Estimation of Slow Crack Growth Behavior in Polyethylene after Stepwise Isothermal Crystallization

The use of analytical methods to estimate the SCG resistance of PE pipe materials has been suggested due to the fact that the slow crack growth (SCG) behavior of polyethylene (PE) is governed by structural parameters such as molecular weight and side chains. In the research project presented here, the molecular structure of several commercially available polyethylene-high density (PE-HD) materials was analyzed using a modified stepwise isothermal segregation (SIS) technique and compared with results from fracture mechanics experiments. A good correlation between the SIS results and SCG rates was found. It turned out that the modified SIS technique is a fast and simple method and could be used to assess SCG resistance in PE.     

Investigation of dislocation kinetics in α-Fe monocrystals with the help of etching technique

Results of the etching technique concerning dislocation arrangements in regions near the surface are introduced after tribomechanical loading on (001) surfaces of α-Fe-monocrystals. Moreover, the load stress field related to the critical shear stress is calculated and discussed. For the etching of grown in and newly developed dislocations a solution of 2% nital was used.