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     

Jute fabric reinforced engineering thermoplastic sandwich composites. I. The effect of molding time

Jute fabric‐reinforced sandwich composites were fabricated using engineering thermoplastics. The jute fabrics were precoated with thermosetting resin to improve their thermal resistance before molding of the composites. Thermal gravimetric analysis (TGA) studies revealed that the resin coated fabrics decomposed at higher temperature than the uncoated jute. The onset of degradation of the coated fibers also falls between that of jute fibers and the thermoset resins. This indicates the presence of good interfacial bonding between jute fibers and both resins. Isothermal TGA studies revealed that jute could withstand brief exposure to higher temperature at 270 and 290°C. The sandwich composites were fabricated at 270°C by compression molding for 1.5 and 3 min in each case, and then characterized by flexural, tensile and morphological studies, i.e., SEM and optical microscopy. The uncoated jute fabric yielded composites of superior mechanical properties even with 3 mins molding at 270°C which is close to the degradation temperature of uncoated jute fibers. This is an indication that it is feasible to prepare jute fiber filled engineering polymer composites provided the exposure time at high temperature during processing does not exceed 3 mins as determined by TGA isothermal studies. SEM studies revealed strong fiber/matrix interfacial bonding between jute and the thermoset resins while the inferior mechanical properties of the resin coated sandwich composites could be attributed to the poor interfacial bonding between the already cured thermoset coating and the matrix based on optical microscopy of the polished cross‐sections. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Effect of lactic acid chain length on thermomechanical properties of star‐LA‐xylitol resins and jute reinforced biocomposites

Star‐shaped bio‐based resins were synthesized by direct condensation of lactic acid (LA) with xylitol followed by end‐functionalizing of branches by methacrylic anhydride with three different LA chain lengths (3, 5 and 7). The thermomechanical and structural properties of the resins were characterized by ¹³C NMR, Fourier transform IR spectroscopy, rheometry, DSC, dynamic mechanical analysis (DMA), TGA and flexural and tensile tests. An evaluation of the effect of chain length on the synthesized resins showed that the resin with five LAs exhibited the most favorable thermomechanical properties. Also, the resin's glass transition temperature (103 °C) was substantially higher than that of the thermoplast PLA (ca 55 °C). The resin had low viscosity at its processing temperature (80 °C). The compatibility of the resin with natural fibers was investigated for biocomposite manufacturing. Finally, composites were produced from the n5‐resin (80 wt% fiber content) using jute fiber. The thermomechanical and morphological properties of the biocomposites were compared with jute‐PLA composites and a hybrid composite made of the impregnated jute fibers with n5 resin and PLA. SEM and DMA showed that the n5‐jute composites had better mechanical properties than the other composites produced. Inexpensive monomers, good thermomechanical properties and good processability of the n5 resin make the resin comparable with commercial unsaturated polyester resins. © 2017 Society of Chemical Industry     

Study of jute fiber reinforced polyester composites by dynamic mechanical analysis

Cyanoethylation of jute fibers in the form of nonwoven fabric was studied, and these chemically modified fibers were used to make jute–polyester composites. The dynamic mechanical thermal properties of unsaturated polyester resin (cured) and composites of unmodified and chemically modified jute–polyester were studied by using a dynamic mechanical analyzer over a wide temperature range. The data suggest that the storage modulus and thermal transition temperature of the composites increased enormously due to cyanoethylation of fiber. An increase of the storage modulus of composites, prepared from chemically modified fiber, indicates its higher stiffness as compared to a composite prepared from unmodified fiber. It is also observed that incorporation of jute fiber (both unmodified and modified) with the unsaturated resin reduced the tan δ peak height remarkably. Composites prepared from cyanoethylated jute show better creep resistance at comparatively lower temperatures. On the contrary, a reversed phenomenon is observed at higher temperatures (120°C and above). Scanning electron micrographs of tensile fracture surfaces of unmodified and modified jute–polyester composites clearly demonstrate better fiber–matrix bonding in the case of the latter. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 71: 1505–1513, 1999     

