Interfacial,dynamic mechanical,and thermal fiber reinforced behavior of MAPE treated sisal fiber reinforced HDPE composites

The present article summarizes an experimental study on the mechanical and dynamic mechanical behavior of sisal fiber reinforced HDPE composites. Variations in mechanical strength, storage modulus (E′), loss modulus (E″), and damping parameter (tan δ) with the addition of fibers and coupling agents were investigated. It was observed that the tensile, flexural, and impact strengths increased with the increase in fiber loading up to 30%, above which there was a significant deterioration in the mechanical strength. Further, the composites treated with MAPE showed improved properties in comparison with the untreated composites. Dynamic mechanical analysis data also showed an increase in the storage modulus of the treated composites The tan δ spectra presented a strong influence of fiber content and coupling agent on the α and γ relaxation process of HDPE. The thermal behavior of the composites was evaluated from TGA/DTG thermograms. The fiber–matrix morphology in the treated composites was confirmed by SEM analysis of the tensile fractured specimens. FTIR spectra of the treated and untreated composites were also studied, to ascertain the existence of type of interfacial bonds. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 3306–3315, 2006     

Dropwise Condensation Studies on Multiple Scales

Recent advances in nanotechnology, chemical/physical texturing and thin film coating technology generate definite possibilities for sustaining a dropwise mode of condensation for much longer durations than was previously possible. The availability of superior experimental techniques also leads to deeper understanding of the process parameters controlling the relevant transport phenomena, the distinguishing feature of which is the involvement of a hierarchy of length/time scales, proceeding from nuclei formation, to clusters, all the way to macroscopic droplet ensemble, drop coalescence, and subsequent dynamics. This paper is an attempt to connect and present a holistic framework of modeling and studying dropwise condensation at these multiple scales. After a review of the literature, discussions on the following problems are presented: (i) atomistic modeling of nucleation; (ii) droplet–substrate interaction; (iii) surface preparation; (iv) simulation of fluid motion inside sliding drops; (v) experimental determination of the local/ average heat transfer coefficient; and (vi) a macroscopic model of the complete dropwise condensation process underneath horizontal and inclined surfaces. The study indicates that hierarchal modeling is indeed the way forward to capture the complete process dynamics. The microscopic phenomena at the three-phase contact line, leading to the apparent droplet contact angle, influence the shear stress and heat transfer. The nucleation theory captures the quasi-steady-state behavior quite satisfactorily, although the early atomistic nucleation was not seen to have a profound bearing on the steady-state behavior. The latter is strongly governed by the coalescence dynamics. Visual observation of dropwise condensation provides important information for building hierarchical models.     

Effect of Organoclays on Nonisothermal Crystallization Kinetics of Poly (trimethylene terephthalate) Nanocomposite

Non-isothermal crystallization kinetics, melting behavior of virgin PTT and PTT nanocomposites were investigated using differential scanning calorimetry with the Avrami equation. Mechanical properties of PTT/clay nanocomposite is also described with Einstien and Guth model. The rate of crystallization and half time required for crystallization increases with increasing the cooling rate for both virgin PTT and PTT/clay nanocomposites. Virgin PTT shows the double melting behavior which changes to single melting point in prances of C30B nanoclays in the case of PTT/C30B nanocomposites. Incorporation of loading of organoclays increases the activation energy (E_a) in PTT matrix and optimum E_a was observed in PTT/C30B-based system.     

Robust rumor blocking problem with uncertain rumor sources in social networks

World Wide Web - Rumormongers spread negative information throughout the social network, which may even lead to panic or unrest. Rumor should be blocked by spreading positive information from...     

Sustainability Assessment and Machinability Investigation of Austenitic Stainless Steel in Finish Turning with Advanced Ultra-Hard SiAlON Ceramic Tool under Different Cutting Environments

Silicon - This paper presents the evaluation of the performances of the various cooling-lubrication techniques (dry, compressed-air cooled, flooded and minimum quantity lubrication) applied in...     

