Present packaging materials

First, ethylene - polyvinyl acetal film ethylene - vinyl acetate (EVA) copolymers are olefins. They are derived from a basic polypropylene structure and have approximately the same chemical resistance properties as low density polypropylene.
Compared with LDPE, EVA resin film has better collision resistance and lower heat sealing temperature. Collision resistance increases with increasing molecular weight and increasing vinyl acetate content. Increasing the vinyl acetate content and decreasing the molecular weight can reduce the heat sealing temperature.
When the vinyl acetate content is increased, the crystallinity of the EVA resin is smaller, but it is more elastic and more viscous. This is related to a high coefficient of friction. Due to stickiness problems, EVA resins need to add more slip and anti-blocking additives when low friction coefficient performance is required. Adding these additives in large amounts will impair optical performance, so unless the low friction requirement exceeds the optical For transparency requirements, such additives should not be used.
Resins with higher vinyl acetate content have lower crystallinity, which increases the permeability of water vapor, grease, and gas.
When vinyl acetate is added, many changes occur in the polyethylene. For example, when vinyl acetate content increases, its resilience, low-temperature heat-sealability, flex-resistance and stress crack resistance, permeability and transparency also increase.
EVA copolymers with higher vinyl acetate content are expected to replace PVC and LDPE as flexible packaging materials, including tray stretch packaging; packaging of fresh meat; shrink packaging of monomolecular films; composite packaging materials such as cured meat; Lining of bagged containers and cartons.
The EVA resin used for packaging can be processed on conventional polypropylene processing equipment. They have excellent low-temperature sealing properties, these resins can be re-formed into a thin film, extrusion coating or coextrusion compound. Several grades have been added with additives to increase their adaptability to packaging machinery.
2. Fluoro-Bendronated Hydrocarbon Films The chimney-fluoroplastic film is a copolymer of chlorotrifluoroethylene (CTFE). These nonflammable, highly insulating, transparent films have some unique practicalities. There are currently two types of such films, CTFE and CTFE (ethylene chlorotrifluoroethylene copolymers).
The CTFE film is still soft below -320°F, and its melting point is between 360°F and 400°F, depending on its grade and degree of crystallization. CTFE is chemically inert and can withstand the attack of aggressive chemicals that metals, ceramics, and other plastics cannot withstand. In addition, the CTFE film has a lower water vapor permeability than any other plastic film, and its hygroscopicity is virtually zero. They can be combined with a variety of base materials, such as polyethylene, PVC, polyester, nylon, iron, aluminum, and they can also be sprayed with vacuum plating. CTFE films and their composites are primarily used to package tablets and capsules that require high moisture protection.
Because they can be compounded with a variety of materials, the packaging is very versatile, and its vinyl compound can be thermoplasticized into a solid, convex blister to protect products that are more easily broken. In both cases, the CTFE film protects the stability of the product longer than any other transparent, flexible plastic. Other uses of CTFE include pressure sensitive tapes, liners for container lids of chemical resistant drugs. The National Association of Safety Managers has determined the liquid oxygen adaptability of CTFE film under impact. This allows them to be used as "clean" bags for ultra-clean aerospace objects.
CTFE film is an important material for transparent moisture-proof composite films.
The current production of these films, 3/4 mils in thickness, is a food packaging material approved by the Food Administration. Each lb. of CTFE can produce a thick, 13,000 square inch film at a cost of $12.30 to $15.25 per pound, depending on the type. The cost of a 1 mil thick film is roughly $1.17 per 1000 square inches.
In general, CTFE films are printable and can be composite and extrusion coated. They can be heat-pulsed, electrically RF or ultrasonically sealed without support. The composite film can be heat-sealed with a conventional heat sealer.
Ethylene-chlorotrifluoroethylene (ECTFE) film is a kind of thin film with high abrasion resistance, high tensile strength and low specific gravity in any existing fluoropolymer film. It is a one to one alternating copolymer of ethylene and chlorotrifluoroethylene. One to three mil ECTFE film and 125 mil sheet are available on the market today.
This material has outstanding resistance to the penetration of moisture, gases and liquids. It has excellent chemical resistance properties and is practically not attacked by aggressive chemicals commonly found in the industry. ECTFE is resistant to strong inorganic acids, oxidizing acids, caustic soda, metallic corrosives, liquid oxygen, especially organic solvents, except for various thermal amines. Like other fluoropolymers, it is attacked by metallic sodium and potassium. The ECTFE film has a relatively high insulation and a low, substantially uniform, dielectric loss angle at various temperatures and frequencies. It also has high volume and surface resistance, as well as excellent anti-imprinting properties. This film has excellent mechanical properties, including abrasion resistance, tensile strength and resistance to splitting. Its resistance to softness outperforms most fluoropolymer films. These properties can be maintained over a wide range of temperatures. It also has outstanding resistance to weathering and anti-high-energy radiation.
When the thickness of ECTFE is 1/16 inch, the oxygen index is 60; when the thickness is as thin as 0.5 mil, the oxygen index is 48. When it is put into the fire, it will charize without melting and dripping.
The film can be heat-sealed using conventional resistance, pulse, and ultrasonic sealing techniques. It can be compounded with a variety of plastic and metal base materials using adhesives with a bond strength of between 600 and 12,000 g/in. Thicker films can be thermoformed using pressure and vacuum techniques, while thermoplastically formed parts can be made of epoxy compound cans, and ECTFE films can be metallized. It can be used for fire protection.
