Some knowledge points of plastic woven bags
Plastic woven bags are made from polypropylene (PP) as the main raw material, through extrusion, drawing, weaving, knitting, and bag making. Polypropylene is a semi transparent and semi crystalline thermoplastic with the characteristics of high strength, good insulation, low water absorption, high hot forming temperature, low density, and high crystallinity. It is the main raw material for woven bags. Modified fillers usually include glass fiber, mineral fillers, thermoplastic rubber, etc.
Plastic woven bags are widely used. At present, plastic woven bags are mainly used for agricultural product packaging, cement bag packaging, food packaging, geotechnical engineering, tourism transportation, flood control materials, etc.
Woven bags mainly include plastic woven bags (non covered woven bags), composite plastic woven bags, and various woven fabrics. The production process of plastic woven bags involves printing, cutting, and sewing woven fabric into woven bags. Depending on the equipment used, it can be cut before printing, or printed before cutting. Automatic tailoring can continuously complete printing, cutting, sewing and other processes, and can also be made into valve pockets, bottom pockets, etc. For plain woven fabrics, bags can be made by bonding the middle seam.
The production process of plastic woven bags is to composite or coat woven fabric, coating materials with paper or film. The obtained cylinder cloth or fabric sheets can be cut, printed, sewn and made into ordinary bottom seam bags, or punched, folded, cut, printed and sewn into cement bags, and the obtained fabric sheets can be sewn, bonded, printed, cut and pasted into bottom patch bags. It can also be welded and wound to manufacture waterproof oilcloth and geotextile.
The technical indicators of the production process of plastic woven bags are mainly divided into four categories:
1. Physical and chemical modification index. Mainly including blending modification, blending ratio, functional additive addition ratio, and blending ratio of waste recycled materials;
2. Physical properties Rheological index. Mainly including draft ratio, expansion ratio, draft ratio, and retraction ratio;
3. Mechanical performance indicators. It mainly includes tension, relative tension, elongation at break, linear speed and Linear density deviation;
4. Tolerance size indicators. There are mainly thickness and width of flat lines.
The lining process of plastic woven bags: Polyethylene material is heated by an extruder, melted, plasticized, and stably extruded; Squeeze into a cylindrical thin film through the machine head; Injecting compressed gas to expand and form tubular bubbles; Use a cooling air ring to cool and shape, and fold it with a herringbone shaped splint; By using traction rollers, transmission rollers, and winding rollers, cutting and heat sealing processes are carried out to complete the production of inner lining bags, and then bagging is carried out.
The production of plastic woven bags using pure polypropylene cannot meet the requirements, and a certain proportion of high-pressure polyethylene, calcium carbonate, and color masterbatch need to be added. Adding a small amount of high-pressure polyethylene can reduce the viscosity and melting rate of the material flow during extrusion, increase flowability, improve the toughness and softness of the woven bag, maintain a certain elongation at break, and improve the low-temperature impact resistance of polypropylene.