Effect of water absorption on frost resistance of clay roofing tiles

Abstract

High frost resistance is one of the signs of good quality in clay roofing tile products. The present paper deals with the question of whether the water absorption of clay roofing tiles affects frost resistance. The results show that clay roofing tiles with high water absorption can be just as frost proof as tiles with lower absorption. Median pore radius is found to be an important factor in determining frost resistance: increasing the median pore radius increases frost resistance.     

White Rice Husk Ash Filled Natural Rubber/Linear Low Density Polyethylene Blends

Abstract

Natural rubber (NR)/Linear low density polyethylene (LLDPE) blends were prepared using an internal mixer at 150°C and a rotor speed of 55 rpm. The tensile strength, tensile modulus and hardness increase with increasing LLDPE content whereas elongation at break and mass swell show decreasing trend. With 30/70 (W/W) NR/LLDPE blends, the increasing white rice husk ash (WRHA) loading also increases the tensile modulus and hardness but reduced the tensile strength, elongation at break, and mass swell.     

Mechanical,water absorption,and morphology of recycled polymer blend rice husk flour biocomposites

Rice husk flour (RHF) biocomposites based on uncompatibilized and compatibilized recycled high density polyethylene/recycled polyethylene terephthalate (rHDPE/rPET) with ethylene‐glycidyl methacrylate (E‐GMA) copolymer were prepared through a two‐step extrusion and hot pressing with fiber loadings of 40, 60, and 80 wt %. Results showed that tensile and flexural properties increased. However, the elongation to break and impact strength decreased as the RHF loading increased. Compatibilizing polymer blend matrices can further enhance the mechanical properties. Water absorption (WA) test were examined in distilled and seawater. It is interesting to note that for composites made from uncompatibilized matrix, the calculated D and K_SR were lower in seawater, but for the compatibilized matrix composites, the D and K_SR obtained were generally lower in distilled water. However, compatibilization of rHDPE/rPET has been markedly reduced the WA and thickness swelling. Scanning electron microscope analysis of the compatibilized matrix composites confirmed the improved interfacial bonding of matrix–matrix and filler–matrix phases. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41494.     

Technological properties of glass-ceramic tiles obtained using rice husk ash as silica precursor

This paper reports the results of a study focused on the obtainment of glass-ceramic by using rice husk ash (RHA) as silica precursor. RHA is a by-product generated in biomass plants using rice husk as fuel for kilns or in the rice mills to generate steam for the parboiling process. Worldwide, it is annually produced about 132 Mt of rice husk, which gives rise to a production of 33 Mt/year of RHA. Glass-ceramic tiles were produced by a sinter-crystallization process using a glassy frit formulated in the MgO–Al₂O₃-SiO₂ composition system. The realized glass-ceramics were studied according to ISO rules for sintering and technological properties (water absorption, apparent density, bending strength, Young's modulus, deep abrasion, Mohs hardness). To complete the investigation crystalline phase formation and microstructural characterization of the glass-ceramic materials was carried out using X-ray diffraction (XRD) and scanning electron microscopy (SEM). Finally, chemical durability tests on parent glass and derived glass-ceramics were performed. The results obtained showed that it is possible to use RHA to produce glass-ceramic tiles by a sinter-crystallization process, obtaining nepheline (Na₂O*Al₂O₃*SiO₂) as main crystalline phase and forsterite (2MgO*SiO₂) at 900 °C. Regarding technological features, the sintered materials showed bending strength values and Mohs hardness higher with respect to commercial glass-ceramics like NeopariesR. Other properties as water absorption (0.5%) allowed to classify these materials into the Group BIa characteristic of high sintered ceramic tiles according to European Standard rule.     

