Lignin-containing polyurethane elastomers with enhanced mechanical properties via hydrogen bond interactions.

In this work, lignin-containing polyester polyol (LPES) was successfully synthesized by vacuum melting method with lignin instead of polyol, and then reacted with isocyanate and chain extender to obtain lignin-based polyurethane elastomer (LPUE). The effects of lignin as reactive raw material, chain extender, and filler on the structure, thermostability, mechanical performance, and self-healing properties of elastomers were systematically studied, respectively. The comprehensive mechanical properties of the obtained materials were significantly enhanced after the introduction of lignin, especially the maximum tensile strength increased to 26.6 MPa and elongation at break reached 408.6%, which were 1510.3% and 2130.5% higher than that of the original polyurethane elastomer (PUE). Results revealed that lignin in the hard segment had a significant effect on the thermal stability and mechanical properties of polyurethane elastomer, and lignin in the soft segment had an obvious impact on the healing properties. Due to the hydrogen bonding interaction of the polar groups in the molecular chain of lignin to form a microphase-ordered structure, LPUE with excellent mechanical properties can be obtained.

Evaluation of Real-Time PPP-Based Tide Measurement Using IGS Real-Time Service.

Tide data plays a key role in many marine scientific research fields such as seafloor topography measurement and navigation safety. To obtain reliable tide data, various methods have been proposed, e.g., tide station measurement, satellite altimeter measurement, and differential global positioning system (GPS) buoy measurement. However, these methods suffer from the limitation that continuous observations at different areas might not be always available. In order to provide high-precision as well as continuous real-time tide data, we propose a method based on real-time precise point positioning (RT-PPP) by using International GNSS Service (IGS) real-time service (RTS) products. Firstly, compared with the IGS final products, the accuracy of the RTS satellite orbit and clock is evaluated. Secondly, the positioning performance of RT-PPP is compared with the IGS ultra-fast products. Finally, a robust Vondrak filter is proposed to eliminate the influence of high-frequency noise and errors and to obtain tide results. Experimental results show that three-dimensional (3D) accuracy of the RTS orbit is better than 0.05 m, and also has 0.22 ns less clock bias. An improvement of 60% is achieved for positioning accuracy using RTS products compared to IGS ultra-fast products. Compared with the post-processing PPP method, the double difference (DD) method and tide gauge data, the root mean square (RMS) values of RT-PPP tide are 0.090, 0.194 and 0.167 m, respectively.

The effects of rubber nanoparticles with different polarities on thermal properties and foaming performance of polypropylene blends.

Polypropylene blends with both polybutadiene rubber (PB) and polycarboxylbuturonile rubber (xNBR) and the required amount of acrylamide (AM) was prepared by blending with water, and the crystallinity, rheological behaviour and thermal performance were analysed and compared. The results of DSC and XRD characterization showed an obvious enhancement in the crystallization of the PP matrix in PP/xNBR/AM blends compared to PP/PB/AM blends, due to the strong incompatibility between xNBR nanoparticles and the PP polymer matrix leading to the inhibition of segmental mobility and induced formation of heterogeneous nuclei. Rheological analysis showed that the dynamical mobility of polymer chains was retarded while the AM monomer was incorporated, due to strengthening interfacial interactions by grafts through hydrogen bonding. The foaming performance was clearly improved, as reflected in the uniform cell morphology and higher cell density, and the expansion ratio achieved was 13-fold. In addition, the decomposition temperature increased from 403 °C to 465 °C by nearly 62 °C as compared with neat PP, which is ascribed to the inhibition of segmental mobility due to the cyclization reaction of nitriles. The increase in the surface energy was about 2.2-fold, which resulted in a decrease of the water contact angle from 105.3° to 83.7°, attributed due to AM addition to the composition.

Synergistic lignin construction of a long-chain branched polypropylene and its properties.

In light of current environmental pressures (referring to its destruction) and the consumption of petrochemical resources, the substitution of chemicals products with renewable natural substances has attracted extensive interest. In this paper, a synergistically constructed lignin polypropylene matrix composite with long-chain branched characteristics was prepared by a pre-irradiation and melt blending method. The effects of lignin on the crystallization, rheological behavior, foaming and aging properties of polypropylene were studied. Differential scanning calorimetry and polarized light microscopy results show that lignin undergoes heterophasic nucleation in a polypropylene matrix; rheological studies show that lignin promotes the formation of a heterogeneous polypropylene network, and thus polypropylene exhibits long-chain branching features; nucleation and a network structure endow the polypropylene-based composites with uniform cell size, thin cell walls, and a foaming ratio of 5-44 times; at the same time, a large number of hindered phenols in lignin can capture free radicals to improve the aging properties of the polypropylene. This research will help to convert industrial waste into functional composite materials.

Green Modification of Corn Stalk Lignin and Preparation of Environmentally Friendly Lignin-Based Wood Adhesive.

In this study, corn stalk lignin was used to react with non-volatile and non-toxic glyoxal under the catalysis of a sodium hydroxide solution, and a wood adhesive based on glyoxalated corn stalk lignin was prepared. The effect of the hydroxylation reaction on the structure and properties of lignin were studied using Fourier transform infrared spectroscopy (FTIR), ultraviolet spectrophotometry (UV), thermogravimetric analysis (TGA), titration tests, gel permeation chromatography (GPC), and differential scanning calorimetry (DSC). Compared with unmodified lignin, the glyoxalated corn stalk lignin had a significant improvement in hydroxyl content, activation, and thermal stability. At the same time, results from the GPC showed that the molecular weight increased compared with original corn stalk, possibly due to the secondary polycondensation reaction between lignin and glyoxal. Lignin-based environmental wood adhesives were prepared by mixing modified lignin and epichlorohydrin (ECH), and the dry strength of plywood reached 1.58 MPa. The mechanical strength and water resistance of plywood was improved significantly by mixing some aqueous emulsion into lignin-based adhesives, e.g., polyacrylic ester (AE) emulsion and aqueous polyurethane (PU) emulsion.

Flexible anode materials for lithium-ion batteries derived from waste biomass-based carbon nanofibers: I. Effect of carbonization temperature.

Carbon nanofibers (CNFs) with excellent electrochemical performance represent a novel class of carbon nanostructures for boosting electrochemical applications, especially sustainable electrochemical energy conversion and storage applications. This work builds on an earlier study where the CNFs were prepared from a waste biomass (walnut shells) using a relatively simple procedure of liquefying the biomass, and electrospinning and carbonizing the fibrils. We further improved the mass ratio of the liquefying process and investigated the effects of the high temperature carbonization process at 1000, 1500 and 2000 °C, and comprehensively characterized the morphology, structural properties, and specific surface area of walnut shell-derived CNFs; and their electrochemical performance was also investigated as electrode materials in Li-ion batteries. Results demonstrated that the CNF anode obtained at 1000 °C exhibits a high specific capacity up to 271.7 mA h g-1 at 30 mA g-1, good rate capacity (131.3 and 102.2 mA h g-1 at 1 A g-1 and 2 A g-1, respectively), and excellent cycling performance (above 200 mA h g-1 specific capacity without any capacity decay after 200 cycles at 100 mA g-1). The present work demonstrates the great potential for converting low-cost biomass to high-value carbon materials for applications in energy storage.