Papers by Keyword: Dynamic Mechanical Thermal Analysis

Abstract: Laminated glass is a structural element used extensively in a reconstruction of existing building structures because of its transparency and simplicity. When using laminated glass as a glass staircase, balustrades, transparent flooring, facades or other structural elements, it is advisable to consider the shear interaction of individual glass panes in the cross-section. A conservative approach where the glass panes shear interaction is not considered, is uneconomical. This interaction depends on the properties of polymeric interlayers used in lamination process. Various commercial products based on PVB (polyvinyl butyral), EVA (ethylene vinyl acetate), ionomer, or thermoplastic polyurethane (TPU) are used. Stiffness of polymers depends on temperature and duration of a load. Interlayers exhibit the viscoelastic properties and temperature dependency usually described by the generalized Maxwell model and WLF model (Williams-Landel-Ferry). Parameters of these models are the most effectively determined by Dynamic Mechanical Thermal Analysis (DMTA), where the material is cyclically loaded at different frequencies and temperatures. Material parameters were found by DMTA in shear for PVB type of interlayer Trosifol® BG R20. In addition, the experimental quasi-static loading tests in shear were performed at different loading rates and at various temperatures. These experimental stress-strain diagrams were compared to the theoretical stress-strain relations obtained from Maxwell model with material parameters based on DMTA testing. All tests were performed in Klokner Institute CTU in Prague.

Abstract: The increasing environmental issues has resulted in the trend of the use of renewable or natural source (green) fillers in the polymer composites fabrication. Among these green fillers is called natural fibers or plant fibers. One particular plant fibers that became the topic of the present work is date palm fiber (DPF). In the present work, DPF at different loadings (i.e. 0, 5, 10, 20, 30 wt%) were incorporated (as fillers) in the high density polyethylene (HDPE) matrix to fabricate HDPE/DPF composites. Further, we have investigated the effect of DPF loadings on the dynamic mechanical thermal properties of the composites. The dynamic mechanical thermal analysis (DMTA) results exhibited that the storage modulus of the composites increased with increasing DPF loadings. Additionally, all the storage modulus values of the composites were higher than the neat HDPE in all temperature ranges. For example, at temperature of 60°C, the storage modulus enhancement of the composites as compared to the neat HDPE were about 26, 76, 134, and 225% for 5, 10, 20, 30 wt% of DPF loadings, respectively. Additionally, the relationship between the DPF loadings (wt%) and temperature (°C) on the storage modulus of the HDPE/DPF composites was modeled using a logarithmic equation. Based on the data plotting between the experimental data and modeled data, the logarithmic equation was found to be fitted with the experimental data satisfactory.

Abstract: The ionic conductivity and mechanical properties of poly (vinyl chloride) (PVC)/poly (ethyl methacrylate) (PEMA) polymer blends containing LiN(CF3SO3)2 as doping salt has been studied using electrical impedance spectroscopy (EIS) and Dynamic Modulus Analysis (DMA) as a function of polymer blend ratios and lithium salt concentration. The film with PVC/PEMA composition of 65:35 obtained the highest conductivity with good transparency. DMA showed that both the storage modulus (E') and the glass transition temperature (Tg) of the PVC/PEMA is increased with PEMA concentration. In the case of PVC/PEMA-LiN(CF3SO2)2 films, the conductivity was found to increase with concentration of salt added with a maximum in conductivity at 35 wt.% LiN(CF3SO2)2. The Tg values of the doped films was found to increase with concentration of salt such that the film with the highest conductivity value has the highest Tg.

Abstract: Conventional mechanical and structural properties allow to describe the complete composite material. They do, however, not describe the reaction during the pyrolysis process. The dynamic mechanical thermal analysis (DMTA) is a technique which is used to characterize materials. In particular, the DMTA method is used to observe the viscoelastic nature of polymers. Another interesting application area of the DMTA is the simulation of pyrolysis experiments to obtain carbon/carbon composites (C/C composites). The pyrolysis process of carbon-fibre-reinforced plastics (CFRP) was performed by means of inert gas (Ar, ambient pressure) under a defined time-temperature profile or alternatively approached by short time sweeps in a DMTA. So the temperature dependence of the elastic modulus (E-modulus) and of the internal damping (tan δ) are determined starting from the cured carbon-fibre-reinforced plastic to the transformed C/C composites. The analyses were applied for different matrix resins. The shown method improves the access to usually hidden mechanical and structural properties and requires further investigation of the entire polymerization and pyrolysis processes.

Abstract: This work reports the effects of nanoclays and aluminium hydroxide (ATH) on the thermomechanical properties of an unsaturated polyester resin. Dynamic mechanical thermal analysis in the temperature range from 25 to 150 °C has indicated the formation of different structures for the different clay (1, 5 and 10 wt. %) and ATH loadings (50 and 100 wt. %) investigated. The rubbery modulus increases with nanoclay and ATH content which indicates that both nanoclays and ATH act positively on the final network density and consequently lead to systems showing higher stiffness at higher temperatures. The mechanical loss peak value decreases with either nanoclay or ATH content which seems to indicate that both nanoclays and ATH improve network density. The glass transition temperature and the mechanical loss peak value changes linearly with ATH content.

Abstract: Resin matrixes for aeronautic advanced composites based on thermoplastic PEK-C (modified polyetherketone) and blending epoxies of DGEBA (diglycidyl ether of bisphenol A) and TGMDA (tetraglycidyl methylenedianiline) are analyzed by DMTA in this paper. The effects of blending ratios and high-temperature post-curing processes on DMTA properties are investigated. The results show that epoxies exhibit different curing features with the existence of high viscous thermoplastic, by contrarily the neat epoxies systems cure according to a random copolymerization rule. The primary peak of tangent delta of DMTA mainly attributes to segment motions of thermoplastic in a blend and the secondary peak mainly for those of the DGEBA cured networks. The higher the ratio of TGMDA to DGEBA is the more obviously the separation degree of tangent delta peaks adopt. Increasing the amount of TGMDA is helpful for separating of phases in the blends. High temperature post-curing promotes separating of phases. In a blend the continuous phase mainly consists of a mass of thermoplastic and some TGMDA, DGEBA mainly collects in dispersed phases.