Sanjay K. Nayak

Studies on mechanical performance of biofibre/glass reinforced polyester hybrid composites

Abstract The degree of mechanical reinforcement that could be obtained by the introduction of glass fibres in biofibre (pineapple leaf fibre/sisal fibre) reinforced polyester composites has been assessed experimentally. Addition of relatively small amount of glass fibre to the pineapple leaf fibre and sisal fibre-reinforced polyester matrix enhanced the mechanical properties of the resulting hybrid composites. Different chemically modified sisal fibres have been used in addition to glass fibers as reinforcements in polyester matrix to enhance the mechanical properties of the resulting hybrid composites. The surface modification of sisal fibres such as alkali treatment produced optimum tensile and impact strengths, while cyanoethylation resulted in the maximum increase in flexural strength of the hybrid composites. It has been observed that water uptakes of hybrid composites are less than that of unhybridized composites. Scanning electron microscopic studies have been carried out to study the fibre-matrix adhesion.

The influence of fibre treatment on the performance of coir-polyester composites

Abstract Surface modifications of coir fibres involving alkali treatment, bleaching, and vinyl grafting are made in view of their use as reinforcing agents in general-purpose polyester resin matrix. The mechanical properties of composites like tensile, flexural and impact strength increase as a result of surface modification. Among all modifications, bleached (65°C) coir-polyester composites show better flexural strength (61.6 MPa) whereas 2% alkali-treated coir/polyester composites show significant improvement in tensile strength (26.80 MPa). Hybrid composites comprising glass fibre mat (7 wt.%), coir fibre mat (13 wt.%) and polyester resin matrix are prepared. Hybrid composites containing surface modified coir fibres show significant improvement in flexural strength. Water absorption studies of coir/polyester and hybrid composites show significant reduction in water absorption due to surface modifications of coir fibres. Scanning electron microscopy (SEM) investigations show that surface modifications improve the fibre/matrix adhesion.

Effect of MAPP as a Coupling Agent on the Performance of Jute–PP Composites

Like other natural fibers jute, because of its hydrophilic nature, is incompatible with nonpolar plastics matrices. This has been the major handicap for preparing stable composites. In this paper we have used maleic anhydride grafted polypropylene, MAPP(G-3015) as the coupling agent for the surface modification of the fibers. Various parameters such as effect of fiber length, MAPP concentration, time period of MAPP treatment, percentage (wt./wt.) of fiber loading on mechanical properties such as tensile, flexural and impact strengths have been studied. It has been found that 30% fiber loading with 0.5% MAPP concentration in toluene and 5 min impregnation time with 6 mm average fiber lengths give the best results. Nearly 72.3% increase in flexural strength was observed in respect of treated composites. The fiber matrix interface was analyzed from the SEM micrographs. Water absorption of the composites has also been considerably reduced in the treated composites. Thermal behavior of the composites were also studied through DSC measurements. The MFI study also supports better fiber matrix adhesion.

Potentiality of Pineapple Leaf Fibre as Reinforcement in PALF-Polyester Composite: Surface Modification and Mechanical Performance:

This paper is an attempt to examine the commercial signficance of an agro-waste “Pineapple Leaf Fibre” (PALF) which is rich in cellulose, relatively inexpensive and has the potential for polymer reinforcement. The quality enhancement of PALF has been tried through different surface modifications like dewaxing, alkali treatment, cyanoethylation and grafting of AN onto dewaxed PALF. The present study investigated the mechanical propeties like tensile, flexural and impact behavior of PALF-reinforced polyester composites as a function of fibre loading and fibre surface modification. The mechanical properties are optimum at a fibre loading of 30 wt%. Among all modifications, 10% AN grafted PALF composite exhibited maximum tensile strength (48.36 MPa) whereas cyanoethylated PALF composite exhibited better flexural and impact strength, i.e., 41% and 27% more than the control (detergent washed composite) respectively. Scanning electron microscopic studies were carried out to understand the fibre-matrix adhesion.

Scanning electron microscopy study of chemically modified coir fibers

Chemical-surface modification of coir fibers was done by dewaxing, using an alkali treatment (5% and 10% NaOH), vinyl grafting with methyl methacrylate (MMA) and cyanoethylation. The chemically modified fibers were characterized by Fourier transform infrared (FTIR) spectroscopy. In addition, the surface features of untreated, dewaxed, alkali-treated, grafted, and cyanoethylated coir fibers were studied using scanning electron microscopy (SEM). Progressive changes in surface morphology were observed. SEM observations showed the removal of tyloses from the surface of coir as a result of alkali treatment (5%), resulting in a rough fiber surface with regularly spaced pits. At a lower percentage of grafting (PMMA), the surfaces became more or less uniform, while the surfaces of the coir fibers with a higher percentage of grafting were increasingly covered with grafted materials, resulting in canal-like cavities between the overgrowths of the grafted materials on the unit cells. Cyanoethylated coir-fiber surfaces showed an insufficient deposit of cyanoethyl groups. SEM analysis of the samples was corroborated by measurements of a mechanical property (maximum stress at break).

Graft Copolymerization of Acrylonitrile on Chemically Modified Sisal Fibers

Graft copolymerization of acrylonitrile (AN) on chemically modified sisal fibers was studied using a combination of NaIO 4 and CuSO 4 as initiator in an aqueous medium in the temperature range of 50-70°C. Effects of reaction medium, variation of time and temperature, concentration of CuSO 4 , NaIO 4 and AN, and the amount of sisal fiber on the percentage of graft yield have been investigated. Water absorption (%) and tensile properties such as tensile strenght, Youngs modulus and extension at break of untreated, chemically modified and AN-grafted sisal fibers were evaluated and compared. FTIR spectroscopy and scanning electron microscopy (SEM) of the chemically modified and AN-grafted sisal fibers have been carried out.

