Plastics are commonly classified on the basis of their origin:
Natural - These include amber, horn, wax, shellac, rubber
Semi-synthetics - These are chemically modified natural materials like:
Hardened rubber (Ebonite, Vulcanite), casein (Erinoid, Galalith), which is based on milk protein, cellulose nitrate and cellulose acetate, both based on cellulose.
Synthetics - These may be further sub-divided into: Early synthetics: phenol formaldehyde (Bakelite), urea formaldehyde (Beatl, Beetle); The ‘poly’ era: polyvinyl chloride (PVC), polymethyl methacrylate(Perspex, Lucite), polyethylene (Polythene), polyamide (Nylon), polyacrylonitrile (Courtelle, Orlon), polyurethane, polycarbonate, polyester, etc.

Identification of plastics
Although the unambiguous identification of a plastic material requires the use of sophisticated equipment, sometimes an 'educated guess' is sufficient. The probable date of the object, the appearance, feel and smell of the material, and the properties necessary for its use are important clues. For example:

• A hard, dark material from the 1940s , with a Carbolic smell, which was often used in electrical goods is probably a phenol-formaldehyde or Bakelite.
• A flexible clear (or yellowed) material from the 1940s is probably polyvinyl chloride, PVC. Flexible PVC was commonly used in the manufacture of shoes and rainwear in the 1960s and 70s. It was also the main material used in the manufacture of toys such as dolls from the late 1940s onwards. It has a distinct and unique smell of plasticiser.
• A hard, light-colored material, used decoratively and in objects dated 1910-1930, is likely to be a casein-based plastic. Casein is commonly found in buttons, pens, costume jewelry, and dressing table sets. It was also used in the manufacture of decorative inlays in furniture and lamps.
• Dolls, dressing table accessories, combs and, generally, decorations from 1930-1950 are frequently made from cellulose acetate. This can have a smell of vinegar - acetic acid.
• Imitation tortoiseshell is likely to be cellulose nitrate (which smells of camphor). Early film stock is also made from this material.
• Polystyrene was used extensively in the 1940s and early 1950s for hard, brightly-colored toys,
• Foam toys are usually natural rubber or polyurethane,
• 'Bendy' (brand name) toys for example are usually natural rubber. This material may often have an associated smell of sulphur.

 

Specifications for Polyester: Poly(ethylene-terephthalate) PET

as provided by the Library of Congress at http://www.loc.gov/preserv/supply/specs/500-500.html

Specification Number 500-500-7/24/02

This specification is provided as a public service by the Preservation Directorate of the Library of Congress. Any commercial reproduction that implies endorsement of a product, service or materials, in any publication, is strictly prohibited by law. This Specification is written for L.C. purchasing purposes and is subject to change when necessary.

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General Specifications

A. Composition

1. Content:
   Must be a clear, colorless, [biaxially oriented/stressed/drawn] poly(ethylene-terephthalate) film such as DuPont Mylar D, ICI Melinex 516 or the equivalent.
2. Impurities:
   The clear and colorless polyester film must not contain any plasticizer, surface coatings, UV inhibitors, or absorbents and be guaranteed to be non-yellowing with natural aging. As received, the film must not contain any coloring agents.

B. Identification

There must be no identification marks on the film.

C. Packaging

1. Inner Wrapper:
   The polyester, if cut, must be carefully and securely packaged in 100 units or less per package.
2. Outer Wrapper:
   The items must be packed in standard commercial containers which are constructed to ensure that they arrive at the Library of Congress in dry, undamaged condition.
   I.D.: The outside of the carton which contains the packages should be labeled with thickness, size and number of items in the carton, and Purchase Order or RFP number.

D. Workmanship

If cut, edges must be clean, straight, and corners 90 degrees. Each item must be free of dents, dings, fingerprints, scratches, abrasions, inclusions or other evidence of handling which would be detrimental to performance.

E. Testing

1. Responsibility:
   The supplier is responsible for meeting all the requirements specified herein. The Library of Congress has the right to perform tests necessary to verify the requirements.
2. Sampling:
   To sample for testing, shipments will be sampled according to MIL-STD-105E at inspection level S-2 with an acceptable quality level of 2.5 percent defective from each lot offered. Copies of MIL-STD-105E are available from Naval Publications and Forms Center; Standardization Document Order Department, Building 4, Section D; 700 Robbins Avenue, Philadelphia, Pennsylvania, 19111-5094.

F. Quality Assurance Inspection

To evaluate non-tested requirements, shipments will be sampled according to MIL-STD-105E at inspection level S-2 with an acceptable quality level of 4.0 percent defective from each lot offered.

 

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