Coir Fiber Composites Research Articles

Effect of concentration of coupling agent on mechanical properties of coir–polypropylene composite

Coir fiber and polypropylene (PP) composites were prepared using m-isopropenyl-α-α-dimethylbenzyl isocyanate grafted polypropylene as a coupling agent. The effect of concentration of coupling agent on mechanical properties (tensile, flexural and impact) was investigated and discussed. The mechanical tests indicate that tensile and flexural strength increases with increase in concentration of coupling agent. The optimum loading capacity of coupling agent was 5 %. Increase in tensile and flexural strength may be attributed to improved wetting and interaction between PP and coir fiber. However, their was no effect of coupling agent concentration on tensile or flexural modulus. The impact strength of composite was also investigated which showed that notched impact strength reduces with increase in coupling agent concentration, while un-notched impact strength increases with increase in coupling agent concentration.

Understanding the interfacial compatibility and adhesion of natural coir fibre thermoplastic composites

An integrated physical–chemical–micromechanicalapproach is implemented to investigate the fibre–matrix interfacial compatibility and adhesion of natural coir fibre composites. Wetting measurements of the fibres and the matrices are carried out to obtain their static equilibrium contact angles in various liquids, and these are used to estimate the surface energies comprising of different components. The work of adhesion is calculated for each composite system, accordingly. Also, fibre surface chemistry is examined by X-ray photoelectron spectroscopy (XPS)to have more information about functional groups at the fibre surface, which assists in adeeper understand ing of the interactions at the composite interfaces. Single fibre pull-out tests and transverse three point bending tests are performed on UD composites to measure interfacial shear strength and interfacial tensile strength respectively. The results suggest that the higher interfacial adhesion of coir fibreswith polyvinyliden efluoridecompared with polypropylene can be attributed to higher fibre–matrix physico-chemical interaction corresponding with the work of adhesion. Whilst the improvement of interfacial adhesion for coir fibreswith maleic anhydride grafted polypropylene compared with polypropylene can probably be attributed to achemical adhesion mechanism. In agreement with the interface evaluations, the flexural strength in longitudinal direction of the composites is largely correlated with their interfacial adhesion.

A review on the characteristics of gomuti fibre and its composites with thermoset resins

Gomuti fibre is obtained from Arenga pinnata tree and is known with other names such as sugar-palm fibre, gomutu, ijuk, serat aren and black fibre. This article presents a review on the physical, mechanical, chemical and thermal properties of gomuti fibre in comparison with other common natural fibres. Furthermore, this article reviews the mechanical properties of gomuti fibre composites with thermoset polymer resins based on the existing published literature. It is observable that gomuti fibre has a close similarity to coir fibre in its physical and mechanical properties than the other natural fibres. It has the characteristics of lower density, strength and modulus, but higher elongation. The composites with gomuti fibre also exhibit properties similar to coir fibre composites.

Chemical Modification Effect on the Mechanical Properties of Coir Fiber

Natural fiber has a vital role as a reinforcing agent due to its renewable, low cost, biodegradable, less abrasive and eco-friendly nature. Whereas synthetic fibers like glass, boron, carbon, metallic, ceramic and inorganic fibers are expensive and not eco-friendly. Coir is one of the natural fibers easily available in Bangladesh and cheap. It is derived from the husk of the coconut (Cocos nucifera). Coir has one of the highest concentrations of lignin, which makes it stronger. In recent years, wide range of research has been carried out on fiber reinforced polymer composites [4-13].The aim of the present research is to characterize brown single coir fiber for manufacturing polymer composites reinforced with characterized fibers. Adhesion between the fiber and polymer is one of factors affecting the strength of manufactured composites. In order to increase the adhesion, the coir fiber was chemically treated separately in single stage (with Cr 2 (SO 4 )3•12(H 2 O)) and double stages (with CrSO 4 and NaHCO 3 ). Both the raw and treated fibers were characterized by tensile testing, Fourier transform infrared (FTIR) spectroscopic analysis, scanning electron microscopic analysis. The result showed that the Young’s modulus increased, while tensile strength and strain to failure decreased with increase in span length. Tensile properties of chemically treated coir fiber was found higher than raw coir fiber, while the double stage treated coir fiber had better mechanical properties compared to the single stage treated coir fiber. Scanning electron micrographs showed rougher surface in case of the raw coir fiber. The surface was found clean and smooth in case of the treated coir fiber. Thus the performance of coir fiber composites in industrial application can be improved by chemical treatment.

