Bonding effectiveness of different dentin conditions on etch-and-rinse mode of two universal adhesives: the confocal laser scanning and shear bond strength

The purpose of this study was to evaluate the shear bond strength and the morphological differences of adhesive/dentin interface of two one-step universal adhesives to dentin using different dentin-conditioning methods with etch-and-rinse mode. Ninety-six dentin specimens were randomly divided into two groups based on application of two adhesives and assigned to three subgroups according to different dentin conditioning (wet-bonding; air-dried; rewetting). After etching and rinsing, experimental dentin conditioning was conducted on the etched dentin specimens. All specimens were subjected to shear bond strength testing using a universal testing machine, and all data were statistically analyzed using two- way analysis of variance with Tukey’s post hoc test. All debonded specimens were examined for fracture pattern by scanning electron microscopy (SEM). Adjunctively, one specimen per group was prepared by the same processing and longitudinally sectioned. Then, the infiltration ability of adhesives into dentin was examined by observing the interface using confocal laser-scanning microscopy (CLSM). Wet and Rewet groups exhibited significantly higher shear bond strength than dry groups on the etch-and-rinse system, regardless of different adhesives. The bond strength between wet and rewet groups showed no significant difference in Tukey’s test. Analysis of failure surface using SEM showed that predominant failure patterns were mixed in both the wet-bonding group and dry-bonding group. CLSM presented that resin penetration into etched dentin was enhanced similarly in wet and rewet group. Application of rewetting agents on dried dentin increased the bonding performance of universal adhesives on etch-and-rinse mode.     

一种中温固化高强度耐烧蚀环氧结构胶的特性

介绍了一种中温固化、粘接强度高、氧-乙炔烧蚀性能好的环氧胶粘剂,讨论了树脂和填料等对组分性能和工艺的影响。满足了小型固体火箭发动机中金属和玻璃钢之间的粘接及其耐烧蚀性能的要求。     

The effect of primers on adhesive properties and strength of adhesive joints made with polyurethane adhesives

The paper presents selected aspects of the effect of primers on adhesive properties and strength of aluminium sheet adhesive joints, made using polyurethane adhesives. The strength of adhesive joints was determined based on two cure time variants: 15 and 64 h. It was found that the longer cure time at a humidity of 33% is more desired, as it leads to a substantial increase in strength of the tested adhesive joints. In addition, two variants of surface preparation were applied: degreasing and degreasing followed by the application of a primer (a pro-adhesive agent). It was observed that the primer application prior to the application of an adhesive leads to a significant increase in strength compared to the variant where the adhesive application is preceded only by degreasing. Moreover, the aluminium sheet surface that was subjected to cataphoretic painting and priming exhibits better adhesive properties. It has a higher value of both surface free energy and its dispersion and polar components compared to the surface that was only subjected to degreasing.     

环保型低剥离力压敏胶的研制

采用半连续乳液聚合法制备了一种丙烯酸类水基型低剥离力压敏胶。主要考察了甲基丙烯酸(MAA)等功能单体和外加交联剂对产物性能的影响。实验表明,随MAA等亲水单体用量的增多,乳液粘度会增大,而引入交联单体在实验范围内可显著降低剥离强度。功能单体用量有一合适范围。选用较高反应活性的氨基树脂作交联剂,可改善耐温性,保持初粘力,得到综合性能较好的低剥离力压敏胶。     

无机填料对环氧树脂胶粘剂强度的影响

研究了不同无机填料对环氧树脂胶粘剂强度的影响。试验结果表明，以碳化硅、刚玉为填料的胶粘剂强度较高；采用较细粒度的填料有利于提高胶粘剂的压缩强度；当碳化硅填料的质量份数在80～160(相对于环氧树脂100份)时，压缩强度达到较高值，粘接强度也保持在较好水平。     

建筑结构胶耐湿热老化性能测试方法研究

GB50367《混凝土结构加固设计规范》中关于耐湿热老化性能测试方法由于试验周期较长,而给建筑结构胶的工程进场复检带来困难。以环氧树脂类建筑结构胶的配方特点为基础,研究对比了适用于工程进场检验的湿热老化性能快速测试方法,并和GB50367进行对比．考查了增韧剂、填料、固化剂、助剂等各种因素以及各种因素的“叠加”效应对2种测试方法结果的影响。研究表明,800C恒温水浴／7d条件下的快速测试方法和GB50367结果基本一致,2者的偏差绝对值不超过15％。快速测试方法能快速地检验出建筑结构胶的耐湿热老化性能．     

