Shi Feng Zhang

Release of Aspirin from Biodegradable Polyesterurethane Networks

In this paper, the release of model drug aspirin (ASP) from biodegradable polyesterurethane networks was studied. Poly(D,L-lactide-co-glycolide)urethane (PULG) networks were prepared from hydroxyl telechelic star-shaped oligo(D,L-lactide-co-glycolide) coupled with 1,6-diisocyanate-2,2,4-trimethylhexane and 1,6-diisocyanate-2,4,4-trimethylhexane or isophorone diisocyanate. PULG networks turned from transparent to opaque after ASP loading. PULG networks with lower crosslinking density always resulted in higher drug loaded content. The results of differential scanning calorimetry (DSC) and scanning electron microscope (SEM) measurements demonstrated that ASP was uniformly distributed in the networks. The drug release courses of ASP from PULG networks in phosphate buffered saline pH = 7.0 at 37 °C could be divided into three stages. Firstly, ASP release was at approximately uniform rate from PULG networks; Secondly, the release rate obviously increased for the degradation of the PULG networks; Thirdly, the release rate decreased gradually because most of the ASP had diffused out of the PULG networks. The crosslinking density of polyesterurethane networks also affected drug release rate. The in vitro release test revealed that ASP accelerated the degradation process of PULG, which exhibited a typical erosion-controlled release mechanism.

Investigation of Soybean/PF Resin Based Adhesive Applying on Plywood

For developing high bonding strength and environmental-friendly wood composites, a soybean/PF resin based (SP) adhesive was investigated and applied in the manufacture of plywood. Formula of the adhesive, the thermal behavior of the adhesive, and the optimum technical parameters of the plywood manufacture were investigated. The bonding strength and formaldehyde emission of plywood bonding by the adhesive were tested according to Chinese Standards methods. The result shows: the optimum formula of SP adhesive was: soy-based adhesive was 70%, PF resin was 30%; the optimum technical parameters of the plywood manufacture were: hot-pressing temperature was 160 °C, hot-pressing time was 80 s/mm, pressure intensity was 1.2 MPa, and glue content was 160 g /m2; Properties of plywood made under the optimum technical parameters were: the bonding strength was 1.30 MPa, the formaldehyde emission was 0.32 mg/L. It completely meets the type Ⅰ plywood requirement and level E0 of formaldehyde emission.

Effect of Melamine Content in MUF Resin on the Durable Properties of Plywood

The effect of melamine content in melamine modified urea formaldehyde (MUF) resin on durable properties of plywood was investigated using ammonium chloride (NH4Cl) with different melamine/urea (M/U) ratios. The plywood specimens were exposed to laboratory accelerated aging and/or cyclic soak-dry (SD). The experiment results indicated that the melamine contents in MUF resin showed an unobservable effect on the durable properties of MUF resin bonded plywood. The mechanical properties of plywood decreased more severely after accelerated aging test in acidic condition. However, the influence of different curing catalyst contents on mechanical properties and formaldehyde emission of UF resin can be minimized by adding melamine to the resin.

A Novel Formaldehyde-Free Adhesive from Jatropha Curcas Press-cake

Jatropha curcas (Jc) was the most favored biomass plant for bio-diesel production. Jc cakes obtained after oil pressed, rich in protein content, were excellent materials for preparing formaldehyde-free wood adhesives, which could provide alternative to formaldehyde-based resins. Sodium hydroxide, used as denaturing agent, modified protein contained in Jc cakes to prepare wood adhesives. Jc adhesives prepared in different pH value and plywood bonded by them were prepared. The curing behavior of these adhesives was conducted by differential scanning calorimetry (DSC) measurement. The gel content and water absorption of the cured Jc adhesives were measured to evaluate their curing content and the water resistant of plywood bonded with these adhesives was also studied. The results showed that pH value influenced the bonding strength of adhesive significantly. The bonding strength of plywood made by modified Jc adhesive significantly increased comparing with that of unmodified one. The curing peak temperature decreased obviously after modified, which was beneficial to achieve complete curing reaction. Modified Jc adhesives provided a potential way to utilize by-product of energy plant, avoided formaldehyde pollution, and reduced dependence on fossil resources.

Study on Properties of Modified Low Molar Ratio Urea-Formaldehyde Resins (I)

For improving the performance of urea-formaldehyde (UF) resin, modified low molar ratio UF resins were developed to improve water resistance properties and reduce the formaldehyde emission of its bonded products. The effects of modifier feeding amount on the character of the cured resins were characterized by Fourier transform infrared spectroscopy (FTIR) measurement. The viscosity, pH value, solid content, free formaldehyde content, pot time, and curing time of the UF resins were also tested according to Chinese National Standards methods. The results show that the modified 1.00 molar ratio UF resins show lower free formaldehyde content and higher boiling-water-resistance comparing with unmodified ones. The boiling-water-resistant bonding strength of poplar plywood bonded with modified UF resin at 140 °C hot-press temperature can reach type I grade (100 °C water bath 3h) plywood requirement and the formaldehyde emission can meet the E0 grade plywood need.

