Development and improvement of heat resistance of woven bag

Woven bag new national standard GB/T8946-2012 "plastic woven bag general technical requirements" has been implemented, which heat resistance test needs a mold, the following my unit - Changzhou Kejian Textile Instrument Co., Ltd. developed this woven bag heat resistance experimental mold and use to report to you.
First, the new plastic woven national standard for heat resistance test mold requirements
This standard specifies its test method in "7.4 Heat resistance" as follows:
Flatten the bag and take two pieces of the warp and weft samples respectively, with the length greater than 320mm and the width greater than 40mm. The sampling position is the spare position shown in Figure C.1 in Appendix C.
The length of the test block is 300 mm±0.5mm, the width is 20mm±0.5mm, and the mass is 1kg±5g. The lower block is longer and wider than the upper block; Smooth the pressing surface.
The braided fabric layers of the two warp samples or weft samples are relatively overlapping and placed in the middle position of the upper and lower press blocks, and placed in the oven at 80 ° C (the film bag is placed at 85 ° C) for 1h. Immediately after removal, the two overlapping samples are separated, and the surface is checked for adhesion, fusion marks, etc.
Second, the design and processing of heat resistance test mold research and development
The mold requirements for heat resistance test in "7.4 Heat Resistance Performance" of GB/T8946-2012 are:
The length of the upper pressing block is 300mm±0.5mm, the width is 20mm±0.5mm, the mass is 1kg; The lower block is longer and wider than the upper block; Smooth the pressing surface.
According to the requirements of the national standard, and the schematic diagram of the heat resistance test mold recommended by Mr. Wang Yongren, an expert in plastic knitting, we designed the following heat resistance test mold (FIG. 1).
The characteristics of this mold:
(1) The area tolerance of the upper press block is limited to 300±0.5×20±0.5mm;
(2) Ensure that the applied mass and tolerance is 1000g± 5g, which is achieved by controlling the grinding thickness of the upper press block. Each upper press block is measured by the balance until it is qualified.
(3) There is no limit to the area of the lower pressing block in the standard, and the one we give is 320×40mm, which meets the requirement of "the lower pressing block is longer and wider than the upper pressing block" in the standard.
(4) Standardize the flatness of the pressing surface; According to the requirements of "smoothing the press surface", our accuracy is...
(5) The upper and lower press blocks are made of stainless steel, which is heat-resistant steel to avoid deformation after repeated use.
(6) The upper pressing block is designed with a hanging ring, so that the hanging ring of the upper pressing block can be hooked with a hook, and the upper pressing block can be removed to avoid hot hands at 80 ° C (85 ° C for the film bag).
Third, the new and old plastic woven bag standard in the heat resistance test comparison
Simply put, the old standard is to apply 1000g load on the specified 300×20mm braid without limiting the area of the upper pressing block, as shown in Figure 2; The new standard is to apply 1000g load to the woven cloth with a 300×20mm upper pressing block, without limiting the area of the woven cloth, as shown in Figure 3.
The old standard GB/T 8946-1998 "Plastic woven bag" and GB/T 8947-1998 "Composite plastic woven bag" stipulate in the "heat resistance" of Chapter 5:
Two pieces of warp and weft samples are taken from the bag, with a length of 300mm and a width of 20mm.
The surfaces were overlapped, a load of 9.8N was applied to them, and the samples were placed in an oven at 80℃ for 1h. The two overlapping samples were separated immediately after removal, and abnormal conditions such as adhesion and melt marks were checked on the surface.
Compared with the old standard, the revised description is as follows:
1. The basic difference between the standard heat resistance test method and the original standard is to change the size of the sample woven fabric 300×20mm to the size of the upper press block 300×20mm.
2, this standard stipulates that the upper press block length is 300 mm±0.5mm, width is 20mm±0.5mm, mass is 1kg±5g; The lower block is longer and wider than the upper block; Smooth the press surface." The first is to limit the area of the block; The second is to standardize the flatness of the pressing surface; The third is that mass is applied, not force. Therefore, the pressure of the block is fixed and does not change. Then the length and width of the warp and weft samples to be pressed should be greater than the length and width of the upper pressing block. Therefore, it is specified that the length of the warp and weft samples is greater than 320mm and the width is greater than 40mm, considering that the warm woven fabric sample may be adhered to and thickened around, and the cold cut woven fabric sample is also slightly thickened around due to cutting knife. Moreover, the sample is slightly larger than the upper pressing block, so that the upper pressing block can easily align the sample, and the experiment can be carried out with a slight deviation.
3, the original standard stipulates that "warp and weft samples are two pieces each, length 300mm, width 20mm." "A load of 9.8N is applied on it", without specifying the area of the block and the degree of surface flatness. Of course, the length and width of the block should be greater than the length and width of the sample, but there is no provision in the standard, which is not perfect. If the block is small or cone shaped, its pressure will change and become uncertain. If the woven cloth is hot, the surrounding area may be adhered and thickened, and the pressure is relatively tight, while the middle area is not tight. When two overlapping samples are separated, there may be abnormal conditions such as adhesion and dissolution marks around the area, but not in the middle area.
4. The new standard clearly stipulates that "the woven fabric layer is relatively overlapping and placed in the middle position of the upper and lower pressing blocks".
5, the accuracy of the new standard with the pressure block to ensure the accuracy of the test effect.