Thermal analysis of the powder and the bran of algaroba

The powder and the bran of algaroba pods, submitted to drying temperatures of 55, 65, 75, 85, 95 and 105°C, were studied by conventional and thermogravimetric methods. The dynamic thermogravimetric curves of the samples indicated the following thermal stability order: 105>55>65>95>85>75°C. The powder and the bran of algaroba pods, dried at 55°C, presented protein content higher and isothermal thermogravimetric profiles comparable. The calorimetric curves of samples, dried at 55°C, indicated the gelatinization of starch. This revised version was published online in August 2006 with corrections to the Cover Date.     

Characterization and comparative study of pyrolysis kinetics of the rice husk and the elephant grass

A comparative evaluation of different biomasses allows the choice that presents the best potential as fuel for energy production. The knowledge of the thermal and kinetics parameters of the biomass in the process of thermal conversion is fundamental as their chemical and physical characterization. Various methodologies have been developed for the determination of kinetic parameters as apparent activation energy and reaction order from the thermogravimetric analysis. In this work, the apparent activation energy needed to break the bonds of hemicelluloses and cellulose of rice husk and elephant grass during the thermal conversion was evaluated according to the kinetics models of Flynn and Wall and Model Free Kinetics developed by Vyazovkin. The biomass elephant grass and rice husk were characterized for moisture, ash and volatile matter by ASTM E871, ASTM E1755, ASTM E872, respectively, and fixed carbon by difference. The percentage of carbon, hydrogen, nitrogen, and oxygen were determined by ultimate analysis. The elephant grass showed to be more suitable for production of bio-oil through pyrolysis due to the higher percentage of volatile, less ash content and less energy required to break the bonds of hemicellulose and cellulose than rice husk in the thermal conversion process.     

Thermogravimetric analysis of rice husk flour filled thermoplastic polymer composites

The thermal degradation and thermal stability of rice husk flour (RHF) filled polypropylene (PP) and high-density polyethylene (HDPE) composites in a nitrogen atmosphere were studied using thermogravimetric analysis. The thermal stability of pure PP and HDPE was found to be higher than that of wood flour (WF) and RHF. As the content of RHF increased, the thermal stability of the composites decreased and the ash content increased. The activation energy of the RHF filled PP composites increased slowly in the initial stage until α=0.3 (30% of thermal degradation region) and thereafter remained almost constant, whereas that of the RHF filled HDPE composites decreased at between 30 and 40 mass% of RHF content. The activation energy of the composites was found to depend on the dispersion and interfacial adhesion of RHF in the PP and HDPE matrix polymers. This revised version was published online in July 2006 with corrections to the Cover Date.     

Characterization of Starch Pharmaceuticals by DSC Coupled to a Photovisual System

The present work proposes evaluation of the gelatinization processes of starch by means of DSC coupled with a photovisual system. The use of DSC, TG and DTA for a fast and efficient evaluation of the starch is suggested. The DSC curves of starch gels with water contents of 20, 30, 40 and 50% (mass/v) exhibited different phase transitions, corresponding to the gelatinization processes at the different water contents for the different lots. The DSC-photovisual system confirmed calorimetric behaviour differences between the starch lots studied. This revised version was published online in July 2006 with corrections to the Cover Date.     

Characterization of rice husks and the products of its thermal degradation in air or nitrogen atmosphere

Rice husk is a by-product of rice milling process and are a major waste product of the agricultural industry. They have now become a great source as a raw biomass material for manufacturing value-added silicon composite products, including silicon carbide, silicon nitride, silicon tetrachloride, pure silicon, zeolite, fillers of rubber and plastic composites, adsorbent and support of catalysts. The bulk and true densities of raw rice husk with different moisture and sizes were determined. The rice husk was subjected to pyrolysis in fluidized-bed reactor in air or nitrogen atmosphere. The products obtained were characterized by thermogravimetric and X-ray powder analysis, IR-spectroscopy, scanning electron microscopy and nitrogen adsorption at 77 K. The specific surface area of the products is comparable with this of γ-Al₂O₃. The kinetics of H₂SeO₃ adsorption out of aqueous solutions at 298 K was studied. The adsorption capacity of white rice husks ash was found to be higher than that of black rice husk ash and the adsorption kinetics obeyed the second order kinetic equation.     

