Preparation of Environmentally Friendly Urea-Hexanediamine-Glyoxal(HUG)Resin Wood Adhesive

Using non-toxic,low-volatile glyoxal to completely replace formaldehyde for preparing urea-glyoxal(UG)resin adhesive is a hot research topic that could be of great interest for the wood industry.However,urea-glyoxal(UG)resins prepared by just using glyoxal instead of formaldehyde usually yields a lower degree of polymerization.This results in a poorer bonding performance and water resistance of UG resins.A good solution is to pre-react urea to preform polyurea molecules presenting already a certain degree of polymerization,and then to condense these with glyoxal to obtain a novel UG resin.Therefore,in this present work,the urea was reacted with hexamethylene diamine to form a polyurea named HU,and then this was used to react it with different amounts of glyoxal to synthesize hexamethylenediamine-urea-glyoxal(HUG)polycondensation resins,and to use this for bonding plywood.The results show that the glyoxal can well react with HU polyuria via addition and schiff base reaction,and also the HUG resin exhibits excellent bonding strength and water resistance.The shear strength of the plywood bonded with this HUG at 160°C hot press temperature as high as 1.93 MPa,2.16 MPa and 1.61 MPa,respectively,which meets the requirement of the China national standard GB/T 9846-2015(≥0.7 MPa),and can be a good choice as a wood adhesive for industrial application.

Effect of Multiple Coatings of One-step Self-etching Adhesive on Microtensile Bond Strength to Primary Dentin

Objective To investigate the effect of multiple coatings of the one-step self-etching adhesive on immediate microtensile bond strength to primary dentin.Methods Twelve caries-free human primary molars were randomly divided into 2 groups with 6 teeth each.In group 1,each tooth was hemisected into two halves.One half was assigned to control subgroup 1,which was bonded with a single-step self-etching adhesive according to the manufacturer's instructions;the other half was assigned to experimental subgroup 1 in which the adhesive was applied three times before light curing.In group 2,the teeth were also hemisected into two halves.One half was assigned to control subgroup 2,which was bonded with the single-step self-etching adhesive according to the manufacturer's instructions;the other half was assigned to experimental subgroup 2 in which three layers of adhesive were applied with light curing each successive layer.Microtensile bond strength was immediately tested after specimen preparation.Results When the adhesive was applied three times before light curing,the bond strength of the experimental subgroup 1(n=33,57.49±11.61 MPa) was higher than that of the control subgroup 1(n=31,49.71±11.43 MPa,P<0.05).When using the technique of applying multiple layers of adhesive with light curing each successive layer,no difference of immediate bond strength was observed between the control subgroup 2 and the experimental subgroup 2(P>0.05).Conclusion Multiple coatings of one-step self-etching adhesive can increase the immediate bond strength to primary dentin when using the technique of light-curing after applying three layers of adhesive.

Multiple Coatings can Improve the Bond Durability of One-step Self-etching Adhesive to Primary Dentin

Objective To investigate whether multiple coatings can improve the bond durability of one-step self-etching adhesive to primary dentin. Methods Twelve caries-free human primary molars were randomly divided into 2 groups. In group 1, each tooth was hemisected into 2 halves. One half was assigned to the control subgroup 1, which was bonded with a commercially available one-step self-etching adhesive according to the manufacturer＇s instruc- tions; the other half was assigned to experimental subgroup 1, in which the adhesive was applied three times before light curing. In group 2, one split half tooth was bonded with a commercially available one-step self-etching adhesive according to the manufacturer＇s instructions; for the other half, three layers of adhesive were applied with each successive layer of light curing. Specimens were stored in 0.9% NaC1 containing 0.02% sodium azide at 37℃ for 18 months and then were subjected to microtensile bond strength test and the fracture mode analysis. Results When the adhesive was applied three times before light curing, the bond strength of the ex- perimental subgroup 1 was significantly higher than that of the control subgroup 1 （47.46__＋13.91 vs. 38.12＋11.21 MPa, P〈O.05）. When using the technique of applying multiple layers of adhesive with each successive layer of light curing, no difference was observed in bond strength between the control subgroup and the experimental subgroup （39.40＋8.87 vs. 40.87-＋9.33 MPa, P〉O.05）. Conclusion Multiple coatings can improve the bond durability of one-step self-etching adhesive to primary dentin when using the technique of light-curing after applying 3 layers of adhesive.

