Seams for Protective Clothing–An Overview

16 World Journal of Textile Engineering and Technology, 2017, 3, 16-23 Seams for Protective Clothing–An Overview

Shanthi Radhakrishnan1,* and Devendra Kumari2

1Department of Fashion Technology, Kumaraguru College of Technology, Tamil Nadu, India 2VCMM Arts and Science College for Women, Tamil Nadu, India Abstract: Specialized clothing is essential for protection against specific environments like fire, heat, cold, chemical, mechanical and biological in nature. Specialized clothing that has been designed and fabricated to face the challenges of these environments is Protective Clothing which is a combination of technical design and functional focus. Seams are most important structures that help to keep a garment intact; they must be strong and have many qualities to hold the garment together in extreme conditions. The type and nature of thread, the model of seam construction and the testing of seams are important for the performance of protective clothing as one loose thread or gap in seams can unravel the space between the person and the environment leaving the person vulnerable. Seams for protective clothing play a critical role since they directly affect the integrity of providing protection, leading to death of the individual. In this paper the different seam construction methods used for protective clothing is being analyzed. Keywords: Protective clothing, specialized environment, ultrasonic seams, seam taping and glueing.

1. INTRODUCTION textiles, medical protective textiles, sports protective textiles and space protective textiles. Personal Protective clothing comes under the technical textile protective textiles can be further classified according to category or products. While all clothing is protective to the end-use functions such as thermal (cold) some degree, concern is not with routine needs, such protection, flame protection, chemical protection, as clothing for warmth, rainwear or routine work mechanical impact protection, radiation protection, clothing. The focus today is on more sophisticated biological protection, electrical protection and wearer needs, protection in situations where hazards or risks visibility [2]. Examples of protective clothing for different are present that have the potential to be life threatening end users are given in Figure 1. or pose considerable potential for injury or damage to the person working in and around the hazard. In some 2. CONVENTIONAL SEWING cases, such as clean rooms, the concern is about Modern day sewing machines are highly automated protecting the product as well as the worker. Many of and programmable and can form seams at very high the new advanced "high-tech" fibers and fabrics are speeds. However, the basic mechanism of stitch used in protective clothing. Conventional materials formation remains similar to that created during the late such as nylon and polyester, cotton and wool, are also nineteenth century- that of interlacing threads through used and provide satisfactory protection in certain or around textile materials. Stitch formation involves the applications - depending on the hazard or exposure. carrying of needle thread to the reverse side of the When new fibers with unique properties are being fabric, where it is interlaced or interlooped with the developed, they are often considered for protective under threads. The process is made continuous by a clothing [1]. mechanism that feeds the material over a defined distance, through the needle head. When a stitch is Classifying personal protective textiles is used with a defined geometry of fabric positioning, a complicated because no single classification can seam is formed [8]. Standard classification of stitches clearly summarize all kinds of protection. Overlap of the and seams is available in international standards, as definitions is common since there are so many given below: occupations and applications that even the same class of protective clothing often has different requirements • ISO 4915, 1991-08 (Stitch types -classification in technique and protection. Depending on the end use, and terminology). personal protective textiles can be classified as • ISO 4916, 1991-09 (Seam types -classification industrial protective textiles, agricultural protective and terminology). textiles, military protective textiles, civilian protective • BS 3870 Part 1 (Stitches and seams - classification and terminology of stitch types).

*Address correspondence to this author at the Department of Fashion Technology, Kumaraguru College of Technology, Tamil Nadu, India; Tel: +91 • BS 3870 Part 2 (Stitches and seams - 9894607690; Fax: 0422-2669406; E-mail: [email protected] classification and terminology of seam types) [9].

(a) (b) (c) (d) (e) Figure 1: Types of Protective Clothing based on end use: (a) Chemical protective suit (b) Cold protective suit (c) Biological Protective suit (d) Mechanical Protective Suit (e) Fire and Heat Protective suit [3-7].

