Some examples of polymers that may be used in the polymeric fiber-forming material include thermoplastic polymers containing polycarbonates, polyesters, polyamides, polyurethanes, block copolymers such as styrene-butadiene-styrene and styrene-isoprene-styrene block copolymers, and polyolefins such as polypropylene, polybutylene, and poly(4-methyl-1-pentene), or combination of such resins.