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Application of CO mixed filling modification technology in packaging materials

according to the diffusion and penetration mechanism, the factors affecting the barrier property of plastic packaging materials are discussed from the perspective of material structure. The research and application status of CO mixed filling modification technology in improving the barrier and mechanical properties of plastic packaging materials were reviewed. The effects of component properties and processing methods on the microstructure, barrier properties and mechanical properties of materials during blending modification, as well as the common problems faced by filling modification, the development and application of surface modification technology are reviewed. The important role of dispersion and orientation of sheet nano filling materials on barrier properties is emphasized. In addition, the application prospect of plastic modification technology in packaging materials was prospected, and the key problems of CO mixing filling technology in the future were pointed out

in terms of food preservation, beverages and beer, gasoline tanks, moisture-proof packaging, etc., high barrier plastic packaging materials have strong technical advantages and ease of use, and their demand has been on the rise in recent years. At the same time, people also put forward higher requirements for the diversity, oxygen resistance, CO2 resistance, moisture resistance, shading, fragrance preservation, freshness preservation, sterilization, antistatic, anti fog, high and low temperature resistance, oxidation resistance, permeability and permeability of high barrier plastic packaging materials. For a long time, people have been trying to improve these performances through various means and methods. At present, there are multi-layer composite method, coating method, modified plastic method and so on. Multilayer composite and coating methods have certain limitations because of their complex process, high equipment investment, and can not significantly improve the mechanical properties of materials. The modified plastic method can not only fundamentally improve the barrier performance of plastic, but also improve its mechanical properties, and the products are also diverse. Therefore, using plastic modification technology to modify packaging materials has become the development direction and research hot topic of packaging materials. Among them, the research and application of blending and filling technology is the most active. In this paper, combined with domestic and foreign literature, the application of Plastic Co blending and filling modification technology in high barrier packaging materials in recent years is reviewed, and its development prospect is prospected

1 basic ways and methods to improve barrier property

gas permeability (barrier) and permeability are the most important properties of barrier materials. The main influencing factors are polymer structure, permeability gas characteristics and environment. Among them, the material structure is the most fundamental and direct factor affecting the barrier performance and mechanical properties

because the gases and liquids to be blocked in the actual process are mainly O2, CO2, H2O and low molecular organic substances, and the use temperature is not too high in most cases. Therefore, the basic way and method to improve the barrier property of materials is to use plastic modification technology to modify materials to reduce the solubility and diffusion of gases and liquids. Blending and filling modification are the two most commonly used methods

2 blending modification

it is difficult for a single material to meet the comprehensive performance and versatility of packaging materials. 4. Please wipe the sample with a dry cloth for the panel (control box, i.e. display). In most cases, packaging materials are prepared by blending materials with different structures and properties to improve their barrier properties and mechanical properties. There are two methods of blending: physical blending and copolymerization through threading and Bridge breaking. Among them, physical blending method is the most commonly used. The preparation techniques mainly include mechanical blending and reactive "in situ compatibilization" thermal mechanical melt blending. The research in this field has made great progress, and the modified materials prepared by this method are also common

2.1 simple blending

metallocene polyethylene (mLLDPE) has excellent properties such as low heat sealing temperature, high strength, strong puncture resistance, low extractable matter, and has good compatibility with LDPE or LLDPE. The blending of the two can significantly improve the physical and mechanical properties, heat sealing properties and printability of the film. It is a common inner material for multilayer composite packaging films of frozen food and health food

both polyarylate (U polymer) and pet have good thermoformability. After bi-directional stretch blow molding of their multilayer billets, heat-resistant bottles that can meet the requirements of 85 ℃ hot filling without heat treatment can be prepared

the ethylene/acrylate derivative copolymer series launched by Du Pont packaging and engineering polymer company has high melt strength and thermal stability. It has good compatibility with LDPE and is easy to bond with pet, PA and PP. It can not only be used for blowing and casting films, extrusion coatings, composite layers, film modifiers, etc., but also can be used as a cheap toughener to blend with PP, PA, pet, ABS and pet/abs. After blending 10% of these materials with PP, the notched impact strength at room temperature can be increased by 23 times

Japan's Dadong me company and Nagoya Industrial Research Institute successfully blended aliphatic polyester with special ingredients to develop a biodegradable garbage bag, which has the advantages of high membrane strength and strong water barrier, and is as thin as 25 μ M also has no water leakage. Crystalline polymer is the preferred ingredient for making high barrier materials. The reason is that crystalline polymers have high barrier property, high strength and good heat resistance. When blending with other materials, because the gas is difficult to dissolve in microcrystals, its diffusion path becomes tortuous and long, and the material can have high barrier property. MXD6, a condensation polymer of m-phenylenedimethylamine and adipic acid, is a high barrier nylon material that has been widely studied and applied in recent years. Its melting point is 20 ℃ higher than that of PA6, and its barrier to O2 is 10 times higher, and the barrier does not decrease with the increase of relative humidity. Although the barrier performance at low temperature is not as good as PVDC, it is better than PVDC at high temperature. MXD6 and pet belong to the same crystalline material, and their thermal behavior is relatively close, which is easy to be compounded into one. Therefore, they are often blended to produce high barrier and heat-resistant bottle packaging containers. Typical products include pet/mxd6/pet multi-layer beer bottles of karlsberg company in France

