Nylon barrier properties

Nylon. Nylon is the designation for a family of thermoplastic polyamide materials which in film form are moderate-oxygen barriers. The gas-barrier properties are equal to odor and flavor barrier properties important in food appHcations. Nylon films are usually tough and thermoform able, but are only fain moisture barriers (see Polyamides). 

Nylon films are used in lamination or coated form to ensure heat sealabiHty and enhance barrier properties. The largest uses are as thermoforming webs for twin-web processed meat and cheese packagiag under vacuum or in an inert atmosphere. Other uses include bags for red meat, boil-ia-bags, bag-in-box for wine, and as the outer protective layer for aluminum foil in cookie and vacuum coffee packages. 

This is a highly polar polymer and crystalline due to the presence of amide linkages. To achieve effective intercalation and exfoliation, the nanoclay has to be modified with some functional polar group. Most commonly, amino acid treatment is done for the nanoclays. Nanocomposites have been prepared using in situ polymerization [85] and melt-intercalation methods [113-117]. Crystallization behavior [118-122], mechanical [123,124], thermal, and barrier properties, and kinetic study [125,126] have been carried out. Nylon-based nanocomposites are now being produced commercially. 

PP is probably the most thoroughly investigated system in the nanocomposite field next to nylon [127-132]. In most of the cases isotactic/syndiotactic-PP-based nanocomposites have been prepared with various clays using maleic anhydride as the compatibilizer. Sometimes maleic anhydride-grafted PP has also been used [127]. Nanocomposites have shown dramatic improvement over the pristine polymer in mechanical, rheological, thermal, and barrier properties [132-138]. Crystallization [139,140], thermodynamic behavior, and kinetic study [141] have also been done. 

Most nanocomposite researchers obdurately believe that the preparation of a completely exfoliated structure is the ultimate target for better overall properties. However, these significant improvements are not observed in every nanocomposite system, including systems where the silicate layers are near to exfoliated [29]. While, from the barrier property standpoint, the development of exfoliated nanocomposites is always preferred, Nylon 6-based nanocomposite systems are completely different from other nanocomposite systems, as discussed [3,8]. 

Polymer-clay nanocomposites (PCN) are a class of hybrid materials composed of organic polymer matrices and organophilic clay fillers, introduced in late 1980s by the researchers of Toyota (Kawasumi, 2004). They observed an increase in mechanical and thermal properties of nylons with the addition of a small amount of nano-sized clays. This new and emerging class of pol miers has found several applications in the food and non-food sectors, such as in constmction, automobiles, aerospace, military, electronics, food packaging and coatings, because of its superior mechanical strength, heat and flame resistance and improved barrier properties (Ray et al., 2006). 

Perhaps the most exciting developments are yet to feature in fruit juice packaging. PET can be laminated with other plastics, such as nylon and ethylene vinyl alcohol (EVOH), to give extremely good barrier properties, and polyethylene naphthalate (PEN) may enable production of a plastic bottle that can be pasteurised at high temperatures. 

EVOH have superior gas barrier properties.80 89 They are often used as the internal layer in multilayer food packaging films, blow molded rigid containers, gasoline tanks for automobiles for a variety of purposes, etc. EVOH can be fabricated by the usual melt processing methods. The barrier properties of films decrease in the presence of moisture, so multilayer with protective polypropylene (especially biaxially oriented material), low-density polyethylene, nylons, or other moisture barrier films provides films or products that are useful even with liquids. The... 

Nylon, amorphous PET. PETG Excellent abrasion resistance, moisture sensitive Good barrier properties, not weatherable. clarity dependent on processing, orientation greatly increases physical properties... 

Examples of the use of nanostructured materials for packaging applications have been given in Chaudhry et al. (2008) and references therein. One of the first market entries into the food packaging arena was polymer composites containing clay nanoparticles (montmorillonite). The natural nanolayer structure of the clay particles impart improved barrier properties to the clay-polymer composite material. Some of the polymers which have been used in these composites for production of packaging bottles and films include polyamides, polyethylene vinyl acetate, epoxy resins, nylons, and polyethylene terephthalate. 

Nylons have relatively high melting points and can be steam autoclaved. Nylons can be injection moulded, blow moulded or made into sheet or film, and have a density range of 1.14—1.16. Multi-ply materials are employed for their oxygen barrier properties. 

SiOv can be applied to films such as PET, PP, nylon and PE. Ox usually lies between 1 and 2 (but excludes 2, i.e. Si02). Improvements in barrier properties are up to 120x for oxygen and 45xfor moisture, but severe creasing can cause a reduction. It has been shown that CPD coated SiOr. films will withstand autoclaving (moist heat) of 121°C, or perhaps above. 

