Abstract
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°C and at −10°C 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.
Résumé
Le but de cette étude était de déterminer l'influence exercée par la méthode de soudage et les caractéristiques du matériau sur la résistance au «T-peel test» des joints soudés à chaud des lés d'étanchéité de bitume polymère (LBP) pour toitures.
Des éprouvettes de joints soudés de dix produits commerciaux, trois à base de bitume modifié par du polypropylène atactique (APP) et sept à base de bitume modifié par un copolymère styrène-butadiène-styrène (SBS), ont été confectionnées avec différentes méthodes de soudage utilisant des agents de chauffage divers, air chaud ou torche à gaz, ainsi que des vitesses et des pressions de soudage différentes. Durant la confection des éprouvettes, on a contrôlé avec précision les conditions de soudage et on a procédé à la mesure de la température des éprouvettes.
Les «T-peel tests» ont été effectués à 23°C et à −10°C sur des éprouvettes de chacun des joints soudés afin de mesurer leur résistance au ‘T-peel test». La propagation des fissures a été examinée visuellement. Sur certaines éprouvettes de joints soudés on a également procédé à un examen microscopique.
Afin de déterminer les caractéristiques et les différences de composition du matériau exerçant une influence sur la résistance des joints soudés, chaque produit a été caractérisé au moyen de différentes méthodes d'analyse chimique et thermique qui sont décrites dans les rapports [1,2] précédemment publiés.
Les conclusions de cette étude sont que le choix de la vitesse de soudage et de la force de pression pour le réglage optimal de la machine de soudage devraient s'effectuer en fonction des caractéristiques thermiques, telles que la chaleur spécifique, et de caractéristiques rhéologiques, telles que la viscosité des lés d'étanchéité de bitume polymère.
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Oba, K., Hean, S. & Björk, F. Study on seam performance of polymer-modified bituminous roofing membranes using T-peel test and microscopy. Mat. Struct. 29, 105–115 (1996). https://doi.org/10.1007/BF02486200
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DOI: https://doi.org/10.1007/BF02486200