Effect of Nanofiller Content on Dynamic Mechanical and Thermal Properties of Multi-Walled Carbon Nanotube and Montmorillonite Nanoclay Filler Hybrid Shape Memory Epoxy Composites

Impact of Tung oil on a sustainable bio-based polymer, and development by zinc oxide nanoparticles

The use of natural and bio-based materials instead of petrochemicals is strongly recommended for reducing greenhouse gas emissions. Here we aim to promote the environmentally friendly bio-based polyester (P), prepared from biomass, with natural Tung oil (TO) plasticizer and zinc oxide nanoparticles (ZnO NPs) filler by 10-50%, and 3% to get a sustainable nanocomposite. The grafting altered the profile of neat P. Owing to insufficient contents, low concentrations have a slight impact, and high concentrations have more enhancements. The physical properties accompanied by curing of P/TO copolymer showed a decrease in viscosity, gelation time, and gelation-curing period for TO-based specimens, besides the lower heat emission during curing reaction, compared with that of P, by 3.4% and 4%, respectively, for P/TO-40 and P/TO-50 copolymers. The stability against exudation was promoted by 48.6%, where all concentrations of composites are more stable than P. P/TO-40 and P/TO-50 improved creep resistance by 62% and 88.1%, respectively, due to the stable surfaces. Furthermore, P/TO-50 concentration reduced hardness by 25%, but it was improved by ZnO NPs by 46.7%. Both TO plasticizer and nanofiller make the polymer capable of absorbing the flexural loading as a toughened composite. The proposed composites provide positive effects on the thermal behavior. Particularly, the P/TO-50 formula decreased the value of tan Delta by 35.5%; all composites increased Tg as well. The obtained data-results and SEM photos confirm the grafting and good distribution of TO plasticizer and ZnO NPs into P matrix through an improved and stable homogeneous bio-based polymer nanocomposite.

Kraft (Nano)Lignin as Reactive Additive in Epoxy Polymer Bio-Composites

The demand for high-performance bio-based materials towards achieving more sustainable manufacturing and circular economy models is growing significantly. Kraft lignin (KL) is an abundant and highly functional aromatic/phenolic biopolymer, being the main side product of the pulp and paper industry, as well as of the more recent 2nd generation biorefineries. In this study, KL was incorporated into a glassy epoxy system based on the diglycidyl ether of bisphenol A (DGEBA) and an amine curing agent (Jeffamine D-230), being utilized as partial replacement of the curing agent and the DGEBA prepolymer or as a reactive additive. A D-230 replacement by pristine (unmodified) KL of up to 14 wt.% was achieved while KL-epoxy composites with up to 30 wt.% KL exhibited similar thermo-mechanical properties and substantially enhanced antioxidant properties compared to the neat epoxy polymer. Additionally, the effect of the KL particle size was investigated. Ball-milled kraft lignin (BMKL, 10 μm) and nano-lignin (NLH, 220 nm) were, respectively, obtained after ball milling and ultrasonication and were studied as additives in the same epoxy system. Significantly improved dispersion and thermo-mechanical properties were obtained, mainly with nano-lignin, which exhibited fully transparent lignin-epoxy composites with higher tensile strength, storage modulus and glass transition temperature, even at 30 wt.% loadings. Lastly, KL lignin was glycidylized (GKL) and utilized as a bio-based epoxy prepolymer, achieving up to 38 wt.% replacement of fossil-based DGEBA. The GKL composites exhibited improved thermo-mechanical properties and transparency. All lignins were extensively characterized using NMR, TGA, GPC, and DLS techniques to correlate and justify the epoxy polymer characterization results.

Pushing the limits of PLA by exploring the power of MWCNTs in enhancing thermal, mechanical properties, and weathering resistance

The present study focuses on enhancing the mechanical, thermal, and degradation behavior of polylactic acid (PLA) by adding carbon nanotubes (CNTs) with different concentrations of 0.5, 1, 3, and 5%. The CNTs were prepared using catalytic chemical vapor deposition, and the prepared PLA/CNTs nanocomposite films were characterized using techniques such as FT-IR, Raman spectroscopy, TGA, SEM, and XRD. The distinct diffraction patterns of multi-walled carbon nanotubes (MWCNTs) at 2θ angles of 25.7° and 42.7° were no longer observed in the prepared nanocomposites, indicating uniform dispersion of MWCNTs within the PLA matrix. The presence of MWCNTs enhanced the crystallinity of PLA as the CNT loading increased. Mechanical tests demonstrated that incorporating CNTs positively influenced the elongation at the break while decreasing the ultimate tensile strength of PLA. The PLA-3%CNTs composition exhibited the highest elongation at break (51.8%) but the lowest tensile strength (64 MPa). Moreover, thermal gravimetric analysis confirmed that the prepared nanocomposites exhibited greater thermal stability than pure PLA. Among the nanocomposites, PLA-5% CNTs exhibited the highest thermal stability. Furthermore, the nanocomposites demonstrated reduced surface degradation in accelerated weathering tests, with a more pronounced resilience to UV radiation and moisture-induced deterioration observed in PLA-3% CNTs.