Thermal degradation of a phenolic resin,vegetable fibers,and derived composites

The thermal degradation behavior of resol, several vegetable fibers (two types of cotton fibers, sisal and sugar cane bagasse) and derived polymer composites have been investigated using thermogravimetric analysis (TGA). The initial thermal degradation temperature T_ONSET, the temperature at the maximum degradation rate TD_M, and the char left at 500°C corresponding to the crosslinked resol were higher than the values measured for the fibers and their composites. Thus, the addition of the fibers reduced the thermal resistance of the phenolic thermoset. The polymer and the fiber‐composites showed a complex degradation involving different thermal decomposition processes. For that reason, the DTG curves were deconvoluted and a phenomenological kinetic expression was found for each individual peak. The overall thermal decomposition curve was recalculated adding each degradation process weighted according to its contribution to the total weight loss. An increase in the activation energy corresponding to the cellulose degradation was observed in the composites, highlighting the protective action of the resin encapsulating the fibers. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Effect of fiber chemical treatment of nonwoven coconut fiber/epoxy composites adhesion obtained by RTM process

In this work untreated and alkali treated nonwoven coconut fiber mats/epoxy resin composites were manufactured using the resin transfer molding process. The alkaline solution removes some impurities present on fibers superficial layers and the effect regarding fiber/matrix adhesion were investigated by thermogravimetric analysis, dynamic mechanical analysis (DMA), scanning electron microscopy (SEM), ultrasonic C‐scan, and quasi‐static flexural test. Results show a removing of some amorphous fibers constituents, mainly waxes, extractives, and hemicellulose, revealing the fiber roughness surface but no initial degradation temperature changing. Regarding the composites, a similar interfacial adhesion was observed in both one through the results of SEM, DMA and quasi‐static flexural tests. The conclusion is that chemical treatment conditions applied on the fiber surface was been suitable to improve fiber roughness but did not the adhesion between coconut fibers mat and epoxy resin. POLYM. COMPOS., 38:2518–2527, 2017. © 2015 Society of Plastics Engineers     

Effect of layering pattern on the physical,mechanical, and thermal properties of jute/bagasse hybrid fiber‐reinforced epoxy novolac composites

In this study, randomly oriented short jute/bagasse hybrid fiber‐reinforced epoxy novolac composites were prepared by keeping the relative volume ratio of jute and bagasse of 1:3 and the total fiber loading 0.40 volume fractions. The effect of jute fiber hybridization and different layering pattern on the physical, mechanical, and thermal properties of jute/bagasse hybrid fiber‐reinforced epoxy novolac composites was investigated. The hybrid fiber‐reinforced composites exhibited fair water absorption and thickness swelling properties. To investigate the effect of layering pattern on thermomechanical behavior of hybrid composites, the storage modulus and loss factor were determined using dynamic mechanical analyzer from 30 to 200°C at a frequency of 1 Hz. The fracture surface morphology of the tensile samples of the hybrid composites was performed by using scanning electron microscopy. The morphological features of the composites were well corroborated with the mechanical properties. Thermogravimetric analysis indicated an increase in thermal stability of pure bagasse composites with the incorporation of jute fibers. The incorporation of hybrid fibers results better improvement in both thermal and dimensional stable compared with the pure bagasse fiber composites. POLYM. COMPOS., 2012. © 2012 Society of Plastics Engineers     

Effect of fibers treatment on dynamic mechanical and thermal properties of epoxy hybrid composites

Epoxy hybrid composites fabricated by reinforcing 2‐hydroxy ethyl acrylate (2‐HEA) treated oil palm empty fruit bunch (EFB) and jute fibers. It assume that chemical modification of jute and oil palm EFB fibers increased fiber/matrix interfacial bonding and it results in enhanced thermal properties of hybrid composites. Dynamic mechanical and thermal analysis of treated hybrid composites was carried out. Results indicated that chemical modification of oil palm EFB and jute fibers affect the dynamic mechanical and thermal properties of hybrid composites. The storage modulus values of hybrid composites increases with chemical treatment and loss modulus increased with fiber treatment in hybrid composites. Damping factor peak values of treated hybrid composites shifted toward the lower temperature compared to both untreated hybrid composites. Cole–Cole analysis was made to understand the phase behaviour of the hybrid composites. Thermogravimetric analysis indicated an increased in thermal stability of hybrid composite with the incorporation of chemically modified fibers. POLYM. COMPOS., 36:1669–1674, 2015. © 2014 Society of Plastics Engineers     

