Stiren-Etilen/Butilen-Stiren Blok Kopolimeri Esaslı Nanokompozitlerin Hazırlanması ve Modifikasyonu

Abstract

In recent years, increases are observed the use of thermoplastic elastomers instead of thermoset rubbers. Thermoplastic elastomers (TPE) are defined as rubber like materials which can be processed and recyclable, because they have melting points like thermoplastic polymers. Processability and recyclable is not possible for rubbers which obtained as a result of vulcanization. The aim of this study is to investigate the properties of polymers which gained by using modified additives and obtained styrene-ethylene/butylene-styrene (SEBS) block copolymer based composite materials which are prepared with modified clays using cationic monomers. Also, it is investigated to availability of our modified clay by comparison composite materials which are prepared by commercial modified clays according to the composite materials which are prepared by our modified clays. Since the SEBS block copolymer is difficult to process alone, it is possible to prepare the blends with polypropylene (PP) and paraffinic oil (PO) to improve the processability. Firstly, SEBS/PP/PO mixtures were prepared in different ratios. According to the mechanical test results of these mixtures, the most appropriate ratio was determined and the main matrix to be used in the continuation of the study was decided. Mixtures of the master matrix with different modified clays were prepared and their effects on the mechanical and thermal properties of the additives were observed. All mixtures were prepared by melt blending method using twin screw mixer. SEBS block copolymer containing 32% by mass of styrene were used as polymer, PP and oil were used to increase the processability in the prepared composite materials. Pure clay montmorillonite (MMT), commercial modified clays and modified clays which are prepared by cationic monomers were used as additives. Firstly, MMT was interacted with [2- (methacryloxy) ethyl] -trimethylammonium chloride (METMAC) and [3- (methacryloamino) -propyl] -trimethylammonium chloride (MPTMAC) in the presence of water and the monomers were deposited between the layers of the clay as a result of the ion exchange reaction. Then, these mixtures were polymerized at different times by thermal polymerization method in the presence of initiator to provide modification of the layered structure. As a result of X-ray diffraction (XRD) analysis, the distances between the layers were calculated by using Bragg equation. The structural characterization of the prepared composite materials was done by XRD and transmission electron microscope (TEM). The distrubition of modified layered structure was investigated with XRD in the polymer matrix and the distances between the layers were calculated. According to the obtained results, the samples prepared with commercially modified clays are intercalated structure, the samples prepared with modified clays using cationic monomers were found to have both intercalated structure and exfoliated structure. These results were supported by images obtained from TEM analysis. The change in the free volume holes of the polymer as a result of the distribution of the clay within the matrix was investigated by PALS measurements. According to the results, more compact structure were formed and decreasing were seen in the free volume holes with increasing interaction between matrix and modified clay layers. The effect of the additives on SEBS block copolymer was investigated by performing mechanical test of prepared materials. According to the results, the mechanical values of the composite samples prepared by our modified clays were found to give better results than the samples prepared with commercial modified clays. When the thermal behavior of the same samples were examined, the degradation of the modified clay doped materials was obtained at higher temperatures.