**2. The principles of joining the textiles using heat**

The principle of joining the textiles is based on heat applied on textile components at defined pressure and time. For all of the technological processes to join textiles components by heat, irrespective of used equipment, and application area, are common [1, 7]:


Different applications require different types of equipment; therefore, a variety of equipment can be used, such as [1, 7]:

**•** flat‐bed press,

**1. Introduction**

218 Joining Technologies

on produced textile products [1–4].

Textile materials can be joined by sewing, fusing, and welding. Sewing is the oldest and also today most popular technology for joining the textile materials, when minimum two textile components are join together to reach the new two‐ or three‐dimensional shape of a textile product. Irrespective, if sewing is made by hand or sewing machine, the sewing thread and needle is needed to design, stitches, and seams. As the first application of permanently seamless connection of textile components can be considered the fusing of the fusible interfacing on backside of fabric to achieve more stiff part of a garment. Later, the welding technologies have become a significant competition to the sewing technologies. The first attempt of joining the textile materials in terms of seams without the sewing threads was done by hot air/wedge welding. That technology presents a milestone in manufacturing of seamless textile products because there were no yarn breakages during the sewing, no missed stitches, and seam puckering

The wider use of welding technologies for textile applications can be traced from new millennium. First welding machines for commercial production of garments and technical textiles appeared in that time [5]. Since then welding has become widely used techniques for textile products, where we require special features and high functional utility, which include water permeability, resistance to pressure, wear and tear of seams, air permeability, and aesthetic appearance. In this group of textile, products are inflatable boats, protective and sports clothing, tents, truck awnings, bag filters, inflatable toys, etc. Hot air and wedge, ultrasonic, laser, and radio frequency technology can create the welded area [6, 7]. In compar‐ ison, the fusing technologies were first introduced on large scale in the 1950s and it became an integral part of clothing technology [4]. The highest development level of fusing the interning on textile materials has been detected at the end of the previous century, when a number of

This chapter gives an overview of the basic principles of hot air/wedge and fusing technology as the most used seamless technologies. The theoretical background and fundamental working principles of both technologies is presented. The thermoplastic adhesives and textile substrates for fusible interlinings and welding tapes is discussed in a separate subchapter. Furthermore, the fusing/welding methods and their parameters in connection with the evaluation of end quality of fused/welded panels are presented with latest scientific findings. The advantages and disadvantages of the presented techniques using the real examples is discussed together with the certain application areas in terms of influences of fusing parameters on fused panel

The principle of joining the textiles is based on heat applied on textile components at defined pressure and time. For all of the technological processes to join textiles components by heat,

new types of fusible interlining and fusing machines were developed.

properties, properties of hot air welded seams, and e‐textile transmission lines.

irrespective of used equipment, and application area, are common [1, 7]:

**2. The principles of joining the textiles using heat**


According to the above‐mentioned backgrounds, the techniques for assembling the textiles using heat can be grouped into the following technologies: fusing, hot air/wedge welding, and ironing.

**Figure 1.** Schematic presentation of a fused panel.

#### **2.1. Fusing technologies**

Fusing technologies were firstly introduced bonding technologies for joining the textile materials using heat. The fused panel arises during the fusing process as a joined composite between the fabrics and fusible interlining. During the fusing process, the fabric and fusible interlining are in contact with the heating elements. The applied pressure at the end of the fusing process provides the penetration of the thermoplastic adhesive into the fabric. The right balance among fusing temperature, time, and pressure is very important for the end quality of a fused joint between the fabric and fusible interring. Moreover, it also depends on the construction and raw material of the shell fabric as well as on the type and manner of coating the thermoplastic adhesive. The properties of a fused panel have specific values with respect to the shell fabrics and fusible interlinings [8, 9]. Therefore, it is not possible to add together mechanical properties of shell fabrics and fusible interlining; every fused panel must be analyzed separately [8, 10], **Figure 1**.

**3.1. Temperature**

The temperature presents a heat required to melt the adhesive coated on the fabric surface or synthetic fibers of used fabric. During the fusing process, the temperature of a heating plate and intermediate temperature between the fabrics to be joined together are both important. The intermediate temperature is the actual temperature, at which the adhesive begins to melt and penetrates into the structure of heat‐joined fabrics. The temperature of the heating plates is for 20–30°C higher than the intermediate temperature due to heat losses, which occur at the

Applying Heat for Joining Textile Materials http://dx.doi.org/10.5772/64309/ 221

The temperature depends on the time of heating, the thickness of the fabrics, thermal conduc‐ tivity, and the types of thermoplastics and used method for joining the textiles using heat.

The thermal sensitive paper strips or electromechanical calorimeters can be used for measuring the actual applied temperature in the joining process or for indicating the temperature during

On the other side, the temperature of the air during hot air welding should be set according to used materials in order to melt properly the material at the joint area. The temperature has an important effect on the viscosity of the melt materials, therefore it should be carefully controlled. The temperature is controlled using a sensor in the wedge or in the air stream. The temperature set needs to be significantly higher (100–250°C) than the material melting point. Hot air systems typically allow operation at up to 600–750°C, hot wedge at up to 500°C. It is recommended to carry out tests at a range of temperatures in order to achieve the required joint performance. The ambient temperature of the working place or effects of the sun also

During heat joining of textiles the following types of the pressure can be applied: planar, linear, and combination of both. The pressure accelerates the transition of the thermoplastic adhesive into the textile structure in the joining procedure and provides the uniformity of joint parts. The pressure is dependent on the type of the used fabrics and type of the adhesive. The pressure must be constant during the process of fixing, as it enables uniform transition of thermoplastic

transition temperature of the heating plates of the material [8].

the calibration of machine settings, **Figure 3** [13].

**Figure 3.** Thermal sensitive paper strip for temperature control [13].

have the effect on the optimal welding parameters [7].

**3.2. Pressure**

adhesive in the process [7, 11].

#### **2.2. Hot air/wedge welding technologies**

The heat technology based on hot air and wedge for joining the textiles is called welding. It is mainly applicable to fully or partially fabrics with thermoplastic components. They can be fibers or the fabric, a thermoplastic coating or a film. Hot air welding is used to thermally bond foils and textiles, where the delivery of the heat is not in the contact with the textile material. On the other side, in hot wedge welding, a small metal wedge is in the contact with fabric during the welding process [7, 11]. Hot air welding is applied to the hot melt adhesive, which is activated at precisely controlled temperature. Under applied pressure after the cooling phase, a strong bond is formed between the tape and the seam. **Figure 2** presents the charac‐ teristic schematic presentation of hot air/wedge welded seams. Mainly those seams have water‐ and wind‐proof properties and if they are welded on the face side of the fabric, they can contribute to the design effect of a manufactured textile product.

**Figure 2.** Schematic presentation of a hot air/wedge welded seams [12].

#### **2.3. Ironing as welding technology**

By ironing the temperature is controlled by a thermostat while pressure and time is mainly depending on operator. Wide range of ironing equipment can be used for joining the textiles by ironing. The maximum joining area should have the size of the flat of iron to get uniform joint between the textile layers [7].
