Effect of alkali treatment and fibre composition on the performance of pineapple leaf fibre-polyvinyl alcohol composites

This paper studied the properties of composites based on polyvinyl alcohol reinforced with pineapple leaf fibres (PALF/PVA). The surface of pineapple leaf fibres (PALF) has been previously treated with 6% sodium hydroxide solution. The influence of fibre loading and fibre surface treatment were examined. Analysis by Fourier transform infrared spectroscopy (FTIR), and X-ray diffraction (XRD) displayed physico-chemical changes on treated PALF/PVA composites compared to untreated PALF/PVA composites. The results from thermogravimetric analysis (TGA) showed that the introduction of untreated PALF into the composites enhanced the thermal stability of the composites. Progressive improvement of thermal stability was discovered by associating treated PALF with the composites. The treated PALF composites produced also improved mechanical properties with increasing fibre content. Differential scanning calorimetric (DSC) analyses showed no significant changes in melting temperatures upon incorporating untreated PALF into the PALF/PVA composites. The best improvement in tensile strength value was obtained for treated PALF composite having 3 wt% of fibre loading, with enhancements of about 11% and 54%, compared to untreated PALF composites and plain PVA matrix, respectively

Mesomorphic and optical properties of azo-ester liquid crystalline reactive mesogens with enhanced thermal stability

A series of azo-ester-linked polymerizable liquid crystalline compounds M1-M3, containing lateral methyl substitution and different terminal alkoxy substituents, e.g., −OCH3, −OCH2CH3, and −OCH2CH2CH3 have successfully been synthesized and characterized. The chemical structures of the prepared compounds were confirmed by different spectroscopic techniques. Thermogravimetric analysis revealed that all the compounds exhibited excellent thermal stability and showed two-staged decomposition patterns. The optical microscopic study revealed that all compounds displayed only the nematic phase and lateral substituent played a crucial role in the formation of single mesophase. The broad X-ray scattering peaks for M1, M2, and M3 in the 2.5–5.5 nm−1 region was observed at temperatures of 154 °C, 85 °C, and 129 °C, respectively, upon cooling from the isotropic liquid, confirming the existence of nematic mesophase. The electronic spectra of M1-M3 showed two main absorption bands with λmax ranges of 263–266 and 369–377 nm. The E-Z photoisomerization study of M1-M3 showcased that the processes followed the first-order kinetic, and the isomerization rate decreased as the alkoxy chain length increased. On the contrary, the Z-E thermal isomerization rates for M1-M3 showed insignificant changes as the alkoxy chain length increased

Mesomorphic and optical properties of azo-ester liquid crystalline reactive mesogens with enhanced thermal stability

A series of azo-ester-linked polymerizable liquid crystalline compounds M1-M3, containing lateral methyl substitution and different terminal alkoxy substituents, e.g., −OCH3, −OCH2CH3, and −OCH2CH2CH3 have successfully been synthesized and characterized. The chemical structures of the prepared compounds were confirmed by different spectroscopic techniques. Thermogravimetric analysis revealed that all the compounds exhibited excellent thermal stability and showed two-staged decomposition patterns. The optical microscopic study revealed that all compounds displayed only the nematic phase and lateral substituent played a crucial role in the formation of single mesophase. The broad X-ray scattering peaks for M1, M2, and M3 in the 2.5–5.5 nm−1 region was observed at temperatures of 154 °C, 85 °C, and 129 °C, respectively, upon cooling from the isotropic liquid, confirming the existence of nematic mesophase. The electronic spectra of M1-M3 showed two main absorption bands with λmax ranges of 263–266 and 369–377 nm. The E-Z photoisomerization study of M1-M3 showcased that the processes followed the first-order kinetic, and the isomerization rate decreased as the alkoxy chain length increased. On the contrary, the Z-E thermal isomerization rates for M1-M3 showed insignificant changes as the alkoxy chain length increased

The Effect of Acid Hydrolysis Parameters on the Properties of Nanocellulose Extracted from Almond Shells

The effects of acid hydrolysis parameters (acid type, acid concentration, reaction time, and temperature) on the properties of nanocellulose (NC) extracted from almond shells were investigated. The highest percentage yield of NC obtained from each type of acid was 71.8% using 25% w/v sulfuric acid at 50°C for 60 min, followed by 71.1% with 50% w/v perchloric acid at 35°C for 15 min, and finally 67% with 50% w/v methane sulfonic acid at 25°C for 10 min. The hydrolysis treatment using sulfuric and perchloric acids greatly affect the NC particle size and length. The extracted NCs show different thermal degradation profiles due to the difference in the crystallinity index and types of acid used. Hydrolysis with strong acids (sulfuric and perchloric acids) produce NC with lower crystallinity due to the degradation of both amorphous and crystalline regions in the cellulose. Furthermore, BET analysis revealed the NCs from the hydrolysis using sulfuric acid possesses the highest surface area, desorption/adsorption pore diameter, desorption, and adsorption cumulative pore volume compared to other acids

Synthesis of imine-ester-linked benzothiazole mesogen containing liquid crystalline monomers with different terminal substituents

<p>A series of imine-ester-linked benzothiazole mesogen-based liquid crystalline (LC) monomers (<b>M1–M4</b>) having polymerizable methacrylate functional group as the terminal were designed and synthesized. These monomers were differentiated from each other by varying the terminal substituents (-H, -CH₃, -OCH₃, and -OCH₂CH₃) at the sixth position on the benzothiazole moiety. The chemical structures of the synthesized monomers were characterized and confirmed by spectroscopic techniques such as FTIR, ¹H NMR, and ¹³C NMR. Thermogravimetric analysis (TGA) was used to study the thermal properties of the investigated monomers. The ethoxy substituted monomer (<b>M4</b>) showed higher thermal stability compared with the other monomers. The mesomorphic behavior of all the monomers was studied using differential scanning calorimetry (DSC) and polarized optical microscopy (POM). DSC and POM studies revealed that the monomer (<b>M1</b>) having no substituent at the sixth position on the benzothiazole ring exhibited both smectic and nematic mesophases, whereas -CH₃-, -OCH₃-, and -OCH₂CH₃-substituted compounds revealed only nematic mesophase.</p