How to Choose Various Plastic Packaging Films
- 2019-01-01
- Original
- 763
The protective function of packaging materials for commodities is a more important and basic function. It is no exaggeration to say that if a plastic film does not have a reliable protective effect on the packaged goods, it will lose its value as a packaging material. The protection function of plastic films on commodities is multifaceted. Different products and different packaging forms have different requirements for the protection functions of plastic packaging films.
Reliable mechanical protection includes preventing the leakage of goods in the package or the damage and pollution of the goods by foreign substances entering the package. Performance indicators that directly reflect the mechanical protection function of plastic films are mainly the mechanical strength of the film, such as tensile strength, tear strength, drop impact strength (drop impact), and puncture resistance.
Good welding strength is also a necessary condition for plastic film bags to reliably protect goods. If the strength of the weld is insufficient, the weld will become the fatal weakness of the plastic film bag, and the plastic bag will lose its protective effect on the goods due to the weld seam rupture. Ordinary polypropylene biaxially stretched film has good mechanical strength, but biaxially stretched polypropylene single film is generally not used as a bag because of poor welding performance.
The welding performance of plastic film is usually expressed by the strength of the weld, that is, N / 15mm. The higher the strength of the weld, the better the welding performance.
Among other functions for product protection, other more commonly considered are barrier performance and light shielding performance.
Barrier performance refers to the performance of plastic films to prevent the transmission of oxygen, carbon dioxide, nitrogen and other gases, and aroma, water vapor and other substances. When the scope is not clear, generally refers to the barrier to non-polar gases such as oxygen, carbon dioxide and nitrogen. . For many products, especially food products, the barrier properties of plastic packaging films are an important factor for the long-term and effective storage of the packaged products. The packaging of fresh fruits and vegetables requires a moderate permeability of the film, properly inhibits breathing and enables the packaged items to maintain a certain metabolism without necrosis, thereby extending the freshness period. The more commonly used method for the barrier properties of plastic films is to measure the amount of a certain unit of film per unit area of film in a certain period of time under certain conditions of temperature and humidity. The barrier properties of plastic films to aroma. Usually, after the scented substance is sealed in a film bag, the time required for the aroma to pass through the film bag is measured. (The plastic bag is placed in a desiccator. Open it regularly to check the time. Is the fragrance retention time), the longer the fragrance retention time, the better the barrier property of the film to the fragrance transmission. Shading students are also very important for the packaging of some products. Light, especially ultraviolet light, is an important reason for the discoloration, discoloration and oxidative deterioration of some substances, so it needs to be paid attention to. The light-shielding property is measured by the light-transmitting property of a given wavelength. The light-transmitting property is high and the light-shielding property is poor. The effect of plastic film on the display of goods is closely related to the light transmittance, haze, gloss, antistatic, and printability of the film itself, which needs to be paid enough attention.
Light transmittance and haze are important indicators that determine the visibility and sharpness of the packaged goods, and have a particularly strong relationship to the display effect of the goods. Both light transmittance and haze are expressed as percentages. The greater the value of the light transmittance, the better the transparency of the film; the larger the haze, the greater the turbidity of the object observed through the film, that is, the poorer the clarity.
Gloss indicates the reflective ability of plastic film when it is in love with light. It is expressed as the percentage of the light reflected by the sample in the direction of regular reflection relative to the standard surface. The larger the value of gloss, the better the brightness of the film surface.
As we all know, the printed patterns on the packaging can not be ignored for the promotion and display of goods. Roughly speaking, the printing performance of plastic film refers to the poor printing performance of the film, which requires surface pretreatment. Some films have good printing performance, and the surface can be printed directly without surface treatment.
The antistatic performance of the plastic film directly affects the dust absorption of the plastic film bag. Those with good antistatic properties are not easy to vacuum; if the antistatic properties are poor, they are easy to vacuum. Vacuuming will reduce the transparency, gloss, and sharpness of printed patterns of plastic film bags. Therefore, the good antistatic properties of plastic films are very important to maintain the good display effect of packaging bags for a long time. When a good display effect is desired, a film with good antistatic properties should be selected.
