Study on seam performance of polymer-modified bituminous roofing membranes using T-peel test and microscopy

The aim of the study was to understand how the T-peel strength of heat-welded seams in polymer-modified bituminous roofing membranes depends on the welding method and on the material properties. Seam samples of ten different commercial products, three of Atactic Polypropylene (APP)-modified bitumen and seven of Styrene-Butadiene-Styrene copolymer (SBS)-modified bitumen, were prepared by different welding methods with different heating media, i.e. hot air or gas torch, welding speed and weight of pressure roller joining seams. The welding conditions were precisely controlled during the preparation, and the temperature in the seam sample was measured. T-peel tests were carried out at 23 degreesC and at -10 degreesC on specimens cut out from each heat-welded sample to measure the T-peel strengths. The fracture propagation during T-peel testing was studied visually. Some seam specimens were also studied using microscopy. In order to identify the material properties and differences in the material compositions influencing the seam strengths, each product was characterised by different chemical and thermal methods, which were described in recently published reports [1,2]. It was concluded that the choice of welding speed and pressure weight for the optimum design of welding machine should make reference to the thermal properties, such as specific heat, and to the rheological properties, such as viscosity.