Evolution of Crystalline Orientation and Texture during Solid Phase Die-Drawing of PP-Talc Composites Rahul H. Rane, 1 Krishnamurthy Jayaraman, 1 Kevin L. Nichols, 2 Thomas R. Bieler, 1 Michael H. Mazor 3 1 Michigan State University, Chemical Engineering and Materials Science, 428, S. Shaw Lane, East Lansing, Michigan 48824 2 Eovations LLC, 1645 Marquette Street, Bay City, Michigan 48706 3 Dow Chemical Co., Midland, Michigan Correspondence to: K. Jayaraman (E - mail: jayarama@egr.msu.edu) Received 2 June 2014; revised 4 September 2014; accepted 5 September 2014; published online 00 Month 2014 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 (1s 21 ) 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. Orienta- tion 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 direc- tion. 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. V C 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2014, 00, 000–000 KEYWORDS: annealing; composites; crystal structures; drawing; polypropylene; voids; X-ray diffractometry INTRODUCTION High levels of molecular orientation can be produced in semicrystalline polymers by solid phase proc- esses such as roll-drawing and die-drawing at elevated tem- peratures below the melting temperature. 1–4 Solid phase processing may be applied to polymer composites as well: for example, die-drawing of particulate filled polyolefins at elevated temperatures was developed recently to produce expanded and oriented particulate composites that are lighter and stronger after processing. 5,6 During die-drawing, the polymer will debond from the particles leading to grow- ing voids near the tips or edges of the particles 7,8 ; it is important to evaluate how these microstructural changes in the drawn composite influence the development of orienta- tion of the polymer and this is the motivation for the present article. Isotactic polypropylene homopolymer (i-PP) was cho- sen as the matrix for the current investigation; its crystal structure is dominated by the a-form, 9,10 which has a mono- clinic unit cell with adjusted orthogonal crystal axes labeled, a*, b, and c. The crystalline domains or spherulites in i-PP are typically cross-hatched or comprised of radial and tangential lamellae separated by amorphous regions. Talc flakes were chosen as the particulate phase. The presence of talc particles changes the morphology of the polymer in the vicinity of the particles, 11,12 leading to smaller spherulites and to transcrystalline domains (or layers of columnar crys- tals) near the particle surface. Studies on micron-sized talc composites have shown that as the talc loading is increased, the b-axes of PP crystals orient increasingly along the normal direction (ND) up to 20 wt % of talc and above this loading, the extent of such orientation levels off. 13–15 The crystalline orientation evolves through rearrangements over hierarchical length scales from the spherulitic scale down to the lamellar scale to the crystallographic scale and through recrystallization. 16,17 The extent of crystal disinte- gration resulting from break-up of spherulites and the orien- tation is determined by the temperature and draw ratio. At higher temperatures below the melting temperature of the polymer, disentanglement of amorphous chains from the net- work is easier and reorientation of the chains along the V C 2014 Wiley Periodicals, Inc. WWW.MATERIALSVIEWS.COM JOURNAL OF POLYMER SCIENCE, PART B: POLYMER PHYSICS 2014, 00, 000–000 1 JOURNAL OF POLYMER SCIENCE WWW.POLYMERPHYSICS.ORG FULL PAPER