Accelerating the Biodegradation of Poly(lactic acid) through the Inclusion of Plant Fibers: A Review of Recent Advances.

As the global demand for plastics continues to grow, plastic waste is accumulating at an alarming rate with negative effects on the natural environment. The industrially compostable biopolymer poly(lactic acid) (PLA) is therefore being adopted for use in many applications, but the degradation of this material is slow under many end-of-life conditions. This Perspective explores the feasibility of accelerating the degradation of PLA through the formation of PLA-plant fiber composites. Topics include: (a) key properties of PLA, plant-based fibers, and biocomposites; (b) mechanisms of both hydrolytic degradation and biodegradation of PLA-fiber composites; (c) end-of-life degradation of PLA and PLA-plant fiber composites in aerobic and anaerobic conditions, relevant to compost, soil and seawater (aerobic), and landfills (anaerobic); and (d) sustainability and environmental impact of PLA and PLA-plant fiber composites, as evaluated using life cycle assessment. Additional degradation modes, including thermal and photodegradation, which are relevant during processing and use, have been omitted for clarity, as have other types of PLA biocomposites. Multiple studies have shown that the addition of some types of plant fibers to PLA (to form PLA biocomposites) accelerates both water transport in the material and hydrolysis, presenting a possible avenue for improving the end-of-life degradation of these materials. To facilitate the continued development of materials with enhanced biodegradability, we identify a need to implement testing protocols that can distinguish between different degradation mechanisms.

Bio-composites from spent hen derived lipids grafted on CNC and reinforced with nanoclay.

A novel cellulose nanocrystal (CNC)-grafted macromonomer containing both saturated and unsaturated fatty acids was synthesized from spent hen lipids, which was further homopolymerized and copolymerized with styrene and in-situ nano-reinforced into nanocomposites. The aim of this study was to investigate the effect of CNC-grafting and nanoclay as filler at different ratios on the thermal, mechanical and water absorption behavior of the developed composites. The chemical grafting on CNC, its polymerization and effect of nanofiller were characterized and investigated by various analytical techniques. The results revealed improved thermal stability for all nanocomposites with higher onset of degradation temperature and more char production for 5% and 10% nanoclay composites, while increased tensile strength was obtained for all nanoclay composites. However, reduced storage modulus and higher moisture uptake was observed for nanocomposites compared to the control polymer composite, which can be attributed to poor interfacial adhesion between nanofiller and matrices, and hydrophilic nature of nanofillers, respectively.

Valorization of Hemp Hurds as Bio-Sourced Additives in PLA-Based Biocomposites.

Sourced from agricultural waste, hemp hurds are a low-cost renewable material with high stiffness; however, despite their potential to be used as low-cost filler in natural fiber reinforced polymer biocomposites, they are often discarded. In this study, the potential to add value to hemp hurds by incorporating them into poly(lactic acid) (PLA) biopolymer to form bio-based materials for packaging applications is investigated. However, as with many plant fibers, the inherent hydrophilicity of hemp hurds leads to inferior filler-matrix interfacial interactions, compromising the mechanical properties of the resulting biocomposites. In this study, two chemical treatments, alkaline (NaOH) and alkaline/peroxide (NaOH/H2O2) were employed to treat hemp hurds to improve their miscibility with poly(lactic acid) (PLA) for the formation of biocomposites. The effects of reinforcement content (5, 10, and 15 wt. %), chemical treatments (purely alkaline vs. alkaline/peroxide) and treatment cycles (1 and 3 cycles) on the mechanical and thermal properties of the biocomposites were investigated. The biocomposites of treated hemp hurd powder exhibited enhanced thermal stability in the temperature range commonly used to process PLA (130-180 °C). The biocomposites containing 15 wt. % hemp hurd powder prepared using a single-cycle alkaline/peroxide treatment (PLA/15APHH1) exhibited a Young's modulus of 2674 MPa, which is 70% higher than that of neat PLA and 9.3% higher than that of biocomposites comprised of PLA containing the same wt. % of untreated hemp hurd powder (PLA/15UHH). Furthermore, the tensile strength of the PLA/15APHH1 biocomposite was found to be 62.6 MPa, which was 6.5% lower than that of neat PLA and 23% higher than that of the PLA/15UHH sample. The results suggest that the fabricated PLA/hemp hurd powder biocomposites have great potential to be utilized in green and sustainable packaging applications.

