This paper reports a single step reactive extrusion process for fabrication of thermally stable, polylactic acid grafted cellulose nanocrystal(PLA-g-CNC) nanocomposite films using dicumyl peroxide as ...crosslinking agent. PLA-g-CNC nanocomposites were recycled without significant breakage in the molecular structure of PLA. The grafted PLA chains shields the sulfate and hydroxyl groups of CNCs, thereby enhancing the compatibilization with PLA matrix and preventing thermal degradation during extrusion. NMR and FTIR spectroscopy studies showed that amorphous PLA chains grafted on CNC surface through C–C bonds formation. Presence of such chemical crosslinks led to efficient transfer of modulus of CNCs to PLA matrix, thereby improving the tensile strength and young's modulus by∼40% and∼490%,respectively. Recycling of PLA-g-CNC doesn't alter the molecular weight, thermal, crystallization and mechanical properties of the nanocomposites significantly. Therefore, the current study provides a novel approach for fabricating CNC-reinforced-PLA nanocomposites which can be easily recycled and reused for multiple cycles.
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•PLA chains grafted onto CNC surface (PLA-g-CNC) through C–C bond formation in presence of dicumyl peroxide radical.•PLA-g-CNC nanocomposite films were found to be thermally stable and could be recycled.•PLA-g-CNC films shows uniform dispersion of CNC due to the efficient grafting, results in improvement in tensile strength.•Crystalline behavior and elastic properties of resulting composites improved with increase in the CNC loadings.
Cellulose nanocrystals (CNC) are fabricated from filter paper (as cellulosic source) by acid hydrolysis using different acids such as sulphuric (H2SO4), phosphoric (H3PO4), hydrochloric (HCl) and ...nitric (HNO3) acid. The resulting acid derived CNC are melt mixed with Polylactic acid (PLA) using extruder at 180°C. Thermogravimetric (TGA) result shows that increase in 10% and 50% weight loss (T10, T50) temperature for PLA-CNC film fabricated with HNO3, H3PO4 and HCl derived CNC have improved thermal stability in comparison to H2SO4-CNC. Nonisothermal kinetic studies are carried out with modified-Coats-Redfern (C-R), Ozawa-Flynn-Wall (OFW) and Kissinger method to predict the kinetic and thermodynamic parameters. Subsequently prediction of these parameter leads to the proposal of thermal induced degradation mechanism of nanocomposites using Criado method. The distribution of Ea calculated from OFW model are (PLA-H3PO4-CNC: 125–139 kJmol−1), (PLA-HNO3-CNC: 126–145 kJmol−1), (PLA-H2SO4-CNC: 102–123 kJmol−1) and (PLA-HCl-CNC: 140–182 kJmol−1). This difference among Ea for the decomposition of PLA-CNC bionanocomposite is probably due to various acids used in this study. The Ea calculated by these two methods are found in consonance with that observed from Kissinger method. Further, hyphenated TG-Fourier transform infrared spectroscopy (FTIR) result shows that gaseous products such as CO2, CO, lactide, aldehydes and other compounds are given off during the thermal degradation of PLA-CNC nanocomposite.
This paper reports a single-step co-precipitation method for the fabrication of magnetic cellulose nanocrystals (MGCNCs) with high iron oxide nanoparticle content (∼51 wt % loading) adsorbed onto ...cellulose nanocrystals (CNCs). X-ray diffraction (XRD), Fourier transform infrared (FTIR), and Raman spectroscopic studies confirmed that the hydroxyl groups on the surface of CNCs (derived from the bamboo pulp) acted as anchor points for the adsorption of Fe3O4 nanoparticles. The fabricated MGCNCs have a high magnetic moment, which is utilized to orient the magnetoresponsive nanofillers in parallel or perpendicular orientations inside the polylactic acid (PLA) matrix. Magnetic-field-assisted directional alignment of MGCNCs led to the incorporation of anisotropic mechanical, thermal, and electrical properties in the fabricated PLA–MGCNC nanocomposites. Thermomechanical studies showed significant improvement in the elastic modulus and glass-transition temperature for the magnetically oriented samples. Differential scanning calorimetry (DSC) and XRD studies confirmed that the alignment of MGCNCs led to the improvement in the percentage crystallinity and, with the absence of the cold-crystallization phenomenon, finds a potential application in polymer processing in the presence of magnetic field. The tensile strength and percentage elongation for the parallel-oriented samples improved by ∼70 and 240%, respectively, and for perpendicular-oriented samples, by ∼58 and 172%, respectively, in comparison to the unoriented samples. Furthermore, its anisotropically induced electrical and magnetic properties are desirable for fabricating self-biased electronics products. We also demonstrate that the fabricated anisotropic PLA–MGCNC nanocomposites could be laminated into films with the incorporation of directionally tunable mechanical properties. Therefore, the current study provides a novel noninvasive approach of orienting nontoxic bioderived CNCs in the presence of low magnetic fields, with potential applications in the manufacturing of three-dimensional composites with microstructural features comparable to biological materials for high-performance engineering applications.
