Water Retting Process Research Articles

Tensile Properties of Unidirectional Kenaf Polypropylene Composite at Various Temperatures and Orientations

The development of bio-composites as biodegradable and renewable materials for sustainable technology are advantageous in creating a green and healthy environment. However, the application of natural fiber as a bio-composite material have been found to be restricted especially as it has lower thermal resistance in comparison to synthetic fiber. Therefore, the objective of this study is to investigate the influence of fiber orientations on the tensile properties at various tensile temperatures for unidirectional kenaf polypropylene (PP) composite. Samples were prepared by hot pressing process. In this study, kenaf long fibers that are produced from water retting process is use as a reinforcement agent while PP as a polymer in the composite fabrication. A tensile test was carried out at different temperatures (30°C, 60°C, 90°C, 120°C) for various orientations (0°, 45° and 90°). It was found that an increase of temperature will reduce the modulus and tensile strength where the highest reduction occurred between 60°C to 120°C and most significantly on the orientation of 45° and 90°, which is lower than pure PP. This concludes that the application of kenaf PP composite is optimum between room temperature with a cut-off temperature at 60°C.

Alkaline treatment and thermal properties of Napier grass fibres

This paper presents an overview of a natural fibre, namely Pennisetum purpureum, which is commonly known as Napier grass. This paper’s intention is to analyse Napier grass fibre to assess the effect of alkaline treatment on the tensile properties, thermal stability, and morphology of the fibres. These fibres were extracted by a water retting process from the internodes of Napier stems. The fibres were later subjected to alkaline treatments with NaOH at 5, 10, 15 and 20% concentrations for a period of 24 h at 25°C (RT). The tensile strength, thermal stability and crystallinity of the fibres were seen to upsurge upon conducting the alkaline treatments. Thus, the experimental results demonstrate that the 10% NaOH concentration has the strongest tensile test compared to untreated Napier grass fibre. The surfaces of the fibres after the treatment were observed with a scanning electron microscope (SEM), TM-3000. SEM investigation showed that the surfaces of the fibres become rougher after NaOH treatment. Moreover, from XRD, the amount of crystallinity is also higher in the 10% alkaline treated fibres, and DSC thermograms proved that they have better thermal stability. From this study, Napier grass fibres show potential to be used as reinforcing fibres in composite structures.

TENSILE PROPERTIES OF UNIDIRECTIONAL KENAF FIBER POLYPROPYLENE COMPOSITE

Over the last decade, awareness of environmental issues and the shortage of petroleum resources contribute to the important factors that encourage researchers to explore the potential use of natural fibers such as kenaf as reinforcement in fiber reinforced composites. The objective of this study was to investigate the effect of different processing condition (temperature, pressure and pressing time) on the tensile properties of unidirectional kenaf fiber polypropylene composite. Samples of composites were prepared by a hot pressing method. In this work, kenaf continuous long fibers from water retting process at 40%wt were aligned in parallel. Polypropylene (PP) in the form of pellets and powder had been used as a matrix. The results showed that, samples produced at temperature 2100C and pressure 5 MPa for 6 minutes hot pressing gives excellent tensile properties which 262% of improvement as compared to pure PP. This indicates that, kenaf fiber is suitable as reinforcement in polymer composite.

Mechanical properties of Napier grass fibre/polyester composites

The mechanical properties of Napier grass fibre-reinforced composites were characterised. Napier grass fibres were extracted through water retting process. The effect of alkali-treatment on the tensile properties and morphology of the fibres was investigated. The fibres were alkali-treated using NaOH solutions of various concentrations and subjected to single fibre testing. The morphology of the fibres was observed using scanning electron microscopy. The 10% alkali-treated Napier grass fibres yielded the highest strength. To fabricate the polymer composites, Napier grass fibre and polyester resin were used as the reinforcing material and polymer matrix, respectively. The tensile and flexural properties of the composites were studied. In general, up to a certain threshold value, the tensile and flexural strengths of the composites increased as the fibre volume fractions increased, following which, there was a reduction in strength. The maximum tensile and flexural strengths of the composites were obtained at 25% fibre loading.