Chemical Treatment of Coir Fiber Reinforced Polypropylene Composites

Agro-based renewable materials have received significant attention in recent years because of their low cost, light weight, ecofriendliness, and worldwide environmental awareness. In the present work, coir fiber reinforced polypropylene composites were manufactured using injection molding method. Raw coir was chemically treated with benzene diazonium salt in alkali, acidic, and neutral media separately in order to increase the compatibility between the coir fiber and polypropylene composite. During chemical treatment, hydrophilic -OH groups in the raw coir cellulose were converted to hydrophobic -O–Na groups. Both raw and treated coir at 10, 15, 20, 25, 30, and 35 wt % were utilized during composite manufacturing. Microstructural analysis and mechanical tests were conducted. Alkali treated specimens yielded the best set of mechanical properties. On the basis of fiber loading, 30% fiber reinforced composites had the optimum set of mechanical properties among all composites manufactured.

A comparative study on the mechanical and degradation properties of plant fibers reinforced polyethylene composites

AbstractCoir and abaca fiber‐reinforced linear low density polyethylene (LLDPE) composites (30 wt% fiber) were prepared by compression molding. Coir and abaca fibers were treated with methyl methacrylate (MMA) using ultraviolet radiation to improve the mechanical properties of the composites. Concentration of MMA and radiation dose was optimized. It was found that 30% MMA in methanol along with photoinitiator Darocur‐1173 (2%) and 15th pass of radiation rendered better performance. Chemically treated fiber‐reinforced specimens yielded better mechanical properties compared to the untreated composites, whereas coir fiber composites had better mechanical properties than abaca fiber reinforced ones. For the improvement of the properties, optimized coir (coir fiber treated with 30% MMA) and abaca (abaca fiber treated with 40% MMA) fibers were again treated with aqueous starch solution (2%–8%, w/w) for 2–7 min. Composites made of 3%‐starch‐treated coir fiber (5 min soaking time) showed the best mechanical properties than that of abaca‐fiber‐based composites. Water uptake and soil degradation tests of the composites were also performed. POLYM. COMPOS., 2011. © 2011 Society of Plastics Engineers

Processing and characterization of solid and microcellular PHBV/coir fiber composites

Poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV)/coir fiber composites were prepared via both conventional and microcellular injection-molding processes. The surface of the hydrophilic coir fiber was modified by alkali- and silane-treatment to improve its adhesion with PHBV. The morphology, thermal, and mechanical properties were investigated. The addition of coir fiber (treated and untreated) reduced cell size and increased cell density. Further decrease in cell size and increase in cell density was observed for treated fibers compared with PHBV/untreated-fiber composites. Mechanical properties such as specific toughness and strain-at-break improved for both solid and microcellular specimens with the addition of coir fibers (both treated and untreated); however, the specific modulus remained essentially the same statistically while the specific strength decreased slightly. The silane-treated coir fiber composites showed the greatest improvement in specific toughness and strain-at-break among the treated-fiber composites. In addition, adding coir fibers (treated and untreated) also increased the degree of crystallinity of the PHBV composites. PHBV with treated coir fibers showed a higher degree of crystallinity compared with untreated coir fibers.