Study on Camellia Oleifera Protein based Wood Adhesive by Epoxy Resin and Its Crosslinking Mechanism

Epoxy resin (EPR) was used to crosslink with Camellia oleifera Abel.protein to prepare wood adhesive,and the bonding performance and curing characteristics of which were mainly investigated,and the synthesis mechanism was also discussed by using model compounds.The experimental results show that EPR can significantly improve the bonding performance of Camellia oleifera Abel.protein-based adhesive,and the maximum of which reaches 0.72 MPa satisfies the strength requirement of Type II plywood in GB/T 17657-2013.After alkali treatment,the protein can more easily crosslink with EPR at low curing temperature,and the adhesive has high degree of crystallinity of curing products,high degree of crosslinking reaction,and high bonding strength.The reaction mechanism of EPR-modified Camellia oleifera Abel.protein adhesive can be divided into resinification phase and curing phase.

Determination of Water Diffusion Coefficients and Dynamics in Adhesive/Carbon Fiber Reinforced Epoxy Resin Composite Joints

To determinate the water diffusion coefficients and dynamics in adhesive/carben fiber reinforced epoxy resin composite joints, energy dispersive X-ray spectroscopy analysis（EDX） is used to establish the content change of oxy- gen in the adhesive in adhesive/carbon fther reinforced epoxy resin composite joints. As water is made up of oxygen and hydrogen, the water diffusion coefficients and dynamics in adhesive/carben fiber reinforced epoxy resin composite joints can be obtained from the change in the content of oxygen in the adhesive during humidity aging, via EDX analy-sis. The authors have calculated the water diffusion coefficients and dynamics in the adhesive/carbon fiber reinforced epoxy resin composite joints with the aid of beth energy dispersive X-ray spectroscopy and elemental analysis. The de- termined results with EDX analysis are almost the same as those determined with elemental analysis and the results al- so show that the durability of the adhesive/carbon fther reinforced epoxy resin composite joints subjected to silane cou- pling agent treatment is better than those subjected to sand paper burnishing treatment and chemical oxidation treat- ment.

SEM Comparison of Penetration in Artificial White Spots Lesion between an Infiltrant Resin and Two Adhesive Systems

White spot infiltration emerged as an alternative of non-invasive treatment to halt progression of the lesion, through the use of low viscosity resins that would permeate the porous enamel and form a physical barrier that would prevent the acid diffusion produced by micro-organisms. Purpose: To compare penetration levels in artificial white spot lesions, of infiltrant resin ICON&trade;and 2 conventional adhesives systems, XP-Bond&trade;and Single Bond 2&trade;. Methodology: White spot lesions (ICDAS code 2) were caused in 75 premolars or third molars were extracted in good conditions, by immersion in a 0.1 M lactic acid solution (pH 4.5) at 37℃ for 8 weeks. They were divided randomly into 3 groups of 25 samples and applied the following resins, Group A: ICON&trade;, B: XP-Bond&trade;and C: Single Bond 2&trade;. Subsequently, the enamel was removed with hydrochloric acid to expose resin saturated area and the samples were metalized with Au-Pd for SEM observation. The resin tags lengths were measured on microphotographs through software, and the values were analyzed with the statistics ANOVA and Scheffé post-test. Results: There were significant differences (p &trade;(82.7 μm ± 26.8 μm) compared to adhesive systems XP-Bond&trade;(58.5 μm ± 29.3 μm) and Single Bond 2&trade;(44.8 μm ± 32.5 μm). We found no significant differences between the two adhesive systems (p > 0.05). Conclusion: Under the conditions tested, the penetration of infiltrant ICON was significantly higher than the adhesive systems;however, it removes the surface layer of the enamel.

Effect of Self-adhesive Resin Cement and Tribochemical Treatment on Bond Strength to Zirconia

Aim To evaluate the interactive effects of different self- adhesive resin cements and tribochemical treatment on bond strength to zirconia. Methodology The following self-adhesive resin cements for bonding two zirconia blocks were evaluated： Maxcem （MA）, Smartcem （SM）, Rely X Unicem Aplicap （UN）, Breeze （BR）, Biscem （BI）, Set （SE）, and Clearfil SA luting （CL）. The specimens were grouped according to conditioning as follows： Group 1, polishing with 600 grit polishing paper; Group 2, silica coating with 110 μm Al2O3 particles which modified with silica; and, Group 3, tribochemical treatment - silica coating ＋ silanization. Specimens were stored in distilled water at 37℃ for 24 hours before testing shear bond strength. Results Silica coating and tribochemical treatment significantly increased the bond strength of the MA, UN, BR, B1, SE and CL to zirconia compared to #600 polishing. For both #600 polished and silica coating treatments, MDP- containing self-adhesive resin cement CL had the highest bond strengths to zirconia. Conclusion Applying silica coating and tribochemical treatment improved the bond strength of self-adhesive resin cement to zirconia, especially for CL.

