Plastics are non-metallic, synthetic, carbon-based materials. They can be moulded, shaped, or extruded into flexible sheets, films, or fibres. Plastics are synthetic polymers. Polymers consist of long-chain molecules made of large numbers of identical small molecules (monomers). The chemical nature of a plastic is defined by the monomer (repeating unit) that makes up the chain of the polymer. Polyethene is a polyolefin; its monomer unit is ethene (formerly called ethylene). Other categories are acrylics (such as polymethylmethacrylate), styrenes (such as polystyrene), vinys (such as polyvinyl chloride (PVC)), polyesters, polyurethanes, polyamides (such as nylons), polyethers, acetals, phenolics, cellulosics, and amino resins. The molecules can be either natural — like cellulose, wax, and natural rubber — or synthetic — in polyethene and nylon. In co-polymers, more than one monomer is used.The giant molecules of which polymers consist may be linear, branched, or cross-linked, depending on the plastic. Linear and branched molecules are thermoplastic (soften when heated), whereas cross-linked molecules are thermosetting (harden when heated).Most plastics are synthesized from organic chemicals or from natural gas or coal. Plastics are light-weight compared to metals and are good electrical insulators. The best insulators now are epoxy resins and teflon. Teflon or polytetrafluoroethene (PTFE) was first made in 1938 and was produced commercially in 1950.Plastics can be classified into several broad types.1. Thermoplastics soften on heating, then harden again when cooled. Thermoplastic molecules are also coiled and because of this they are flexible and easily stretched.Typical example of thermoplastics is polystyrene. Polystyrene resins are characterized by high resistance to chemical and mechanical stresses at low temperatures and by very low absorption of water. These properties make the polystyrenes especially suitable for radio-frequency insulation and for parts used at low temperatures in refrigerators and in airplanes. PET (polyethene terephthalate) is a transparent thermoplastic used for soft-drinks bottles. Thermoplastics are also viscoelastic, that is, they flow (creep) under stress. Examples are polythene, polystyrene andPVC.2. Thermosetting plastics (thermosets) do not soften when heated, and with strong heating they decompose. In most thermosets final cross-linking, which fixes the molecules, takes place after the plastic has already been formed.Thermosetting plastics have a higher density than thermoplastics. They are less flexible, more difficult to stretch, and are less subjected to creep. Examples of thermosetting plastics include urea-formaldehyde or polyurethane and epoxy resins, most polyesters, and phenolic polymers such as phenol-formaldehyde resin.3. Elastomers are similar to thermoplastics but have sufficient cross-linking between molecules to prevent stretching and creep.
I decided to be a journalist. I think it is an interesting and useful profession.
I like to watch TV, listen to the radio, read newspapers and magazines. I like everything which connected with mass media.
I have a hobby. My friends and I are publishing a small newspaper once a month in our school. We write articles about school events, life of young people, jokes, draw pictures and caricatures. My favourite school subjects are history and literature.
I like the profession of a journalist. They meet many people. They try to understand what is going on in the world, or the country, or the city and try to explain it to other people.
I think that the work of a journalist is very much like that of historian. A historian studies and tries to explain events of the past and a journalist does the same about the present.
But for me to be a journalist is much more interesting than to be a historian because you deal with real events that are happening right now so you can even influence them.
So journalists can influence the history. That is why I want to be a journalist.
Я хочу быть журналистом
Я решил стать журналистом. Я думаю, что это интересная и полезная профессия.
Мне нравится смотреть телевизор, слушать радио, читать газеты и журналы. Мне нравится все, что связано со средствами массовой информации.
У меня есть хобби. Мы с моими друзьями издаем в нашей школе небольшую газету раз в месяц. Мы пишем статьи о школьных событиях, жизни молодежи, шутки, рисуем иллюстрации и карикатуры. Мои любимые школьные предметы — история и литература.
Мне нравится профессия журналиста. Они встречаются со многими людьми. Они пытаются понять, что происходит в мире, стране, городе и объяснить это другим людям.
Я думаю, что работа журналиста очень похожа на работу историка. Историк изучает и пытается объяснить события а журналист делает то же самое с настоящим.
Но для меня работа журналиста гораздо интереснее работы историка, потому что ты имеешь дело с реальными событиями, которые происходят прямо сейчас, и таким образом, на них даже можно повлиять.