High temperature performance of soy-based adhesives

We studied the high temperature performance of soy meal processed to different protein concentrations (flour, concentrate, and isolate), as well as formulated soy-based adhesives, and commercial nonsoy adhesives for comparison. No thermal transitions were seen in phenol-resorcinol-formaldehyde (PRF) or soy-phenol-formaldehyde (SoyPF) or in as-received soy flour adhesive during differential scanning calorimetry scans heating at 10?°C/min between 35 and 235?°C. Heat flow rates decreased in the order soy flour (as received)?>?SoyPF?>?PRF?>?emulsion polymer isocyanate (EPI). In thermogravimetric analysis (TGA) scans from 110 to 300?°C at 2?°C/min, total weight loss decreased in the order soy flour (as-received)>SoyPF?>?PRF?>?casein?>?maple?>?EPI. For bio-based materials, the total weight loss (TGA) decreased in the order soy flour (as-received) > concentrate, casein?>?isolate. Dynamic mechanical analysis from 35 to 235?°C at 5?°C/min of two veneers bonded by cured adhesive showed 30–40% decline in storage modulus for maple compared to 45–55% for the adhesive made from soy flour in water (Soy Flour) and 70–80% for a commercial poly(vinyl acetate) modified for heat resistance. DMA on glass fiber mats showed thermal softening temperatures increasing in the order Soy Flour?<?casein?<?isolate?<?concentrate. We suggest that the low molecular weight carbohydrates plasticize the flour product. When soy-based adhesives were tested in real bondlines in DMA and creep tests in shear, they showed less decrease in storage modulus than the glass fiber-supported specimens. This suggests that interaction with the wood substrate improved the heat resistance property of the adhesive. Average hot shear strengths (ASTM D7247) were 4.6 and 3.1?MPa for SoyPF and Soy Flour compared to 4.7 and 0.8?MPa for PRF and EPI and 4.7 for solid maple. As a whole, these data suggest that despite indications of heat sensitivity when tested neat, soy-based adhesives are likely to pass the heat resistance criterion required for structural adhesives.     

Preconditioning of epoxy film adhesives for bond strength improvement

The moisture level of two commercial overaged epoxy film adhesives has been controlled by drying under vacuum and/or exposure to humid atmosphere. Shear and peel bond strengths of the conditioned adhesives were evaluated. Predrying of the uncured adhesive under vacuum (3–5 mm Hg) at room temperature is shown to be very effective for bond strength enhancement. Additional humidifying/drying circles show the same effect but some irreversible degradation occurs and only partial improvement of adhesive bond strength is achieved.     

Bonding adhesive joints with radio-frequency dielectric heating

The feasibility of using radio-frequency (RF) dielectric heating to cure thermoset adhesives has been evaluated. Thermoset and thermoplastic polymer panels have been bonded to steel using conventional one-and two-part epoxy and two-part urethane adhesives. Process cycle times for adhesive cure using RF heating were about 20 to 60 seconds, compared with about 20 to 30 minutes for the same materials using conventional oven-cure methods. Thermoset substrates bonded included glass fibre-reinforced composite panels based on sheet moulding compound (SMC) and resin transfer moulding styrene-vinylester (RTM). Thermoplastics such as polycarbonate, polyarylate, Noryl, ABS and polymethylmethacrylate were also successfully bonded. RF bonding experiments were performed by preparing and testing lap-shear joints as well as by joining a large test structure with a 25 mm x 1.25 m bondline. Bonding of painted steel to SMC composite, SMC to SMC and steel to RTM composite were also accomplished using the RF dielectric heating process.     