III. Ionic Bonds Thin film ion bonds, ie "ionically crosslinked" thermoplastic polymers, are derived from ethylene/methacrylic acid copolymers. Therefore, the ionic bond also clearly has characteristics common to many olefin polymer products, and the molecular weight and crosslinkage are directly related to the physical and processing characteristics of the ionic bond. The properties of ionically crosslinked structures include: high speed processing properties, high thermal bonding strength, formability, toughness, excellent optical properties, low temperature heat sealing properties, oil solvent resistance, and co-extrusion of aluminum foil and nylon .
There are 26 grade ionomer films and coating materials that can be used to package a wide variety of foods and other products. This includes composite structures that are fused by ionic bonds, such as vacuum bags for sugar-processed meat and ion-bonded/nylon co-extruded film bags for fresh meat.
An additional use of ionic bonds is to combine it with paper and foil into a multi-layer film for packaging foods and making high-strength laminated bags.
Ionic bonds have been used for flexible packaging due to their strong bonding force with the foil, good resistance to penetration, heat sealability, and the ability to seal at low temperatures through form-fill-seal equipment.
Since the inner chain of the ionic bond is not the same as the common polyethylene covalent bond, it can be thermally reversed, so that it can also be thermally melt-replicated using conventional techniques. Hot-melt ionic bond strength is particularly high, can withstand stretching during forming operations, can be stretched into very thin coatings, and has excellent "thermal adhesion", which is the so-called perfection in hot melt conditions. Heat sealability.
Nylon film nylon is an interesting and versatile plastic packaging material. Its ideal properties, such as excellent oxygen barrier properties, excellent anti-adulterative properties, good high and low temperature properties, thermoforming properties, and retention of mechanical strength in both orientation and orientation, make it A strong competitor on the packaging. However, its main drawback - poor moisture resistance - makes it necessary to compound with other materials. Therefore, in the packaging, the nylon technology is actually a composite technology of nylon and other materials.
Individual or single-layer nylon films are mainly produced by cooling roll casting, and some can also be produced by blow molding. It is then combined with the polyolefin by bonding or extrusion compounding. Most nylon films used today are composites with PVDC films to further enhance their moisture and oxygen resistance. In turn, nylon can also be extruded on other film base materials. Coextruded films of nylon and other resins are produced by casting and blow molding.
No. 6 nylon film can be biaxially oriented by blow and transverse stretching. This material has outstanding flex resistance and also exhibits better tensile and impact strength. Nylon can also be plated with metal, this film has better insulation.
Chemically, all nylons are polyamides, that is, polymers of long chain amines that combine organic amines with organic hydroxy acids.
A type of nylon is composed of monomer molecules, each of which contains a combination of an acid and an amine. For example, E-aminoacetic acid constitutes No. 6 nylon.
The effect of humidity on the properties of nylon 6: Commercially, nylon 6 is made from ethylene-propionamide by the action of transamides. Other commercial nylons made from singulation are nylon 12, nylon 11 and nylon 8.
The other type is mainly nylon polymer chains, which are formed by combining molecules containing two groups of acids and other molecules containing two groups of amines. The material thus constructed is called nylon 66, which is composed of oxalic acid and hexamethylenediamine.
Other nylons that fall into this category are nylon 610 and nylon 612.
Nylon 6/11 and Nylon 6/12 variants of the first nylon-based nylon copolymer were formed by random polymerization of two different amino acids. Copolymer variants of the second type of nylon include nylon 66/610 and 66/612. The other type of copolymer is nylon 6/66, which is a combination of nylon 6 and nylon 66. Most nylons are miscible with each other and therefore synthesize almost endless amounts of copolymers.
The graft copolymers constitute another class of nylon copolymers, which block grafts of other polymers such as ethylene copolymers onto the spine of the nylon polymer. These materials have better softness and impact resistance. It also exhibits permeability between polymerized olefins and pure nylon.
Because nylon is an integral polymer, they undergo amine-amine alternation and hydrolytic cleavage during extrusion and other hot melt processes. Therefore, the resin must be kept at a low temperature prior to extrusion, otherwise the moisture will chemically change in combination with the amine, destroying the final combination of amine and acid, and lowering the molecular weight. Under normal conditions, moderately sized nylon strands do not absorb excessive moisture in 2 to 3 hours and cause problems.
The damp nylon can be oven-dried under the specified conditions. Nylon scraps of composite structures, if not protected, are in contact with air and must not be used until they have dried.
All nylon will absorb moisture and absorb water when in contact with air. At 70°F and an air humidity of 50%, nylon 6, in particular 66, absorbs approximately 2.5% by weight of water. Water acts as a plasticizer on nylon, producing a softer, more extensible, and impact-resistant film. It also greatly increases the permeability of oxygen to nylon.
Appropriate design and processing of the film structure allow the nylon to exhibit the desired dry or wet and wet properties. For example, a layer of nylon co-extruded between two layers of olefin polymer can withstand moisture for several weeks in a row. On the other hand, a layer of nylon 1 mil thick outside the packaging container can reach 50% relative humidity within a few minutes.
Most nylons are crystalline thermoplastics. The time for the internal crystal formation of nylon is limited and depends on the processing time, so the processing can influence the size, shape and percentage of crystals in the finished product. This effect is particularly noticeable for nylon 6. A skilled technician can significantly change the crystalline morphology of the nylon layer. For example, a blown co-extruded film of nylon 6 tends to be more opaque than a film of the same structure produced by a chill roll cast film line. As the blown film stays at a higher temperature for a longer time, the crystal grows longer and the light is diffracted, resulting in opaque results.
The majority of the nylon used for film today is nylon 6, because of its low price, large output, ease of processing, and wide application. The amount of nylon used is also quite a few, almost entirely thin