Zhanhua Huang

Enhanced thermal and mechanical properties of PVA composites formed with filamentous nanocellulose fibrils

Long filamentous nanocellulose fibrils (NCFs) were prepared from chemical-thermomechanical pulps (CTMP) using ultrasonication. Their contribution to enhancements in thermal stability and mechanical properties of poly(vinyl alcohol) films were investigated. The unique chemical pretreatment and mechanical effects of CTMP loosen and unfold fibers during the pulping process, which enables further chemical purification and subsequent ultrasound treatment for formation of NCFs. The NCFs exhibited higher crystallinity (72.9%) compared with that of CTMP (61.5%), and had diameters ranging from 50 to 120 nm. A NCF content of 6 wt% was found to yield the best thermal stability, light transmittance, and mechanical properties in the PVA/NCF composites. The composites also exhibited a visible light transmittance of 73.7%, and the tensile strength and Youngs modulus were significantly improved, with values 2.8 and 2.4 times larger, respectively, than that of neat PVA.

Preparation of CMC-modified melamine resin spherical nano-phase change energy storage materials

A novel carboxymethyl cellulose (CMC)-modified melamine-formaldehyde (MF) phase change capsule with excellent encapsulation was prepared by in situ polymerization. Effects of CMC on the properties of the capsules were studied by Fourier transformation infrared spectroscopy (FTIR), differential scanning calorimetry (DSC), scanning electronic microscopy (SEM), X-ray diffractometry (XRD), and thermogravimetric analysis (TGA). The results showed that the CMC-modified capsules had an average diameter of about 50nm and good uniformity. The phase change enthalpy of the capsules was increased and the cracking ratio decreased by incorporating a suitable amount of CMC. The optimum phase change enthalpy of the nanocapsules was 83.46J/g, and their paraffin content was 63.1%. The heat resistance of the capsule shells decreased after CMC modification. In addition, the nanocapsule cracking ratio of the nanocapsules was 11.0%, which is highly attractive for their application as nano phase change materials.

Synthesis and swelling properties of β-cyclodextrin-based superabsorbent resin with network structure

A biodegradable, β-cyclodextrin-based superabsorbent resin was synthesized by the inverse suspension method. The microstructure, chemical structure, and thermal performance of the resin were characterized by scanning electron microscopy, Fourier transform-infrared spectroscopy, and differential scanning calorimetry. The effects of the synthesis conditions (dosage of cross-linking agent, mass ratios of acrylic acid to acrylamide, mass ratios of β-cyclodextrin to total monomer, neutralization degree, initiator dosage, and reaction time) were optimized to achieve a resin with a maximum swelling capacity. The water absorbency of the optimized resin in distilled water was 1544.76 g/g and that in 0.9 wt.% NaCl was 144.52 g/g. The resin, which is thermoplastic as well as pH-sensitive, had good salt resistance and underwent a maximum in swelling with time in CaCl(2) and AlCl(3) solutions. The fracture surface of the dry resin contained many pores. After swelling, the internal hydrogel showed a typical three-dimensional network structure. The biodegradation of the resin reached 71.2% after 18 days treatment at 30 °C with Lentinus edodes.

Preparation and adsorption behaviors of sodium alginate-based adsorbent-immobilized β-cyclodextrin and graphene oxide

Highly water soluble graphene oxide (GO) was synthesized via a modified Hummers method. A sodium alginate (SA)-based adsorbent-immobilized β-cyclodextrin (β-CD) and GO gel (SCGG) with excellent regeneration ability were prepared. The adsorptive properties of methylene blue (MB) on the SCGG adsorbent were studied. The results showed that when the dosage of the adsorbent was 1.0 g, pH of the solution was 7, temperature was 35 °C, initial concentration of MB was 50 mg L−1, and adsorption time was 180 min, the removal rate of MB was 84.98% and the adsorption capacity was 133.24 mg g−1. The isotherms and kinetics of adsorption were investigated to reveal that the equilibrium adsorption and kinetics were well-described by the Freundlich model and pseudo-second-order kinetics, respectively. The thermodynamic parameters showed that the adsorption process was spontaneous and endothermic in nature. The mechanical property of the SCGG was improved by the addition of GO. The regeneration removal rate of MB was more than 82% after six recycles.

One-step hydrothermal synthesis of fluorescent nanocrystalline cellulose/carbon dot hydrogels

Fluorescent nanocrystalline cellulose/carbon dots (NCC/CDs) hydrogels were successfully prepared by a facile one-step green hydrothermal carbonization process. The properties of NCC/CDs hydrogels prepared at different temperatures were investigated by fluorescence spectroscopy, transmission electron microscopy, nuclear magnetic resonance spectroscopy, X-ray diffraction, and thermogravimetric analysis. NCC/CDs hydrogels with high crystallinity, high thermal stability, and excellent fluorescence properties can be obtained by controlling the hydrothermal treatment temperature. Small rod-like NCC/CDs hydrogels with a diameter of 2-6nm, a length of 40-60nm, and the cellulose Ι structure were obtained when the hydrothermal carbonization temperature was 240°C. The NCC/CDs hydrogels exhibited an excellent broad spectral response and high fluorescence stability at various pH values. Considering of the wide natural abundance of NCC and the biocompatibility of the NCC/CDs hydrogels, Preparation in this simple, green approach is attractive for future bio-medical applications.

Separation and purification of Arabinogalactan obtained from Larix gmelinii by macroporous resin adsorption

Arabinogalactan (AG) obtained from Larix gmelinii R. was purified with the method of macroporous resin adsorption. Effects of various parameters on the adsorption, including adsorption time and temperature, the concentration and the dosage of raw AG, the reused numbers of resin, were investigated. The effect of purification was tested through the removal rate of impurity and the contents of AG and impurity. The optimal condition was determined as follows: adsorbed at 30°C for 2 h with the concentration of raw AG <0.1 g·mL−1 and its dosage < 7 mL, the dose of resin was 3 g and reused for 4 times. On the basis of these, macroporous resin column was used for AG purification. The result showed that the AG yield could reach 68.28% with sugar content of 95.02%. The analysis of IR and UV showed that the effect of macroporous resin characteristics on the purification of AG was significant. The obtained product had the same functional groups with standard sample.

Preparation and characterization of spherical β-cyclodextrin/urea–formaldehyde microcapsules modified by nano-titanium oxide

We successfully prepared novel β-cyclodextrin/urea–formaldehyde (β-CD/UF) microcapsules modified by nano-TiO2 using KH560 silane coupling agent by in situ polymerization and grafting method. The as-prepared TiO2–β-CD/UF microcapsules displayed excellent energy storage properties with a melting enthalpy of 154.6 J g−1, and the paraffin content in the TiO2–β-CD/UF microcapsules was as high as 75.94%, indicating a high energy storage capacity. Nano-titanium oxide was successfully reacted onto the surface of the β-CD/UF microcapsules using KH560 by forming new C–O–Si and Ti–O–Si chemical bonds, which was confirmed by FT-IR and XPS technology. Besides, pH played an important role in the encapsulation of phase change paraffin by affecting the curing reaction rate of the shell materials. Also, the thermal decomposition temperature of the TiO2–β-CD/UF microcapsules was highly improved by about 90 °C compared with that of β-CD/UF microcapsules without treatment by TiO2 nanoparticles, mainly due to the formation of C–O–Si and Ti–O–Si chemical bonds. The as-prepared TiO2–β-CD/UF microcapsules in this experiment might be used as an effective and potential media for energy storage.