Melt Mastication of Isotactic Polyproyplene for Improved Thermal and Physical Properties

• Published in: Polymer engineering and science Vol. 60; no. 2; pp. 380 - 386
• Main Authors: Cromer, Brian M., Coughlin, Edward Bryan, Lesser, Alan J.
• Format: Journal Article
• Language: English
• Published: Hoboken, USA John Wiley & Sons, Inc 01.02.2020; Society of Plastics Engineers, Inc; Blackwell Publishing Ltd
• Subjects: Annealing; Atomic force microscopy; Birefringence; Calorimetry; Compressive strength; Crystal morphology; Crystal structure; Crystalline polymers; Crystallinity; Crystallization; Crystals; Low temperature; Mastication; Mechanical properties; Melts (crystal growth); Microscopes; Microscopy; Modulus of elasticity; Morphology; Optical microscopy; Physical properties; Polymers; Polypropylene; Propylene; Strain hardening; Thermodynamic properties
• ISSN: 0032-3888; 1548-2634
• DOI: 10.1002/pen.25293

Herein a new polymer processing method referred to as Melt‐Mastication (MM) is presented as way to substantially improve the thermal and mechanical properties of Polypropylene (iPP) and other semi‐crystalline polymers. MM is a low temperature mixing technique that subjects molten iPP to chaotic flow under at temperatures between the melting and crystallization temperatures, thereby promoting flow induced crystallization (FIC). The resulting materials demonstrate an unusual crystal morphology that is highly crystalline by thermal calorimetry (57% crystal volume fraction), melts at a temperature 10.3 K higher than conventionally processed iPP, and demonstrates melt memory after annealing at 200°C. The highly crystalline morphology does not show birefringence in polarized optical microscopy and by SEM and AFM appears to be comprised of largely disorganized lamellar crystals, with possible stacked ordering in local (~1 μm) regions. Melt‐Masticated iPP demonstrates improved compressive modulus (+77%), strength (+40%), and strain hardening modulus in uniaxial compression, which are attributed to enhanced crystal volume fraction, lamellar crystal thickness, and network connectivity, respectively. POLYM. ENG. SCI., 60: 380–386, 2019. © 2019 Society of Plastics Engineers