Liying Qian

Enhanced water vapour barrier and grease resistance of paper bilayer-coated with chitosan and beeswax.

In order to overcome the deficiencies of single layer coating, bilayer coated papers were prepared by two separate coating procedures using various combinations of proteins or polysaccharides with beeswax. Among those combinations, chitosan-beeswax bilayer coated paper showed the best water vapour barrier property. It was observed that as the concentration of chitosan solution increased from 1.0 to 3.0 wt%, its water vapour transport rate (WVTR) decreased from 171.6 to 52.8 g/m(2)/d but using reduced beeswax coating weight (from 10.1 to 4.9 g/m(2)). It also displayed an enhanced performance of grease resistance. Scanning electron microscopy (SEM) showed that beeswax layer was fitted to chitosan layer so closely that these two layers are indistinguishable. Confocal laser scanning microscope (CLSM) further confirmed the existence of an integrated chitosan film between beeswax layer and paper base and a thin composite layer consisting of chitosan and beeswax.

Immobilization of pectinase on oxidized pulp fiber and its application in whitewater treatment.

Modified pulp fiber was originally used as a new type of carrier for pectinase immobilization. Pulp fiber was oxidized by sodium periodate to produce aldehyde groups for covalently binding with amino groups of pectinase. Results showed that the enzymatic activity of immobilized pectinase on pulp fiber reached 65 μgg(-1)min(-1) when immobilization pH value, temperature and time were of 7.0, 20 °C and 15 min, respectively. The immobilized pectinase showed higher thermo stability in a wider temperature range of 40-70 °C than its free type and its optimal pH shifted from 8.0 to 8.8. Furthermore, the immobilized pectinase exhibited good operational stability. When employed in whitewater treatment of papermaking industry, it still efficiently decreased the cationic demand after operating repeatedly for six batches. The results obtained demonstrate a promising route to prepare available, cheap and biodegradable carrier for immobilizing enzymes with potential application in wastewater treatment in papermaking industry.

Polyelectrolyte complex containing antimicrobial guanidine-based polymer and its adsorption on cellulose fibers

Abstract Polyelectrolyte (PE) complexes (PECs) are formed by the electronic interaction between cationic and anionic PEs, and a number of factors influence the forming pattern and characteristic of the PECs. In this work, a guanidine-based polymer with high cationic charge density (CD) and low molecular weight (MW) was applied for interacting with anionic carboxymethylcellulose (CMC) with low CD and high MW. To reveal the self-assembly pattern of the PEC, the turbidity of PEC and layer-by-layer (LBL) film, along with its adsorption on cellulose fibers, was characterized. The antimicrobial activity of the handsheet containing the PEC was also investigated. The charge ratio of anionic PE to cationic PE was found to be critical to the PEC stability. The roughness of the LBL film was increased and then decreased with more bilayers assembled. The isothermal adsorption indicated that the amount of adsorbed cationic PE on cellulose fibers was increased significantly by interacting with anionic CMC. The inhibition of the cationic PE on bacterial growth was not impaired by the formation of the complex. The CMC with high MW in the complex could maintain or even improve the antimicrobial efficiency of the guanidine-based polymer in handsheet.

Preparation of Novel Nano-Sized Hydrogel Microcapsules via Layer-By-Layer Assembly as Delivery Vehicles for Drugs onto Hygiene Paper

Hydrogel microcapsules are improved transplantation delivery vehicles for pharmaceuticals by effectively segregating the active ingredients from the surroundings and delivering them to a certain target site. Layer-by-layer (LbL) assembly is an attractive process to fabricate the nano-sized hydrogel microcapsules. In this study, nano-sized hydrogel microcapsules were prepared through LbL assembly using calcium carbonate nanoparticles (CaCO3 NPs) as the sacrificial inorganic template, sodium alginate (SA) and polyethyleneimine (PEI) as the shell materials. Ciprofloxacin was used to study the encapsulation and release properties of the hydrogel microcapsules. The hydrogel microcapsules were further adsorbed onto the paper to render antimicrobial properties. The results showed that the mean size of the CaCO3 template was reduced after dispersing into sodium n-dodecyl sulfate (SDS) solution under sonication. Transmission electron microscope (TEM) and atomic force microscope (AFM) revealed that some hydrogel microcapsules had a diameter under 200 nm, typical creases and collapses were found on the surface. The nano-sized PEI/SA hydrogel microcapsules showed high loading capacity of ciprofloxacin and a sustained release. PEI/SA hydrogel microcapsules rendered good antimicrobial properties onto the paper by the adsorption of hydrogel microcapsules, however, the mechanical properties of the hygiene paper were decreased.

Preparation of conductive composite hydrogels from carboxymethyl cellulose and polyaniline with a nontoxic crosslinking agent

Conductive composite hydrogels based on sodium carboxymethyl cellulose (CMC) and polyaniline (PAn) were prepared via the semi-interpenetrating polymer network (semi-IPN) method, using glycerol diglycidyl ether (GDE) as the crosslinking agent. The structures of the resulting composite hydrogels were characterized by 13C-NMR, FT-IR, and SEM. The composite hydrogels with various concentrations of CMC presented a similar swelling kinetic behaviour and a relatively high swelling ratio. With increasing CMC concentration, both the compressive fracture stress and modulus of the composite hydrogels improved gradually. Though the modulus of the composite hydrogels increased with more GDE added, the compressive fracture stress decreased when the crosslinking density was too high. The electrical conductivity of the composite hydrogels increased first and then decreased slightly with increasing dosages of CMC and GDE. Doping with aromatic sulfonate is a good approach to improve the conductivity of the composite hydrogels and the conductivity reached 6.31 × 10−3 S cm−1 after doping with sodium benzene sulfonate (BSNa).

Microwave Assisted Preparation of Antimicrobial Chitosan with Guanidine Oligomers and Its Application in Hygiene Paper Products

Guanidinylated chitosan (GCS) was prepared by grafting guanidine oligomers onto chitosan under microwave irradiation. The structure of GCS characterized by FT-IR and 1H NMR verified the covalent bonding between the guanidine oligomers and chitosan; the effects of molar ratio, reaction temperature, and time were investigated and the degree of substitution of GCS reached a maximum of 25.5% under optimized conditions in this work. The resulting GCS showed significantly enhanced antimicrobial activities. The results obtained from the dynamic UV absorption of Escherichia coli (E. coli) and atomic force microscopy (AFM) revealed that the deactivation of E. coli by GCS was due to the destructing of the cell membrane and the prompt release of cytoplasm from the bacterial cells. The adsorption of GCS onto cellulose fibers and the antimicrobial efficiency of the hygiene papers with GCS were also investigated. Microwave irradiation as a green assisted method was applied to promote this reaction. This facile approach allowed chitosan to be guanidinylated without tedious preparation procedures and thus broadened its application as a biocompatible antimicrobial agent.