Effect of neutral polymeric bonding agent on tensile mechanical properties and damage evolution of NEPE propellant

Introducing Neutral Polymeric bonding agents(NPBA) into the Nitrate Ester Plasticized Polyether(NEPE)propellant could improve the adhesion between filler/matrix interface, thereby contributing to the development of new generations of the NEPE propellant with better mechanical properties. Therefore,understanding the effects of NPBA on the deformation and damage evolution of the NEPE propellant is fundamental to material design and applications. This paper studies the uniaxial tensile and stress relaxation responses of the NEPE propellant with different amounts of NPBA. The damage evolution in terms of interface debonding is further investigated using a cohesive-zone model(CZM). Experimental results show that the initial modulus and strength of the NEPE propellant increase with the increasing amount of NPBA while the elongation decreases. Meanwhile, the relaxation rate slows down and a higher long-term equilibrium modulus is reached. Experimental and numerical analyses indicate that interface debonding and crack propagation along filler-matrix interface are the dominant damage mechanism for the samples with a low amount of NPBA, while damage localization and crack advancement through the matrix are predominant for the ones with a high amount of NPBA. Finally, crosslinking density tests and simulation results also show that the effect of the bonding agent is interfacial rather than due to the overall crosslinking density change of the binder.

Characterization on Surface and Interfacial Properties of Nitramine Crystal Fillers and Polymeric Bonding Agents

The surface and interfacial properties of polymeric bonding agents and nitramine crystal fillers were studied. The surface free energy and adhesion work of polymeric bonding agents and nitramine fillers were calculated by using Kaeble′s equations. It was observed that the hydroxyl values of neutral polymeric bonding agents (NPBA) correlate well with the polar components of surface free energies. On the basis of the measurements of swelling ratio and initial modulus, the interfacial bonding through highly crosslinked polymeric shell formation around the nitramine particles and generating interfacial reinforcement were rationalized. The application of Tapping Mode AFM (atomic force micro scope) to observing the surface morphology of NPBA reveals that methyl acrylate monomer appears to play a role for aiding the formation of network like structure when nanometer scale images of NPBA are created.

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.

Cytotoxicity of seven recent dentine bonding agents on mouse 3T3 fibroblast cells

Today it is generally accepted that most bonding agents are cytotoxic. In this study the relative cytotoxicity of seven recent dentine bonding agents on mouse 3T3 fibroblast cells were investigated. Materials and Methods. Near-confluent mouse 3T3 fibroblast cells were exposed to Dulbecco Modified Eagle’s Medium containing extractions from the seven different bonding agents. The cell survival rate was then determined using the standard MTT assay. Results. The cell survival rate ranking is: iBond (94%) < Gbond (78%) < Xeno V (71%) < Adper Easy Bond (63%) < Xeno V+ (61%) < Adper Scotchbond SE (33%) < XP Bond (32%). Part A of Adper Scotchbond SE had a survival rate of 35% and part B 38%. These two parts did not differ significantly. Adper Scotchbond SE and XP Bond do not differ significantly. While Xeno V+, Xeno V and Adper Easy Bond do not differ. (p < 5%;Tukey-Kramer Multiple-Comparison Test). Conclusion. All of the tested adhesive bonding agents were cytotoxic with survival rate of 3T3 cells between 94% to 31%. Of the 7 bonding agents tested iBond was found to be only slightly toxic and by far the least toxic. The two bonding agents (XP Bond and Adper Scotchbond SE) containing UDMA plus TEGDMA plus HEMA plus camphorquinone were found to be the most toxic.

Effects of water-aging for 6 months on the durability of a novel antimicrobial and protein-repellent dental bonding agent

Biofilms at the tooth-restoration bonded interface can produce acids and cause recurrent caries. Recurrent caries is a primary reason for restoration failures. The objectives of this study were to synthesize a novel bioactive dental bonding agent containing dimethylaminohexadecyl methacrylate(DMAHDM) and 2-methacryloyloxyethyl phosphorylcholine(MPC) to inhibit biofilm formation at the tooth-restoration margin and to investigate the effects of water-aging for 6 months on the dentin bond strength and protein-repellent and antibacterial durability. A protein-repellent agent(MPC) and antibacterial agent(DMAHDM) were added to a Scotchbond multi-purpose(SBMP) primer and adhesive. Specimens were stored in water at 37 °C for 1, 30, 90, or 180 days(d).At the end of each time period, the dentin bond strength and protein-repellent and antibacterial properties were evaluated. Protein attachment onto resin specimens was measured by the micro-bicinchoninic acid approach. A dental plaque microcosm biofilm model was used to test the biofilm response. The SBMP + MPC + DMAHDM group showed no decline in dentin bond strength after water-aging for 6 months, which was significantly higher than that of the control(P < 0.05). The SBMP + MPC + DMAHDM group had protein adhesion that was only 1/20 of that of the SBMP control(P < 0.05). Incorporation of MPC and DMAHDM into SBMP provided a synergistic effect on biofilm reduction. The antibacterial effect and resistance to protein adsorption exhibited no decrease from 1 to 180 d(P > 0.1). In conclusion, a bonding agent with MPC and DMAHDM achieved a durable dentin bond strength and long-term resistance to proteins and oral bacteria. The novel dental bonding agent is promising for applications in preventive and restorative dentistry to reduce biofilm formation at the tooth-restoration margin.

