Application of plastic packaging materials in food

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Analysis on the application of plastic packaging materials in food packaging

the food industry is an important part of China's national economy. The food packaging industry has a close and inseparable relationship: on the one hand, the development of food packaging is restricted by the development of food industry; On the other hand, good packaging can promote the development of a certain food industry

in China, with the development of food industry, food packaging industry has also received corresponding attention and development. Great progress has been made in food packaging materials, packaging containers, packaging theory, packaging research, packaging education, packaging design, packaging technology, packaging machinery, etc. With the continuous development of social production, the continuous improvement of people's lives, and the continuous expansion of foreign trade, especially today after China's entry into WTO, the development of food packaging plays an increasingly prominent role in the national economy and the people's livelihood. At the same time, countries all over the world also attach great importance to the development of food packaging, which has formed a worldwide technical and high-intelligent industrial field. In the past decade, China has also made a qualitative leap in food packaging, especially in the rapid development of plastic materials in food packaging

plastic is a plastic polymer material. Compared with traditional paper, metal and glass, plastic is a new packaging material. All kinds of packaging films, bags, barrels, boxes, bottles, cans and composite packaging materials made of plastic are widely used in the field of food packaging, and the consumption is increasing year by year. The reason why plastic packaging materials are widely used in food packaging all over the world is that plastic packaging has different excellent characteristics from other packaging materials:

(1) it has excellent physical properties. Plastic has certain strength and elasticity, wear resistance, vibration, and certain barrier properties

(2) its chemical stability is relatively good. Most plastics are resistant to acid, alkali and chemical agents, and also have certain resistance to grease

(3) the relative density of light plastic is only 1/5 of metal and 1/3 to 2/3 of glass. The packaging container is light in weight, convenient for storage, transportation, sales, and easy to carry

(4) easy processing and molding can adopt extrusion, reverse injection, blow molding, thermoforming, composite and other processing methods to process plastic into film, sheet, hollow container, composite and other packaging products

(5) beautiful promotional plastic is easy to be processed into various appearance shapes, which can be dyed or colored, printed and decorated, and the application of transparent plastic packaging can also increase the aesthetic effect of goods

of course, some plastic materials also have problems in health and safety, and plastic packaging waste also has a great impact on environmental protection. Thus, the use of plastic packaging materials in some food packaging fields is affected. However, with the continuous emergence of new plastic materials, the scope of application of plastics in food packaging will be greatly expanded

I have been engaged in the marketing of plastic bag cultivation materials for more than ten years. During this period, I have contacted many front-line production staff and technicians, including employees of plastic material production enterprises and plastic packaging material using enterprises. From them, I have learned a lot about new products of plastic packaging materials, and can basically understand the development trend of domestic plastic packaging materials. On this basis, I also carefully understand the main characteristics of plastic packaging materials, namely: 1. Mechanical properties include its tensile strength, elongation at break, impact strength, cracking strength, pricking strength, creep, stress relaxation, etc. 2. Barrier and permeability include permeability, permeability coefficient, moisture permeability, moisture permeability coefficient and light transmittance. 3. In order to withstand the past, the film needs to be deposited very thick first, with high temperature resistance and low humidity resistance. 4. Chemical stability and hygiene. And combine the observation in practice to analyze the application of plastic packaging materials in food packaging

polyethylene (PE), which is widely used in the market, is polymerized from ethylene. Due to different polymerization methods and densities, it is divided into low-density polyethylene (LDPE), high-density polyethylene (HDPE) and linear low-density polyethylene (LLDPE). Polyethylene has low transparency, certain air permeability, good moisture resistance, certain tensile strength and cracking strength, and good flexibility. Good chemical stability, insoluble in any organic solvent at room temperature, resistant to most acid and alkali, not resistant to concentrated nitric acid. It has good low temperature resistance (-70 ℃), easy to open processing, good heat sealing, but poor printability. Corona treatment or chemical surface treatment are often used to improve its printability. It is a non-toxic packaging material. Therefore, it is often used in the heat sealing layer and moisture-proof coating of composite materials. Linear low density polyethylene can also be made into film and film bags for packaging. At present, the inner layer of general food packaging is mostly PE or liquid crystal pendulum impact testing machine. Operation steps: CPP, etc. People have adopted its advantages of non-toxic, good moisture resistance, good flexibility and good heat sealing performance. Used as the inner layer of food composite packaging materials

polypropylene (PP), which is widely used in the market, is polymerized from propylene. It is a very light plastic with good transparency and gloss, excellent mechanical properties, tensile strength, hardness and toughness, and good heat resistance. It can be used continuously at a high temperature of 120 degrees and can be cooked in boiling water. Chemically stable, it is stable to acids, bases, salts and many solvents within a certain temperature range. Health and safety. Meet the requirements of food packaging. The gas barrier property of polypropylene is better than that of PE. But it is still poor. Poor cold resistance, easy to crack at low temperature. Polypropylene has poor printing performance and needs surface pretreatment before printing. Therefore, other materials are used in combination. Because this product has good physical properties and relatively low price, it has become the most widely used plastic film substrate for food bag cultivation. For example, it is used in the food packaging of instant noodles, biscuits, candy, dried fruits, potato chips, etc

