Study On Adhesive Strength Of Molded Composites Of Nano Molding Technology

Nano molding technology(NMT),one of polymer-to-metal direct molding technologies,has been developed as an innovation in recent years.This technology requires the surface treatment,which is able to form nano-scale mesh-shaped structures on the surface of metal specimen firstly.And then nano-scale mechanical interlocking between thermoplastic polymer and metal is built on the interface after polymer is injected into these structures.The adhesive strength of composites and the retention capacity of the strength are the key points for this technology.In order to find a way to increase the adhesive strength,the relationship between injection molding parameters and adhesive strength was researched by studying on the polyphenylene sulfide(PPS)–metal(steel,aluminum alloy)composites produced by nano molding technology.The four process parameters,which are identified with metal surface temperature,polymer melt temperature,injection speed and packing pressure,were mainly considered.Adhesive strength was measured and the orthogonal experimental method as well as the scanning electron microscope(SEM)were conducted to evaluate the effect of each parameter on adhesive strength.The results were shown that metal surface temperature is the most significant positive factor on strength,while injection speed has the most limited effect.Annealing process effectively increased the adhesive strength of composites,which is raised by about 15%with conditions of 200℃ and2hours.In addition,in order to study the correlation between aging conditions and the retention of adhesive strength,4 groups of PPS-steel composites were respectively placed at-20℃,23℃,90℃,130℃ for a duration of 497 hours,and the strength of each specimen was measured.By comparison with the initial value of strength,the results showed that the strength was 3.48%decreased at the-20℃,2.86%increased at 23℃,6.21%increased at 90℃ and 10.83%increased at 130℃.The adhesive strength of PPS-steel composites didn’t decrease much generally.It indicates that PPS-steel composites have the excellent aging resistance performance under the given conditions in this experiment.This also shows the finished parts made by NMT have mechanical stability and a long lifetime----a guarantee of NMT promotion and development.