Structural, physico-chemical, thermal and pasting properties of potato (Solanum tuberosum L.) flour

In this work, two varieties of potato flour (Ágata and IAPAR Cristina) were studied by simultaneous thermogravimetry–differential thermal analysis (TG–DTA), differential scanning calorimetry (DSC), rapid viscoamylographic analysis (RVA), and microscopy (NC-AFM) that were compared with conventional physico-chemical analysis, according different granulometry of each flour. Flours of IAPAR Cristina showed higher levels of starch, fiber, and phosphate and it showed higher thermal stability (TG–DTA), as well as higher pasting temperature and viscosity (RVA), and lower enthalpy of gelatinization (DSC) in the two granulometries. Flours of Agata showed higher gelatinization enthalpy (DSC) and lower pasting temperature (RVA). Atomic force microscopy—non contact method (NC-AFM), was important to check for protrusions and pores of the flour surfaces. The differences between cultivars can be attributed mainly to the genotypes and growth conditions of the tubers, which can modify the flour properties.     

钾元素对生物质及其三组分热解的影响

采用机械混合法将KCl加入到纤维素、半纤维素、木质素以及稻壳和稻壳模拟物等生物质中,得到了一系列不同K含量的生物质样品,通过热重(TG)实验考察了K元素对生物质热解特性的影响.结果表明,K元素对生物质三组分热解特性的影响比较复杂,纤维素的最大热解失重速率随着KCl添加量的增加而降低,但KCl对半纤维素和木质素热解特性的影响不显著.无论是否添加KCl,模拟生物质的热解特性均可以认为是三组分热解的简单叠加.但酸预处理稻壳三组分间的稳定结构,导致其DTG曲线在300 ℃左右的热解峰由稻壳模拟物的尖峰变为肩峰,其热解焦炭收率也比稻壳模拟物的略低.此外,实验还采用浸渍法向酸预处理稻壳中添加了KCl.TG实验结果表明,K元素的存在对生物质热解具有一定的催化作用,但KCl的添加方式不同,生物质的热解特性有明显差别,生物质样品经机械混合添加KCl后,其热解焦炭收率呈下降趋势(纤维素除外),浸渍法添加的KCl导致酸预处理稻壳的最大热解失重速率和焦炭收率升高.     

Enhancing Resistant Starch Content of High Amylose Rice Starch through Heat–Moisture Treatment for Industrial Application

The objective of the present study is to enhance the resistant starch (RS) content of high amylose rice starch with heat–moisture treatment (HMT) for industrial application. The optimized HMT condition for achieving the highest RS content established using response surface methodology (RSM) was a temperature of 100 °C, moisture content of 24.2%, and a time of 11.5 h. Upon HMT, the RS content increased from 32.1% for native starch to 46.4% in HMT starch with optimized condition. HMT of the starches reduced the solubility and swelling power. The surface of HMT starch granules was more irregular than native starch. The X-ray diffraction (XRD) peak intensity at 2θ = 5° was greatly reduced by HMT, and the peaks at 22.7° and 24.2° were merged. HMT increased the gelatinization temperature and reduced the gelatinization enthalpy. HMT provides a method for the production of high-yield RS2 with high amylose rice starch in industrial application.     

Thermal properties of complexes of amaranthus starch with selected metal salts

Metal cations (Cu(II), Fe(III), Mn(II), and Ni(II)) are ligated by amaranthus starch as proven by EPR spectra and conductivity measurements. The hydroxyl groups of starch are the coordination sites. The acetate and nitrate anions of the metal salts behave as bidentate ligands and reside in the inner coordination sphere of resulting polycenter Werner complexes. There is only a weak degeneration of orbitals of central metal ions caused by a shift of unpaired spin from the central atom to the ligand. The ligation of the central metal atoms resulted in a variation of the thermal stability, pathway, and rate of thermal decomposition of starch as proven by thermogravimetric (TG) and differential scanning calorimetric (DSC) measurements.     

Investigation of thermal decomposition of rice husk

Studies on the thermal decomposition of untreated rice husk and that treated with HCl and H₂SO₄ of various concentrations were carried out by TG, DTG and DTA. The mass loss occurred in three distinct stages, namely, removal of moisture, release of volatile matter and burning of combustible material. The corresponding temperature ranges for untreated husk were 40–150, 215–350 and 350–690°C. The final temperature of combustion decreased with acid-treatment of the husk. The thermal decomposition of the husk was found to be an exothermic process.     

Starch Gelatinization Kinetics in Bread Dough. DSC investigations on 'simulated' baking processes

Starch gelatinization in wheat flour dough of various moisture contents was quantitatively evaluated by means of DSC. The experimental records were worked out in the form of excess heat capacity vs. T traces which were deconvoluted to single out the contribution of starch gelatinization from that of the decomposition of amylose-lipid complexes. The quantitative procedure used put into evidence that a third endothermic process would take place in the dough with a poor moisture content. DSC runs carried out with sealed pans (i.e., at constant moisture level) and open pans (from which some water was free to evaporate) allow simulation of two extreme conditions of a real baking process, namely that relevant to the central core and to superficial layer of a dough loaf, respectively. The extent of starch gelatinization occurred in these conditions was quantitatively assessed. These data were collected at various heating rates and used to define temperature-time-transformation(TTT) diagrams which are useful tools to predict the progress of baking for any given thermal history of the system. This revised version was published online in July 2006 with corrections to the Cover Date.     

