Effect of acetylation on dimensional stability,mechanical, and dynamic properties of jute board

Jute slivers were acetylated in pilot scale following a no catalyst‐no solvent method at 120°C for 2 h. The weight % gain was found to be 11.37. Different jute boards were pressed under heat and pressure using acetylated jute sliver and urea formaldehyde resin. Neutral salt (NaCl), acid salt (NH₄Cl), and melamine powder were used separately for curing urea formaldehyde. For comparison purposes, control boards were also prepared using nonacetylated slivers. The boards were tested for water soaking, cyclic water soaking, and cyclic humidity to see the effect of acetylation on dimensional stabilization. This chemical modification was found to improve the dimensional stability to a great extent for NaCl and NH₄Cl cured boards and to a less extent for a melamine‐cured one. Tensile and flexural strengths were tested by Instron before and after the cyclic tests. Retention values were found to be as high as 60% after cyclic water tests for acetylated boards and the same was as low as 24% for control boards. Dynamic parameters, such as storage flexural modulus (E′), loss flexural modulus (E"), and loss factor or damping efficiency (tan δ) were determined in a fixed‐frequency mode. Dynamic mechanical study revealed that tan δ peaks were lowered due to increased bulkiness of the fiber after acetylation and thus restricted mobility. A tiny additional peak was also visible at ∼90°C beside the main peak at ∼125°C for boards with modified slivers. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 72: 935–944, 1999     

Recycling of jute textile in phenol formaldehyde–jute composites

Jute textile was recycled into composites using different percents of phenol formaldehyde (PF) resin. The effect of the resin percent, from 12 to 30%, on the flexural strength, tensile strength, water absorption, and thickness swelling of the produced composites was studied. To improve the dimensional stability of the produced composites, jute textile was acetylated or steamed. The effect of steaming and acetylation on the structure and thermal stability of jute fibers was studied using Fourier Transform Infrared (FTIR) spectroscopy and Thermogravimetric analysis (TGA), respectively. The effect of these treatments on the flexural strength, tensile strength, water absorption, and thickness swelling of the produced composites was studied. Steaming of jute textile was superior to acetylation in improving the dimensional stability. Cyclic wetting and drying test of the composites showed that steaming of the jute textile resulted in much less irreversible and reversible thickness swelling than in case of using acetylated or untreated jute textile. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 3588–3593, 2003     

Influence of electron beam treatment of jute on the thermal properties of random and two-directional jute/poly(lactic acid) green composites

In the present study, randomly aligned jute fiber/poly(lactic acid) (PLA) and two-directionally aligned jute fabric/PLA green composites with jute (50% by weight) treated with electron beam at different dosages (0, 5, 10, 30, 50, and 100?kGy) were fabricated by compression molding technique and the effect of electron beam treatment on their thermal properties was investigated in terms of thermal expansion, thermal stability, dynamic mechanical thermal property, and heat deflection temperature (HDT). The dynamic storage modulus and HDT of neat PLA were significantly increased by incorporating jute fibers or fabrics into PLA, whereas the coefficient of thermal expansion (CTE) and the damping property were decreased, reflecting the enhancement in the interfacial adhesion between the jute and the PLA by electron beam treatment with an optimal dosage of 10?kGy and the reinforcing effect by jute. The result exhibited that the thermal stability, storage modulus, and HDT of jute/PLA green composites were highest with the electron beam irradiation of jute at 10?kGy and lowest at 100?kGy, whereas the CTE and tan δ were lowest at 10?kGy and highest at 100?kGy. The thermal behavior of random jute/PLA green composites shows a similar tendency to that of 2D jute/PLA counterparts and the influence of electron beam irradiation on the thermal properties studied was consistent with each other. The thermomechanical analysis, dynamic mechanical thermal analysis, thermogravimetric analysis, and HDT results were in agreement with each other, showing a comparable effect of electron beam irradiation on composites thermal characteristics.     