3. SEAMS FOR PROTECTIVE CLOTHING and defense protective clothing are discussed CATEGORIES herewith.

Seams are very important in the case of any type of 3.1. Seams for Chemical Protective Clothing apparel or clothing. It serves the function of converting a two dimensional cut fabric into a three dimensional Seams may also be bound or reinforced with other garment. In the case of protective clothing they must material pieces such as additional fabric or tape or also serve the function of resistance to the even covered with a top coating of a polymer. The type environmental features which might cause harm to the of seam and how it is applied is usually affected by the human body. Based on the end use, the seams used material used in garment construction and the intended for protective clothing are Serged Seam, Sewn and integrity or performance of the chemical protective Bound Seam and Heat Sealed Seam. Serged seams clothing [2]. Different types of seam constructions can are used for a dry environment, sewn and bound be used in protective clothing categories such as seams are used for light liquid background and heat serged seam, bound seam, sewn seam with tape seal sealed seams for liquid splash and as a barrier to on one side, sewn seam with tape seal on both sides, chemical environment, as expressed in Figure 2. The glued and sealed seams. However, lap or fell seams seams suitable for chemical protective clothing, are also used in the fabrication of some Protective medical protective clothing, protective clothing against Clothing. cold weather, protective clothing against fire and heat

(a) (b) (c) Figure 2: Seam Types for Special Environments: (a) Dry Environment (b) Liquid & Chemical Environment (c) Light Liquid. 18 World Journal of Textile Engineering and Technology, 2017, Vol. 3 Radhakrishnan and Kumari

in Figure 4(a). Apart from serged seams, lap or fell seams may also be used. 3.1.2. Bound Seam Stitched seams produces stitched holes that provides a path to chemical penetration. The bound seam limits the pathways for chemical penetration as the seam is wrapped with a folded strip of similar or stronger material and chain-stitched through all five layers in a single operation. These operations result in a tougher seam which also provides improved liquid and particle repellency at the seams as well as a tougher garment all round. A bound seam is not suitable for a chemical suit as it is not liquid tight. Figure 4(b) shows the bound seam. Figure 3: Seam Construction for Chemical Protective 3.1.3. Stitched and Taped Seam Clothing [10]. The seam is first stitched and sealed on the outside The seam types for chemical protective clothing with a heat activated tape. This results in an impervious include. (Figure 3) seam which is completely liquid-tight. As these seams are generally used for chemical suits the tape type is 3.1.1. Serged Seam often constructed from a similar material to the garment fabric in order to maintain similar chemical permeation A serged seam joins two pieces of material with a properties. When the heat sealing is done on both thread that interlocks. This is an economical stitching sides with a heat activated tape the seam becomes method for general applications. This stitching method fully impervious and is considered to be the strongest is generally not used for all types of chemical protective seam for gas-tight suits e.g. Interceptor [14]. Figure 5 clothing. It is more commonly found on limited use in shows the flat felled seam (LSc -1) with heat sealing dry particulate protective clothing where dry particles tape on one side (5a) and heat sealing tape on top and are of concern. An example of a serged seam is given bottom sides of seam (5b).

(a) (b) Figure 4: (a) Serged seam EFd; (b) Bound seam BSa-1 [11 & 12, 13].

(a) (b) Figure 5: Stitched and taped seam: (a) Stitched & Single Taped Seam; (b) Stitched & Double-Taped Seam [11, 15]. Seams for Protective Clothing–An Overview World Journal of Textile Engineering and Technology, 2017, Vol. 3 19

3.1.4. Glued Seam used to activate the adhesive in the films which creates c Adhesive films like Sewfree are being used to a bond between the adjoining fabrics. Gluing is usually replace stitches for seams. Primarily components of performed for coated fabrics and unsupported rubber garments namely pockets, zippers, darts, pleats, materials; the woven fabric is coated with rubber or hemlines were constructed using glued seams. Hems plastic on one or both sides of the fabric. Some of the materials include PVC/Nylon, Polyurethane Nylon, and plackets are also being glued to provide a clean look, eliminate the use of seam tape and prevent water Neoprene/Nomex and Butyl/Nylon [16]. The method of leakage in the used areas e.g. Hems, pocket flaps or layering the materials for a glued seam is shown in cuffs. The purpose of glueing in garments is to provide Figure 6. significant improvements in garment weight, softness, 3.1.5. Sealing breathability and comfort. Heat and pressure may be Sealing is applied to materials where the surface can be melted to create a bond with the surface of another material as shown in Figure 7a. This seaming approach is used for plastic laminates, thermoplastics, and other film-based materials2. Sealing can be accomplished by using ultrasonic welding machine, Radio Frequency Welding, hot air welding, hot wedge welding, Laser Welding and Bonding Technology [9]. The equipment used for welding and hot wedge (a) (b) welding are shown in Figure 7(b) and (c). Ultrasonic Figure 6: Glued Seam: (a) Material layering for glued seam; technology involves the creation and channeling of high (b) Coated fabrics [17]. frequency vibratory waves that cause rapid heat to

(a) (b) (c) Figure 7: (a) Sealing method, (b) Welding equipment, (c) hot wedge welding equipment [9].