Итак, журналисты могут повлиять на историю. Вот почему я хочу стать
Plastics are non-metallic, synthetic, carbon-based materials. They can be moulded, shaped, or extruded into flexible sheets, films, or fibres. Plastics are synthetic polymers. Polymers consist of long-chain molecules made of large numbers of identical small molecules (monomers). The chemical nature of a plastic is defined by the monomer (repeating unit) that makes up the chain of the polymer. Polyethene is a polyolefin; its monomer unit is ethene (formerly called ethylene). Other categories are acrylics (such as polymethylmethacrylate), styrenes (such as polystyrene), vinys (such as polyvinyl chloride (PVC)), polyesters, polyurethanes, polyamides (such as nylons), polyethers, acetals, phenolics, cellulosics, and amino resins. The molecules can be either natural — like cellulose, wax, and natural rubber — or synthetic — in polyethene and nylon. In co-polymers, more than one monomer is used.The giant molecules of which polymers consist may be linear, branched, or cross-linked, depending on the plastic. Linear and branched molecules are thermoplastic (soften when heated), whereas cross-linked molecules are thermosetting (harden when heated).Most plastics are synthesized from organic chemicals or from natural gas or coal. Plastics are light-weight compared to metals and are good electrical insulators. The best insulators now are epoxy resins and teflon. Teflon or polytetrafluoroethene (PTFE) was first made in 1938 and was produced commercially in 1950.Plastics can be classified into several broad types.1. Thermoplastics soften on heating, then harden again when cooled. Thermoplastic molecules are also coiled and because of this they are flexible and easily stretched.Typical example of thermoplastics is polystyrene. Polystyrene resins are characterized by high resistance to chemical and mechanical stresses at low temperatures and by very low absorption of water. These properties make the polystyrenes especially suitable for radio-frequency insulation and for parts used at low temperatures in refrigerators and in airplanes. PET (polyethene terephthalate) is a transparent thermoplastic used for soft-drinks bottles. Thermoplastics are also viscoelastic, that is, they flow (creep) under stress. Examples are polythene, polystyrene andPVC.2. Thermosetting plastics (thermosets) do not soften when heated, and with strong heating they decompose. In most thermosets final cross-linking, which fixes the molecules, takes place after the plastic has already been formed.Thermosetting plastics have a higher density than thermoplastics. They are less flexible, more difficult to stretch, and are less subjected to creep. Examples of thermosetting plastics include urea-formaldehyde or polyurethane and epoxy resins, most polyesters, and phenolic polymers such as phenol-formaldehyde resin.3. Elastomers are similar to thermoplastics but have sufficient cross-linking between molecules to prevent stretching and creep.
Объяснение:
Объяснение:
I Want to be a Journalist
I decided to be a journalist. I think it is an interesting and useful profession.
I like to watch TV, listen to the radio, read newspapers and magazines. I like everything which connected with mass media.
I have a hobby. My friends and I are publishing a small newspaper once a month in our school. We write articles about school events, life of young people, jokes, draw pictures and caricatures. My favourite school subjects are history and literature.
I like the profession of a journalist. They meet many people. They try to understand what is going on in the world, or the country, or the city and try to explain it to other people.
I think that the work of a journalist is very much like that of historian. A historian studies and tries to explain events of the past and a journalist does the same about the present.
But for me to be a journalist is much more interesting than to be a historian because you deal with real events that are happening right now so you can even influence them.
So journalists can influence the history. That is why I want to be a journalist.
Я хочу быть журналистом
Я решил стать журналистом. Я думаю, что это интересная и полезная профессия.
Мне нравится смотреть телевизор, слушать радио, читать газеты и журналы. Мне нравится все, что связано со средствами массовой информации.
У меня есть хобби. Мы с моими друзьями издаем в нашей школе небольшую газету раз в месяц. Мы пишем статьи о школьных событиях, жизни молодежи, шутки, рисуем иллюстрации и карикатуры. Мои любимые школьные предметы — история и литература.
Мне нравится профессия журналиста. Они встречаются со многими людьми. Они пытаются понять, что происходит в мире, стране, городе и объяснить это другим людям.
Я думаю, что работа журналиста очень похожа на работу историка. Историк изучает и пытается объяснить события а журналист делает то же самое с настоящим.
Но для меня работа журналиста гораздо интереснее работы историка, потому что ты имеешь дело с реальными событиями, которые происходят прямо сейчас, и таким образом, на них даже можно повлиять.
Итак, журналисты могут повлиять на историю. Вот почему я хочу стать