Novel Eco-Friendly Biocomposites: Biofiber Reinforced Biodegradable Polyester Amide Composites—Fabrication and Properties Evaluation

Lignocellulosic natural fibers like sisal and pineapple leaf fiber (PALF) can be incorporated in polymers based on biodegradable polyester amide matrix, BAK 1095 for achieving desired properties and texture in the resulting biocomposites. But high level of moisture absorption, poor wettability and insufficient adhesion between untreated fiber and the polymer matrix led to debonding with age. In order to improve the above qualities, various surface treatments of sisal fiber like mercerization, cyanoethylation, acetylation, bleaching and vinyl monomer (acrylonitrile) grafting are carried out which results in improved mechanical performance of sisal-BAK composites. Mechanical properties like tensile and flexural strength are optimum at a fiber loading of 50 wt%. Among all modifications, alkali treatment and acetylation result in improved properties of the composites. Alkali treated sisal composite shows about 20% increase in tensile strength and acetylated sisal composite shows about 14% increase in flexural strength compared to the control, i.e., untreated sisal based biocomposites. From the biodegradation study, we find that after 60 days of soil burial about 1% weight loss is observed for BAK whereas acetylated sisal-BAK composite shows maximum weight loss (22%). It also shows maximum decrease in flexural strength (47%) after 15 days of sisal burial. A comparative account of properties of PALF-BAK and sisal-BAK biocomposites is also given. Scanning electron microscopic studies were carried out for better understanding of fiber-matrix adhesion in biocomposites.

Polypropylene—Bamboo/Glass Fiber Hybrid Composites: Fabrication and Analysis of Mechanical, Morphological, Thermal, and Dynamic Mechanical Behavior:

Hybrid composites of polypropylene reinforced with bamboo and glass fibers (BGRP) were fabricated using an intermeshing counter rotating twin screw extruder followed by injection molding. Maleic anhydride grafted polypropylene (MAPP) has been used as a coupling agent to improve the interfacial interaction between the fibers and matrix. The mechanical properties of the hybrid composites were studied from tensile, flexural, and impact tests. Mechanical tests indicated an increase in tensile, flexural, and impact strength of the BGRP hybrid composites at a bamboo:glass fiber ratio of 15:15 ratio in the presence of 2 wt% of MAPP. Nearly, 69, 86, and 83% increase in tensile flexural and impact strength respectively has been observed as compared with virgin PP. The fiber matrix interfacial morphology of the tensile fractured specimens was studied using scanning electron microscopy (SEM) which showed less fiber pullout and comparatively less gaps between the fiber and the base matrix in the case of MAPP treated hybrid composites. The crystallization, melting behavior and thermal stability of the hybrid composites were investigated employing differential scanning electron microscopy (DSC) and thermogravimetric analysis (TGA). Thermogravimetric analysis (TGA) showed an increase in thermal stability of the matrix polymer with incorporation of bamboo and glass fibers, confirming the effect of hybridization and efficient fiber matrix interfacial adhesion. The dynamic mechanical analysis (DMA) showed an increase in storage modulus (E′) indicating higher stiffness in case of hybrid composites as compared with untreated composites and virgin matrix. The tan δ spectra presented a strong influence of fiber content and coupling agent on the α and γ relaxation process of PP.

Sisal Glass Fiber Reinforced PP Hybrid Composites: Effect of MAPP on the Dynamic Mechanical and Thermal Properties

Hybrid composites of polypropylene (PP) reinforced with short sisal and glass fibers were prepared using twin-screw extruder, followed by injection molding in the presence and absence of maleic anhydride grafted PP (MAPP) as a coupling agent. The mechanical properties such as tensile strength, flexural strength, and impact strength increased by an optimum value at 15% sisal and 15% glass fiber loading in the presence of 2% MAPP. The rate of water absorption in the composites decreased due to the presence of glass fiber and coupling agent. The storage modulus of sisal/glass reinforced PP hybrid composites (SGRP) showed maximum improvement after treatment with MAPP. The fiber matrix morphology of the interface region in the composites was examined using scanning electron microscopy. The differential scanning calorimetry thermogram confirms higher thermal stability in the case of hybrid composites.

Polypropylene Nanocomposites: Effect of Organo-modified Layered Silicates on Mechanical, Thermal & Morphological Performance

The present article reports the mechanical, thermal and morphological characteristics of polypropylene — maleic anhydride grafted polypropylene —organically modified MMT (PP-PP-g-MAH-OMMT) nanocomposites. PP nanocomposites were prepared by melt mixing in a twin screw extruder followed by injection moulding. Sodium montmorillonite has been organically modified using quaternary ammonium intercalants. A comparative account with commercial quaternary ammonium modified clay; Cloisite 15A has also been presented. Mechanical tests showed considerable improvement in tensile, flexural and impact properties of PP matrix with the incorporation of organically modified nanoclays. Furthermore, the quaternary ammonium intercalants exhibited improved performance with an optimum improvement in compatibilized PP/Cloisite 15A nanocomposites. The morphology of the nanocomposites has been examined using wide angle X-ray diffraction (WAXD) and transmission electron microscopy (TEM). Morphological findings revealed efficient dispersion of organically modified nanoclays within the PP matrix. PP-g-MAH compatibilized PP/Cloisite 15A nanocomposites displayed finely dispersed exfoliated nanomorphology as compared with other systems. The crystallization, melting behavior and thermal stability of the nanocomposites has been studied using differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA) which indicated an increase in crystallization temperature as well as thermal stability of PP matrix in Cloisite 15A nanocomposites. DMA curves also confirmed an increase in storage modulus of PP matrix in the nanocomposites, indicating an increase in the stiffness of the matrix polymer with the addition of organically modified nanoclays.