Improvement of functional properties of jute‐based composite by acrylonitrile pretreatment

Cyanoethylation of jute fiber in the form of nonwoven fabric was successfully achieved using an acrylonitrile monomer which is said to react with the hydroxyl groups of fiber constituents. The degrees of cyanoethylation to different extents were undertaken by varying the reaction time. An IR study showed that extent of cyanoethylation increases with increase of the reaction time. Cyanoethylated fibers thus obtained were further treated with unsaturated polyester resin to obtain modified fiber composites. These composites have been found to be tolerant against cold and boiling water where water absorption and thickness swelling are much reduced compared to those of unmodified fiber composite. It is also observed that the moisture content of the modified fiber composites is remarkably reduced. Cyclic tests reveal that use of cyanoethylated fiber leads to improvement of the dimensional stability of the fiber composites. The mechanical properties of the modified fiber composites improved remarkably due to better bonding at the fiber–matrix interface and this effect is more pronounced with a higher degree of cyanoethylation. A scanning electron micrograph of the fractured surfaces of cyanoethylated jute composite showed excellent retention of resin on broken fiber ends, whereas the unmodified composite showed uncoated fibers and holes in the matrix. DSC data demonstrated that the moisture content of the composites reduces with increase of the cyanoethylation. Both TG and DSC thermograms showed an additional peak due to decomposition of cyanoethyl group which is shifted to a higher value with the extent of cyanoethylation. However, the cellulose degradation temperature remained almost the same. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 78: 495–506, 2000     

Thermal degradation of epoxy resin reinforced with polypropylene fibers

The influence of polypropylene fibers on the thermal degradation of epoxy composites was investigated with thermogravimetric analysis. Three composites with 5, 10, or 15 wt % polypropylene fibers were prepared with epoxy as a matrix material. The polypropylene fibers, used as reinforcing materials, retarded the thermal decomposition, and increasing the weight percentage of the fiber material increased the thermal stability to a certain extent. Of the three composites, the 10 wt % polypropylene fiber/epoxy resin composite showed very good thermal stability, which was indicated by the increase in the resin decomposition temperature from 280°C for the 5 wt % polypropylene fiber/epoxy resin composite to 375°C for the 10 wt % polypropylene fiber/epoxy resin composite. The Horowitz–Metzger method was used to calculate the activation energies, and the results were tabulated. A morphological analysis was carried out with scanning electron microscopy to evaluate the dispersion of the fibers in the epoxy matrix. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 104: 500–503, 2007     

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     

Structural characterization and tensile properties of Borassus fruit fibers

The chemical and instrumental analysis of alkali‐treated Borassus fibers is carried out to explore the possibility of their use as reinforcement in green composites. The chemical analysis shows presence of α‐cellulose, hemicellulose, and lignin. This is further confirmed by FTIR and high‐resolution solid‐state ¹³C NMR spectroscopy. The influence of alkali treatment on morphology and mechanical properties is attempted by SEM and UTM techniques, respectively. The wide‐angle X‐ray diffraction analysis of the native and treated fibers shows that alkali treatment influences the crystallinity of the fibers. The efficacy of the Borassus fibers (native and treated) as a component of green composites is discussed. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Chemical modification of hemp,sisal, jute,and kapok fibers by alkalization

Plant fibers are rich in cellulose and they are a cheap, easily renewable source of fibers with the potential for polymer reinforcement. The presence of surface impurities and the large amount of hydroxyl groups make plant fibers less attractive for reinforcement of polymeric materials. Hemp, sisal, jute, and kapok fibers were subjected to alkalization by using sodium hydroxide. The thermal characteristics, crystallinity index, reactivity, and surface morphology of untreated and chemically modified fibers have been studied using differential scanning calorimetry (DSC), X‐ray diffraction (WAXRD), Fourier transform infrared spectroscopy (FTIR), and scanning electron microscopy (SEM), respectively. Following alkalization the DSC showed a rapid degradation of the cellulose between 0.8 and 8% NaOH, beyond which degradation was found to be marginal. There was a marginal drop in the crystallinity index of hemp fiber while sisal, jute, and kapok fibers showed a slight increase in crystallinity at caustic soda concentration of 0.8–30%. FTIR showed that kapok fiber was found to be the most reactive followed by jute, sisal, and then hemp fiber. SEM showed a relatively smooth surface for all the untreated fibers; however, after alkalization, all the fibers showed uneven surfaces. These results show that alkalization modifies plant fibers promoting the development of fiber–resin adhesion, which then will result in increased interfacial energy and, hence, improvement in the mechanical and thermal stability of the composites. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 84: 2222–2234, 2002     

