Influences of aminosilanization of halloysite nanotubes on the mechanical properties of polyamide‐6 nanocomposites

The main purpose of this study was to explore effects of silanization of halloysite nanotubes (HNT) on the mechanical properties of polyamide 6 by using aminopropyltriethoxysilane. Effects of two silanization parameters; “initial silane concentration” and “pH of reaction solution” were also investigated. Nanocomposites were compounded via melt mixing method in a twin‐screw extruder, while specimens were shaped by injection molding. Formation of aminosilane molecules on the edges and defected surfaces of HNTs were revealed mainly by Fourier‐Transform infrared spectroscopy. Scanning electron microscopy and mechanical tests indicated that even the use of unmodified HNTs could be homogenously distributed in the matrix leading to increased mechanical properties as much as more than 30%. Aminosilanization of HNTs with optimum silanization parameters resulted in effective amounts of Al O Si bridging bonds between the matrix and reinforcement, making composite strengthening mechanisms more operative. In this condition, increases in the mechanical properties were as much as more than 50%. POLYM. COMPOS., 35:1350–1361, 2014. © 2013 Society of Plastics Engineers     

The proximate composition and some minor constituents of poppy seeds

The proximate chemical composition of poppy seeds, along with minerals and water-soluble vitamins content was investigated. The compositions of the fatty acids and tocopherols of the extracted oil were also determined. The proximate analysis of poppy seeds showed the following composition: (440 g kg^?1), protein (211 g kg^?1), moisture (50 g kg^?1), ash (63 g kg^?1), crude fine (62 g kg^?1) and total carbohydrates (236 g kg^?1). Potassium and calcium were the predominant elements in the poppy seeds. Linoleic acid was the major unsaturated fatty acid (750 g kg^?1 total fatty acids) while palmitic acid was the main saturated one (86-4 g kg^?1). The amounts of α-, β- and δ-tocopherols found in poppy seed oil were 220 μg g^?1, 40 μg g^?1 and 20 μg g^?1 respectively. Among the water-soluble vitamins determined, pantothenic acid was found at the highest level followed by niacin and thiamin.     

Fire retardant properties of intumescent polypropylene composites filled with calcium carbonate

This study was aimed to investigate the influence of calcium carbonate (CaCO₃), a widely used filler, on the fire retardancy of intumescent polypropylene composites. Two intumescent systems based on (1) mixture of ammonium polyphosphate (APP) and pentaerythritol and (2) surface‐modified APP (m‐APP) were examined. In terms of steady heat release rate, total heat evolved, and fire growth index determined by mass loss calorimetry, m‐APP performed markedly superior to APP‐pentaerythritol. The presence of CaCO₃ in both intumescent formulations caused significant losses in fire retardant performance assessed by mass loss calorimetry, limiting oxygen index and UL‐94 tests. Peak rates of heat release and mass loss during combustion, and total heat evolved on combustion were increased, whereas time to ignition was decreased. Characterization of fire residues ascribed the mechanism of deterioration in fire retardancy to the formation of porous and nonexpanded crystalline calcium phosphate/CaCO₃ residues during combustion rather than the amorphous protective intumescent chars formed in the absence of CaCO₃. POLYM. ENG. SCI., 2011. © 2011 Society of Plastics Engineers     

Block copolymers by combinations of cationic and radical routes

Summary A new method is described for the production of macroporous beads by copolymerization of styrene and divinylbenzene initiated by azo linked polytetrahydrofuran, which was obtained by silver salt-diacid chloride technique. Swelling properties of the beads in various solvents were studied.     

