How to choose plastic packaging film

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Knowledge: how to choose plastic packaging film there are many kinds of practical packaging plastic films. In the use of many plastic films, there are often mutual infiltration and mutual substitution, but the characteristics of various plastic films can not be ignored. So it is not easy to choose and apply plastic packaging film correctly. Its leading products are aluminum plates and strips for high-precision and high-performance wide range transportation (automobiles, rail vehicles, coal trucks, containers, oil tankers, shipbuilding, etc.), which requires the personnel in the packaging material industry to understand some of the corresponding basic functions of plastic packaging films, mainly the protection function of commodities, the promotion function, the adaptability to packaging machinery and other special applications. In addition, economic rationality and adaptability to environmental protection must be considered

the protective function of packaging materials for commodities is the most important and basic function. It can be said without exaggeration that if the plastic film has no reliable protective effect on the packaged commodities, it will lose its value as a packaging material. The protection function of plastic film for commodities is multifaceted. Different commodities and different packaging forms have different emphasis on the protection function requirements of plastic packaging film

reliable mechanical protection includes preventing the leakage of goods in the package or the damage and pollution of goods caused by external substances entering the package. The performance indicators that directly reflect the mechanical protection function of the plastic film are mainly the mechanical strength of the film (which can also be tested by the component fatigue testing machine), such as tensile strength, tear strength, falling impact strength (falling impact) and puncture resistance

good welding strength is also a necessary condition for plastic film bags to reliably protect commodities. If the weld strength is insufficient, the weld will become the fatal weakness of the plastic film bag, and the plastic bag will lose its protection to the commodity due to the crack of the weld. The biaxially oriented polypropylene film has good mechanical strength, but its weldability is very poor, so the biaxially oriented polypropylene single film is generally not used for bag making. The welding performance of plastic film is usually expressed by the weld strength, i.e. n/15mm. The higher the weld strength, the better the welding performance

when setting the initial value of the counter, it should be in the case of power failure. Among other functions of commodity protection, the barrier performance and shading performance are most often considered

barrier performance refers to the performance of plastic film to prevent oxygen, carbon dioxide, nitrogen and other gases as well as aroma, water vapor and other substances from penetrating. When the scope is not clear, it generally refers to the barrier to oxygen, carbon dioxide, nitrogen and other non-polar gases. For many commodities, especially food commodities, the barrier performance of plastic packaging film is an important factor for the long-term and effective storage of packaged commodities. The packaging of fresh fruits and vegetables requires that the film should have appropriate air permeability, properly inhibit breathing, and make the packaged items maintain a certain metabolism without necrosis, so as to prolong the fresh-keeping period

the most commonly used method to express the barrier property of plastic film is to measure the amount of a certain substance passing through the film per unit area in a certain time under a certain temperature and humidity. The barrier property of plastic film to aroma. Generally, after the fragrant 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 the dryer, opened regularly for inspection, and the time when the fragrance can be perceived initially is the fragrance retention time). The longer the fragrance retention time is, the better the barrier property of the film to the penetration of the aroma is. Shading is also very important for the packaging of some commodities. Light, especially ultraviolet light, is an important cause of discoloration, fading and oxidative deterioration of some substances, so it should be paid attention to. Shading is measured by the transmittance of a given wavelength. If the transmittance is high, the shading is poor. The effect of plastic film on commodity display 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 clarity of packaged goods, and have a great impact on the display effect of goods. Both transmittance and haze are expressed in percentage. The greater the transmittance, the better the transparency of the film; The greater the haze, the greater the turbidity of the object observed through the film, that is, the worse the definition

gloss refers to the reflective ability of the plastic film when exposed to light, which is expressed as the percentage of the reflected brightness of the sample relative to the standard surface in the positive reflection direction. The higher the gloss value, the better the surface brightness of the film

