Structure of the in situ produced polyethylene based composites modified with multi-walled carbon nanotubes: In situ synchrotron X-ray diffraction and differential scanning calorimetry study

• Published in: Composites science and technology Vol. 167; pp. 148 - 154
• Main Authors: Kazakova, Mariya A., Selyutin, Alexander G., Semikolenova, Nina V., Ishchenko, Arcady V., Moseenkov, Sergey I., Matsko, Mikhail A., Zakharov, Vladimir A., Kuznetsov, Vladimir L.
• Format: Journal Article
• Language: English
• Published: Barking Elsevier Ltd 20-10-2018; Elsevier BV
• Subjects: Catalysis; Catalysts; Coherent scattering; Comparative studies; Composite materials; Composite structures; Crystallization; Differential scanning calorimetry; Dynamic models; Heat measurement; In situ polymerization; In situ synchrotron X-ray diffraction; Molecular dynamics; Multi wall carbon nanotubes; Multi-walled carbon nanotubes; Nanotubes; Nucleation; Particulate composites; Polyethylene; Polyethylene composites; Polyethylenes; Polymer crystallization; Polymer matrix composites; Polymerization; Scanning electron microscopy; Synchrotron radiation; X-ray diffraction; Ziegler-Natta catalysts; Polyethylene composites; In situ polymerization; Multi-walled carbon nanotubes; In situ synchrotron X-ray diffraction; Polymer crystallization
• ISSN: 0266-3538; 1879-1050
• DOI: 10.1016/j.compscitech.2018.07.046

Polyethylene based composites modified with multi-walled carbon nanotubes (MWCNTs) were produced via in situ polymerization of ethylene with the Ti-Ziegler–Natta catalyst preliminarily immobilized on MWCNTs. The composite structure was characterized with transmission and scanning electron microscopy, differential scanning calorimetry (DSC) and in situ synchrotron X-ray Diffraction (in situ XRD). For the first time the Ti-containing catalyst species of the size 2–3 nm were observed on the MWСNTs surface stabilized in the polymer matrix. A comparative study of the melting-crystallization cycles of neat polyethylene (PE) and MWCNT-PE composites with in situ XRD and DSC provide information on the nucleation of PE crystals. For the first time, the in situ XRD technique was used for estimation of the coherent scattering region of PE blocks during the melting-crystallization cycles. These experiments and molecular dynamic modeling showed that MWCNTs act as the template for the PE chain orientation and as the nucleating agent for PE crystallization. However, the nucleation of PE crystals in composites occurs on the nanotube surface and also within the space between nanotubes. Thus, the relative volume of PE nucleated on nanotubes depends on their content in the composite and can be significant only for the composites with high nanotube loading.