Jiyou Gu

Preparation and properties of a starch-based wood adhesive with high bonding strength and water resistance.

A Highly efficient method was developed for preparing starch-based wood adhesives with high performance, using H2O2, a silane coupling agent and an olefin monomer as an oxidant, cross-linking agent and comonomer, respectively. The effects of various parameters on the shear adhesive strength were investigated in the dry state (DS) and wet state (WS). The results indicated that the bonding strength of starch-based wood adhesives could reach 7.88 MPa in dry state and 4.09 MPa in wet state. The oxidation could reduce the content of the hydroxyl transforming into carboxyl and aldehyde groups, and the graft copolymerization enhanced the thermal stability, which improved the bonding strength and water resistance. The starch-based adhesive and the fractures in the bonded joints were analyzed via Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM) and thermogravimetric analysis (TGA). The improved properties were attributed to the modified of microstructure of the graft-copolymerized starch-based adhesive.

Synthesis and characterization of maleic anhydride esterified corn starch by the dry method.

Maleic anhydride esterified starch was synthesized by a dry method using corn starch as the material and maleic anhydride as the esterifying agent. The esterified starch (ES) was analyzed by Fourier transform infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS), which confirmed that there was a successful esterification reaction between the maleic anhydride and corn starch. The effects of reaction temperature and time on the degree of substitution of esterified starch were studied, where the results showed that 80 °C of reaction temperature and 3h of reaction time were optimal conditions. The result of XPS testing demonstrated that the esterification reaction led to increase of ester bonds in starch. The scanning electron microscopy (SEM) and laser particle size analyzer results showed that esterification led to roughness on the surface of the starch particle, and the particle size and distribution rate of esterification starch became larger. X-ray diffraction (XRD) analysis demonstrated that esterification reaction did not change the crystalline type of native starch. The differential scanning calorimeter (DSC) and thermo gravimetric analysis (TGA) confirmed that destruction of the crystal structure resulted in improved thermoplasticity of the starch, decreased the gelatinization temperature and increased the thermogravimetric rate of esterification starch.

Effects of dry method esterification of starch on the degradation characteristics of starch/polylactic acid composites

Maleic anhydride esterified corn starch was prepared by dry method. Esterified starch/polylactic acid (PLA) biodegradable composite was produced via melt extrusion method with blending maleic anhydride esterified corn starch and PLA. The influence of the dry method esterification of starch on the degradation characteristics of starch/PLA composites was investigated by the natural aging degradation which was soil burial method. Test results of mass loss rate showed that the first 30 days of degradation was mainly starch degradation, and the degradation rate of esterified starch/PLA (ES/PLA) was slower than that of native starch/PLA (NS/PLA). Therefore, the damage degree of ES/PLA on the surface and inside was smaller than that of NS/PLA, and the infrared absorption peak intensities of C-O, C=O and C-H were stronger than that of NS/PLA. With the increasing time of soil burial degradation, the damage degree of NS/PLA and ES/PLA on the exterior and interior were gradually increased, whereas the infrared absorption peak intensities of C-O, C=O and C-H were gradually decreased. The XRD diffraction peak intensity of PLA in composites showed an increased trend at first which was then followed by a decreased one along with the increasing time of soil burial degradation, indicating that the degradation of amorphous regions of PLA was earlier than its crystalline regions. When the soil burial time was the same, the diffraction peak intensity of PLA in ES/PLA was stronger than that of NS/PLA. If the degradation time was the same, T0, Ti and residual rate of thermal decomposition of NS/PLA were larger than those of ES/PLA. The tensile strength and bending strength of composites were decreased gradually with soil burial time increasing. Both the tensile strength and bending strength of ES/PLA were stronger than those of NS/PLA.

The influence of acid treatment on multi‐walled carbon nanotubes

Purpose – The purpose of this paper is to investigate in detail the effects of acid treatment on multi‐walled carbon nanotubes (MWNTs), which could find a variety of applications in coatings and composites.Design/methodology/approach – A number of analytical techniques, including Fourier transform infrared spectroscopy (FT‐IR), X‐ray photoelectron spectroscopy (XPS), Raman spectroscopy (Raman), and scanning electron microscopy (SEM), were employed to assess the effects of acid treatment on MWNTs.Findings – It was found that desirable modifications to MWNTs occurred after acid treatment. Thus, carboxylic acid groups were introducing on to the surface of MWNTs. It was also found that both chemical and physical properties of MWNTs could be modified/altered.Practical implications – The investigation established a method to modify MWNTs via acid treatment and the effects of such a treatment on MWNTs in detail. The modified MWNTs can be used for various applications and further modifications. The acid treated a...

FTIR and XPS study of the reaction of phenyl isocyanate and cellulose with different moisture contents

Purpose – To evaluate the competing reaction of isocyanate with cellulose and water which can provide direction for further studies on bonding and curing reactions of isocyanate with wood.Design/methodology/approach – Two modern analytical techniques, Fourier transform infra‐red (FTIR) and X‐ray photoelectron spectroscopy (XPS), were used. The FTIR was used to identify the products of the reaction of phenyl isocyanate (PI) with alcohol, water, and cellulose; while the XPS was used to evaluate the proportions of isocyanate that reacted with water or cellulose when PI reacted with cellulose at different moisture contents (MCs), respectively.Findings – Methods for the IR identifications of reaction results of PI with n‐propanol, water, and cellulose, in which the reactions of PI with water and PI with cellulose resulted in N,N′‐diphenylurea and carbamate, respectively, were developed. It was discovered that the extent of reaction of isocyanate and cellulose decreased with increasing cellulose MC, and 92.98 p...

