HANDBOOK OF TECHNICAL TEXTILES

This book confirms once again that enthusiasm and love for the profession are more important than financial gain. Department of Built Environment, Faculty of Technology, Bolton Institute, Deane Road, Bolton BL3 5AB, UK.

Preface

The editors would like to express their sincere thanks to all the authors for their important contribution, patience and cooperation. Special thanks are also given to Patricia Morrison of Woodhead Publishing Ltd, Cambridge for her continued interest and effort in keeping this project going for so long and her continued faith in the editors.

List of contributors

Chen

Holme

Technical textiles market – an overview

Introduction

Beyond that, much of the technology and expertise associated with the industry rests on an understanding of the needs and dynamics of many very different end-use and market sectors. This chapter takes a closer look at some of the factors – technical, commercial and global – that drive the industry forward.

Deﬁnition and scope of technical textiles

Technical or industrial textiles: what’s in a name?
Operating at the boundaries of textiles
Inconsistent statistical reporting

If the adjective "technical" is difficult to define with any precision, then so is the purpose of the term textile. Polymer membranes, composites and extruded webs and meshes are other products that challenge traditional notions of the scope of technical textile materials, processes and products.

Milestones in the development of technical textiles

Developments in ﬁbre materials – natural ﬁbres
Viscose rayon
Polyamide and polyester
Polyoleﬁns
High performance ﬁbres
Glass and ceramics

As mentioned above, the development of the polypropylene industry was initially focused on the European and North American market. The introduction of other high performance fibers increased rapidly, especially in the late 1980s, and in the wake of the aramids.

Textile processes

On the other hand, the total value of yarns and fibers and all technical textile products will grow slightly slower than their volume due to the changing mix of materials and technologies, which will especially reflect the growth of nonwovens.

Applications

Transport textiles
Industrial products and components
Medical and hygiene textiles
Home textiles
Clothing components
Agriculture, horticulture and ﬁshing
Construction – building and rooﬁng
Packaging and containment
Sport and leisure
Geotextiles in civil engineering
Protective and safety clothing and textiles
Ecological protection textiles

The automotive industry (which accounts for a high proportion of all transport textiles) is certainly one of the most mature in market terms. Temporary structures such as tents, canopies and canopies are some of the most obvious and visible applications of textiles.

Globalisation of technical textiles

Such globalization has already progressed further in the automotive and transportation industry, the largest of the 12 market segments defined above. Manufacturers in the newly industrialized world are rapidly adopting the latest materials and processing technologies.

Future of the technical textiles industry

A changing strategic environment

The economic importance of technical textiles worldwide therefore undoubtedly far exceeds the $60 billion estimated in Tables 1.2-1.4 for staple fibers, yarns and textiles alone. Technical textiles will become better value for money than ever before, which should pave the way for further applications as existing end uses mature.

If the 1980s was a period when the technical textile industry enjoyed a rapid and increasing awareness of its existence by the outside world (as well as within the mainstream textile industry), then the 1990s was an era of more mature commercial development and consolidation as fiber producers and textile manufacturers have concentrated on revamping and refocusing their businesses in the wake of the global recession. Individual companies will be defined less by the technologies and materials they use than by the markets and applications they serve.

Technical ﬁbres

Introduction
Conventional ﬁbres

Natural ﬁbres
Regenerated ﬁbres
Synthetic ﬁbres

High strength and high modulus organic ﬁbres
High chemical- and combustion-resistant organic ﬁbres
High performance inorganic ﬁbres
Ultra-ﬁne and novelty ﬁbres
Civil and agricultural engineering
Automotive and aeronautics
Medical and hygiene applications
Protection and defence
Miscellaneous
Conclusions

Further development and refinement of the manufacturing technique has created a whole range of fibers with improved properties. It is made into fibers by extruding sodium alginate in a calcium chloride bath where calcium alginate filaments precipitate. The filaments are then drawn, washed and dried.

