M. F. Mina

Thermo-mechanical and morphological properties of short natural fiber reinforced poly (lactic acid) biocomposite: Effect of fiber treatment

Untreated oil palm empty fruit bunch (REFB), alkali treated EFB (AEFB), ultrasound treated EFB (UEFB) and simultaneous ultrasound-alkali treated EFB (UAEFB) short fibers were incorporated in poly(lactic acid) (PLA) for fabricating bio-composites. The REFB fiber-PLA (REPC) and treated EFB (TEFB) fiber-PLA (TEPC) composites were prepared and characterized. Glass transition temperature, crystal melting temperature, decomposition temperature, melt flow index, density and mechanical properties (tensile strength, tensile modulus and impact strength) of TEPC are found to be higher than those of REPC. The observed crystallization temperature of TEPC is lower than that of REPC. Among all samples, TEPC prepared from UAEFB fiber shows better performances than other samples fabricated by REFB and AEFB fibers. Scanning electron microscopy, Fourier transform infrared spectroscopy and XRD analyses well support all the observed results.

Degradation And Stability Of Green Composites Fabricated From Oil Palm Empty Fruit Bunch Fiber And Polylactic Acid: Effect Of Fiber Length

In this work, polylactic acid and oil palm empty fruit bunch fiber-reinforced green composites have been fabricated by using random and fixed-length fibers through extrusion followed by injection molding. The prepared composites have been characterized by mechanical tests, thermal analysis, Fourier transform infrared spectroscopy, scanning electron microscopy, and X-ray diffractometry. Among all fabricated composites having various sizes and contents of fibers, 30-mm long and 40 wt% empty fruit bunch fiber-incorporated composites show the optimum tensile strength and modulus. As compared to raw empty fruit bunch fiber-loaded composites, simultaneous ultrasound and alkali-treated empty fruit bunch-reinforced composites have revealed improved mechanical performances, enhanced crystallinity, and thermal stability. In case of soil burial degradation studies, treated empty fruit bunch fiber-reinforced composite has been found to be more stable than untreated fiber-reinforced composite.

Structures and Performance of White Clay-Filled Isotactic-Polypropylene Composites Prepared by Double-Molding Techniques

Various contents of Bangladeshi white clay (WC)-filled Isotactic polypropylene (iPP) composites were fabricated by double-molding techniques. Scanning electron micrographs shows a good impact between iPP matrix and fillers. X-diffraction and IR spectroscopic measurements reveal that inclusion of fillers develops an additional γ-crystal along with the α- and β-crystals that are merely observed in the neat iPP. Youngs modulus and microhardness are found to increase with increasing WC content. Thermal analyses represent a considerable increase of thermal stability of the composites with filler addition. Appearance of new crystalline phase by filler inclusion and performances of the composites are discussed in detail.

Twin Formation Mechanism in the Solid-Solid Phase Transition of Normal Hexatriacontane (n-C36H74).

Solid-solid phase transition of n -C 36 H 74 was investigated by DSC and X-ray diffraction methods. In the original monoclinic single crystal, molecular chains inclined about 27° in the bc -plane from the normal to the lamellar surface. During the transition started from 72°C and completed at 73.4°C, two kinds of mechanisms were observed in the formation of a high temperature monoclinic structure having the molecules inclined about 19° in the ac -plane. One mechanism was due to formation of twinned crystals where the transition was developed on the frontier of the (110) twin boundary. The twin formation was achieved by rotation of the molecular zigzag plane producing the new crystalline a -axis deviated by 67° from the original orientation. The other mechanism was attained by changing the molecular staggering by 90° where the crystalline axis was unchanged. In the solid-solid transition, the two mechanisms appeared simultaneously, resulting in the appearance of polycrystals.

Studies of Micromechanical Deformation Processes in Particle-Filled Glassy Polymer

ABSTRACT The deformation behavior of rubber-toughened polymer, which was prepared by incorporating soft, core-shell rubbery particles into a glassy polymer such as poly (methyl methacrylate) (PMMA), has been investigated by means of mechanical tests, optical monitoring (OM), and scanning electron microscopy (SEM). By mechanical testing, the neat PMMA reveals a 2% strain with high yield stress. After inclusion of 17.5 and 35 vol%rubber particles, the softened-PMMA samples exhibit corresponding strain of 20% and 38%, showing an increase of strain along with the relative decrease of yield stress, resulting in a toughening behavior of PMMA. Clear shear bands and stress whitening develop in the rubber-toughened PMMA after deformation, as observed by OM. Investigation by SEM shows crazes/cracks in the stretched, rubber-softened PMMA samples in which the core-shell particles are found to be cavitated. The mechanism of this deformation has been explained based on the void formation in the rubbery shell as well as the initiation and propagation of crazing.

