Product category and industrial application scope

2022-08-22
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Product category and industrial application scope of additives for plastic film

plastic additives are chemicals added to improve the processability and serviceability of resins. There are usually more than ten kinds of plastic additives used. With the increase of plastic varieties, the expansion of applications and the continuous progress of processing technology, the types and varieties of additives are also increasing. Plastic additives should be added in the processing and use of plastic films. Because the inherent properties of some resin or film products do not meet the requirements of the required processing technology, adding additives only needs to change their processability; However, some materials have better processing performance, but the product performance can not meet our requirements, so additives should be added to change the product performance. Of course, these two functions complement each other, sometimes to achieve these two purposes at the same time

here we first introduce the additives that can change the performance of plastic packaging film

General requirements for additives

compatibility

generally speaking, only when additives have good compatibility with resins, can additives exist in films for a long time, stably and uniformly, and play their functions effectively. If the compatibility is not good, it is prone to "migration". It is "sweating" in liquid additives and "frost spraying" in solid additives. However, sometimes when the requirements for the film are not too strict, the compatibility of the electro-hydraulic servo dynamic fatigue testing machine can still be allowed to be insufficient. Under this background, some have developed with the development of the electro-hydraulic servo technology, such as the compatibility between the filler and the resin is poor, but as long as the particle size of the filler is small, it can still basically meet the performance requirements of the film. Of course, if it is treated with coupling agent or surfactant, its function can be brought into full play. However, some additives that improve the surface properties of the film, such as opening agent and antistatic agent, require a little mobility to play a role on the surface of the film

durability

durability requires that additives exist in the film for a long time with little or no loss, and the loss of additives is mainly through three ways: volatilization, extraction and migration. This is mainly related to the molecular weight of the additives, the solubility in the medium and the solubility in the resin

adaptability to processing conditions

the processing conditions of some resins are harsh, such as high processing temperature. At this time, it should be considered whether the selected additives will decompose and whether the additives have corrosive effect on the processing equipment

restrictions of film uses on additives

films with different uses have certain requirements on the odor, toxicity, weather resistance, thermal performance, etc. of additives. For example, plastic bags for food are required to be non-toxic, so the additives used are different from those used in plastic bags for general packaging

synergism and phase antagonism in the coordination of additives

in the same resin system, some two additives will produce "synergy", that is, they play a much greater role than using a certain additive alone. However, if it is not properly matched, some additives may have "mutual resistance", which will weaken the function of each additive and even make some additives ineffective. This should be paid special attention to, for example, the combination of carbon black and amine or phenolic antioxidants will produce antagonism. Plasticizers and heat stabilizers commonly used in plastic packaging films, as the name suggests, are substances that increase the plasticity of materials, that is, adding them to the resin, on the one hand, increases the fluidity of the resin during molding and improves processing performance, on the other hand, it can increase the flexibility and elasticity of the film

heat stabilizer is an additive added for the purpose of improving the thermal stability of resin. It is mainly used for processing PVC and vinyl chloride copolymer

light stabilizer

polymer materials will age rapidly under the irradiation of sunlight, light and high-energy rays, showing yellowing, embrittlement, cracking, surface loss of gloss, greatly reduced mechanical and electrical properties, and even eventually lost their use value. In this complex destruction process, ultraviolet light is the main reason for the aging of polymer materials. It is mainly the result of the combined action of ultraviolet rays in sunlight and oxygen in the atmosphere on polymer macromolecules

in order to protect polymer material films from UV and oxygen damage and prolong their service life, light stabilizers are added to plastic materials to make them absorb UV energy in the resin and convert the absorbed energy in a harmless form. To inhibit or weaken the role of photodegradation and improve the light resistance of the material. Since most light stabilizers can absorb ultraviolet light, they are also called ultraviolet absorbers. To evaluate the quality of an ultraviolet absorber, we should consider the efficiency, processing, price, non-toxic, etc., and we cannot emphasize oneortwo effects alone. These conditions are summarized as follows:

n can effectively absorb ultraviolet light with a wavelength of 290 ~ 410nm, and the absorption bandwidth; It can effectively eliminate or weaken the destructive effect of ultraviolet rays on polymers, while it has no impact on other physical and chemical properties of polymers. 1. Application of battery acupuncture experimental machine: it has no impact on the safety function of batteries after acupuncture experiments

n itself has good stability, and the absorption capacity will not decline after long-term UV exposure

n good thermal stability, no failure and discoloration due to heating during processing and use; It does not affect the processability of the polymer

n has good compatibility with polymers, does not separate and migrate during processing and use, is not easy to be extracted by water and solvent, and is not easy to volatilize

n non toxic or low toxic

n it is chemically stable and does not react with other components in the material to damage the performance of the material