(a) (b) (c) Figure 8: (a) Seamsonic machine for ultrasonic seams, (b) Nonwoven welded seam, (c) Ultrasonic welding-pleated fabric [20, 21]. 20 World Journal of Textile Engineering and Technology, 2017, Vol. 3 Radhakrishnan and Kumari weld or bond synthetic fabrics [18]. These methods are 3.3. Seams for Cold Weather Protective Clothing adhesive free and time for drying glues or solvents can be avoided. Clean look, water proofing and less weight Seam sealing is an important step as total sealing of are the advantages when compared to a garment with clothing is required for protection from cold weather. regular seams. Waterproof tape seals the seams to prevent any moisture from leaking in through the needle holes 3.2. Seams for Biological Protective Clothing made when stitching the material together. Critically taped seams will cover the most exposed sections of Non-woven seam sealing tapes are used for the seams, while fully taped seams will seal every Medical Protective Clothing, Anti-bacterial Protective stitch on the garment [11]. Initially the suits used Clothing and other Non-woven fabric products. traditional sewing methods to simply overlap two strips Protective garments are generally useless without of rubber and sew them together. This technique had strong, tight seams. The protective suit must have the many problems as the punched holes through the two highest level of non-penetrable seam construction for overlapping strips of foam or rubber opens the suit to biohazard applications to ensure there is no water flow causing discomfort. The second problem penetration of blood-borne pathogens. Types of seams was the stretching of the material which enlarged the recommended for use in biohazard medical needle holes when the suit was used by the personnel. applications are Heat Sealed/Taped Seams, Ultrasonic These discrepancies made the protective clothing to be Seam. Hot air seam sealing machine and the ultrasonic very cold along the seams and the seam became a generator with converter are generally used for heat perforated tear edge causing wearing of the suit along sealing and ultrasonic sealing respectively. (Figure 8) the seams during use. When nylon-backed neoprene appeared, the problem of the needle weakening the The electronic conversion of the line voltage into a foam was solved, but the needle holes leaked water high voltage/high frequency signal is made by an along the seams. ultrasonic generator which is delivered to a converter. The converter has piezoelectric crystals placed 3.3.1. Seam Taping between two titanium discs that vibrate at the To deal with the early sewing problems, taping of frequency of the applied electric signal. This; vibration seams was developed. The tape is a strong nylon cloth produces a fast mechanical movement of 20,000 with a very thin but solid waterproof rubber backing. cycles per second with small amplitude of about 18 The tape is applied across the seam and bonded either microns. This can be further increased with an with a chemical solvent or with a hot rolling heat-sealer amplitude coupler. The resultant amplitude causes to melt the tape into the neoprene. With this compression and friction between the thermoplastic technology, the suit could be sewn and then taped, and molecules causing heating and melting of the material the tape would cover the sewing holes as well as which creates a bond between them. This method of providing some extra strength to prevent tearing along seaming or welding creates a superior particular and the needle holes. Figure 9(a) is an example of seam fluid barrier [19]. tape sealed protective clothing.

(a) (b) (c) Figure 9: (a) Seam tape sealed protective clothing (b) Blind Stitch seam (c) Seam glued suit [9, 22]. Seams for Protective Clothing–An Overview World Journal of Textile Engineering and Technology, 2017, Vol. 3 21

3.3.2. Seam Gluing closer to the skin. For these reasons blind stitching Another alternative to sewing was to glue the edges rapidly became the primary method of sewing wetsuits of the suit together [Figure 9c]. This created a smooth, together, with other methods used mainly for flat surface that did not necessarily need taping, but decorative or stylistic purposes [23]. foam glued to foam is prone to tearing as the bond is The seam tape is activated by hot air seam sealing not strong. Most early wetsuits were fabricated machine, and applied to sewn seams of the coated completely by hand, which could lead to sizing errors in fabrics to prevent water from leaking through the the cutting of the foam sheeting. If the cut edges did seams. The machines used for seam sealing are Hot- not align correctly or the gluing was not done well, Air Welding Machines or Ultrasonic Wave Welding water leakage along the seam is inevitable. Initially Apparatuses and the type of products using the seam suits could be found as being sewn/glued/taped only, sealing techniques are ski jackets, functional clothing, then sewn and taped, or glued and taped, or perhaps diving suits, raincoats, tents, any winter waterproof all three. clothing & products of TPU, PU and PVC coating The blind stitch method was used to sew nylon- fabrics [25]. (Figure 10) backed neoprene. A blind stitch sewing machine uses 3.4. Seams for Heat and Fire Protective Clothing a very unusual curved needle, which is designed to not go all the way through the neoprene but just shallowly The seams for heat and fire protective clothing are dip in behind the fabric backing as shown in Figure serged seam (Figure 11a), bound seam (Figure 11b), 9(b). The curved needle allows the fabric backing to be and the sealed seam (Figure 11c). A surged seam is sewn together without punching a hole completely produced when three threads are interlocked around through the neoprene, and thereby eliminating the the raw edges of two pieces for a strong, stress- water-leakage holes along the seam. Blind stitch resistant seam. A bound seam is tightly sewn with a seams also lay flat, butting up the edge of one sheet reinforced outer binding to increase seam strength and against another, allowing the material to lay flatter and barrier for potential light splash of nonhazardous liquids

