**3. The processing parameters for joining the textiles using heat**

The joint between a minimum of two fabric layers can be made by applying the temperature and pressure at the prescribed time. Irrespective of the joining method and type of used machinery, the heat joining is controlled by four processing parameters: temperature, time, pressure, and cooling.

#### **3.1. Temperature**

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

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

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

The joint between a minimum of two fabric layers can be made by applying the temperature and pressure at the prescribed time. Irrespective of the joining method and type of used machinery, the heat joining is controlled by four processing parameters: temperature, time,

**3. The processing parameters for joining the textiles using heat**

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**

joint between the textile layers [7].

pressure, and cooling.

analyzed separately [8, 10], **Figure 1**.

220 Joining Technologies

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

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

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

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

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

#### **3.2. Pressure**

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 adhesive in the process [7, 11].
