IFSS, TG, FT-IR spectra of impregnated sugar palm (Arenga pinnata) fibres and mechanical properties of their composites

This study aimed to investigate the effect of resin impregnation on the interfacial shear strength (IFSS), thermogravimetric (TG) and fourier transform infrared (FT-IR) of sugar palm (Arenga pinnata) fibres. In addition, the effect of resin impregnation on the mechanical properties of sugar palm fibre reinforced unsaturated polyester (UP) composites was also studied. The fibres were impregnated with UP via vacuum resin impregnation process at a pressure of 600 mmHg for 5 min. Composites of 10, 20, 30, 40 and 50 % fibre loadings were fabricated and tested for tensile and flexural properties. It was observed that the impregnation process caused the fibres to be enclosed by UP resin and this gave a strong influence to the increase of its interfacial bonding by the increase of its IFSS from single fibre pull-out test. It was also observed with TG and FT-IR spectra that the impregnated fibre had lower moisture uptake than the control and there was no significant increase in thermal stability of the impregnated fibre. The sequence of fibre decomposition started from the evaporation of moisture, hemicelluloses, cellulose, lignin and finally ash content and the presence of these components were proven by FT-IR spectra. For the composite specimens, due to the high interfacial bonding of the impregnated fibre and the matrix, the impregnated composites showed consistently higher tensile strength, tensile modulus, elongation at break, flexural strength, flexural modulus and toughness than the control samples. It was also observed that 30 % fibre loading gave optimum properties.     

Mechanical properties of hybrid glass/sugar palm fibre reinforced unsaturated polyester composites

A research has been carried out to investigate the mechanical properties of composites made by hybridizing sugar palm fibre (Arenga pinnata) with glass fibre into an unsaturated polyester matrix. Hybrid composites of glass/sugar palm fibre were fabricated in different weight ratios of strand mat glass fibres: sugar palm fibres 4:0, 4:1, 4:2, 4:3, 4:4, and 0:4. The hybrid effects of glass and sugar palm fibre on tensile, flexural and impact properties of the composites were evaluated according to ASTM D5083, ASTM D790 and ASTM D256 respectively. Results have been established that properties of hybrid glass/sugar palm composites such as tensile strength, tensile modulus, elongation at break, toughness, flexural strength, flexural modulus and impact strength are a function of fibre content. The failure mechanism and the adhesion between fibres/matrix were studied by observing the scanning electron micrographs of impact fracture samples. In general, the incorporation of both fibres into unsaturated polyester matrix shows a regular trend of increase in the mechanical properties.     

Structural FTIR analysis and thermal characterisation of lyocell and viscose-type fibres

The microstructure and thermal properties of lyocell and other regenerated cellulose fibres (viscose and modal) were analysed using DSC, TG and FTIR. The FTIR spectral analysis showed that lyocell is the most crystalline fibre and is composed principally of crystalline cellulose II and amorphous cellulose. Likewise, the thermal analysis showed that lyocell has a higher thermal stability than viscose and modal fibres, as the difference between the onset temperature for its decomposition process was as high as 20 °C.     

Study of cellulosic fibres morphological features and their modifications using hemicelluloses

The microfibrilar structure and the morphology of the fibre are some of the most important characteristics that determine fibre performance during yarn making. This article is focused on understanding of morphological features of manmade cellulosic fibre and exploring an alternate way to alter fibre morphology. It is observed that though the chemical nature of different types of cellulose fibres viz. viscose, modal and lyocell is same; different processing routes lead to different cross-section and morphologies of fibres which leads to their characteristic properties and spinning behavior. A novel way is attempted to alter the fibre morphology of viscose fibre by changing the fibre regeneration kinetics and molecular weight distribution through addition of low molecular weight and branched structured hemicelluloses in spinning dope. Addition of hemicelluloses in the spinning dope prior to spinning and regeneration of viscose fibres is found to alter the morphology of the fibres without affecting tensile properties of the fibres.     

Thermal degradation and decomposition of jute/vinylester composites

Thermal analysis of jute fibre reinforced vinylester resin with 30 vol% of fibre were performed by TG/DTG under dynamic conditions. The fibres were treated with alkaline solution at different temperatures and the final composition (cellulose, hemicellulose and lignin) of the fibre was determined by chemical analysis. Apparent activation energies were determined using a variety of conventional thermogravimetric methods. Two peaks were found in the composite differential curves: the first peak close to 327 and the second peak at 408°C. The apparent activation energy values for the second peak decreased when fibre were treated. The addition of the jute fibres produced a slightly decrease in the thermal stability of the composites.     