1-Ethyl-4-{2-[1-(4-methyl-phen-yl)ethyl-idene]hydrazinyl-idene}-3,4-dihydro-1H-2λ(6),1-benzothia-zine-2,2-dione.

In the title compound, C(19)H(21)N(3)O(2)S, the dihedral angle between the aromatic rings is 6.7 (2)° and the C=N-N=C torsion angle is 178.0 (2)°. The conformation of the thia-zine ring is an envelope, with the S atom displaced by 0.802 (2) Šfrom the mean plane of the other five atoms (r.m.s. deviation = 0.022 Å). In the crystal, mol-ecules are linked by C-H⋯O inter-actions, generating C(5) chains propagating in [010]. A weak C-H⋯π inter-action is also observed.

6-Bromo-4-(2-cyclo-hexyl-idenehydrazin-1-yl-idene)-1-methyl-2,2-dioxo-3,4-dihydro-1H-2λ(6),1-benzothia-zine.

The asymmetric unit of the title compound, C(15)H(18)BrN(3)O(2)S, contains two independent mol-ecules in both of which the (thia-zine)C=N-N double bond exhibits an E conformation. The cyclo-hexyl rings adopt chair conformations while the thia-zine rings are in sofa conformations. The mean planes of these rings are oriented at dihedral angles of 64.43 (13) and 28.6 (2)° in the two independent mol-ecules while the aromatic and thia-zine rings are twisted by dihedral angles of 8.73 (8) and 13.07 (2)°, respectively. In the crystal, C-H⋯O and C-H⋯Br inter-actions connect mol-ecules into chains propagating along the a axis.

Spiraeamide, new sphingolipid from Spiraea brahuica.

Spiraeamide, a new sphingolipid, has been isolated from the ethyl acetate-soluble fraction of the methanolic extract of the whole plant of Spiraea brahuica, along with marrubiin, 19-acetylmarrubenol, and 6-acetylmarruenol. Their structures were elucidated by ¹H and ¹³C NMR spectra, and COSY, NOESY, HMQC, HMBC, EI-MS, and FAB-MS experiments.

Cytotoxic geranylflavonoids from Bonannia graeca.

The analysis of the aerial parts of Bonannia graeca led to the isolation and characterization of polar geranylated flavonoids (6 and 7). The structure elucidation was performed by extensive spectroscopic methods (1D and 2D NMR) and comparison with literature data. All natural flavonoids isolated from B. graeca (1-7) and some synthetic derivatives (8-11) were tested for cytotoxic activity against four human tumor cell lines. Preliminary structure-activity relationship correlations are discussed.

Structural determination of crotamides A and B, the new amides from Croton sparsiflorus.

Two new amides crotamides A and B, have been isolated from the n-hexane soluble fraction of Croton sparsiflorus in addition to salisomide and N-(4-hydroxyphenethyl)-octacosanamide reported for the first time from this species. Their structures were assigned from spectral data including 1D and 2D NMR spectroscopic data.

Asphorodin, a potent lipoxygenase inhibitory triterpene diglycoside from Asphodelus tenuifolius.

Asphorodin (1), a new diglycoside, has been isolated from the ethyl acetate-soluble fraction of Asphodelus tenuifolius. It showed significant inhibitory activity against the enzyme lipoxygenase in a concentration-dependent manner. The Lineweaver-Burk and Dixon plots indicated that the nature of inhibition was non-competitive.