1995 Volume 81 Issue 10 Pages 983-988
The effects of crystallinity on the formability and corrosion resistance of the polypropylene (PP) laminated steel sheets by melt-extrusion method were researched.
The crystallinity of the PP layer varies with the cooling condition. The crystallinity of the rapid cooling sample A (cooling rate was 100°C/s) was about 28%, while the slow cooling sample B (cooling rate was 2°C/s) was about 60%.
The laminated layer of the sample B became white appearance from impact shock and microcracks were observed. On the other hand, both the whitening and the microcracks were not observed on the sample A. After the corrosion resistance test with a surfactant solution, the high crystallinity sample B showed inferior corrosion resistance to the low crystallinity sample A. In addition, the mechanical properties of the PP layer remarkably changed with the crystallinity.
It was necessary to cool the PP laminated steel sheet quickly with a cooling rate of not less than 20°C/s at least in the range from 100°C to 50°C in order to restrict the crystallization of the laminated PP resin.