Key points of the composite packaging bag combination standard

A composite packaging bag is composed of two or more materials combined through one or more dry lamination processes to form a composite packaging bag with specific functions.

I. Structure of Composite Packaging Bags Structure

Generally, it can be divided into base layer, functional layer, and heat-sealing layer.

Base layer: The base layer mainly plays a role in aesthetics, printing, and moisture resistance. Such as BOPP, BOPET, BOPA, MT, KOP, KPET, etc.;

Functional layer: The functional layer mainly plays a role in barrier and light protection, such as VMPET, AL, EVOH, PVDC, etc.;

Heat-sealing layer: The heat-sealing layer is in direct contact with the packaged goods, providing adaptability, permeability resistance, good heat-sealability, transparency, and openability, such as LDPE, LLDPE, MLLDPE, CPP, VMCPP, EVA, EAA, E-MAA, EMA, EBA, etc.

Composite packaging bags are packaging products that combine various packaging advantages, with low cost and exquisite printing;

II. Characteristics of Composite Packaging Bags Characteristics

This product has the characteristics of: anti-static, UV-resistant, moisture-proof, oxygen-barrier, light-shielding, cold-resistant, oil-resistant, high-temperature resistant, fresh-keeping, and good sealability;

III. Applications of Composite Packaging Bags Applications

Widely used in clothing and apparel packaging, industrial packaging, daily chemical packaging, food packaging, medicine, hygiene, electronics, aerospace, science and technology, military industry, and other fields;

IV. Types of Composite Packaging Bags Types

1. Classified by bag type and function

Stand-up pouches

Vacuum packaging bags

Stand-up spout pouches

Custom-shaped stand-up food pouches

Wine pouches

High-temperature retort pouches

Aluminum foil tea and coffee bags

Anti-static shielding bags for electronic products

UV-resistant bags for daily necessities

Stand-up hanging hook sports water pouches

Bone-attached zipper file bags

Milk, soy milk, and soy bean milk bags

2. Classified by material

Aluminum foil composite bags

Aluminum-plastic composite bags

Kraft paper aluminum foil composite bags

Woven bag composite bags

Pure kraft paper composite bags

Plastic aluminum-plastic composite bags (vacuum bags or aluminum foil bags) are packaging products that combine various packaging advantages, with low cost and exquisite printing. This product has the characteristics of anti-static, UV-resistant, moisture-proof, oxygen-barrier, light-shielding, cold-resistant, oil-resistant, high-temperature resistant, fresh-keeping, and good sealability.

Characteristics of Aluminum-Plastic Composite Bag Printing

High flatness, bright printing colors, can be equipped with zippers, partial matte, hot stamping and other special processes. Unique design, new printing technology, highlighting pattern design and trademark effect, can design special trademarks or patterns, playing a good anti-counterfeiting effect, and can better highlight the high-grade and unique shelf effect of the product.

V. Types of Aluminum-Plastic Composite Bags

1. Classified by material structure: pure aluminum bags and aluminum-plated bags (including paper-aluminum composite bags).

Pure aluminum composite bag structure: OPP/AL/PE; PET/AL/PE, etc.;

Aluminum-plated composite bag structure: PET/VMPET/PE; VMPET/CPP, etc.

2. Classified by function: anti-static product packaging bags, UV-resistant daily chemical product packaging bags, etc.

3. Classified by process structure: two-layer composite, three-layer composite, four-layer composite, and multi-layer composite, the material structure can be combined according to customer requirements.

4. Classified by bag type: three-side seal, stand-up pouch, spout pouch, custom-shaped pouch, center seal pouch, yin-yang pouch, mother-child pouch, special packaging bag, etc.

VI. Aluminum-Plastic Composite Bag Products of Classification and Application

The main classifications include vacuum aluminum foil bags, yin-yang aluminum foil bags, anti-static shielding bags, grid electrostatic bags, anti-vibration electrostatic bags, electrostatic aluminum-plated bags, and various daily chemical and industrial labels, etc.; applied in industrial packaging, daily chemical packaging, food packaging, medicine, hygiene, electronics, aerospace, science and technology, military industry, and other fields. Common aluminum-plastic bag products in life include the following varieties: stand-up pouches, vacuum packaging bags, stand-up spout pouches, custom-shaped stand-up food pouches, wine pouches, high-temperature retort pouches, aluminum foil tea and coffee bags, anti-static shielding bags for electronic products, UV-resistant bags for daily necessities, stand-up hanging hook sports water pouches, bone-attached zipper file bags, milk, soy milk, and soy bean milk bags, etc.

