Biodegradable poly(ethylene succinate) nanocomposites. Effect of filler type on thermal behaviour and crystallization kinetics

Probing into the nucleation and reinforcing effects of poly (vinyl acetate) grafted cellulose nanocrystals in melt-processed poly (lactic acid) nanocomposites

Blending poly (lactic acid) (PLA) with cellulose nanocrystals (CNCs) to fabricate nanocomposites is a valuable strategy to improve the properties of PLA without sacrificing its biodegradability. However, the nucleation and reinforcing mechanisms of CNCs for semi-crystalline PLA matrix are still elusive in melt-processed PLA/CNC nanocomposites. Herein, poly (vinyl acetate) (PVAc) chains were grafted onto the surface of CNCs via an efficient radical polymerization in an aqueous medium, making CNCs suitable for conventional melting processing techniques. It is found that the dispersion state of CNCs in the PLA matrix and the interface interaction between PLA and CNCs can be tailored by varying the PVAc grafting density. Further studies show that well-dispersed CNCs play a positive role in reinforcing PLA. But unexpectedly, the nucleation effect is suppressed even though the homogeneous dispersion of CNCs is achieved with higher PVAc grafting density because the rich PVAc chains at the interface dilute the PLA chains, thus hindering the nucleation and spherulite growth of PLA. This research sheds light on the nucleation and reinforcing mechanisms of polymer grafted CNCs, and will provide theoretical guidance for the industrialization of high-performance bio-based nanocomposites.

Significantly Enhanced Crystallization of Poly(ethylene succinate-co-1,2-propylene succinate) by Cellulose Nanocrystals as an Efficient Nucleating Agent

Poly(ethylene succinate-co-1,2-propylene succinate) (PEPS) is a novel aliphatic biodegradable polyester with good mechanical properties. Due to the presence of methyl as a side group, the crystallization rate of PEPS is remarkably slower than that of the poly(ethylene succinate) homopolymer. To promote the potential application of PEPS, the effect of cellulose nanocrystals (CNC) on the crystallization behavior, crystalline morphology, and crystal structure of PEPS was investigated in this research with the aim of increasing the crystallization rate. CNC enhanced both the melt crystallization behavior of PEPS during the cooling process and the overall crystallization rate during the isothermal crystallization process. The crystallization rate of PEPS became faster with an increase in CNC content. The crystalline morphology study directly confirmed the heterogeneous nucleating agent role of CNC. The crystal structure of PEPS remained unchanged in the composites. On the basis of the interfacial energy, the nucleation mechanism of PEPS in the composites was further discussed by taking into consideration the induction of CNC.

Superior Crystallization Kinetics Caused by the Remarkable Nucleation Effect of Graphene Oxide in Novel Ternary Biodegradable Polymer Composites

In this study, novel ternary composites were prepared, including biodegradable poly(ethylene succinate) (PESu), poly(ethylene glycol) (PEG), and graphene oxide (GO). We have conducted a comprehensive study on whether GO can successfully promote the crystallization behaviors of PESu in the ternary composites. The results of isothermal crystallization demonstrated that with the increase of GO content in the composite (at a fixed PESu/PEG ratio), the Avrami rate constant k gradually increased, indicating that the crystallization rate was faster when GO was added to the composite. The same phenomenon was also found for nonisothermal crystallization. It was found that the Mo model can adequately describe the nonisothermal crystallization behaviors of the composites. The analyses demonstrated that the F(T) value estimated from the Mo model decreased when the GO content was increased. This result implied that GO promoted the nonisothermal crystallization of PESu in the ternary PESu/PEG/GO composites. Discussions on nucleation activity and microscopy observations confirmed that GO can act as a nucleation agent to further enhance the crystallization of the composites. The significant nucleation effect of GO on PESu in its novel ternary composite was first discovered in this study.

Grafting of Biodegradable Polyesters on Cellulose for Biocomposites: Characterization and Biodegradation

Sustainable, biodegradable and thermoplastic processable aliphatic polyesters (polybutylene succinate (PBS) and polyethylene succinate (PES)) were prepared and characterized; then, they were grafted onto cellulose micro-fibers using a simple click reaction. This modification was conducted under simple experimental conditions. The characterization (NMR and FTIR analysis), thermal properties, solubility, morphology and biodegradation process of the all products prepared were established and studied. The results show that the solubility of the prepared derivatives is improved in comparison with cellulose, while their thermal stability showed a slight decrease compared to the starting materials. The composites derived from the modified cellulose show a slight decrease in their biodegradability in comparison with that of unmodified cellulose due to several parameters.

Incorporation of inorganic fullerene-like WS2 into poly(ethylene succinate) to prepare novel biodegradable nanocomposites: a study on isothermal and dynamic crystallization

Novel biodegradable nanocomposites based on PES and environmentally-friendly IF-WS₂ were prepared with enhanced crystallization behavior in isothermal and non-isothermal modes.

Kinetics of dispersion of nanoparticles in thin polymer films at high temperature

We report the first detailed study of the kinetics of dispersion of nanoparticles in thin polymer films using temperature dependent in situ X-ray scattering measurements. We show a comparably enhanced dispersion at higher temperatures for systems which are otherwise phase segregated at room temperature. Detailed analysis of the time dependent X-ray reflectivity and diffuse scattering data allows us to explore the out-of-plane and in-plane mobility of the nanoparticles in the polymer films. While the out-of-plane motion is diffusive with a diffusion coefficient almost two orders of magnitude lower than that expected in bulk polymer, the in-plane one is found to be super-diffusive resulting in significantly larger in-plane displacement at similar time scales. We discuss the origin of the observed highly anisotropic motion of nanoparticles due to their slaved motion with respect to the anisotropic chain orientation and consequent diffusivity anisotropy of matrix chains. We also suggest strategies to utilize these observations to kinetically improve dispersion in otherwise thermodynamically segregated polymer nanocomposite films.

Combinatorial effect of rolling and carbonaceous nanoparticles on the evolution of crystallographic texture and structural properties of ultra high molecular weight polyethylene

Presence and shape of nanoparticles influences the crystallographic texture of ultra high molecular weight polyethylene during hot rolling.