NEEDLE PUNCHED NONWOVENS | Mark Livingstone | SIT

1. INTRODUCTION

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The needlepunching industry is recognized as one of the most successful sectors within the textile realm worldwide [1]. It is a dynamic and diverse industry encompassing both natural and synthetic fibers.

2. PROCESS

The needlepunch process is demonstrated in Fig. 1. Needlepunched nonwovens are produced by mechanically orienting and interlocking the fibers of a spunbonded or carded web. This interlocking occurs through the repeated use of thousands of barbed felting needles that traverse into and out of the web.

Fig. 1: Needle punching process

The primary components of the needle loom, along with a brief description of each, include:

2.1 THE NEEDLE LOOM (Fig-2 a & b)

• The needle board: This is the base unit that holds the needles in place. The needle board fits into the needle beam to secure its position.
• The feed roll and exit roll: These drive rolls facilitate the web's motion as it passes through the needle loom.
• The bed plate and stripper plate: The web travels between these two plates. Each has holes corresponding to the needle arrangement, through which needles pass. The bed plate supports the fabric as it feeds through, and the stripper plate removes the fibers from the needle, allowing for continuous material advancement.

Fig. 2a: Needle loom

Fig. 2b: Needle penetration

2.2 THE FELTING NEEDLE

The selection of the correct felting needle can significantly impact the quality of the needle-punched product. The choice of gauge, barb, point type, and blade shape (pinch blade, star blade, conical) can provide the necessary edge in this competitive market (fig. 3).

Fig. 2: Types of needles

The gauge of the needle refers to the number of needles per square inch. Finer needles have a higher gauge, while coarser products typically utilize lower gauge needles. For instance, sisal fiber products may use 12 to 16 gauge needles, while fine synthetics might use 25 to 40 gauge needles [3].

The major components of a basic felting needle include:

• The crank: A 90-degree bend at the top that seats the needle in the needle board.
• The shank: The thickest part of the needle, fitting directly into the needle board.
• The intermediate blade: Used on finer gauge needles to enhance flexibility, typically found on 32 gauge or finer.
• The blade: The working section that penetrates the web and houses the vital barbs.
• The barbs: Critical for carrying and interlocking fibers; their shape and size can dramatically influence the outcome.
• The point: The needle's tip, which must be well proportioned to minimize breakage and maximize surface appearance.

The needle loom’s operational movement causes the needles to penetrate the fiber batt. Barbs engage fibers on their downward movement, pulling them to the depth of penetration. As the draw roll advances, the batt is realigned from a mostly horizontal to a nearly vertical configuration. Increased penetration generally results in greater web density and strength, as illustrated in Fig. 4 a & b. Excessive penetration, however, can cause fiber damage.

Fig. 4a: Needle Action - Schematic

Fig. 4b: Needle action

3. TYPES OF LOOMS

In the needlepunching industry, there are three fundamental types of needle looms:

1. The Felting Loom
2. The Structuring Loom
3. The Random Velour Loom

The felting looms, as described earlier, can contain one to four needle boards with needle access from the top, bottom, or both. These looms primarily interlock fibers to create flat, one-dimensional fabrics suitable for a diverse range of products, including industrial uses, geotextiles, automotive interiors, and home furnishings [2].

Structuring looms employ fork needles that deposit fiber tufts into lamella bars spanning the loom's entry and exit points (fig. 1). Depending on the fork needle's orientation, a ribbed or velour texture emerges (fig. 5). Common structures produced with these looms include carpets, automotive products, wall coverings, and marine applications.

Fig. 5: Structured needling

Random velour looms, introduced in the mid-20th century, manufacture velour surfaces. These products are isotropic, making it difficult to distinguish between machine and cross directions. Unique to this design is the bristle-brush and bed-plate system, where special crown or fork needles push fibers into a moving brush bed plate. This results in a non-linear appearance, perfect for molded applications. Random velour products have gained traction in European and Japanese automotive sectors, although they are yet to become widespread in the United States.

3.1 Machine variable:

The depth of penetration and puncture density are critical machine variables. The penetration depth is determined by factors such as the needle's three-sided shank length, the spacing between plate needles, the stroke height, and the angle of penetration. Greater penetration depth increases the fiber entanglement within the fabric due to the increased number of barbs at work.

The puncture density, defined as the count of punches on the web’s surface, depends on:

• The needle board density (Nd)
• The material feed rate
• The punching frequency
• The effective width of the needle board (Nb T)
• The number of processing runs

The puncture density per run can be calculated as follows: Edpass = [n*F] / [V*W], where n = number of needles within a needleboard, F = punching frequency, V = material feed rate, and W = effective needle board width. The overall puncture density for the needled fabric also considers the total number of runs and varies based on weight, density, and air permeability — all factors that influence the fabric's compactness.

4. APPLICATIONS

1. Tennis Court Surfaces
2. Space Shuttle Exterior Tiles
3. Marine Hulls, Headliners
4. Shoe Felts
5. Blankets
6. Automotive Carpeting
7. Automotive Insulation
8. Filters
9. Vinyl Substrate
10. Insulators
11. Primary Carpet Backing
12. Fiberglass Insulation Felts
13. Fiberglass Mats
14. Wall coverings
15. Composites
16. Blood Filters
17. Tennis Ball Covers
18. Synthetic Leather
19. Carpet Underlay Pads
20. Auto Trunk Liners
21. Interlinings
22. Papermaker Felts
23. Felts
24. Padding
25. Shoulder Padding
26. Ceramic Insulation
27. Kevlar Bullet Proof Vests

5. MARKET & PROSPECTS

In the U.S., the needlepunching sector has often been viewed as the underdog of the nonwovens industry, associated with slow, non-technical processes. Conversely, these perceptions are less prevalent in international markets, particularly in Asia. Many U.S. companies lack a comprehensive understanding of the needlepunching procedure and the potential market growth. The demand for needled felts, particularly for filtration, constitutes about 10% of total consumption, translating to approximately $400 million. Pacific Rim countries, including Korea, Taiwan, and Indonesia, are heavily investing in pollution control, thus enhancing the market for needled felt products [3].

Additionally, the needlepunched nonwovens sector is swiftly expanding in Latin America due to their extensive application in the automotive industry, which suggests significant growth potential [4].

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