Plastic tance, and abrasion resistance (1). The strength of the glass container depends greatly on the condition of its surface, and the strength can be greatly reduced by a slight surface scratch. To reduce scratches and impact breakage, various lubricating coatings, such as special waxes and silicones, are often applied to the outer surfaces. Fairly thick glass is often needed to provide sufficient strength to prevent breakage due to internal pressure (especially for carbonated beverage bottles), impact, or thermal shock. This thicker glass, however, adds considerable weight to the package.

Thermal properties include thermal strength, which is a measure of the ability to withstand sudden temperature change. Stresses from sudden cooling are more damaging than those from sudden heating. A simple experiment to determine thermal shock resistance is to observe the number of breakages that occur when glass containers at a high temperature are suddenly transferred to a cold-water bath. The temperatures used in the experiment depend on the actual process temperatures that the container will experience, such as in pasteurization, hot pack, or retorting (1).

Optical properties include the degree of transmission to light and its effects on the quality of the product. Glass can be colored for decoration or light protection. Flint is basic clear glass used for most food-packaging applications. Amber is the familiar brown glass used for beer that can filter out ultraviolet light (300-400 nm). Emerald is bright-green glass used mostly in the beverage industry. Other blue, green, and opaque glasses are also available (2).

In recent years, thin layers of silica (SiOx) are deposited onto films such as polyethylene terephthalate (PET), oriented polypropylene (OPP), and low-density polyethylene (LDPE). These silica-coated (or glass-coated) films have good gas barrier (3), and they are clear, recyclable, and retortable; however, the commercial applications of these films are rather limited because of the high cost and technical difficulties in ensuring good silica adhesion to certain base polymers (4).

Sleeping Sanctuary

Sleeping Sanctuary

Salvation For The Sleep Deprived The Ultimate Guide To Sleeping, Napping, Resting And  Restoring Your Energy. Of the many things that we do just instinctively and do not give much  of a thought to, sleep is probably the most prominent one. Most of us sleep only because we have to. We sleep because we cannot stay awake all 24 hours in the day.

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