plastics for the most part are very weak materials, why DO WE UES THEM?
551175
Plastics are not all "weak". Have you tried pulling some 100 lbs test line apart with your hands? Can you tear a zip lock bag apart with your hands? Weak is a relative term. Aluminum is a metal but it can be very soft and "weak" Just look at aluminum foil. \n\nI recently replaced the outside trim on my back door. It was wood but had rotted from being wet most of the winter. It now has a piece of  PVC for the same trim. It will be there for many many years. \n\nMaterials are selected for an application based on many different requirements. Shear and tensile strength are not always an important requirement. In compression, many plastics are more than adequate for the job.
1027689
For the same reason the rest of the body deteriorates with age.  Just like a car deteriorates with age. etc etc... use ..missuse abuse and just wearing out.
67470
Forty years ago, anything made of plastic was considered "cheap." That’s certainly not true today when plastics are used in thousands of products ranging from computers, automobile parts and important medical equipment to toys, cookware, sports equipment, and even clothes. And the plastics industry continues to grow rapidly. Just where do plastics come from?\n\nWhat are plastics?\n\nIt may surprise students to learn that gutta-percha, shellac, and the horns of animals—all naturally occurring substances—were used as plastic material before the first synthetic plastics were produced. Gutta-percha is derived from the sap of certain trees, and shellac is made from the secretions of a tiny scale insect. Before horn can be used, however, it must be "plasticized," or softened, by being boiled in water or soaked in an alkaline solution.\n\nThe first synthetic plastic was made from the plant material cellulose. In 1869, John Wesley Hyatt, an American printer and inventor, found that cellulose nitrate could be used as an inexpensive substitute for ivory. The mixture could be plasticized with the addition of camphor. Celluloid, as this new material was called, became the only plastic of commercial importance for 30 years. It was used for eyeglass frames, combs, billiard balls, shirt collars, buttons, dentures, and photographic film.\n\nIn 1951, two young research chemists for Phillips Petroleum Company (now ConocoPhillips) in Bartlesville, Okla., made discoveries that revolutionized the plastics world. Today, the plastics they discovered—polypropylene and polyethylene—are used to produce the vast majority of the thousands of plastics products all over the world. (Read more about their discoveries in "Serendipity, Science & Discoveries" in this publication.)\n\nThe source for today’s wide variety of plastics? Petroleum.
262692
A note on recyclability . . . \n\nFor food products in the US, recycled plastic must be depolymerized (broken down into component cheicals and no longer be a plastic), then repolymnerized to be used in food-safe applications. This is not the case if one uses recycled plastic to make fabric, or for use in non-foodsafe applications. The capital cost of the plant and energy involved in depolymerizing and repolymerizing the plastic make recycled plastic prohibitively expensive for foodsafe applications.
590034
Aluminium is very popular for its low weight properties. Thats why they use it in aviation and many other industries.
1187133
It really depends on what type of plastic it is.  Some plastics are made to be melted and reused (recyclable plastic), but other plastics are not made to be melted and reused.  These plastics would probably catch on fire before they melted.  What exactly are you trying to do?
1015578
God made the components of plastics. We only "mix" the components.\n\nIs there plastic in the afterlife? Well, why don't we ask who already got there shall we?\nOh wait... no one is coming back... what should we do?!? We can't live without plastic!~ No we can't!! \n\n(j/k)
1086495
plastic is not degradable and if left on the earth would eventually choke the earth, plastic if burnt there is air polution plastics can be recycled but eventually it has to be destroyed, animals have been know to accidently eat plastic, small children usually put plastic toys in their mouth which if of a cheap quality can harm babies, plastic bags in the hands of small children,  can suffocate them if they playfully put it over their heads
1181417
In 35 plus years of experience of materials sales , I can say without a doubt , that the materials used today are :\n1. Friendlier to the environment  2. More affordable \n3. Are safer to use  4. When used according to Manufacturer's recomendations, will provide superior performance.   \nIn summary : Developments in materials through research has made the above possible!
419054
you can search the internet for "recycling plastic materials" in your area, there are many manufacturers who colect (they pay for this kind of waste) PE, PP, PS, ABS or PET and made granules from it, selling them after for more, as raw material.
10417
Trying to outsmart their competition but only they end up doing it to themselves. In other words, By them using cheap materials their cost of manufacturing cars will be lesser. Therefore they dont last while others use high quality materials that last long.
877039
Precede is incorrect to say that ALL plastics are petroleum based. \n\nMost plastics you will encounter are petroleum based - think your coca cola soda bottles, toothbrushes, tupperware containers, the lids of McDonalds soda cups, straws.... the list is very long - simply because they are, and have been for some time, cheap to produce.\n\nThey are very bad for the environment since most of what is produced ends up in landfills. It also isn't a very logical process since a lot of the goods made out of these plastics are containers (like soda bottles) that are used once, then thrown out thus not needing the durability or shelf life that plastics have.\n\nThere is a growing field of science called biopolymers, and a growing market for bioplastics. While this word isn't yet recognized by Microsoft Word, it is often used to describe plastics that biodegrade much faster than petroleum based plastics (think days, on the range of 30 under the right conditions,  as opposed to decades). These plastics are made out of things like corn and/or bagasse (sugar cane derivative). One retailer I know of is World Centric (google them). We bought their plastic cups for a fundraiser recently and you can't even tell the difference! \n\nIt would be interesting to know how much energy it takes to produce these petroleum alternatives and compare it to that of the petroleum plastics.
92563
styrofoam because it is a better insulator of heat than the other materials mentioned\n\nyou do not have to be a physician to know that
1179417
There are some heat treatments or annealing things they do with plastics that may change its strength.
650119
Less dense materials are better insulators. The denser the material, the closer its atoms are together. That means the transfer of energy of one atom to the next is more effective. Thus, gases insulate better than liquids, which in turn insulate better than solids.\n\nAn interesting fact is that poor conductors of electricity are also poor heat conductors. Wood is a much better insulator than copper. The reason is that metals that conduct electricity allow free electrons to roam through the material. This enhances the transfer of energy from one area to another in the metal. Without this ability, the material--like wood..AND IN YOUR CASE RUBBER--does not conduct heat well.
1088357
Actually all plastic is biodegradable, but it is VERY slow to biodegrade.  It degrades better chemically and through other physical processes such as being in sunlight...Plastic will biodegrade after it has gone through other processes over a long time in places like a landfill, and once enough of the chemical and/or physical bonds are broken down that way there are bacteria that love to devour petroleum based products, it just takes a while.
276119
I believe it was the comedian, George Carlin who asked that question first.  His theory is that plastic was the one thing the Earth couldn't make so it evolved man to make plastic.  He went on to theorize that man is a parasite to the Earth and eventually "it will shake us off like fleas on a dog"