THERMAL PROPERTIES Plastic fabric is susceptible to temperature changes It softens as temperature rises and become more rigid as temperature drops Resistance to low temperature may be controlled by varying the composition of the coating RESISTANCE TO FIRE Through the use of dif ferent additives plastic fabric can be rendered flame retardant The material used in the manufacture of Rocvent tubing will not sustain burning Rocvent ventilation material has been certified by Natural Resources Canada under CSA Certification 1 181 The ducting material also conforms to CANCSAM427M91 AGING Plastic fabric ages slowly Nevertheless even a material as strong as PVC will degenerate with the passage of time through the action of a series of dif ferent factors In all probability the ultraviolet radiation present in sunlight is the major factor This radiation acts on the PVC coating and causes brittleness The plastic will become discoloured and hydrochloric acid gas released in the process will begin to attack the substrate WELDABILITY Adequate adhesion between substrate and the plastic coating is of particular importance in the manufacture of tubing from plastic fabric The degree of adhesion must be adapted to reflect the other properties of the material to ensure that tensile strength is virtually identical to that of the material itself The grade of plastic fabric used in the Rocvent tubing and our purpose designed highfrequency welding equipment provides just such a result ABRASION RESISTANCE Abrasion resistance is determined by conducting a test in which a roller is rotated against a sample of fabric ASTM D 1 17555T Loads are applied to the roller in several ways and an account is taken of the number of roller revolutions that precede the exposure of the threads in the fabric Shear strength test for a welded joint ROCVENT INC MINE TUNNEL VENTILATION 11 wwwrocventcom