WHAT DOES SHOWERPROOF MEAN? Showerproof fabric is fabric that resists water. We could pour a glass of water over it and watch the liquid simply form beads and run off. But shower proof fabric allows water vapour to pass through it. Thus it is comfortable to wear.
METHOD OF PRODUCING SHOWER PROOFFABRIC There are several methods which can be used to obtain fabrics which are both breathable and waterproof. These can be divided into three groups:• Densely woven fabrics• Membranes• Coatings
DENSELY WOVEN FABRICS(PORE SIZE 10-31M) These fabrics are made from finest types of longest staple cottons, using low twist mercerized yarns, woven using an Oxford weave, which is a plain weave with two threads acting together in the warp. The fabric weight ranges from 170 to 295 gsm.
COTTON Until quite recently, most waterproofs and tents were made from special close-woven cotton. Most cottons for tents and jackets also have some form of treatment which helps them to shed water without absorbing too much. They need re-spraying from time to time with this. In general, cottons are comfortable to wear and hardwearing, but they tend to be heavy, especially when wet, their waterproof qualities are limited, they take a long time to dry out and they are liable to rot.
NYLON Most waterproofs and tents are nowadays made of nylon. Nylon fabrics are very light and strong, packing away into a small bundle. They can be coated in a variety of ways to render them either totally waterproof or breathable-waterproof. Nylon doesnt absorb much water and so takes very much less time to dry out than cotton. It is also resistant to rot. All in all, nylon is more practical for fieldwork. The problem for manufacturers with nylon fabrics is that they deteriorate when exposed to sunlight, and are weakened when coated with the various waterproofing treatments
MEMBRANES Membranes are extremely thin films made from polymeric material and engineered in such way that they have a very high resistance to liquid water penetration, yet allow the passage of water vapour. A typical membrane is only about 10 μm
DIFFERENT TYPES OF MEMBRANES1. Microporous membrane (pore size 3-0.11 μm) This if thin film expanded polytetrafluoroethylene (PTFE) polymer claimed to contain 1.4 billion tiny holes per square centimeter. These holes are much smaller than the smallest raindrops (2-3 μm compared with 100 μm ), yet very much larger than a water vapour molecule (40-10^- 6 μm ).
DIFFERENT TYPES OF MEMBRANES2.Hydrophilic membrane (pore size below 0.001μm) Hydrophilic membranes are very thin films of chemically modified polyester or polyurethane containing no holes. The polyester or polyurethane polymer is modified by incorporating up to 40% by weight of polyethylene oxide. The poly ethylene oxide constitutes the hydrophilic part of the membrane by forming part of the amorphous regions of the polyurethane polymer system.
COATINGThese consist of a layer ofpolymeric applied to onesurface of the fabric.Polyurethane is used as thecoating material. Likemembranes, the coatingsare of two types,microporous andhydrophilic. These coatingsare much thicker thanmembrane.
MICROPOROUS COATINGS (PORE SIZE 3-2 μ M) Microporous coatings have similar structure to the microporous membranes.
HYDROPHILIC COATINGS (PORE SIZE BELOW0.001 μM) The difference between micropous material and hydrophilic material is that with the former, water vapour passes through the permanent air permeable structure whereas the later transmits vapour by molecular mechanism involving adsorption- diffusion and desorption