(a) (b) (c) (d) Figure 10: (a) Seam sealing tape; (b) Finished Seam seal; (c) Before sealing seam; (d) after sealing seam [24].

(a) (b) (c) Figure11: (a) Serged seam, (b) Bound seam, (c) Sealed seam [23]. 22 World Journal of Textile Engineering and Technology, 2017, Vol. 3 Radhakrishnan and Kumari

(a) (b) (c) (d) (e) Figure 12: (a) Stitch type 401, (b) Stitch type 301, (c) Stitch type 504, (d) Seam 1.01, (e) Seam 2.02 [26, 27, 28]. or particle penetration through the seam. A sealed woven or nonwoven synthetic materials or blends with seam is produced when materials are lapped and up to 40% natural fibers are placed between the thermally welded with no fillers, thread or needle holes. machine’s horn and anvil or, in the case of the Seam Master, rotating wheel. High-frequency vibrations result The National Fire Protection Association (NFPA) in localized heat buildup that causes the synthetic has devised performance manufacturing standards for fibres to soften and fuse, creating a durable seal chemical and fire protective clothing. The stitch type without needles, thread, glue or other consumables. 401, 301 and 504 while seam classes superimposed The sealing of seams are very critical in such situations seam type 1.01 and lapped seam 2.02 is used for fire especially when life is exposed to serious risk [29]. protective clothing as shown in Figure 12a,b,c,d and e respectively [23]. CONCLUSION

3.5. Seams For Mechanical Protective Clothing Seams are the most essential connections in protective clothing and must be flexible and durable for Composite laminate armour or hard armour consists producing two or three dimensional products. The of multilayered fabrics combined together with a resin sewing thread should also possess qualities that must binder. Usually the hard armor, Spectra Shield, does maintain the demanding requirement of the entire not require sewing as its panels are usually just cut and product. Products in this sector are high-tech, stacked in layers that go into tight fitting pouches in the innovative and special keeping the main focus on vest. A bulletproof vest made from Kevlar can be either function. Hence seams are very special and sometimes quilt-stitched or box-stitched. Quilt-stitching forms small the life of personnel depend on these seams; if seams diamonds of cloth separated by stitching, whereas box fall apart the life of the personnel wearing the protective stitching forms a large single box in the middle of the clothing will be in danger. Hence exceptional care must vest. Quilt-stitching is more labor intensive and difficult, be taken to select the parameters to construct the and it provides a stiff panel that is hard to shift away seam and to decide the method of construction to from vulnerable areas. Box-stitching, on the other maintain the durability and safety of protective clothing. hand, is fast and easy and allows the free movement of Much research and testing is carried out to improve the the vest [25]. functions and performance of seams. Standard procedures are available to test seams as their Body armor is used for protection by law performance is of utmost importance while selecting enforcement and military personnel, Secret Service the appropriate method of construction to develop a agents, emergency responders and CIA and IRS protective suit or technical apparel. employees. Bullet-proof materials like Spectra-Shield and Kevlar–contained in the vest lose their life-saving REFERENCES effectiveness when exposed to water and hence it is absolutely critical that the seams in the outer nylon [1] Smith WC. An overview of protective clothing - markets, materials, needs., May 30-June 1, 1995. Available at shell are perfectly fuse. Ultrasonic bonding creates a http://www.intexa.com/downloads/pcc.pdf (Accessed Dec. strong molecular bond that is impervious to moisture 16, 2015). and eliminates stitch holes, glue gaps, fraying and [2] Scott RA. Textiles For Protection. Woodhead Publishing unraveling, reducing risk of damage to the interior Limited in association with The Textile Institute, Cambridge, UK, 2005. Available at www.woodheadpublishing.com. contents of the vest. Ultrasonic bonding occurs when (Accessed Dec. 30, 2015). Seams for Protective Clothing–An Overview World Journal of Textile Engineering and Technology, 2017, Vol. 3 23

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Received on 20-12-2017 Accepted on 28-12-2017 Published on 31-12-2017

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