Kenaf-Unsaturated Polyester Composite: The Effect of Different Retting Process of Kenaf Bast Fiber on the Mechanical Properties

Kenaf bast fiber reinforced unsaturated polyester composite was produced using kenaf bast fiber based on different retting process. There are two different retting method involved which are water and mechanical retting process. The composites were prepared by using hand lay-up method with different fiber loading (weight %) of 10, 15 and 20%. The mechanical test involved was tensile test and scanning electron microscope (SEM) was employed to investigate the fiber-matrix adhesion and fiber breakage. The result showed that the tensile properties of the composite increased as the fiber loading increased. Besides, the water-retted kenaf –UPE composites exhibited the highest mechanical properties as compared to mechanical-retted kenaf –UPE composites. While, the morphology analysis using SEM showed that water retted kenaf-UPE composite show better fiber distribution and better interfacial adhesion compared to mechanical retted kenaf-UPE composite.

Tensile and Flexural Strength of Untreated Napier Grass Fibre/Polyester Composites

This paper describes the experimental investigation of the tensile and flexural strength of untreated Napier grass fibre reinforced polyester composites. Napier grass fibres were extracted trough conventional water retting process and used as reinforcing materials in the polyester composite laminates. Tensile tests were then conducted for the composite specimens from the laminates at 25% fibre loading using the electronic extensometer setup to obtain the tensile properties. The results show significant differences in tensile strength between random short fibres laminates and random long fibrelaminates with the long fibres yield over 30 % higher in strength.Both the short and long fibre composites exhibits similar strength with short fibres having slightly higher flexural strength to long fibres The laminate also shows higher maximum strength compared to other commonly available natural fibre composites with almost 75 % improved in the maximum strength compared to the short kenaf fibre reinforced composites.

Effects of Alkaline Treatments on the Tensile Strength of Napier Grass Fibres

This paper presents the experiment test of the Napier grass fibres to determine the tensile strength of the Napier grass fibre. . Napier grass fibre is a natural source of fibre which is extracted from the internodes of Napier grass stems. Napier grass fibres were extracted trough conventional water retting process. However, the main disadvantages of natural fibres in composites are the poor compatibility between fibre and matrix and the relative high moisture absorption. These Napier grass fibre then undergoes alkaline chemical treatment using sodium hydroxide (NaOH) to improve the surface roughness and to minimize the water absorption into the cellulose. The treatment is conducted with different concentration of NaOH at 5%, 10%, 15% and 20% respectively. The single fibre tensile test was conducted using Instron micro tester. Based on the tests conducted, the results show that the fibre treated 10% concentrations yield the strongest tensile test compared to untreated Napier grass fibre.

Tensile Strength of Untreated Napier Grass Fibre Reinforced Unsaturated Polyester Composites

This paper describes the experimental investigation of the tensile strength of untreated Napier grass fibre reinforced polyester composites. Napier grass fibres were extracted trough conventional water retting process and used as reinforcing materials in the polyester composite laminates. Tensile tests were then conducted for the composite specimens from the laminates at 25% fibre loading using the electronic extensometer setup to obtain the tensile properties. The results show significant differences in tensile strength between random short fibres laminates and random long fibre laminates with the long fibres yield almost 45 % higher in the strength. The laminates also show higher maximum strength compared to other commonly available natural fibre composites with over 70 % increase in the maximum strength compared to the short kenaf fibre reinforced composites.

English

Five plant raw materials collected from South Eastern part of Nigeria were used for biofibre extraction and analysis to assess their suitability for biocomposite production. Lignocellulosic biofibres were extracted from young stems of Adenia lobata, Ampelocissus leonensis, Cissus palmatifida, Morinda morindoides and Urena lobata through natural water retting process for a period of 14 - 16 days and the resulting fibres were uniform with almost flat or circular cross sections. Phytochemical contents and extractives were determined on the untreated and treated fibres respectively. The %w/w cellulose contents of the pretreated biofibres were found to be 48.97± 1.33% for A. leonensis and 43.22±0.95% for A. lobata. The cellulose content of M. morindoides and C. palmitifida were found to be 55.76±1.40% and 55.20±1.59%, respectively. In all the plants studied, U. lobata had the greatest %w/w cellulose content of 58.94±1.05% while A. lobata had the least cellulose content of 43.22±0.95%. Estimation of %w/w hemicellulose contents showed A. leonensis to be 21.22±0.89% whilst the hemicelluloses content in A. lobata and U. lobata were observed to be 18.22±2.18% and 12.38±0.33% in that order. Lower hemicelluloses contents were obtained in C. palmitifida and M. morindoides as 10.32±1.27, 9.32±0.58 and 8.62±1.67%, respectively. The klason lignin contents were found to be 31.33±1.05% for C. palmitifida, 31.22±0.97% for M. morindoides, 28.22 ± 1.96% for A. lobata, and 24.91±0.61% for A. leonensis. The lignin content of U. lobata was found to be the least at 22.26±0.55%. Acid soluble lignin (ASL) content was greater in A. lobata (2.17±0.08%) while A. leonensis had the least value of 1.74±0.34%. ASL-derived products (vanillin, p-coumaric acid and ferulic acid) ranged between 0.50±0.12% and 1.41±0.02% for vanillin; 0.03± 0.02% and 0.65±0.14% for p-coumaric acid; and ferulic acid was only detected in A. leonensis as 0.41±0.11%. The mechanical properties of most fibres used in this study are comparable to those of other biofibres already used in manufacturing and can even match those of some synthetic fibres. Results obtained revealed that fibres used in this study had comparable properties with those already established for manufacturing in biofibre industries.   Key words: Biofibre, biocomposite, cellulose, lignin, hemicelluloses.

