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- ItemCarboxylated nitrile butadiene rubber/hybrid filler composites(São Carlos : Universidade Federal de São Carlos, 2012) Mousa, A.; Heinrich, G.; Simon, F.; Wagenknecht, U.; Stöckelhuber, K.-W.; Dweiri, R.The surface properties of the OSW and NLS are measured with the dynamic contact-angle technique. The x-ray photoelectron spectroscopy (XPS) of the OSW reveals that the OSW possesses various reactive functional groups namely hydroxyl groups (OH). Hybrid filler from NLS and OSW were incorporated into carboxylated nitrile rubber (XNBR) to produce XNBR hybrid composites. The reaction of OH groups from the OSW with COOH of the XNBR is checked by attenuated total reflectance spectra (ATR-IR) of the composites. The degree of curing ΔM (maximum torque-minimum torque) as a function of hybrid filler as derived from moving die rheometer (MDR) is reported. The stress-strain behavior of the hybrid composites as well as the dynamic mechanical thermal analysis (DMTA) is studied. Bonding quality and dispersion of the hybrid filler with and in XNBR are examined using scanning-transmission electron microscopy (STEM in SEM).
- ItemA numerical study on deformation of Newtonian droplets through converging cylindrical dies(Berlin : de Gruyter, 2013) Mostafaiyan, M.; Saeb, M.R.; Ahmadi, Z.; Khonakdar, H.A.; Wagenknecht, U.; Heinrich, G.In this work, the dynamic deformation of a viscose Newtonian droplet passing through cylindrical converging dies has been studied. The changes in the interfacial area between two immiscible Newtonian fluids have been considered as a variable representing the time-dependent deformation of a circular droplet along converging dies. To do so, a surface tracking method has been incorporated into a finite element code, developed by the authors, which quantifies the deformation of the droplet through the converging path, and where the surface area of the deformed drop has been consequently chosen as a criterion for a two-phase interface. In this study, it has been revealed that by changing both rheological and geometrical parameters it is possible to manage the value of interface area between two phases. Ultimately, a unique curve is developed for each droplet to primary phase viscosity ratio which can correlate drop deformation with geometrical parameters.
- ItemUtilization of agrowaste polymers in PVC/NBR alloys: Tensile, thermal, and morphological properties(New York, NY : Hindawi, 2012) Mousa, A.; Heinrich, G.; Kretzschmar, B.; Wagenknecht, U.; Das, A.Poly(vinyl chloride)/nitrile butadiene rubber (PVC/NBR) alloys were melt-mixed using a Brabender Plasticorder at 180 °C and 50rpm rotor speed. Alloys obtained by melt mixing from PVC and NBR were formulated with wood-flour- (WF-) based olive residue, a natural byproduct from olive oil extraction industry. WF was progressively increased from 0 to 30phr. The effects of WF loadings on the tensile properties of the fabricated samples were inspected. The torque rheometry, which is an indirect indication of the melt strength, is reported. The pattern of water uptake for the composites was checked as a function WF loading. The fracture mode and the quality of bonding of the alloy with and without filler are studied using electron scanning microscope (SEM).
- ItemInvestigation of laser irradiated areas with electron backscatter diffraction(Amsterdam [u.a.] : Elsevier, 2012) Heinrich, G.; Höger, I.; Bähr, M.; Stolberg, K.; Wütherich, T.; Leonhardt, M.; Lawerenz, A.; Gobsch, G.In this work, two silicon nitride (SiNx) layers with two different refraction indices, deposited on polished or damageetched silicon wafers were locally irradiated by laser pulses. The focus was set on the investigation of the ablation mechanisms. Thereby, an ultra-short laser source (pulse duration 10 ps, wavelength 532 nm, Gaussian profile) was used. The irradiated areas were investigated by electron backscatter diffraction (EBSD) in order to analyze the nearsurface crystallographic orientation and crystallinity. In this work an indirect ablation was observed for SiN x (n = 1.9). Further, a change from an indirect ablation to a partial lift-off for SiNx (n = 2.1) was determined to be fluence dependent. At low fluences, the SiNx was completely removed. However, at higher fluences, SiNx was not completely removed, due to direct ablation. The two-photonabsorption coefficient of SiNx (n = 2.1) was estimated to be 2·105 cm/TW.
- ItemCure kinetics of epoxy nanocomposites affected by MWCNTs functionalization: A review(Boynton Beach, Fla. : Hindawi, 2013) Saeb, M.R.; Bakhshandeh, E.; Khonakdar, H.A.; Mäder, E.; Scheffler, C.; Heinrich, G.The current paper provides an overview to emphasize the role of functionalization of multiwalled carbon nanotubes (MWCNTs) in manipulating cure kinetics of epoxy nanocomposites, which itself determines ultimate properties of the resulting compound. In this regard, the most commonly used functionalization schemes, that is, carboxylation and amidation, are thoroughly surveyed to highlight the role of functionalized nanotubes in controlling the rate of autocatalytic and vitrification kinetics. The current literature elucidates that the mechanism of curing in epoxy/MWCNTs nanocomposites remains almost unaffected by the functionalization of carbon nanotubes. On the other hand, early stage facilitation of autocatalytic reactions in the presence of MWCNTs bearing amine groups has been addressed by several researchers. When carboxylated nanotubes were used to modify MWCNTs, the rate of such reactions diminished as a consequence of heterogeneous dispersion within the epoxy matrix. At later stages of curing, however, the prolonged vitrification was seen to be dominant. Thus, the type of functional groups covalently located on the surface of MWCNTs directly affects the degree of polymer-nanotube interaction followed by enhancement of curing reaction. Our survey demonstrated that most widespread efforts ever made to represent multifarious surface-treated MWCNTs have not been directed towards preparation of epoxy nanocomposites, but they could result in property synergism.