Pyrolytic behaviour of different biomasses (angiosperms) (maize plants,straws, and wood) in low temperature pyrolysis

The thermal degradation of agricultural products and by-products (two kinds of maize plants, wheat, and barley straw) has been investigated by means of thermogravimetric/mass spectrometric analysis at heating rates from 1 to 10 °C/min. Large differences were found in the pyrolytic behaviour of the untreated samples, mainly caused by the high content of inorganics (ash content of about 4–6 wt%). These differences could be reduced by washing the samples with cold water. A kinetic model based on the formal kinetic parameters for the pyrolysis of the main components (hemicelluloses, lignin, and cellulose) and their degradable amounts was applied. To reduce the complexity of the model, only largely ash reduced samples were used. The formal kinetic parameters for the main components of barley straw and Gavott were individually determined. Although, different monomeric lignin degradation products were found for the angiosperms of grassy biomass in comparison to woody biomass, the formal kinetic parameters for lignin degradation are similar. The transferability of the formal kinetic parameters was successfully tested by applying them to a different straw type (wheat) and to a different maize cultivar (Doge) using the results of the biochemical analysis for the main components (hemicelluloses, lignin, and cellulose).     

Chemical and thermal analysis of the biopolymers in thyme (Thymus vulgaris)

Thyme (Thymus vulgaris) has been known, long time ago, for its aromatic properties. It contains essential oils and polymers such as cellulose (mixture of hemicellulose and cellulose) and lignin. The thyme, studied in this work, was gathered from the same place, in the period from November 1999 to October 2000. The chemical analysis (water, total ash, essential oils, extractive substances, cellulose, holocellulose and lignin) can be used roughly in the characterisation of the four periods that correspond to the four seasons of the year. The cellulose level was found to be more than lignin level in the wet periods (growth of the plant). The opposite was found in the dry periods. The total ash and essential oil levels were found to be high during the period of high pluviometry. The thermal decomposition of cellulose and holocellulose was found to fit well with the first-order kinetics. The activation energy, under air flow, was 185 and 196 kJ mol⁻¹ for cellulose and holocellulose, respectively. The maximum decomposition rate and thermal analysis heating rate of lignin were found to have a direct linear relationship.     

Anisotropy of cell wall polymers in branches of hardwood and softwood: a polarized FTIR study

The mechanical and physical properties of wood fibres are dependent on the organisation of their constituent polymers (cellulose, hemicellulose and lignin). Fourier Transform Infrared (FTIR) microscopy was used to examine the anisotropy of the main wood polymers in isolated cell wall fragments from branches of maple and Serbian spruce. Polarised FTIR measurements indicated an anisotropy, i.e. orientation of the cellulose microfibrils that was more or less parallel to the longitudinal axis of the cell wall. The hemicelluloses, glucomannan and xylan appeared to have a close link to the orientation of the cellulose and, thus, an orientation more parallel to the axis of the cell wall. An important result is that, in both maple and spruce samples, lignin was found to be organised in a parallel way in relation to the longitudinal cell wall axis, as well as to the cellulose. The results show that, despite the different lignin precursors and the different types of hemicelluloses in these two kinds of wood, lignin has a similar orientation, when it comes to the longitudinal axis of the cell wall.     

Date palm fibre filled recycled ternary polymer blend composites with enhanced flame retardancy

Flammability of recycled polypropylene (PP)/low density polyethylene (LDPE)/high density polyethylene (HDPE) ternary blends containing date palm fibres is investigated in this study. Melt blending is used for the composite preparation and the palm fibres induce good mechanical strength to the blend composites. The effect of flame retardant magnesium hydroxide, is studied through the limiting oxygen index analysis and cone calorimeter studies. Morphology of the palm fibres in presence of fire retardant reveals interesting facts of base hydrolysis. Since the polymers used are recycled ones and the fibres are obtained from the date palm leaves, the whole composite manufactured stands as low cost, less energy consuming and environmental friendly. Though the flame retardant reduced the mechanical properties, the palm fibres strengthened the whole composite thus helping to achieve the flame retardancy and mechanical properties simultaneously. Flame retardancy is correlated with the thermal degradation and thermal conductivity of the blend fibre composites as well.     

Extraction and characterization of new natural lignocellulosic fiber Cyperus pangorei

This research is focused on the study of the physical, chemical, mechanical, and thermal properties of a newly identified natural stem fiber, Cyperus pangorei. The chemical composition of Cyperus pangorei fibers (CPF) such as cellulose, lignin, ash, moisture, and wax contents was evaluated. Besides these, the fiber density was determined and the apparent diameter was measured using an optical microscope. Further, tensile, thermal, XRD, and FT-IR studies were performed to evaluate the suitability of the fiber as a reinforcement. The surface topography of CPF was analyzed using scanning electron microscopy (SEM). Encouraging properties such as increased stiffness, fiber texture, and higher thermal stability suggest the suitability of CPF as reinforcement in polymer matrices.     

