| 摘要 |
<p>The core layer of a face mask for air filtration is made from a moulded layer of fibres which have been contracted into coiled or looped profiles by thermal relaxation. The interstices within the fibre structures trap much finer particles than those caught by a regular or irregular lattice structure made of relatively straight fibres of similar filament dia. Pref. the contracted fibres are made from fibres produced by fibrillation of laminated films of dissimilar materials, specifically a layer of propylene film with a layer of ethylene/ propylene co-polymer film or of high density polyethylene. Alt. claims use of fibres from laminates of ethylene/propylene copolymer film with a film blend of ethylene/vinyl acetate copolymer and polypropylene. Pref. the films are contracted into helical form and then matted and moulded with superficial fusion. Opt. the fibres are loaded with an absorbant filler such as activated carbon, prior to contraction to trap at least some of the filler particles. Pref. a mat 4mm thick, weighing 420g/sq.m. of dtex contracted fibres, is enclosed between covers made from 8-20 dtex polyolefin fibril fibres and moulded so that the covers and the core have different curvatures, to minimise interfacial contact.</p> |