Mechanical Properties of Polypropylene Composites Reinforced with Chemically Treated Coir and Abaca Fiber

Coir and abaca fiber-reinforced polypropylene composites were manufactured using a single extruder and an injection molding machine. Raw coir and abaca were chemically treated with benzene diazonium salt. Both raw and treated coir and abaca fibers at level of fiber loading (10, 15, 20, 25, and 30 wt%) were utilized during composite manufacturing. Mechanical tests of the resultant composites and PP were conducted. A comparison has been made between the mechanical properties of the coir and abaca fiber-reinforced composites. Chemically treated fiber-reinforced specimens yielded better mechanical properties compared to the raw composites, while coir fiber composites had better mechanical properties than abaca fiber reinforced ones. Based on fiber loading, 30% fiber-reinforced composites had the optimum set of mechanical properties.

Improvement Properties of Recycled Polypropylene by Reinforcement of Coir Fiber

This research was to study the related mechanical and thermal properties of recycled polypropylene from post consumer containers reinforced with coir fiber. Surface of coir fiber was treated with sodium hydroxide to remove lignin and hemicelluloses and likely to improve the interfacial adhesion in the composites. The composites of treated coir fiber and recycled polypropylene were prepared by varying the coir fiber contents at 5%, 10% and 20% by weight using a twin screw extruder. The thermal properties were investigated by thermal gravimetric analysis (TGA) and differential scanning calorimeter (DSC). The results from TGA showed that thermal stability of the composites was lower than that of recycled polypropylene resin and thermal stability decreased with increasing coir fiber content. From DSC results, it indicated that the crystallinity of treated coir fiber composites increased as a function of fiber content. The mechanical properties of injection-molded samples were studied by universal testing machine. The treated coir fiber composites produced enhanced mechanical properties. The tensile strength, tensile modulus and impact strength of modified coir fiber/recycled polypropylene composites increased as a function of coir fiber content.

Use of Sand–Coir Fiber Composite Columns in Stabilization of Soft Clay Deposits

Coir, the processed fiber from the husk of coconuts, is reputed to be the strongest and most durable natural material and is abundantly available at low cost in many Asian countries. A few studies have been conducted in the past to examine the potential of coir as a random reinforcing material. This paper reports the degree of improvement obtained by using sand–coir fiber composite in the form of columnar reinforcement in plate load tests on soft clay beds. Influence of area as well as configuration of columns on the pressure versus settlement behavior of soft clay is identified and isolated. The study indicates that strength improvement sufficient enough to eliminate the need for a deep foundation is achievable through the use of the proposed technique. The provision of four identical sand–coir fiber columns just inside the corners of the loaded area is the optimum configuration as far as soil improvement is concerned. This paper also discusses the mechanism of soil improvement and the possibility of expressing the degree of improvement as a unique function of relative column area and normalized column depth.

Physico-mechanical properties of chemically treated palm and coir fiber reinforced polypropylene composites

In this work, palm and coir fiber reinforced polypropylene bio-composites were manufactured using a single extruder and injection molding machine. Raw palm and coir were chemically treated with benzene diazonium salt to increase their compatibility with the polypropylene matrix. Both raw and treated palm and coir fiber at five level of fiber loading (15, 20, 25, 30 and 35 wt.%) was utilized during composite manufacturing. Microstructural analysis and mechanical tests were conducted. Comparison has been made between the properties of the palm and coir fiber composites. Treated fiber reinforced specimens yielded better mechanical properties compared to the raw composites, while coir fiber composites had better mechanical properties than palm fiber ones. Based on fiber loading, 30% fiber reinforced composites had the optimum set of mechanical properties.

Tensile behaviours of the coir fibre and related composites after NaOH treatment

Brown coir fibres were treated by NaOH solution with concentrations from 2% to 10% separately. Tensile strength of the alkali-treated fibres was measured. A decreased trend of the fibre tensile strength with increased NaOH density was found. Laminated coir fibre net was used as the reinforcement and polypropylene as the matrix to fabricate the composites with a heat press. The tensile strength of the samples was shown. In the case of NaOH density with 10%, lower tensile strength of the composite was noticed compared to the cases of 2%, 4%, 6% and 8%. This demonstrated that the fibre deterioration in the 10% case was serious. No significant difference was revealed in the composite tensile strength among the cases of 2%, 4%, 6% and 8%. This implied that the improved adhesive ability of the coir fibre with the matrix after the alkali treatment had been outweighed by the strength loss of the fibre in these four cases.

