The present invention provides a method of manufacturing high-melting-tension heat-resistant transparent or opaque sheets, boards, and moulds from
polyethylene terephthalate (PET). The method is characterised in that a mixture of: (1) PET
polyester whose melt flow rate (MFR) is 45-130 g / 10 minutes (a); (2)
coupling agent master batch (f) comprising
coupling agent (d) and substrate (e), wherein
coupling agent (d) is a mixture of compounds containing 2
epoxy groups (b) and compounds containing 3 or more
epoxy groups (c); and (3) catalyst master batch (i) comprising
coupling reaction catalyst (g) and substrate (h); is melted in a reaction-extruder to give PET
polyester whose MFR is 40 g / 10 minutes or less. The resulting PET
polyester is moulded into amorphous sheets or boards, and then heated again to a predetermined temperature to give transparent heat-resistant sheets or boards; or then vacuum-, pressure-, or vacuum-pressure-formed following heat-setting to give transparent heat-resistant or white opaque highly-heat-resistant mould articles.