Effect of Processing Time on the Tensile,Morphological, and Thermal Properties of Rice Husk Powder‐Filled Polypropylene Composites

Abstract

Brabender plasticorder internal mixer was used to incorporate rice husk powder into polypropylene. Rice husk powder (RHP)‐filled polypropylene (PP) composite was prepared by varying mixing time under constant rotor speed (50 rpm) at two mixing temperatures. Brabender mixing torque, tensile properties, morphology, and thermal properties were investigated in detail. Results indicate that the tensile properties, such as Young's modulus, yield strength, and elongation at break, do not exhibit a significant trend with the increasing of processing time. Scanning electron microscope (SEM) micrographs reveal the better filler dispersion at longer processing time. Differential scanning calorimetry (DSC) analysis indicates nucleating ability of RHP and reduction of degree of crystallinity of PP at higher temperature and longer processing time. In fact, RHP changes the melting point of PP in the composites.     

Design and analysis of single-factor experiments: Analysis of variance of the effect of rice husk ash and commercial fillers in NR compounds

Summary White rice husk ash (WRHA) and black rice husk ash (BRHA) were incorporated into natural rubber (NR) using a laboratory-sized two-roll mill. A conventional vulcanization system was used for curing and physical tests of the NR vulcanized involved determining of tensile and tear resistances. For comparison purposes, precipitated silica (Zeosil-175) and carbon black (N774) were used too. Using the analysis of variance of single-factor experiments, it can be concluded that: BRHA is non-reinforcing filler and its use is limited to 20 phr; WRHA is semi-reinforcing filler and the variation of filler loading (0 up to 50 phr) causes the maximum variation upon tensile strength of NR compounds; and, that although carbon black and silica are reinforcing fillers, a real reinforcement is reached up to 20 phr for tensile strength.     

A procedure to evaluate the resistance to biological colonization as a characteristic for product quality of ceramic roofing tiles

Ceramic roofing tiles suffer deterioration through time due to environmental exposure. Biological colonization affects the appearance and integrity of building materials, such as roofing tiles. The resistance to biocolonization represents an important property affecting the product quality of ceramic roofing tiles. While natural colonization of roofing tiles by organisms is a progressive, heterogeneous, and slow process, laboratory assessment of this phenomenon requires a sensitive procedure that can be carried out within a reasonable period of time. Different microorganisms have been evaluated and the use of phototrophs, specifically the cyanobacterium Oscillatoria, presented several advantages such as good adherence, homogeneous growth on surfaces, and the chlorophyll-autofluorescence which can be used for a sensitive detection. Colonization by Oscillatoria on roofing tiles was assessed by measuring the autofluorescence of cells. This study proposes the use of specific cyanobacterial cells and a simple method for monitoring biofilm formation and biological colonization of roofing tiles.     

气相、沉淀、稻壳SiO2／聚乙烯醇复合膜的性能比较

分别采用气相SiO2、沉淀SiO2和稻壳SiO2与聚乙烯醇（PVA）接不同的比例制备成复合膜。比较了3种不同来源的纳米SiO2／PVA复合膜的拉伸性能及耐水性能。结果表明：SiO2含量相同时,复合膜的断裂伸长率和拉伸强度的排列顺序为：气相SiO2／PVA〉稻壳SiO2／PVA〉沉淀SiO2／PVA;拉伸模量的排列顺序为：气相SiO2／PVA〉沉淀SiO2／PVA〉稻壳SiO2／PVA;3种来源的SiO2都可以提高PVA的耐水性,且耐水性随SiO2含量的增大而增强,SiO2含量相同时,复合膜的耐水性排列顺序为：气相SiO2／PVA〉沉淀SiO2／PVA〉稻壳SiO2／PVA。     

Preparation and properties of rice husk‐filled plasticized wheat gluten biocomposites

Rice husk (RH) reinforced wheat gluten/glycerol (Gly/Glut) and rice husk (R) reinforced wheat gluten‐glycerol/chitosan‐polyethylene glycol (Gly/Glut‐CP) biocomposites with varying rice husk loading were prepared. Morphological, thermal, and mechanical properties of the biocomposites were investigated by scanning electron microscope, thermogravimetric analyzer, and tensile testing machine, respectively. Water absorption properties and surface functional groups of the biocomposite films were determined by weight measurement and attentuated total reflectance Fourier transform infrared spectroscopy, respectively. The results were discussed in terms of chitosan‐polyethylene glycol (CP) and rice husk content. Although CP and 1‐g rice husk addition decreased maximum degradation temperature of Gly/Glut film, adding of more rice husk did not considerably change the maximum degradation temperature. As a result of adding CP, the tensile strength of Gly/Glut film was increased by about 183%, whereas tensile modulus was decreased by about 34%. POLYM. ENG. SCI., 54:1477–1483, 2014. © 2013 Society of Plastics Engineers     