YbF_3/SiO_2 Fillers as Radiopacifiers in a Dental Adhesive Resin

The objective of this study was to evaluate the effect of functionalizing a dental adhesive resin with YbF_3/SiO_2 fillers for use as radiopacifiers.Particles of YbF_3/SiO_2 were obtained with the high-energy mechanical milling method and characterized by both physical and chemical methods.After characterization,the particles were sieved and silanized prior to being incorporated into an adhesive resin.The stability of the particle suspension was then evaluated.After light activation,the radiopacity,degree of conversion,flexural strength and elastic modulus were determined.The dental adhesive resins with 10 and 15 wt% of filler provided satisfactory radiopacity,while flexural strength and elastic modulus were not affected.The degree of conversion was statistically lower than that of the control(p<0.05).The method used for incorporating the tested ytterbium fluoride/silicon dioxide particles at concentrations of 10 and 15 wt% was shown to be feasible for the development of a radiopaque dental adhesive system.

MUF Resins Improved by Citric Acid as Adhesives for Wood Veneer Panels

This article presents the first applied results of using citric acid in combinations with a melamine-urea-formal-dehyde(MUF)resin for bonding wood veneers.The chemical reactions involved are shown based on a MALDI ToF analysis of the reaction of the MUF resin with citric acid.The preliminary results of the physical and mechanical properties of the LVL prepared are also presented.Veneers from Populus sp were used to manufacture 5-layer laminated veneer lumber(LVL)of small dimensions.Five combinations of the amount of citric acid,MUF spread rate and pressing parameters were tested.LVL bonded with 20%of citric acid+100 g/m^(2)of MUF,hot-pressed using a 3-step process with maximum 1.5 MPa of pressure yielded the board with better dimensional stability and mechanical properties.It could be concluded that citric acid in combination with MUF can be used for bonding wood veneer and the research should be continued to study further the parameters involved and to enhance the results.

Synthetic Process of Bio-Based Phenol Formaldehyde Adhesive Derived from Demethylated Wheat Straw Alkali Lignin and Its Curing Behavior

Lignin is a natural biopolymer with a complex three-dimensional network, commercially obtained from wasteliquid of paper pulp and bioethanol production, and could be a candidate for preparation of environment-friendlybio-based polyphenol material. In the present work, the demethylated wheat straw alkali lignin (D-Lig), preparedby demethylation of wheat straw alkali lignin (Lig) using an in-situ generated Lewis acid, was used to synthesizebio-based phenol formaldehyde resin adhesive (D-LPF) applied in plywood. Effects of synthetic process’s factors,including lignin substitution for phenol, NaOH concentration and molar ratio of formaldehyde to phenol, on thebonding strength and free formaldehyde content of D-LPF were investigated in detail, and the optimum syntheticprocess of D-LPF was obtained as following: Lignin substitution for phenol 60%, NaOH concentration 5.0% andmolar ratio of formaldehyde to phenol 2.0, and under the optimum reaction condition, the D-LPF presented lower free formaldehyde content (0.18%) and higher bonding strength (2.19 MPa), which was better than those ofcontaining-lignin phenol formaldehyde resin adhesive (LPF). Additionally, the curing behavior of the adhesivewas studied by differential scanning calorimetry (DSC) combined with gel time. It can be obtained that D-LPFresin adhesive had the shortest gel time, and fastest curing rate, compared with those of PF and L-PF resin adhesives. The curing kinetics data was fitted well by Kissinger model using non-isothermal DSC method, and theaverage activation energy value was 85.3 kJ/mol, slightly higher than that of commercial PF resin, while lowerthan that of LPF (90.2 kJ/mol). Finally, based on the analytical results of high temperature fourier transform infrared spectroscopy (FTIR), a possible curing mechanism of D-LPF was proposed.

Preparation of the Heat Resistant Adhesive of NBR Modified BMI

A Kind of homogeneous resin , which can be used as thermal resistant adhesive and matrix for composite, was prepared by bis (4-maleimidophenyl) methane ( BMI), 4,4’ -diaminodiphenylmethane( DDM), aniline (An), phenol type epoxy resin ( F-51 ) and nitrile -butadiene rubber ( NRR) through solution copolymer-ization . The reaction from prepolymerization to curing of the resin system was studied. And the factors such as raw material ratio and curing temperature, which affect thermal resistance and adhesives of cured product, were also analyzed. SEM and IR spectra were utilized to discuss the mechanisms of toughness and reaction of modified BMI.