Thermal properties of biocomposites

Thermal properties of new biocomposites prepared from modified starch matrix reinforced with natural vegetable fibres were studied. DSC and TG methods were applied to study thermal behaviour of biocomposites. Biocomposites were obtained in the laboratory twin-screw extruder. Two kinds of natural fibres were used, i.e. flax and cellulose in the amount of 0–40 mass%. DSC curves of biocomposites reveal glass transition temperature, attributed to the amorphous nature of the plasticized starch matrix. In general, incorporating natural fibres into modified starch matrix leads to an increase in glass transition temperature. Thermal degradation of modified starch matrix and cellulose reinforced biocomposites proceeds in three steps, whereas the degradation process of flax reinforced biocomposites occurs in two steps. For unreinforced matrix as well as for all biocomposites, regardless of type and amount of reinforcement, the major mass loss is observed at the temperature above 300°C. The increase in thermal stability with introduction of natural fibre is observed for both flax and cellulose reinforced biocomposites.     

Effect of pulp composition on the characteristics of residuals in CMC made from such pulps

Four different spruce sulphite pulp samples were used for the preparation of carboxymethylcellulose (CMC). The characteristics of the unreacted fibre and particle residuals obtained in the CMC-preparation were used to establish a correlation between the hemicellulose in the pulp and the intrinsic viscosity, i.e.,␣cellulose chain length and the occurence of unreacted residuals. It was shown that the residual particles in the CMC consisted of fibres, fibre fractions and gel particles of different degrees of substitution. The results suggested that pulps with long cellulose chains, i.e., pulps with high intrinsic viscosities, resulted in particles that were more substituted and more swollen. These pulps also resulted in more substituted hemicelluloses in the CMC and more substituted residuals. It was also suggested that galactoglucomannan in the cellulose pulps is favourable for the swelling which results in more substituted hemicelluloses in the CMC and more swollen residuals. The amount of residuals was influenced mainly by the characteristics of the cellulose in the pulp. It is therefore believed that a combination of high viscosity and a suitable combination of hemicelluloses is the most favourable way of eliminating the occurrence of undissolved residuals in CMC.     

Cellulose nano-particles from Pandanus: viscometric and crystallographic studies

Pandanus utilis a plant abundant throughout Kerala, India has been used as a source to isolate nano-particles. The fibres were extracted from Pandanus plant by biological natural retting. Extracted fibres were dried, ground and treated with 5 % NaOH followed by bleaching using 5 wt % hypochlorite solution. Bleached cellulose was hydrolysed using sulphuric acid. After centrifugation, suspension was freeze dried. Effect of Acid concentration, temperature and time of hydrolysis on the isolation of cellulose nanoparticles was studied. FESEM images of cellulose showed the presence of spherical nano-particles. Dynamic light scattering revealed homogeneous dispersion of nano-particles. Degree of polymerisation of cellulose was determined viscometrically using cupriethylene-diamine as solvent. Removal of lignin and hemicelluloses was confirmed from FTIR spectra. X-Ray diffractograms of powdered fibre, bleached cellulose and nano-cellulose were compared. Using peak height method and peak de-convolution method, crystallinity indices were determined. Using Scherrer equation crystallite size was calculated and it further confirmed that particles are of nanometre size.     

Crystallinity changes in lyocell and viscose-type fibres by caustic treatment

One of the most important treatments performed on cellulosic fibres to improve properties such as dimensional stability, tensile strength and lustre, is mercerisation. The aim of this work was to study the crystallinity, accessibility and unit cell structure changes occurring in three types of regenerated cellulose fibres (lyocell, modal and viscose) that were mercerised with caustic soda solutions of different concentrations. Differences were observed between the behaviour of the viscose type fibres (viscose and modal) and that of the lyocell fibres. For the viscose type fibres, the proportion of crystalline regions increased at low alkali concentrations, while for lyocell fibres a decrease in crystallinity was observed. In all three fibres there was a transformation from cellulose II to amorphous cellulose. While for lyocell the transformation was partial, the modal and in particular the viscose fibres showed a complete transformation, and the swelling agent caused the fibre to dissolve at high caustic concentrations.     

Jute as raw material for the preparation of microcrystalline cellulose

Cellulose was extracted at a yield of 59.8% from jute fibres based on the formic acid/peroxyformic acid process at an atmospheric pressure. The amounts of dissolved lignin and hemicelluloses were determined in the spent liquor. The results showed that the spent liquor contained 10.6% total sugars and 10.9% lignin (based on jute). Microcrystalline cellulose (MCC) was further prepared from the jute cellulose based on the acid hydrolysis technique. A very high yield, 48–52.8% (based on the jute raw material) was obtained. The acid hydrolysate of cellulose contained 2.7% glucose and 0.2% xylose. The MCC samples obtained from two different conditions, one at a low acidity and the other at a high acidity, were characterized by means of Thermo Gravimetric Analysis, Fourier Transform Infrared, X-ray detraction, Scanning Electron Micrograph, and Transmission Electron Micrograph techniques.     

