[GreenYes] Re: Plastics definition

["David Biddle" <Dbiddle@no.address>]

Title: Re: [GreenYes] Plastics definition

Okay, Amy, plastics aren’t necessarily petroleum based. You got me. But, and I say this with all sincerity (really!), I never felt like I knew as much as you did. In the interest of learning for all of us, here is something I yanked off the Net which seems pretty much definitive. 

Thanks Amy.

db

Reference: From Mindfully.org    (which is a pretty interesting site).


Plastics Terminology

A dictionary of technical terms defines the word "plastic" as "capable of being molded or modeled". It defines "plastics" as " nonmetallic moldable compounds and the articles made from them". Recent use has also given the adjective, "plastic," the additional meaning of " made of plastics". An apt definition of plastics has been given by the head of the Monsanto Plastics Research who says, "Plastics are materials that, while being processed, can be pushed into almost any desired shape and then retain that shape."

The term "plastics" is a commercial rather than a scientific phraseology, because rubber and glass are easily formed into any desired shape during processing, and retain that shape after cooling. The word "plastics" now generally applies to the synthetic products of chemistry. These chemical products can be cast, molded, or pressed into an unlimited variety of shapes.
Classification

Plastics, depending on their physical properties, may be classified as thermoplastic or thermosetting materials. Thermoplastic materials can be formed into desired shapes under heat and pressure and become solids on cooling. If they are subjected to the same conditions of heat and pressure, they can be remolded. Thermosetting materials acquire infallibility under heat and pressure and cannot be remolded.

Plastics may be classified also according to their chemical sources. The twenty or more known basic types fall into four general groups:

    1. cellulose plastics
    include the cellulose nitrates and cellulose acetates. The cellulose nitrate plastics are the oldest in this group, and "Celluloid" is the oldest example. These plastics are made from cotton or wood pulp.

    2. synthetic resin plastics
    include the phenol formaldehyde, phenolic furfural, urea formaldehyde, vinyl, styrene, and acrylic plastics. These plastics are made from phenol, formaldehyde, urea, acetylene, petroleum, glycerol, and phthalic anhydride.

    3. protein plastics
    casein plastics are the most common type in the protein group. They are made from milk. Other protein plastics are made from soy beans, coffee beans, peanuts, and other agricultural products.

    4. natural resins
    include shellac, asphalt, rosin, amber, and pitch. These materials with fillers are usually cold molded.



on 9/5/07 12:45 PM, amy perlmutter at amy@no.address wrote:

> David:
>
> Plastics don't have to be petroleum-based!
>
> Amy


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