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Bonding of nonwovens - past, present and future: the history of nonwovens bonding goes back only 40 years; there continues to be great potential for future development.

Bonding Of Nonwovens--Past, Present And Future

the history of nonwovens bonding goes back only 40 years, there continues to be great potential for future development This month we are taking a look at the bonding processes currently being used in various nonwoven processes and products. It is interesting to note that the major portion of nonwovens made today uses technology, equipment and/or chemicals for bonding them that were developed in the last 40 years.

The first and original method of making nonwovens, known as "felting," has all but disappeared and needlepunching has replaced it. Needlepunching is the physical entanglement of fibers to transform them into a fabric and give them integrity. Most of us in the nonwovens business have probably never thought about the fact that the typical wovens and knits use this basic principle. They utilize the surrounding or adjacent fibers to secure the total of the fibers into a fabric. The twist (entanglement) in a staple or short fiber yarn holds the fibers together. The knit or woven structure of yarns form a fabric that is also an entanglement of sorts.

Not Like Wovens Or Knits

So how can we bond fibers into a fabric without using this entanglement of yarns like the wovens or knits? To review for a moment:

NONWOVEN BONDING SYSTEMS:

1. Adhesion

2. Chemical, Wet/Dry Additives

3. Heat-Air

4. Heat and Pressure

5. Needlepunch

6. Solvent

7. Sonic

8. Water/Air Entanglement

Adhesion bonding is the bonding that occurs in processes such as melt blown. Here polymers are melted and extruded into a fiber form. While the fiber is still tacky or sticky it comes in contact with other such fibers, which stick to each other, building a network or fabric-like structure.

In the Chemical category, we find the backbone of the nonwovens business that includes the use of a multitude of chemical formulations such as acrylates, acrylonitrile, butadiene, ethylene, vinyl acetate and vinyl chlorides. The chemical systems include saturation, print bonding, foam bonding and spray bonding methods.

Heat methods using air pressure or other alternatives are typically used with melt/adhesion type fibers or polymers. Here a thermoplastic is particularly melted to become sticky and bond to the surrounding fibers.

Needlepunching is the physical entangling of fibers using a barbed needle.

Solvent bonding can soften and make a fiber sticky so that it sticks to a similar or dissimilar fiber.

Sonics uses a different energy source to effectively heat or melt bond fibers together. It is separated from other types of heat bonding since the bond can be very different from the typical heat and pressure bond.

Water entanglement is often referred to as spunlace. Here a web of fibers is subjected to concentrated high velocity streams of water and/or air to entangle the fibers into a fabric.

There are other methods of bonding that are not included in the above categories because they are relatively small, non-commercial, isolated or unique to specific products. These include extrusion foam bonding, grafting and the like.

Taking The Past Into The Future

Bonding of fibers in nonwovens has continually evolved during the past 40 years and any student of history would suggest that it should continue to do so even at a decreasing rate. In any case it is important to remind ourselves of the basic principles of bonding one fiber to another in building the fabrics of the future.

The future will bring a variety of polymers in fiber form to offer variations in bonding. Natural fibers will also be available with new and different bonding characteristics. Sophisticated chemicals will be introduced to add to the already complicated list. Machinery and equipment will no doubt be developed that will enable the nonwovens manufacturer to run at higher speeds and lower costs. The combinations of these factors will change some current bonding concepts from "not viable" to "profitable." We will see a continuation of change in the bonding of nonwovens where more than one bonding method will become prevalent.

Tom Holliday is a well-known consultant to the nonwovens and textile industries whose column on a wide range of nonwovens-related topics appears every month in Nonwovens Industry. Mr. Holliday operates his consultancy firm, Thomas M. Holliday & Associates, out of his office at 25 Edgewood Road, Yardley, PA 19067; (215)493-2501.
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Article Details
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Author:Holliday, Tom
Publication:Nonwovens Industry
Article Type:column
Date:Oct 1, 1989
Words:716
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