Heat/mass transfer characteristics and nonisothermal drying kinetics at the first stage of biomass pyrolysis

Biomass pyrolysis can be divided into three stages: moisture evaporation, main devolatilization, and continuous slight devolatilization. This present study focuses on the heat and mass transfer characteristics of biomass in the first pyrolysis stage, which takes place in the range of room temperature to 150?°C. Thermalgravimetric experiments of rice husk and cotton stalk were performed by a synchronic thermal analyzer (TG/DSC). Four nonisothermal drying models were obtained from common isothermal drying models in order to describe the drying behavior of agricultural products. The moisture content of biomass decreased rapidly as the temperature increased and an apparent water loss peak was observed in the temperature range of 65?C75?°C. DSC could be regarded as the superposition of three parts: heat flow from moisture evaporation, heat flow from the heat capacity of unevaporated moisture, and heat flow from the heat capacity of dry base biomass. The heat requirements for the dehydration of 1?kg rice husk and cotton stalk were 251 and 269?kJ, respectively. Nonisothermal drying models were evaluated based on the coefficient of determination (R ²) and reduced chi-square (??²). Page model was found to be the best for describing the nonisothermal drying kinetics. The values of activation energy were determined to be 9.2 and 15.1?kJ/mol for rice husk and cotton stalk, respectively.     

Bismaleimide/rice husk silica reinforced composites

Silica derived from the renewable resource rice husk is modified using stearic acid and N-[4-(chlorocarbonyl)phenyl]maleimide. These materials are used as fillers in the bismaleimide, 4,4′-bismaleimidodiphenylmethane (BMIM), and thermally cured. The thermogravimetric (TG) curves for polyBMIM/silica composites showed no pronounced changes compared to the TG curve for the pure polyBMIM. Kissinger–Akahira–Sunose, Flynn–Wall–Ozawa, and Friedman methods are used to compute the activation energy (E _a) for degradation. Silica and surface-modified silica using stearic acid dispersed by ultrasonication increase the activation energy for degradation and show considerable influence on the thermal stability of cured BMIM. The long alkyl chain present in the stearic acid modified silica and the bulky spacer present in the chemically modified silica definitely alter the degradation process of cured BMIM. The SEM studies indicated uniform dispersion of the silica particles in the polyBMIM.     

Study on physico-chemical properties of dialdehyde yam starch with different aldehyde group contents

Dialdehyde yam starches (DASs) are prepared and characterized. Compared with native starch, viscosity average molecular weight of DASs decreases, and the extent of degradation depends on content of the aldehyde groups. Fourier transform infrared (FT-IR) spectra confirm that the characteristic peak for CO group at 1732 cm^?1 is enhanced with the increasing of content of the aldehyde groups. Scanning electron microscopy (SEM) micrographs show that the surface of starch granules becomes wrinkled. X-ray diffraction (XRD) patterns clearly indicate that their crystallinity decreases with the increasing content of the aldehyde groups before they become amorphous at higher oxidation states. The experimental results of thermogravimetric analysis (TGA) show that DASs have poor stability as compared to native starch. With the increase in content of the aldehyde groups, the thermal stability of DAS declines gradually. According to the results of differential scanning calorimetry (DSC), gelatinization temperature (T_o and T_p) of DASs are increased, whereas the gelatinization enthalpy decreased.     

Thermal analysis of fly ash-based zeolites

The paper presents research results on dehydration properties and thermal behaviour of zeolites synthesized from fly ash, applying TG (thermogravimetry), DTG (derivative thermogravimetry) and SDTA (simultaneous differential thermal analysis) methods. In result of the analysis conducted water contents in zeolite samples were defined. On the basis of the data obtained from the thermogravimetric analysis, thermal behaviour of zeolites was assessed. This revised version was published online in July 2006 with corrections to the Cover Date.     

Phase transitions of cassava starch dispersions prepared with glycerol solutions

The aim of this work was to study the glass transition, the glass transition of the maximally freeze-concentrated fractions, the ice melting and the gelatinization phenomenon in dispersions of starch prepared using glycerol-water solutions. The starch concentration was maintained constant at 50 g cassava starch/100 g starch dispersions, but the concentration of the glycerol solutions was variable (C _g= 20, 40, 60, 80 and 100 mass/mass%). The phase transitions of these dispersions were studied by calorimetric methods, using a conventional differential scanning calorimeter (DSC) and a more sensitive equipment (micro-DSC). Apparently, in the glycerol diluted solutions (20 and 40%), the glycerol molecules interacted strongly with the glucose molecules of starch. While in the more concentrated glycerol domains (C _g>40%), the behaviour was controlled by migration of water molecules from the starch granules, due to a hypertonic character of glycerol, which affected all phase transitions.     

