Gordon Low black butyl rubber liners carry a lifetime guarantee. They are so confident in the quality of product due to the way it is produced. The vulcanisation process during manufacture means that the material differs from all thermoplastic products (i.e. PVC), in that its properties are not affected by varying temperatures. The product is chemically stable and always returns to its original dimensions after stretching. The cross-linked molecular structure gives Butyl rubber its unique properties. Ageing or changes in characteristics are negligible despite decades of exposure to the atmosphere, sunlight, UV radiation, chemical fallout, water or major temperature fluctuations. Butyl rubber contains no plasticisers or additives which can evaporate or be washed out over the years. The strength and elasticity of the membrane remain practically unchanged for decades, without shrinkage, brittleness, melting or cracking. The membrane is equally elastic, regardless of whether the temperature is -30°C or +120°C, and obviously all of these liners are manufacturer guaranteed fish and plant friendly.