Glues are necessary in the dry production processes, as well as in lamination to thicker elements. Polyurethane glue is much used, as well as melted fibres (thermal bonding) of polyolefine, polyester and maize starch, in quantities 4-18%. In the wet process 8-22 % bitumen is often added for water resistance; it also acts as additional adhesive. Phenol-resorcinol-formaldehyde (PRF) glue is then often used together with the bitumento the extent of1-2%. For lamination common adhesivesare poly vinyl acetate (PVAC) and waterglass glue, again typically 1-2%.
Fire retardants are used in most of these products.Common are whey, borates,am-monium sulphates and phosphates, and cement. Whey counteracts fire by releasing nitrogen when heated. Ammonium sulphates and phosphates release ammonia and water, borates release water. Cement being a mineral material is incombustible. Extent of fire retardants vary from 5-25 %.
Anti fungal agents are added to some products.This can be soda waterglass cement, aluminium sulphate (alum) and borates. The effect of soda waterglass and cement is to increase the alkalinity of the product.
Water repelling additives are for products to be used in exposed or humid conditions, especially products for the exterior sheathing of buildings.They include bitumen, para/in wax, colophony and latex. Often several of these are used in combination.
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