Figure 2.1 presents typical stress/strain behaviour for most conventional ﬁbres.

Technical yarns

Introduction

Staple ﬁbre yarns

Ring spinning
Rotor spinning
Friction spinning
Wrap spinning
Air-jet spinning
Twistless spinning
Ply yarn

As the bobbin rotates, the thread tension pulls the traveler around the ring. 3.4) where is the thread twist (m-1 turns), is the thread arm rotation speed (rpm) and Vdis is the thread delivery speed (m min-1).

Filament yarns

Deﬁnitions
Manufacture of ﬁlament yarns
Filament technical yarns

Because of its properties and low cost, glass fiber is widely used in the manufacture of reinforcement for composites. It is commonly used in glass-reinforced plastics in the form of woven fabrics.

Bibliography

PBO fiber has exceptional thermal properties and almost twice the strength of conventional para-aramid fibers. Its low LOI gives PBO more than twice the fire-retardant properties of meta-aramid fibers.

Technical fabric structures – 1. Woven fabrics

Introduction

Weave structures

Plain weave
Rib fabrics and matt weave fabrics
Twill fabrics
Satins and sateens
Lenos
Triaxial weaves

By using appropriate covering factors and yarn selection, most of the abrasion on such a fabric can be concentrated on the base yarn and the weft will be protected. A 2/1 twill is a warp twill, that is a fabric where most of the warp yarn is on the surface, while a 1/2 twill has a weft.

Figure 4.9(a) and (b) shows 5-end weft sateens with two and three steps, respec- respec-tively

Selvedge

Hairpin selvedge – shuttle weaving machine
Leno and helical selvedges
Tucked-in selvedges
Sealed selvedges

To ensure a flat edge, a different weave can be used in the self edge of the body of the cloth. The thread extends to the fall of the cloth and is automatically withdrawn during weaving.

Fabric speciﬁcations and fabric geometry

Fabric width
Fabric area density
Crimp
Cover factors
Thickness

It depends on the warp and weft coverage factors, described in Section 4.4.4, the properties of the yarns and the weaving and finishing tension. The shrinkage is measured by the ratio between the length of the fabric sample and the corresponding length of the yarn when straightened after being removed from the cloth, as shown in Fig.

Weaving – machines (looms) and operations

Warp preparation
Shedding
Weft insertion and beat-up (single phase machines)
Other motions and accessories for single phase weaving machines
Machine width

Each point across the full width of the weaving machine can be individually controlled and the weft repeat can be of any desired length. After each pick is inserted, it must be beaten up, which is moved to the fall of the cloth.

Figure 4.22 shows schematically the production of cloth on a shuttle loom. The shuttle carrying the pirn, on which the weft is wound, is reciprocated through the warp by a picking motion (not shown) on each side of the machine

The future

Technical fabric structures – 2. Knitted fabrics

Terms and deﬁnitions

Overlaps the lateral movement of the guide rods on the beard or hook side of the needle. Underlap Is the lateral movement of the guide rods on the side of the needle far from the hook or beard.

Weft knitting machines

Loop formation with latch needles
Single-jersey latch needle machines
Double-jersey machines

The operating speed of these machines is up to twice the speed of equivalent latch needle machines. The sink facilitates setting up the machine after a partial or full press (after the shutters have been opened manually).

Figure 5.8(a) illustrates the needle at tuck height, that is high enough to receive a new yarn, but not high enough to clear the old loop below the latch

Weft-knitted structures

They range from simple machines over mechanical jacquard machines to fully electronic and computerized flat machines, even equipped with presser feet. Two- and three-dimensional structures as well as complete garments without seams or joints can be produced on the latest electronic flat knitting machines and the associated design systems.

