Application of packaging materials for the hottest

Application of packaging materials for fast food

fast food, also known as convenience food, usually has the characteristics of storage and transportation, convenient use, long shelf life and moderate price. The development and application of fast food meet the needs of the rapid pace of society. Fast food is generally processed food, which has developed rapidly in recent years. When we step into any supermarket or convenience store, we see a variety of vacuum packaged food, nitrogen filled packaged food, deoxidized packaged food, cooked packaged food, microwave food, etc. The development and utilization of fast food can not only bring great benefits to the majority of consumers, but also help to improve the grade of goods, enhance the market competitiveness of goods, and create more profits for producers. Therefore, it has developed very rapidly and has become a bright spot in the recent development of the food industry

modern convenience food requires a long shelf life and is easy to open. The production and utilization of most products are closely related to packaging materials. It can be said that the rapid development of fast food has provided a wide range of markets and many development opportunities for the development of packaging materials. At the same time, it is also the development and research results of packaging materials, especially plastic composite packaging materials, that promote the production and application of fast food to become a reality. In order to adapt to the development of fast food, the packaging of fast food is further developing in the direction of convenience, safety, hygiene, extending the shelf life of food and reducing costs; At the same time, green packaging, which is suitable for the sustainable development of human society, is increasingly favored by people, and its research, development and application have increased greatly

here are the basic information of several packaging materials closely related to fast food: barrier packaging materials, easy to open packaging materials and packaging materials for microwave ovens

first, barrier packaging materials

the performance of packaging materials to block oxygen has a great impact on the storage period of processed food. On the one hand, the growth and reproduction of bacteria is a major cause of food spoilage, and the existence and concentration of oxygen is a necessary condition for bacteria to survive and reproduce; On the other hand, oxidative deterioration of oil and other components in food is often another important reason for food spoilage. Therefore, in order to extend the shelf life of processed food, high barrier packaging materials should be selected when selecting packaging materials. The gas barrier of packaging materials is usually characterized by the air permeability of packaging materials, that is, under the condition of 0.1 MPa (1 atmospheric pressure) gas pressure difference on both sides of the packaging materials, the milliliters of gas passing through per square meter and 24 hours. The greater the air permeability, the worse the barrier; On the contrary, the smaller the air permeability, the better the barrier. As for the distinction between high barrier, medium barrier and low barrier, there is no strict definition so far. From a practical point of view, some people call a film with a thickness of 2.5 wires (0.025 mm) whose air permeability is less than 5cm3/(M2.24h..0.1mpa) as a high barrier packaging material; If the air permeability is between 5 -200cm3/(M2.24h..0.1mpa), the electric machine should be grounded and installed as barrier packaging material; Those with air permeability greater than 200cm3/(M2.24h..0.1mpa) are called low barrier packaging materials. The moisture permeability of packaging materials also has a significant impact on the quality of many foods. Controlling the moisture in food within a certain range can not only maintain the flavor of food, but also block the entry of moisture. Because the existence of water often contributes to the reproduction of bacteria and accelerates the deterioration of food, many foods need to be preserved in a dry state. Packaging materials are required to have good performance of blocking water vapor, which can effectively prevent the water vapor in the air from entering the food

II. Composite packaging materials

1. Composite packaging materials containing aluminum foil

traditional aluminum plastic composite packaging materials, which contain aluminum foil layer, are the most barrier packaging materials in common use. Their oxygen and moisture permeability are close to zero, and can prevent the transmission of visible light and ultraviolet light. In addition to preventing the deterioration of food caused by the entry of oxygen and water vapor outside the food packaging container, it can also prevent the deterioration of photosensitive components in food caused by the action of visible light and ultraviolet light, which has extremely excellent protection for the packaged food. Moreover, when high temperature resistant resin, such as polypropylene, is selected as the heat sealing layer, the composite material based on aluminum foil has digestibility. Therefore, it has a wide market in the packaging of convenience food. So far, it is widely used in cooking packaging, vacuum packaging, gas replacement packaging and other fields

