Utilizador:Diogo Alves/Rascunho: diferenças entre revisões

Conteúdo apagado Conteúdo adicionado
Madeira
Vidro vantagens e desvantagens
Linha 1:
Glass has beenand will remainan important packaging material for a number of products because it is strong, durable, transparent, and chemically inert. Pleasing to the eye, it evokes an image of quality and allows the consumer to see the product. Glass is impervious to transmission of gases and products and, therefore, is used extensively to contain delicate flavor and perfume essences. It also is proof against the harshest acids and bases known to chemistry (except for hydrofluoric acid, which is actually used to etch glass).
Wood is a structural material developed by nature to support the foliage and fruit of trees and is remarkably strong for its weight. Being a natural material, it is not very uniform in its physical characteristics, however, and it becomes necessary to select and treat it to make it useful as a packaging material. Some types of wood and certain parts of the tree are better suited for packaging than others. Even growing conditions will have an effect on the wood's strength and other qualities.
 
Glass containers also can be used in microwave ovens and served at the table without the contents being transferred to another receptacle. All colors of glassflint, green, opal, and amberare equally transparent to microwave energy. It is strongly recommended that closures be loosened before the containers are put into the oven for heating to prevent pressure buildup. But even when it is on tight, tests indicate that the cap will blow off before the container explodes.
Glass is made from relatively inexpensive domestic raw materials, but the process is rather energy-intensive.
Fortunately, by selecting the proper variety, sorting it for knots and other defects, drying it carefully, and sometimes laminating it to make plywood, it is possible to produce a fairly uniform material suitable for packaging. About fifteen times stronger with the grain than across it, wood has a tendency to split when fastened together to make a box or crate, and to shrink and warp on standing. Nevertheless, it is a valuable component for large packages.
Despite lightweighting efforts, glass is still heavier than a comparably sized plastic or aluminum container, which means it is more costly to transport. Breakability is another negative although new coatings that reduce abrasion and, therefore, breakage are being pursued.
{{AutoCat}}