Advanced Materials Research Vols. 29-30

Abstract: PP/EOC thermoplastic blend nanocomposites were prepared by melt intercalation technique using an intermeshing co-rotating twin screw extruder. The organoclay (Na+ MMT, Cloisite 20A, Cloisite 30B) content was varied between 0-5wt. % whereas the blend composition was kept constant (70PP: 30EOC) as optimized in our previous work. The effects of clays on the mechanical and rheological properties have been studied. Mechanical studies of PP/EOC nanocomposites reveal a significant increase in the impact strength upto a clay content of 3%. X-ray diffraction (XRD) analysis showed a significant increase in the interlayer gallery space with increase in clay loading. The rheological characterization made employing parallel plate rheometer revealed a maximum increase in storage modulus (G’) and loss modulus (G”) in case of modified clay indicating higher stiffness of the nanocomposites as compared to unmodified nanocomposites. Time Temperature superposition (TTS) was employed to generate various viscoelastic mastercurves.

Abstract: The present work summarizes an experimental study on the dynamic mechanical behaviour of sisal – glass fiber reinforced PP composites (SGRP). Variation in mechanical strength, storage modulus (E’), loss modulus (E’’) and damping parameters (tan δ) with the addition of fibers and MAPP were investigated. Mechanical tests revealed an increase in the tensile, flexural and impact strength in the SFRP composites with an increase in the fiber loading from 10% to 30%. Further the SGRP composites prepared using 15 wt% of glass and 15 wt % of sisal fiber, exhibited improved mechanical performance as compared with the virgin matrix as well as 30% SFRP composites. The fiber matrix morphology of the interface region in the composites was examined employing SEM analysis of the tensile fracture specimens. Thermal stability in the composites was studied using TGA/DTG thermo grams. Dynamic mechanical analysis data showed an increase in the storage modulus of the treated composite. The tanδ spectra presented a strong influence of fiber content and coupling agent on the α and γ relaxation process of PP. FTIR spectra of the treated and untreated sisal fibers was also studied to ascertain the existence of the type of interfacial bonds.

Abstract: Polycarbonate (PC) nanocomposites were prepared by melt intercalation technique in an intermeshing co-rotating twin-screw extruder. Both unmodified (Na+MMT) and organo-modified (Cloisite 10A & OMMT) clays were used for the preparation of nanocomposites. The effect of addition of clays on the morphological and dynamic mechanical properties of PC matrix has been studied. The wide angle X-ray (WAXD) studies reveal a dominated exfoliated morphology of the nanocomposites at a clay content of 5%. The intercalated morphology is predominated upto clay content of 3%. Transmission electron microscopy (TEM) demonstrated the co-existance of intercalated/exfoliated morphology in all the composites. Dynamic mechanical analysis (DMA) shows an increase in storage modulus indicating higher stiffness in case of organomodified clay filled composites as compared to unmodified & virgin matrix.

Abstract: The present paper summarizes an experimental study on the molten viscoelastic behavior of HDPE / jute composites under steady and dynamic mode. Variations of the melt viscosity and die swell of the composites with an increase in shear rate, fibre loading and coupling agent concentration have been investigated using capillary rheometer. It was observed that the melt viscosity of the composites increased with addition of fibres and MAPE. Further, the dynamic viscoelastic behavior of the composites was measured employing parallel plate rheometer. Time temperature superposition was applied to generate various viscoelastic master curves. The fibrematrix morphology of the extrudates were also examined using scanning electron microscopy.

Abstract: The paper presents the results of investigation on the wear of alumina-based composites containing submicrometre particles of other phases in different conditions of work. Three types of phases were used as additives: tungsten carbide, yttria stabilized zirconia and metallic tungsten. The above mentioned phases were used separately or simultaneously as mixes. Two types of tests were performed - the Dry Sand Test and the Miller Test in wet pulp. Coarse silicon carbide grains were used as an abrasive medium in both cases. The results indicate that the optimal wear susceptibility in given work environment could be achieved by the addition of different type of additives.