polyester (PET), commonly known as polyester, is also widely used in the market. It has high transparency and good gloss. It has excellent gas and oil resistance and fragrance retention properties. It is rigid and ductile, and its tensile strength is 5-10 times that of PE and 3 times that of PA. Good chemical stability, resistant to dilute acid, alkali and ordinary organic solvents. Pet can maintain its excellent physical and mechanical properties in a wide temperature range. The normal use temperature range is -70-120 degrees, and it can be used at 150 degrees for a period of time. It has good hygiene and safety. Therefore, it is widely used in poultry packaging. The composite film based on pet can be used for cooking food packaging. Polyester bottles are widely used in beverage packaging

polyamide (PA), commonly known as nylon, has strong gas resistance, but poor barrier to water vapor, strong water absorption, and swells with the increase of water absorption, resulting in a sharp decline in gas and moisture resistance, and the stability of its strength and packaging size is also affected. It has good mechanical properties, toughness, wear resistance, cold resistance and heat resistance. The normal use temperature range is -60-130 degrees, and the maximum temperature can reach 200 degrees. Chemically stable, alkali resistant but not resistant to strong acids, water and alcohol. Easy to process, good printability, but poor heat sealing. It has excellent puncture resistance. The material is non-toxic and meets the requirements of food packaging on hygiene and safety. Therefore, it is widely used in food freezing packaging and cooking packaging. Because of its good printability and puncture resistance, many refined rice sold in the market now use nylon cast packaging bags

polyvinylidene chloride (PVDC) has outstanding advantages, that is, it has excellent barrier to gas, water vapor, oil and odor. Therefore, it is regarded as an important part of barrier composites in the market. It can also be made into lotion and coated on other substrates to improve the barrier property of materials. Its use temperature range is -18-135 degrees, which is resistant to low-temperature refrigeration and high-temperature cooking. It is often used in some aromatic and greasy food packaging, which can greatly extend the freshness and aroma preservation time of these edible Lu

the provincial government of polycarbonate issued the administrative measures for the identification of chemical industrial parks in Shandong Province. Fat (PC) has good transparency, excellent mechanical properties, stable size and good heat resistance. It is a very excellent packaging material, but its wide application is limited by its high price. It can be made into films, sheets, and containers with high impact resistance. It is generally used to make food trays, bowls and many other daily necessities

polyvinyl alcohol (PVA universal experimental machine does not do experiments for a long time) has high transparency, good gloss and excellent gas resistance. High strength and toughness. It has good chemical stability and is not eroded by common solvents such as hydrocarbons, alcohols and ketones, oil, etc. except for water. No static electricity, good printability. It is non-toxic and tasteless, and the film made of it can be directly used to package oily food. After compounding with other films, it overcomes the shortcomings of moisture permeability and improves the gas resistance. Therefore, it is widely used in the packaging of meat, butter, cheese and fast food

ethylene vinyl alcohol copolymer (EVOH), which is the hydrolysate of EVA, is a high barrier material. Its most outstanding advantages are its high barrier to oxygen, nitrogen, carbon dioxide and other gases and excellent fragrance retention. In addition, it has good resistance to oil and organic solvents, and can be used for the packaging of oily food and edible oil

in addition to the above plastic packaging materials, there are many other plastic packaging materials such as PVC, PS and many deep-processing products. In particular, many composites of the above products are more worthy of our study and discussion

composite flexible packaging materials composite flexible packaging materials refer to multi-layer materials composed of two or more layers of different flexible materials through certain technologies. The composite substrates used include plastic, aluminum foil, paper, cellophane, etc. In food packaging, plastic packaging materials combined with other materials account for a considerable proportion. Therefore, plastic packaging materials are widely used in food packaging. Has a very important position

the composite flexible packaging materials with the participation of plastic packaging materials have good comprehensive performance, high strength, high barrier, high and low temperature resistance, good adaptability of packaging operation, health and safety, and can meet the all-round requirements of food packaging for materials. The structural requirements of composite materials used for food packaging are as follows:

the inner layer materials are required to be non-toxic, tasteless, oil-resistant, chemical resistant, and have heat sealing and adhesion. Commonly used are thermoplastic materials such as PE, CPP, EVA, etc

the outer material requires good optical properties, good printability, and high strength and rigidity. The commonly used outer materials include pet, PA, BOOP, aluminum foil, paper and other materials

if the composite material is required to have high barrier property, an intermediate layer can be set. The commonly used intermediate layer materials are aluminum foil and PVDC with high barrier property

the expression of composites is: from left to right, from outer layer to inner layer. For example, pet/pvdc/cpp, the outer layer is pet, the middle layer is PVDC, and the inner layer is CPP. The composite process methods are generally lamination, coating, coextrusion, vacuum coating, etc. If you need to increase the shelf life of food, plastic composite packaging materials are an ideal choice

with the deepening of market economy, food packaging is also moving forward to practical, beautiful and cheap aspects. Many packaging technicians are constantly studying and discussing the application of new plastic packaging materials in food packaging. For example, new nano technology is introduced into plastic packaging materials. With time

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