Conventional polyethylene terephthalate (PET) preforms uses Solid State Polycondensation (SSP) process. A new technology to produce PET preforms directly from the polycondensation reactor to the injection perform machine, as an alternative to the conventional SSP process followed by granulating and injection steps, has been developed. The German firm Zimmer has already started a new pilot plant for the production of bottle preforms with its “Direct To Preform” process (DTP). The plant comprises a polycondensation reactor for high bottle-grade polymer viscosities, a melt distribution system suited for dosing various additives as well as a preform machine supplied by Husky. The feed zone of the machine extruder has been modified to accept PET melt feed rather than the usual granules. Uhde Inventa-Fischer has also developed a melt to preform process.

Solid State Polycondensation applies to crystal polymers (mainly PET and PC). What Polycondensation does, is not only upgrade the IV of the polymer, that's important anyway, but also remove monomers and other dangerous chemicals, specially when raw material is made out of scrap.

All the present methods use solid state polymerization after the initial polymerisation, in which intrinsic viscosity upto 0.6 can be achieved. The solid state polymerization not only increases viscosity to more than 0.8 required for bottles, but also eliminates the monomer as well as impurities. With this new method, it is possible to eliminate the costly process of solid state polymerization. It is expected that this new alternate route could take a few years for commercial reality.