Mechanical Properties of Regenerated Cellulose Fibres for Composites

Summary: A broad variety of regenerated cellulose fibres was subjected to single fibre tensile tests in order to determine the modulus of elasticity, tensile strength, and failure strain. The results were compared to glass fibres and flax fibres, which are considered the most important technical and natural fibres, respectively. With regard to their modulus of elasticity and tensile strength, regenerated cellulose fibres showed clearly lower values than glass fibres, even when their low density was taken into account. The average modulus of elasticity and tensile strength of regenerated cellulose fibres was also lower than the values measured for flax fibres, but when variability was considered, both fibres performed similarly. In terms of interfacial shear strength with polypropylene, lyocell fibres performed significantly less well than sized glass fibre and ramie fibre. The most important difference between regenerated cellulose fibres and both glass and flax fibres is their high failure strain and thus high work to fracture. The high work to fracture of regenerated cellulose fibres makes them particularly useful for composite applications where high fracture toughness is required.     

The influence of chemical treatment on the mechanical properties of windmill palm fiber

Bleached palm fiber without lignin, alkalized palm fiber without hemicelluloses and raw windmill palm fiber were prepared. Then, the chemical composition and the mechanical properties of the windmill palm fiber were investigated. Scanning electron microscopy, Fourier transform infrared spectroscopy and Raman microscopy were employed to characterize the structure and chemical composition. A universal material tester, nanoindentation and dynamic mechanical analysis were used to study the mechanical property of these samples. According to the results, bleach treatment removed most of the silica bodies as well as the lignin, smoothed the fiber surfaces and increased the hollowness to 50%. Alkali treatment removed most of the hemicelluloses, increased the surface roughness, and reduced the hollowness to 28%. Alkalized fibers have the highest tensile strength, elongation at break and elastic modulus, with values of 119.37 ± 27.21 MPa, 30.58 ± 5.87% and 10.75 ± 4.30 GPa, respectively. The raw material without treatment has the highest stiffness, while the alkalized samples are the most flexible fibers and sensitive to temperature.     

Surface treated cellulose fibres in flame retarded PP composites

Polypropylene-based composites were prepared containing non-treated and various treated cotton fibre and wood flakes. A correlation was observed among the fibre treatment and compounding parameters, mechanical and discoloration properties. The structural changes in fibres were demonstrated by Raman spectroscopic and DSC measurements. The possibility for forming cellulose fibre containing flame retardant composites was also investigated. The efficiency of various treatments on compounding, discoloration and mechanical properties enhance in the following order: no treatment < non ionic surfactant < reactive silicone segment containing non ionic surfactant < special silylation treatment. The best results obtained with the special silylation treatment were explained with the more organophilic character and by the thermal stability of the treated fibres. Cellulose fibre as a polyol-charring component and ammonium-polyphosphate together constitute a high performance intumescent flame retardant system in the PP matrix.     

Exploration on the characteristics of cellulose microfibers from Palmyra palm fruits

To obtain cellulose microfibers from Palmyra palm fruit fibers, a new succession of specific chemical treatments including acidified chlorination, alkalization, and acid hydrolysis have been developed. Cellulose microfibers obtained were characterized by different techniques. The chemical analysis indicated an increase in α-cellulose content and decrease in lignin and hemicellulose for the cellulose microfibers over raw fibers. Fourier transform infrared and ¹³C NMR spectra confirmed the removal of non-cellulosic (lignin and hemicellulose) components after chemical treatments. The X-ray diffraction results revealed that the cellulose I was partly transformed into cellulose II by chemical treatments and the crystallinity index of cellulose microfibers was significantly increased as compared to raw fibers owing to removal of non-cellulosic components. Thermogravimetric analysis results demonstrated that the thermal stability was enhanced noticeably for cellulose microfibers than for the raw fibers. The scanning electron micrographs illustrated cleaner and rough surfaces for the cellulose microfibers when compared to those of raw fibers.     

Destruction thermo-oxydante de certains materiaux fibreux cellulosiques et de leurs composants

The investigation of the oxidative thermal destruction of some new cellulose-type fibrous materials, namely poplar down and down of silkweed is described. The latter are characterized by a high content of amorphous components. The components of the fibres, cellulose, holocellulose, hemicelluloses and lignin, separated by extraction, have also been studied. From the experimental data, the compounds isolated from the original material could be classified according to their thermal stabilities. The influence of the molecular structure on the kinetic parameters of the oxidative thermal destruction has also been studied. The activation energies of the single steps of the thermal reaction have been estimated for each compound isolated.