Preferred microfibrous matrices are made from melt-blown thermoplastic polymeric fibers, such as polyolefins, particularly polypropylene, polyesters, particularly polybutylene terephthalate, and polyamides, such as nylon 66, where the fiber diameter is typically in the range of from about 1 to about 4 micrometers, typically having void volumes ranging from about 60 to about 90% and thicknesses in