HEADING 39.07 - POLYACETALS OTHER POLYETHERS AND EPOXIDE RESINS IN PRIMARY FORMS; POLYCARBONATES ALKYD RESINS POLYALLYL ESTERS AND OTHER POLYESTERS IN PRIMARY FORMS.
109 COMMODITIES
3907.10 - Polyacetals
3907.20 - Other polyethers
3907.30 - Epoxide resins
3907.40 - Polycarbonates
3907.50 - Alkyd resins
3907.60 - Polyethylene terephthalate
- Other polyesters :
3907.91 - - Unsaturated
3907.99 - - Other
This heading covers :
(1) Polyacetals. Polymers obtained from an aldehyde normally formaldehyde and characterised by the presence of acetalfunctions in the polymer chain. They are not to be confused with the polyvinyl acetals of heading 39.05 in which the acetal-functions are substituents on the polymer chain. This family of plastics includes acetal copolymers and is regarded as engineering plastics being used for ring bearings cams automobile instrument housings doorknobs pump and air impellers shoe heels mechanical toys plumbing fittings etc.
(2) Other polyethers. Polymers obtained from epoxides glycols or similar materials and characterised by the presence of ether-functions in the polymer chain. They are not to be confused with the polyvinyl ethers of heading 39.05 in which the ether-functions are substituents on the polymer chain. The most important members of this group are polyoxyethylene polyoxypropylene and polyphenylene oxide (PPO) (more correctly named poly(dimethylphenylene-oxide)). These products have a variety of uses PPO being used like the polyacetals as engineering plastics polyoxypropylene as an intermediate for polyurethane foam.
(3) Epoxide resins. Polymers made for example by condensing epichlorohydrin (1-chloro-2 3 with bisphenol A (4 4 novolak (phenolic) resins or other polyhydroxy compounds or by epoxidising unsaturated polymers. Whatever the basic structure of the polymer these resins are characterised by the presence of reactive epoxide groups which allow them to be readily cross-linked at the time of use e.g. by the addition of an amino compound an organic acid or anhydride a boron trifluoride complex or an organic polymer.
Epoxide resins range from low viscosity liquids to high melting solids; they are used as surface-coatings as adhesives as moulding or casting resins etc.
Epoxidised animal or vegetable oils are classified in heading 15.18.
(4) Polycarbonates. Polymers obtained for example by condensing bisphenol A with phosgene (carbonyl chloride) or diphenyl carbonate and characterised by the presence of carbonic ester-functions in the polymer chain. These have a number of industrial applications particularly in moulded articles and as glazing.
(5) Polyesters. These polymers are characterised by the presence of carboxylic ester functions in the polymer chain and are obtained for example by condensation of a polyhydric alcohol and a polycarboxylic acid. They are thus distinguished from polyvinyl esters of heading 39.05 and polyacrylic esters of heading 39.06 in which the ester groups are substituents on the polymer chain.
Polyesters include :
(a) Alkyd resins. Polycondensation products of polyfunctional alcohols and polyfunctional acids or their anhydrides one of which at least must be partly or wholly tri- or higher functional modified with other substances such as fatty acids or animal or vegetable oils monofunctional acids or alcohols rosin. They do not include oil-free alkyds (see Item (d) below). These resins are used mainly as coatings and in high grade varnishes and are supplied usually in viscous form or solution.
(b) Polyallyl esters. A special class of unsaturated polyesters (for the term " unsaturated " see Item (d) below) derived from esters of allyl alcohol with dibasic acids for example diallyl phthalate. They are used as laminating adhesives coatings varnishes and in applications requiring microwave transparency.
(c) Polyethylene terephthalate (PET). Polymers obtained from the reaction of dimethyl terephthalate with ethylene glycol. Apart from its very important use in textiles it finds application for example in packaging films recording tapes soft-drink bottles.
(d) Other polyesters. These may be unsaturated or saturated.
Unsaturated polyesters are those which possess sufficient ethylenic unsaturation that they can readily be (or already have been) cross-linked with monomers containing ethylenic unsaturation to form thermosetting products. Unsaturated polyesters include polyallyl esters (see Item (b) above) and other polyesters (including oil-free alkyds) based on an unsaturated acid for example maleic or fumaric acid. These products which are usually in the form of liquid prepolymers are mainly used for producing glass fibre reinforced laminates and cast transparent thermosetting products.
Saturated polyesters include polymers based on terephthalic acid for example polybutylene terephthalate and saturated oil-free alkyd resins.
They are largely used for textile fibres and films.
For the classification of polymers (including copolymers) chemically modified polymers and polymer blends see the General Explanatory Note to this Chapter.FI