Application of Technical Textiles in Everyday Life

Non-implantable materials used in Medical Textiles

These materials are used for external applications on the body and may or may not make contact with skin. They are made from a copolymer of two amino acids. They are employed as covering, absorbent, protective and supports for injured or diseased parts Table 4.2 illustrates the range of textile materials employed within this category, the fibres used, and the principal method of manufacture

Wound care

A number of wound dressing types are available for a variety of medical and surgical applications (Fig. 4.2). The functions of these materials are to provide protection against infection, absorb blood and exudate, promote healing and, in some instances, apply medication to the wound. Common wound dressings are composite materials consisting of an absorbent layer held between a wound contact layer and a flexible base material. The absorbent pad absorbs blood or liquids and provides a cushioning effect to protect the wound. The wound contact layer should prevent adherence of the dressing to the wound and be easily removed without disturbing new tissue growth. The base materials are normally coated with an acrylic adhesive to provide the means by which the dressing is applied to the wound.

Developments in coating technology have led to pressure-sensitive adhesive coatings that contribute to wound dressing performance by becoming tacky at room temperature but remain dry and solvent-free. The use of collagen, alginate and chitin fibres has proved successful in many medical and surgical applications because they contribute significantly to the healing process. When alginate fibres are used for wound contact layers the interaction between the alginate and the exuding wound creates a sodium calcium alginate gel. The gel is hydrophilic, permeable to oxygen, impermeable to bacteria, and contributes to the formation of new tissue. Other textile materials used for wound dressing applications include gauze, lint, and wadding.

Gauze is an open weave, absorbent fabric that when coated with paraffin wax is used for the treatment of burns and scalds. In surgical applications gauze serves as an absorbent material when used in pad form (swabs); yarns containing barium sulphate are incorporated so that the swab is X-ray detectable. Lint is a plain weave cotton fabric that is used as a protective dressing for first-aid and mild burn applications. Wadding is a highly absorbent material that is covered with a nonwoven fabric to prevent wound adhesion or fibre loss. It can be used as it is for absorbency or coated with paraffin wax for the treatment of burns and scalds. Gauze with paraffin coating is easier to be removed from the wound after use.

Types of Wound Care

• PRIMARY WOUND DRESSINGS: Placed next to the wound surface. Nonwoven with a binder content of 60% and made from cellulose fabrics are being used.
• ABSORBENT: Similar to wound pads used in surgery. Manufactured from well-bleached, carded and cleaned cotton fabrics
• BANDAGES: These are narrow cotton or linen, plain weave cloth of low texture, either woven or knitted. Ex: Plaster of Paris Bandage, orthopaedic bandage, crepe Bandage.
• PROTECTIVE EYE PAD: Scientifically shaped 2 ¾” x2 ¾ x to lit over the eye used in the outpatient clinic and industrial medical department.
• ADHESIVE TAPES: It is narrow, plain weave fabric having a coating of adhesive paste. It is used with other pads to conform them to the injury.

 

Bandages

Bandages are designed to perform a whole variety of specific functions depending upon the final medical requirement. They can be woven, knitted, or nonwoven and are either elastic or non-elastic. The most common application for bandages is to hold dressings in place over wounds. Such bandages include lightweight knitted or simple open weave fabrics made from cotton or viscose that are cut into strips then scoured, bleached, and sterilised. Elasticated yarns are incorporated into the fabric structure to impart support and conforming characteristics.

Knitted bandages can be produced in tabular form in varying diameters on either warp or weft knitting machines. Woven light support bandages are used in the management of sprains or strains and the elasticated properties are obtained by weaving cotton crepe yarns that have a high twist content. Compression bandages are used for the treatment and prevention of deep vein thrombosis, leg ulceration, and varicose veins and are designed to exert a required amount of compression on the leg when applied at a constant tension. Compression bandages are classified by the amount of compression they can exert at the ankle and include extra-high, high, moderate, and light compression and can be either woven and contain cotton and elastomeric yarns or warp and weft knitted in both tubular or fully fashioned forms.(Fig 4.3)

Orthopaedic cushion bandages are used under plaster casts and compression bandages to provide padding and prevent discomfort. Nonwoven orthopaedic cushion bandages may be produced from either polyurethane foams, polyester, or polypropylene fibres and contain blends of natural or other synthetic fibres. Nonwoven bandages are lightly needle-punched to maintain bulk and loft.

Fig 4.3 Different types of bandages and their application.

(a) Elasticated flat bandage, (b) tubular finger bandages, (c) tubular elasticated net garment, (d) tubular support bandages,(e) and (f) orthopaedic casting bandage, (g) pressure gloves, (h) pressure garment, (i) hip spica, (j) lumbar/abdominal support, (k) anti-embolism stockings.

Products Used for Medical-Surgical Dressings

Wound care products

A wound dressing is used for many purposes including protection against infection, absorption and exudation of blood and excess fluids, healing and application of medication ideally a wound dressing should be soft pliable pad the wound to protect it from further injury, be easily applied and removed, be sterile lint-free and non – toxic. The wound dressing should not adhere to the wound allowing easy removal without disturbing new tissue growth. An absorbent cotton swab placed at the wound and tied with gauze forms the oldest form of the wound dressing. However, this traditional method of wound covering is found to stick to the wound and does not provide a moist microclimate to the wound conducive to its faster healing.

The modern wound dressing is usually made of three layers

• Wound contact layer: It should not stick to the wound or cause maceration of the skin if the dressing is not changed. It can be woven, knitted or non-woven made from silk, viscose, polyamide or
• Middle absorbing layer: If has to absorb blood or liquids while providing a cushioning effect to protect the wound. It is generally non-woven composed of cotton or
• Base Material: It provides a means by which the dressing is applied. The material is coated with acrylic adhesive to hold the dressing in place, eliminating the need for a bandage.

