sbs/app modified bitumen waterproof membranes The products are made by soaking the base in bitumen,or thermoplas ticiyelastomer (such as styrene butadiene-SBS),or thermoplastics (such as atactic polypropylene-APP,APAO.APAL)modifiled biumen,then covering double faces with wlastomer(SBS)or thermoplastics (APP,APAO,APAL)modified bitumen,and last..