Selection and application of the hottest barrier f

2022-08-08
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The selection and application of barrier film in the packaging industry

preface

the packaging barrier material made of plastic film is used to protect the package from damage or degradation caused by penetrating gases such as oxygen or water vapor. Barrier resins also protect the taste benefits of food or beverages in the packaging. At the same time, compared with the old packaging materials such as glass and metal, plastics have some advantages, such as softness, light weight and low cost

barrier resins used in packaging materials include polyvinylidene chloride (PVDC), ethylene vinyl alcohol (EVOH), polyethylene terephthalate (PET), polytrifluoroethylene (PCTFE), nylon and nitrile copolymer

although there are some packaging resins with single-layer structure, the vast majority of packaging resins are packaged with multi-layer structure. Typically, the outer resin of multi-layer packaging materials is generally made of polyester and polystyrene materials, with high strength and good transparency; The interlayer resin is also a barrier resin; The plastic with the inner layer contacting the packaging materials is generally low-density polyethylene. Sometimes additional layers are used to improve the strength or barrier performance of the packaging materials, and sometimes adhesives are used to improve the bonding strength of multi-layer materials. The commonly used adhesive is a copolymer of ethylene vinyl acetate resin (EVA) and ethylene acrylic acid

polymer abbreviation oxygen ml/m2 24 hours- ATM 250C carbon dioxide ml/m2 24 hours- ATM 250C water vapor g/m2 24 hours- ATM 370C welding performance polyethylene (low density)

(high density) PE ldpe

hdpe

good polyester PETP poor polyamide (nylon) Pa poor polyvinyl chloride PVC -- 100 poor polyvinylidene chloride PVDC poor vinyl alcohol copolymer evoh0.4 - 0.6

(%rh)

25 - 31

0.5 - 240 - 80 poor polypropylene PP - 120008 -14 poor polystyrene PS - 26000 100 poor

table 1: the barrier properties of plastics under standard conditions are used to protect meat or meat products. Specimen thickness: 0.025 mm

(source: Norwegian Food Research Institute) the barrier resin packaging material has a variety of complex multi-layer structures. At the same time, it is required to have a certain strength and gas permeability. It is required that some gases can pass through, while other gases cannot pass through. One of the directions being studied is to improve the performance of polyethylene terephthalate (PET), a packaging material. As far as equipment is concerned, it can prolong the storage life of beer

polyvinylidene chloride (PVDC)

polyvinylidene chloride (PVDC) is one of the earliest packaging materials. It has been used as a food packaging material in supermarkets for many years. It is also sold in supermarkets as a consumption film for refrigerated food. Polyvinylidene chloride (PVDC) is characterized by low penetrability to oxygen, odor and moisture, and good transparency, strength and sealing performance

polyvinylidene chloride (PVDC) has strong barrier properties, and can be coextruded with other polyolefins to produce multilayer packaging films. This multilayer film can be used alone, or laminated with other materials such as metal foil, paper, polyolefin, nylon, oriented tensile film, polychloroethylene or high impact polystyrene to form a variety of hard or elastic bottoms

figure 1: the sausage packaging material adopts biaxially stretched polyvinylidene chloride, which has good barrier performance against oxygen and water

(source: macro Engineering Technology Co., Ltd.) in addition to the barrier characteristics, multilayer PVDC films have certain toughness, strength, chemical resistance, softness and certain economic benefits. It is mainly used in food packaging, transparent plastic cover of medicine, hat lining and fabric lining to protect clothes

ethylene vinyl alcohol (EVOH)

ethylene vinyl alcohol is one of the most competitive competitors of polyvinylidene chloride as a barrier material for food packaging. It has significant oxygen resistance and water resistance, as well as high strength, softness and transparency. Ethylene vinyl alcohol is often coextruded with polyester, polyethylene or polypropylene as the sandwich layer of sandwich structure. Although mainly used as a barrier material for food packaging, vinyl alcohol can also be used as a barrier material for automotive fuel tanks and ducts

a recent research on vinyl alcohol is the perfect combination of flexibility and elasticity, which enables vinyl alcohol to be used on softer barrier packaging and shrink packaging film; Another research trend is to improve the oxygen barrier performance of ethylene vinyl alcohol, and add oxygen Purifier - chemical active additives to food packaging materials to absorb oxygen. For example, for food sensitive to oxygen, closed thermoformed polypropylene ethylene Filip 2 manufactured by Swedish packaging company can be used. It also has honeycomb technology vinyl alcohol propylene barrier cup. After the cup is disinfected, use an oxygen purifier to absorb oxygen immediately, because disinfection temporarily disturbs the barrier of vinyl alcohol

figure 2: foam polypropylene and ethylene vinyl alcohol are co extruded to produce light food trays

(source: CO extrusion plastic technology company)

polyethylene terephthalate (PET)

this is a problem that sanning has been thinking about and exploring. Polyethylene terephthalate is widely used as barrier packaging material to keep carbon dioxide in carbonated drinks, while maintaining the fresh smell of spicy condiments, fruit juice, jam and flavoring agents. Resin producers and packaging companies are looking for some new uses of polyethylene terephthalate as barrier material. The most active one is to use polyethylene terephthalate as beer bottle. Compared with polyethylene terephthalate soft drink bottles, pet as a beer bottle requires higher barrier performance. At the same time, they should not only keep carbon dioxide from leaking out, but also ensure that oxygen cannot come in. In addition, the bottle must adapt to high temperature disinfection, and finding a packaging material that meets such requirements is a considerable challenge. Another obstacle faced by developers is the requirement that PET containers can be easily recycled. The problem is the multi-layer packaging materials generated by various materials

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