Measuring in-situ X-ray scattering of natural rubber biaxial deformation: A new equipment for polymer studies

This research is supported by national funds through the FCT (Portuguese Foundation for Science and Technology)/MCTES (PIDDAC) under the projects UIDB/04044/2020, UIDP/04044/2020, Associate Laboratory ARISE LA/P/0112/2020 and PAMI—ROTEIRO/0328/2013 (Nº 022158) and UID/Multi/04044/2013.Understanding biaxial deformation is essential for a more realistic evaluation of rubber elasticity compared to the more usual uniaxial deformation. To study crystallisation occurring during biaxial deformation of natural rubber films, a new simple equipment has been designed and assembled. The equipment, mounted in the beamline of ALBA synchrotron light source facility, allowed the in-situ measurement of X-ray scattering of natural rubber during biaxial deformation. This work provides, for the first time, quantitative information on crystallisation during biaxial extension.info:eu-repo/semantics/publishedVersio

Development of Biodegradable Thermosetting Plastic Using Dialdehyde Pineapple Stem Starch

Starch extracted from pineapple stem waste underwent an environmentally friendly modification process characterized by low-energy consumption. This process resulted in the creation of dialdehyde pineapple stem starch featuring varying aldehyde contents ranging from 10% to 90%. Leveraging these dialdehyde starches, thermosetting plastics were meticulously developed by incorporating glycerol as a plasticizer. Concurrently, unmodified pineapple stem starch was employed as a control to produce thermoplastic material under identical conditions. The objective of streamlining the processing steps was pursued by adopting a direct hot compression molding technique. This enabled the transformation of starch powders into plastic sheets without the need for water-based gelatinization. Consequently, the dialdehyde starch-based thermosetting plastics exhibited exceptional mechanical properties, boasting a modulus within the range of 1862 MPa to 2000 MPa and a strength of 15 MPa to 42 MPa. Notably, their stretchability remained relatively modest, spanning from 0.8% to 2.4%. Comparatively, these properties significantly outperformed the thermoplastic counterpart derived from unmodified starch. Tailoring the mechanical performance of the thermosetting plastics was achieved by manipulating the glycerol content, ranging from 30% to 50%. Phase morphologies of the thermoset starch unveiled a uniformly distributed microstructure without any observable starch particles. This stood in contrast to the heterogeneous structure exhibited by the thermoplastic derived from unmodified starch. X-ray diffraction patterns indicated the absence of a crystalline structure within the thermosets, likely attributed to the establishment of a crosslinked structure. The resultant network formation in the thermosets directly correlated with enhanced water resistance. Remarkably, the thermosetting starch originating from pineapple stem starch demonstrated continued biodegradability following a soil burial test, albeit at a notably slower rate when compared to its thermoplastic counterpart. These findings hold the potential to pave the way for the utilization of starch-based products, thereby replacing non-biodegradable petroleum-based materials and contributing to the creation of more enduring and sustainable commodities

Revisiting the morphology, microstructure, and properties of cellulose fibre from pineapple leaf so as to expand its utilization

Pineapple leaf waste is an agricultural product that is available in large quantities and is still under-utilized. Therefore, the aim of this work was to investigate the morphology, microstructure, and mechanical properties of pineapple leaf fibre (PALF) such that its full potential may be realized. Pineapple leaf, its fibre bundles and elementary fibres have been investigated. Morphology, size, and mechanical properties of fibre bundles extracted from different parts (i.e. bottom, middle and top) of a leaf were studied. It was found that the PALF obtained from vascular tissue and from the mesophyll have different macroscopic shapes. Both, however, contain micron-size elementary fibres of similar size and shape. Size and properties of fibre bundles change from the bottom end of a leaf toward the top end. Pineapple leaf microfibre (PALMF) was found to be smaller in diameter than other natural fibres. It is also very long and its structure changes according to its position along the leaf. At the bottom end a clear and large central hole or lumen can be observed. At the top the lumen becomes almost undetectable. The mechanical strength of PALMF appears to decrease, albeit very slightly, toward the tip of the leaf. The mechanical properties of the fibres are relatively high and comparable to that of flax and hemp fibres which are widely studied and used as reinforcing materials in composites. Very long microfibre can easily be obtained from fibre bundles by dissolving the binding matrix. Potential applications for this microfibre are suggested

