Vinyl-ester-participated transesterification and curing on the physicochemical behavior of Coir-IV

In this article, we report the transesterification of coir with n-Butyl acrylate (BA) and methyl acrylate (MA) under appropriate reaction conditions using NaOH and/or pyridine (Py) as catalyst. The modified vinylog coir was subsequently cured with benzoylperoxide (BPO) in acetone at 50–60°C. The modified fibers were characterized by Fourier transform infrared (FTIR) spectroscopy. Transesterification and curing of transesterified coir lowered the percentage of moisture regain and imparted improved tensile strength and resistance to common chemical reagents. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 64: 2283–2291, 1997     

Effect of chemical modification on FTIR spectra. I. Physical and chemical behavior of coir

Coir fibers were chemically modified through alkali treatment, and crosslinking with formaldehyde, para-phenylene diamine, phthalic anhydride, and combined crosslinking-cyanoethylation reactions in appropriate solvent and catalyst. The parent and chemically modified coir were characterized by FTIR spectra. The percent moisture regain, tensile strength, and behavior toward some chemical reagents (solubility %) of parent and chemically modified fibers have also been evaluated. The modified fibers showed significant hydrophobicity, improved tensile strength, and good chemical resistance. © 1995 John Wiley & Sons, Inc.     

Effect of chemical modifications on FTIR spectra. II. Physicochemical behavior of pineapple leaf fiber (PALF)

This article highlights chemical modifications like alkali treatment, dinitrophenylation, benzoylation, and benzoylation-acetylation carried out on an pineapple agrowaste leaf fiber (PALF). The parent and chemically modified PALF were characterized by FTIR spectra, pH measurement, and detection of nitrogen. The percent moisture regain (extent of hydrophobicity), mechanical strength, and chemical inertness of parent and chemically modified fibers were evaluated. The modified fibers showed significant hydrophobicity, improved mechanical strength, and moderate chemical resistance. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 64: 2119–2125, 1997     

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     

Degradation Studies of Thermoplastics Composites of Jute Fiber–Reinforced LDPE/Polycaprolactone Blends

This article reports the fabrication, properties, and degradation studies of jute fiber–reinforced thermoplastic polymers. One of the non-traditional outlets of jute fiber is in the area of fiber-reinforced composites. However, the major drawback associated with the application of jute fiber for this purpose is its high moisture regain. To impart hydrophobicity to the fibers and to concomitantly increase interfacial bond strength, which is a critical factor for obtaining better mechanical properties of composites, jute fibers were treated with benzoylchloride, Y-glycidoxytrimethoxysilane, and neo-alkoxy-tri(N-ethylenediamino)ethyltitanate. Such a treatment resulted in an increase in the diameter and denier of the treated fibers, and deterioration in the mechanical properties was observed. SEM studies revealed an increase in surface roughness after titanate and alkali treatment, which in turn increases interfacial bond strength. A series of low-density polyethylene (LDPE) blends with 5–20% (w/w) of poly(e-caprolactone) (PCL) and with/without treated and untreated jute fibers were prepared by using a single-screw extruder. LDPE modified by blending with PCL (80:20, wt/wt) was used as a thermoplastic matrix. Composites were fabricated by using 1-cm-long jute fibers; the weight fraction of unmodified fibers, silane-treated fibers, and titanate-treated fibers was varied from 0.05 to 0.13. An increase in weight fraction of fibers resulted in an increase in tensile strength and modulus and decrease in elongation at break. Thin sheets and dumbbells were used for enzymatic degradation tests. The degradation of the material was monitored by weight change and loss of mechanical properties. The enzymatic degradation in the presence of Pseudomonas cepacia lipase gave appreciable weight loss in PCL and blended materials.     

Comparative Studies of Some Physico‐mechanical Properties of Alkali and Diazonium Salts‐Treated Jute Fiber

Abstract

The effect of diazonium salts and alkali on some physico‐mechanical properties, viz, tensile strength, tenacity, elongation at break, moisture regain, shrinkage, loss in weight, etc. of jute fiber has been studied. The tensile strength, tenacity, elongation at break, and moisture regain properties of the treated (dyed) fiber are found lower in comparison with those of raw (control) fiber. However, higher tensile strength and tenacity of the diazonium salts‐treated jute fiber are observed in comparison with those of the alkali‐treated fiber. The nature of the shades developed on jute fiber is also reported.     