Characterization of jute fibers treated with soap–glycerol micelles

A tossa variety of jute fiber (Corchorus olitorious) treated with soap–glycerol micelles is characterized by infrared (IR) spectroscopy, X‐ray diffraction method, and tensilometry. The IR spectra for jute fibers treated with soap–glycerol micelles show a reduced absorption band due to O H stretching at a frequency of 3420 cm⁻¹ with almost absent OH bending frequencies, prominent CH₂ stretching and bending frequencies at 2915 and 1440 cm⁻¹ and reduced skeletal vibration at 1060 cm⁻¹. The percentage crystallinity measured by the X‐ray diffraction method increases from 45 to 53% on treated jute fibers. The tensile strength and strain percent at maximum load, Young's modulus, and work done per unit volume within an elastic limit (resilience) for treated fibers increased from 1.8 ± 0.2 to 3.43 ± 0.2 GPa, from 3.98 ± 0.1 to 4.75 ± 0.1, from 75 ± 2 to 113 ± 5 GPa, and from 26 ± 2 to 74 ± 3 MJ m⁻³, respectively. Using a stabilizing agent (2%) and a swelling agent (2% KOH), the tensile strength, strain percent, Young's modulus, and resilience increase to 4.02 ± 0.2 GPa, 4.85 ± 0.3, 154 ± 5 GPa, and 95 ± 4 MJ m⁻³, respectively. Under natural weathering at 12–30°C and 30–80% relative humidity over a prolonged period of 8 weeks, all the tensile properties for micelle‐treated fibers increase during the first 2 weeks of exposure and then decrease exponentially to the starting values. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 77: 852–856, 2000     

Studies on jute-reinforced composites,its limitations,and some solutions through chemical modifications of fibers

Jute, unlike other natural fibers, absorbs moisture and its moisture regain property is quite high. Water migration and subsequent degradation of jute-based composites can be a problem. Because jute is hydrophilic and the matrix resins are mostly hydrophobic, wetting of the fibers with resins is poor, for which high resin consumption may occur that would increase the cost of composites. To reduce the moisture regain property of jute fiber, it is essential to pretreat the jute fiber so that the moisture absorption is reduced and the wettability of the resin is improved. Jute fiber in the form of nonwoven jute has been pretreated with precondensate like phenol formaldehyde, melamine formaldehyde, cashew nut shell liquid-formaldehyde, and polymerized cashew nut shell liquid. The moisture content of the pretreated nonwoven jute has been determined by conventional methods and by a differential scanning calorimetric technique. Treatment of jute with precondensate causes the reduction of water regain property in jute. Pretreated nonwoven jute has been impregnated with phenol formaldehyde resin, and the composite board has been prepared therefrom. The jute composite board has been tested for bending strength, tensile strength, thickness swelling, and water absorption. Thermal analyses, such as differential scanning calorimetry and thermogravimetry, have also been conducted on jute and pretreated jute fibers. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 67:1093–1100, 1998     

Rheological characterization of PP/jute composite melts

The present article summarizes an experimental study on the molten viscoelastic behavior of PP/jute composites under steady and dynamic mode. Variations in melt viscosity and die swell of the composites with an increase in shear rate, fiber loading, and coupling agent concentration have been investigated using capillary rheometer. It was observed that with the addition of fibers and MAPP, the melt viscosity of the composites increased due to improved fiber‐matrix interfacial adhesion. Further, the dynamic viscoelastic behavior, measured using parallel plate rheometer, revealed an increase in the storage modulus (G′), indicating higher stiffness in case of fiber‐filled composites as compared with the virgin matrix. Time–temperature superposition was applied to generate various viscoelastic master curves. The fiber‐matrix morphology of the extrudates was also examined using scanning electron microscopy, which corroborated the findings of rheological properties. The treated composites displayed uniform distribution of fibers within the PP matrix with lesser surface irregularities. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 99: 1476–1484, 2006     

FTIR spectra and physico-chemical behavior of vinyl ester participated transesterification and curing of jute

In this article we report the transesterification of jute with n-Butylacrylate (BA) under appropriate condition using NaOH, Pyridine (Py), and a Pyridine–acetone mixture as a catalyst. The modified vinylog jute was subsequently cured with benzoylperoxide (BPO) in acetone at 50–60°C. The parent and chemically modified jute were characterized by FTIR spectra. The percent moisture regain, mechanical strength, and behavior to common chemical reagents of the parent and modified fibers have also been tested. Transesterification and curing of jute lowered the percentage of moisture regain, imparted mechanical strength, and resistance to common chemical reagents. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 79: 575–581, 2001     

