This International Standard specifies a method for the determination of the apparent volatile-matter content in pre-impregnated yarns, tapes, mats (SMC) and fabrics. The method is applicable to all unidirectional and multidirectional fibre-reinforced prepregs and all thermosetting-resin matrices, unless otherwise specified in product specifications. If aramid fibres are used as the reinforcement, water absorbed by the fibres is eliminated with volatile matter at the test temperature. lt is therefore necessary to correct the volatile-matter content by subtracting the water content. The method does not apply to unimpregnated reinforcement fibres. NOTE 1 For products with a Polyester-resin matrix (UPI, the result will be lower than the real value.