Hualin Chen

Synthesis and Sand-Fixing Property of Cationic Poly(Vinyl Acetate-Butyl Acrylate-DMC) Copolymer Emulsions

The novel cationic poly(vinyl acetate-butyl acrylate-DMC) copolymer emulsion used as chemical sand-fixing material was successfully prepared. The morphology, structure and composition, and thermal property of the emulsion were characterized by TEM, FTIR and DSC, respectively. The correlations between the concentration of prepared emulsion and the sand-fixing properties were investigated. The results show that the emulsion could significantly improve the water retaining, compressive strength and anti-wind erosion ability to prevent the loose sand surface from forming a sand dune in the wind erosion conditions. Also, the prepared emulsion has good thermal and freeze-thaw stabilities to withstand the changes in temperature.

Chemical sand stabilization: A review of material, mechanism, and problems

Chemical sand stabilization has potential for desertification control and this method is characterized by its speed and convenience in operation compared with other stabilization technologies. The materials used in chemical sand stabilization are the key point of this technology and various materials have been developed and investigated. In this review, we present the classification, performance of the materials adopted in sand stabilization, and their stabilizing mechanism as well. We wish to find the relationship between the material structures and their application performance to prevent blind use. However, the consideration for the materials used in chemical sand stabilization is far behind the requirement of desertification control, thus greater efforts have to be paid in this area.

Preparation and Characterization of PDMS-PMMA Interpenetrating Polymer Networks with Indistinct Phase Separation

This paper describes the preparation and characterization of the interpenetrating polymer networks (IPNs) of polydimethylsiloxane-polymethyl methacrylate (PDMS-PMMA) via 3-(methacryloxypropyl)-trimethoxy-silane (MPS) as the crosslinking agent. The structure of synthesized IPNs was characterized by 1HNMR, DSC, FT-IR, XPS, SEM and AFM, respectively. The experimental results show that, with the method adopted in this preparation process, the phase separation between PDMS and PMMA in PDMS-PMMA IPNs has been reduced to a smaller extent than other previous reports.

Scale inhibitors with a hyper-branched structure: preparation, characterization and scale inhibition mechanism

In order to improve the scale inhibition efficiency of existing scale inhibitors for industrial water and to reduce the phosphorus pollution of water bodies, a new type of scale inhibitor with a hyper-branched structure has been developed in this study. First, an AB′ type of functional monomer (AMA) was synthesized from maleic anhydride (MAH) and propylene glycol, then copolymerized with monomer B (MAH) through radical polymerization, resulting in a hyper-branched polycarboxylic acid. The synthesis conditions, such as reaction temperature and time, monomer ratio and initiator dosage, have been investigated for obtaining the expected hyper-branched polymer with good scale inhibition performance. The scale inhibition efficiency of the obtained products was determined according to their resistance to the crystallization of calcium sulfate and calcium carbonate under the optimal application conditions. The experimental results show that the hyper-branched polycarboxylic acid provides a scale inhibiting efficiency for CaCO3 and CaSO4 as high as 95.2% and 92.3%, respectively. In addition, XRD analysis showed that the good scale inhibition of the hyper-branched polycarboxylic acid is attributed to its ability to inhibit and destroy the formation of crystals, changing the crystal forms of the calcium scale. This conclusion indicates that the prepared hyper-branched polycarboxylic acid has great application potential in the treatment of industrial water.

The Influence of 2-Hydroxyethyl Acrylate on the Properties of Cationic Poly(VAc-BA-HEA) Terpolymer Latexes

The cationic poly(vinyl acetate-butyl acrylate-2-hydroxyethyl acrylate) terpolymer latexes (Poly(VAc-BA-HEA)) were successfully prepared using the emulsion polymerization. The structure and composition, morphology, and thermal property of the latexes were characterized by FTIR, TEM and DSC, respectively. Also, the correlations between the particle size, zeta potential, viscosity and water absorption of prepared cationic latexes and 2-hydroxyethyl acrylate concentration were established. The results show that the concentration of 2-hydroxyethyl acrylate could affect the properties of the latexes significantly. This offers an attractive opportunity for adjusting the particle size and viscosity of latexes over a wide range by feeding 2-hydroxyethyl acrylate with varying concentration.

Influence of 2-Methylacryloylxyethyl Trimethyl Ammonium Chloride on the Properties of Cationic Poly(vinyl acetate-butyl acrylate-DMC) Copolymer Emulsions

The cationic poly(vinyl acetate-butyl acrylate-DMC) copolymer emulsions were successfully prepared using the emulsion polymerization technique with 2-methylacryloylxyethyl trimethyl ammonium chloride (DMC) as a functional cationic monomer, cetyltrimethylammonium bromide (CTAB) as the surfactant, and K2S2O8 as the initiator. The morphology, structure and composition, and thermal properties of the emulsions were characterized by TEM, FTIR and DSC, respectively. Also, the correlations between the particle size, zeta potential, viscosity, water absorption and antibacterial efficiency of prepared cationic emulsions and DMC cationic monomer content were established. The results show that the content of the DMC monomer could affect the properties of the emulsions and their films significantly. This offers an attractive opportunity for adjusting the particle size and zeta potential of cationic emulsions over a wide range by feeding DMC monomer in varying concentrations. Furthermore, the prepared emulsions present a high antibacterial efficiency of 98.2% even containing only 2.0 wt% DMC in its monomers, which results in a great potential application as a kind of antibacterial coating material in the future.