Study of the thermal behavior of alkali‐treated jute fibers

Jute fibers were treated with 5% NaOH solution for 2, 4, 6, and 8 h to study the performance of the fibers as a reinforcing material in the composites. Thermal analysis of the fibers was done by the DTG and DSC technique. The moisture desorption was observed at a lower temperature in the case of all the treated fibers, which might be a result of the increased fineness of the fibers, which provides more surface area for moisture evaporation. The decrease in percentage moisture loss for the fibers treated with alkali for 6 and 8 h could be the result of the increased crystallinity of the fibers. The percentage degradation of the hemicellulose decreased considerably in all the treated fibers, conforming to the fact that the hemicellulose content was lowered on alkali treatment. The decomposition temperature for α‐cellulose was lowered to 348°C from 362.2°C for all the treated fibers, and the residual char formation increased to a significant extent. The enthalpy for the thermal degradation of α‐cellulose showed a decreasing trend for the fibers treated for 2 and 4 h, which could be caused by the initial loosening of the structure, followed by an increase in the enthalpy value in the case of the 6‐ and 8‐h‐alkali‐treated fibers resulting from increased crystallinity, as evident from the X‐ray diffraction. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 85: 2594–2599, 2002     

Cellulose triacetate prepared from low-grade hardwood dissolving pulp and its insoluble residues in acetylation mediums

As cellulose triacetate is prepared from low-grade hardwood dissolving pulp, a considerable amount of the insoluble residue was present in the acetylation medium of the acetic acid/acetic anhydride/sulfuric acid system. The characterization of this residue indicated that the insoluble residue is composed of cellulose triacetate and xylan diacetate, retaining a fiber structure of swollen form. To reduce the insoluble residues, reaction conditions for acetylation were investigated. As one of the remedies of reducing the insoluble residues, 17 different solvents were selected to add to the acetylation medium, and among these, dichloroacetic acid was found to be very effective for its reduction. The obtained cellulose triacetate could then reveal good thermal properties similar to that from high-grade dissolving pulps. Therefore, acetylation systems with an addition of an appropriate solvent can have a potential to industrially manufacture a high-quality cellulose triacetate from even low-grade hardwood-dissolving pulps, as observed in low-grade softwood-dissolving pulps. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 67: 289–297, 1998     

Graft copolymerization and characterization of 2‐hydroxyethyl methacrylate onto jute fiber by photoirradiation

UV radiation induced graft copolymerization of 2‐hydroxyethyl methacrylate onto natural lignocellulose (jute) fiber was carried out by two methods: simultaneous irradiation and grafting and preirradiation grafting. 1‐Hydroxycyclohexyl‐phenylketone was used as the photoinitiator in both methods. In the former method, the variation of the graft weight was measured for different values of radiation exposure time and the concentrations of both the monomer and photoinitiator. The latter method produced up to 76% graft weight compared to 45% obtained with the former method. The preirradiation method offers better control of the homopolymerization reaction compared to that afforded by the other method. The optimum value of the reaction parameters on the graft weight was evaluated. The mechanical properties of grafted samples were found to be drastically different from those of the as‐received ones and the effect was proportional to the percentage of graft weight. Differential scanning calorimetry studies showed that the percentage of graft add‐on of hydroxyethyl methacrylate with jute had a significant effect on the thermal properties. IR studies indicated the degree of grafting could be estimated by correlating the band intensities with the graft weight. The jute samples grafted with poly(hydroxyethyl methacrylate) at a level of 12% graft weight exhibited a maximum 20% increase in hydrophilicity. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 2898–2910, 2006     

Na2O-Al2O3-B2O3玻璃的热学性质和红外光谱

制备了Na2OAl2O3B2O3系统低熔点玻璃,确定了Na2OAl2O3B2O3系统玻璃成玻范围,研究了玻璃的转变温度(Tg)、热膨胀系数(α)和玻璃的红外光谱,表明这种玻璃的熔化温度低、转变温度也较低、玻璃的热膨胀系数较大,在近红外区有一水分的吸收带,在中红外区有BO、AlO的特征吸收带,以及玻璃的Tg、α与玻璃组成的关系。     

Effect of graft copolymerization of mixtures of acrylamide and methyl methacrylate on mechanical properties of jute fibers of different compositions

The role of persulfate-induced graft copolymerization of mixtures of acrylamide and methyl methacrylate at 50°C in modifying mechanical properties of jute fibers of different compositions was studied in a limited aqueous system following a pretreatment technique. Results obtained indicate that such a process admits a good scope for modification of mechanical properties of jute fiber depending on degree of grafting achieved and compositional variations of (1) the feed monomer mixture and (2) the multiconstituent jute itself, consequent to selective removal of lignin and hemicellulose to different extents from the fiber. Low to moderate removal of hemicellulose is more effective than a similar degree of removal of lignin from jute in rendering the fiber more amenable to vinyl grafting using the mixed monomer system without being adversely affected with respect to tensile properties. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 68: 1139–1147, 1998     

Graft copolymerization of nitrile monomers onto bleached jute fiber using potassium persulfate system and their textile characteristics