Process control in weft knitting

Main factors affecting the dimensional properties of knitted fabrics or garments
Laboratory stages of relaxation
Fabric geometry of plain single-jersey structures
Practical implications of fabric geometry studies
Quality control in weft knitting

Static soaking in water and dry flat - Wet relaxed state: dense structures do not always reach a "true" relaxed state. 5.5) where is the total number of needles, is the stitch length (mm) and is the text of Tis yarn, or.

Table 5.2 k-Constant values for wool plain single jersey a k c k w k s k c /k w

End-use applications of weft-knitted fabrics

Flat bar machines
Circular machines
Straight-bar machines (fully fashioned machines)

The dimensions of a knit fabric are determined by the number of stitches and their size, which in turn is determined by the length of the stitch. Machine width: from 2–16 machines per section - each section up to 36 inches wide (up to 40 machines per section were produced).

Warp-knitting machines

Introduction
Tricot and raschel machines
Knitting action of compound needle warp-knitting machine
Knitting action of standard raschel machine

5.20(c) shows the guide for overlapping and swinging back at the front of the car. 5.21(c) the guide bars swing to the rear of the machine and then close for the overlap and in Fig.

Figure 5.21(f) shows the needle bar continuing to descend, its head passing below the surface of the trick-plate, drawing the new loops through the old loops, which are cast-off, and as the web holders advance over the trick-plate, the underlap shog of the

Warp-knitted structures

Stitch notation
Single-guide bar structures
Two-guide bar full-set structures
Grey speciﬁcation of a warp-knitted fabric
Fabric quality
Tightness factor
Area density
End-use applications of warp-knitted fabrics Speciﬁcation for tricot machines is

The structure of the simplest fabric made with two swords is shown in fig. The long rear sword underlaps are locked to the body of the fabric by the warp stitches of the front sword.

Figure 5.31 shows the laid-in thread being trapped in the fabric by the front guide bar threads knitting an open tricot stitch (0-1, 2-1).

Technical fabric structures – 3. Nonwoven fabrics

Introduction

Instead, it is necessary to explain the methods of ﬁber processing and the methods of bonding separately. In fiber processing, it is common to first make a thin layer of fiber called a web and then to lay several webs on top of each other to form a sheet which goes directly to bonding.

Methods of batt production using carding machines

Parallel laying
Cross laying

The weakness of the fabric in the transverse direction has a great effect on possible uses of the fabric. Cross-laid fabrics are consequently very strong in the transverse direction and weak in the machine direction.

Air laying

Another problem is trying to match the cross-layer input speed with the card's web speed. It is often thought that because the fibers are deposited without airflow control, they will be random in the plane of the piston.

Figure 6.6 shows the formation zone in more detail. This shows that the ﬁbres fall onto an inclined plane, and that the angle between this plane and the plane of the fabric depends on the width of the formation zone, w, and the thickness of the

Wet laying

This belief is so widespread that airlaid fabrics are often referred to as "randomly laid" fabrics. In fact, air-laid fabrics can have stiffness ratios as high as 2.5:1, which is no accident.

Dry laying wood pulp

It is possible when making thick fabrics to reduce the width,w, so that the yarns lie at a considerable angle to the plane of the batt. It is claimed that for this reason air-laid fabrics show better compression recovery compared to cross-laid fabrics.

Spun laying

Although the dry paper process cannot currently be considered a non-woven process, it is very likely that the process will be modified to accept textile fibers and will become very important in non-woven materials in the future. By controlling the speed and amplitude of this oscillation, the degree of cross-directionality can be controlled.

Flash spinning

Because the fine fibers leave very small pores in the fabric, it is not only waterproof, but also resistant to many other liquids with a surface tension lower than water. Tyvek is mainly used for protective clothing in the chemical, nuclear and oil industries, probably as protection for the armed forces and certainly in many industries that do not need such good protection but where it is conveniently found.

Melt blown

The fact that the original fibers were very fine means that the material is very smooth and can be used for handwriting or printing. For many end uses, no form of bonding is used and the material is not nonwoven, but simply a batt of loose fibers.