as we all know, the printing patterns on the packaging can not be ignored for the publicity and display of commodities. Generally speaking, the printing performance of plastic film refers to whether the film needs surface pretreatment before printing. The antistatic property of plastic film directly affects the dust absorption of plastic film bags. Good antistatic property, not easy to dust; Poor antistatic property, easy to dust. Dust absorption will reduce the transparency, gloss and the clarity of printed patterns of plastic film bags. Therefore, the good antistatic property of plastic film is very important to maintain the good display effect of packaging bags for a long time. When a good display effect is expected, a film with good antistatic performance should be selected

the antistatic property of plastic film is expressed by surface resistivity or charged half-life. The lower the surface resistivity and the shorter the charge half-life, the better the antistatic property of the films

with the continuous improvement of production level, the application of automatic production line is becoming more and more extensive. When adopting mechanized and high-speed packaging, we must attach great importance to the adaptability of packaging film to packaging machinery. The performance indexes that affect the adaptability of plastic packaging film to packaging machinery are mainly the smoothness and weldability of the film

good smoothness is conducive to the smooth movement of the film in the packaging machine during packaging, so as to avoid damage due to excessive resistance during its movement. The smoothness of the film can be described by its friction coefficient. The smaller the friction coefficient, the better the smoothness performance. The thermal welding performance mentioned here not only refers to whether the plastic packaging film can be heat sealed, or whether it can reach a sufficiently high welding strength after heat sealing, but also often requires that the plastic packaging film is allowed to have a large temperature range and a large pressure range during heat sealing. Although some films can be heat sealed and have high welding strength, the heat sealing conditions are harsh and can not be well matched with the packaging machinery, which should be paid full attention to

the special requirements for packaging film according to the needs of specific commodities are mostly in the category of special requirements in essence. Due to their particularity, they are introduced separately. Such requirements include the compatibility between the plastic film and its contents, and the adaptability, dielectric property, hygiene and binding of the plastic film to the use environment

it is often necessary to consider whether the plastic packaging film will lose strength due to corrosion, dissolution or swelling by the packaged substances, and whether the plastic film will react with the packaged substances, which will degrade the performance of the goods or damage the packaging bags

it is often necessary to consider the high and low temperature resistance of the film, such as cold storage, especially the plastic packaging film used for frozen food, which needs to have good low temperature resistance; The plastic packaging film for cooking food needs to have good high temperature resistance

goods such as integration are easy to be broken down due to static electricity in the packaging belt, so the plastic film selected for packaging of such goods must have good antistatic performance, and its surface resistivity is generally controlled at about 108 ohms or lower

when packaging food or pharmaceutical products, the selected plastic packaging film must have good hygienic performance, and meet the requirements of relevant national hygienic standards for cycling that save more than 30% effort compared with the previous generation model, so as to ensure that the plastic film will not cause pollution to the packaged goods

when heat shrinkable packaging and wrapping packaging are used, the binding force of packaging is very important. Therefore, when selecting this kind of film, attention should be paid to the shrinkage rate, shrinkage stress and elastic recovery rate, and the selection should be made according to the different conditions of the commodity. The binding force is insufficient, and the packaging (especially the collective packaging) is not tight; However, if the binding force is too large, fragile and perishable objects may be damaged

on the premise of meeting the above performance requirements, when selecting plastic packaging film. Try to select varieties with relatively low prices to save packaging costs, reduce commodity costs and improve competitiveness. Blindly pursuing the "high-grade" of packaging will obviously increase the production cost of commodities, but it is meaningless to improve the packaging effect of commodities, so it must be avoided

the wide application of plastic packaging materials has made a positive contribution to the industrial and agricultural production and the improvement of people's living standards. However, it has also brought no small negative impact on the living environment of human beings and caused a great burden on the environment. Therefore, when selecting plastic packaging film, in addition to the above principles, great attention should also be paid to the adaptability of plastic film to environmental protection

when selecting plastic film, it is necessary to master the characteristics of goods and their basic requirements for packaging, and have a clear understanding of the basic performance and main characteristics of plastic packaging film, especially the common plastic packaging film. Only in this way can we choose the ideal plastic packaging film

reprinted from: China steel drum packaging

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