Failure characterization of polypropylene block copolymer welded joints

The failure behavior of polypropylene block copolymer double-V welded joints was investigated. Joints were prepared using the hot-gas welding technique at varying gas temperatures in the range of 230-260 degrees C. Uniaxial tensile tests, fracture mechanics experiments, several microscopy techniques, and complementary FEM analysis were carried out to assess the quality of filler rods and welding interfaces. The developed interfaces were weaker than the parent material as a consequence of polymer chains segregation during the welding process. The hot-gas temperature had a marked effect on the failure behavior of the welds. The highest interface toughness was attained at the highest gas welding temperature used at which, polymer chains were able to quickly diffuse into the parent material enlarging the distance of penetration and hence the micro-deformation capability of the joint.