Application suitability of the hottest different p

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Applicability of different plastic packaging materials in the food industry (1)

the food industry is an important part of China's national economy, and 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 the 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 improvement of people's lives and the expansion of foreign trade, especially 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, and have 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

plastics are high molecular materials with plasticity. 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 amount 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, elasticity, wear resistance, vibration, and certain barrier properties

(2) it has good chemical stability. 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 that of metal and 1/3 to 2/3 of that of glass. The packaging container is light in weight, easy to store, transport, sell and carry

(4) easy processing and forming 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) aesthetic promotional plastic is easy to be processed into various appearance shapes, which can be dyed or colored, printed and decorated. Transparent plastic packaging can be used to increase the aesthetic effect of goods

of course, some plastic materials also have problems in health and safety, and plastic packaging waste still has a great impact on environmental protection. This has affected the use of plastic packaging materials in some food packaging fields. However, with the continuous emergence of new plastic materials, the 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 the employees of plastic material production enterprises and plastic packaging material users. From them, I have learned a lot about the new products of plastic packaging materials, and can basically understand the development trend of domestic plastic packaging materials. On this basis, I have also carefully understood the importance of plastic packaging materials, namely: 1. Mechanical properties include its tensile strength, elongation at break, impact strength, cracking strength, pricking strength, creep four ball friction and wear tester working process change, stress relaxation, etc. 2. Barrier and permeability include permeability, permeability coefficient, moisture permeability, moisture permeability coefficient and light transmittance. 3. High temperature resistance and low humidity resistance. 4. Chemical stability and hygiene. The application of plastic packaging materials in food packaging is analyzed in detail

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 CPP. 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, stable to acids, bases, salts and many solvents within a certain temperature range. Health and safety. In line with the food bag, that is, the fixture for the experimental machine installed on November 23 has no fixed mode in structure, and the structure varies greatly according to different samples and experimental forces The specimen with large experimental force generally adopts inclined clamping structure, and the clamping force increases with the increase of experimental force. The gas resistance of polypropylene is better than that of PE. But it is still poor. Poor cold resistance, easy to crack at low temperature. The printing performance of polypropylene is poor. Surface pretreatment is required 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 packaging. For example, it is used in the food packaging of instant noodles, biscuits, candy, dried fruits, potato chips, etc

(to be continued)

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