High-density polyethylene permeability

PIB exhibits a comparatively low gas permeation (56). In Table 6.5, gas permeation coefficients of some polyolefins are given. Oppanol B 200 is compared with natural rubber, high density polyethylene) and low density poly(ethylene). Certain other Oppanol types have roughly the same permeability to gases as Oppanol B 200. 

From calculations based on permeability data and some laboratory tests, the authors believe that the pressure rise quoted here is less than can be expected with low-density polyethylene. The permeability data in Table III. I show that considerable improvement is possible by using high-density polyethylene. 

To restrict water entry into certain parts of the delivery system and to separate the drug layer from the osmotic layer, different materials are used as barrier layers. In a multilayered reservoir, the water-permeable coat consists of hydrophilic polymers. In contrast, water-impermeable layers are formed from latex materials such polymethacrylates (Table 7.1). Further, a barrier layer can be provided between the osmotic composition and the drug layer that consists of substantially fluid-impermeable materials such as high-density polyethylene, a wax, a rubber, and the like.20... 

High density polyethylene (HDPE) is used to make automotive fuel tanks as is an alternative material to steel. HDPE has many advantages over steel, especially the design freedom to utilise unused space and low weight. However, the shortcoming of HDPE is its permeability to gasoline and methanol so, therefore, it cannot maintain the right emission standards. Since the permeability of the liquid in the polymer depends both on the nature of the bulk as well as the surface of the polymer, the surface modification of this... 

HDPE (high-density polyethylene).t These plastics have minimal branching, which makes them more rigid and less permeable than LDPEs. 

Films. Three films were included in this study. Low density polyethylene (LDPE) was included as a representative polyolefin. It is not considered to be a barrier polymer. It has permeabilities to selected aroma compounds slightly higher than the permeabilities of polypropylene and high density polyethylene (1). A vinylidene chloride copolymer (co-VDC) film was included as an example of a barrier that is useful in both dry and humid conditions. The film was made from a Dow resin which has been designed for rigid packaging applications. A hydrolyzed ethylene-vinylacetate copolymer (EVOH) film was included as an example of a barrier film that is humidity sensitive. The polymer was a blend of resins with total composition of 38 mole% ethylene. 

For hydrated products, the answer is more complex. The shelf life of the product may be dependent upon retaining a certain amount of moisture in the package. To prevent dehydration over time, a water proof barrier is needed. Contrary to common perception, polyethylene (PE) and high-density polyethylene (HDPE) are quite permeable to water vapor. Some plastics are better than others but none of them eompare to foil. Not only is foil packaging expensive, it is not see-through. Being transparent may be important. 

M.A. Osman, A. AtaUah, High-density polyethylene microand nanocomposites effect of particle shape, size and surface treatment on polymer crystalltnity and gas permeability, Macromolecular Rapid Communications 25 (2004) 1540-1544. 

The lightweight flexible sheet materials suitable for use as breather membranes in most forms of wall construction are manufactured firom high-density polyethylene or polypropylene, PTFE (Teflon), or a combination of both. A flexible membrane coated or laminated to an outer base fabric controls the moisture permeability through the fabric. 

The common plastic films used in MAP are low-density polyethylene (LDPE), linear low-density polyethylene (LLDPE), high-density polyethylene (HOPE), polypropylene (PP), polyvinyl chloride (PVC), poly-ethylene terephthalate (PET), polyvi-nylidene chloride (PVDC) and polyamide (Nylon). PVDC, PVC, PET and nylon have low gas permeability and can be used only for slow respiring cormnodities. However, perforating the films can extend their use to many conunodities. 

Consider the case of a moisture-sensitive item that must be kept in an atmosphere of less than 10% relative humidity. This means that the partial pressure of moisture in the air cannot exceed 10% of the saturation vapor pressure. To protect the item against accidental excursions of the humidity of the surrounding air, it is proposed to package it in an appropriate material. Inspection of Table 3.6 shows that high-density polyethylene has a suitably low permeability to water vapor. We now stipulate that the thickness of the packaging material should be sufficient to protect the item against the accidental exposure to 95% humidity air of 1-h duration. 

Novel polymer-ceramic nanocomposite membranes were fabricated, characterized, and tested for their barrier performance. Atomic layer deposition (ALD) was used to deposit alumina films on primary, micron-sized (16 and 60 pm) high-density polyethylene (HOPE) particles at a rate of 0.5 nm/cyde at 77 °C. Well-dispersed polymer-ceramic nanocomposites were obtained by extruding aluminapolymer particle size. The diffusion coefficient of fabricated nanocomposite membranes can be reduced to half with the inclusion of 7.29vol.% alumina flakes. However, a corresponding increase in permeability was also observed due to the voids formed at or near the interface of the polymer and alumina flakes during the extrusion process, as evidenced by electron microscopy [1]. 

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