Search

Nonclassical features of crystallization in solution have been recently identified both experimentally and theoretically. In particular, an amorphous-phase-mediated pathway is found in various crystallization systems as an important route, different from the classical nucleation and growth model. Here, we utilize high-resolution in situ transmission electron microscopy with graphene liquid cells to study amorphous-phase-mediated formation of Ni nanocrystals. An amorphous phase is precipitated in the initial stage of the reaction. Within the amorphous particles, crystalline domains nucleate and eventually form nanocrystals. In addition, unique crystallization behaviors, such as formation of multiple domains and dislocation relaxation, are observed in amorphous-phase-mediated crystallization. Theoretical calculations confirm that surface interactions can induce amorphous precipitation of metal precursors, which is analogous to the surface-induced amorphous-to-crystalline transformation occurring in biomineralization. Our results imply that an unexplored nonclassical growth mechanism is important for the formation of nanocrystals.

In this study, poly(butylene adipate‐co‐terephthalate) (PBAT) biocomposites were generated from spent coffee grounds (SCGs) or torrefied SCG (TSCGs) using a melt compounding process. TSCGs were obtained at torrefaction temperatures of 230, 245, 260, 275, or 290°C for a duration of 60 min. Torrefaction enhanced the hydrophobicity, grindability, and biomass stability of the resulting composites by eliminating hemicellulose. Various concentrations of SCGs (10 and 20 wt.%) and TSCGs (10, 20, and 30 wt.%) were compounded into PBAT. The thermal, mechanical, and degradation properties of PBAT biocomposites were investigated. As SCGs and TSCGs were introduced, the crystallization temperature drastically increased. Compared with PBAT biocomposites with SCGs, PBAT biocomposites with TSCGs exhibited higher thermal stability and hydrophobicity, and improved mechanical properties. Further, alkaline hydrolysis occurred at a faster rate for biocomposites with biofillers than for neat PBAT. Therefore, this study demonstrated the improved compatibility between SCGs and PBAT by torrefaction. [ABSTRACT FROM AUTHOR]

Poly(butylene sebacate-co-terephthalate) (PBSeT) copolyesters are prepared by melt polymerization via two-step transesterification and polycondensation using pentaerythritol (PE) as a branching agent. The effects of the incorporated PE on its chemical, thermal, mechanical, and degradation properties, along with the rheological properties of its melt, are investigated. The highest molecular weight and intrinsic viscosity along with the lowest melt flow index were achieved at a PE content of 0.2 mol%, with minimal reduction in the tensile strength and the highest tear strength. The addition of PE did not significantly influence the thermal behavior and stability of the PBSeT copolyesters; however, the elongation at break decreased with increasing PE content. The sample with 0.2 mol% PE exhibited a higher storage modulus and loss modulus as well as a lower loss angle tangent than the other samples, indicating improved melt elasticity. The incorporation of more than 0.2 mol% PE enhanced the enzymatic degradation of copolyesters. In summary, including within 0.2 mol%, PE effectively improved both the processability-related characteristics and degradation properties of PBSeT copolyesters, suggesting their potential suitability for use in agricultural and packaging materials. [ABSTRACT FROM AUTHOR]

Poly (lactic acid) (PLA) is an important biodegradable plastic with unique properties. However, its widespread application is hindered by its low miscibility and suboptimal degradation properties. To overcome these limitations, we investigated the mechanical, thermal, and degradation properties of PLA and poly (butylene sebacate‐co‐terephthalate) (PBSeT) blends in the presence of poly (ethylene oxide) (PEO). Specifically, this study aimed to identify the effects of PEO as a compatibilizer and hydrolysis accelerator in PLA/PBSeT blends. PLA (80%) and PBSeT (20%) were melt blended with various PEO contents (2–10 phr), and their mechanical, thermal, and hydrolytic properties were analyzed. All PEO‐treated blends exhibited a higher elongation at break than that of the control sample, and the tensile strength was slightly reduced. In the PEO 10% sample, the elongation at break increased to 800% of that of the control sample. Differential scanning chromatography (DSC) analysis confirmed that when PEO was added to the PLA/PBSeT blends, the two glass transition temperatures (Tg) narrowed, resulting in improved miscibility of PLA and PBSeT. In addition, the hydrolytic degradation of the PLA/PBSeT/PEO blend accelerated as the PEO content increased. It was confirmed that PEO can act as a compatibilizer and hydrolysis‐accelerating agent for PLA/PBSeT blends. [ABSTRACT FROM AUTHOR]

Poly(butylene sebacate-co-terephthalate) (PBSeT) copolyesters are prepared by melt polymerization via two-step transesterification and polycondensation using pentaerythritol (PE) as a branching agent. The effects of the incorporated PE on its chemical, thermal, mechanical, and degradation properties, along with the rheological properties of its melt, are investigated. The highest molecular weight and intrinsic viscosity along with the lowest melt flow index were achieved at a PE content of 0.2 mol%, with minimal reduction in the tensile strength and the highest tear strength. The addition of PE did not significantly influence the thermal behavior and stability of the PBSeT copolyesters; however, the elongation at break decreased with increasing PE content. The sample with 0.2 mol% PE exhibited a higher storage modulus and loss modulus as well as a lower loss angle tangent than the other samples, indicating improved melt elasticity. The incorporation of more than 0.2 mol% PE enhanced the enzymatic degradation of copolyesters. In summary, including within 0.2 mol%, PE effectively improved both the processability-related characteristics and degradation properties of PBSeT copolyesters, suggesting their potential suitability for use in agricultural and packaging materials.