Water Absorption Of Composites Research Articles

Effect of virgin and recycled plastics on moisture sorption of nanocomposites from newsprint fiber and organoclay

In this study the effect of virgin and recycled plastics on water absorption of nanocomposites from newsprint fiber and organoclay was studied. Newsprint fiber was mixed with either virgin or recycled polypropylene (PP) at 30% by weight fiber loading. The samples were made by melt compounding and then injection molding. The concentration was varied as 0, 2.5, and 5% for nanoclay. The amount of coupling agent was fixed at 10% for all formulations. The long-term water absorptions of samples were evaluated by immersing them in water at room temperature for several weeks, and water diffusion coefficients were also calculated by evaluating the water absorption isotherms. The results indicated that whether or not virgin plastic is used has a significant effect on the water absorption of composites. The water absorption of the newsprint fiber/recycled plastic composites was higher than those of virgin plastics. Furthermore, with addition of nanoclay content in composites, water absorption decreased. Water absorption of all formulations was proved to follow the kinetics of a Fickian diffusion process. Morphological findings showed the formation of intercalated morphology and better dispersion with 2.5% of nanoclay.

Preparation and Characterization of CCCW/Foamed Concrete Composite

Aimed at improving the waterproofing property of foamed concrete, a heat-insulating and waterproofing composite applied in underground engineering was prepared by using cementitious capillary crystalline waterproofing material and foamed concrete. The properties of foamed concrete and composite such as compressive strength, water absorption and thermal conductivity were tested and contrasted, and the compounding reaction mechanism was analyzed. The results show that, compared with foamed concrete, the water absorption of composite has been significantly reduced while the heat-insulating property of foamed concrete is maintained and the overall waterproofing and heat-insulation performance has been significantly improved. A new approach solving underground heat-harm such as high temperature and high humidity is provided.

Thermal Expansion of High Filler Content Cellulose-Plastic Composites

The effects of resin content (10–30%), cellulose fiber length (120 and 300 micrometer), and molding conditions (press, injection, and extrusion molding) on the thermal expansion of high filler content cellulose/polypropylene composites were evaluated. Other physical properties such as densities, bending strengths, and water absorption of composites were also determined. The results indicated that thermal expansion of composites is dependent on the above conditions. Small thermal expansion was observed for composites with low resin (high cellulose) content. Composites with long fibers (300 micrometer) showed smaller thermal expansion than those of 120 micrometer, except for injection-molded composites with 20% resin content. Composites prepared by injection and extrusion molding showed anisotropy of thermal expansion depending on the parallel and perpendicular directions of molding. The results of thermal expansion are discussed in the light of other physical properties and the interaction of fibers in the composites.

Preparation and characterization of polypropylene/wood flour/nanoclay composites

In this study, the effects of coupling agent and nanoclay loading on the mechanical properties and water absorption of composites are investigated. Composites based on polypropylene (PP), wood flour, nanoclay, and maleated polypropylene (MAPP) were made by melt compounding and then injection molding. The mechanical analysis showed that the biggest improvement of the tensile and flexural strengths can be achieved for the nanoclay loading at 3%. However, further increasing of the loading of nanoclay resulted in a decrease of all the mechanical properties. The maximum tensile and flexural strengths (increase of ∼46%, compared to the pure PP) were achieved in the composites when 7.5% MAPP was used as coupling agent in the manufacture of the composites. Finally, it was found that addition of nanoclay or MAPP reduced the water absorption property of the composites. However, the extent of improvement in the water absorption is more prominent with MAPP.

Effects of nanoclay and coupling agent on the physico‐mechanical, morphological, and thermal properties of wood flour/polypropylene composites

AbstractThis article presents the effects of coupling agent and nanoclay (NC) on some properties of wood flour/polypropylene composites. The composites with different NC and maleic anhydride grafted polypropylene (MAPP) contents were fabricated by melt compounding in a twin‐screw extruder and then by injection molding. The mass ratio of the wood flour to polymer was 40/60 (w/w). Results showed that applying MAPP on the surface of the wood flour can promote filler polymer interaction, which, in turn, would improve mechanical properties of the composite as well as its water uptake and thermal stability. Composite voids and the lumens of the fibers were filled with NC, which prevented the penetration of water by the capillary action into the deeper parts of composite. Therefore, the water absorption in composites fabricated using NC was significantly reduced. Scanning electron microscopy has shown that the treatment of composites with 5 wt% MAPP, promotes better fiber–matrix interaction, resulting in a few numbers of pull‐out traces. In all cases, the degradation temperatures shifted to higher values after using MAPP. The largest improvement on the thermal stability of composites was achieved when NC was added. POLYM. ENG. SCI., 2011. © 2010 Society of Plastics Engineers

Biobased composites from glyoxal–phenolic resins and sisal fibers

Lignocellulosic materials can significantly contribute to the development of biobased composites. In this work, glyoxal–phenolic resins for composites were prepared using glyoxal, which is a dialdehyde obtained from several natural resources. The resins were characterized by 1H, 13C, 2D, and 31P NMR spectroscopies. Resorcinol (10%) was used as an accelerator for curing the glyoxal–phenol resins in order to obtain the thermosets. The impact-strength measurement showed that regardless of the cure cycle used, the reinforcement of thermosets by 30% (w/w) sisal fibers improved the impact strength by one order of magnitude. Curing with cycle 1 (150 °C) induced a high diffusion coefficient for water absorption in composites, due to less interaction between the sisal fibers and water. The composites cured with cycle 2 (180 °C) had less glyoxal resin coverage of the cellulosic fibers, as observed by images of the fractured interface observed by SEM. This study shows that biobased composites with good properties can be prepared using a high proportion of materials obtained from natural resources.

