chapter  12
16 Pages

- Fiber Webs

Wood ‹bers can be used to produce a wide variety of low-density, three-dimensional webs, mats, and ‹ber-molded products. Short wood ‹ber can be blended with a long ‹bers can be formed into ¯exible ‹ber mats, which can be made by physical entanglement, nonwoven needling or thermoplastic ‹ber melt matrix technologies. The three most common types of ¯exible mats are carded, airlaid, needle punched, and thermobonded mats. In carding, the ‹bers are combed, mixed and physically entangled into a felted mat. These are usually of high density but can be made at almost any density. Air-laid webs are made by laying down layers of wood ‹bers combined with a low melting thermoplastic ‹ber that is then passed through a heated chamber that melts the thermoplastic in the web. The heated web is then passed through calender rolls that press the melted ‹bers together with the wood ‹bers holding the web together. A needle punched mat is produced in a machine which passes a randomly formed machine made web through a needle board that produces a mat in which the ‹bers are mechanically entangled. The density of air-laid webs and needled mats can be

12.1 Webs and Mats ...................................................................................................................... 458 12.1.1 Forming Options .......................................................................................................460