aluminum plastic packaging materials also have many shortcomings. The most obvious one is the poor folding resistance of aluminum-plastic composite packaging materials containing aluminum foil. When the aluminum-plastic composite film or aluminum-plastic composite bag is folded, cracks will occur because of the aluminum foil, resulting in a significant decline in barrier performance. In addition, aluminum foil is not transparent, which prevents the transmission of visible light and ultraviolet light, and has a good protective effect on photosensitive components in food. However, at the same time, it loses the display function of packaging, and people can't observe the situation of food through packaging, which is detrimental to improving the purchasing desire of consumers

2. Composite packaging materials with aluminum coating

in order to solve the problem that the barrier performance is greatly reduced due to the fracture of aluminum foil, people have successfully carried out vacuum aluminum plating (also known as vacuum aluminum spraying) on the surface of plastic film, mainly on the surface of PET film taking into account planned ports, port industrial parks and BOPP film, to manufacture composite flexible packaging materials with aluminum coating. This material has the performance of blocking oxygen, water vapor and light transmission close to the composite flexible packaging material containing aluminum foil. When it is folded, it is not easy to produce cracks, and its inherent high barrier property can still be maintained. This composite material with vacuum aluminized coating also has better gloss, and through the coloring of aluminized base film, it can obtain golden yellow and silver ordinary performance PBT plastic, which is difficult to meet the requirements of white, bright red and other colors to meet the needs of decoration. In addition, because the thickness of the aluminum coating is significantly lower than that of the aluminum foil, using the aluminum base film to replace the aluminum foil to produce high barrier composite packaging materials also has the characteristics of saving materials

for a long time in the past, China could only produce decorative aluminum-plastic composite packaging materials by vacuum aluminizing. Through the efforts of the majority of scientific researchers, breakthroughs have been made in the base film precoating and aluminizing process recently. They have mastered the practical technology of producing high barrier vacuum aluminizing, and have been able to produce a high barrier aluminizing base film with an aluminum coating thickness of 500 Angstroms

3. Composite packaging materials with inorganic coating

in order to manufacture highly transparent composite packaging materials with the same barrier as composite packaging materials containing aluminum foil, people have developed a base film containing evaporated aluminum oxide layer or silicon oxide layer (using physical or chemical methods, plating a layer of dense silicon oxide or aluminum oxide on the surface of pet thin film). The made composite film has extremely high oxygen resistance, moisture resistance, oxygen permeability and moisture permeability, and also has a high degree of transparency. The packaged goods can be clearly seen through the packaging, which has a good display effect on the goods. In addition, because the composite does not contain aluminum layer and has excellent microwave permeability, it can be well used in microwave food where aluminum composite packaging materials cannot be used

the common limitation in performance of composite packaging materials containing aluminum foil and inorganic coating is that they have the tensile molding performance of ordinary thermoplastic plastics (composite packaging materials containing aluminum foil cannot be thermoformed; composite packaging materials containing inorganic coating will have a significant decline in barrier performance and lose use value after thermoforming)

in addition to the above-mentioned characteristics, composite packaging materials containing aluminum foil and inorganic coating, especially composite packaging materials containing inorganic coating, have a common advantage, that is, they have good adaptability to environmental protection and are easy to dispose of packaging waste. Therefore, they are generally considered to be one of the most promising composite packaging materials

in the past, when producing composite packaging materials containing aluminum foil and inorganic coating, the dry compounding process of solvent based adhesive was often used. The discharge of its solvent would pollute the surrounding environment, and the residual solvent would degrade the hygienic performance of the packaging materials. With the continuous improvement of people's awareness of environmental protection, solvent-free compounding and dry compounding with water binder have been favored by people, and there is a trend to gradually develop to the mainstream process. (to be continued)