Noticias

Composite packaging films are required for poultry products, tea and coffee products, baked foods, dry goods and frozen foods. There is a wide range of food preservation technologies, such as vacuum packaging, modified atmosphere packaging, food dehydration packaging, aseptic filling, retort packaging, hot liquid filling and so on. Plastic packaging materials are essential for all these packaging processes, and the proper selection of barrier resins is a critical factor.

1、Selection Principles

(1) Choose barrier materials according to food types.

(2) Select different materials based on food usage scenarios: separate materials are needed for microwave-retortable food and frozen food.

(3) Pick packaging films by evaluating the comprehensive performance of barrier resins.

• Aluminum foil: Top-tier barrier performance, retort-resistant, UV-blocking and opaque. It has poor fold resistance, high material cost and cannot be used for microwave heating.
• Metallized film: Excellent fold resistance, barrier performance close to aluminum foil, UV-shielding and opaque. Its metallic coating has weak bonding strength, and it is incompatible with microwave heating.
• 5-layer co-extruded EVOH film: Outstanding barrier properties, good oil and organic solvent resistance, antistatic and recyclable. Its barrier performance drops drastically when ambient relative humidity exceeds 50%, with high equipment investment and raw material cost.
• Nano-polyamide: Good oxygen barrier, improved water vapor barrier performance, oil and solvent resistance. It only supports a single film-forming process, hard to recycle, and the related manufacturing technology remains immature.
• PVDC coated film: Balanced oxygen and water vapor barrier properties, heat-sealable coating layer and relatively low cost. Special coating production equipment is required, and the film cannot be recycled.
• Silicon oxide / aluminum oxide coated film: High transparency with excellent oxygen and moisture barrier performance, yet the finished product cost is extremely high.

• Modified PVA coated film: Superior oxygen barrier, low cost, excellent aroma retention, oil and solvent resistance. The coating layer is thin and needs protective lamination with PO films.
   
  (4) Storage environment of packaged food

   

  The relative humidity of the storage environment must be taken into account. Test results show that EVOH (38% ethylene content) outperforms PVDC in oxygen barrier at relative humidity of 0~70%. Once relative humidity rises above 70%, EVOH’s barrier capacity deteriorates rapidly and becomes inferior to PVDC. At 80% RH, PVDC’s oxygen barrier performance is 3 times that of EVOH; at 100% RH, PVDC delivers 13 times better oxygen barrier than EVOH.
   
  For meat packaging in particular: the external ambient relative humidity stands at 60%~70%, while the internal humidity of meat products reaches 95%~100%. The relative humidity inside the laminated film layers usually exceeds 70%. Therefore, PVDC is far more suitable than EVOH for meat product packaging.
   
  (5) Cost of barrier resins

   

  Generally, PVDC is cheaper than EVOH. Cost-effective barrier materials are prioritized in mass production.