STUDIES ON IPE OF POLYACRYLAMIDE INVERSE EMULSION AND MODIFIDE UREA-FORMALDEHYDE RESIN

The selective water plugging agent was prepared by heating the blends of the polyacry-lamide inverse latex, modified urea formaldehyde resin, crosslinking agent and catalysts.The results show that using different types of polymers and additives or changing in theirproportion of the blends, the gelling viscosity, starting point of gelling and other propertiesof the IPN can be controlled.

Short Communication—A Novel Sample Preparation Method That Enables Ultrathin Sectioning of Urea-Formaldehyde Resin for Imaging by Transmission Electron Microscopy

Urea-formaldehyde (UF) resin is widely used as an adhesive for the manufacture of a range of wood and fiber based products. Although the microstructure of this resin has been examined at high resolution by field-emission scanning electron microscopy and atomic force microscopy, transmission electron microscopy (TEM) has thus far not been used, perhaps because of difficulties in ultrathin sectioning this resin in cured (polymerized) state. In the technical note presented here, a novel sample preparation method is described which enabled us to examine the microstructural morphology of UF resin by transmission electron microscopy in ultrathin sections, revealing the presence of spherical particles within the resin. Our initial attempt to ultrathin section the resin directly was not successful as it was too brittle to trim blocks for sectioning. Then, we developed a sample preparation technique that involved impregnation ofPinus radiatawood tissues with the UF resin, and then embedding of resin impregnated wood tissues with Spurr’s low viscosity embedding medium, which has been widely employed in plant and wood ultrastructure work. The TEM images illustrated and the information on the microstructural morphology of the UF resin presented are based on this novel sample preparation approach.

Preparation and characterization of urea-formaldehyde resin]reactive kaolinite composites

Novel urea-formaldehyde resin/reactive kaolinite composites containing 20-40wt%; kaolinite were prepared by in situ polymerization. The kaolinite was modified with tetraethoxysilane and a silane coupling agent to introduce reactive groups. Fourier-transform infrared spectroscopy and X-ray diffraction confirmed preparation of the urea-formaldehyde resin/reactive kaolinite composites. The composite morphology was investigated using scanning electron microscopy; the composites consisted of uni- form spherical particles. The surface chemical components of the composites were determined using energy-dispersive X-ray spectroscopy. The spectra showed that the reactive kaolinite was encapsulated by the urea-formaldehyde resin. The thermal properties of the composites were examined using dif- ferential scanning calorimetry and thermogravimetric analysis. The results showed that their thermal stability was much better than that of pure urea-formaldehyde resin, Reactive kaolinite addition greatly decreased formaldehyde emissions and improved the water resistance of the composites. A mechanism for urea-formaldehyde resin/reactive kaolinite composite synthesis is proposed.

Electroless plating of copper layer on surfaces of urea-formaldehyde microcapsule particles containing paraffin for low infrared emissivity

A copper coating was deposited by electroless plating on the surfaces of urea-formaldehyde microcap- sules containing paraffin （UFP） particles. This composite microcapsule structure had low infrared OR） emissivity and maintained a constant temperature, and could be used in IR stealth applications. The eiectroless copper layer formation and its micro-appearance, and the effect of the copper layer on the IR emissivity and thermal properties of the composite microcapsules were investigated. The IR emissivity of the composite microcapsules at wavelengths of 1-14 μm gradually decreased with increasing copper mass on the surface. After formation of an integrated copper layer, the rate of IR emissivity decrease was lower. This is because the copper coating improves the surface conductivity of the UFP; a high conductivity results in high reflectivity, which leads to a decrease in IR emissivity. The lowest IR emissivity achieved was 0.68. The phase-change enthalpy of the composite microcapsules decreased with increasing amount of copper coated on the surface because of the high density of copper. When the mass increase of the UFP after electroless copper plating was about 300%, the composite microcapsules had low IR emissivity （about 0.8） and a high phase-change enthalpy （80J/g）.

Preparation and Characterization of Microcapsules for Self-healing Materials

The urea-formaldehyde（UF） capsules filled with a healing agent, a mixture of epoxy resins（epoxy 711 and E-51） as core material, were produced by means of one step in-situ polymerization. The characteristics of these microcapsules were studied via scanning electron microscopy（SEM）, particle size analysis, FTIR and DSC/TGA. The results show that the dispersed and integrated microcapsules of 5 μm in shell thickness were synthesized successfully. The capsules were produced with diameters ranging from 10 to 250 μm via controlling agitation rate. Young＇s modulus of the capsule was a little lower than those of the epoxy resins, but the microcapsules having such a shell thickness were robust enough to survive handling during manufacturing self-healing composites. When damage occurred in the epoxy matrix, the crack could rupture the microcapsule to make the repairing agent release.

New Advanced Technology on Waste Resourcelization of the Black Pulping Liquor

Combining the characteristics of the black pulping liquor that contains a lot of lignin and other biomass resources, the technology of comprehensive waste utilization is employed. The reconstructive preparation of modified urea-formaldehyde glue by adding black pulping liquor and the application in extruding the medium density fibre board using this modified urea-formaldehyde glue is researched. Results show that when applying the preparation technology that alkaline reaction and then weak acid reaction, the appropriate preparation process is as follows： the adding urea process is divided into three stages （proportion 2 ： 1 ： 1） ; the pH value is 8.0, and the reaction time is 40 min in the addition reaction stage; the pH value will be naturally reduced to 3.5 -5.0, and the reaction time is 45 min in the aggregation reaction stage; the pH value is 8.0 in the urea complement stage. And the optimal condition of the reconstructive preparation the modified ureaformaldehyde glue is adding the condensed black pulping liquor after hydroxymethylation in the beginning of polycondensation reaction by 5% proportion. The application in extruding medium density fibre board with this modified urea-fosmaldehyde glue is proved feasible.

