Polyplastics Co., Ltd., a leading global supplier of engineering thermoplastics, has developed an innovative technology that improves metal-resin bonding of composite parts for the automotive and electrical/electronics industries.

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Direct metal-resin bonding is a process which uses metal insert molding. Metal parts and resins are firmly bonded by introducing molten resin through injection molding to metal parts which have already undergone sufficient surface treatment. Metal-resin composites deliver the properties of metals (high rigidity, electrical conductivity) and engineering plastics (low density, electrical insulation). However, while many factors (metal parts, resins, mold structures, injection molding conditions) have had an adverse effect and prevent stable bonding, Polyplastics has made progress with successful bonding. 

For metal surface treatments, Polyplastics’ Quick-10 (R) technology uses quick heating and cooling of inserted metals to produce direct metal-resin bonding with metal insert molding alone, without any special surface treatments for the metal side. Resins must exhibit properties such as interface infinity, surface transferability (flowability), and low shrinkage to produce good bonding.

A key resin component is an affinity improvement additive that gives the metal-resin interface improved compatibility and promotes maximum adhesion to the metal surface. Polypalstics’ metal adhesion grades include 1135MF1 and 940MA for PPS and PBT respectively. Other metal adhesion grades, 1150MF1 and 930MA, provide added functionality.

Polyplastics notes that mold temperature can have a strong effect on bonding. The company has devised optimum molding conditions to achieve good surface transferability and low mold shrinkage with a linear expansion rate close to that of metal.

Metal-resin bonding technology has been used in mobile device parts (mobile phones, tablets, digital cameras) and some auto-related parts.

For more information, visit 
https://www.polyplastics.com/en/support/joint/metal_resin/index.vm