Comparative Study of Flax and Pineapple Leaf Fiber Reinforced Poly(butylene succinate): Effect of Fiber Content on Mechanical Properties

In this study, we compare the reinforcing efficiency of pineapple leaf fiber (PALF) and cultivated flax fiber in unidirectional poly(butylene succinate) composites. Flax, known for robust mechanical properties, is contrasted with PALF, a less studied but potentially sustainable alternative. Short fibers (6 mm) were incorporated at 10 and 20% wt. levels. After two-roll mill mixing, uniaxially aligned prepreg sheets were compression molded into composites. At 10 wt.%, PALF and flax exhibited virtually the same stress–strain curve. Interestingly, PALF excelled at 20 wt.%, defying its inherently lower tensile properties compared to flax. PALF/PBS reached 70.7 MPa flexural strength, 2.0 GPa flexural modulus, and 107.3 °C heat distortion temperature. Comparable values for flax/PBS were 57.8 MPa, 1.7 GPa, and 103.7 °C. X-ray pole figures indicated similar matrix orientations in both composites. An analysis of extracted fibers revealed differences in breakage behavior. This study highlights the potential of PALF as a sustainable reinforcement option. Encouraging the use of PALF in high-performance bio-composites aligns with environmental goals

Identification of Active Species in Photodegradation of Aqueous Imidacloprid over g-C₃N₄/TiO₂ Nanocomposites

In this work, g-C3N4/TiO2 composites were fabricated through a hydrothermal method for the efficient photocatalytic degradation of imidacloprid (IMI) pesticide. The composites were fabricated at varying loading of sonochemically exfoliated g-C3N4 (denoted as CNS). Complementary characterization results indicate that the heterojunction between the CNS and TiO2 formed. Among the composites, the 0.5CNS/TiO2 material gave the highest photocatalytic activity (93% IMI removal efficiency) under UV-Vis light irradiation, which was 2.2 times over the pristine g-C3N4. The high photocatalytic activity of the g-C3N4/TiO2 composites could be ascribed to the band gap energy reduction and suppression of photo-induced charge carrier recombination on both TiO2 and CNS surfaces. In addition, it was found that the active species involved in the photodegradation process are OH• and holes, and a possible mechanism was proposed. The g-C3N4/TiO2 photocatalysts exhibited stable photocatalytic performance after regeneration, which shows that g-C3N4/TiO2 is a promising material for the photodegradation of imidacloprid pesticide in wastewater

Processing and properties of pineapple leaf fibers-polypropylene composites prepared by twin-screw extrusion

Pineapple leaf fiber (PALF) is an agricultural waste, very abundant in some countries of East Asia (India, Thailand, and Philippines). Owing to its intrinsic mechanical properties, it could be used as a reinforcing fiber for thermoplastic polymers. In this article, PALF was used to prepare polypropylene-based composites by twin-screw extrusion. The variations of the fiber dimensions (length, diameter, and aspect ratio) induced by the compounding process was analyzed. PALF suffer from a significant reduction in length, but the bundles are very difficult to separate and their diameter remains almost constant. The change in fiber length and aspect ratio along the screw profile showed an exponential decrease, as already observed for other lignocellulosic fibers. The mechanical properties of composites prepared with 20 wt% PALF fibers show an increase in Young's modulus (146%) and stress at break (112%), but a strong decrease in elongation at break (298%). These results confirm the potential value of this agricultural waste as effective reinforcing fiber for polymer composites