Nitrogen Release from Slow-Release Fertilizers in Soils with Different Microbial Activities

Soil microbial activity is recognized as an important factor affecting nitrogen (N) release from slow-release fertilizers. However,studies on the effect of size and activity of soil microflora on fertilizer degradation have provided contrasting results. To date, no clear relationships exist between soil microbial activity and the release of N from slow-release fertilizers. Hence, the aim of this study was to better understand such relationships by determining the release of N from three slow-release fertilizers in soils with different microbial activities. Soils were amended with urea-formaldehyde (UF), isobutylidene diurea (IBDU), and crotonylidene diurea (CDU). Urea, a soluble fertilizer, was used as the control. Fertilized soil samples were placed in a leaching system, and the release of N was determined by measuring ammonium-N and nitrate-N concentrations in leachates during 90 d of incubation. Non-linear regression was used to fit N leaching rate to a first-order model. In all the treated soils, N was released in the order: urea (89%–100%) > IBDU (59%–94%) >UF (46%–73%) > CDU (44%–56%). At the end of incubation, N released from CDU did not differ (P > 0.05) among soils. On the contrary, UF and IBDU released significantly lower (P < 0.05) amounts of N in the soil with higher microbial activity and lower pH.The rate constant (K_0) for UF was lower (P < 0.05) in the soil with lower pH. Taken together, our results indicated that soil microbial size and microbial activity had a marginal effect on fertilizer mineralization.

Modeling and optimization of the parameters affecting the in-situ microencapsulation process for producing epoxy-based self-healing anti-corrosion coatings

Micro/nanocapsules of urea-formaldehyde resin loaded with linseed oil, which are a self-healing agent in glass flake epoxy anti-corrosion paint, were prepared using a combination of ultrasonic homogenization and in-situ polymerization. The main objective of this study was to model and optimize the microen- capsulation process. Five-level central composite design was used to design, model, and optimize the microencapsulation process. A quadratic model was constructed to show the dependency of the per- centage of encapsulated linseed oil and capsule size, as model responses, on the studied independent variables （the rotational speed of the agitator and the power and duration of sonication）. Analysis of vari- ance showed that all of the variables have significant effects on the encapsulated linseed oil percentage, while the rotational speed of the agitator and sonication time is effective variables for controlling the capsule size. Under the determined optimum conditions, a maximum encapsulated linseed oil percentage （ELO%） of 93.9% and a minimum micro/nanocapsule size of 0.574 μm were achieved at 594 rpm agitation, 350 W sonication power, and 3 min sonication time. Validation of the model was performed. The percent- age relative errors between the predicted and experimental values of the ELO% and micro/nanocapsule size are 1.28% and 3.66%, respectively. The efficacy of the optimum micro/nanocapsules in healing cracks in a glass flake epoxy paint and corrosion protection was investigated by the salt spray test and Tafel polarization technique.

Effect of Wood-drying Condensate on Emission of Volatile Organic Compounds and Bonding Properties of Fibreboard

Potential use of condensate generated by cooling the steam obtained during high-frequency/vacuum drying step of hardwood lumber was investigated.The liquid condensates were obtained from oak,beech and walnut wood.This liquid condensate was then used as a replacement for deionized water in the synthesis of Urea-Formaldehyde(UF)resin(5 wt%of total resin)using a laboratory scale reactor.Medium Density Fibreboards(MDFs)were produced using control and modified resins.Emissions of Volatile Organic Compounds(VOCs)from the MDFs were determined by Micro Chamber method.The bonding properties of the MDFs were determined according to European standards.The main VOC emissions from MDFs produced using UF resin containing the condensate were a-Pinene,b-Pinene,careen,and acetic acid,which were lower than those of the control MDF,except for the acetic acid emission of MDF with oak condensate.In the tree species,the beech wood condensate gave the lowest VOC emissions(732μg·m^-3)from the MDFs,followed by the MDFs containing walnut wood condensate(852μg·m^-3),oak wood condensate(998μg·m^-3),and control MDF(3529μg·m^-3),respectively.However,the internal bond strength of MDFs containing the condensate was negatively impacted by the condensate(0.70 N·mm^-2 to 0.54 N·mm^-2 depending on the tree species).The results showed that the liquid wood-drying condensate which generally released to the ground could be efficiently used as an alternative to expensive VOCs scavenger used in the production of UF resin bonded MDF.This may be one of the most efficient uses of the condensate in high value-added materials.

Release Profile of Nitrogen During Thermal Treatment of Waste Wood Packaging Materials

Wood packaging waste with a high recycling value is one of the main components of packaging waste.However,most research has been focused on natural wood,and less is known about the recycling of wood-based panel waste commonly used in packaging.This paper examined the pyrolysis of common urea-formaldehyde(UF)resin particleboard,including the decomposition characteristics of its nitrogen-containing adhesives,the product types,and how they are generated.The samples and pyrolysis products were analyzed by infrared spectroscopy.The results showed that the UF resin was the main contributor to the release of ammonia(NH3)and hydrogen cyanide(HCN).At low temperatures,more NH3 was released than the HCN,and at high temperatures,the reverse was true.A high heating rate promoted the release of the NH_(3) and HCN.The UF resin and wood in the particleboard interacted and caused the release of the NH3 and HCN.These results provide a reference for further study of the thermochemical regeneration of wood-based packaging waste.