Svetlana Butylina

Retention of pegs in cross-flow ultrafiltration through membranes☆

Abstract This work investigated the difference between membrane cut-offs measured with the CHARMME methods and the values quoted from the manufacturers. Four different membranes were characterised. The two regenerated cellulose membranes that according to the manufacturers had cut-offs of 5 and 10 kD had, in fact, the same cut-off of 2.5 kD. It was also found that the polyethersulfone membrane had a lower cut-off (3 kD) than that stated by the membrane manufacturers (5 kD). A cross-flow velocity of 2 m/s and a flux of 40 l/h/m2 was found to keep the mass transfer coefficient within a tolerable range for all PEGs used.

NF retention and critical flux of small hydrophilic/hydrophobic molecules

This feature article provides details of a study in which small molar mass substances were used as model substances in nanofiltration using NF-270 and Desal-5 DL membranes. The hydrophobicities of ...

Physical and Mechanical Properties of Wood-Polypropylene Composites Made with Virgin and/or Recycled Polypropylene

The physical and mechanical properties of wood-polymer composites made with virgin or recycled polypropylene, or a mixture of these were studied. The composites made with recycled polypropylene had higher density, lower porosity, and higher dimensional stability compared to the composites made with virgin polypropylene. Although the composites made with recycled polypropylene exhibited lower tensile strength than those made with virgin polypropylene, they had higher Charpy impact strength. Scanning electron microscopy analysis of the fractured surfaces of the composites showed no significant differences in the fracture mechanisms of the studied composites. The degree of crystallinity was estimated to be higher for the virgin polypropylene than for the recycled one.

Mineral fillers for wood–plastic composites

Abstract Five mineral fillers were tested for wood–plastic composites (WPCs): calcium carbonate, two different types of wollastonite, soapstone and talc. The impact of the fillers on the mechanical properties of the composites was studied. The experiments included bending tests, tensile tests, Brinell hardness and scanning electron microscopy experiments. The amount of wood, mineral and plastic (polypropylene) was kept steady. Only the mineral type was changed during the tests. A control sample without any mineral added was also manufactured. The mineral addition improved the tensile strength of the WPCs. The hardness of the composite was also improved when the minerals were added, and along with the increasing mineral hardness, the hardness of the composite increased. The wollastonite acicular shape was crushed during the manufacturing process, so the phase of the process in which the minerals are added requires careful consideration.

Weathering of wood-polypropylene composites containing pigments

Outdoor applications of composites have raised questions about their durability. In this study, the effects of outdoor weathering on the properties of wood-polypropylene composites with and without pigments were examined. The composites were placed outdoors for one year, and their colour changes were evaluated after 1, 3, 6, 9 and 12 months of weathering. The durability of the composites was assessed by testing flexural strength and density. Scanning electron microscopy was applied to evaluate the surface degradation of the composites. The weathering resulted in considerable colour fading of the composites. The composites containing darker colour pigments had better colour stability. After weathering, the general trend was a decrease of the flexural strength and density of the composites. The decrease in flexural strength was found to be lower for the composites having higher density.ZusammenfassungDer Einsatz von Verbundwerkstoffen im Außenbereich hat Fragen bezüglich ihrer Dauerhaftigkeit aufgeworfen. In dieser Studie wurde der Einfluss einer Freibewitterung auf die Eigenschaften von Holz-Polypropylen-Verbundwerkstoffen mit und ohne Pigmente untersucht. Die Verbundwerkstoffe wurden über einen Zeitraum von einem Jahr im Freien gelagert und die Farbänderungen wurden nach 1-, 3-, 6-, 9- und 12-monatiger Bewitterung gemessen. Anhand von Biegefestigkeits- und Dichteprüfungen wurde die Dauerhaftigkeit der Verbundwerkstoffe bestimmt. Die Veränderung der Oberflächen wurde mittels Raster-Elektronenmikroskopie beurteilt. Die Bewitterung führte zu starkem Ausbleichen der Farbe. Verbundwerkstoffe mit dunkleren Farbpigmenten zeigten eine bessere Farbbeständigkeit. Nach der Bewitterung wurde generell eine Abnahme der Biegefestigkeit und der Dichte der Verbundwerkstoffe festgestellt. Bei Verbundwerkstoffen mit höherer Dichte nahm die Biegefestigkeit weniger stark ab.

