Application of the most popular barrier materials

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The application of different barrier materials in the packaging industry (Part I)

packaging, especially plastic packaging, can be seen everywhere in modern society. The rapid development of the packaging industry is due to its ability to protect and stabilize products for a long time, as well as to avoid damage, pollution and moisture. To achieve the best protection effect, high barrier materials are the inevitable choice

in a broad sense, barrier packaging has been used for many years. Barrier packaging is designed to protect products and contents from the infiltration of pollutants, flavors, colorants and odors, and sometimes is also used to prevent the leakage of contents

in other cases, multi-layer structure (lamination or coextrusion) is needed to improve strength and barrier performance. Even for seemingly simple products such as fast food, the packaging can be very complex. These multilayer structures often contain 7 or more different plastic layers, and each layer has different structural barrier or bonding effects

synthetic special barrier resin, namely polyvinylidene chloride (PVDC), came out in the 1950s. After the development in the 1960s, plastic barrier packaging has experienced great development since then. Soon, ethylene/vinyl alcohol (EVOH) was put into commercial application in the 1970s

barrier packaging industry has been changing since then. Because different applications have different requirements, ideal polymer barrier materials do not exist now and may never appear. For example, in some cases, such as PVC film with poor oxygen barrier properties, it is often used as meat packaging display in supermarkets, mainly because PVC film can keep meat red and attract customers during display time. However, if meat needs long-term transportation or storage, it must have good oxygen barrier performance to prevent meat deterioration

at present, barrier packaging plastics can indeed meet the needs. However, problems still exist, which restrict the application and development of barrier packaging plastics in many applications. These problems mainly include:

the cost is high, which is generally higher than simple single-layer plastic packaging, such as LDPE and LLDPE

when exposed to water, it is particularly easy to pollute and degrade. EVOH is the most suitable material to solve this problem, but hydroxyl not only gives excellent barrier properties, but also makes the material easy to hydrolyze. Therefore, EVOH can only be used as the inner layer of multilayer structure

handling and reuse problems. Most multi-layered packaging contains a variety of plastics (such as HDPE and PET), so it is not easy to mix and reuse

challenges from alternative materials. Traditional materials such as glass and new materials such as silica glass veneer can provide excellent barrier properties

according to its oxygen and water permeability and permeability, the barrier resin should have the following permeability characteristics:

1 Oxygen: resin with oxygen permeability (OTR) less than 2ml/mil thickness/100 square inches under atmospheric pressure for 24 consecutive hours. Most oxygen permeability measurements are carried out at a temperature of 73 ° C and a relative humidity determined according to specific conditions. Many traditional resins have an oxygen permeability of 5, while most new resins are equal to or lower than 1. For example, the oxygen permeability of standard metallized PET film does not exceed 0.3; Materials with oxygen permeability lower than 0.1 are classified as high barrier materials, including PVDC and EVOH. Other materials are classified as medium barrier materials

2. Water vapor (moisture): resin with moisture permeability (WVTR) less than 0.1. We define and classify the structure of moisture barrier polymers according to the classification of pharmaceutical blister packaging industry. In other words, films with moisture permeability higher than 0.1 are classified as ultra-low barrier films, films from 0.06 to 0.1 are classified as low barrier films, films from 0.03 to 0.06 are classified as medium barrier films, and films equal to or lower than 0.03 are classified as high barrier films

there are also 20% glass fibers for reinforcement. Various resin films with moisture permeability of 1 have been on the market for many years. Ptcfe is the latest and best moisture proof film at present, and its moisture permeability is lower than 0.3. It is considered to be the only high moisture proof film resin at present. The moisture permeability is generally measured at 100 ° C and 90% relative humidity

Introduction to various barrier materials

Polyoxymethylene (POM)

polyoxymethylene is a kind of multi-functional engineering resin with high technical content if the product has high added value. Its chemical structure, regular molecular structure and high crystallinity make it have excellent resistance to water, gasoline, solvents and other neutral chemicals

pom can be processed by injection molding and extrusion. Its specific uses include: air spray container, gasoline tank cover, chemical spray, soap dispenser, paint mixer, water pipe fittings, gears, creep resistant shell, wear-resistant surface, etc

its barrier test shows that a variety of thin new materials have been sought after by the market. When the film thickness exceeds 10 mils, the filler free ticon innovatively proposed a new processing technology. A Celcon polyformaldehyde and glass reinforced polyformaldehyde have roughly the same permeability. DuPont Delrin products have excellent permeability resistance and strength characteristics for a variety of substances, making them suitable for containers, especially air spray containers. Ticona Celcon POM can withstand high humidity and high temperature water for a long time. Therefore, this material is widely used in water pipe related applications

propylene resin (AMA)

this is a transparent rubber modified propylene material, which has excellent chemical resistance, gas resistance and high modulus or stiffness. It is mainly used in packaging. The permeability of AMA depends on the presence of additives and the chemical composition of propylene and comonomers. Hot forming, film extrusion, sheet extrusion, extrusion blow molding, tape casting, injection molding, injection blow molding, injection pull blow molding can be used

it is mainly used for packaging, including food packaging: processing meat, fish, cheese, condiments, sauces, juices and concentrated fruit juices; Drug packaging: pharmaceutical and skin patches; Personal care: cosmetics packaging, mouthwash, perfume, etc

The barex of

bp is a kind of propylene/methyl methacrylate copolymer grafted on propylene rubber. Barex 210 and 218 resins are high barrier and impact resistant modified copolymer resins. Compared with all kinds of plastics used in single-layer packaging, barex resin has the lowest oxygen permeability, and its performance often exceeds the multilayer structure containing EVOH and PVDC, and its cost is low. Encapsulated in beneficial gases such as nitrogen and carbon dioxide, it can prolong the storage life and prevent oxygen from entering the package

under various relative humidity, barex resin has extremely high barrier to oxygen. However, the increase of temperature will affect the barrier performance. In terms of water vapor barrier properties, barex resin is comparable to other plastic packaging materials except polyolefin. In applications where waterproof requirements are critical, the water vapor barrier performance of barex resin can be enhanced by polyolefin orientation or lamination

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