Determination of filler content in thermoplastic composites by FTIR analysis

FTIR quantitative analytical method is described as an alternative technique for computation of the filler content in polypropylene composites. White rice husk ash (WRHA) was incorporated as a filler material into polypropylene homopolymer. Absorption peaks at 480, 621, and 790 cm^?1 chosen for the quantitative analysis work have been shown to give good linearity with increasing filler contents. © 1995 John Wiley & Sons, Inc.     

Preparation and characteristics of polyurethane made with polyhydric alcohol‐liquefied rice husk

The limited availability of fossil resource is causing the urgent need to get renewable chemicals. Solvent liquefaction can convert rice husk into bio‐based chemicals. Rice husk was liquefied in polyhydric alcohol catalyzed by sulfuric acid under atmospheric pressure. The viscosity, residue content, and weight average molecular weight (M_w) of liquefied rice husk were 3089 cps, 23.6% and 4100, respectively. Prolonging the liquefaction time decreased the residue content and increased the average molecular weight. Polyurethane (PU) foams were successfully prepared from the liquefied rice husk with different molar ratios of NCO to OH (NCO/OH). The mechanical properties of PU foams showed that the compressive strength in the vertical direction is higher than that in the horizontal direction. With Increase of the NCO/OH molar ratio from 1.0 to 2.0, compressive strength in the vertical direction of PU foams increased from 70.6 to 114.7 kPa at 10% strain. Thermal analysis results showed that thermal stability of liquefied rice husk‐based PU resins was better than that of fossil‐ and liquefied wood‐ based PU resins. Increasing the NCO/OH molar ratio and inorganic residue of rice husk can help to increase thermal stability. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 45910.     

Study on the pozzolanic properties of rice husk ash by hydrochloric acid pretreatment

The pozzolanic properties of rice husk ash by hydrochloric acid pretreatment are reported in the paper. Three methods have been used to estimate the pozzolanic activity of rice husk ash. The heat evolution and the hydration heat of cement, the Ca(OH)₂ content in the mortar and the pore size distribution of mortar are determined. It is shown that compare with the rice husk ash heated untreated rice husk, the sensitivity of pozzolanic activity of the rice husk ash heated hydrochloric acid pretreatment rice husk to burning conditions is reduced. The pozzolanic activity of rice husk ash by pretreatment is not only stabilized but also enhanced obviously. The kinetics of reaction of rice husk ash with lime is consistent with diffusion control and can be represented by the Jander diffusion equation. A significant increase in the strength of the rice husk ash (pretreated) specimen is observed. The results of heat evolution indicate that the rice husk ash by pretreatment shows the behavior in the increase of hydration of cement. The cement mortar added with the rice husk ash by pretreatment has lower Ca(OH)₂ content after 7 days and the pore size distribution of the mortar with the rice husk ash with pretreatment shows a tendency to shift towards the smaller pore size.     

Study of the morphology and mechanical properties of polypropylene composites with silica or rice‐husk

The mechanical, morphological behavior and water absorption characteristics of polypropylene (PP) and silica, or PP and rice‐husk, composites have been studied. The silica used in this study as filler was a commercial type produced from soluble glass or rice husks. The compatibilizing effect of PP grafted with monomethyl itaconate (PP‐g‐MMI) and/or with vinyltriethoxysilane (PP‐g‐VTES) as polar monomers on the mechanical properties and water absorption was also investigated. In general, a high loading of the studied fillers in the polymer matrix increases the stiffness and the water absorption capacity. This effect is more noticeable in the tensile modulus of the PP/silica composite with PP‐g‐VTES as compatibilizer. However, the increase of the rice‐husk charge as a natural filler in the PP matrix decreases the stiffness, and in the presence of PP‐g‐MMI as compatibilizer in PP/rice‐husk, the tensile modulus and water absorption of the composite were improved. The better adhesion and phase continuity in the PP/silica and PP/rice‐husk composites with different compatibilizers was confirmed by the morphological study. Copyright © 2004 Society of Chemical Industry     

