What property of "plastics" make them non-biodegradable?

Question

and how plastics r exactly made?

as it is a cellulose derivative.

Answer 1

Plastics are polymers meaning they are long chains of molecules in many strong bonds connecting them together.The stonger the bonds are the more time it takes to break the bonds and degrading the product making it biodegradbale.So the polymer bonds are what is making them nonbiodegradable.

Answer 2

Peggy is on the ball with her answer.

The hydrocarbon polymer strings do form very strong bonds, they don't decay and don't react with many things.  Often things degrade of their own accord - iron will rust away in time as it oxidises, plant and animal matter decomposes.  Not so with plastics, you need something to break the bonds such as heat or a solvent and those don't occur naturally in large enough quantities to have an appreciable effect.

It's kind of complicated and lengthy to explain so I'll leave it to Wikipedia to do the rest...

http://en.wikipedia.org/wiki/Plastic

Answer 3

Let me answer your second question first.

The technical term for plastics is "Polymers." A polymer is a "giant molecule" made up of a long repeated "chain" of small, simple molecules. The suffix "poly-" is a Greek word meaning "many." The basic sub-units of polymers are small molecules, referred to a "monomers"; "mono-" meaning "one."

Plastics and polymers are a *very* broad subject, so I will try to condense as much as I can.

For example, many substances found in living things are polymers; proteins, starch, cellulose, and DNA are all polymers. The sub-units or monomers of DNA are called "nucleotides", or "base pairs"; a DNA molecule can be made up of several million base pairs. Cellulose consists of a chain of simple glucose sugar monomers, whereas proteins are made of long or short chains of monomers called "amino acids"

Plastics are man-made polymers. How the plastic is made, depends on what kind of plastic it is, there are literally thousands of different processes.

One common method is to expose the monomers to heat and pressure, in the presence of a specific "Catalyst." This is how vinyl, polystyrene, and polyethylene are made. Some polymers are made of a pair of two different monomers; they need only be mixed together in order to form polymers; nylon, and epoxy glues are two examples. Some monomers are reactive enough that they need only be exposed to oxygen and/or moisture in order to form tough polymers; super glue (cyanoacrylate), or silicones for example.

Rayon is made up of cellulose which has been chemically digested, spun into fibers, and reconstituted.

Now let me answer your first question.

In general, plastics are not biodegradable, if the monomers they are made from, do not naturally oxidize or break down over time.

Unfortunately, this is true of the majority of plastics, since they are usually made of substances not normally found in nature. Indeed, biodegradability is not always desirable, particularly in fibers and structural plastics. Biodegradability is usually desirable for dirt cheap, *disposable* plastic items, such as bottles, containers, packaging, bags, small toys, etc. However, many of the very cheap plastics used for such items, such as polystyrene or vinyl, are not biodegradable. As such, these cheap plastics make up the biggest fraction of all the plastics produced.......

The good news is that these cheap plastics are quite easy to recycle, the bad news is that they hardly ever are.....

Some plastics are specifically designed to be highly stable and resistant to breakdown. Teflon, or PTFE, used in non-stick pans among other things; is nearly impervious to acids, chemicals, and solvents, and can easily resist temperatures of 1,500 degrees or more, without being significantly altered.

Most of the plastics found in modern electronics are not biodegradable in the least. Such items should never be thrown away, but taken to a recycling center. Most of the plastics found in cars are not biodegradable, but because of the expense of cars, they are worthwhile to recycle, and most old cars are.

Probably more than you wanted to know......;-)

~Soylent Yellow

Additional:

To say that non-biodegradable plastics have "strong bonds" is an oversimplification. As I said, many plastics are made of compounds not normally found in nature, and which are unusually stable(.....many of these, in their raw form are environmental pollutants in their own right) These substances don't break down over time, and organisms such as bacteria and fungi simply have no real way of dealing with them, since they have never evolved mechanisms to do so.

Altering the chemical structure of *some* plastics in order to make them biodegradable is possible, but this usually means they will be much more expensive.

You can incinerate most plastics, but you need special equipment, since they will often produce toxic fumes......