A new composite two component grout comprised of modified urea-formaldehyde resin and cement was formulated to take account of the advantages and disadvantages of both the cement grout and the chem- ical grout. The ne...A new composite two component grout comprised of modified urea-formaldehyde resin and cement was formulated to take account of the advantages and disadvantages of both the cement grout and the chem- ical grout. The new grout is designed for water blocking by reinforcing as well as seepage control by bore grouting. The A component consists of a modified urea-formaldehyde resin A component, some cement, and some water. The B component is an alkaline coagulant. An orthogonal test of four factors at three lev- els showed that gel time increased with increased water content and with urea-formaldehyde resin con- tent. Gel time decreased at increased levels of alkaline coagulant. The A component of this new composite grout is stable over time. A mixed cross-over test showed that as the volume ratio of A to B increases the gel time falls at first but then increases. The solid strength decreases with increasing levels of the B com- ponent. The solid strength increases over time and becomes stable by the 28th day after mixing. The vis- cosity increases with increasing levels of resin A component. The increase is exponential and may be fit to： μ = 8.162e0.0286x.展开更多
Spherical macroporous adsorbents with active sites capable of hydrogen bonding adsorption based on urea-formaldehyde condensed polymer were synthesized via reversed suspension polymerization. The properties of the obt...Spherical macroporous adsorbents with active sites capable of hydrogen bonding adsorption based on urea-formaldehyde condensed polymer were synthesized via reversed suspension polymerization. The properties of the obtained adsorbent were also investigated in detail. The results showed that the water permeability could be improved by adding hydroxyl-containing organic compound moiety into the adsorbent. The specific surface area and average pore diameter of these adsorbents increased while the porosity first increased then decreased with the increase of the amount of the added hydroxyl-containing compound.展开更多
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 type...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.展开更多
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-emiss...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.展开更多
Lignin,lignosulfonate,and synthesized phosphorylated lignosulfonate were introduced as greenfillers in citric acid-sucrose adhesives for bonding particleboard fabricated from areca leaf sheath(ALS).The characteristics ...Lignin,lignosulfonate,and synthesized phosphorylated lignosulfonate were introduced as greenfillers in citric acid-sucrose adhesives for bonding particleboard fabricated from areca leaf sheath(ALS).The characteristics of particleboards were compared to that of ultralow emitting formaldehyde(ULEF-UF).Thefillers derived from Eucalyptus spp.kraft-lignin were added forflame retardancy enhancement.10%of each lignin and modified lig-nin was added into the ULEF-UF and citric acid-sucrose bonded particleboards.Analyses applied to particle-boards included thermal characteristics,X-ray diffraction analysis(XRD),morphological properties,Fourier transform infrared spectroscopy(FTIR),as well as physical,mechanical,andfire resistance characteristics of the laboratory-fabricated particleboards.Lignin and modified lignin resulted in improved thermal stability of the composites bonded with ULEF-UF while the improvement in the particleboard bonded with citric acid-sucrose was not significant.The introduction offiller exerted a higher influence on the UF-bonded particleboards compared to composites fabricated with citric acid-sucrose.Generally,the presence of lignin,lignosulfonate,and phosphorylated lignosulfonate enhanced the mechanical strength of the ULEF-bonded particleboards,although their dimensional stability has deteriorated.Markedly,the use of lignin and lignosulfonate enhanced thefire resis-tance of the particleboards produced with lower observed weight loss.All laboratory particleboards exhibited satisfactoryfire resistance,attaining a V-0 rating in according to the UL-94 standard.展开更多
The fracture and tribological evaluation of dental composite resin containing pre-polymerized particle fillers were investigated. Composite resins, e.g. metafil, silux plus, heliomolar and palfique estelite were selec...The fracture and tribological evaluation of dental composite resin containing pre-polymerized particle fillers were investigated. Composite resins, e.g. metafil, silux plus, heliomolar and palfique estelite were selected as specimens in order to evaluate the effects of pre-polymerized particle filler on the fracture and wear characteristics of composite resins. In the wear tests, a ball-on-flat wear test method was used. The friction coefficient of metafil was quite high. The wear resistance of silux plus and palfique estelite was better than that of metafil and heliomolar under the same experimental condition. The main wear mechanism of composite resins containing pre-polymerized particle fillers was an abrasive wear by brittle fracture of pre-polymerized particles and by debonding of fillers and matrix.展开更多
Slow/controlled release fertilizers （SRFs/CRFs） have been paid more at- tentions by the researchersin recent years. In this paper, the application effects and methods, types, current problem and development prospect...Slow/controlled release fertilizers （SRFs/CRFs） have been paid more at- tentions by the researchersin recent years. In this paper, the application effects and methods, types, current problem and development prospect of SRFs/CRFsboth at home and abroad were reviewed. The production principles and processes of urea- formaldehyde slow release fertilizers were introduced; and It is suggested that the urea-formaldehyde slow release fertilizers show great development to ease energy and environment pressure.展开更多
