As an important carrier of modern commercial circulation, the material selection of plastic packaging bags directly affects product protection, safety and environmental protection. The following is a systematic analysis of plastic packaging bag materials from aspects such as mainstream material characteristics, functional compatibility, safety standards, and development trends. ​

I. Classification and Characteristics of Mainstream Plastic Materials

The materials of plastic packaging bags can be classified by chemical structure into polyolefin type, polyester type, vinyl type, etc. Each material presents unique properties due to the differences in its molecular structure. ​

(1) Polyolefin type: The most widely used basic material

Polyethylene (PE)

Classification and Characteristics:

Low-density polyethylene (LDPE) : With a density of 0.910-0.925g/cm³, it is soft and transparent, resistant to low temperatures (-60℃), but has relatively poor heat resistance (≤70℃). It is often used in cling film and plastic bags. ​

High-density polyethylene (HDPE) : With a density of 0.941-0.965g/cm³, it features high hardness, wear resistance, and heat resistance up to 120℃. It is suitable for supermarket shopping bags and industrial packaging bags. ​

Advantages: Non-toxic and odorless, low processing cost, strong recyclability (recycling code 04), with a global recycling rate of approximately 30%. ​

Polypropylene (PP

Characteristics: Density 0.89-0.91g/cm³, excellent chemical resistance, heat resistance up to 160℃, suitable for microwave oven heating packaging. ​

Application: Food packaging bags (such as bread bags) and clothing packaging bags often enhance transparency and strength through the biaxial stretching process (BOPP), with tensile strength reaching over 40MPa. ​

(2) Polyester: Representative of high strength and barrier properties

Polyethylene terephthalate (PET)

Characteristics: High transparency (light transmittance > 90%), tensile strength up to 50MPa, oil and water resistant, gas barrier property better than PE/PP, commonly used in beverage bottles and vacuum packaging bags. ​

Environmental friendliness: Recyclable (Recycling code 01), but it is necessary to note that it should be recycled separately from other plastics. The global PET bottle recycling rate is approximately 55% (OECD data 2023). ​

Polyamide (PA, nylon)

Characteristics: Excellent wear resistance (coefficient of friction 0.15-0.3), strong puncture resistance, often combined with PE to make high-barrier packaging, such as meat vacuum bags, oxygen transmission rate ≤5cm³/(m² · 24h · 0.1MPa). ​

(3) Vinyl type: Special functional materials

Polyvinyl chloride (PVC)

Characteristics: By adding plasticizers, it can be made into soft materials (such as cling film) or hard materials (such as boards), but it contains chlorine and releases toxic gases such as dioxins when burned. The European Union has restricted its use in food packaging. ​

Current situation: In China, only non-food contact uses (such as garbage bags) are allowed, with the recycling code 03. Professional processing is required to prevent environmental pollution. ​

Polyvinylidene chloride (PVDC)

Characteristics: One of the best plastics in the world in terms of barrier performance, with an oxygen transmission rate of ≤1cm³/(m² · 24h · 0.1MPa), it is often used in the packaging of foods such as sausages and cheese that require a long shelf life, but the cost is relatively high (50% higher than PE). ​

Ii. Material Function Adaptation and Composite Technology

(1) Functional limitations of a single material

PE/PP: Insufficient barrier properties, not suitable for high-oil or easily oxidized foods (such as nuts, fried foods). ​

PET: It is prone to brittleness at low temperatures (< -20℃) and is not suitable for cold chain packaging. ​

(2) Breakthroughs in multi-layer composite technology

Different materials are combined through co-extrusion or dry lamination processes to optimize performance:

Typical structure:

PET/PE: The outer layer of PET offers strength and transparency, while the inner layer of PE has good heat-sealing properties and is used for snack packaging bags. ​

PA/PE: The PA layer is puncture-resistant and the PE layer is moisture-proof. It is suitable for packaging meat with bones. ​