2.2 physical blending

because there are few resins that are truly compatible in thermodynamics, there are not many varieties of simple blending. Physical blending has attracted more and more attention. During blending, the barrier properties and mechanical properties of materials are related to free volume fraction, polarity, melting point (or glass transition temperature), crystallinity, molecular fine structure and other factors, and the system often needs compatibilization

polar polymers have strong barrier to gas, but generally weak barrier to water; Non polar ones are the opposite. In order to improve the comprehensive properties of materials, they are often blended together. HDPE is thermodynamically incompatible with PA or EVOH. Liu Chunlin and others used the graft of matrix resin as compatibilizer to prepare high barrier hdpe/pa alloy materials with xylene permeability of only 0.3% under certain technological conditions. The patent invented a pe/pa material with good barrier performance to organic solvents. This material is prepared by blending PE, PA and compatibilizer (pa-g-evoh). Liu Ping, chengminlian, Cai Liangzhen and others also studied hdpe/pa, hdpe/evoh, EVOH, LCP, MXD6 and PET Blends by using the principle of Compatibilization technology. After thermal mechanical blending and blow molding, they prepared packaging containers with different excellent barrier properties to O2, CO2, H2O, aliphatic hydrocarbons, aromatics and pesticides. SEM observation shows that HDPE or Pei is a continuous phase. Under biaxial tension, PA or EVOH is in sheet shape and arranged parallel to the wall orientation, which gives the material high barrier properties

the diffusion coefficient of the material is related to the free volume fraction. The greater the free volume fraction, the greater the diffusion coefficient. ABIS et al. Studied the binary blends of syndiotactic polystyrene (SPS) with LLDPE, HDPE and SEBS respectively. It is found that adding 10% SEBS to sps/lldpe and sps/hdpe can greatly improve the dispersion of LLDPE and HDPE in SPS. At the same time, it was also found that the crystallinity and distribution of the components themselves also affected the structural properties of the blends. High elastic amorphous components can increase the free volume fraction, enhance the rearrangement ability of chain segments, and make it easier to form seams instantaneously. Therefore, the addition of compatibilizer can not only reduce the crystallinity of LLDPE, HDPE and SPS, but also reduce the barrier performance in excess

polymers with amorphous structure have small free volume fraction, weak segment rearrangement ability and low gas permeability in the glassy state. Therefore, amorphous polymers with high glass transition temperature (TG) have strong barrier properties. The Tg of pen is 43 ℃ higher than that of pet, and its barrier to O2, CO2 and H2O is 4 times, 5 times and 3.5 times higher than that of pet respectively. The tensile strength is 35% higher than that of pet, and the bending modulus is 5% higher. It has excellent barrier properties of O2, CO2 and H2O, mechanical properties and thermal properties. By blending pen with pet, 30% - 40% pen can make the blow molding bottle obtain excellent heat resistance (> e.g. wedge clamp 90 ℃), gas barrier and UV blocking. Such blends have been used to make beer bottles and beverage bottles. For example, polyclearn-10 of Swiss sntis Kunststoffe company, pen/pet of Austrian CA Greiner packaging company, alloy bottles, beverage bottles of Coca Cola company, etc

the fine structure of polymer also affects the permeability. Among them, the substituents have the most significant effect on the permeability of gas. This is mainly related to the free volume fraction. Large side groups (such as tert butyl) are conducive to gas penetration; Polar groups (such as -oh, -cn, etc.) and atoms with high electronegativity (such as Cl, f) can increase intermolecular interaction, making the formation of instantaneous cracks the most difficult. M poly (aryl ether ketone) (Paek) is a kind of polymer formed by the connection of phenylene ring through ether bond and carbonyl group. Ohamed et al. Prepared a polymer by polymerization of fluorine-containing oligomer with carbamate and end group fluorination, respectively It was blended with polyvinylidene fluoride (PVDF) casting solution containing N, N-Dimethylacetamide. The results showed that the barrier of the blend to water was greatly enhanced

2.3 orientation and stratification

from the perspective of material microstructure, orientation and stratification have an important impact on the barrier properties of blends. The two are generally related to external factors such as processing conditions and methods. Many blend modified plastics have a single-phase continuous microphase separation structure. Continuity generally plays a leading role in the permeability of blends. When there is a highly barrier dispersed phase, the greater the orientation and stratification of the dispersed phase along the wall direction, the stronger the barrier of the material. After tensile orientation of crystalline materials, the permeability coefficient can be reduced by about 50%; The non crystalline stretching can also be reduced by 10% - 15%. Therefore, in the blending modification, tensile orientation and layered blending have attracted more and more attention, and have become one of the hot spots in the preparation of high barrier plastic packaging materials

the degree of stratification mainly depends on the nature and proportion of the selected resin and the melt flow rate (MFR) of the resin. The MFR of HDPE is similar to that of PA6. Wu Peixi must be