Comparison of water absorption and mechanical properties of wood-plastic composites made from polypropylene and polylactic acid.

Abstract This study focuses on the water absorption and mechanical properties of composites made from softwood sawdust and plastics, such as virgin and recycled polypropylene and polylactic acid (PLA). The composites were processed by extrusion, and their properties were investigated by a water immersion test, mechanical tests and a cyclic test for moisture resistance. Scanning electron microscopy was used to study the morphology of the fracture surfaces of the composites. The composites made with recycled polypropylene had the lowest water absorption and thickness swelling of the studied composites. The PLA composites made with heat-treated sawdust showed the highest flexural strength. Of the polypropylene based composites, virgin polypropylene resulted in composites with higher flexural strength. The Charpy impact strength of the composites was found to have an inverse trend compared to flexural strength. Cyclic treatment of the studied composites resulted in 20–60% loss of flexural strength, depending on type of composite.

The effect of mineral fillers on the thermal properties of wood-plastic composites

Abstract The thermal properties of wood-plastic composites with five different mineral fillers were studied. The tested mineral fillers were calcite (CaCO3), two different qualities of wollastonite, soapstone, and talc. The amount of wood, mineral, and plastic (polypropylene) was kept constant. Only the mineral type has been changed during the tests. The thermal behavior of the samples was studied by using a differential scanning calorimeter, a thermogravimetric analyzer and by determining the heat build-up. The analyzed properties were compared with a reference sample made without adding any minerals. The results show that the addition of mineral fillers does not remarkably change the thermal stability of composites. All the studied mineral fillers except soapstone had a small effect on the heat build-up.

Resistance to weathering of wood-polypropylene and wood-wollastonite-polypropylene composites made with and without carbon black

Purpose - The purpose of this paper is to study natural and accelerated weathering of wood-polypropylene (WF-PP) and wood-wollastonite-polypropylene composites made with and without carbon black.De ...

Thermal performance and optical properties of wood–polymer composites

The thermal performance and optical properties of wood–polypropylene composites made from untreated wood material with and without metal-containing pigments, and composites made from heat-treated wood material were studied. The thermal heat buildup and linear shrinkage were determined. The impact of the optical properties of the surface of the composites on the heat buildup was analysed. The wood–polypropylene composites made from untreated wood without pigment were found to have the lowest heat buildup; a similar composite containing grey pigment had the highest heat buildup. The linear shrinkage of the studied wood–polypropylene composites was in the range 0.05–0.16%.

Effects of water immersion‐freeze‐thaw cycling on the properties of wood‐polypropylene composites containing pigments

Purpose – The purpose of this paper is to study the effects of water immersion‐freeze‐thaw treatment on the physical properties, flexural strength (FS) and morphology of wood‐polypropylene composites containing pigments.Design/methodology/approach – Wood‐polypropylene composites containing brown, green and grey pigments were compounded in a conical twin‐screw extruder. A composite manufactured without any pigment addition was used as a reference. The amount of pelletized wood, polypropylene and coupling agent (MAPP) was kept constant. The moisture content, thickness swelling (TS), FS and surface colour of the composites were measured before and after water immersion‐freeze‐thaw cycling. Scanning electron microscopy (SEM) was used to study the morphology of the composites.Findings – FS and dimensional stability were reduced after exposure to water immersion‐freeze‐thaw cycling for all composites. The surface properties (colour and roughness) of the composites also changed after exposure to water immersion‐...