Mechanical Properties and Chemical Resistance of Short Tamarind Fiber/Unsaturated Polyester Composites: Influence of Fiber Modification and Fiber Content

In the present work, tamarind fibers were extracted from ripened fruits by the water retting process. Using these fibers as reinforcement and unsaturated polyester as matrix, composite samples were prepared by the hand lay-up technique. The effect of chemical surface treatments (alkali and silane) of tamarind fibers on the mechanical properties, chemical resistance, and interfacial bonding was studied. The mechanical properties of the composites with surface modified fibers were found to be higher than those with unmodified fibers. Morphological studies indicated improvement of interfacial bonding by alkali and silane coupling agent treatments of the fibers. The composites were found to be resistant to many chemicals.

Effects of cultural conditions on the hemp (Cannabis sativa) phloem fibres: Biological development and mechanical properties

Natural fibres such as hemp are extensively used in new composite materials. This article deals with biological and mechanical aspects of hemp phloem fibres. The effects of different cultural parameters on some characteristics of hemp fibres were studied: variety, soil drought during plant cultivation and water-retting process. Results showed that there was no significant influence on studied properties of the hemp variety and of water-retting. Under water-limited conditions, results showed that plant growth was reduced and the maturation of phloem fibres was delayed. Secondary cell wall was synthesised later in comparison with water-controlled conditions and cell protoplast remains longer. These biological aspects can be related to the higher Young’s modulus and maximal stress values measured on fibre strands from plants grown under water-stressed conditions. These results are promising, by considering the extent and degree of drought conditions in the world.

Sugar Palm Fibre-Reinforced Unsaturated Polyester Composite Interface Characterisation by Pull-Out Test

Polymer composites using natural fibres as the reinforcing agents have found their use in many applications. However, they do suffer from a few limitations, due to the hydrophilicity of the natural fibres which results in low compatibility with the hydrophobic polymer matrices. This paper aims to determine the best sugar palm (Arenga pinnata) fibre surface treatment to improve the fibre-matrix interfacial adhesion. Fibre surface modifications were carried out by water retting process where the fibres were immersed in sea water, pond water and sewage water for the period of 30 days. The test samples were fabricated by placing a single fibre in an unsaturated polyester resin. Single-fibre pull-out tests showed that freshwater-treated fibres possessed the highest interfacial shear strength, followed by untreated fibres, sewage water-treated fibres, and sea water-treated fibres. Further surface analyses of the samples were performed using a Scanning Electron Microscope (SEM) and an Energy Dispersive X-ray Spectroscopy (EDS) system.

Pre-Treatment by Water Retting to Improve the Interfacial Bonding Strength of Sugar Palm Fibre Reinforced Epoxy Composite

Polymer composites using natural fibres as the reinforcing agents have found their use in many applications. However, they do suffer from a few limitations, due to the hydrophilicity of the natural fibres which results in low compatibility with the hydrophobic polymer matrices. This paper presents the alternative low-cost methods of sugar palm (Arenga pinnata) fibre surface treatments to improve the fibre-matrix interfacial adhesion. Fibre surface modifications were carried out by water retting process where the fibres were immersed in sea water, pond water and sewage water for the period of 30 days. The results showed that the tensile and flexural strengths of the treated fibre reinforced composites increased as the fibre treatment duration increased. This indicates that the treatments had significantly improved the fibre-matrix bonding strength.

