Material used in medical nonwovens:
Fibers
The fibers used in medical nonwovens can be classified in
natural and synthetic categories. The natural fibers used are wood-pulp, cotton
and rayon. Wood pulp is used for its obvious absorbency, bulk and low cost.
Cotton and rayon are good to be used directly on wounds. They have good
absorbency and make excellent nonwovens.
The reasons natural fibers make excellent medical nonwovens
are:
- They are highly absorbent of exudate and blood
- Excellent breathability
- Good aesthetic characteristics
- Easy launderability and can be sterilized
- Excellent dimensional stability and high operability
temperature ~ 175 deg C
- Biodegradable
- Excellent drape and conformability
- Good heat resistance
- Excellent water retaining capacity
- Nonallergenic and nonirritant fibers
The synthetic fibers mostly used in this application are:
polypropylene for its excellent rheological characteristics, hydrophobicity
which is desired in some systems where barrier properties are required, low
cost, bicomponent fibers which are widely used in thermal bonding and added
functionality and polyester when strength, mechanical properties and ease of
sterilization are of prime importance. Synthetic fibers also account for the products strength, solvent resistance, static dissipation and many other desirable properties.
The properties of synthetic fibers which are required in
many applications:
- Hydrophobicity: to be able to act as a barrier fabric
- Easy to process
- Cost effectiveness
- Better performance due to strength, low density
- Easy to dispose, not hazardous
Manufacturing Processes for Medical Nonwovens
Web Formation: The most popular techniques for medical nonwovens are spunbonding,
meltblowing and their composites (SMS) in specific end uses. Spunbonding is
used when more strong webs are needed. Spunbonded webs are strong in both
machine direction (MD) and cross direction (CD). They are soft, porous and
dimensionally stable. Spunbonding is mostly used for products like face masks,
head wears, shoe covers, bed linens and disposable clothing etc. Dry laying,
wet laying and carding are used for different web properties depending on web
thickness required, speed of bonding technique to be used etc. Carding is
adapted for lightweight web production for technical and hygienic products. Carding produces very high quality webs at very high speeds.
Bonding is carried out by many methods including thermal
bonding for synthetic fibers and their blends. Hydroentangling as the fastest
growing bonding technique is used explicitly in medical nonwovens for that
textile-like hand and feel that's desirable in products like gauzes, dressings,
hospital apparel etc.
Needlepunching finds application in bonding various fibers
or webs of medium thickness. Needlepunching is fast, effective and often chosen
technique for varied applications. It is also cost effective. Apart from all
these techniques, stitchbonding is also used. Chemical bonding is often used
for making elastic nonwovens.