Effect of NaOH Treatments on Jute and Coir Fiber PP Composites

Changes occurring in jute and coir fiber composites with 2–8% concentration of a NaOH treatment for 24 h were investigated, respectively, for void content, microscopy images, mechanical properties and water absorption. The jute and coir fibers were vacuum dried before molding composite specimens. Mechanical properties indicated good adhesion between natural fibers and PP. Jute fibers, when alkali-treated with 2% concentration for 24 h, showed best improvement in tensile strength by 40% and modulus by 9%, respectively, while coir fibers, when alkali-treated with 6% concentration for 24 h, showed best improvement in tensile strengths by 62% and modulus by 17%, respectively. With 2% concentration of alkali-treatments, the elongation of jute and coir composites reached 8% and 13.5%, respectively. Moisture absorption for jute and coir composites are 50% and 60% lower than untreated fiber composites, respectively.

Recycled milk pouch and virgin low‐density polyethylene/linear low‐density polyethylene based coir fiber composites

AbstractThe viability of the thermomechanical recycling of postconsumer milk pouches [a 50 : 50 low‐density polyethylene/linear low‐density polyethylene (LDPE–LLDPE) blend] and their use as polymeric matrices for coir‐fiber‐reinforced composites were investigated. The mechanical, thermal, morphological, and water absorption properties of recycled milk pouch polymer/coir fiber composites with different treated and untreated fiber contents were evaluated and compared with those of virgin LDPE–LLDPE/coir fiber composites. The water absorption of the composites measured at three different temperatures (25, 45, and 75°C) was found to follow Fickian diffusion. The mechanical properties of the composites significantly deteriorated after water absorption. The recycled polymer/coir fiber composites showed inferior mechanical performances and thermooxidative stability (oxidation induction time and oxidation temperature) in comparison with those observed for virgin polymer/fiber composites. However, a small quantity of a coupling agent (2 wt %) significantly improved all the mechanical, thermal, and moisture‐resistance properties of both types of composites. The overall mechanical performances of the composites containing recycled and virgin polymer matrices were correlated by the phase morphology, as observed with scanning electron microscopy. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2007

Flexural characteristics of coir fiber reinforced cementitious composites

This study has examined the flexural properties of natural and chemically modified coir fiber reinforced cementitious composites (CFRCC). Coir fibers of two different average lengths were used, and the longer coir fibers were also treated with a 1 % NaOH solution for comparison. The fibers were combined with cementitious materials and chemical agents (dispersant, defoamer or wetting agent) to form CFRCC. The flexural properties of the composites, including elastic stress, flexural strength, toughness and toughness index, were measured. The effects of fiber treatments, addition of chemical agents and accelerated ageing of composites on the composites’ flexural properties were examined. The results showed that the CFRCC samples were 5–12 % lighter than the conventional mortar, and that the addition of coir fibers improved the flexural strength of the CFRCC materials. Toughness and toughness index, which were associated with the work of fracture, were increased more than ten times. For the alkalized long coir fiber composites, a higher immediate and long-term toughness index was achieved. SEM microstructure images revealed improved physicochemical bonding in the treated CFRCC.

Natural fibres: can they replace glass in fibre reinforced plastics?

In this work, natural fibres (sisal, kenaf, hemp, jute and coir) reinforced polypropylene composites were processed by compression moulding using a film stacking method. The mechanical properties of the different natural fibre composites were tested and compared. A further comparison was made with the corresponding properties of glass mat reinforced polypropylene composites from the open literature. Kenaf, hemp and sisal composites showed comparable tensile strength and modulus results but in impact properties hemp appears to out-perform kenaf. The tensile modulus, impact strength and the ultimate tensile stress of kenaf reinforced polypropylene composites were found to increase with increasing fibre weight fraction. Coir fibre composites displayed the lowest mechanical properties, but their impact strength was higher than that of jute and kenaf composites. In most cases the specific properties of the natural fibre composites were found to compare favourably with those of glass.