The premise for upgrading packaging bags is the understanding of packaging materials; it's truly useful!

Packaging is less about solving current problems and more about addressing the continuous problems of the past, present, and future. Packaging materials and forms constantly evolve with consumer habits, the needs of distributors' transportation and warehousing, and the requirements of government regulatory agencies. The functional properties of packaging materials directly drive the functional development of the flexible packaging industry. Below, Shunxingyuan Packaging, a professional flexible packaging manufacturer, interprets several commonly used packaging materials to help enterprises achieve Packaging upgrade.

1. PE Film Material

 

 

 

Heat-sealable PE materials have evolved from single-layer blown films to multilayer co-extruded films. This allows for differentiated design of the inner, middle, and outer layers. Different types of polyethylene resin blends can produce films with different sealing temperatures, heat-sealing temperature ranges, anti-seal contamination properties, heat-seal strengths, and anti-static effects, meeting the specific product packaging requirements and diverse functional properties of PE film materials.

In recent years, biaxially oriented polyethylene (BOPE) film has also been developed, improving the tensile strength of polyethylene film and exhibiting high heat-sealing strength.

2. CPP Film Material

 

 

 

CPP materials are often used in moisture-proof lightweight packaging structures like BOPP//CPP, but different CPP resin formulations can also produce films with different functional properties, such as improved low-temperature resistance, high-temperature cooking resistance, lower sealing temperature, high puncture resistance, and corrosion resistance. In recent years, the industry has also developed matte CPP films, enhancing the visual presentation of single-layer CPP film packaging bags.

3. BOPP Film Material

 

 

 

The most commonly used materials in lightweight composite films are ordinary glossy BOPP films and matte BOPP films, as well as BOPP heat-sealable films (single-sided or double-sided heat-sealable), and pearlescent BOPP films. The biggest advantage of BOPP is its high tensile strength (suitable for multicolor printing) and excellent water vapor barrier properties, making it widely used as a surface printing material for moisture-proof lightweight packaging.

Matte BOPP film has a matte decorative effect similar to paper. BOPP heat-sealable film can be used as a single-layer packaging material, such as for inner packaging of candies. Pearlescent BOPP film is often used as a heat-sealing layer material for ice cream packaging, eliminating the need for white ink printing. Its low density and sealing strength of 2～3N/15mm make the packaging bag easy to open and remove the contents. In addition, BOPP functional films such as anti-fog BOPP film, holographic OPP laser film, PP synthetic paper, and biodegradable BOPP film are also being promoted in specific areas.

4. PET Film Material

 

 

 

Ordinary 12μm PET glossy film is widely used in composite flexible packaging. The mechanical strength of its composite products is far higher than that of double-layer BOPP composite products (slightly lower than that of double-layer BOPA composite products), and its oxygen barrier ability is 20～30 times lower than that of BOPP//PE(CPP) composite films.

PET material has excellent heat resistance and can produce packaging bags with good flatness. Functional products such as PET heat-shrinkable film, matte PET film, high-barrier polyester film, PET twist film, and linearly tearable PET film are also used.

5. Nylon Film

 

 

 

Biaxially oriented nylon film, with its high strength, high puncture resistance, high-temperature resistance, and good oxygen barrier properties, is widely used in vacuum, water-boiled, and steamed packaging bags. For most large-capacity packaging of 1.7kg or more, the BOPA//PE structure is also used to obtain good drop resistance.

Cast nylon film is widely used in Japan for the packaging of frozen foods, exhibiting excellent low-temperature resistance and reducing the breakage rate of packaging bags during low-temperature transportation and storage.

In addition, products such as easily bonded (ONM), linearly tearable (NC), gas barrier (DCR, M, E), and double-sided corona (ONBC) types developed by U-Long Jike have expanded the application range of standard BOPA films.

6. Metallized Film

 

 

 

Vacuum metallization forms a dense aluminum layer on the surface of a film (such as PET, BOPP, CPP, PE, PVC, etc.), greatly increasing the film's barrier properties against water vapor, oxygen, and light. The most commonly used materials in composite flexible packaging are VMPET and VMCPP. VMPET is used in three-layer composites, and VMCPP is used in two-layer composites. The OPP//VMPET//PE structure is now maturely applied to vacuum-boiled packaging of pickles and bean sprouts. To overcome the shortcomings of ordinary metallized products, such as easy aluminum layer migration and poor water-boiling resistance, VMPET products with a bottom coating have been developed. Their peel strength before and after water boiling can reach more than 1.5N/15mm, and the aluminum layer does not migrate, enhancing the overall barrier performance of the packaging bag.

7. Aluminum Foil

 

 

 

Aluminum foil used in flexible packaging generally has a thickness of 6.5μm or 9μm. Aluminum foil is theoretically a high-barrier material, with water, oxygen, and light permeability all being "0". However, in practice, aluminum foil has pinholes and poor folding and pinhole resistance, resulting in some situations where the actual barrier packaging effect is not ideal. The key to applying aluminum foil material is to avoid pinholes during processing, packaging, and transportation, thereby reducing the actual barrier ability. In recent years, there has been a trend of replacing aluminum foil materials with more economical packaging materials in traditional application areas.

8. Coated High-Barrier Films

These mainly include PVDC-coated films (K-coating films) and PVA-coated films (A-coating films).

PVDC has excellent oxygen barrier and moisture-proof properties, as well as excellent transparency. The base films used for PVDC-coated films are mainly BOPP, BOPET, BOPA, and CPP, but they can also be PE, PVC, or cellophane. The most commonly used films in composite flexible packaging are KOPP, KPET, and KPA films.

High-saponification polyvinyl alcohol (PVA) molecules have a highly regular and polar structure, making them easy to crystallize and thus exhibiting high barrier properties against non-polar gases such as oxygen. Under dry conditions, the oxygen permeability coefficient is only 6.2 × 10 -17 ml·cm/(cm 2 ·S·cmHg), significantly lower than that of commonly used PVDC, PET, and PE resins in packaging materials. The oxygen permeability coefficients of PVDC, PET, and PE are 5.3×10 －13 、2.0×10 －12 、2.5×10 －10 ml·cm/(cm 2 ·s·cmHg). PVA coated films have achieved industrial-scale production.

9. Co-extruded high-barrier films

Co-extrusion is a molding method for preparing composite films by using two or more extruders to melt and plasticize two or more different plastics and then feeding them into a single die. Co-extruded barrier composite films are usually composed of three categories of materials: barrier plastics, polyolefin plastics, and adhesive resins. Barrier resins mainly include PA, EVOH, and PVDC.

The above are only the most common packaging film materials. In fact, at least oxide vapor-deposited films, PVC, PS, PEN, and paper are also used, and different functional film materials can be obtained from the same resin by different processing methods and different formula modifications. By laminating different functional films, functional composite flexible packaging materials that meet the packaging needs of different contents can be produced through dry lamination, solvent-free lamination, and extrusion lamination.