Simultaneous free radical polymerization and acidic polycondensation of acrylamide—formaldehyde resin on jute fabric

Acid catalyzed grafting, polycondensation, and crosslinking of acrylamide—formaldehyde (AMF) resin and simultaneous free radical graft copolymerization of the resin moieties on jute fabric were studied using a combination of MgCl₂ and K₂S₂O₈, respectively, as the (dual) catalyst system. Resin application and finish on jute fabric were accomplished by padding at room temperature, drying at 80°C, and polymerization and curing at 150°C. Changes in chemical structure and surface morphology of jute fiber on resin treatment were examined by Fourier transform infrared (FT-IR) spectroscopy and scanning electron microscopy (SEM), respectively. Application of 8% spectroscopy and scanning electron microscopy (SEM), respectively. Application of 8% AMF resin under the dual catalyst system in appropriate doses produced the most improved balance in the properties of jute fabric, including tenacity, modulus, breaking extension, stiffness, crease recovery angle, fiber shedding, moisture regain, and dyeability. Analysis indicated that all the major constituents of jute, namely, α-cellulose, hemicellulose, and lignin reacted with the AMF resin system and that the resin finish turned jute thermally more stable. Effects of different degrees of removal of lignin and hemicellulose from jute on its AMF resin uptake were also studied and reported. © 1997 John Wiley & Sons, Inc.     

Preparation and properties of successive alkali treated completely biodegradable short jute fiber reinforced PLA composites

The natural fiber reinforced biodegradable polymer composites were prepared with short jute fiber as reinforcement in PLA (Poly lactic acid) matrix. The short jute fiber is successively treated with NaOH at various concentrations (5%, 10%, and 15%) and H₂O₂. The composites were prepared with untreated and treated short jute fibers at different weight proportions (up to 25%) in PLA and investigated for mechanical properties. The results showed that the composite with successive alkali treated jute fiber at 10% NaOH and H₂O₂ with 20% fiber loading has shown 18% higher flexural strength than neat PLA and untreated jute/PLA composite. The flexural modulus of the composite at 25% fiber loading was 125% and 110% higher than that of composites with untreated fibers and neat PLA, respectively. The impact strength of composite with untreated fibers at higher fiber weight fraction was 23% high as compared to neat PLA and 26% high compared to composite with treated fibers. The water absorption was more for untreated jute/PLA composite at 25% fiber loading than all other composites. The composite with untreated fibers has high thermal degradation compared with treated fibers but lower than that of pure PLA matrix. The enzymatic environment has increased the rate of degradation of composites as compared to soil burial. Surface morphology of biodegraded surfaces of the composites were studied using SEM method. POLYM. COMPOS., 37:2160–2170, 2016. © 2015 Society of Plastics Engineers     

Alkali treatment of jute fibers: Relationship between structure and mechanical properties

The mechanical properties of tossa jute fibers were improved by using NaOH treatment process to improve the mechanical properties of composites materials. Shrinkage of fibers during this process has significant effects to the fiber structure, as well as to the mechanical fiber properties, such as tensile strength and modulus. Isometric NaOH‐treated jute yarns (20 min at 20°C in 25% NaOH solution) lead to an increase in yarn tensile strength and modulus of ∼ 120% and 150%, respectively. These changes in mechanical properties are affected by modifying the fiber structure, basically via the crystallinity ratio, degree of polymerization, and orientation (Hermans factor). Structure–property relationships, developed for cellulosic man‐made fibers, were used with a high correlation factor to describe the behavior of the jute fiber yarns. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 71: 623–629, 1999     

