Definition, Selection, and Application Analysis of Composite Packaging Materials

Composite materials are two or more materials that have been combined together through one or more composite processes to form a composite material with certain functions. Generally, it can be divided into base layer, functional layer and heat sealing layer. The base layer mainly plays the roles of aesthetics, printing, moisture barrier and so on. Such as BOPP, BOPET, BOPA, MT, KOP, KPET, etc.; Functional layer mainly plays a role in barrier, light avoidance, such as VMPET, AL, EVOH, PVDC, etc.; heat sealing layer in direct contact with the packaged goods, adaptability, resistance to penetration, good sealing properties, as well as transparency and openness and other functions, such as LDPE, LLDPE, MLLDPE, CPP, VMCPP, EVA, EAA, E-MAA, EMA, EBA and so on. The following is a brief description of the inner layer material development, development and current status of composite flexible packaging materials.

Selection

Because the composite packaging materials involved in the raw materials are more varied, the nature of the different, which materials can be combined, or can not be combined, with what things to bond, etc., the problem is more and more complex, so they must be carefully selected to obtain the desired results. The principles of selection are: (1) clear packaging objects and requirements. (2) Selection of suitable packaging raw materials and processing methods; (3) the use of appropriate adhesives or laminating materials.

Application

For short-term circulation and consumption of yoghurt, plastic packaging materials can be used for packaging. Commonly used in yoghurt packaging plastic materials, including monomer plastic materials and multi-layer plastic composite materials (such as multi-layer composite polyethylene materials). Plastic packaging materials packaging yogurt belongs to the one-time sales package, and generally need to be stored and sold at low temperatures, common recommended preservation temperature of 2 ~ 4 ℃, 2 ~ 6 ℃, 2 ~ 8 ℃ and 0 ~ 4 ℃ and other temperature ranges, of which the temperature range of 2 ~ 6 ℃ is the most common; common recommendations for the shelf-life of 14 days, 16 days, 20 days, 24 days, 30 days and other preservation period, the most common of which are 14 days (generally stored at 2 to 6°C), and less commonly 30 days (generally stored at 0 to 4°C).

Plastic materials have many advantages and characteristics compared with paper, glass and metal materials, such as good transparency, good water and moisture resistance, good resistance (such as oil resistance, drug resistance, low temperature resistance), good processability and suitable mechanical strength, at the same time, plastic materials are cheap and small specific gravity. Of course, plastic materials in terms of corrosion resistance is not as good as glass materials, mechanical strength is not as good as metal materials, in the printing suitability is not as good as paper, but as long as a reasonable choice, and combined with advanced plastics handling and processing technology, plastic materials in yoghurt and other dairy products have a broad application prospects.

Commonly used in packaging yoghurt plastic materials or plastic composite materials are: ① polyethylene + titanium dioxide. In the production of polyethylene film, add white titanium dioxide produced by the polyethylene film has a certain light-blocking properties, you can play a certain role in shading, this is due to the white titanium dioxide makes the polyethylene film showing white translucent or opaque state, to a large extent, to improve the polyethylene materials on the shortcomings of the packaging of yoghurt (transparency) to adapt to the opaque yoghurt packaging materials requirements. ② Multi-layer composite high-density polyethylene materials. Commonly used mainly three-layer structure of high-density polyethylene (the middle layer of black high-density polyethylene containing charcoal, the inner and outer layers of white high-density polyethylene containing titanium dioxide) and five-layer structure of high-density polyethylene

The main packaging forms of yoghurt packaging using plastic materials are bag type, bottle type and cup type, of which, the bag type packaging materials commonly used for polyethylene + titanium dioxide materials and multi-layer composite high-density polyethylene materials, bottle type packaging and cup type packaging materials commonly used for polyethylene materials and polystyrene materials, two kinds of materials.Flat bag packaging form The use of flat bag packaging yoghurt, generally printed sheet plastic film installed in the automatic filling machine packaging material supply parts, in the process of packaging to complete the bag making, filling and sealing operations, bag sealing method is mostly the back of the middle of the sealing, sealing at both ends of the way. This packaging method of packaging costs are low, packaging technology and packaging technology is mature, easy to operate. Flat bags are generally simpler decorative design and printing, and the pattern is continuous, generally to ensure that each bag has a complete pattern.

Flat bags of yoghurt packaging, the capacity of each bag (packaging specifications) generally to the net content of "how many grams" or "how many millilitres" marked on the bag, such as common: 125 grams, 227 grams, 250 grams, 125 ml, 243 ml, 250ml, etc. At the same time, this form of packaging, often more than one pouch (common four bags, five bags, six bags, eight bags, ten bags) into a larger transparent plastic bag as a sales unit for packaging; sometimes, some brands of yoghurt have a range of flavours, such as plain, strawberry, taro, pumpkin, peach, apple, lychee and so on, in the collection of packaging, but also often different flavours! In the collection of packaging, but also often the different flavours of the sachets bagged yogurt into a large bag as a packaging unit or sales unit for packaging.

Three-sided sealing of the column bag packaging This bag type packaging is commonly used in the packaging of soya milk, yoghurt packaging in the application of more and more. In the production process, the use of advanced "inflatable pressure filling" process filling, is the printed two sheets of plastic film for the alignment of heat sealing, the first two sides of the longitudinal sealing, and then one end of the transverse sealing, and then the sealing of one end of the bag, the size of one end of the bag is gradually shrinking, the final formation of the size of the straw and the size of a similar small mouth. The bag is cylindrical in shape, with a very small cut in the mouth of the bag to facilitate tearing, and when drinking, it can be gently torn from the cut to drink. This form of packaging is generally only a simple decorative printing, and in the opening printed with "beware of splashing" and other warnings (due to the use of pressure filling process for filling, so the air pressure inside the container is slightly higher than the atmospheric pressure, the opening of the yoghurt is easy to splash).

Yoghurt packaged in columnar bags with three-sided sealing, with specifications of 250 g or 250 ml per bag, and similar to flat-bag yoghurt, this form of packaging is often used for yoghurt of the same flavour in multiple bags, or yoghurt of different flavours in combination with multiple bags, to be packaged as a sales unit.