The present work demonstrates the formulation of cellulose nanofiber (CNF) or magnetic cellulose nanofiber (mgCNF) dispersed chitosan-based edible nanocoating with superior mechanical, thermal, ...optical, and texture properties. The fabrication of mgCNF is successfully achieved through a single-step coprecipitation route, where iron particles get adsorbed onto CNF. The thermal stability of mgCNF is improved considerably, where ∼17% reduction in weight is observed, whereas CNF degrades completely under identical conditions. TGA analysis shows that there is an improvement in thermal stability for both CNF- and mgCNF-reinforced CS nanocoatings, where mgCNF provides more heat dimensional stability than CNF-dispersed CS nanocoatings. Further, the edible nanocoatings are stable even at the temperature of heat treatment such as food sterilization. The mechanical property of the mgCNF-dispersed chitosan (CS) shows a remarkable improvement in tensile strength (57.86 ± 14 MPa) and Young’s modulus (2348.52 ± 276 MPa) in comparison to neat CS (6.27 ± 0.7 and 462.36 ± 64 MPa, respectively). To determine the developed materials to be safe for food, the quantification of iron is made by using ICP-MS technique. It is worth mentioning that mgCNF-coated CS helps in improving the texture of cut pineapples in comparison with uncoated pineapple slices under ambient conditions.
This work reports the fabrication of four varieties of cellulose nanocrystals(CNCs) through hydrolysis with different acids which leads to their tailored physical, structural, thermal and surface ...characteristics. The hydroxyl groups of CNCs are substituted with anionic-moieties from acid which alters its interfacial interaction with PLA matrix, as predicted from dispersion surface energy and work of adhesion values. Interestingly, tunable aspect ratios of various acid-derived CNCs have substantial effect on mechanical reinforcing-efficiency and thermal behavior of nanocomposites. CNCs with high aspect ratio improved the elastic modulus of nanocomposites whereas with low aspect ratio accelerated the crystallization rate. The different acid-derived CNCs shows heterogeneous nucleation-driven crystallization phenomenon with propagation of PLA spherulites in three dimensions. Lauritzen-Hoffmann parameters shows that growth of PLA crystals are restricted requiring higher activation-energy to initiate nucleation process. Therefore, this study provides an alternative approach of selecting the appropriate acid-hydrolyzed CNCs for fabrication of CNC-reinforced polymeric nanocomposites with desired properties.
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•Different acid-hydrolyzed CNCs shows tailored physical and surface characteristics.•Dispersion of CNCs in PLA matrix could be predicted from surface energy parameters.•CNCs with lower aspect ratio accelerated the crystallization rate.•CNCs with higher aspect ratio improved mechanical reinforcement effect.•CNCs induced heterogeneous nucleation phenomenon with 3-D growth of spherulites.
•Microwave assisted transesterification of soybean oil.•Microwave assisted poly (lactic acid) oligomer preparation.•Cold flow properties characterization of ethyl lactate stabilized ...oligomer-biodiesel system.•Engine performance and emission characteristics.