Migration behavior of anionic polyurethane dispersion during infiltration and redistribution in sand

Migration behavior strongly affects the properties of the chemical sand stabilization (CSS) crust by determining the distribution of the stabilizing material in sand. A simple method was established to investigate the migration behavior of anionic polyurethane (APU) dispersion (APUD) in sand, based on weight measurement. The movements of APU particles and water were found to differentiate during the redistribution, as a result of the size restriction of film water. By analyzing the interaction between the sand surface, APU particles, and water, four patterns of the migration of APU particles were illustrated. Factors that might affect the migration, such as temperature, APU particle size, and concentration of APUD, were investigated. A semi-empirical formula was deduced for the thickness of the CSS crust, which demonstrates the relationship among sand, water, and the stabilizing material.

Properties of surfactants on high salt-affected sandy land in enhanced sand fixation: salt tolerance, adsorption isotherms and ecological effect

In the present paper surfactant, for the first time, was used to improve the sand fixing ability of emulsion in high salt-affected sandy land. This study started from the analysis of the main components of sand particles from Golmud sandy land, Qinghai province, China, by X-ray diffraction (XRD). Then, two surfactants, sodium dodecyl sulfate (SDS, an anionic surfactant) and Pluronic L35 (L35, a nonionic surfactant), were selected and used to conduct a salt tolerance test before their reaction with sand from a salty desert. The water solubilization method and Fourier transform infrared (FTIR) spectroscopy have been adopted to investigate the salt tolerance of surfactants and their reaction with sand particles, respectively. The adsorption and adsorption characteristics of two surfactants at varied salinities by sand particles have been considered because of its significance for the interaction. In addition, the influence of SDS and L35 on the growth of Escherichia coli (E. coli) and sand microbes were evaluated to understand their ecological effect. The experimental results showed that SDS and L35 can visibly enhance the sand-fixing ability of the emulsion in high salt-affected sandy land. The related mechanism is that, first, SDS and L35 could improve the stability of the emulsion against the salt if the preparation of emulsion uses SDS and L35 as the emulsifying agents; second, SDS and L35 could change the morphology of salt in sand (this experimental result we will report in another paper). The investigation into the influence of SDS and L35 on the growth of E. coli and sand microbes also showed a dependable ecological effect.

The Surface Characteristics of Chitosan Modified PSt-GMA Microspheres Influenced the Interactions and Properties of Immobilized Pepsin

The surface characteristics of carriers outstandingly influence the application of immobilized enzymes. Because of its biocompatible and multi-functional groups, chitosan was introduced into poly(styrene-co-glycidyl methacrylate) (PSt-GMA) microspheres with/without spacer-arms. Pepsin was immobilized onto these microspheres by a simple and mild process, and then its enzymatic activity was evaluated. As for the different modified microspheres, the interactions between the carrier and enzyme molecules would be different, influencing the immobilized system. The experimental results suggested that the optimal pH for immobilized enzyme was close to the optimal reaction pH of free enzyme. It was also found that the Freundlich model fit the immobilized process better than the Langmuir model. In addition, pepsin immobilized onto chitosan modified microspheres (CMM, M3-M4) possessed a higher affinity to substrate, hemoglobin. Compared to free pepsin, the optimal reaction temperature of immobilized pepsin onto modified microspheres (M2-M4) shifted toward higher temperature. Furthermore, the thermal and storage stabilities of pepsin after immobilization were enhanced, particularly for pepsin immobilizing onto CMMs. The pepsin linked onto M3/M4 still retained approximately 70% of enzymatic activity after storing 50 days, compared to below 20% for free pepsin. In a word, CMMs provide more interactions and biocompatible surface for immobilized enzymes.

The synthesis of salt-resistant emulsion and its application in ecological sand-fixing of high salt-affected sandy land

ABSTRACT For the first time, the salt-resistant emulsion was applied as an ecological sand-fixing material to enhance the sand-fixing ability in salty desert. This study started from the synthesis of the novel salt-resistant poly(vinyl acetate-dibutyl maleate-acyclic acid-sodium p-styrene sulphonate) copolymer emulsion. Then, the structure, composition and thermal property of the emulsion were characterised. The sand-fixing properties and ecological effect of the emulsion were evaluated. The experimental results showed that the emulsion has been successful synthesised and could be used as an ecological sand-fixing material. The related reason is that, first, the emulsion could significantly visibly enhance the sand-fixing ability in high salt-affected sand land. Second, the prepared emulsion had good thermal aging resistance and freeze-thaw stabilities to withstand the changes in the temperature of salty desert, and the test of the influence of the emulsion on the growth of microbe of sand showed a favourable ecological effect.