Nylons packaging applications

Nylon film has been used increasingly for packaging applications for foodstuffs and pharmaceutical products. The value of nylon in this application is due to low odour transmission and to some extent in the ability to boil-in-the-bag. Film of high brilliance and clarity, particularly from nylon 11, is available for point-of-sale displays. 

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. 

For most packaging applications, compression cutting or shear cutting are used. LDPE is most often compression cut because its low modulus leads to necking in a shear die, and therefore a ragged edge is formed. For HDPE, PP, PMMA, PS, nylons, and PET, shear cutting can be used very effectively. However, the same die will not work equally well for each material because of the differences in modulus. 

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. 

Ideal for lamination to other substrates such as Dartek nylon film or Mylar polyester film for vacuum packaging applications. In converter combinations, SL is particularly suited for the vacuum packaging of processed meats. " ... 

Many polymers, including polyethylene, polypropylene, and nylons, do not dissolve in suitable casting solvents. In the laboratory, membranes can be made from such polymers by melt pressing, in which the polymer is sandwiched at high pressure between two heated plates. A pressure of 8-15 MPa (1000-2000 psi) is applied for 0.5-5 min, at a plate temperature just above the melting point of the polymer. Melt forming is commonly used to make dense films for packaging applications, either by extmsion as a sheet from a die or as blown film. 

Large volumes of polymer films are commercially vacuum metallized with aluminum every year and the metallization of roll substrates such as polyester, nylon and oriented polypropylene films for packaging applications are wide spread. In addition the metallization of paper is principally a decorative application where holographic or iridescent patterns are intensified by the reflective metal layer. The barrier properties of the aluminum layer are controlled by the base sheet onto which the aluminum is applied but also by the deposition process. In general the films are metallized to add a significant light barrier and to enhance the moisture and perhaps oxygen gas barrier properties of the film. Metal adhesion is also a primary concern. 

Nylon barrier layers are used in packaging films and blow molded bottles. In these applications, their excellent resistance to oxygen permeation are valued when packaging greasy foods, such as potato crisps (chips), that rapidly turn stale when exposed to oxygen. 

Polyamides, commonly known as nylons, may safely be used to produce articles intended for application in processing, handling, and packaging of food, including for products intended to be cooked directly in their packages. Nylon resins are manufactured by condensation of hexyamethylenediamine and adipic acid (nylon 66) or sebacic acid (nylon 610), by the polymerization process, e.g., of co-laurolactam (nylon 12), or by condensation and polymerization, e.g., nylon 66 salts and s-caprolactam. 

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). 

Because of the capacity to tailor select polymer properties by varying the ratio of two or more components, copolymers have found significant commercial application in several product areas. In fiber-spinning, ie, with copolymers such as nylon-6 in nylon-6,6 or the reverse, where the second component is present in low (<10%) concentration, as well as in other comonomers with nylon-6,6 or nylon-6, the copolymers are often used to control the effect of spherulites by decreasing their number and probably their size and the rate of crystallization (190). At higher ratios, the semicrystalline polyamides become optically clear, amorphous polymers which find applications in packaging and barrier resins markets (191). 

Second behind packaging in the United States is the use of polymers in fiber and fiberfill applications that encompass the apparel, sports equipment, building and construction, electronic, furniture and furnishings, and industrial/machinery markets. In 1998, 4.8 million metric t of manufactured fiber was produced for use in traditional consumer products such as apparel, carpets, upholstered furniture, and bedding as well as in high-tech applications such as composite materials, medical devices, and electronic circuit boards (17). Key fiber types include polyester, nylon, olefin,... 

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