Effect of chain extender and terpolymers on tensile and fracture properties of polyamide 6

Preparation of a Novel Branched Polyamide 6 (PA6) via Co-Polymerization of ε-Caprolactam and α-Amino-ε-Caprolactam

In this study, a novel branched polyamide 6 has been synthesized via the hydrolytic ring-opening co-polymerization of ε-caprolactam (CPL) and α-Amino-ε-caprolactam (ACL). The NMR characterization proves the existence of a branched chain structure. The rheological test determines that there is a remarkable increase in the melt index (MFR), zero shear rate viscosity, and storage modulus in the low-frequency region. The shear-thinning phenomenon becomes more obvious. The thermal properties tested by differential scanning calorimetry (DSC) show that the melting point and crystallinity of co-polymers decrease with the incorporation of ACL. However, the crystal structure of the samples only exhibits a slight change. When the ACL content in the feed is 1 wt%, the tensile strength and fracture elongation rate of the co-polymers show a significant enhancement.

Post-Polymerization Heat Effect in the Production of Polyamide 6 by Bulk Quasiliving Anionic Ring-Opening Polymerization of ε-Caprolactam with Industrial Components: A Green Processing Technique

Bulk, solventless anionic ring-opening polymerization (AROP) of ε-caprolactam (CPL) with high yields, without side products and with short reaction times, initiated by caprolactamate-carbamoylcaprolactam initiating systems belong to green polymerization processes, leading to poly(ε-caprolactam) (Polyamide 6, PA6, Nylon 6). However, the effect of post-polymerization heat (i.e., slow, technically feasible cooling) on the fundamental characteristics of the resulting polymers such as yield and molecular weight distributions (MWDs) have not been revealed thus far. Significant post-polymerization effect was found by us in terms of both monomer conversions and MWDs by carrying out CPL polymerization with industrial components under conditions mimicking thermoplastic reaction transfer molding (T-RTM). Remarkably, higher monomer conversions and molecular weights (MWs) were obtained for Polyamide 6 samples prepared without quenching than that for the quenched polymers at the same reaction times. Independent of quenching or non-quenching, Mn of the resulting polymers as a function of conversion fell in the theoretical line of quasiliving AROP of CPL. At high monomer conversions, significant increase of the MW and broadening of the MWDs occurred, indicating pronounced chain–chain coupling. These findings have fundamental importance for designing processing conditions for in situ polymerization processes of ε-caprolactam by various techniques such as T-RTM, reaction injection molding (RIM), and other processing methods of Polyamide 6.

Effect of fiber content on flexural properties of glass fiber-reinforced polyamide-6 prepared by injection molding

The use of non-metal clasp denture (NMCD) materials may seriously affect the remaining tissues because of the low rigidity of NMCD materials such as polyamides. The purpose of this study was to develop a high-rigidity glass fiber-reinforced thermoplastic (GFRTP) composed of E-glass fiber and polyamide-6 for NMCDs using an injection molding. The reinforcing effects of fiber on the flexural properties of GFRTPs were investigated using glass fiber content ranging from 0 to 50 mass%. Three-point bending tests indicated that the flexural strength and elastic modulus of a GFRTP with a fiber content of 50 mass% were 5.4 and 4.7 times higher than those of unreinforced polyamide-6, respectively. The result showed that the physical characteristics of GFRTPs were greatly improved by increasing the fiber content, and the beneficial effects of fiber reinforcement were evident. The findings suggest that the injection-molded GFRTPs are adaptable to NMCDs because of their excellent mechanical properties.