Surface treatment of cellulose fibers with methylmethacrylate for enhanced properties of in situ polymerized PMMA/cellulose composites

Cellulose micro/nanofibers (CNF), prepared from jute fibers were surface treated with methyl methacrylate (MMA) for better dispersion into poly methyl methacrylate (PMMA) matrix. PMMA/cellulose composites were prepared by in situ suspension polymerization technique. The surface treatment of CNF was confirmed by Fourier transform infrared spectroscopy (FTIR) and Nuclear magnetic resonance (NMR) analysis. MMA‐treated cellulose micro/nanofibers (MCNF) demonstrated improved affinity and dispersion in MMA monomer as well as in the PMMA/cellulose composites. Thermal properties of the cellulose composites were analyzed by differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). The glass transition temperature (T_g) of PMMA increased by nearly 19°C in the in situ cellulose composites compared to that of unreinforced PMMA as indicated by DSC. TGA showed increased thermal stability of the cellulose composites. Enhanced tensile properties as well as significantly lower moisture uptake were observed in the in situ prepared PMMA/cellulose composites. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 39808.     

Esterified PVA-lignin resin by maleic acid applicable for natural fiber reinforced composites

This article reports an esterified polyvinyl alcohol (PVA)-lignin resin that is applicable for natural fiber reinforced polymer composites. To meet the requirement for the composites, a biopolymer-based resin is necessary, which should well interact with the natural fiber with good waterproof behavior. By mimicking the relationship between cellulose, lignin and hemicellulose in wood, the esterified PVA-lignin resin with maleic acid is provided. The preparation and characterization of the environment-friendly resin are illustrated in this article. 180 °C of esterification reaction temperature and 40% of maleic acid contents are shown to be an optimum condition for the preparation of the resin. The esterified PVA-lignin resin exhibits 13, 31, and 55% increase of its tensile strength, toughness, and failure strength, respectively. The water contact angle of the esterified PVA-lignin resin is improved from 0 to 57°. The prepared resin is originally thermoplastic composite and it turned to be a thermoset resin by the esterification reaction at 180 °C, which is beneficial for composite processing. The developed resin is applicable for environment-friendly and high strength-natural fiber reinforced polymer composites. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020 , 137, 48836.     

Enzyme‐mediated surface modification of jute and its influence on the properties of jute/epoxy composites

Surface modification of jute fibers is necessary to improve the adhesion and interfacial compatibility between fibers and resin matrix before using fibers in polymer composites. In this study, dodecyl gallate (DG) was enzymatically grafted onto the jute fiber by laccase to endow the fiber with hydrophobicity. A hand lay‐up technique was then adopted to prepare jute/epoxy composites. Contact angle and wetting time measurements showed that the surface hydrophobicity of the jute fabric was increased after the enzymatic graft modification. The water absorption and thickness swelling of the DG‐grafted jute fabric/epoxy composite were lower than those of the other composites. The tensile and dynamic mechanical properties of the jute/epoxy composites were enhanced by the surface modification. Scanning electron microscopy images revealed stronger fiber–matrix adhesion in composites with modified fibers. Therefore, the enzymatic graft modification increased the fiber–matrix interface area. The fiber–matrix adhesion was enhanced, and the mechanical properties of the composites were improved. POLYM. COMPOS., 38:1327–1334, 2017. © 2015 Society of Plastics Engineers     

Comparison of the structures and properties of Lyocell fibers from high hemicellulose pulp and high α‐cellulose pulp

Lyocell fibers were produced from a cheap pulp with a high hemicellulose content and from a conventional pulp with a high α‐cellulose content. The mechanical properties, supermolecular structure, fibrillation resistance, and dyeing properties as well as the fibril aggregation size of the high hemicellulose Lyocell fiber and high α‐cellulose Lyocell fiber were compared. The results showed that the high hemicellulose spinning solution could be processed at a higher concentration, which improved the mechanical properties and the efficiency of the fiber process. Compared with the high α‐cellulose Lyocell fiber, the high hemicellulose Lyocell fiber had better fibrillation resistance and dyeing properties. Therefore, it is feasible that this cheap pulp with a high hemicellulose content can be used as a raw material for producing Lyocell fibers. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008