PET modified new additives

Clariant Masterbatch has launched a new series of reactive additives that can increase the intrinsic viscosity of recycled PET (RPET) without curing in the reactor. This chain extender, called CESA-Extend, does not affect mechanical or thermal properties. In the case of performance or crystallinity, the molecular weight is restored to the original level or even higher.

Conventional chain extenders require preheated PET to be heated in a highly vacuumed state for a few hours in a curing reactor, which generates gels during uncontrolled chain branching. CESA-Extend can be processed on a conventional twin-screw extruder without pre-drying PET or vacuum, resulting in less gel.

Clariant said that its new additive can also improve the blending of EPET with other polyesters, PCs, and nylons in future compounding. The reflectance component is a proprietary functional polypropylene oligomer from Johnson Polymer LLC of Sturtevant, Wisconsin. The company shares certain patented technologies with Clariant.

The above active additives can be combined with any polycondensation resin including PC, nylon, acetal, TPU, PBT, and blends of the above, but the effect is better in PET and nylon is inferior. It reacts with polar groups such as amines, isocyanates, hydroxy groups, and the like.

This additive greatly improves the melt strength of the polymer so that the PET can be blow molded and even processed into a blown film. Extrusion of raw un-dried PET (0.75 IV) plus 3% CESA-Extend, under vacuum, PET produced 0.78 IV, without chain extender, the same PET dropped to 0.543 IV, recovered 0.558 IV PET plus 2% CESA-Extend produced 0.673 IV, plus 3% produced 0.72 IV.