UV-curable polyurethane prepolymer and photoinitiator 1173 were facilely encapsulated in a poly（urea-formaldehyde） shell, which was in situ formed by the polymerization of formalde-hyde and urea in an oil-in-water e...UV-curable polyurethane prepolymer and photoinitiator 1173 were facilely encapsulated in a poly（urea-formaldehyde） shell, which was in situ formed by the polymerization of formalde-hyde and urea in an oil-in-water emulsion. The diameters of the microcapsules ranged from 118 μm to 663 μm depending on agitation speed, and were obtained via optical mi-croscopy and scanning electron microscopy analyses. The encapsulation percent and the yield of microcapsules prepared at the agitation speed of 600 r/min can reach 97.52wt% and 65.23wt%, respectively. When the water-borne polyurethane （WPU） coating embedded with the prepared microcapsules were scratched, the healing agent could be released from rup-tured microcapsules and lled the scribed region. The excellent anticorrosion properties of the WPU coating embedded with the prepared microcapsules were con rmed by the results obtained from both electrochemical impedance spectroscopy and Tafel curves.展开更多
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 the...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.展开更多
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 intr...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.展开更多
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 ...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）.展开更多
Water-dispersed polyurethane (PU) adhesive is a novel and highly efficient adhesive with broad application potential. In this study, the key parameters affecting the synthesis and application of this adhesive were exa...Water-dispersed polyurethane (PU) adhesive is a novel and highly efficient adhesive with broad application potential. In this study, the key parameters affecting the synthesis and application of this adhesive were examined, and optimal conditions were identified. The water-dispersed PU adhesive was successfully synthesized, and applied in the fastness test of pigment printing on cotton fabric. The data demonstrated that all the fastnesses of PU adhesive were better than that of the conventional PA one.展开更多
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 mod...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.展开更多
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 degradatio...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.展开更多
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-si...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.展开更多
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 ...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.展开更多
基金the Graduate Developing Innovation Project of Jiangsu Province of China (No. CXZZ11-0306)the Major State Basic Research and Development Program of China (No.2007CB209400)
文摘A new composite two component grout comprised of modified urea-formaldehyde resin and cement was formulated to take account of the advantages and disadvantages of both the cement grout and the chem- ical grout. The new grout is designed for water blocking by reinforcing as well as seepage control by bore grouting. The A component consists of a modified urea-formaldehyde resin A component, some cement, and some water. The B component is an alkaline coagulant. An orthogonal test of four factors at three lev- els showed that gel time increased with increased water content and with urea-formaldehyde resin con- tent. Gel time decreased at increased levels of alkaline coagulant. The A component of this new composite grout is stable over time. A mixed cross-over test showed that as the volume ratio of A to B increases the gel time falls at first but then increases. The solid strength decreases with increasing levels of the B com- ponent. The solid strength increases over time and becomes stable by the 28th day after mixing. The vis- cosity increases with increasing levels of resin A component. The increase is exponential and may be fit to： μ = 8.162e0.0286x.
基金uported by the National Natural Science Foundation of China !(Grant No. 29574164)
文摘Spherical macroporous adsorbents with active sites capable of hydrogen bonding adsorption based on urea-formaldehyde condensed polymer were synthesized via reversed suspension polymerization. The properties of the obtained adsorbent were also investigated in detail. The results showed that the water permeability could be improved by adding hydroxyl-containing organic compound moiety into the adsorbent. The specific surface area and average pore diameter of these adsorbents increased while the porosity first increased then decreased with the increase of the amount of the added hydroxyl-containing compound.
文摘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.
文摘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.
基金funded by the Equity Project Universitas Sumatera Utara(Number:10/UN5.2.3.1/PPM/KPEP/2023),which is entitled Pengembangan Papan Partikel Tahan Api Rendah Emisi Berbahan Limbah Tanaman Mangrove dan Limbah Tanaman Pertanian Melalui Penambahan Lignin Terfosforilasi Sebagai Filler.PT Greenei Alam Indonesia(PT GAI)contributed to providing the areca leaf sheath through the implementation of a collaboration agreement with the Research Center for Biomass and Bioproducts BRIN FY 2023-2025.