Effects of selected pectinolytic bacterial strains on water-retting of hemp and fibre properties

To study the effect of selected bacterial strains on hemp water-retting and properties of retted fibre. The trials were performed in laboratory tanks. The traditional water-retting process, without inoculum addition, was compared to a process modified by inoculating water tanks with two selected pectinolytic bacteria: the anaerobic strain Clostridium sp. L1/6 and the aerobic strain Bacillus sp. ROO40B. Six different incubation times were compared. Half the fibre obtained from each tank was combed. Micromorphological analyses were performed by scanning electron microscopy on uncombed and combed fibres. Moreover, organoleptic and chemical analyses of uncombed fibres were performed. The inoculum, besides speeding up the process, significantly improved the fibre quality. The fibre was not damaged by mechanical hackling, thanks to the good retting level obtained by the addition of selected strains, differently to what happened with the traditionally retted fibre. The best fibre quality was obtained after 3-4 days of retting with the addition of the bacterial inoculum. Retting is the major limitation to an efficient production of high-quality hemp fibres. The water-retting process and fibre quality were substantially improved by simultaneously inoculating water tanks with two selected pectinolytic strains.

Influence of Temperature on the Water Retting Process of Hemp (Cannabis sativaL.) Cultivated Under Swedish Climate Conditions

ABSTRACT Hemp has recently received increased interest as a sustainable crop for a multitude of possible uses. This paper focuses on the retting process, which is an important part in the processing of high quality fibre for, e.g., textile products. Water retting process trials were performed on stem plant material from Futura 75 grown at the Lönnstorp Farm research station in the south of Sweden in 2004. Three retting treatments at water temperature 30, 37.5 and 45°C were performed on dried hemp material. Hemp samples were taken from each of the three treatments at 48, 96, 144 and 196 hours. The retting process was investigated and documented by using the change in pectin content and the change in pH value as measures of the rettability. It was not possible to determine an optimal temperature for the retting process by these trials. However it could be concluded that 45°C was too high a water temperature.

Characterization of bacterial pectinolytic strains involved in the water retting process.

Pectinolytic microorganisms involved in the water retting process were characterized. Cultivable mesophilic anaerobic and aerobic bacteria were isolated from unretted and water-retted material. A total of 104 anaerobic and 23 aerobic pectinolytic strains were identified. Polygalacturonase activity was measured in the supernatant of cell cultures; 24 anaerobic and nine aerobic isolates showed an enzymatic activity higher than the reference strains Clostridium felsineum and Bacillus subtilis respectively. We performed the first genotypic characterization of the retting microflora by a 16S amplified ribosomal DNA restriction analysis (ARDRA). Anaerobic isolates were divided into five different groups, and the aerobic isolates were clustered into three groups. 84.6% of the anaerobic and 82.6% of the aerobic isolates consisted of two main haplotypes. Partial 16S rRNA gene sequences were determined for 12 strains, representative of each haplotype. All anaerobic strains were assigned to the Clostridium genus, whereas the aerobic isolates were assigned to either the Bacillus or the Paenibacillus genus. Anaerobic isolates with high polygalacturonase (PG) activity belong to two clearly distinct phylogenetic clusters related to C. acetobutylicum-C. felsineum and C. saccharobutylicum species. Aerobic isolates with high PG activity belong to two clearly distinct phylogenetic clusters related to B. subtilisT and B. pumilusT.

Tensile Properties of Pandanus Atrocarpus based Composites

Pandanus atrocarpus, or locally known as mengkuang plant is likely to be potential natural fibre reinforcement in composite. Both the Pandanus leaves, and fibres extracted from the Pandanus leaves were used in composite fabrication. Fibres were extracted from Pandanus leaves with water retting process. Pandanus composites were laminated using compression moulding method. The tensile properties of composite laminates based on lamination of Pandanus leaf- and extracted Pandanus fibre-reinforced polyethylene were investigated. Tensile tests have shown that composite laminates based on extracted Pandanus fibre reinforced polyethylene were more superior than using the Pandanus leaf itself without extracting its fibre. Tests exhibited that increasing the volume fraction of Pandanus fibre resulted in strength increase. This suggests that Pandanus fibre- based composites could offer a range of mechanical properties for use in the engineering industry.