Polymerization

Small-angle X-ray scattering

Materials science

Ultimate tensile strength

Scattering

Differential scanning calorimetry

Strain hardening exponent

Polymer

Thermodynamics

Physics

Optics

Microstructure

Composite material

Tacticity

Fourier transform infrared spectroscopy

Extrusion

Toughness

Journal of Macromolecular Science Part B

ABSTARCTIn this work, isotactic polypropylene (iPP) melt was slowly extruded through a slit die of a single-screw extruder. Once the iPP melt left the die, it was uniaxially stretched at different stretching rates (SRs). Via this process its microstructure can be manipulated, it was subsequently investigated by wide-angle X-ray diffraction (WAXD), small-angle X-ray scattering (SAXS), differential scanning calorimetry (DSC), polarized optical microscopy (POM), and Fourier transform infrared spectroscopy (FTIR). Furthermore, the mechanical properties (including tensile strength, modulus, toughness, and strain-hardening) were investigated. The results showed that the tensile strength and modulus of the melt-stretched iPP films gradually increased with increasing SRs. In addition, the toughness and elongation at break showed maximum values for iPP films melt-stretched at 30 cm/min. Moreover, compared with other melt-stretched films, the iPP films melt-stretched at 90 cm/min exhibited an obvious strain-hardening behavior at lower strain.

Microstructure and Mechanical Properties of Isotactic Polypropylene Films Fabricated via Melt-Extrusion and Uniaxial-Stretching