Sorption behavior and crystallinity of jute fiber at higher alkali treatments

Moisture regain of jute fiber was studied at different alkali concentrations and temperatures. It was found that the moisture regain increased up to 4.5N alkali treatment and then leveled off. Variation in swelling temperature had no significant effect on moisture regain. Amorphous fraction calculated from Valentine's equation using sorption ratio was compared with infrared crystallinity. The accessibility was increased with decreasing crystallinity in alkali-treated jute fiber, where as in cyanoethylated jute fiber it increased with increasing the degree of cyanoethylation.     

Novel jute yarns grafted with methyl methacrylate

This research work involves graft copolymerization of jute fibers with methyl methacrylate (MMA), initiated by cerric ions, and optimization of the grafting parameters as a function of different polymerization conditions. It was considered to produce a hydrophobic jute fiber with enhanced properties. To achieve this, the effects of monomer concentration and grafting percentage on FTIR spectra, mechanical properties, moisture regain, oil‐adsorption capacity, and surface morphology were investigated, and optimum percentage of MMA with reasonable properties was suggested. The results indicated that cerric ions initiated graft copolymerization of MMA onto jute with 30% of weight of monomers at optimum conditions of acid concentration and temperature. The FTIR studies proposed grafting of MMA onto jute at hydroxyl groups. The results showed that mechanical properties and moisture regain (%) of samples decrease with increasing of graft percentage. The most remarkable features of this investigation include reducing oil‐adsorption capacity with increasing of lipophilic monomer percentages after one limitation. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

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     

Chemical modification of tussah silk with acid anhydrides

Tussah silk fibroin was chemically modified by acylation with aliphatic, aromatic, and hydrophobic acid anhydrides. The tussah silk fibers were pretreated by immersing them in a lithium thiocyanate (LiSCN) solution and then acylated in dimethylformamide (DMF) at elevated temperatures. Using this method, acylated tussah silk fibers with weight gains of 8–22% could be obtained. The pretreatment with LiSCN was necessary to promote the acylation. Without it, the reaction did not proceed. The optimum temperature and reaction time of the pretreatment was 55°C and 60 min, respectively. When examining the physical properties and the thermal behavior of both pretreated and acylated tussah silk, it was found that the mechanical properties and the position of the major DSC endothermic peak remained unchanged, regardless of pretreatment and acylation. The moisture regain of the pretreated tussah silk increased slightly while the moisture regain of the acylated silk decreased linearly with increasing weight gain. The chemical modification allows for a wide control of the tussah silk fiber's properties, making it possible to use tussah silk for the development and production of novel textile and biomaterials. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 78: 382–391, 2000     

Effect of Ultraviolet Radiation on the Mechanical and Dielectric Properties of Hessian Cloth/PP Composites with Starch

Hessian cloth (jute fabrics) reinforced poly(propylene) (PP) composites (45 wt% fiber) were prepared by compression molding and the mechanical properties were evaluated. Jute fabrics and PP sheets were treated with UV radiation at different intensities and then composites were fabricated. It was found that mechanical properties of the irradiated jute and irradiated PP-based composites were found to increase significantly compared to that of the untreated counterparts. Irradiated jute fabrics were also treated with aqueous starch solution (1–5%, w/w) for 2–10 min. Composites made of 3% starch-treated jute fabrics (5 min soaking time) and irradiated PP showed the best mechanical properties. Tensile strength, bending strength, tensile modulus, bending modulus and impact strength of the composites were found to improve 31, 41, 42, 46 and 84% higher over untreated composites. Water uptake, thermal degradation and dielectric properties of the resulting composites were also performed.     

