Abstract: A nonwoven fabric is provided having a plurality of semi-crystalline filaments that are thermally bonded to each other and are formed of the same polymer and exhibit substantially the same melting temperature. The fabric is produced by melt spinning an amorphous crystallizable polymer to form two components having different levels of crystallinity. During spinning, a first component of the polymer is exposed to conditions that result in stress-induced crystallization such that the first polymer component is in a semi-crystalline state and serves as the matrix or strength component of the fabric. The second polymer component is not subjected to stress induced crystallization and thus remains in a substantially amorphous state which bonds well at relatively low temperatures. In a bonding step, the fabric is heated to soften and fuse the binder component. Under these conditions, the binder component undergoes thermal crystallization so that in the final product, both polymer components are semi-crystalline.

Abstract: A moisture vapor permeable, water impermeable composite sheet material is provided which is suitable for use as a housewrap material, and is also useful for other applications such as tarpaulins, or as covers for automobile, boats, patio furniture or the like. The composite sheet material includes a nonwoven substrate and an extrusion-coated polyolefin film layer overlying one surface of the substrate. The nonwoven substrate is comprised of polymeric fibers randomly disposed and bonded to one another to form a high tenacity nonwoven web. The nonwoven substrate has a grab tensile strength of at least 178 Newtons (40 pounds) in at least one of the machine direction (MD) or the cross-machine direction (CD). The extrusion coated polyolefin film layer is intimately bonded to the nonwoven substrate. The film layer has micropores formed therein to impart to the composite sheet material a moisture vapor transmission rate (MVTR) of at least 35 g/m2/24 hr. at 50% relative humidity and 23° C.