Graft copolymerization of nitrile monomers, such as acrylonitrile and methacrylonitrile, onto bleached jute fiber was carried out by using K₂S₂O₈/FeSO₄ redox system in nitrogen atmosphere and their effect on the textile characteristics was also investigated. Percent graft yield increased with the increase of concentrations of monomer, initiator, and catalyst, reaction time, and reaction temperature up to a certain value, and, thereafter, it decreased. The effect of percent grafting efficiency was similar to that of percent graft yield, except for the monomer concentration. The increase of percent graft yield was dependent on the availability of jute‐macroradicals as well as monomer radicals. Sometimes the predominancy of homopolymerization over grafting and the premature termination of growing grafted chains occurred because of the higher monomer radicals and excess primary radicals, SO₄^?? and ^?OH, from K₂S₂O₈ initiator. The percent graft yield of acrylonitrile and methacrylonitrile was 20.5 and 29.1%, respectively. Higher graft yield for methacrylonitrile might be due to the methyl group present in it. Infrared spectra at 2229–2235 cm^?1 of acrylonitrile‐ and methacrylonitrile‐grafted jute strongly supported the graft formation. Grafting of jute fiber improved the thermal stability, protected from photooxidative degradation, and decreased swellability as well as dyeability, etc. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 3622–3629, 2004     

Modification of jute by acrylic acid in the presence of Na3PO4 and K2S2O8 as catalysts under thermal treatment

Jute fabric was modified using acrylic acid (AA) as the finishing agent in the presence of K₂S₂O₈ and Na₃PO₄ catalysts separately or in selected combinations, employing a pad–dry–cure technique. Treatment with 10% acrylic acid at 30°C and at pH 7 produced optimum effects: a batching time of 45–60 min at 30°C, followed by drying of the batched fabric at 95°C for 5 min and curing of the dried fabric at 140°C for 5 min produced most balanced improvements in the textile related properties. Na₃PO₄ catalyst allowed esterification of AA with cellulosic, hemicellulosic, and lignin constituents of jute, and K₂S₂O₈ catalyst allowed radical polymerization of free acrylic acid or jute-bound acrylic acid moieties; the said processes ultimately lead to some degree of crosslinking of the chain polymers of jute. Examination of the surface morphology of untreated and treated jute fabrics by scanning electron microscopy revealed a good degree of masking effect on the unit cells of jute and intercellular regions by a cohesive film of polyacrylic acid or its salts, particularly when K₂S₂O₈ was used either alone or in combination with Na₃PO₄ as catalyst. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 68:63–74, 1998     

Mechanical properties of jute fibers and interface strength with an epoxy resin

Four different forms of jute fibers, namely untreated jute filament (UJF), sliver jute filament (SJF), bleached jute filament (BJF), and mercerized jute filament (MJF), have been subjected to tensile strength analysis following Weibull's theory. The MJF and BJF were obtained by the chemical modification of the UJF. A minimum of 50 fibers of each type, at three different gauge lengths, i.e., 15, 30, and 50 mm, were used to study the strength distribution and the effect of gauge length. The mean fiber strength was found to be the maximum for UJF followed, in the order, by BJF, MJF, and SJF (∼ 700, ∼ 660, ∼ 580, and ∼ 540 MPa, respectively, at 50‐mm gauge length). The strength was also found to decrease with an increase in gauge length. In all cases, good agreement was found with Weibull's statistical model. Single fiber composite tests, with an epoxy resin as the matrix, were carried out determine the critical fragment lengths and interfacial strength, following the Kelly–Tyson approach. The BJF was found to have the maximum interfacial adhesion (τ ≈ 140 MPa) followed by UJF, SJF, and MJF having τ values of ∼ 83, ∼ 57, and ∼ 47 MPa, respectively. Scanning electron microscope pictures showed the fiber surface was physically modified by the various treatments. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 75: 1585–1596, 2000     

鸦片类毒品酰化与硅烷化在GC-MS分析中的比较

比较了鸦片类毒品采用气相色谱/质谱分析前通过MSTFA硅烷化处理和MBTFA乙酰化处理后的分析结果;用乙基吗啡作内标,比较了血液中添加吗啡、6-单乙酰吗啡、可待因经过液相萃取后,再分别进行硅烷化和乙酰化处理后的检测结果;并比较了通过两种衍生化方法所测得的真实海洛因吸食致死者血样中上述3种毒品的浓度。结果说明,上述鸦片类毒品硅烷化后的响应高;乙酰化后的6-单乙酰吗啡和3-单乙酰吗啡的分离效果好;血液中乙酰化后的吗啡检测灵敏度高,而硅烷化后的6-单乙酰吗啡检测灵敏度高。两种方法各有特点,可以根据分析需要选择不同的方法。     