n has low absorption of visible light, no coloring and discoloration

n it is cheap, easy to manufacture and rich in sources

according to the action mechanism of light stabilizers, they can be divided into four categories: ① light shielding agents (pigments); ② Ultraviolet absorbent; ③ UV quenching agent; ④ Free radical trapping agent. These four action modes constitute four levels that gradually deepen in light stabilization. Each level can inhibit the destructive effect of ultraviolet rays on polymer bodies. In the specific design coordination, it is a level or the protection of each level, which should depend on the requirements of the film and the use environment. After adding light stabilizer, although the amount is very small, and the upper edge of the scale is horizontal, the effect of preventing aging is very significant. Generally, only 0.1% - 0.5% of the weight of polymer needs to be added

there are many commonly used light stabilizers, which mainly include: ① o-hydroxybenzophenones (such as UV-9, UV-531, etc.); ② Benzotriazoles (such as UV-P, UV-327, UV-326, etc.), ② salicylates (bad, TBS, etc.); ④ Triazines; ⑤ Substituted acrylonitrile ⑥ organic nickel complex; ⑦ Hindered amines. Among these absorbers, benzotriazole and triazine are the best

antioxidant

for most plastic varieties, they are sensitive to oxidative degradation in the process of manufacturing, processing, storage and application. Oxygen can penetrate into the plastic film and react with most polymers, resulting in degradation or cross-linking, thereby changing the properties of materials. A small amount of oxygen can dramatically change the strength, appearance and properties of these polymer materials. Under thermal processing and sunlight, the oxidation rate is faster. Therefore, the oxidation of polymers is usually divided into thermal oxidation and photooxidation. Finally, the result of this reaction is performance aging. If this kind of reaction is not prevented, it can quickly oxidize the polymer and lose its use value. Different plastics have different stability to oxygen, so some plastics do not need to add antioxidants. Some must be added with antioxidants. The role of antioxidants is to capture active free radicals and interrupt the chain reaction, in order to delay the oxidation process and speed of plastics. According to the action mechanism of antioxidant, it is effective for all plastics

the chemical structure of antioxidants can be divided into: 1 Phenols, including: monophenol, bisphenol, triphenol, polyphenol, hydroquinone, thiobisphenol; 2. Amines, including naphthylamine, diphenylamine, p-phenylenediamine, quinoline derivatives, as well as phosphite esters, thioesters and other kinds

among the above categories, phenols and amines are the main antioxidants, accounting for more than 90% of the total. Generally speaking, amine antioxidants have higher protective efficacy than phenols. However, amines change color to varying degrees under the action of light and oxygen, and are not suitable for light, bright and transparent films, so they are less used in plastic films

according to the antioxidant effect, antioxidants are divided into main antioxidants and auxiliary antioxidants. Aniline has good anti oxygen effect, but it is highly polluting, and is mainly used in rubber products; Phenols have poor antioxidant effect, but less pollution and better comprehensive effect. They are mostly used in plastic films. Usually, mercaptans or thioesters and phosphites are classified as auxiliary antioxidants and used together with main antioxidants to produce synergistic effects and prolong the effectiveness of antioxidants

at present, the production and research of antioxidants are developing towards the direction of high efficiency, low toxicity and low price. Therefore, phenolic antioxidants will gradually surpass amine antioxidants. The compatibility between antioxidant and polyolefin plastics can be improved by substituting alkyl for some phenyl. Increasing the molecular weight of antioxidant is also an important way to improve the durability of antioxidant. Most antioxidants are easy to migrate, making the polymer unprotected. If the molecular weight of antioxidants is large enough and the possibility of migration is reduced, the effective life of antioxidants can be improved

lubricant

polymers usually have high viscosity after melting. In the processing process, when the molten polymer passes through narrow slots, gates and other channels, the polymer melt must have friction with the surface of the processing machinery. Some friction is not very suitable for the processing of polymers. After all, it is the most important advantage that they are suitable for themselves. These friction reduce the fluidity of the melt, and serious friction will make the surface of the film rough, Lack of gloss or streaks. Therefore, it is necessary to add additives for the purpose of improving lubricity, reducing friction and reducing interfacial adhesion. This is the lubricant. In addition to improving the fluidity, lubricants can also act as melting accelerators, anti adhesion and anti-static agents, smooth agents and so on

lubricants can be divided into external lubricants and internal lubricants. The role of external lubricants is mainly to improve the friction between polymer melt and the hot metal surface of processing equipment. It has poor compatibility with polymers and is easy to migrate from the melt to the outside, so it can form a lubricating thin layer at the interface between plastic melt and metal. Internal lubricant has good compatibility with polymer. It plays a role in reducing the cohesion between polymer molecules in the polymer, so as to improve the internal friction heat generation and melt fluidity of plastic melt. The commonly used external lubricant is stearic acid and its salts; The internal lubricant is a low molecular weight polymer. Some lubricants have other functions. In fact, every lubricant has the function of realizing a certain requirement. Internal and external lubrication always work together, but it is more prominent in one aspect. The same lubricant will show different lubrication effects in different polymers or under different processing conditions. For example, under high temperature and high pressure, the inner lubricant will be extruded out and become the outer lubricant

in the production of plastic film, we will also encounter some adhesion phenomena, such as in plastic film

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