Introduction
The most commonly used method to maintain sterility of surgical instruments in hospitals is the use of sterilization wraps. Initially, 140-thread count muslin cloth was used as sterilization wrap but since it was woven, it could not provide complete microbial protection. In 1960s, non-woven materials were brought into the market and they offered higher level of protection but lacked sufficient strength. The use of polypropylene wraps is a breakthrough as it possesses strength, barrier and repellant properties. Another fabric that is high in demand is Spunbound/Melt-blown/Spunbond (SMS). It consists of three thermally bonded layers where in spun bound provides sufficient strength and melt-blown acts as the barrier[4].
Polyolefins are the most commonly used resins for production of polymer-laid non-wovens[1]. They are categorized into :
a) Polypropylene (PP) and
b) Polyethylene (PE)
PP exists in three major forms:
a) Isotactic PP
In this polymer, the monomer units are placed head to tail. Hence, all methyl groups appear on the same side of the polymeric backbone. It possess good mechanical properties such as tensile strength and stiffness. It crystallizes in the form of a helix. Commercially, isotactic PP is the most commonly available and it is sold in the form of three different products : Homopolymer, block copolymer and random copolymer. Among the three types, homopolymer shows the highest stiffness and melting point. It also exhibits a wide range of Melt Flow Rates (MFR).
b) Syndiotactic PP
In this type of polymer, monomer units are arranged in an alternating manner. Stiffness of syndiotactic PP is low compared to isotactic type but it has more clarity and impact.
c) Atactic PP
This type of polymer is produced by random insertion of monomers. It is not as crystalline as the other two types. Atactic PP is mainly used for adhesive and roofing purposes.
The three main times of PE are: High Density Polyethylene (HDPE), Low Density Polyethylene (LPDE) and Linear Low Density Polyethylene (LLDPE)[1].
Polypropylene resin is more difficult to extrude than polyethylene owing to higher melting point and higher shear sensitivity of PP. Blue wrap is produced using polypropylene resin. It is used for wrapping surgical instruments for the purpose of sterilization.
The general characteristics required of a sterilization wrap are tabulated

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