The chapters devoted to structure-permeability properties of the more commercially advanced amorphous nylons (Chapter 5 (50)) and experimental polycarbonates (Chapter 7 (51)) illustrate many of the general principles needed for optimizing the barrier properties of essentially any polymer family. These chapters consider the importance of intersegmental packing and intrasegmental mobility on... 

Information on how orientation during melt crystallization affects the transport properties of polymers is sparse however, increases in the permeability have been attributed to the "shish kebab" morphology (ill). Most of the work involving barrier properties of oriented semicrystalline polymers has dealt with materials drawn at temperatures well below the melting point. The transport properties of cold-drawn polyethylene (34f 42-46), polypropylene (42,42), poly(ethylene terephthalate) (12,42-4 9), and nylon 66 (22) among others have been reported. 

Earlier work done in these laboratories has shown that polymer blends wherein the barrier polymers are dispersed as thin platelets parallel to the surface of the fabricated article, have significantly improved permeability barrier properties than the conventional "homogeneous", uniform, dispersions (1,2). The high barriers demonstrated were then achieved by blending 15-20% polyamides with a linear polyethylene, which achieved performance comparable to that obtained by adding as much as 50% nylon by conventional blending. While this performance has been satisfactory for a variety of applications, some of the more demanding uses require that the barrier polymer be used more efficiently. Described here are such blend compositions which show substantial resistance to permeation of hydrocarbon solvents and their mixtures. 

Cheese barrier properties strength laminations or coextrusion with PVDC on a base film of cellophane, polyester, nylon or PP... 

Orientation Orientation improves the inherent barrier and mechanical properties of unoriented nylon film. After biaxial orientation, nylon film exhibits a significant improvement in oxygen and aroma-barrier properties. ... 

Film Applications Packaging. Nylon s strength, durabiUty, and barrier characteristics make it a valuable component in multilayer film. Nylons are combined with polyolefins, foils, and other materials to enhance barrier properties. ... 

General Description DuPont Selar PA is an amorphous nylon (polyamide [PA]) resin that exhibits superior transparency good barrier properties to gases, water, solvents, and essential oils and high-temperature structural properties.P ]... 

Film Applications The amorphous nylons can be used in flexible or rigid packaging, and monolayer or multilayer films. Selar PA is suitable for a variety of packaging applications that require clarity, barrier properties, and processing flexibility. Because of the excellent barrier properties in refrigerated conditions. 

Selar PA and Selar PA blends have benefits in meat and cheese packages, replacing the nylon 6, PVDC, or EVOH barrier layer.Selar PA 2072 can be blended with EVOH (up to 40 wt% addition) without compromising the oxygen barrier properties of EVOH, especially at high humidity,... 

Barrier Properties In wet conditions (i.e., 95-100% RH), Selar PA 3426 is an excellent barrier to oxygen, carbon dioxide, and water vapor. It is equivalent to the EVOH oxygen barrier at the same wet conditions. In dry conditions (0-5% RH), Selar PA 3426 is a good barrier. At 0% RH, its oxygen and carbon dioxide barrier properties are the same as for nylon 6. At 95-100% RH, the oxygen and carbon dioxide barrier of Selar PA is substantially better than that of nylon 6. 

The barrier properties of nylon 6 blends fall between the performance of Selar PA 3426 and nylon 6. However, as the humidity increases, adding even small amounts of Selar PA 3426 improves the barrier more than would be predicted by a straight-line correlation. 

General Description Polyvinylidene chloride (PVDC) resin is a copolymer of vinylidene chloride (VDC) with vinyl chloride or other monomers and is used as a coating over DuPont Teijin Films Mylar films. Enhance Packaging Technologies Sclairfihn BL LLDPE Film, Dartek B-601 and B-602, nylon 66, and PVDC coated nylon. The PVDC coating provides the film with excellent oxygen-and moisture-barrier properties. 

Honeywell Oxy Shield nylon/EVOH oxygen-barrier (OB) film s combination of nylon 6 and EVOH delivers a strong mix of benefits the strength, toughness, and flex-crack resistance of nylon with the extremely low oxygen transmission rates, superior fla-vor/odor/aroma-barrier properties, with the outstanding solvent and oil resistance of both nylon and EVOH. The film is microwaveable and recyclable, and does not release harmful substances upon incineration.do 3]... 

OxyShield BOEB. Biaxially oriented, coextruded nylon 6/EVOH/nylon 6 clear film having excellent gas barrier properties through a broad range of relative humidity.h083]... 

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