دانلود کتاب راهنمای بوها در مواد پلاستیکی

Olfaction is one of the senses − smell. Olfaction or the sense of smell can recognize the smell of different odorants. Each chemical substance is a different odorant, which can be recognized by the sense of smell at a particular concentration. Sensitivity of olfaction for the different odorants varies, which makes the usefulness of smell a complex matter in recognition of the danger of the presence of different chemicals in our surroundings. Some chemical compounds can be recognized by the sense of smell at very low concentrations (0.00000001 mg/l). On the one hand, smell is a very powerful early warning system, but on the other hand the extensive smell of a chemical compound does not necessarily mean that the chemical compound is present at a high or a dangerous concentration. At the same time, intensity of smell is a characteristic feature of a chemical substance and its presence affects the olfactory response of a material into which the chemical compound is incorporated. Most products are meant to have no smell. There are exceptions, such as fragrances, flowers, or cosmetics, in which the composition of volatile odorants (scents or aromas) is very essential to their appeal, but in most cases products should have no odor. Product and processing technology are typically concerned about the selection of the best composition of materials which can be easily processed to form a product having the best possible properties to satisfy user needs. Odor formation is the result of composition or may be caused by processing or other external factors, discussed below. In most technological processes, odor is not a factor to be considered unless there are complaints from users.