Because sterilization is a major concern for surgical dressings, nonwovens are considered. Nonwovens can be smooth and lint-free for the most part. This allows a lesser chance for debris to be left at the wound. Nonwoven can be made softer and more absorbent by latex or thermal calendaring. For the post-operative dressing, sophisticated nonwoven structures such as perforated films on absorbent base, polymers/nonwoven welded laminate and metalised nonwoven are used.

Polypropylene is promoted as the most unwettable fibre, but it can also be quite wettable if converted to a fibrous web by melt blowing. In melt blowing a stream of molten polymer is subjected to blasts of air which form tiny fibrils that fall randomly as a web. This gives polypropylene a role of absorbable dressing’s material. Traditionally polypropylene is used in wound dressings in fibre or fabric form, coupled with absorbent material. Polysaccharide based dressings have increasingly become a viable alternative to biologically incompatible and often problematic cotton and viscose gauzes used for wound dressings.

Abundantly available alginates and their relative ease of solubility, in particular, have been instrumental in developing these fibres and their applications as vehicles for drug delivery. The other polysaccharide is Branan ferulate which is gel spun. It is extracted from corn bran and has water-soluble properties. This polysaccharide can infiltrate the biological activities in the body and hence accelerate wound healing.

Types of Bandages

Bandages are designed to perform a whole variety of specific functions depending upon the final medical requirement. They can be woven, knitted, non – woven or composite in structure. They can be classified into various classes depending upon the function they serve as.

• Simple bandages – These are fixation bandages that can be elastic or inelastic in nature. Adhesive bandages, cohesive bandages and tubular bandages belong to this class. A simple non–elastic bandage is required to the dressing in the proper place over the wound. One such bandage is simple, open weave cotton or viscose fabric cut into strips that have been scoured, bleached and sterilized. The problems of fraying in the plain-woven bandage are overcome by the use of non-fraying cotton leno The structure of the bandage is more stable with crossing warp threads in the leno woven structures. These can be further coated with paraffin to prevent sticking
• Light support bandages – Woven light support bandages are used for sprains or strains. Elastic crepe bandages are used for sprained wrist or ankle support. The elasticated properties of these bandages are obtained by weaving cotton crepe yarns that have twist content. Similar properties can also be achieved by a combination of two warp sets with normal and high tension. Stretch and recovery properties of these bandages apply sufficient tension to support the sprained
• Compression bandages – Compression bandages are used to exert a certain compression for the treatment and prevention of deep vein thrombosis, leg ulceration and varicose Depending upon the compression they provide, compression bandages are classified as light, moderate, high and extra–high compression bandages. They can be woven, warp or weft knitted from cotton and elastomeric yarns.
• Orthopaedic bandages – These bandages are used under plaster casts and compression bandages to provide padding and prevent discomfort. Non–woven orthopaedic cushion bandages are made from polyester or polypropylene and blends of natural and synthetic fibres. Polyurethane foam can also be used. Light needle punching gives bulk and left to the structure for greater cushioning

Two main types of fabrics are currently used for making pressure garments.

• Firm elastic fabric containing elastane yarns is used for making pressure This fabric is usually warp-knitted. Tubigrip is a circular weft knitted cotton fabric with rubber yarn laid–in, tubular lengths of different diameters. Since these garments are to be continuously worn, the seams should be strong enough to resist strong transverse forces. Also, the seam should have high extensibility and recovery to allow for body movement. In the various suitable fabric structures and garment constructions, the following have been established:
• Fabrics with a low coefficient of friction are more comfortable than those with a high coefficient of friction and are less likely to cause maceration. Hence, Powernet, sleekit fabrics are found to be more suitable as compared to weft or warp knit fabrics. However, the deviation in the coefficient of friction was found to be quite high for almost all fabrics. The face side of all fabrics was rougher than the reverse Hence an optimum construction is to be arrived at for comfort and recovery of the patient.

Gauze

Gauze and paraffin coated gauzes are the most commonly used dressing. Most gauze is made up of cotton in the form of a loose plain weave. The typical yarn density per inch is 12 – 19 for warp and 8 –15 for the weft. 44sNe warp and 54sNe carded weft yarn is generally used. Gauze is mostly used as a direct dressing for wounds or may be used in internal pads and general swabbing applications. The burns and skin grafts have their dressings changed frequently and the difficulty with this gauze is that its fibres stick to the wound. The removal is not only painful but also destroys the regenerating tissues. This leads to delay in the healing process and also leaves scars behind. The problems associated with the traditional woven cotton gauze are as below:

• A possibility of loose fibres getting caught in the wound
• A large adherence surface
• Irritation or mechanical injuring of the wound when the dressing is
• Prolonged time of wound healing
• Paraffin–coated gauze is usually multi-layered, is a little easier to remove, but it does not rapidly absorb the wound liquids. Also, this being a petroleum-based coating can liquefy at body temperature and introduced foreign matter into the wound. It is used to treat burns and

Plasters

Plasters are made up of three layers

1. Plaster fabrics
2. Adhesive and
3. Wound pad. A simple plaster cast consists of gauze impregnated with plaster of Paris. The modern plaster fabric is made from spun bonded nonwovens of cotton, viscose, polyester or glass fibre. The adhesive used for plaster fabric is acrylic that doesn’t stick to the skin. The cushioning wound pad is made from knitted viscose fabric impregnated with an antiseptic. The highly absorbent wound pad helps in the rapid absorption of secretion from the wound.

Others Dressings

The other surgical dressings include wadding and lint. Wad – ding is an absorbent material to prevent adhesion to wound or fibre loss, it is covered with a non–woven fabric. Lint is a plain weave cotton fabric that is frequently used in the treatment of mild burns.