文摘Lignin,lignosulfonate,and synthesized phosphorylated lignosulfonate were introduced as greenfillers in citric acid-sucrose adhesives for bonding particleboard fabricated from areca leaf sheath(ALS).The characteristics of particleboards were compared to that of ultralow emitting formaldehyde(ULEF-UF).Thefillers derived from Eucalyptus spp.kraft-lignin were added forflame retardancy enhancement.10%of each lignin and modified lig-nin was added into the ULEF-UF and citric acid-sucrose bonded particleboards.Analyses applied to particle-boards included thermal characteristics,X-ray diffraction analysis(XRD),morphological properties,Fourier transform infrared spectroscopy(FTIR),as well as physical,mechanical,andfire resistance characteristics of the laboratory-fabricated particleboards.Lignin and modified lignin resulted in improved thermal stability of the composites bonded with ULEF-UF while the improvement in the particleboard bonded with citric acid-sucrose was not significant.The introduction offiller exerted a higher influence on the UF-bonded particleboards compared to composites fabricated with citric acid-sucrose.Generally,the presence of lignin,lignosulfonate,and phosphorylated lignosulfonate enhanced the mechanical strength of the ULEF-bonded particleboards,although their dimensional stability has deteriorated.Markedly,the use of lignin and lignosulfonate enhanced thefire resis-tance of the particleboards produced with lower observed weight loss.All laboratory particleboards exhibited satisfactoryfire resistance,attaining a V-0 rating in according to the UL-94 standard.
文摘The fracture and tribological evaluation of dental composite resin containing pre-polymerized particle fillers were investigated. Composite resins, e.g. metafil, silux plus, heliomolar and palfique estelite were selected as specimens in order to evaluate the effects of pre-polymerized particle filler on the fracture and wear characteristics of composite resins. In the wear tests, a ball-on-flat wear test method was used. The friction coefficient of metafil was quite high. The wear resistance of silux plus and palfique estelite was better than that of metafil and heliomolar under the same experimental condition. The main wear mechanism of composite resins containing pre-polymerized particle fillers was an abrasive wear by brittle fracture of pre-polymerized particles and by debonding of fillers and matrix.
基金Supported by the Special Fund for Construction of National Tea Industry Technology System(CARS-23)Funding Project of Hubei Agricultural Science and Technology Innovation Center(2011-620-005-003-04)~~
文摘Slow/controlled release fertilizers （SRFs/CRFs） have been paid more at- tentions by the researchersin recent years. In this paper, the application effects and methods, types, current problem and development prospect of SRFs/CRFsboth at home and abroad were reviewed. The production principles and processes of urea- formaldehyde slow release fertilizers were introduced; and It is suggested that the urea-formaldehyde slow release fertilizers show great development to ease energy and environment pressure.
文摘UV-curable polyurethane prepolymer and photoinitiator 1173 were facilely encapsulated in a poly（urea-formaldehyde） shell, which was in situ formed by the polymerization of formalde-hyde and urea in an oil-in-water emulsion. The diameters of the microcapsules ranged from 118 μm to 663 μm depending on agitation speed, and were obtained via optical mi-croscopy and scanning electron microscopy analyses. The encapsulation percent and the yield of microcapsules prepared at the agitation speed of 600 r/min can reach 97.52wt% and 65.23wt%, respectively. When the water-borne polyurethane （WPU） coating embedded with the prepared microcapsules were scratched, the healing agent could be released from rup-tured microcapsules and lled the scribed region. The excellent anticorrosion properties of the WPU coating embedded with the prepared microcapsules were con rmed by the results obtained from both electrochemical impedance spectroscopy and Tafel curves.
基金Supported by the National Natural Science Foundation of China(Nos.50775222 and 50735006)
文摘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.
文摘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.
文摘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）.
文摘Water-dispersed polyurethane (PU) adhesive is a novel and highly efficient adhesive with broad application potential. In this study, the key parameters affecting the synthesis and application of this adhesive were examined, and optimal conditions were identified. The water-dispersed PU adhesive was successfully synthesized, and applied in the fastness test of pigment printing on cotton fabric. The data demonstrated that all the fastnesses of PU adhesive were better than that of the conventional PA one.
基金Sponsored by the Ministerial Level Advanced Research Foundation(20060013)
文摘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.
文摘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.
文摘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.
文摘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.
