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/m.sup.2/24 hr. at 50% relative humidity and 23° C. and a hydrostatic head of at least 55 cm. In one embodiment, the nonwoven substrate comprises a spunbonded nonwoven fabric formed of randomly disposed substantially continuous polypropylene filaments. The spunbonded nonwoven fabric is an area bonded fabric in which the filaments are bonded to one another throughout the fabric at locations where the randomly disposed filaments overlie or cross one another.

The present invention relates to new, improved or modified polymer materials, membranes, substrates, and the like and to new, improved or modified methods for permanently modifying the physical and/or chemical nature of surfaces of the polymer substrate for a variety of end uses or applications. For example, one improved method uses a carbene and/or nitrene modifier to chemically modify a functionalized polymer to form a chemical species which can chemically react with the surface of a polymer substrate and alter its chemical reactivity. Such method may involve an insertion mechanism to modify the polymer substrate to increase or decrease its surface energy, polarity, hydrophilicity or hydrophobicity, oleophilicity or oleophobicity, and/or the like in order to improve the compatibility of the polymer substrate with, for example, coatings, materials, adjoining layers, and/or the like. Furthermore, this invention can be used to produce chemically modified membranes, fibers, hollow fibers, textiles, and the like, for example, to produce polyolefin microporous battery separators or membranes having improved hydrophilicity or wettability, having crosslinking in the polyolefin which can improve the high temperature stability, and/or the like.

The present invention relates to new, improved or modified polymer materials, membranes, substrates, and the like and to new, improved or modified methods for permanently modifying the physical and/or chemical nature of surfaces of the polymer substrate for a variety of end uses or applications. For example, one improved method uses a carbene and/or nitrene modifier to chemically modify a functionalized polymer to form a chemical species which can chemically react with the surface of a polymer substrate and alter its chemical reactivity. Such method may involve an insertion mechanism to modify the polymer substrate to increase or decrease its surface energy, polarity, hydrophilicity or hydrophobicity, oleophilicity or oleophobicity, and/or the like in order to improve the compatibility of the polymer substrate with, for example, coatings, materials, adjoining layers, and/or the like. Furthermore, this invention can be used to produce chemically modified membranes, fibers, hollow fibers, textiles, and the like, for example, to produce polyolefin microporous battery separators or membranes having improved hydrophilicity or wettability, having crosslinking in the polyolefin which can improve the high temperature stability, and/or the like.

The present invention relates to new, improved or modified polymer materials, membranes, substrates, and the like and to new, improved or modified methods for permanently modifying the physical and/or chemical nature of surfaces of the polymer materials, membranes, or substrates for a variety of end uses or applications. For example, one improved method uses a carbene and/or nitrene modifier to chemically modify a functionalized polymer to form a chemical species which can chemically react with the surface of a polymer substrate and alter its chemical reactivity. Furthermore, this invention can be used to produce chemically modified membranes, fibers, hollow fibers, textiles, and the like.