Base fabric:
Usually made of polyester, there are also a small number of cotton and polyester-cotton fabrics, nylon, acrylic and glass fiber products. Although polytetrafluoroethylene (PTFE) fiber, aramid fiber, carbon fiber, etc. have excellent performance, they are too expensive for large-scale application, so they are generally rarely used except for special purposes.
Polyester is widely used for weaving base fabrics due to its high strength, durability, good tensile properties and affordable price. Nylon is also widely used. It is sometimes stronger than polyester, but it is more expensive and has greater elongation. Polyester fabric is used as the base fabric, and PVC coating or PVC film bonding is a bulk product of industrial textiles in the United States and Western Europe. Its uses include awnings, tents, building fabrics, advertising light box signs, commodity and transportation covers, container materials, marine fabrics, agricultural covers, inflatable fabrics, machine and car covers, luggage fabrics, raincoats, padded safety clothing, etc., and there are many manufacturers. Glass fiber fabrics no longer stretch after pre-tensioning, and are suitable for permanent buildings after polytetrafluoroethylene coating.
Glass fiber can reflect a higher proportion of the sun's heat, keep the structure cool inside, and will not burn and smoke. Polytetrafluoroethylene (PTFE) fiber woven fabrics have the advantages of resisting environmental damage and being resistant to bending and folding, but these structural materials are relatively expensive.
In the application of awnings, solution-dyed acrylic (generally modified acrylic with flame retardant properties) accounts for the largest proportion (even more than polyester). The reason for using acrylic is that it has good light resistance, bright color, and good shape retention, especially 100% solution dyeing can better play its advantages. Some of the awnings also have the function of light boxes.
Abroad, most industrial fabrics use filaments and rarely use short-staple yarns. This is because the filaments themselves have good strength and elongation properties. If short-staple yarns are used, the twist should be selected appropriately so that it can withstand higher tensile loads and prevent premature yarn breakage caused by slippage between fibers. When the twist is small, the filaments will become flat during weaving, increasing the coverage rate, which is suitable for hydrophobic materials.
When polyester fabrics require high strength, polyester industrial yarns should be used, and some should use high-strength and low-shrinkage polyester industrial yarns. The products made have high strength, good tear resistance, stable dimensions, and are not easy to peel off, and are widely used.
There are two types of base fabric weaving processes: weaving and knitting. The knitted base fabric is mainly biaxial warp knitted fabric (as shown in the figure). Biaxial warp knitted fabrics have high strength utilization, low shrinkage, good bonding with coatings, high tear strength, and much higher production speed than weaving, so their applications are gradually increasing.
When the strength requirement is not very high, in order to improve the peel strength, the base fabric can be a mesh fabric (also known as a sparse fabric). The use of biaxial warp knitting is conducive to making the position of the intersection of the mesh structure relatively fixed.
At present, woven fabrics are still the most commonly used abroad. When using the weaving process, attention should be paid to the warping and weaving process, and the uniformity of tension should be emphasized to make the coating surface smooth. When the fabric density is high, it is necessary to apply sizing and twisting; when the fabric shrinkage rate is low, heat setting can be omitted. However, if high-shrinkage filaments are used, the fabric must be heat-set before coating to avoid excessive shrinkage during coating. When using a sparse fabric base fabric to produce laminated fabrics, it is generally not necessary to scour, because at this time it mainly depends on the bonding between the upper and lower layers rather than the bonding between the layers and the fabric. If the sizing material and the coating material are compatible, sometimes scouring can be omitted before coating.
The typical weight of coated base fabric is 112~198g/m* (3.3~5.9oz/yd'). The design of tight structure does not cause the yarns to slip when torn like loose fabrics. The tensile strength of coated fabric is higher, but the tear strength is not necessarily high. For example, the tear strength of coated fabric can be doubled by using anti-rip fabric structure, i.e. changing plain weave, and replacing single yarn with double yarn at a certain distance, but the coating will be thinner at the crossing of double yarn and more sensitive to wear. The typical weight of laminated loose fabric is 41~112g/m² (1.2~3.3oz/yd').