Synthesis of Green Adhesive with Tannin Extracted from Eucalyptus Bark for Potential Use in Wood Composites

Recently,the exploitation of renewable plant resources in the formulation of adhesives is very promising for their availability at low coast,as well as their richness in biomolecules such as polyphenols.In this way,many research studies tannins extracted from different sources such as mimosa,quebracho,and pine have been the subject of very satisfactory recent studies.In this paper,a new complete characterization of the tannins extracted from the bark of eucalyptus globulus harvested from two regions in Algeria was achieved.The structural characterization enabled us to confirm the richness in condensed tannins,particularly in procyanidin and prodelphinidin units.The most reactive tannins obtained during extraction at 70℃(yield:27.1%)have a Stiasny number of 75.92%.This extract was used for the formulation of adhesives(tannin/hexamine).The thermal characterizaction of the adhesives showed higher stability for the tannin formulation of eucalyptus/hexamine as well as an excellent mechanical performance with a MOE of 2807 MPa at 180℃and shear strength of 689.4 N/mm^(2).

In vitro analysis of riboflavin-modified,experimental,two-step etch-and-rinse dentin adhesive:Fourier transform infrared spectroscopy and micro-Raman studies

To modify two-step experimental etch-and-rinse dentin adhesive with different concentrations of riboflavin and to study its effect on the bond strength,degree of conversion,along with resin infiltration within the demineralized dentin substrate,an experimental adhesive-system was modified with different concentrations of riboflavin（mlm,0,1%,3%,5%and 10%）.Dentin surfaces were etched with 37%phosphoric acid,bonded with respective adhesives,restored with restorative composite-resin,and sectioned into resin-dentin slabs and beams to be stored for 24 h or 9 months in artificial saliva.Micro-tensile bond testing was performed with scanning electron microscopy to analyse the failure of debonded beams.The degree of conversion was evaluated with Fourier transform infrared spectroscopy（FTIR） at different time points along with micro-Raman spectroscopy analysis.Data was analyzed with one-way and two-way analysis of variance followed by Tukey＇s for pair-wise comparison.Modification with 1%and 3%riboflavin increased the micro-tensile bond strength compared to the control at 24 h and 9-month storage with no significant differences in degree of conversion（P〈0.05）.The most predominant failure mode was the mixed fracture among all specimens except 10%riboflavin-modified adhesive specimens where cohesive failure was predominant.Raman analysis revealed that 1%and 3%riboflavin adhesives specimens showed relatively higher resin infiltration.The incorporation of riboflavin in the experimental two-step etch-and-rinse adhesive at 3%（mlm） improved the immediate bond strengths and bond durability after 9-month storage in artificial saliva without adversely affecting the degree of conversion of the adhesive monomers and resin infiltration.

A Boron-based Adhesion Aid for Efficient Bonding of Silicone Rubber and Epoxy Resin

We improved the adhesion between silicon based insulating materials and epoxy resin composites by adding the adhesion promoter cycloborosiloxane(BSi,cyclo-1,3,3,5,7,7-hexaphenyl-1,5-diboro-3,7-disiloxane).The experimental results show that the addition of BSi in the silicone rubber(SR)system significantly increases the tensile shear strength between BSi and epoxy resin(EP),reaching 309%of the original value.On this basis,the mechanism of BSi to enhance the adhesion effect was discussed.The electron deficient B in BSi attracted the electron rich N and O in EP to enhance the chemical interaction,combined with the interfacial migration behavior in the curing process,to improve the adhesion strength.This study provides the design and synthesis ideas of adhesive aids,and a reference for further exploring the interface mechanism of epoxy resin matrix composites.

600 Mesh Silicon Carbide Corona Protection Varnish with EPOXY/OMMT Nano-composite Adhesive

A new corona protection varnish was prepared by using epoxy/montmorillonite nanocomposite and pure epoxy resin as adhesives respectively.The adhesive with different amounts of organic montmorillonite（OMMT） was mixed with 1200 mesh silicon carbide（Si C） by different weight ratios.The surface states of the varnishes with various adhesives were observed by powerful optical microscope.Some properties of the varnishes were analyzed during the enduring time under 5kV/cm DC,such as the relation of change in nonlinear coefficient,natural surface resistivity,and surface temperature variation.The results showed that the amounts of OMMT had little effect on the natural surface resistance of the varnish but had important influence on the nonlinear property of the varnish.When the range of the OMMT content was 2wt% to 6wt%,the nonlinear coefficient of all materials with epoxy/OMMT nano-composite adhesive was higher than that with pure epoxy resin adhesive.The surface temperature of the varnish with epoxy/OMMT nanocomposite adhesive was all lower than that with the pure epoxy resin adhesive under high electrical field strength.