Impact toughness,viscoelastic behavior,and morphology of polypropylene–jute–viscose hybrid composites

In this investigation, we studied the impact toughness and viscoelastic behavior of polypropylene (PP)–jute composites. In this study, we used viscose fiber as an impact modifier and maleated PP as a compatibilizer. The toughness of the composites was studied with conventional Charpy and instrumental falling‐weight impact tests. The composites’ viscoelastic properties were studied with dynamic mechanical analysis. The results show that the incorporation of viscose fibers improved the impact strength and toughness to 134 and 65% compared to those of the PP–jute composites. The tan δ peak amplitude also increased with the addition of the impact modifier and indicated a greater degree of molecular mobility. The thermal stability of the composites was evaluated with thermogravimetric analysis. The addition of 2 wt % maleated polypropylene (MAPP) to the impact‐modified composite improved the impact strength and toughness to 144 and 93%, respectively. The fiber–matrix morphology of the fracture surface and the Fourier transform infrared spectra were also studied to ascertain the existence of the type of interfacial bonds. Microstructural analysis showed the retention of viscose fibers in the composites compared to the more separated jute fibers. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 42981.     

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     

Physico-Mechanical and Degradation Properties of Gamma-Irradiated Biocomposites of Jute Fabric-Reinforced Poly(caprolactone)

Jute fabric-reinforced poly(caprolactone) biocomposites (30–70% jute) were fabricated by compression molding. Tensile strength, tensile modulus, bending strength, bending modulus and impact strength of the non-irradiated composites (50% jute) were found to be 65 MPa, 0.75 GPa, 75 MPa, 4.2 GPa and 6.8 kJ/m², respectively. The composites were irradiated with gamma radiation at different doses (50–1000 krad) at a dose rate of 232 krad/hr and mechanical properties were investigated. The irradiated composites containing 50% jute showed improved physico-mechanical properties. The degradation properties of the composites were observed. The morphology was evaluated by scanning electron microscope.     

Effect of steam pretreatment of jute fiber on dimensional stability of jute composite

Dimensional stability of fiber board from lignocellulosic materials is a prime concern for efficient utility of the product. A number of methods have been used to improve the dimensional stability. These include the application of coating, oil, and wax treatments and chemical modification of lignocellulosic materials. A new process has been developed to minimize irreversible swelling (i.e., permanent fixation of compressive deformation of wood fiber through a hygrothermal treatment using in‐built steam from moisture of compressed fiber at high temperature). This process has been applied on jute fiber for the evaluation of dimensional stability and vis‐à‐vis the mechanical and thermal properties of the fiber board made from the modified jute fiber. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 76: 1652–1661, 2000     

Studies on the Effect of Hydroxy Benzene Diazonium Salts on Physico-Mechanical Properties of Jute Fiber

Jute fiber was treated with three different hydroxy benzene diazonium salts in acidic and basic media. The formation of coupling with lignin in the polymer system was observed by the infrared spectra and nitrogen content estimation. The physico-mechanical properties, viz., tensile strength, tenacity, elongation at break, moisture regain, shrinkage, and loss in weight of jute fiber were studied. The tensile strength, tenacity, and moisture regain properties of the treated fiber were found lower in comparison to those of raw (control) fiber. However, higher tensile strength and tenacity of the fiber treated with ortho hydroxy benzene diazonium salts in comparison to fiber treated with meta hydroxy benzene diazonium salts were observed. The tensile strength and tenacity of the fiber treated with meta hydroxy benzene diazonium salts were higher than those of the fiber treated with para hydroxy benzene diazonium salts. The elongation at break of the treated fiber is found greater than that of the raw fiber. The fiber treated in basic media shows higher tensile strength than that treated in acidic media. The formation of metallated azo complex compound on jute fiber was observed by infrared spectra. The nature of the shades developed on jute fiber was also reported.     

Decrystallization of jute by cyanoethylation

The cyanoethylation of jute fiber was studied at different reaction conditions. Moisture regain decreased significantly on cyanoethylation. Introduction of 5–6% nitrogen content on the fiber minimized the moisture regain capacity to 2.8%. A further increase in the nitrogen content increased the moisture regain. The effect of cyanoethylation on infrared absorption was studied. The absorbance curves of O? H and C? H stretching frequencies are parabolic in nature, whereas β-glycosidic and C? H bending absorption curves are almost linear with an increase in the degree of substitution. The cellulosic transition was indicated by the lattice conversion ratio, which showed an increase along with the degree of cyanoethylation. © 1993 John Wiley & Sons, Inc.     

