Plastic woven bags are flexible packaging containers made of synthetic resin as the main raw material through extrusion, stretching, weaving and other processes. They are one of the most widely used packaging forms in the field of modern industrial packaging. This type of packaging bags has become an indispensable packaging solution for the food, chemical, building materials and other industries due to its excellent physical properties, good environmental adaptability and high cost performance. As an important part of the modern packaging industry, its performance and quality depend to a large extent on the selected plastic resin material. Here I will introduce plastic woven bags from the characteristics of different plastic resins, processing technology, application scenarios and other aspects.
Application of polypropylene resin in woven bags
Basic characteristics of polypropylene resin
Polypropylene is the most widely used plastic resin in woven bag production, accounting for more than 80%.
Physical properties. The density is only 0.90-0.91g/cm³, which is the lightest of the commonly used plastics. Its tensile strength can reach 30-40MPa, the bending modulus is about 1500MPa. In addition, it has excellent rigidity.
Thermal properties. The melting point is between 160-170℃. The heat deformation temperature is between 100-120℃ (under 0.45MPa). And the Vicat softening point is about 150℃.
Chemical stability. It has good tolerance to most acids, alkalis, salt solutions and organic solvents, and is particularly suitable for chemical product packaging.
Processing performance. The melt flow rate is moderate, usually in the range of 2-4g/10min (230℃, 2.16kg), which is very suitable for wire drawing process.
PP grades and characteristics for woven bags
Homopolymer PP T30S
PP T30S is the most typical homopolymer for woven bags, with the following excellent properties:
High isotacticity (>95%), high crystallinity, and good mechanical strength.
Narrow molecular weight distribution and excellent processing stability.
Low ash content (<0.03%), reducing spinneret blockage.
Low volatile matter (<0.2%), less smoke during production.
Homopolymer PP T03
PP T03 is another commonly used grade. Compared with T30S:
The melt index is slightly higher (3.0-4.0g/10min), and the processing fluidity is better.
The tensile strength is slightly lower, but the elongation at break is higher.
It is more suitable for producing thin woven fabrics and high-speed drawing.
Impact copolymer PP
Impact copolymer PP is used in woven bags with certain special requirements:
Improving low-temperature toughness by introducing ethylene monomer, usually 5-15%.
The impact resistance is improved by 2-3 times, which is especially suitable for use in cold areas.
However, the tensile strength and rigidity are reduced, and the cost is also higher.
Application areas of PP woven bags
Grain packaging: rice, wheat, corn, etc., Usually using standard packaging of 50kg/bag.
Performance requirements:
Moisture resistance. PE film lining, water vapor transmission rate ≤5g/m².
UV resistance. UV stabilizer needs to be added for outdoor storage.
Load-bearing capacity. Standard 50kg/bag, warp tension ≥350N/5cm.
Fertilizer and pesticide: packaging of chemical products such as urea and compound fertilizer.
Performance requirements:
Chemical corrosion resistance, acid and alkali resistance, prevent fertilizer leakage.
Anti-aging, add anti-UV agent, service life ≥12 months.
Feed packaging: packaging of poultry feed and fish feed.
Performance requirements:
Mold and moisture resistance, inner PE film or aluminum foil layer.
Breathability, some feeds require microporous structure to prevent deterioration.
Building material packaging: cement, sand and gravel, etc., require high strength and moisture resistance.
Performance requirements:
High gram weight, ≥90g/m², prevent bag breakage.
Moisture resistance, lamination or coating treatment, humidity ≤5%.
Drop resistance, 1.5m drop test without breaking.
Chemical raw material packaging, ton bag packaging, load-bearing 0.5-2 tons.
Performance requirements:
Corrosion resistance, some chemicals require HDPE lining.
Anti-static, carbon black filling or anti-static coating.
Food grade packaging:
Food grade PP resin and additives that meet FDA requirements must be used, no fluorescent agent, no heavy metals.
Consumer goods and retail packaging: shopping bags, gift bags, home storage bags.
Performance requirements:
Aesthetics, color printing, matte or glossy treatment.
Recyclability, single material PP, easy to recycle.
Ore sand and coal packaging: Heavy packaging such as coal and ore requires high-weight woven fabrics.
Performance requirements:
Ultra-high strength, weight≥120g/m², warp tension≥650N/5cm.
Abrasion resistance, enhanced by adding talcum powder or calcium carbonate.
Application of polyethylene resin in woven bags
Inner liner bags: Most PP woven bags use PE inner liner bags.
Performance characteristics
Barrier performance: The water vapor permeability of PE is 3-5 times lower than that of PP.
Heat sealing performance: The heat sealing temperature of PE (120-150℃) is lower than that of PP (160-180℃).
Flexibility: The PE inner bag can better fit the outer woven bag.
All-PE woven bags, all-PE woven bags are used in special applications.
Low-temperature application: PE remains tough at -50℃ and is suitable for frozen food packaging.
Impact-resistant packaging: LLDPE woven bags are used for fragile goods transportation.
Chemical resistance: Some chemicals (such as strong oxidants) are corrosive to PP, so PE is required.
Application of recycled plastics in woven bags
Pure recycled material woven bags
100% recycled materials can be used for low-end applications:
Garbage bags: low strength requirements.
Building dust nets: short-term use products.
Low-value agricultural product packaging: such as feed bags.
Mixed use of virgin and recycled materials
Usually 30% recycled materials + 70% virgin materials.
Advantages:
Balance cost and performance.
Meet environmental regulations in the EU and other places.
Need to add compatibilizer to improve interface bonding.
Key points for quality control of recycled plastics
Impurity content: metals, sand and gravel, etc. need to be controlled below 0.1%.
Melt index matching: The MFR difference between recycled materials and new materials should be less than 1g/10min.
Color control: Dark recycled materials are suitable for the production of gray or black woven bags.
Innovative application of functional plastic resins in woven bags
Anti-UV woven bags, by adding anti-ultraviolet agents to extend outdoor service life.
Anti-static woven bags, used for packaging sensitive items such as electronic components and explosives.
Flame-retardant woven bags are used in places with high fire protection requirements.
Application of degradable plastics in woven bags
PLA (polylactic acid): derived from corn starch, with high transparency but high brittleness.
PBAT (polybutylene adipate/terephthalate): good flexibility, often blended with PLA.
PBS (polybutylene succinate): processing performance is close to PP.
Starch-based plastics: low cost but poor water resistance.
Conclusion
As the basic material of woven bags, the selection of plastic resin directly affects the performance, cost and environmental friendliness of the product. Enterprises need to select suitable materials based on specific application requirements, comprehensively considering mechanical properties, processing characteristics, cost factors and environmental protection requirements. If you have any requirement, feel free to contact us for further details.