Studies of γ-Ray Induced Polymerization of Aqueous Acrylamide

Polymerization of acrylamide has been performed by γ-ray irradiation at various radiation doses with the help of a Co-60 source, which was used to produce the samples from aqueous solutions of acrylamide monomer in single distilled water having the concentrations of 20, 30 and 40% (w/w). Solubility test, differential scanning calorimetry, and infrared (IR) spectroscopy demonstrate that the properties of the samples prepared by irradiation are quite different from that of a monomer. The degree of polymer conversion is found to depend on doses and concentrations, where maximum conversion reaches at doses of 0.18, 0.16, and 0.10 kGy for 20, 30, and 40% concentrations, respectively. Viscosity and molecular weight (MW) of irradiated samples increase with both the doses and concentrations showing the value of MW≈108, which strongly indicates the polymer formation. The amount of gel content that represents the cross-linked portions in the irradiated samples is found to be negligible, suggesting the formation mainly of polyacrylamide.

Centrifuging Effect on the Structure and Property of Natural Rubber Latex Films

Abstract The structure and property of the films produced from natural rubber latexes such as field latex (FL) and single, double, and triple centrifuged latexes were studied by x‐ray diffraction and mechanical testing methods, respectively. Mechanical test shows that tensile strength of the film increases after single centrifugation and then decreases with higher order centrifugation, whereas elongation‐at‐break (EB) decreases with successive centrifugation. X‐ray diffraction study clearly reveals a change of average molecular packing and structural element of the centrifuged films. These results clarify that purification of rubber latex by single centrifugation promotes tensile strength resulting from the elimination of inhibitor type of nonrubbery constituents. Higher order centrifugation causes a decrease of this property because of the elimination of accelerator type nonrubbery elements having the sizes of 1.4–2.5 nm and 18–42 nm. The decrease of EB with sequential centrifugation is associated with the removal of both accelerator and inhibitor type particles.

Dynamic Investigation of the Solid-Solid Phase Transition of Normal-Alkane (Hexatriacontane) by Simultaneous Measurements with Differential Scanning Calorimetry, Small-Angle X-Ray Scattering and X-Ray Television Detector

Simultaneous measurements have been performed using differential scanning calorimetry, time-resolved small-angle X-ray scattering and X-ray television (TV) methods to study the solid-solid phase transition of the normal-alkane (hexatriacontane) single crystal. The low-temperature monoclinic form (M L) of hexatriacontane transforms to the high-temperature monoclinic form (M H) by two mechanisms. One mechanism is a direct transition from M L to M H by twin formation without passing any activated state. The other mechanism is a two-step transition through an intermediate orthorhombic state (O), where the molecules stand up from the M L state and then re-incline into the M H state. The subsecond time-resolved investigation by simultaneous measurements reveals dynamic variations during the transition. The former M L→M H transition appears at a lower temperature showing that twin formation requires lower energy, than the two-step process with the activated state. Continuous changing of intensities observed in the X-ray TV indicates that the latter M L→O→M H transition is caused by the coherent motion of the molecules.

12 – The use of oil palm biomass (OPB) fibers as reinforcements in composites

Abstract: There are tremendous demands of lightweight materials for use in transportation and construction sectors. Natural fibers (NFs) in reinforced polymer composites are relatively lightweight. However, NFs have some limitations due to their moisture affinity, poor wettability and low thermal stability during processing with synthetic polymers. These drawbacks have been overcome by effective physical and chemical treatments of NFs. Among various NFs, oil palm biomasses (OPBs) are readily available in some tropical countries and have received intense attention in the composite industries. In this chapter, the performance of untreated and differently treated OPB fibers, reinforced thermoplastic and thermoset composites prepared through extrusion, compression and injection moldings have been discussed in detail.

Laser Light and X-Ray Diffraction Studies of Oriented Isotactic Polypropylene (iPP) Prepared by Temperature Slope Crystallization

Isotactic polypropylene (iPP) film was melt-crystallized in a temperature gradient. The iPP film showed well oriented α- and β-crystalline textures along the gradient. The crystalline structure, phase transition boundary and lamellar twisting were examined by X-ray diffraction and laser light diffraction (LLD). On the α-β boundary, LLD shows a sharp streak perpendicular to the boundary, where the a-axis of the β-crystal is oriented perpendicular to the temperature gradient. Apart from the boundary, the a-axis of the β-crystal becomes parallel to the gradient. The β-crystal shows lamellar twisting with a pitch of 200 μm at room temperature. When heated the β-crystal, the lamellar distance of 295Å at room temperature decreases to 285Å at 80–100°C and then increases to more than 300Å above 120°C. During the heating, the value of the twist period increases from 200 to 210 μm at 90–100°C, and then to above 224 μm at 140°C. The increase of the twist period is related to the increasing crystalline thickness of the β-lamellae.