Strength of short fiber reinforced polymers: Effect of fiber length distribution

In this study, the prediction of mechanical strength of short fiber reinforced plastics (SFRPs) is made possible by obtaining a Fiber Length Distribution (FLD) efficiency factor, η_FLD, from the formerly known twofold discrete strengthening equation of Kelly–Tyson. The unified parameter η_FLD is developed involving both the effects of fiber breakage and resulting distribution, fiber volume fraction and fiber and interface properties, so that they can be incorporated into modified rule of mixtures (MROM). This procedure helps to clarify the experimentally observed loss in strengthening rate with increasing fiber fraction. By adapting a few experimentally determined distributions to a Weibull type function, the analytical solutions described in this study establish the exploration of the strength of SFRPs in the entire fiber content range or can reveal the interfacial bond strength. After investigating the effects of fiber and interface parameters on strengthening efficiency, it is found that common fiber‐matrix combinations possessing intermediate critical fiber lengths show a significant decrease in strengthening efficiency with increasing fiber content at low fiber loadings. On the contrary, higher and lower critical fiber lengths yield less significant losses. POLYM. COMPOS., 2008. © 2008 Society of Plastics Engineers     

An improvement in the calculation of the magnetic field for an arbitrary geometry coil with rectangular cross section Int. J. Numer. Model. 2005; 18(6):493–504

The above article was published in Volume 18, Issue 6, Pages 493–504, (October 2005). A number of imperfections were subsequently identified and have been corrected below. On page 497, the following equation has been corrected to: On page 501, the following equation has been corrected to: On page 502, the following equation has been corrected to:      

Efficient parallel spatial subdivision algorithm for object-based parallel ray tracing

Parallel ray tracing of complex scenes on multicomputers requires the distribution of both computation and scene data to the processors. This is carried out during preprocessing and usually consumes too much time and memory. The paper presents an efficient parallel subdivision algorithm that decomposes a given scene into rectangular regions adaptively and maps the resultant regions to the node processors of a multicomputer. The proposed algorithm uses efficient data structures to identify the splitting planes quickly. Furthermore the mapping of the regions and the objects to the node processors is performed while parallel spatial subdivision proceeds. The proposed algorithm is implemented on an Intel iPSC/2 hypercube multicomputer and promising results have been obtained.     

Multi-level direct K-way hypergraph partitioning with multiple constraints and fixed vertices

K$K$-way hypergraph partitioning has an ever-growing use in parallelization of scientific computing applications. We claim that hypergraph partitioning with multiple constraints and fixed vertices should be implemented using direct K$K$-way refinement, instead of the widely adopted recursive bisection paradigm. Our arguments are based on the fact that recursive-bisection-based partitioning algorithms perform considerably worse when used in the multiple constraint and fixed vertex formulations. We discuss possible reasons for this performance degradation. We describe a careful implementation of a multi-level direct K$K$-way hypergraph partitioning algorithm, which performs better than a well-known recursive-bisection-based partitioning algorithm in hypergraph partitioning with multiple constraints and fixed vertices. We also experimentally show that the proposed algorithm is effective in standard hypergraph partitioning.     

The effects of surface roughness on varnish adhesion strength of wood materials

In this study, the effects of surface roughness of wood material on the adhesion strength of varnish layers have been tested. For this purpose, test samples of beech (Fagus orientalis L.), Scots pine (Pinus sylvestris L.), and cherry (Prunus cerasus) wood species were prepared and sanded with 80, 120, and 180 grit abrasives. The surface roughness values of specimens were determined using a stylus-type profilometer TIME TR 200 according to the ISO 4287 standards. Then, water-based, polyurethane, and acrylic varnish were applied to the surfaces of the samples in accordance with ASTM-D 3023. Layer adhesion strength was determined to the TS EN ISO 4624 standards. As a result, the highest adhesion strength value (2.52 N/mm²) was found in cherry, while the Scots pine had the lowest value (2.32 N/mm²). For the varnish types, polyurethane varnish types gave the highest value (3.15 N/mm²), while the lowest value was obtained from the water-based varnish. Looking at interactions between adhesion strength and surface roughness, the water-based varnish had the strongest correlation with adhesion strength (69%) and acrylic varnish also had a similar result (67%), while polyurethane varnish had the weakest result (33%) in this interaction.