Polypropylene composite with carbon nanotubes

Features of thermal breakdown and burning of a nanocomposite based on polypropylene and multiwalled carbon nanotubes are studied. A kinetic model is proposed on the basis on the TGA results, taking account of the diffusion nature of polypropylene nanocomposite thermal breakdown. The main parameters of nanocomposite inflammability are determined using a cone-calorimeter. Currently more attention is being devoted in the world to studying the properties of polymer nanocomposites based on well-known thermoplastics, i.e., polypropylene (PP), polyethylene (PE), polystyrene (PS), polymethylmethacrylate (PMMA), polycarbonates, polyamides, and carbon nanotubes (CNT), exhibiting heat resistance, reduced inflammability, electrical conductivity, and other properties. As a rule, nanocomposites of thermoplastic polymers based on CNT are prepared using melting technology. The aim of this study is to develop a procedure for preparing and studying the thermal characteristics of nanocomposites based on PP and multiwalled carbon nanotubes (MCNT). Among the world publications there are a number of works devoted to synthesizing and studying the thermal properties of nanocomposites of atactic polypropylene (aPP) and MCNT. In the majority of research, an increase is noted in the thermal and thermal-oxidation stability of PP-MCNT nanocomposites, achieved as a result of introducing insignificant amounts of nanocarbon filler of 1‐5 wt.%. Study Objects and Materials. The polymer matrix used was isostatic PP (Moscow Oil Processing Plant) with a melt flow index (MFI) of 0.7 g/10 min. The carbon-containing nanofiller used was industrial MCNT prepared by a pyrolytic method [Shenzen Nanotechnologies Co. Ltd. (NTP), CPR]. This product has a low amorphous carbon content and controlled particle sizes, i.e., different diameter D, length L, and characteristic ratio L/D. The characteristics of three types of multiwalled carbon nanotubes are provided in Table 1. The dimensions and structure of the original nanotubes were additionally evaluated by means of scanning (SEM) and transmission (TEM) electron microscopy. The microphotographs obtained are provided in Figs. 1 and 2, respectively. Nanocomposites Preparation. Composites were prepared by mixing polymer and nanotubes in a melt in a laboratory two-rotor mixer in the presence of thermal oxidation stabilizers for polymer breakdown at 190°C (for PP) and a rotor rotation rate of 90 rpm. The stabilizers used for thermal oxidation breakdown of polymer under composite preparation conditions in a melt, processing and operation, were 1,1,3-tris-(6’-methyl-3’-tret-butyl-4’-oxyphenyl)-butane, or topanol (in an