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Adhesion Behavior of Interface-controlled Metal-Polymer

Adhesion Behavior of Interface-controlled Metal-Polymer
Alternative Author(s)
Issue Date
2021. 2
Morphological and physical properties of twin-screw extruded polycarbonate/acrylonitrile-butadiene-styrene (PC/ABS) blends with various blend ratios are studied here. The needle-like co-continuous phase for PC-rich blends is changed to the sea-island phase for the blend ratios of more than 50 wt% of ABS content. While pure PC exhibits an almost Newtonian flow behavior, the PC/ABS blends show the interesting rheological transition. The viscosities of the blends increase as the amount of ABS increase. At low frequency levels under 0.1 rad/s, the viscosity of the material with a blend ratio of 3:7 (PC:ABS) is higher than that of pure ABS polymer. As the temperature increased, the viscosities of ABS-rich blends increased rather than decrease, whereas PC-rich blends exhibit decreases in viscosity. At the frequency of 10 rad/s, the PC-rich blends exhibit high viscous properties, whereas the ABS-rich blends present high elastic properties as the temperature increases. Results from the time sweep measurements indicate that ordered structures of PC, and the formation and breakdown of internal network structures of ABS polymer occur simultaneously in the blend systems. Newly designed sequence test results show that the formations of internal structures between PC and ABS polymers are dominant at low shear conditions, and effects of structural change and the presence of PBD become dominant at high shear conditions. The results of yield stress and relaxation time for PC/ABS blends support this phenomenon. The specimen with a blend ratio of 3:7 exhibit the highest value of yield stress at high temperature among others, which implies that the internal structure become stronger at higher temperature. Moreover, the ABS polymer in the PC/ABS polymer blend induces the significant change at the fracture surface of PC from brittle to ductile, which brings about the excellent increase in impact strength even though only addition of small amount of ABS. Electroplating is one of the economic decorative technologies for metallization of polymer substrate. Plating on plastic (POP) process was implemented on acrylonitrile-butadiene-styrene (ABS) at diverse etching conditions. Mechanical interlocking structures induced from the characteristics of anchor holes were built up between metal and polymer. Sa value, the extension of arithmetical mean height from the line to the area, and Sdr value, developed interfacial area ratio were adopted to quantify the surface profile instead of conventional linear roughness factor, Ra. At more than 15 min of etching time, the failure mode was changed from the adhesive to the cohesive, and the peel-off strength of metal-plated ABS exhibited the similar tendency to the tensile strength of ABS. The peel-off strength of electroplated ABS specimens increased to 8.46 N/cm at 30 min of etching time, but the metal layer did not fill up the anchor holes completely, and the inner voids were observed at the interface. The high injection molding rate led to the deformation of anchor holes, which caused the decrease in peel-off strength. The etched surface of the parting line formed by packing pressure on the mold did not exhibit anchor holes but show only collapsed morphology. PC/ABS blend is also one of the successful materials which can be applied to electroplating. As the content of ABS in the blend increased, the morphology of etched surface exhibited a number of rougher and deeper anchor holes. For the corresponding backside of metal layers, the surface did not show remarkable change of appearance over the ABS content of 70 wt%, and this phenomenon was also observed in the case of increasing etching time. The Sa and Sdr values of etched PC/ABS blend recorded higher with increasing ABS content and etching time, whereas those of metal layer represented difference in the degree of elevation. The adhesion strength of electroplated PC/ABS was increased at the larger amount of ABS in the blend. The Sdr of polymeric substrate after etching was divided by Sdr of plating layer, and newly suggested surface parameter, Sdr, polymer/Sdr, plating, was used to predict the tendency of adhesion strength of electroplated PC/ABS blend. The four types of inorganic fillers, needle-like whisker, plate shaped talc, spherical kaolin and CaCO3, incorporated PC/ABS composites were studied. The anisotropic fillers enhanced the mechanical properties of PC/ABS, whereas isotropic fillers did lesser increment. The dynamic viscosity curves of PC/ABS composites exhibited that rod-like whiskers are prone to be oriented in shear conditions, which led to lower viscosity than neat PC/ABS as shear rate increased. This phenomenon was more noticeable at the composite with larger amount of filler. The etched surfaces of PC/ABS with spherical fillers showed higher values of Sa and Sdr than those of PC/ABS composites using whisker and talc. The incorporation of spherical fillers brought about synergistic increase in adhesion strength of electroplated PC/ABS.
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