Mechanical Behavior of Castor-Oil-Based Advanced Polyurethane Functionalized with Glycidol and Siloxanes

Castor-oil-based polyurethane (PU), epoxy (glycidol) terminated polyurethane (EPU), and hydroxy terminated poly (dimethyl siloxane) (HTPDMS) modified EPU (EPDMS) were synthesized. The PU and EPU were synthesized with polyol:diisocyanate and polyol:diisocyanate:glycidol ratio of 1:1.2 and 1:3:3, respectively, whereas EPDMS was prepared by the incorporation of 5 wt.%, 10 wt.%, 20 wt.%, and 30 wt.% of HTPDMS into the EPU. The structural modification of EPDMS was confirmed by solid-state CP/MAS ¹³C and ²⁹Si NMR spectroscopy. The results of a tensile test revealed that the EPDMS with 10 wt.% loading of HTPDMS (EPDMS10) exhibited considerable enhancement in the tensile strength and modulus. The scanning electron microscope analysis was performed to understand the increased phase heterogeneity of the samples.     

Damage tolerance behaviour of cloisite 15A incorporated recycled polypropylene nanocomposites and bionanocomposites

In the present investigation, recycled polypropylene (rPP) used as a matrix was modified by incorporating nanofillers through melt blending technique to prepare a masterbatch of nanocomposites. Untreated sisal fibre and mercerised sisal fibres were further incorporated into the nanocomposites for the preparation of bionanocomposites. Bionanocomposites containing 40 wt% of UT fibre and 5 wt% of MA-g-PP revealed an increase in the tensile strength and modulus to the tune of 27% and 370%, respectively, compared to rPP. The flexural strength and modulus also increased to the tune of 129% and 269%, respectively, compared to rPP. Further, the surface treatment of the fibre slightly increased the mechanical properties and stiffness of bionanocomposites. Interfacial strength between fibre and matrix was also evaluated by using Turcsanyi and Sato–Furukawa models. Damage tolerance of rPP nanocomposites and its bionanocomposites was evaluated using single-edge-notch specimens. The notch length ‘a’ to width ‘W’ ratios, a/W, were chosen as 0.3, 0.45 and 0.6. The nanocomposites showed better damage tolerance as compared to the rPP matrix. The corrugated structure with increased fractured surface area was observed in scanning electron microscopy. Better dispersion of clay in the nanocomposites was observed in transmission electron microscopy.     

Effect of feature spacing when injection molding parts with microstructured surfaces

The effects of microfeature spacing on the replication of thermoplastic elastomer features was investigated using micropillars with two diameters (10 μ m and 20 μ m) and three spacing ratios (0.5:1, 1:1, and 2:1). The tooling and part features were characterized for feature depth and height as well as feature definition using scanning electron microscopy and optical profilometry. Filling simulations provided insight into the process. Feature spacing significantly affected the replication of micropillars using a thermoplastic elastomer. This replication was competition between pressurization, relaxation, and cooling of the melt. Higher pressures generally improved feature replication, but did not always create perfect replication. Relaxation of the highly aligned polymer chains and cooling effects restricted filling, tended to reduce feature height, and increase feature diameters. POLYM. ENG. SCI., 56:1330–1338, 2016. © 2016 Society of Plastics Engineers     

Polypropylene–nano‐silica nanocomposite foams: mechanisms underlying foamability,and foam microstructure,crystallinity and mechanical properties

We investigate the production and characterization of foams prepared from polypropylene (PP) as well as PP–silica nanocomposites containing different loadings of nano‐silica. This study was carried out to investigate the mechanisms underlying the production of foams with a regular cell structure through the use of nano‐scale fillers. Foaming was carried out in batch mode using an autoclave with CO₂ as the physical blowing agent; high pressures of the order of 14 MPa were achieved through a combination of active pressurization and the use of high foaming temperatures. The resulting PP nanocomposite foams were characterized in detail to quantify the effect of the nano‐silica loading on the foam density and mechanical, morphological and thermal properties. The addition of nano‐silica in PP resulted in the improvement of foam quality – as assessed from the well‐defined and regular cell structures with absence of cell coalescence – as well as an increase in expansion ratio and decrease in foam density. Careful analyses of trends in cell size, cell density and expansion ratio of the foams were correlated with measurements of melt rheology and nano‐filler morphology of the unfoamed specimens in order to identify subtle details regarding the role of silica nanoparticles in improving foam quality. © 2019 Society of Chemical Industry