| New materials and new technologies provide a striking appearance of the metal effect for plastic products.At present,the metal effect of plastic products is obtained by spraying metal-effect paint on the surface of plastic products.Spraying process is complicated,which has serious pollution to the environment.However,the metallic effects of plastic products were produced through incorporation of flash aluminum flake pigments in thermoplastic resins by injection molding.This production method could eliminate post-processing techniques,such as spray coating,painting,or metallization.The metal particles are difficult to disperse uniformly in the polymer matrix.And there is a weaker interface between the metal particles and the polymer.Therefore,the performance of polymer composites filled with metal particles has been severely constrained.However,ultrasonic-assisted processing can improve the processability of the polymer and improve the dispersion of the metal particles in the polymer matrix.Obviously,the ultrasonic treatment may also overcome the defects caused by the blending of the metal flash aluminum pigment with the polymer,while improving the mechanical properties of the composites.In this paper,HDPE/Al and ABS/Al composites of metallic effects was prepared by melt blended methods,and then metallic effects in injection molded parts is created used composites by injection molding process.In addition,we use SEM,AFM to study the surface morphology of injection molded parts,and characterize the metallic effects of injection molded parts by using spectrophotometer.At the same time,the effects of crystallinity and thermal conductivity on the metallic effects were studied.Finally,the rheological behavior of HDPE/Al composites was measured by using a self-improved ultrasonically-aided torque rheometer in the absence and presence of ultrasound treatment.The effects of ultrasonic treatment on the crystal structure,crystallinity and thermal stability of HDPE/Al composites were also investigated.The main contents of the study are as follows:(1)The effects of the particle size and content of aluminum pigment on the surface morphology of injection molded parts were studied.The results show that the aluminum pigments is covered by the polymer in most areas of the surface of the injection molded parts.However,aluminum pigments are more or less randomly appearing leafing in very few local areas.The leafing is surrounded by a polymer,and the polymer melt has a shrinkage during the injection molding stage.The region with the leafing phenomenon is filled with aluminum pigment particles and the aluminum pigment particles have no shrinkage effect.These induces the micro shrinkage and causes micro caverns,which increased surface roughness.At the same time,AFM results show that these also improve the surface roughness of the injection molded parts.(2)Based on standard deviation method and fractal information dimension method,the dispersion and distribution of aluminum pigment in polymer were analyzed quantitatively.The results showed that the dispersion and distribution of aluminum pigment in HDPE/Al-100-3 and HDPE/Al-40-5 composites were the best.Their fractal information dimension has the largest value,which is 1.85 and 1.78 respectively.(3)Based on the L*a*b*color space,the metallic effects in injection molded parts is characterized by the brightness and whiteness index,and the reflectivity.The results show that aluminum pigment improves the brightness,whiteness index and reflectivity of HPDE components,and enables the HPDE component to obtain a metallic effect.The injection molded parts were loaded with 40 ?m aluminum pigments of 3wt%and their surface reflectance was almost double that of pure HDPE.At the same time,aluminum pigments improve the crystallinity and thermal conductivity of HDPE,which has a positive effect on improving the metallic effects of injection molded parts.(4)The aluminum pigment has a significant effect on the mechanical mechanics of HDPE/Al composites.The experimental results show that the interfacial cracks between the aluminum pigment and the HDPE matrix lead to the decrease of the tensile strength,impact strength and toughness of the composites.HDPE/Al composites have a lower mechanical properties associated with a larger particle size of aluminum pigments and a higher content.(5)The metallic effects and mechanical properties of ABS/Al composites were studied on the basis of previous exploration of HDPE/Al composites.The results show that the aluminum pigment enables ABS to achieve shiny metallic luster,but their brightness,whiteness index and reflectivity is lower than pure ABS.At the same time,aluminum pigments also reduce the tensile strength,impact strength and toughness of ABS/Al composites.(6)The rheological behavior of HDPE/Al composites was studied by ultrasonic assisted capillary rheometer.The effects of ultrasonic intensity,aluminum pigment content and particle size on the viscosity of the composites were discussed.The results show that ultrasonic vibration improves the dispersion of aluminum pigments,prompting them to be more uniformly distributed.At the same time,ultrasonic vibrations improve the flow rate of HDPE/Al composites,and reduces the apparent shear viscosity and die pressure.When the screw rotational speed was 5rmp and the ultrasonic intensity was 300W,the apparent shear viscosity decreased by 61%,while the die pressure reduced by 58%.Ultrasonic oscillations could improve crystallinity and decreased the lamella thickness of crystals.Ultrasonic vibrations could also significantly increase the thermal stability of composites. |
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