Preparation and characterization of dry method esterified starch/polylactic acid composite materials.

Corn starch and maleic anhydride were synthesized from a maleic anhydride esterified starch by dry method. Fourier transform infrared spectroscopy (FTIR) was used for the qualitative analysis of the esterified starches. The reaction efficiency of dry method esterified starch reached 92.34%. The dry method esterified starch was blended with polylactic acid (PLA), and the mixture was melted and extruded to produce the esterified starch/polylactic acid (ES/PLA) composites. The degree of crystallinity of the ES/PLA was lower than that of the NS/PLA, indicating that the relative dependence between these two components of starch and polylactic acid was enhanced. Scanning electron microscopy (SEM) indicated that the dry method esterified starch increased the two-phase interface compatibility of the composites, thereby improving the tensile strength, bending strength, and elongation at break of the ES/PLA composite. The introduction of a hydrophobic ester bond and increase in interface compatibility led to an increase in ES/PLA water resistance. Melt index determination results showed that starch esterification modification had improved the melt flow properties of starch/PLA composite material. Strain scanning also showed that the compatibility of ES/PLA was increased. While frequency scanning showed that the storage modulus and complex viscosity of ES/PLA was less than that of NS/PLA.

Aqueous poly(vinyl acetate)-based core/shell emulsion: synthesis, morphology, properties and application

Core/shell structured composite emulsions have become an increasingly important interdisciplinary research field and deserve more attention because of their wide and potential applications in modern and advanced materials. The development of reliable synthetic and controlling approaches to composite emulsion with well-designed morphology, composition and functionality is of scientific importance and technological interest. The generation of poly(vinyl acetate)-based core/shell emulsion with phase separation can be achieved through seeded emulsion polymerisation, as well as multi-stage emulsion polymerisation. Insights on the fabrication of poly(vinyl acetate)-based core/shell latex particles with well-defined morphology and architecture have been substantially developed by recent advances in the morphological control mechanism of thermodynamics and kinetics. The factors affecting the formation of poly(vinyl acetate)-based core/shell emulsion, including polymerisation conditions, type and nature of monomer and initiator as well as grafting structure, are discussed. Finally, the properties of the poly(vinyl acetate)-based core/shell emulsion in mechanical, film-forming and adhesive performance, and its applications and potential functionalities are also briefly described.

Reaction kinetics of toluene diisocynate and propanol by in situ FTIR

Purpose – To evaluate the effect of the concentrations of isocyanate group and hydroxyl group and hydroxyl group species on the rate constants of isocyanate‐propanol reaction, and to reveal the kinetics of isocyanate‐hydroxyl reaction.Design/methodology/approach – The in situ FTIR technique was employed to measure the group concentration evolutions, by which the rate constants were determined. Besides, the FTIR was used to detect the OH absorbance shifts during reaction and the OH absorbance at different concentrations. The kinetic mechanism of isocyanate‐propanol reaction was discussed with the combination of rate constants and FTIR spectra.Findings – A new reaction mechanism, alcohol association mechanism, was proposed that could explain many phenomena. It was revealed that the rate constant was independent of the isocyanate concentration, while the concentration and species of hydroxyl groups had apparent effects on the rate constants. It was possible to calculate the number averaged degree of associat...

Exploration of zwitterionic cellulose acetate antifouling ultrafiltration membrane for bovine serum albumin (BSA) separation

This study focused on the preparation of a new kind of membrane material, zwitterionic cellulose acetate (ZCA), via a three-step procedure consist of oxidization, Schiff base and quaternary amination reaction, and the fabrication of antifouling ZCA ultrafiltration membrane by the non-solvent-induced phase separation method (NIPS). The morphologies, surface chemical structures and compositions of the obtained CA and ZCA membranes were thoroughly characterized by field emission scanning electron microscopy (FE-SEM) with energy dispersive X-ray (EDX) spectroscopy, Fourier transform infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS), respectively. Meanwhile, the thermal stability, porosity and average pore size of two investigated membranes were also studied. As a result, the ZCA membrane displayed significantly improved hydrophilicity and water permeability compared with those of the reference CA membrane, despite a slight decrease in the protein rejection ratio. According to the cycle ultrafiltration performance of bovine serum albumin (BSA) solution and protein adsorption experiment, ZCA membrane exhibited better flux recovery property and fouling resistant ability, especially irreversible fouling resistant ability, suggesting superior antifouling performance. This new approach gives polymer-based membrane a long time life and excellent ultrafiltration performance, and seems promising for potential applications in the protein separation.

Fabrication and performance study of a zwitterionic polyimide antifouling ultrafiltration membrane

In this paper, the new aromatic zwitterionic polyimide (PI) copolymer was synthesized by a one-pot polymerization reaction and used to prepare a fouling-resistant ultrafiltration membrane. The obtained polymer was thoroughly characterized by differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA) and exhibited excellent thermal stability. Meanwhile, the zwitterionic PI membrane was compared to the reference PI membrane to determine changes in hydrophilicity, performance and antifouling properties. The results displayed that the surface hydrophilicity, pure water flux and protein solution permeation of the zwitterionic PI membrane were remarkably higher than those of the reference PI membrane. The cycle ultrafiltration experiment for protein solution revealed that nonspecific protein adsorption, especially irreversible protein adsorption, for the zwitterionic PI membrane was significantly reduced, suggesting superior antifouling performance. In sum, the zwitterionic PI is employed as the polymer-based membrane material, resulting in the ultrafiltration membrane with long-term performance stability.