Abstract: Confocal microscopy and water diffusivity measurements were used to characterise the development of defects in biofibre-reinforced composite materials. Biofibres swelled more than the matrix when the specimen was immersed in water, but the associated distortion of the matrix rarely caused defects. The biofibres shrank faster than the matrix when the specimen was dried in air, causing debonding at the fibre-matrix interfaces and microcracks within the fibres. We started with coarse technical fibres from the leaves of harakeke (Phormium tenax), treated a portion with 1% NaOH, and pulped a portion at 170 °C. Water diffusivities for the corresponding composites increased over the first 3 wet-dry cycles, particularly for the composite made with untreated fibre, but were too small to be of concern for the composite made from pulped fibre.

Abstract: Thin and short multi walled carbon nanotubes (MWNTs) were used to prepare nanocomposites based on poly(3-hexylthiophene) (P3HT). The MWNTs were characterized by TEG, SEM, TEM and Raman spectroscopy following deposition of films from stable dispersions of MWNT in chloroform. Non-covalent interaction between MWNT and P3HT dissolved in chloroform allowed the preparation of solution-cast composite films. Composite thermal events such as glass transition, melting temperature and heat of fusion were investigated by DSC and compared with pure polymer. Conductivity of composite bulk films was measured as a function of temperature by 2-point probe DC-resistance measurements. Loadings of MWNTs above 0.1 weight percent (wt%) in the conjugated polymer significantly increased the conductivity of P3HT composites. Interplay between charge transport through the semiconductor polymer and carbon nanotube network allowed the increase of conductivity after percolation to values close to 10-2 S cm-1, an improvement of four orders of magnitude over that of films cast from pure P3HT.

Abstract: Clays are essentially composed of crystalline particles of one or more members of a small group of minerals. The ability of clays to intercalate certain organic substances has been known for a very long time. There is a scope in these clay structures for isomorphous replacement, that is, for substitution of Na+ by cations of similar size but usually of lower valency. This research aims at identifying suitable additives for pretreatment of clay and determining the effect of different classes of compounds (intercalants) on the d-spacing expansion of clay layers. This paper addresses a different approach to ion exchange for treatment of sodium montmorillonite, with different functional groups: aldehyde, ether, alcohol, glycol, and stearates. The results were compared with commercially available clays, Cloisite 25A and Cloisite 30B (Southern Clay Products), which are montmorillonite (MMT) clays intercalated with quaternary ammonium salts. The d-spacing increment in this research was consistent with the d-spacing achieved in commercially available clays. Future research will be to utilize the treated clay to produce polymer composites.

Abstract: A nondestructive technique would be very beneficial, which could be used to test the CF/Epoxy composite laminates. A new method for nondestructively determining the ply layup in a composite laminate is presented. A one-sided pitch-catch setup was used in the detection and evaluation of flaws and material anomalies in the composite laminates. Two Rayleigh wave transducers were joined head-to-head and used in the pitch-catch mode on the surface of the composites. The pitch-catch signal was found to be more sensitive than normal incidence backwall echo of longitudinal wave to subtle flaw conditions in the composite. Also the other method employs a normal-incidence longitudinal ultrasound to perform C-scan of ply interfaces of the laminate, and extracts fiber orientation information from the ultrasonic reflection in the laminate. Using two-dimensional spatial Fourier transform, interface C-scan images were transformed into quantitatively angular distribution plots to show the fiber orientation information therein and to determine the orientation of the ply. Therefore, it is found that the efficiency of developed system shows between the one-sided pitch-catch testing and C-scan images in characterizing ply-layup orientation of the laminates.

Abstract: In recent years, industrial hemp fibre reinforced thermoplastic composites have attracted substantial interest as potential structural materials. These composites have been subject to intense study for use in lightweight, recyclable and low cost applications. The aim of this research was to improve and evaluate the composite tensile strength and fibre/matrix interfacial adhesion by means of fibre treatment and addition of a coupling agent. Hemp fibre was digested in a small pressure vessel with a solution of 5wt% NaOH / 2wt% Na2SO3. Single fibre tensile tests were performed on treated and untreated fibres, and it was found that the alkali treatment resulted in an increase in fibre strength and an improvement in fibre separation. Composites containing either treated or untreated fibre, polypropylene and a maleic anhydride modified polypropylene (MAPP) coupling agent were then compounded in a twin-screw extruder and injection moulded into tensile test specimens. Tensile tests revealed that significant improvements in composite strength were made by using treated fibre and MAPP. The effect of MAPP on the interface of treated hemp fibre/polypropylene composites was assessed by means of the single fibre fragmentation test, and the interfacial shear strength was determined thereafter.