In this study, the effect of poly (lactic acid)-oligomer (OLLA) on cold flow properties, IC engine performance and subsequently, exhaust gas emission characteristics is evaluated using microwave synthesized biodiesel from soybean oil. Biodiesel was synthesized by achieving maximum 99% conversion using KOH as catalyst at 60°C under optimum reaction time of five minutes. Cloud point, pour point, flash point and fire point of synthesized biodiesel were analyzed as reference properties. OLLA is synthesized in absence of catalyst at 150°C with the targeted molecular weight Mn∼1000Da and density ∼1.21gm/cm3. Subsequently, by blending ethyl lactate stabilized OLLA with biodiesel, the cloud point, pour point, flash point and fire point were reduced significantly. Polarizing optical microscopic images during temperature scan relate the effect of OLLA on cloud point crystal morphology which delayed the crystal formation with reduction in crystal nucleation density and size of the crystals. Rheological analyses are conducted to understand the Newtonian flow regime at lower temperature and change in the viscosity and flow activation energy of biodiesel in the presence of neat as well as with ethyl lactate stabilized OLLA. The engine performance test reveals the comparative utilization of brake specific fuel consumption and break thermal efficiency with significant reduction in carbon monoxide and incombustible hydrocarbon in the exhaust gases. Hence, present research demonstrates the use of OLLA for improvement in the cold flow properties of biodiesel and the exhaust gas emission characteristics.
Abstract
This present study demonstrated the preparation of a highly crystalline anatase (ana) form of titanium oxide (TiO
2
) doped silk nanocrystal (SNC) nanohybrid (ana-TCS) of diameter (7.5 ± ...1.4 nm) by the sol–gel method using titanium (IV) butoxide as the hydrolysis material. This prepared nanohybrid with surface hydroxyl groups acted as a co-initiator for the synthesis of poly(L-lactic acid) (PLLA)-g-ana-TSC nanocomposite with grafted PLLA chains via the in situ polymerization technique, using tin-octoate as a catalyst. The fabricated nanocomposite had a high number average molecular weight of 83 kDa with good processibility. This prepared nanocomposite was hydrophobic in nature, with a contact angle of 105°, which was further enhanced to 122 ± 1° when processed via electrospinning technique into a non-woven fabric. The prepared nanocomposite could degrade up to 43% methylene blue dye in 15 days. This nanocomposite showed no significant molecular weight reduction after 1 h of aqeous treatment, which could be attributed to its hydrophobic nature, inhibiting its degradation. However, 50% degradation was observed for the nanocomoposite whereas, PLLA demonstrated 25% degradation in 15 days, after its end-of-life. Thus, this study revealed that the in situ synthesized PLA-ana-TCS nanocomposite could be targeted for use as a hydrophobic, self-cleaning, dye-degradable fabric.
Pineapple is a tropical fruit that is the most economically significant member of the Bromeliaceae family that are rich in flavonoids, phenolic acids, and antioxidants, which protect human cells from ...free radicals known to cause chronic diseases. However, short postharvest shelf-life of the fruit limits its long-distance distribution and consumption. Chitosan is a positively charged polysaccharide consisting of N-acetyl d-glucosamine and d-glucosamine units that can be used as a promising sustainable biopolymer for active coating of the fruit. In this work, chitosan-based nanocomposite formulations were prepared with added eugenol (clove essential oil) and Aloe vera gel as antioxidant, antibacterial and antifungal agents. The results showed that the incorporation of eugenol oil nanoemulsion and Aloe vera gel in the coatings enhanced their physico-chemical and functional properties including antimicrobial activities against four foodborne bacterial pathogens (Escherichia coli, Alcaligenes faecalis, Staphylococcus aureus, and Bacillus subtilis) and two fungal isolates. The developed coatings not only kept the pineapple fresh, but also preserved its quality and prolonged their shelf-life by up to three weeks during storage in ambient conditions.
•Pineapple is a perishable fruit, whose shelf-life enhancement is important.•Chitosan based active and composite coating formulations were developed.•Aloe vera gel and eugenol nanoemulsion enhanced functionalities of the coating.•Shelf-life of the fruit was extended by up to 3 weeks at ambient conditions.•The developed coating is an effective alternative to synthetic wax-based coating.
In this paper, review on fabrication of scaffolds through solvent casting particle leaching method has been done. The addition of different biodegradable based and ceramic based composite has been ...covered for bone tissue replacement or repairing. The synthetic biopolymers and composites that are used for fabrication of scaffolds are reviewed. Scaffold requirements in terms of their mechanical properties, pore structure along with other biological and mechanical properties are discussed. Various methods for fabricating scaffolds merits, demerits along with their applications are successfully discussed. Addition of bioactive factors like bioceramics, demineralised bone particles and their effects during invivo and invitro conditions has also been covered. Finally, highlights on the challenges faced in solvent casting particle leaching methods, suggestions for further research and development has been expressed.
