| 摘要 |
A shingle formed from a base sheet, with a layer of polymer modified asphalt coating the top of the base sheet, and a layer of conventional oxidized asphalt, free from polymer additives, coating the bottom of the bas e sheet. Both layers preferably directly contact the strands of the base sheet for good adhesion. This improves the strength, flexibility and ultraviolet resistance of the shingle, while reducing the cost as compared with a shingl e which utilized only polymer modified asphalt, and in addition it increases t he stiffness of the shingle as compared with one using only polymer modified asphalt. |
