What are mesh produce bags made of？
In the circulation of agricultural products, a mesh bag made of polyethylene (PE) is becoming an important packaging tool for the transportation of fruits and vegetables worldwide. With its unique mesh structure, this kind of woven bag is widely used in the storage and transportation of agricultural products such as garlic, onion, potato, corn, watermelon, ginger and so on. Its special material characteristics and production process, so that in order to ensure the quality of the product at the same time, the perfect balance between environmental protection needs and practical performance.
First, the core material: the scientific analysis of polyethylene (PE)
As an important derivative of petrochemicals, polyethylene (Polyethylene) has become the material of choice for mesh bag manufacturing due to its excellent chemical stability. The two main raw materials used in the production process are High Density Polyethylene (HDPE) and Linear Low Density Polyethylene (LLDPE):
HDPE: with a compact molecular structure and a crystallinity of up to 90%, it gives the bags excellent tensile strength (up to 20-30MPa) and abrasion resistance, and is particularly suitable for loading heavy agricultural products such as watermelons and potatoes.
- LLDPE: unique short branched chain structure makes it has better flexibility (elongation at break can reach 500%), used for ginger, garlic and other perishable agricultural products packaging can effectively buffer the impact of transportation.
The two raw materials through the scientific ratio (common ratio of 7:3), combined with antioxidants, anti-ultraviolet agents and other modification additives, so that the finished mesh bag in the -50 ℃ to 80 ℃ temperature domain to maintain stability, weather resistance than the traditional sacks to enhance more than 3 times.
Second, precision manufacturing: the metamorphosis journey from granule to mesh
The modernized production line adopts five-layer process to create high-quality PE mesh bags:
- Raw material modification: Melt and mix PE pellets with masterbatch and functional additives in twin-screw extruder to form composite materials with anti-aging and anti-static properties.
- Film Forming : Extruding cylindrical film with thickness of 0.02-0.05mm through ring die, water cooling system precisely controls the crystallinity to ensure the subsequent tensile strength.
- Stretching and weaving : The longitudinal stretching unit forms warp threads with a 5:1 stretching ratio, and the transverse stretching forms weft threads, which are interwoven to form an adjustable mesh structure with an aperture diameter of 3-15mm.
- Heat-setting treatment: Stabilize the molecular orientation in the 120-150℃ hot air circulation system to eliminate the internal stress, so that the mesh shape is permanently set.
- Intelligent slitting : The laser cutting system cuts according to the preset size (common specification 25kg/50kg), and the error is controlled within ±0.5mm.
The air permeability of the mesh bag produced by this process can reach 3000-5000cm³/(m²-24h), which is twice as much as that of the traditional sacks, and effectively prevents fruits and vegetables from accumulating respiratory heat.
Third, the functional advantages: crack the agricultural products storage and transportation problems
- Micro-environment regulation: hexagonal grid structure forms air convection channels, which can control the humidity inside the bag in the ideal range of 75-85%, compared with airtight packaging, potato sprouting rate reduced by 40%.
- Mechanical adaptability: the warp knitting process makes the load-bearing capacity of more than 50kg, watermelon and other perishable products transportation breakage rate down to 0.3%, better than carton packaging 1.2%.
- Visualization supervision: 40% opening rate to achieve visual inspection of goods, with the implantation of RFID tags, so that the supply chain traceability efficiency increased by 60%.
- Green recycling: PE material can be 100% recycled, and a single mesh bag can be reused 5-8 times on average, reducing the life cycle carbon footprint by 75% compared with disposable cartons.
Fourth, globalization applications: regional characteristics and standards to adapt to
Different agricultural production areas have differentiated needs for bag specifications:
Dutch onion bags: 10mm diamond-shaped mesh with blue UV stabilizer to meet the long-term open-air storage in the humid climate of the North Sea.
Peruvian grape bags: special 5mm microporous structure, lined with food-grade PE film, complying with FDA 21CFR177.1520 standards.
China Garlic Bags: Red UV resistant mesh bags can effectively block 50% light intensity and inhibit garlic cloves photo-oxidation reaction.
International certification systems such as ISO 9001, BRC packaging standards to promote the development of PE mesh bags to functionality, flame retardant, antibacterial and other special mesh bags have occupied 15% of the European market share.
Fifth, the new trend of sustainable development
With the implementation of the EU SUP Directive, bio-based PE mesh bag R & D breakthroughs: extracted from sugarcane ethanol green polyethylene (Green PE) mesh bag, while maintaining the mechanical properties of the bio-carbon content of more than 85%. Together with the light-biological double degradation technology, the degradation cycle of traditional PE mesh bags has been shortened from 400 years to 3-5 years, and has been piloted in Walmart’s fresh food supply chain.
This PE mesh bags, which integrates material innovation and process upgrading, is reshaping the global circulation system of agricultural products. Its scientific design concept not only solves the practical problems in the storage and transportation of fruits and vegetables, but also provides an innovative sample for the sustainable development of agriculture through the circular economy model. With the integration and application of intelligent sensing, traceable printing and other technologies, PE mesh bags are evolving from simple packaging containers to intelligent carriers connecting fields and tables.