Long jute fiber‐reinforced polypropylene composite: Effects of jute fiber bundle and glass fiber hybridization

Two types of long jute fiber pellet consisting of twisted‐jute yarn (LFT‐JF/PP) and untwisted‐jute yarn (UT‐JF/PP) pellets are used to prepare jute fiber–reinforced polypropylene (JF/PP) composites. The mechanical properties of both long fiber composites are compared with that of re‐pelletized pellet (RP‐JF/PP) of LFT‐JF/PP pellet, which is re‐compounded by extrusion compounding. High stiffness and high impact strength of JF/PP composites are as a result of using long fiber. However, the longer fiber bundle consequently affects the distribution of jute fiber. The incorporation of 10 wt % glass fibers is found to improve mechanical properties of JF/PP composites. Increasing mechanical properties of hybrid composites is dependent on the type of JF/PP pellets, which directly affect the fiber length and fiber orientation of glass fiber within hybrid composites. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41819.     

Synthesis and characterization of ternary‐copolymer of soluble fluorinated polyimides based on 1,4‐bis (4‐amino‐2‐trifluoromethylphenoxy) benzene

A series of novel ternary‐copolymer of fluorinated polyimides (PIs) were prepared from 1,4‐bis(4‐amino‐2‐trifluoromethylphenoxy)benzene (pBATB), commercially available aromatic dianhydrides, and aromatic diamines via a conventional two‐step thermal or chemical imidization method. The structures of all the obtained PIs were characterized with FTIR, ¹H‐NMR, and element analysis. Besides, the solubility, thermal stability, mechanical properties, and moisture uptakes of the PIs were investigated. The weight‐average molecular weight (M_w) and the number‐average molecular weight (M_n) of the PIs were determined using gel‐permeation chromatography (GPC). The PIs were readily dissolved not only in polar solvents such as DMF, DMAc, and NMP, but also in some common organic solvents, such as acetic ester, chloroform, and acetone. The glass transition temperatures of these PIs ranged from 201 to 234°C and the 10% weight loss temperatures ranged from 507 to 541°C in nitrogen. Meanwhile, all the PIs left around 50% residual even at 800°C in nitrogen. The GPC results indicated that the PIs possessed moderate‐to‐high number‐average molecular weight (M_n), ranging from 9609 to 17,628. Moreover, the polymer films exhibited good mechanical properties, with elongations at break of 8–21%, tensile strength of 66.5–89.8 MPa, and Young's modulus of 1.04–1.27 GPa, and low moisture uptakes of 0.54–1.13%. These excellent combination properties ensure that the polymer could be considered as potential candidates for photoelectric and microelectronic applications. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Polyacrylonitrile (PAN)-grafted jute fibres: Some physical and chemical properties and morphology

Grafting of polyacrylonitrile (PAN) on (dewaxed and bleached) jute fibres was done by aqueous polymerization of acrylonitrile (AN) in the presence of the fiber samples employing a sodium periodate (IO₄^?) and copper sulfate (Cu²⁺) combination as the initiator. Effect of PAN grafting to different extents on X-ray crystallinity, tensile properties, thermal behavior, whiteness index, dyeability, light-fastness rating, and moisture regain properties of the fiber samples were studied and analyzed. Their rot resistance, determined by a standard soil burial test, were also examined and compared. Twenty to thirty percent PAN-grafting was found to impart a most desirable balance of physical properties including fiber strength and modulus, moisture regain, whiteness index, and light-fastness rating. PAN grafting also makes the otherwise nonresistant jute fiber significantly rot-resistant. Morphology of the different fiber samples as studied and compared using scanning electron microscopy indicates that PAN grafting occurs on surfaces and intercellular regions as well as within the lumens of the multicellular jute fibers. © 1994 John Wiley & Sons, Inc.