The shrinkage rate of flame retardant fabric refers to the percentage of shrinkage of the flame retardant fabric after washing or soaking. Shrinkage is a phenomenon that the length or width of flame retardant fabrics change after washing, dehydration and drying in a certain state. Shrinkage degree involves different kinds of fibers, fabric structure, fabric processing by different external forces and so on.
Flame retardant fabrics with the smallest shrinkage rate are blended flame retardant fabrics. Flame retardant fabrics have shrinkage discoloration problems, the key is finishing process. Therefore, the general flame retardant fabric is treated by pre shrinking. It is noteworthy that the flame retardant fabric treated by pre-shrinkage is not equal to non-shrinkage, but refers to shrinkage within 3% - 4%.
Therefore, in the selection of flame retardant fabrics, in addition to the selection of flame retardant fabric quality, color, flame retardant performance, the shrinkage rate of flame retardant fabrics should also be understood.
When the flame retardant fabrics are spinning, or when the yarns are weaving and dyeing, the yarns in the flame retardant fabrics are stretched or deformed by external forces. At the same time, the yarn structure of the flame retardant fabrics produces internal stress, which should be applied to different degrees in the state of static dry relaxation, static wet relaxation, Dynamic Wet relaxation and full relaxation. The release of the force will restore the yarn of the flame retardant fabric to its original state. The flame retardant fabrics of different materials have different shrinkage. The reasons affecting the shrinkage of flame retardant fabrics are the following
1. raw materials
Flame retardant fabrics have different raw materials and shrinkage. Generally speaking, the fiber with high hygroscopicity expands, enlarges diameter, shortens length and enlarges shrinkage rate after immersion.
The density of flame retardant fabric is different and shrinkage rate is different. If the warp and weft density is similar, the longitude and latitude shrinkage ratio is also close. If the warp density of flame retardant fabrics is high, the warp shrinkage will be large, otherwise, the weft density is higher than the warp density of flame retardant fabrics, and the weft shrinkage will be large.
3. yarn thickness
Flame retardant fabrics are different in thickness and shrinkage. The shrinkage of the flame retardant fabric with coarse yarn is large, and the shrinkage of the flame retardant fabric with fine yarn is small.
4. production technology
The shrinkage rate of flame retardant fabric is different. Generally speaking, in the process of weaving, dyeing and finishing flame retardant fabrics, the fiber should be stretched many times, the processing time is long, and the shrinkage rate of fabric with large tension is large, otherwise it is small.