Preparation and characterization of bismaleimide-diamine prepolymers and their thermal-curing behavior

Various bismaleimide-diamine Michael addition type prepolymers were prepared through melt condensation and using acetone, dimethylformamide, and m-cresol as solvents in a molar ratio of 1 : 1. Structures of the prepolymers, such as terminal moieties and molecular weight of main chain, depended strongly on the preparation conditions used. More terminal double bonds were observed in the molecule of the prepolymer (sample 3) prepared in dimethylformamide solution without a catalyst. In contrast, the prepolymer produced in m-cresol solution had a polyaspartimide structure with a higher molecular weight. The differential scanning calorimetry and Fourier transform infrared spectra results demonstrated that the molecular structure of the prepolymer had a noticeable effect on their thermal-curing behavior. Thermal properties (T_g and T_d) of cured polymers were evaluated. The polyimide (sample 3b) from sample 3 exhibited the highest T_g and but still retained very good processing properties for film casting. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 70: 2471–2477, 1998     

Preparation,characterization, and properties of unbleached,bleached, and grafted pulps from JRC‐321 variety jute fiber

Graft copolymerization onto jute pulps opened the door to new concepts in pulp and paper research. Jute pulp from the JRC‐321 variety white jute fiber was prepared by the alkaline sulfite pulping process. The pulp obtained was bleached by the chlorination, extraction, and hypochlorite sequence technique to remove excess lignin for making bright and good quality paper. Special attention was focused on the graft copolymerization of acrylamide monomer onto the unbleached and bleached pulps by the use of a complex initiating system: Cu(II)/glycine/KHSO₅ in aqueous solution. It was found that percentage grafting was high in the case of bleached pulp. The grafted pulps so obtained were characterized by FTIR and their thermal behavior was characterized by TGA. Their mechanical properties such as tensile strength, percentage elongation, and tenacity were measured and compared. The physical properties such as rot‐resistance and water‐retention capacity of the grafted and the ungrafted pulps were determined. The effect of the percentage grafting variation on the above mentioned properties was examined. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 83: 1963–1969, 2002     

Characterization of alkali‐treated jute fibers for physical and mechanical properties

Changes occurring in jute fibers when treated with a 5% concentration of a NaOH solution for 0, 2, 4, 6, and 8 h were characterized by weight loss, linear density, tenacity, modulus, FTIR, and X‐ray measurements. A 9.63% weight loss was measured during 2 h of treatment with a drop of hemicellulose content from 22 to 12.90%. The linear density value showed no change until 2 h of treatment followed by a decrease from 33.0 to 14.5 denier by 56% after 6 h of treatment. The tenacity and modulus of the fibers improved by 45 and 79%, respectively, and the percent breaking strain was reduced by 23% after 8 h of treatment. X‐ray diffractograms showed increase in crystallinity of the fibers only after 6 h of treatment, while FTIR measurements showed much of the changes occurring by 2 h of treatment with an increased amount of OH groups. By measuring the rate of change of the modulus, tenacity, and percent breaking strain with the time of treatment, a clear transition was apparent at 4 h of treatment with the dissolution of hemicellulose, causing a weight loss and drop in the linear density before and development of crystallinity with an improvement in the properties after the transition time. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 80: 1013–1020, 2001     

Assessing the fire behavior of woods modified by N-methylol crosslinking,thermal treatment,and acetylation

Wood products are often treated by different techniques to improve their longevity when used as building materials. Most of the time, the goal is to increase their resistance to weathering effects, deformations in material dimensions or biotic decomposition. These wood treatment techniques have a significant impact on pyrolysis and burning behavior. The general effects of three different common wood treatments on flame retardancy were investigated by comparing treated woods with their untreated counterparts and with other kinds of wood. While the acetylation of beech leads to a slightly increased fire hazard, the thermal treatment of wood and crosslinking of cellulose microfibrils dimethyloldihydroxy-ethyleneurea show a limited flame retarding effect. Switching to woods with a higher lignin content, and thus higher char yield, however, results in a more pronounced improvement in flame retardancy performance. This article delivers a comprehensive and balanced assessment of the general impact of different wood modifications on the fire behavior. Further, it is a valuable benchmark for assessing the flame retardancy effect of other wood modifications.