Preparation and Performance of Bio-Adhesive Based on Acorn Starch Graft Glycidyl Methacrylate

For improving the performance of acorn starch (AS) based bio-adhesive, AS graft glycidyl methacrylate (AS-g-GMA) adhesive was prepared in this paper. The properties of the AS-g-GMA adhesive were studied by Fourier transform infrared spectroscopy (FTIR) and differential scanning calorimetry (DSC) measurement. The bonding strength of the plywood bonded by AS-g-GMA adhesive was measured according to Chinese National Standards methods to evaluate its water resistant. FTIR results indicated that GMA was grafted on the AS successfully. The bonding strength of the plywood bonded by AS-g-GMA adhesive showed lower curing temperature, better bonding strength, and water resistance comparing with that of control. The water resistant could reach type II grade (63°C water bath 3h) plywood requirement when the glycidyl methacrylate adding amount was 6% based on AS.

Study of Amino Polymer Modified Soy Protein Adhesive

For improving the bonding strength and water resistance of plywood bonded with soy protein adhesive (SPA), an amino polymer (AP) was synthesized using polyamines, and the AP was used to modify SPA to prepare a modified soy protein adhesive (MSPA) in this paper. The plywood was prepared using MSPA, and the effects of preparation technology of amino polymer and hot-pressing technology of plywood on the bonding strength of plywood were investigated. The results showed that the optimization preparation technologies of AP were as follow: the molar ratio of polyamine/modifying agents was 0.25/1, the pH value was 5, the reaction temperature was 70 °C, and the reaction time was 1.5 h. The optimization preparation technologies of plywood were that the hot-pressing temperature was 150 °C and the hot-pressing time was 60 s/mm. The bonding strength of plywood made from MSPA on the optimization preparation technology was 1.03 MPa, which meets the requirement of plywood type II (³0.7MPa). The MSPA bonded plywood had a rather low formaldehyde emission, which is close to that of wood itself.

Preparation and Properties of Environmental Friendly Wood Adhesives Based on Wild Acorn Starch

A friendly environmental wood adhesive was prepared using wild acorn starch as a raw material. The physical properties of wild acorn starch were investigated by scanning electron microscope (SEM) and brookfield viscometer. The polyvinyl acetate emulsion and isocyanate were employed to prepared modified wild acorn starch adhesives. The plywoods were prepared using the adhesives and their bonding strength was measured. The experimental results showed that 1) the wild corn starch was adaptive for preparing adhesive; 2)the optimum preparing conditions of the modified wild acorn starch adhesive were as follows: the mass ratio of acorn starch/water/modifing agent was 8/9/3, the addition amount of viscosity reducer was 0.6%, the mass proportion of polyvinyl acetate emulsion/starch adhesive was 1/1, the addition amount of isocyanate was 15% weight of starch adhesive. The plywood using the adhesive prepared at the optimum condition was 0.9 MPa, could meet the type ⅡChinese Strandard plywood requirement.

Properties of Particleboard Manufactured with Modified Urea-Formaldehyde Resin

This study modified urea-formaldehyde (UF) resin with a modifier, and focused on properties of particleboard manufactured with the modified UF resin. The orthogonal design was used to analyze the effects of different levels of hot-pressing temperature, hot-pressing time, glue content, and waterproof agent content on the modulus of rupture (MOR), internal bonding strength (IB), and formaldehyde emission (FE) of the particleboard, and thus determined the optimum technical parameters of hot-pressing. The conclusions were as follows: (1) the modifier used in this study could significantly reduce the free formaldehyde content of UF resin and the formaldehyde emission of particleboard; (2) the optimum hot-pressing technical parameters of particleboard manufactured with the modified UF resin were hot-pressing temperature 180°C, hot-pressing time 50s/mm, glue content 12%, and waterproof agent content 0.6%. The MOR and IB under the optimum technical parameters could reach 20.7 and 0.47 MPa, and the FE was 0.85 mg/L.

Performances of Modified Urea-Formaldehyde Resins for Bonding Plywood

Urea-formaldehyde resin was modified by a modifier with different synthetic processes labelled as UFM1, UFM2, and UFM3 respectively. As a comparison, normal UF resin with a F/U molar ratio of 1.1 labelled as UF0 was synthesized. The thermal behavior of modified urea-formaldehyde resins was studied by TG-DTA techniques, and the properties of plywood bonded with the UFM resins were investigated. The conclusions were as follows: (1) the modifier used in this study could significantly reduce the free formaldehyde content of urea-formaldehyde resin and the formaldehyde emission of plywood; (2) The exothermic peak temperatures of DTA curve were 129.37, 125.05, 120.98, and 116.11 °C for UF0, UFM1, UFM2, and UFM3 respectively. (3) The plywood manufactured with UFM2 and UFM3 resins have high bonding strength (1.28MPa and 1.59MPa) and low formaldehyde emission value (E1 grade).