Chain extension of recycled PA6

Abstract

1Recycling of polymers is a necessity in our intensively consuming polymer world but 2 the nature of polymers is such that they are prone to thermal degradation when re-extruded 3 and this poses technical challenges to recycling. This papers describes research that seeks to 4 rebuild the structure of degraded PA6. We present data from controlled experiments with 5 pristine pPA6 extruded to form a base recycle rPA6 to which we added two chain extenders, 6 separately: one with anhydride multifunctionality (ANHY), highly reactive with amide groups 7 and one with epoxy multifunctionality (EPOX), less reactive. We found from rheological data 8 carried out in the linear viscoelastic region (so as to study structural changes) a striking 9 difference in the ability of the chain extenders to rebuild structure: 306% increase in the 10 complex viscosity of rPA6/ANHY compared to 25% in that of rPA6/EPOX of the base rPA6.

Chain extension of polyamide 6/organoclay nanocomposites

“…Such a behavior is consistent with the observations made by Najafi et al and Ghanbari et al . With regard to the evidence of chain branching, it is also important to note that overdosing with Joncryl with loading larger than 1% leads to very high torques developing during extrusion, making it impossible to operate, suggesting crosslinking as observed in our previous work .…”

“…This requirement is found in Joncryl® ADR 3400, a styrene maleic anhydride copolymer with repeated anhydride groups (see the structure in Fig. ), which we have tested successfully in a previous study with recycled PA6 .…”

Thermal Stability and Early Degradation Mechanisms of High‐Density Polyethylene, Polyamide 6 (Nylon 6), and Polyethylene Terephthalate

“…Nevertheless, recycling usually yields polymeric products with inferior properties to the original materials. This inferiority is because recycled plastic products accumulate thermal and mechanical history and contain the remains of polymeric additives, residual contaminants, labels, and dirt . Despite their scientific and practical importance, the limits of the thermal stability of these polymers are still not well understood.…”

Reactive Extrusion of Polyamide 6 Using a Novel Chain Extender

“…Like all thermoplastics, PA6 is heated before being shaped into a final product, usually in an extruder or an injection moulding machine where the melted polymer is intensely sheared at temperatures higher than its melt temperature (220 o C) for several minutes when processed at industrial scale [5]. At extrusion temperatures above 300 o C, such exposure to heat and shear causes PA6 degradation, a chemical reaction where one of two chain scissions can occur: (i) a thermal only breaking of the chain linking the amide CONH 2 and alkyl group (CH2) 5 or (ii) if water is present, the chain linking the carboxyl (COOH) and amine (NH 2 ) groups in the recurring amide group (CO-NH) is hydrolysed [6][7][8]. These degradation reaction mechanisms are shown in Fig.…”