Evolution of crystalline orientation and texture during solid phase die-drawing of PP-Talc composites

• Published in: Journal of polymer science. Part B, Polymer physics Vol. 52; no. 23; pp. 1528 - 1538
• Main Authors: Rane, Rahul H., Jayaraman, Krishnamurthy, Nichols, Kevin L., Bieler, Thomas R., Mazor, Michael H.
• Format: Journal Article
• Language: English
• Published: Hoboken, NJ Blackwell Publishing Ltd 01.12.2014; Wiley; Wiley Subscription Services, Inc
• Subjects: annealing; Applied sciences; Billets; Composites; Crystal structure; crystal structures; Draw ratio; Exact sciences and technology; Forms of application and semi-finished materials; Mechanical properties; Organic polymers; Orientation; Physicochemistry of polymers; Polymer industry, paints, wood; polypropylene; Polypropylenes; Properties and characterization; Surface layer; Technology of polymers; Texture; Voids; X-ray diffractometry; Hot deformation; Crystal form; Crystal orientation; Propylene polymer; Dispersion reinforced material; polypropylene; Experimental study; annealing; Texture; crystal structures; voids; Composite material; Mechanism; Growth from solid state; composites; Hot drawing; Oriented polymer; Isotactic polymer; X-ray diffractometry; drawing; Olefin polymer; Elongation (mechanics)
• ISSN: 0887-6266; 1099-0488
• DOI: 10.1002/polb.23592

ABSTRACT The objective of the present work was to examine the development of crystalline orientation and texture in the polypropylene matrix of talc‐filled i‐PP and in unfilled i‐PP with increasing draw ratio during solid‐phase die‐drawing at high strain rates (∼1 s−1) and a die temperature of 145 °C. After drawing, the entire billet was cooled rapidly “under tension” to room temperature before releasing the billet and cutting specimens from different axial locations for analysis. Orientation distributions of the three crystal axes for increasing axial strains have been presented as pole figures in the MD‐TD plane with the direction of draw (MD) as the reference direction. While disruption of spherulites was noticed within the die for neat PP at a draw ratio of 1.5, transcrystalline domains within the composite persisted even at a draw ratio of 3.5 in the free draw region outside the die. The transformation to fibrillar crystal morphology was complete in both materials at a draw ratio of 4.5 but the texture continued to develop beyond this stage. While the (110)[001] texture component was found to be dominant at all draw ratios for neat PP, the (010)[001] texture component was dominant at the higher draw ratios in the drawn composite. This may be attributed to the (010)[001] slip system being more active as the transverse spacing between elongated voids encasing the particles was decreased. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2014, 52, 1528–1538 Die‐drawing of polymer composites is capable of producing high levels of molecular orientation. In this work, the progress of crystalline orientation in a talc‐filled semicrystalline polypropylene composite is analyzed as draw ratio increases at high strain rates and high temperatures, while elongated voids develop. This is compared to the orientation progress in unfilled polypropylene, which also undergoes solid phase die‐drawing after annealing at high temperatures but does not develop any voids.