改性耐高温胶粘剂的研究进展

综述了近年来国内外改性耐高温胶粘剂的发展现状,对环氧树脂(EP)、酚醛树脂(PF)、有机硅、含氮杂环以及无机耐高温胶粘剂的性能、应用和改性方法进行了详细的论述,主要介绍了提高各种胶粘剂耐高温性能的改性方法和技术途径,并对今后改性耐高温胶粘剂的发展趋势作了展望。     

Preparation and properties of novel dentin adhesives with esterase resistance

A new methacrylate monomer, trimethylolpropane mono allyl ether dimethacrylate (TMPEDMA), was synthesized and evaluated. This branched methacrylate was designed to increase esterase‐resistance when incorporated into conventional HEMA (2‐hydroxyethyl methacrylate)/BisGMA (2,2‐bis[4(2‐hydroxy‐3‐methacryloyloxy‐propyloxy)‐phenyl] propane) dental adhesives. The new adhesives, HEMA/BisGMA/TMPEDMA in a 45/30/25 (w/w) ratio were formulated with H₂O at 0 (A0T) and 8 wt % water (A8T) and compared with control adhesives (HEMA/BisGMA, 45/55 (w/w), at 0 (A0) and 8 wt % (A8) water). Camphoroquinone (CQ), 2‐(dimethylamino) ethyl methacrylate and diphenyliodonium hexafluorophosphate were used as photoinitiators. The new adhesives showed a degree of conversion comparablewith the control and improved modulus and glass transition temperature (T_g). Exposure of photopolymerized discs to porcine liver esterase for up to eight days showed that the net cumulative methacrylic acid (MAA) release in adhesives formulated with the new monomer and 8% water (A8T: 182 μg/mL) was dramatically (P < 0.05) decreased in comparison to the control (A8: 361.6 μg/mL). The results demonstrate that adhesives made with the new monomer and cured in water to simulate wet bonding are more resistant to esterase than conventional HEMA/BisGMA adhesive. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Heat transfer model for the cooling of hot melt adhesives

Results concerning the crystallization of a hot melt adhesive are presented. This adhesive was a liquid at high temperature (160°C) and was deposited on a wood slab kept at ambient temperature. Cooling can be enhanced by circulating air above the adhesive. The temperature within the adhesive and the wood were measured versus time under three conditions: when the cooling of the upper external part of the adhesive was due to free convection; when it was due to forced convection (to simulate the moving of the assembly line), and in the case where a second wood slab was placed to simulate a joint. It was observed that for a sufficiently thick adhesive film the cooling was slowed down by heat transfer to the wood. A model combining the heat conduction and the kinetic law of crystallization is presented. This model permits the prediction of the evolution of temperature at each point in the adhesive or in the wood for different geometries. The beginning of the crystallization at each point in the adhesive is also predicted. By knowing the rheological properties of the adhesive versus temperature, using the model giving the variation of temperature versus time, one can determine the variation of storage and loss moduli versus time.     

高强度耐热环氧胶带的研制

所研制的是耐热性环氧胶，通过选择基材（包括处理方法）、固化促进剂和耐热性改性剂等，并改进胶带的制法，得到了粘接强度高、耐热性好、使用期长的环氧胶带，选择好的促进剂，不但可以提高固化速度，还可以使胶带具有较长的适用期，先溶解双氰双胺，再将其它组合加入到胶液，得到的胶带的性能较好。     

Shear bond strength to dentine of dental adhesives containing hydroxyapatite nano-fillers

The aim of this study was to compare the effect of hydroxyapatite (HAP) nano-rods (HAP_rods) and HAP nano-sticks (HAP_sticks) added to commercial adhesives on the macro-shear bond strength (SBS) to dentine and morphology of the adhesive–dentine interface. HAP was added to Single Bond Universal (SBU, 3M ESPE) and Te-Econom Bond (TeE; Ivoclar Vivadent), in the form of water suspensions to avoid agglomeration of nano-particles and to achieve HAP concentrations of 0.5, 1.0 and 1.5 wt%. Following a ‘total-etch’ or a ‘self-etch’ protocol, the adhesives were applied to flat dentine surface of 162 intact human, third molars (N = 6/group). Composite (Z250, 3M ESPE) was built-up using a split stainless steel mould, 3 mm in diameter. SBS was tested using a universal testing machine at 1 mm/min until fracture. Data were statistically analysed using two-way and one-way analysis of variance with Tukey’s post-test (α = 0.05). HAP_rods had no significant effect on SBS of the tested adhesives while HAP_sticks improved bond strength to dentine only of adhesives applied following the ‘total-etch’ total-etch protocol. SBS values of SBU containing 1% HAP_sticks (15.10 ± 2.96 MPa) and TeE containing 0.5% HAP_sticks applied following the total-etch protocol (12.96 ± 4.48 MPa) were higher than those of their respective control groups (10.36 ± 2.68 and 7.97 ± 3.64 MPa). Samples with higher SBS showed more ‘mixed’ failures. HAP nano-fillers may improve bond strength of total-etch adhesives without an adverse effect on adhesive dispersion on dentine and its ability to infiltrate dentinal tubules.     