Effect of enamel-grinding on adhesionstrength of enamel-resin junction

In this paper,we have tested the normal and mottled enamel in order to get some instructive information for the clinical treatment. As demonstrated by the results of our experiments, the grinding treatment of the enamel superficial layer has no significant improvement on the adhesional strength of the junction between the normally developed teeth and the resin. However, it does exhibit evident effect on the adhesional strength of the junction between the fluorosis teeth and the repairing resin.

Dental Post Based on Epoxy Resin/Zirconium Phosphate Composite Aiming Prosthetic Dentistry

The aim of this research was to develop an intrarradicular dental post based on epoxy resin/nano zirconium phosphate composite with potential appli-cation in prosthetic dentistry. Zirconium phosphate (ZrP) nanoparticle was synthesized by a reaction between phosphoric acid (H3PO4) and zirconium (IV) oxide chloride 8-hydrate (ZrOCl2·8H2O) and applied as filler. Commer-cial epoxy resin and hardener were used as polymer matrix. The composites were prepared at different proportions of epoxy resin/hardener, filler amount, reaction time and temperature. Infrared revealed that degree of conversion decreased with amount of ZrP. Insoluble matter was upper than 97%. Thermogravimetry indicated two steps of degradation. The best values of flexural modulus and flexural strength were achieved for the post desig-nated as 1:0.25:0.25. Laser scanning confocal microscopy suggested that the morphology of the posts fractured surface varied according to epoxy-resin:hardener ratio and the ZrP amount. From atomic force micros-copy, the topographic view exposed the shape and size of ZrP particles. Field emission scanning electron microscopy and energy dispersive spectroscopy indicated good adhesion between epoxy resin matrix-ZrP and that the pres-ence of phosphate rendered brittle the fracture surface.

环氧树脂增韧体系对胶粘剂热性能的影响

本文对比考察了端羧基液体丁腈橡胶(CTBN)和核壳橡胶增韧剂对环氧树脂胶粘剂体系固化反应热、玻璃化转变温度(Tg)、膨胀系数以及拉伸剪切强度的影响。研究结果表明:CTBN和核壳橡胶均能降低环氧树脂胶粘剂体系的固化反应热,CTBN体系固化反应峰值温度升高,核壳橡胶体系固化反应峰值温度变化不大;CTBN和核壳橡胶的添加,均降低了胶粘剂体系的Tg,CTBN体系下降幅度大于核壳橡胶体系;CTBN和核壳橡胶的添加,均增大了胶粘剂体系的膨胀系数(<Tg时),CTBN体系增大幅度大于核壳橡胶体系;随着CTBN和核壳橡胶添加量的不断增加,拉伸剪切强度均呈现出先增加后降低的趋势。

国产芳纶用防弹树脂胶黏剂配方设计研究

现有防弹树脂胶黏剂体系与国产芳纶的相容性不佳,制得的芳纶防弹无纬布表面不光滑、不平整,存在起泡现象,同时其防弹性能难以满足标准要求。对国产芳纶用防弹树脂胶黏剂配方进行了设计研究,采用80.0%聚氨酯D、10.0%树脂E、9.5%树脂F、0.5%白炭黑的防弹树脂胶黏剂配方制得的芳纶防弹无纬布表观性能优异,布面光滑、平整,常温及高温环境下均无起泡现象,同时防弹性能优异,穿透层数少,凹陷值小,满足GA 141—2010标准要求。

增粘树脂对硫醇调节型氯丁橡胶胶料性能的影响

研究4种增粘树脂(A-90树脂、203树脂、古马隆树脂和Koresin树脂)及增粘树脂并用体系(A-90树脂/Koresin树脂和古马隆树脂/Koresin树脂并用体系)对硫醇调节型氯丁橡胶(CR)胶料性能的影响。结果表明:4种增粘树脂及增粘树脂并用体系的加入使胶料的门尼粘度降低,门尼焦烧时间延长,A-90树脂及增粘树脂并用体系的加入增大了硫化胶的交联密度;4种增粘树脂及增粘树脂并用体系的加入对硫化胶的硬度和拉伸强度影响不明显,使硫化胶的拉断伸长率增大,回弹值减小,古马隆树脂/Koresin树脂并用体系的加入增大了硫化胶的300%定伸应力,提高了硫化胶的耐热氧老化性能,保持了硫化胶的减震性能;4种增粘树脂及增粘树脂并用体系的加入提高了硫化胶的粘合性能,加入古马隆树脂和A-90树脂的硫化胶的粘合强度较大。