VII. Heat Sealing Quality of Composite Packaging Bags Control

The type, thickness, and quality of the heat-sealing material have a decisive impact on the heat-sealing strength. Commonly used heat-sealing materials for composite packaging bags include CPE, CPP, EVA, hot melt adhesive, and other ion-type resin co-extruded or co-blended modified films. The thickness of the heat-sealing material is generally between 20 and 80 μm, and in special cases, it can reach 100 to 200 μm. For the same heat-sealing material, the heat-sealing strength increases with the increase in heat-sealing thickness. The heat-sealing strength of retort pouches generally requires 40 to 50 Newtons, therefore, the thickness of its heat-sealing material should be above 60 to 80 μm.

Heat-sealing temperature has the most direct impact on heat-sealing strength. The high and low melting temperatures of various materials directly determine the minimum heat-sealing temperature of the composite bag. In the production process, due to the influence of heat-sealing pressure, bag-making speed, and the thickness of the composite substrate, the actual heat-sealing temperature used is often higher than the melting temperature of the heat-sealing material. The smaller the heat-sealing pressure, the higher the required heat-sealing temperature; the faster the machine speed, and the thicker the surface material of the composite film, the higher the required heat-sealing temperature. If the heat-sealing temperature is lower than the softening point of the heat-sealing material, it is impossible to truly seal the heat-sealing layer no matter how much pressure is increased or the heat-sealing time is extended. However, if the heat-sealing temperature is too high, it is easy to damage the heat-sealing material at the weld, causing it to melt and extrude, resulting in a "root cutting" phenomenon, which greatly reduces the heat-sealing strength of the seal and the impact resistance of the bag.

To achieve ideal heat-sealing strength, a certain amount of pressure is essential. For lightweight packaging bags, the heat-sealing pressure must reach at least 2 kg/cm², and it increases accordingly with the increase in the total thickness of the composite film. If the heat-sealing pressure is insufficient, the two layers of film cannot be truly fused, resulting in poor local heat sealing or difficulty in expelling air bubbles trapped in the weld, causing false welding; of course, the heat-sealing pressure is not the greater the better, it should not damage the weld, because at a higher heat-sealing temperature, the heat-sealing material at the weld is in a semi-molten state, and too much pressure easily squeezes away some of the heat-sealing material, causing the weld edge to be semi-cut, the weld becomes brittle, and the heat-sealing strength is reduced.

The heat-sealing time is mainly determined by the speed of the bag-making machine. Heat-sealing time is also a key factor affecting the sealing strength and appearance of the weld. With the same heat-sealing temperature and pressure, a longer heat-sealing time means that the heat-sealing layer is more fully fused and the bonding is stronger, but if the heat-sealing time is too long, it is easy to cause wrinkles in the weld, affecting the appearance.

If the weld after heat sealing is not cooled properly, it will not only affect the flatness of the weld appearance, but also have a certain impact on the heat-sealing strength. The cooling process is the process of shaping the weld that has just been heat-sealed at a certain pressure and lower temperature to eliminate stress concentration. Therefore, insufficient pressure, poor cooling water circulation, insufficient circulation volume, too high water temperature, or untimely cooling will all cause poor cooling, causing the heat-sealed edge to warp and the heat-sealing strength to decrease.

The more heat-sealing times, the higher the heat-sealing strength. The number of longitudinal heat-sealing times depends on the ratio of the effective length of the longitudinal welding rod to the bag length; the number of transverse heat-sealing times is determined by the number of sets of the transverse heat-sealing device of the machine. Good heat sealing requires at least two heat-sealing times. General bag-making machines have 2 sets of hot knives, and the higher the degree of overlap of the hot knife positions, the better the heat-sealing effect.

For composite films with the same structure and thickness, the higher the interlayer peel strength of the composite layer, the greater the heat-sealing strength. For products with lower composite peel strength, the weld failure is often caused by interlayer delamination of the composite film at the weld, causing the inner heat-sealing layer to independently bear the destructive tensile force, and the surface material loses its reinforcing effect, thus greatly reducing the heat-sealing strength of the weld. If the composite peel strength is large, interlayer delamination at the weld will not occur, and the actual heat-sealing strength measured will be much greater.