Structural Hierarchy of PA6 Macromolecules after Hydrostatic Extrusion

Area of Science:

• Materials Science
• Polymer Science
• Mechanical Engineering

Background:

• Polyamide 6 (PA6) is a widely used engineering thermoplastic.
• Severe plastic deformation (SPD) techniques can modify polymer properties.
• Hydrostatic extrusion (HE) is an SPD method capable of inducing significant structural changes.

Purpose of the Study:

• To investigate the influence of hydrostatic extrusion (HE) on the thermal and structural properties of polyamide 6 (PA6).
• To understand how varying deformation levels during HE affect PA6's crystallinity and phase composition.
• To correlate processing conditions with resulting material characteristics.

Main Methods:

• Microscopic observations to visualize the fibrous structure formed during HE.
• Differential scanning calorimetry (DSC) to analyze the degree of crystallinity and glass transition temperature (Tg).
• Wide-angle X-ray scattering (WAXS) and Fourier-transform infrared (FTIR) spectroscopy to characterize the crystalline phases (α, α1, α2, γ) and their proportions.

Main Results:

• Hydrostatic extrusion (HE) induced a fibrous structure in PA6 oriented along the extrusion direction.
• The proportion of the crystalline phase α increased by up to 12% with increasing deformation in HE.
• Glass transition temperature (Tg) decreased initially at low deformation (0.68) to 44.2 °C, then increased to 53.2-53.5 °C at higher deformations.
• WAXS and FTIR confirmed the presence and increase of crystalline phases (α1, α2, γ) with higher deformation.

Conclusions:

• Favorable properties in PA6 were achieved when HE processing temperature exceeded the glass transition temperature but remained below the melting point.
• Increased deformation during HE processing significantly enhances the crystalline phase proportion in PA6.
• HE is an effective method for tailoring the thermal and structural properties of PA6 through controlled plastic deformation.