Editorial

Citation

Stylios, G.K. (2005), "Editorial", International Journal of Clothing Science and Technology, Vol. 17 No. 2. https://doi.org/10.1108/ijcst.2005.05817baa.001

Editorial

Project philosophy

This is a generic project based on the scientific needs of the industry for being able to truly engineer technical textile products, in the same manner as other industries develop new products such as aerospace, civil, automotive, medical, etc.

In its conception, the project addressed important issues inherent to textile materials such as complexity, diversity, non-homogeneity, anisotropy and non-linearity. Nevertheless it is generally accepted that new products made out of textiles need rigour for precisely adhering to performance specifications if they are to be effective and competitive. This in a nutshell can only be achieved if three areas of expertise are developed and further integrated together; design and modelling, measurement and manufacture, as seen in Figure 1.

Figure 1

These three areas are now being researched in a collaborative manner by three partner universities; Manchester, Leeds and Heriot-Watt universities, in this national UK project which is to cost about £1 million over 3 years. As the project is approaching its second year end, some significant achievements are being reported here.

Design and modelling

In Manchester, the school of materials under Dr X Chen has devised geometrical and mechanical modelling and simulation tools for design and modelling technical textile products. In their geometric model, material properties maybe predicted from basic yarn and fabric structure variables, as shown in Figures 2 and 3.

Figure 2

Figure 3

In the mechanical model, the actual performance of a particular fabric, in this case a hollow spacing material, being crashed (Figure 4) used for protective clothing, Plate 1 can be predicted.

Figure 4

Plate 1

Measurement

The Leeds group under Professor C. Lawrence has concentrated in the measurement of Water Vapour Transport on a range of fabrics used in protective shell clothing. The effect of humidity on the diffusion constant for a wide range of fabrics has been determined. Figure 5 shows the structural morphology of some fabric samples considered.

Fabric samples “A”, “E”, “F” and “G” (Figure 5) do not possess any pores. Fabric “C” is demonstrating irregular type of pore configuration and fabric “B” is coated.

All fabrics have been divided into three groups:

• •

  twisted filaments yarn fabric;

• •

  zero twisted filaments yarn fabric (i.e. the filaments yarn having small amount of twist to hold the fibres together for the subsequent process, e.g. weaving); and

• •

  mono-filament yarn fabric.

Figure 5

An example of each group of fabric is shown in Figure 6 together with their constituent yarn.

Figure 6

The air permeability characteristics of the three fabrics Silkscreen 1, Silkscreen 2, Silkscreen 3 are shown in Figure 7

Figure 7

Plans are underway for an un-isothermal test method for water vapour transmission and the development of a temperature and humidity sensor system, which accurately measures up to 100 per cent relative humidity. The proposed testing measurement is shown in Figure 8.

Figure 8 Proposed test methodology

Finally, Leeds is developing a new air porosity-testing instrument purposely made for technical textile fabrics, shown in Plate 2.

Plate 2

Manufacturing

The Heriot-Watt team under Professor G. K. Stylios is working on manufacturing with special emphasis in the coating process. The objective is to offer an appropriate manufacturing route and the optimisation of machine variables in the coating manufacturing processing of technical textile materials.

The coating process is composed of several different process technologies, such as solution preparation, polymer polymerisation, extracting diluent from the coating network, etc., all of which need to function effectively and interact with each other.

The study is based on hydrophilic polyurethane coating in the Basecoater 200 (Plate 3) in which the coating process is being modelled using precise variables, as follows:

• •

  temperature of coating;

• •

  time to reached maximum temperature;

• •

  rolling rate;

• •

  viscosity of coating paste and coat solution system;

• •

  room environment such as temperature and humidity;

• •

  temperature of coating paste;

• •

  fabric parameter;

• •

  coating thickness;

• •

  air extraction speed;

• •

  temperature profile across the fabric;

• •

  vibrations close to blade; and

• •

  tension of fabric.

The main quality problems associated with the coating manufacturing process are:

• •

  surface roughness;

• •

  surface flatness;

• •

  thickness and homogeneity of coatings;

• •

  fault size, distribution and amount;

• •

  process reliability;

• •

  openness of structure;

• •

  thickness and resiliency;

• •

  dimensional stability; and

• •

  coat solution system.

Plate 3

Figure 9 shows SEM micrographs of the surface of uniform film on fabrics by controlling solution viscosity, film thickness (knife gap) and rolling rate (speed). The film thickness can be determined through solution viscosity, knife gap and rolling rate. After proper dilution of the coating solution, correcting the knife gap and machine speed, a uniform and flat coating surface can be produced, as shown in the right of the figure.

Figure 9

The thickness of coating on fabrics is determined by regulating the knife gap on the coater. However, under certain conditions at low speed, small gap and high viscosity, flow instability appears in which the coating becomes uneven or “ribbed”. It was found that higher concentration of polymers in the solution is required while keeping the viscosity low. Although a great amount of solvent in the solution can decrease the viscosity of the solution, an observable difference between the surface of the layer and the interior structure was found (Figure 10). Accordingly, solvent permeation due to gravity makes higher solution concentration of the coating solution to stay on the top surface zone of the fabric, rather than penetrating the fabric structure below the top. In this case holes can be found after drying (Figures 11 and 12). In order to solve the problem, different approaches have been tried to decrease the viscosity while keeping higher the concentration of the solids in the coating solution.

Figure 10

Figure 11

Figure 12

Summary

In summary, the project is progressing very well with important finding, which has led to a number of significant new developments.

UMIST has produced geometrical and mechanical modelling and simulation tools for designing technical textile products.

Leeds has produced measurement methods such as fluid flow for determining the performance specifications of technical materials.

Heriot-Watt has established fabric coating parameters for process optimisation, it has eliminated problems associated with fabric/machine interactions and has produced regular porous coating for functional materials.

For further information you may contact the individual universities, TechniTex on www.technitex.net or the editor.

George K. Stylios