Strong and chemically inert sinter crystallised glass ceramics based on Estonian oil shale ash

Abstract

In heat and power production, oil shale combustion forms substantial amounts of solid waste, including fly ash. The present paper is dedicated to the manufacturing of frit derived glass ceramics from melting high amounts of this waste (65–67 wt-%) combined with inexpensive minerals, such as rhyolite (33–35 wt-%). Owing to a surface mechanism of crystallisation, fine powders led to glass ceramics with high strength and reliability, even for rapid treatments (fast heating, at a rate of 40°C min^?1, followed by 30 min holding stage). To minimise the presence of pressing and demoulding induced defects, the tiles were prepared by incorporating binders, i.e. polyethylene glycol or kaolin, to the frit mixtures. Finally, the stabilising effect of recycled borosilicate glass powders, mixed with waste derived glass powders, was also investigated with promising results for the production of a chemically stable material.     

Application of rice husk ash as fillers in the natural rubber industry

Rice husk ash (RHA) obtained from agricultural waste, by using rice husk as a power source, is mainly composed of silica and carbon black. A two‐stage conventional mixing procedure was used to incorporate rice husk ash into natural rubber. For comparison purposes, two commercial reinforcing fillers, silica and carbon black, were also used. The effect of these fillers on cure characteristics and mechanical properties of natural rubber materials at various loadings, ranging from 0 to 40 phr, was investigated. The results indicated that RHA filler resulted in lower Mooney viscosity and shorter cure time of the natural rubber materials. The incorporation of RHA into natural rubber improved hardness but decreased tensile strength and tear strength. Other properties, such as Young's modulus and abrasion loss, show no significant change. However, RHA is characterized by a better resilience property than that of silica and carbon black. Scanning electron micrographs revealed that the dispersion of RHA filler in the rubber matrix is discontinuous, which in turn generates a weak structure compared with that of carbon black and silica. Overall results indicate that RHA can be used as a cheaper filler for natural rubber materials where improved mechanical properties are not critical. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 98: 34–41, 2005     

Studies on mechanical characterization and water resistance of glass fiber/thermoplastic polymer bionanocomposites

This experimental work is aimed at studying the performance of rice husk flour/glass fiber reinforced high density polyethylene hybrid nanocomposites. To meet this objective, the nanoclay was compounded with high density polyethylene (HDPE), rice husk flour (RF), glass fiber, and coupling agent in an internal mixer; then, the samples were fabricated by injection molding. The concentration was varied from 0 to 6 per hundred compounds for nanoclay and from 0 to 15% for glass fiber, individually. The amount of coupling agent was fixed at 2% for all formulations. The morphology, water absorption, thickness swelling, and mechanical properties of nanocomposites were evaluated as a function of nanoclay and glass fiber contents. The results indicated that both modulus and strength were improved when glass fibers were added to the composites system but impact strength and moisture absorption further decreased with the increase of glass fiber content. The morphology of the nanocomposites has been examined by using X‐ray diffraction. The morphological findings revealed that the nanocomposites formed were intercalated. The mechanical analysis showed that the biggest improvement of the tensile and flexural modulus and strengths can be achieved for the nanoclay loading at 4 per hundred compounds. However, further increasing of the loading of nanoclay resulted in a decrease of impact strength. Finally, it was found that addition of nanoclay reduced the water absorption and thickness swelling of the composites. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Wear resistance and friction coefficient of nano-SiO<Subscript>2</Subscript> and ash-filled HDPE/lignocellulosic fiber composites

