Polymer Testing 85 (2020) 106439 Available online 18 February 2020 0142-9418/© 2020 Published by Elsevier Ltd. Elucidation of the relationships of structure-process-property for different ethylene/α-olefn copolymers during flm blowing: An in-situ synchrotron radiation X-ray scattering study Haoyuan Zhao a , Qianlei Zhang a , Zhijie Xia a , Erjie Yang a , Mengnan Zhang a , Yusong Wang b , Youxin Ji a, c , Wei Chen a, * , Daoliang Wang a , Lingpu Meng a , Liangbin Li a a National Synchrotron Radiation Laboratory, Anhui Provincial Engineering Laboratory of Advanced Functional Polymer Film, CAS Key Laboratory of Soft Matter Chemistry, University of Science and Technology of China, Hefei, 230026, China b Hefei National Laboratory for Physical Sciences at the Microscale, University of Science and Technology of China, Hefei, 230026, China c School of Materials Science and Engineering, The Key Laboratory of Materials Processing and Mold, Ministry of Education, Henan Key Laboratory of Advanced Nylon Materials and Application, Zhengzhou University, Zhengzhou, 450001, China A R T I C L E INFO Keywords: Film blowing Polyethylene Crystallization Structure-process-property relationship Synchrotron radiation X-ray scattering ABSTRACT The copolymerization of ethylene and different α-olefns could result in polyethylene (PE) with different structural topologies, and lead to polyethylene products with different macroscopic performances. Herein, three different polyethylene samples, namely low-density polyethylene (l-PE), metallocene catalyzed ethylene-hexene copolymer (h-PE) and ethylene-octene copolymer (o-PE), were selected as representatives to construct the structure-process-property relationship during flm blowing. The detailed crystal-based network evolution during flm blowing was frst characterized by in-situ synchrotron radiation X-ray scattering. The crystallization process of l-PE flm is determined by the coupling effects of temperature and fow, while those of h-PE and o-PE flms are dominated by the temperature. Furthermore, the hierarchical crystal structure from the molecular scale to mi- crometers of fnal flms and segmental dynamics were systematically characterized by multiple ex-situ charac- terization techniques, i.e. Solid-State NMR, FTIR, SEM. l-PE flm shows the crystalline morphology of the row- nucleated structure, whereas h-PE and o-PE show spherulite-like superstructure with better mechanical prop- erties. The current study tentatively constructs the relation of primary chemical structure, microstructural evolution and macroscopic performances of different polyethylene copolymers during flm blowing. 1. Introduction As one of the most important processing technologies, the flm blowing has gained worldwide attention since its beginning in the 1930s [1]. The general flm blowing process is intuitively shown in Fig. 1a. The polymer pellets are fully melted and plasticized by the screw at the very beginning, and then extruded from the annular die with an extruded velocity v e . From the annular melt to the tubular flm, the melt un- dergoes the take-up forces from the nip rolls (the take-up velocity v t ), circumferential extension from the air pressure difference between in- side and outside of bubble (ΔP), and fast cooling from the cooling air. Therefore, the crystallization process during flm blowing is intrinsically complicated with the coupling of fast cooling and multi-dimensional fow feld [2–5]. It is of great importance, but also a great challenge in polymer physics to elucidate the relationships of structure-process-property during flm blowing. During the flm blowing, the multi-scale microstructural evolution of bubble is highly related to the structural topology of the primary mo- lecular chain, which in turn determines the macroscopic properties of fnal flms [6–9]. Polyethylene (PE) is a material commonly used for flm blowing processing in various felds such as mulching flms, greenhouse flms, carrier bags, and packaging applications [10–12]. Different polyethylene flms can be obtained by changing the type of α-olefn comonomer to obtain specifc properties [13–16]. The crystal structure of polyethylene blown flms have been extensively studied based on the row-nucleated model of Keller and Machin since the 1950s [17]. In this model, the direction of the crystal growth is parallel to the b-axis. A vast of results indicate that low-density polyethylene (LDPE) and linear * Corresponding author. E-mail address: wc003@ustc.edu.cn (W. Chen). Contents lists available at ScienceDirect Polymer Testing journal homepage: http://www.elsevier.com/locate/polytest https://doi.org/10.1016/j.polymertesting.2020.106439 Received 16 October 2019; Received in revised form 11 January 2020; Accepted 14 February 2020