High barrier is not only an ability, but also an adjective. The concepts and standards of high-barrier packaging in different periods are also different, and the concepts and standards of high-barrier packaging for different purposes are also different, even in terms of price and processing performance. There are also differences in the high barrier of the industry, and what is more, the industry has not unified the understanding of the comprehensive barrier performance indicators of high barrier. Some materials have excellent performance in blocking certain substances, some are comprehensive, but when specific to a certain index, there are many materials that are better than it, and some have good barrier performance in dry environments, but When encountering a humid environment, the barrier ability will drop sharply. Some have excellent barrier properties and are basically unaffected by the environment, but they may be easily broken and have inherent processing performance limitations. Some have good barrier properties, but unfortunately they are not. Translucent, some have good barrier properties, but have little effect on UV blocking.
High-barrier packaging is a plastic packaging bag material with high barrier properties. Currently, the most widely used barrier materials are PVDC, EVOH, PEN, nitrile-based resin, polyamide, etc. At present, high barrier properties have become one of the important development directions of plastic packaging bag materials, especially in food and pharmaceutical packaging, more and more emphasis is placed on high barrier properties.
PVDC high barrier packaging material
PVDC (polyvinylidene chloride) is characterized by low permeability, barrier properties and chemical resistance. At present, it has been widely used in food, cigarette, beverage preservation and taste separation, as well as moisture-proof packaging in chemical, pharmaceutical, electronic and military industries.
The single-layer PVDC film is produced by biaxial stretching blow molding, which has shrinkage, barrier properties and water resistance, and does not decompose under the condition of microwave heating. It is widely used in household plastic wrap; PVDC and polyethylene (PE), polypropylene ( Multi-layer extrusion of synthetic resins such as PP) and polystyrene (HIPS) is used for the packaging of vacuum dairy products and jams. ) composite sheet is suitable for the packaging of easily moisture-absorbing and volatile medicines. At present, many domestic research institutes and manufacturers focus on the research of PVDC and other resin composite lamination film technology and high temperature resistance technology of composite film.
Since PVDC is currently the only high-barrier transparent material certified by the US FDA to be in contact with food, coating PVDC latex on many plastic packaging materials has also become one of the commonly used methods in the international food packaging industry. PVDC is used in a variety of substrates such as PE, PP, PVC, polyamide (PA), polyethylene terephthalate (PET), etc. Taking biaxially oriented polypropylene film as an example, the oxygen permeability after coating It can be reduced by 1000 times, and the water permeability is reduced by 3 times; the coating can be single-layer or multi-layer, and generally a single-layer coating of 2.5μm can have a good barrier effect.
EVOH High Barrier Packaging Materials
The barrier properties of EVOH depend on the ethylene content. Generally speaking, when the ethylene content increases, the gas barrier properties decrease, but it is difficult to process. The remarkable feature of EVOH is that it has excellent gas barrier properties and excellent processability. In addition, it has excellent transparency, gloss, mechanical strength, stretchability, abrasion resistance, cold resistance and surface strength.
In the field of packaging, EVOH is made into a composite film intermediate barrier, which is used in all rigid and flexible packaging; in the food industry, it is used in aseptic packaging, hot cans and retort bags, packaging dairy products, meat, juice cans and Condiments; in non-food, it is used to package solvents, chemicals, air-conditioning structural parts, gasoline barrel linings, electronic components, etc. In terms of food packaging, EVOH’s plastic containers can completely replace glass and metal containers. Many seafood companies use PE/EVOH/PA/RVOH/PE five-layer co-extrusion film vacuum packaging for seafood. The gas barrier properties of the new stretched EVOH film are three times that of existing high-performance non-stretched EVOH films. In addition, EVOH can also be used as a barrier material to coat other synthetic resin packaging materials to enhance the barrier properties.
PEN High Barrier Packaging Materials
The structure of PEN (polyethylene naphthalate) is similar to that of PET, except that the benzene ring is replaced by a naphthalene ring, but it is superior to PET in almost every aspect: its barrier property is about 5 times that of PET, and its heat resistance, Better chemical resistance.
With the breakthrough of its raw material 2,6-naphthalenedicarboxylic acid synthesis technology, famous chemical companies such as ICI Company, Shell Company, Amoco Company and Eastman Company have carried out production and accelerated application research. At present, it has been used in food, beverage, medicine, cosmetics, etc., such as small-sized carbonated beverage bottles, juice, mineral water, milk, beer bottles, baby food (retort and sterilized) packaging, requiring high barrier, radiation resistance and chemical resistance Pharmaceutical pharmaceutical packaging requires industrial packaging with high strength, impact resistance, chemical resistance, and high barrier. In beer and beverage packaging, it has made up for the defects of PET and glass and has become a hot spot in recent years.
Some countries in Western Europe have begun to use PEN beer bottles in the market, which have the same fresh-keeping effect as glass bottles, and are impact-resistant and easy to recycle. At present, the limitation of its development is the immaturity of raw material synthesis technology.