Impacts of Hydrothermal Treatments on the Morphology,Structural Characteristics,and In Vitro Digestibility of Water Caltrop Starch

The influence of hydrothermal treatments on the structural properties and digestibility of water caltrop starch was investigated. Scanning electron microscopy (SEM) showed some small dents on the surface of starch granules for samples treated with heat moisture treatment (HMT), but not for samples treated with annealing (ANN) which generally showed smoother surfaces. The gelatinization temperature of starch was generally increased by hydrothermal treatments, accompanied by a trend of decreasing breakdown viscosity. These results implied the improvement of thermal and shearing stability, particularly for HMT in comparison to ANN. After being cooked, the native and ANN-modified water caltrop starch granules were essentially burst or destroyed. On the other hand, the margin of starch granules modified by HMT and dual hydrothermal treatments remained clear with some channels inside the starch granules. X-ray diffraction revealed that the crystalline pattern of water caltrop starch changed from the C_A-type to the A-type and the relative crystallinity reduced with increasing moisture levels of HMT. Results of ANN-modified water caltrop starch were mostly similar to those of the native one. Moreover, water caltrop starch modified with HMT20 and dual modification contained a pronouncedly higher resistant starch content. These results suggested that HMT, ANN, and dual modification effectively modified the functional properties of water caltrop starch.     

Chlorinated thermal stabilizer for optically clear PMMA

Optically clear poly(methyl methacrylate) (PMMA) blends with HET‐EG oligoester (synthesized by condensation of chlorendic acid with ethylene glycol) at six different compositions were prepared by bulk polymerization. The effect of HET‐EG in the PMMA matrix on the optical clarity of PMMA blend was measured using ultraviolet‐visible spectroscopic study. The thermal stability of PMMA blends was investigated using differential scanning calorimetric (DSC) and thermogravimetric (TG) analyses. The parameters to deduce the thermal stability of pure PMMA and PMMA blends were calculated from DSC and TG results. The thermal stability of PMMA was found to increase effectively by loading 5% of HET‐EG oligoester without marring optical clarity. The probable physical and chemical actions of HET‐EG oligoester on the thermal stability of PMMA are discussed. Copyright © 2011 John Wiley & Sons, Ltd.     

Rice Husk‐derived Hierarchical Micro/Mesoporous Carbon–Silica Nanocomposite as Superior Filler for Green Electronic Packaging Material

In this study, a carbon‐controllable hierarchical micro/mesoporous carbon–silica material derived from agricultural waste rice husk was easily synthesized and utilized as filler in an epoxy matrix for electronic packaging applications. Scanning electron microscopy, thermogravimetric analysis, and N₂ adsorption/desorption isotherms were used to characterize the morphology, thermal stability, carbon content, and porous structural properties, respectively, of the as‐obtained carbon–silica material, namely rice husk char (RHC ). As a filler material, the uniformly dispersed RHC filler in the epoxy/RHC composite was easily prepared through hydrogen bonding of the silanol group of silica with the epoxy matrix. For electronic packaging applications, the thermal conductivity and thermomechanical properties (storage modulus and coefficient of thermal expansion) of the epoxy/RHC composites improved with increasing carbon content. Moreover, loading of the 40% RHC filler substantially enhanced the storage modulus of the epoxy/RHC composite (5735 MPa ) compared to the epoxy with 40% commercial silica filler (3681 MPa ). Considerable commercial potential is expected for the carbon–silica composite because of the simple synthesis process and outstanding performance of the prepared packaging material.     

Thermal properties and morphology of cassava starch grafted with different content of polystyrene

The interest in replacing synthetic polymers by biodegradable materials from renewable resources is steadily increasing. In this work, cassava starch grafted with different content of polystyrene (PS) was synthesized via free-radical polymerization using suspension polymerization technique. Thermal data of pure starch and the grafted starch with different content of PS were collected by simultaneous thermogravimetric (TG)–differential scanning calorimetry (DSC) setup in open alumina pans. Separately, typical DSC measurements were conducted in standard aluminum pans with lid. The data obtained by different methods are correlated and discussed. Morphology of cryogenic fracture surface of starch sample was studied by scanning electron microscopy. In order to obtain more reliable data about the processes taking place during the thermal treatment, the changes of surface morphology of starch treated at different temperatures are observed.