环氧粘合剂粘接聚四氟乙烯板/不锈钢的耐温性研究

考察了经表面化学活化的3种纯聚四氟乙烯(PTFE)板和1种聚苯酯填充PTFE板在室温和高温下的拉伸性能,用两类环氧粘合剂DG–3S和JF205–1对这4种PTFE板与不锈钢进行了粘接,研究了室温和高温下这两种粘合剂的粘接效果。结果表明,4种活化PTFE板经高温老化后的拉伸性能变化不明显;室温下两种环氧粘合剂对4种PTFE板与不锈钢的粘接性能均良好,但DG–3S粘合剂不适合高温下对PTFE板/不锈钢的粘接,经耐热改性的JF205–1粘合剂在300℃下的粘接性能则较好;JF205–1粘接聚苯酯填充PTFE板/不锈钢的实际粘接性能较好且具有高的耐磨性能和抗蠕变性,在满足实际粘接要求的情况下可应用于制造发动机零部件。     

An experimental study on the dependence of the strength of adhesively bonded joints with thickness and mechanical properties of the adhesives

Adhesive bonding joints are widely applied in many engineering fields. Their overall strength is much dependent on the thickness of adhesive layers. Many previous experimental studies have found that the ultimate failure strength of the bonding structure increases with the decrease of the adhesive thickness. However, few of them consider the effect of adhesive intrinsic material parameters on the relation between the overall strength and adhesive thickness. In the present investigation, the effect of the adhesive thickness on the overall strength of the lightweight metallic adhesive bonding joints was experimentally studied, considering the effect of the adhesive toughness. The results show that the variations of overall strength resulting from the adhesive thicknesses have remarkable discrepancy due to the toughness of the adhesive, which is in agreement with the previous model prediction.     

导电胶的研究进展

随着现代科学技术的高速发展,电子仪器正在向小型化、微型化、高集成化方向迈进,导电胶作为一种新兴的绿色环保微电子封装材料,广泛应用于电子产品中。本文介绍了导电胶的组成,从宏观和微观角度对导电机理进行了概述,并对国内外最新成果进行了综述,最后对各向异性导电胶的发展前景作了展望。     

有机硅胶粘剂的耐热性能研究

以自制的有机硅树脂为基体,通过添加耐热填料制得一种耐高温胶粘剂。探讨了无机耐热填料的受热温度、受热时间对胶粘剂剪切强度的影响。试验结果表明:当m(TiO2)∶m(ZnO)=1.0∶1.0时,胶粘剂在300℃时受热1 h,能够获得高达6.61 MPa的拉伸剪切强度;当受热时间延长至4 h时,胶粘剂仍可保持5.20 MPa的剪切强度;350℃受热1～4 h,胶粘剂获得了5.53～4.01 MPa的剪切强度;在400℃分别受热1 h和4 h,胶粘剂的剪切强度降至3.65 MPa和2.54 MPa。随着受热温度的升高、受热时间的延长,胶粘剂的剪切强度呈下降趋势。     

Numerical analysis and experimental tests for long-term strength of adhesive bonds

This paper presents selected numerical analysis results on static strength of adhesive layers which were subjected to long-term loads. The numerical calculations involved modelling the properties of the adhesive layer using the Burger's model. The coefficients of the Burger's model components were determined on the basis of the creep curves of the adhesive. Some results were verified experimentally. It was ascertained that it is possible to examine the problems of long-term strength of adhesive bonds using numerical analysis under certain limitations. Numerical tests should reduce the need for time-consuming experiments. The investigations pointed out adhesive joints long-term strength dependence on creep curves of adhesives. The long-term strength of adhesive joints increased by reinforcement of the adhesive layer with glass fabric.     

汽车用厌氧螺纹锁固胶扭矩的影响因素研究

介绍了汽车用厌氧型螺纹锁固胶的固化机理,并以天山公司产品为例介绍了厌氧型螺纹锁固胶扭矩的影响因素,包括固化温度、固化时间、螺栓表面状态、螺栓类型、间隙等等,并与国外同类产品做了对比试验,