The Processability and Mechanical Properties of Polyamide 6 Were Improved by Chain Extension in Extrusion

Polyamide-6 (PA6) is one of the most widely used engineering thermoplastics due to its excellent overall properties. The macromolecular chain of PA6 contains many highly polar amide groups, which is easy to absorb water. In the process of high-temperature processing, a small amount of water and impurities will lead to hydrolysis. The results showed that molecular weight, melt viscosity and mechanical properties of PA6 decreased after processing. In the process of melting extrusion, it is usually very difficult to improve the mechanical properties and machining capacity of polyamide-6 (PA6) by extension chain method.

To solve this problem, engineers tried to design and synthesize a novel small molecule tri-epoxy chain extender (D1) and used it to modify PA6. Rheological measurement results show that the shear viscosity of PA6 containing 2 wt % D1 is 52.2% lower than that of the original PA6 at the shear rate of 1000s−1, which is within the range of shear rate of industrial thermoplastic machining. This interesting result is attributed to the long chain branched structure of the large molecular chain of PA6, which decreases the power law index and aggravates the shear thinning behavior of the PA6 melt. In addition, the corresponding dent impact strength increases from 62.4 to 105.9 J/m. This provides a feasible method for preparing PA6 with excellent mechanical properties and processability in industrial production.

DOI：10.1021/acs.iecr.0c02022