This work comparatively evaluates the effect of nano-SiO₂ (at 2 and 3 wt%), rice husk and bagasse ash (at 5 and 10 wt%) on the wear resistance and friction coefficient of HDPE (high-density polyethylene)/lignocellulosic fiber composites. Rice husk and bagasse fibers at 50% by weight contents were mixed with HDPE and 2% maleic anhydride-grafted polyethylene as compatibilizer. SEM images showed a fairly appropriate connection between the polymer matrix and fillers. We found that the fillers improve the wear resistance, and the effect of nano-SiO₂ is more pronounced. The rice husk ash showed a better performance compared to the bagasse ash, probably due to greater SiO₂ content measured by X-ray fluorescence spectrometry. In contrast to nano-SiO₂, both ashes had a reducing effect on other mechanical strengths (Izod impact resistance, modulus of elasticity and modulus of rupture). All fillers remarkably increased the water absorption and thickness swelling. The water uptake of composites increased after wear.     

Wood flour-high density polyethylene composites: Influence of silanization and esterification on mechanical properties

Silanization and esterification are strategies used to treat wood flour (WF) to produce surface functionalized hydrophobic WF leading to an improvement in dispersion and compatibility between wood phase and polymer phase. Silanization involves functionalization of alkyl groups by coupling trimethoxy (propyl) silane (MPS), and esterification functionalizes WF with ester groups, using acetic anhydride (Ac). Modified WF was incorporated into recycled high-density polyethylene (HDPE) to form reHDPE/mod-WF composite system. Both modifications produced highly hydrophobic WF surfaces which improved the dispersion in the reHDPE matrix; resulting in a significant difference in impact strength, specifically at 20 wt% filler, from 74.5 Jm⁻¹ to 146.3 Jm⁻¹ and 113.5 Jm⁻¹, that is, up to 96% and 52% for MPS-WF and Ac-WF, respectively. However, filler agglomeration higher than 20 wt% reduces the composite impact strength. The results herein demonstrate that alkyl-functionalized WF show excellent dispersion in the reHDPE system and is the preferred technique to improve system mechanical resilience as compared to esterification.     

The Fatigue Behaviour of Filled Epoxidized Natural Rubber Compounds

Abstract

The fatigue behaviour of white rice husk ash (WRHA) filled ENR-50 compounds was compared with those of silica (Vulcasil-S) and carbon black (N 330) filled compounds. The effect of WRHA loading on scorch time and Mooney viscosity was also studied. The incorporation of WRHA in ENR-50 compounds reduced the scorch time but increased the Mooney viscosity. The increment in filler loadings has resulted in the reduction of the fatigue fife. The fatigue behaviour of ENR-50 vulcanizates was observed to be strain dependent. At a similar filler loading, silica filled vulcanizates showed the highest fatigue life followed by those of WRHA and carbon black.     

Interfacial strengthening of polypropylene composites via bimodal porosity in Rice husk ash: Comparison with calcium carbonate reinforcement

Polypropylene is used in the textile industry in the manufacturing of plastic yarns, tapes, etc., but its low tensile strength and Young's modulus limits its associated applications. Composites of polypropylene with reinforcement of CaCO₃ and rice husk ash were processed by compression molding. Bimodal porosity in rice husk ash particles has shown an improved interfacial anchoring effect via capillary effect resulting in enhanced mechanical properties, whereas such an effect is not observed with CaCO₃ reinforcement in polypropylene matrix. On reinforcement with 10 wt % of each of rice husk ash and CaCO₃, thermal decomposition temperature of polypropylene (333.3 °C) shifted to higher value of 415.9 °C and polypropylene Young's modulus (749.5 MPa) increased to 789.5 MPa (by 5.3%), but tensile strength decreased from 23.5 to 21.2 MPa (by 2.3 MPa only). The isolated contribution of CaCO₃ and rice husk ash has been delineated, and resulting interfacial strengths have been quantified using analytical models. Rice husk ash has shown a stronger interfacial anchoring and can effectively replace CaCO₃ as reinforcement for achieving improved mechanical and thermal properties of polypropylene composites. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 46989.