Utilizador:Antonio Cruz/Rascunhos

TEXTO EM PROCESSO DE TRADUÇÃO Pg. 1206

GLASS

Bottles, jars, and jugs and ampoules made of glass are used in the industry for food and pharmaceutical packaging. Glass packaging is usually formed directly from the molten raw materials into the package. This means that material testing generally must be conducted on the package itself rather than on a sheet or resin pellet as is an option in papers, metals, and plastics. Most standards have to do with maintaining production quality and dimensional consistency (TABELA DADA; COPIEI PARA AQUI). Glass properties are dependent on the composition. Appropriately equipped analytical laboratories can determine this, but in glass manufacturing plants, density and softening point can be substituted for a full analysis. Strength in glass is not typically measured using a tensile strength as in most other materials, because it is extremely strong but extremely brittle. Compressive strength measurements of glass result in much higherstrength values than tensile strength measurements. Glass packages generally break at lower values than the theoretical expectations because of small cracks on the surface that serve as stress concentration points. Online application of pressure, at squeezing stations on glass package-making lines, is used to prevent cracked, broken, or weak packages from advancing into the process. Internal pressure resistance is an important property of glass containers, which will endure pressures such as sterilizing in the package and carbonation. The compressive strength of glass packages reflects their ability to support the load in stacking systems and when closures are applied. It is generally addressed during the design stage by selecting appropriate neck and body diameters and shoulder radius. The heel design of containers can also improve strength.

Thermal shock is a measure of glass’ tendency to crack under heat. This is important for hot fill, retorting, and applications in which the product is heated in glass by the consumer to be served. Finite-element analysis is used to model this. Glass is often used for its superior optical properties. Thus, measurement of these properties is important. On glass production lines, automated inspection stations are used to verify that the containers are free of sand, dirt, stones, and other visual defects. Clarity and color, and the consistency of both, are important in glass manufacture and use. When printed or when graphics are formed into the glass surface, the appearance of these aesthetics also needs to be measured. The containment capability of a glass container is dependent not only on the properties of the particular glass formula but also on the thickness of the container walls. Additionally, the total weight of each container must be measured and controlled to assure consistency of cost, performance, and fill weights. The finish dimensions must be consistent to assure that the cap/closure system fits properly, offers correct opening strength, and provides an appropriate seal of the package. Glass offers excellent water vapor and gas-barrier properties. When pigmented, it provides light control as well.

tabela das propriedades

Composition . Composition . Density . Softening point Strength . Compressive . Stacking strength . Hydraulic pressure strength . Impact strength Thermal shock Visual/optical . General visual quality . Clarity . Color Dimensions . Container weight . Wall thickness . Finish dimensions . General dimensions Permeability

Pg.1075: In the United Kingdom, paper and board account for 43% by weight of all packaging (2). Paper and board packaging make up 6.4% of the overall content of typical household waste. For further information on paper and cardboard recycling, see Waste Watch’s Paper information sheet. Plastics account for 20% of the weight of all packaging. Glass accounts for 20% of the weight of all packaging and 10% of all goods are packaged in glass.