Chemical bonding

Saturation bonding
Foam bonding
Print bonding
Spray bonding

Therefore, the fabric modulus is of the order of the fiber modulus, i.e. extremely high. The foam is then fed to the horizontal cut of the impregnation roller, as shown in fig.

Thermal bonding

Thermal bonding without pressure
Thermal bonding with some pressure
Thermal bonding with high pressure
Thermal bonding with point contact

This method is basically the same as the previous one, except that when the batt leaves the thermobind furnace, it is calendered by two heavy rollers to bring it to the desired thickness. The binding is limited to those points where the rollers touch, leaving about 95% of the bat unbound.

Solvent bonding

Needlefelting

Third, if it is necessary to get a higher production from a needle loom, it is better to increase the number of needles in the board or increase the speed of the embroidery board. Less commonly, the geotextile is needed for drainage, which means water movement in the plane of the fabric.

Stitch bonding

Batt bonded by threads
Stitch bonding without threads
Stitch bonding to produce a pile fabric
Batt looped through a supporting structure
Laid yarns sewn together with binding threads

This structure was used for making single-sided pile towels and also for making loop-pile rugs in Eastern Europe. The structure was not popular in the West due to competition with double-sided terry towels and tufted rugs. Again, sets of yarns are laid crosswise, but in this case not in the transverse direction, but at, for example, 45° or 60° to the transverse direction.

Hydroentanglement

Two sets of yarn in e.g. +45° and -45° in the transverse direction plus another layer of yarn in the machine direction can be sewn together in the usual way. Again, high modulus yarns are used, with the advantage that the directional properties of the fabric can be designed to satisfy the stresses in the component being manufactured.

Finishing of technical textiles

Introduction

Finishing processes

Chemical processes: these can be described as those processes that involve the application of chemicals to the fabric. After the filling or chemical finish application stage, the fabric is usually dried to remove water from the fabric and then some form of coating fixation is performed.

Mechanical ﬁnishes

Calendering
Raising
Shearing
Compressive shrinkage

Schreiner or silk finish: this is a silk-like finish on one side of the fabric. In the pile action, the points of the wire are directed away from the direction of movement of the fabric.

Heat setting

Heat-setting mechanisms
Fibre structure
Polymer orientation
Transition temperatures
Heat shrinkage
Heat setting
Essentials of heat setting

In nylon and polyester, these crystalline regions take up about 50% of the total space in the fiber. Melting Point: At this point, the forces holding the molecules in the crystalline regions of the fiber are overcome by the thermal energy and the polymer melts.

Chemical processes

Durable ﬂame-retardant treatments 13,14
Synthetic ﬁbres with inherent ﬂame-retardant properties
Water-repellent ﬁnishes
Antistatic ﬁnishes
Antimicrobial and antifungal ﬁnishes

Some of the later treatments involve the use of other fatty acid derivatives and some of these are shown in Fig. The normal addition depends on the efficiency of the specific product, but addition weights of 1-4% are commonly quoted.

Table 7.1 Typical backcoating formulation

Coating of technical textiles

Introduction

Chemistry of coated textiles

Polyvinyl chloride (PVC)
Polyvinylidene chloride (PVDC)
Polytetraﬂuoroethylene (PTFE)
Rubber
Styrene–Butadiene Rubber (SBR)
Nitrile rubber
Butyl rubber
Polychloroprene (neoprene)
Chlorosulphonated polyethylene (Hypalon)
Silicone rubbers
Polyurethanes

As in the case of PVC, it is produced by emulsion polymerization of vinylidene chloride, as illustrated in fig. These principles are used in the production of tires and harnesses, where the excellent wear resistance of natural rubber makes it the material of choice.

Coating techniques 12

Lick roll
Knife coating

The two materials will react at room temperature, although this is often accelerated by raising the temperature. These blocked isocyanates will not react at room temperature, but will react at elevated temperatures in the presence of organotin catalysts.