strength of the material.Filling the inorganic rigid particles into the polymer can improve the toughness of the polymer and maintain the rigidity of the substrate.The first part:The results of chemical analysis showed that the main component of oil sand tailings was calcium carbonate?CaCO₃?with a content of 78.63 wt%.It was found by scanning electron microscopy?SEM?that CaCO₃ existed in the form of particles.The mechanical properties of modified oil sand tailings/HDPE composites are studied by surface modification of oil sand tailings with 5%stearic acid.The results show that the oil sand tailings can effectively improve the toughness and modulus of HDPE,but the tensile strength is reduced.It has the effect of heterogeneous nucleation on HDPE,the melting temperature of the composite material is slightly reduced,and the crystallization temperature is obviously increased,which provides a new method and idea for the comprehensive utilization of oil sand tailings.The second part:The critical particle spacing?L_C?criterion holds that L_C is an inherent property of the matrix,independent of the size and content of the dispersed phase particles.The effects of notch radius?R?on the applicability of critical particle spacing criteria were investigated by melt blending different sizes of CaCO₃ particles with HDPE.The results show that Lc is independent of the CaCO₃ particles size and content at the notch is a45°V-shaped notch with the tip radius R of 0.25 mm.However,Lc depends on the CaCO₃ particles size and content at the notch is a 45°V-shaped notch with the tip radius R of 1.0 mm.This indicates that the critical particle spacing criterion is inapplicable at a 45°V-shaped notch with the tip radius R of 1.0mm.The third part:The relationship between matrix properties and CaCO₃particle size with L_C of the blend system was studied by melt blending differ--rent size of CaCO₃ particles with different matrix properties of HDPE.The average distance between the microcracks?^*and the dimensionless factor C are obtained,which is consistent with Leibler's toughening model.It is verified that the Leibler toughening model is not only suitable for rubber toughened thermoplastic polymer systems,but also for inorganic rigid parti--cles toughen thermoplastic polymer systems.The fourth part:Nano-CaCO₃ particles modified with different kinds of fatty acids(C₅-valeric acid,C₁₀-decanoic acid,C₁₈-stearic acid)were used to study the effect of alkyl chain length on the structure and properties of HDPE/nano-CaCO₃ composites.The results showed that the surface hydrophobicity of nano-CaCO₃ enhanced with the increase of fatty acid alkyl chain length,the impact strength of the blend system increased gradually,and the tensile strength changed little,which had no significant effect on the crystallization behavior of the composite.The molecular chain segment has an increased ability to move inside the material,and the relaxation time is gradually increased.