Chemical Treatments of Natural Fiber for Use in Natural Fiber-Reinforced Composites: A Review

Studies on the use of natural fibers as replacement to man-made fiber in fiber-reinforced composites have increased and opened up further industrial possibilities. Natural fibers have the advantages of low density, low cost, and biodegradability. However, the main disadvantages of natural fibers in composites are the poor compatibility between fiber and matrix and the relative high moisture sorption. Therefore, chemical treatments are considered in modifying the fiber surface properties. In this paper, the different chemical modifications on natural fibers for use in natural fiber-reinforced composites are reviewed. Chemical treatments including alkali, silane, acetylation, benzoylation, acrylation, maleated coupling agents, isocyanates, permanganate and others are discussed. The chemical treatment of fiber aimed at improving the adhesion between the fiber surface and the polymer matrix may not only modify the fiber surface but also increase fiber strength. Water absorption of composites is reduced and their mechanical properties are improved.

Studies on Acrylonitrile-Butadiene (NBR) Latex-Reinforced Jute Nonwoven Fabric Composites: Chemical Resistance, Mechanical Properties, and Water Absorption

Composites were fabricated by impregnating the jute nonwoven fabric in a bath of acrylonitrile-butadiene (NBR) latex. The effects of different pickup ratios (dry-to-dry weight) of jute nonwoven fabric to NBR latex viz., 1:0.5, 1:1, 1:1.5, 1:2, and 1:2.5 on the performance of composites have been studied. The fabricated composites have been evaluated for physico-mechanical properties and chemical resistance. Percent water absorption of composites has been determined both at room temperature and boiling water. Effects of different relative humidity on the equilibrium moisture content of the natural jute nonwoven fabric-NBR composites have been evaluated.

Physico-mechanical Properties of Paper Sludge-Thermoplastic Polymer Composites

This study investigates the effect of paper sludge’s mixing ratio and the types and concentrations of coupling agents on the physical and mechanical properties of paper sludge-thermoplastic polymer composites. In the experiment, four levels of mixing ratios of paper sludge to thermoplastic polymer (10: 90, 20: 80, 30: 70 and 40: 60) and three levels of coupling agent (Epolene G-3003TM) content (1, 3, and 5 wt.%) were designed to discuss the physical and mechanical properties of composite. Composite density, as expected, increased but melt flow index decreased when the paper sludge content increased. Thickness swelling and water absorption of composites was slightly improved by the addition of paper sludge compared with control specimens. Tensile properties of composites significantly increased as the mixing ratio of paper sludge increased. Especially, tensile modulus improved with the increase of paper sludge content. Flexural strength and modulus showed similar trends to that of the tensile properties. Notched and unnotched Izod impact strengths lowered by the addition of paper sludge. With the addition of coupling agent, G-3003TM, tensile and flexural properties improved considerably compared with control specimens (without any coupling agent). Epolene G-3003TM, with high molecular weight, was effective in the improvement of the composites’ tensile and flexural properties.

Preparation and properties of composites made from rice straw and poly(vinyl chloride) (PVC)

AbstractRice straw was employed for the preparation of lignocellulosic‐poly(vinyl chloride) (PVC) composites. The effect of pretreatment of rice straw, concentration of PVC, pressure as well as pressing temperature on the mechanical properties and water absorption was studied. Also, the effect of lignin as coupling agent on the mechanical properties and water absorption of composite was studied. Composites of rice straw comprising both PVC and a coupling agent offer superior properties compared to those made from only rice straw and PVC. The extent of improvement in the mechanical properties and dimensional stability of composites depended not only on the pretreatment of rice straw, concentration of PVC and lignin but also on pressure and pressing temperature. Copyright © 2004 John Wiley & Sons, Ltd.

Isothermal moisture properties of wood-cementitious composites

This article describes a study undertaken to examine the moisture properties of lightweight concrete prepared from clay, cement, and wood aggregates at isothermal conditions. The sorption-desorption isotherm curves of different mixtures show a strong hysteresis. The effect of wood aggregates on the water absorption of composite has been investigated by gamma ray absorption spectrometer. It is found that the sorptivity of the composite is very affected by the presence of wood aggregates in clay-cement matrix. Test results have been confirmed both qualitatively, using magnetic resonance imaging method, and quantitatively, from capillary suction curve calculated from sorption isotherm and pore size distribution.