Performance improvement: The tensile strength of the composite film can be increased by 30% to 50% compared with that of a single material, and the oxygen barrier property has been enhanced to ≤10cm³/(m² · 24h · 0.1MPa). ​

(3) Special functional materials

Anti-static plastic: With carbon nanotubes or antistatic agents (such as quaternary ammonium salts) added, the surface resistance is ≤10⁹Ω, and it is used for packaging electronic components. ​

Antibacterial plastic: Mixed with antibacterial agents such as silver ions and copper ions, it has an antibacterial rate of ≥99% against Escherichia coli and Staphylococcus aureus, and is suitable for fresh food packaging. ​

Iii. Safety and Environmental Protection Standards

(1) Food contact safety standards

Domestic regulations:

It is required to comply with GB 4806.7-2016, which stipulates that the residual monomer in the plastic resin should be ≤100ppm and the migration amount of additives should be ≤0.1mg/kg (such as antioxidant BHT). ​

Phthalate plasticizers are prohibited in infant and toddler food packaging, and the DEHP migration amount should be less than 0.05mg/kg. ​

International Certification

Regulation (EC) No 10/2011 of the European Union stipulates that the content of heavy metals (calculated as Pb) in plastics should be ≤0.1mg/kg, and they need to pass migration tests such as simulated gastric juice (pH1.2) and olive oil. ​

(II) Environmental Protection assessment

Recyclability

The recycling rate of single materials (such as pure PE) is high, while that of composite films is low (< 15%) due to the difficulty in delamination. The EU's "New Plastics Economy Action Plan" requires that all packaging be reusable or recyclable by 2030. ​

Degradability

Bio-based plastics such as polylactic acid (PLA) and PBAT need to pass the ASTM D6400 certification. Under industrial composting conditions, the biodecomposition rate within 180 days should be ≥90%, but the cost is 2-3 times higher than that of traditional plastics. ​

Iv. Material Development Trends

(1) Lightweighting and reduction

By optimizing the film thickness (such as reducing shopping bags from 0.06mm to 0.04mm), 50% more products can be produced per ton of material, while maintaining a tensile strength of ≥20MPa and reducing raw material consumption and carbon emissions. ​

(2) Bio-based alternative technologies

PLA industrialization: In 2023, the global PLA production capacity reached 1.5 million tons, with the cost dropping to 2.5 US dollars per kilogram (a 40% decrease compared to 2018), gradually replacing PET in mineral water bottles. ​

Chemical recycling of waste plastics: Converting PE/PP into olefin monomers through pyrolysis to achieve the "plastic-crude oil" cycle. Data from Circle Economy in Germany shows that chemical recycling can reduce the carbon footprint of plastics by 70%. ​

(3) Innovation in Intelligent materials

Temperature-indicating plastic: Thermosensitive pigments are added. When the temperature inside the package exceeds the critical value of the food's shelf life (such as refrigerated food > 4℃), the color will automatically change with an error of ≤±0.5℃. ​

Blockchain traceability material: NFC chips are embedded in plastic particles to record information such as raw material sources and production batches. Consumers can scan the code to view the full life cycle data. ​

V. Conclusion

The selection of plastic packaging bag materials is an art of balancing technology, economy and environmental protection. In the future, with the advancement of the "dual carbon" goals and the development of a circular economy, bio-based plastics, recyclable composite materials, and intelligent functional materials will become mainstream. Enterprises should be guided by GB/T 38082-2019 "General Rules for Sustainability Evaluation of Plastic Packaging", build a green supply chain from the source of materials, minimize environmental load while meeting functional requirements, and promote the transformation of the plastic packaging industry towards safety, low-carbonization and intelligence. ​

This covers the classification, functions, safety and trends of plastic packaging bag materials. If you need to supplement specific material cases (such as agricultural mulching film, medical packaging) or details of testing standards, please feel free to inform us at any time for further expansion. ​