# Influence of Hexylene Glycol Terephthalate Chain Segments on the Crystallization and Thermal Properties of Polyamide 6

## TL;DR

This study explores how adding BHET segments affects the crystallization and thermal properties of a polyamide copolymer.

## Contribution

The novel contribution is the investigation of how BHET segments disrupt hydrogen bonding and crystallization in polyamide 6.

## Key findings

- BHET segments reduce melting point, crystallization temperature, and crystallinity of the copolymer.
- Thermal stability decreases, and crystalline form shifts from α to γ phase with BHET addition.
- Molecular simulations reveal changes in interchain hydrogen bonding due to BHET segments.

## Abstract

In this study, a poly [ε-caprolactam-co-bis(2-hydroxyethyl) terephthalate] copolymer (P (CL-co-BHET)) was synthesized from para-terephthalic acid (PTA), ethylene glycol (EG), and caprolactam (CL). The crystallization behavior and thermal stability of the copolymer were thoroughly investigated. With the aid of molecular simulation, this study investigated the variation in interchain hydrogen bonding in the copolymer, focusing on the direction and the number of hydrogen bonds. The results revealed a close relationship between the copolymer chain structure, the variation in interchain hydrogen bonding, and the crystallization behavior and thermal stability of the copolymer. The introduction of BHET segments disrupted the regularity of the PA6 backbone and hydrogen bonding, leading to a decrease in the melting point, crystallization temperature, and crystallinity of the copolymer. The thermal stability of the copolymers also decreased, and the crystallization form gradually shifted from the α-crystalline to the γ-crystalline phase. The findings of this study are significant for evaluating the crystallization behavior of polyester amides and for predicting and regulating the properties of polyesteramide polymers.