Antistatic properties of plastic films are expressed in terms of surface resistivity or charged half-life. The lower the surface resistivity and the shorter the charging half-life, the better the antistatic properties of the film.
With the continuous improvement of the production level, the application of automatic production lines has become increasingly widespread. When using mechanized, high-speed packaging, the adaptability of packaging films to packaging machinery must be taken seriously. The performance indicators that affect the adaptability of plastic packaging films to packaging machinery are mainly the smoothness and weldability of the films.
Good smoothness is beneficial to the smooth movement of the film in the packaging machine during packaging, and to avoid damage due to excessive resistance during its movement. The smoothness of a film can be described by its friction coefficient. The smaller the coefficient of friction, the better the slip performance.
The thermal welding performance mentioned here not only refers to the fact that the plastic packaging film can be heat-sealed, or after heat sealing, it is a problem that it can reach a sufficiently high welding strength, but often also requires the plastic packaging film to be heat-sealed. , Allow a larger temperature range during heat sealing and a larger pressure range for heat sealing. Although some films can be heat-sealed and can obtain higher welding strength, the heat-sealing conditions are harsh and cannot be used well with packaging machinery. Full attention should be paid to this.
Refers to the special requirements for packaging films based on the needs of specific commodities, which are mostly in the scope of some special requirements. Due to their special characteristics, they are introduced separately. Such requirements include the compatibility of plastic films with their contents, the adaptability of plastic films to the use environment, dielectric properties, hygienic properties, and restraint properties.
Often need to consider whether the plastic packaging film will be corroded, dissolved or swollen by the packaged material to lose its strength, and the plastic film will chemically react with the packaged material, which will reduce the performance of the product or the packaging bag will be damaged, etc. .
Often need to consider the high and low temperature resistance of the film, such as refrigerated, especially frozen food using plastic packaging film, need to have good low temperature resistance; plastic packaging film for cooking food, need to have good high temperature resistance and so on.
Commodities such as integration are easily punctured by static electricity in the packaging. Therefore, the plastic film used for packaging of such products must have good antistatic properties. The surface resistivity is generally controlled at about 108 ohms or lower.
When packaging food or pharmaceutical products, the plastic packaging film selected must have good hygienic properties and meet the requirements of relevant national health standards to ensure that the plastic film will not cause pollution to the packaged goods.
When using heat-shrink packaging and wrapping packages, packaging restraint is very important. Therefore, when selecting such films, attention should be paid to the shrinkage rate, shrinkage stress, and elastic recovery rate, etc., and selection should be made according to different conditions of the product. The binding force is insufficient, and the packaging (especially the collective packaging) is not tight; however, if the binding force is too large, the brittle and fragile items may be damaged.
On the premise of meeting the above-mentioned performance requirements, when selecting plastic packaging films, it is necessary to choose relatively low-price varieties as much as possible to save packaging costs, reduce commodity costs, and increase competitiveness. Blindly pursuing the "upscale" of packaging will obviously increase the production cost of the product, but it is meaningless to improve the packaging effect of the product, and it must be avoided.
The widespread application of plastic packaging materials has made positive contributions to the industrial and agricultural production and the improvement of people's living standards. However, it has also exerted a significant negative impact on the living environment of human beings and caused a great burden on the environment. Therefore, in selecting plastic packaging films, in addition to considering the above-mentioned principles, we must also attach great importance to the adaptability of plastic films to environmental protection.
When selecting plastic film, we must first grasp the characteristics of the product and its basic requirements for packaging. At the same time, we must have a clear understanding of the basic properties and main characteristics of plastic packaging films, especially commonly used plastic packaging films. In this way, a more ideal plastic packaging film is selected.
It should be emphasized that it is necessary to pay attention to the fact that there are many kinds of goods, and the requirements for different kinds of goods are also various, and some are even completely opposite, so there is not a plastic film that can perfectly suit for all commodity packaging applications. Welcome to contact us for further discussion with your spefic demands.