Investigation of the role of aziridine bonding agents on the aging of the composite solid rocket propellant(CSRP)

The role of bonding agents on the aging characteristics is one of the important research topics.Aging program of the prepared propellant samples was conducting as follows:Five samples,two free of bonding agents,and three containing an aziridine based bonding agents(MAPO,HX-752,MAT4),four samples based on different bonding and curing agents all were aged at 70 ℃.The prepared bonding agent "MAT4" gave remarkable improvements and resulted in highly stable mechanical properties comparing with HX-752 or MAPO.The selected bonding agents family inhibited the rate of decomposition of the propellants during the aging periods and supported the propellant matrix against decomposition at the elevated temperatures.

Properties of SiC Particulate Preforms Based on Different Pore-forming Agents and Bonding Methods for Making SiC/Al Composites

The preforms with high SiC volume fraction （〉50%） were successfully fabricated by two bonding methods. Moreover, the dimensional change, compressive strength, and microstructure of SiC preforms were investigated, and the bonding mechanism among SiC particulates in preforms was also discussed. Results show that, after heating to 1 100 ~C and holding for 2 h, a uniform and interconnected structure in the SiC preforms can be obtained by using starch, stearic acid, and graphite respectively as the pore-forming agents, which benefits the subsequent infiltration by the molten metals. More neck-like-jointing among SiC particulate by using graphite as the pore-forming agent improves the dimensional accuracy and compressive strength of the preform. Besides, the properties of the preforms by the binder bonding are better than those by the oxidation bonding, which is mainly because the mixed neck-like-jointing and binder at high temperature provide effective bonding together.

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.

Anti-proteolytic capacity and bonding durability of proanthocyanidin-biomodified demineralized dentin matrix

Our previous studies showed that biomodification of demineralized dentin collagen with proanthocyanidin（PA） for a clinically practical duration improves the mechanical properties of the dentin matrix and the immediate resin–dentin bond strength. The present study sought to evaluate the ability of PA biomodification to reduce collagenase-induced biodegradation of demineralized dentin matrix and dentin/adhesive interfaces in a clinically relevant manner. The effects of collagenolytic and gelatinolytic activity on PA-biomodified demineralized dentin matrix were analysed by hydroxyproline assay and gelatin zymography. Then, resin-/dentin-bonded specimens were prepared and challenged with bacterial collagenases. Dentin treated with 2% chlorhexidine and untreated dentin were used as a positive and negative control, respectively. Collagen biodegradation, the microtensile bond strengths of bonded specimens and the micromorphologies of the fractured interfaces were assessed. The results revealed that both collagenolytic and gelatinolytic activity on demineralized dentin were notably inhibited in the PA-biomodified groups, irrespective of PA concentration and biomodification duration. When challenged with exogenous collagenases, PA-biomodified bonded specimens exhibited significantly less biodegradation and maintained higher bond strengths than the untreated control. These results suggest that PA biomodification was effective at inhibiting proteolytic activity on demineralized dentin matrix and at stabilizing the adhesive/dentin interface against enzymatic degradation, is a new concept that has the potential to improve bonding durability.

Influence of anodic oxide film structure on adhesive bonding performance of 5754 aluminum alloy

Three types of anodic films(unsealed,hot water sealed and agent sealed)were prepared to study the effects of anodic film structure on the adhesive bonding performance of AA5754 automotive sheets.The morphology of the anodic films was examined by using scanning electron microscope(SEM)and the composition was examined by glow discharge optical emission spectroscopy(GDOES).The adhesive bonding strength and the durability in corrosive environment were investigated by using single lap-hear test and salt spray test(SST),respectively.The results showed that the unsealed sample could provide high initial bonding strength,but the durability was poor in corrosive environment.The hot water sealed sample could provide high durability,but the bonding strength was low.In contrast,the agent sealed sample displayed porous structure at outer layer and partially plugged nano pores structure at inner layer,providing both excellent bonding strength and durability.

Effect of Saliva Contamination on Shear Bond Strength of Orthodontic Brackets When Using a Self-Etch Primer

The effect of saliva contamination on the shear bond strength of orthodontic brackets, at various stages of the bonding procedure using a new self-etch primer was studied. The samples were divided into 4 groups according to 4 different enamel surface conditions: Group A: dry; Group B: saliva contamination before priming; Group C: saliva contamination after priming, and Group D: saliva contamination before and after priming. Stainless steel brackets were bonded in each test group with a light-cured composite resin (TransbondXT 3M). The shear bond strength was determined in the first 30 min after bonding. The analysis of variance indicated that the shear bond strengths of the 4 groups were significantly different (F=11.89, P<0.05). Tukey HSD tests indicated that contamination both before and after the application of the acid-etch primer resulted in a significantly lower (=4.6±1.7 MPa) shear bond strength than either the control group (=8.8±1.9 MPa) or the groups where contamination occurred either before (=7.9±2.0 MPa) or after (=6.9±1.5 MPa) the application of the primer. It was concluded that the new acid-etch primer could maintain adequate shear bond strength if contamination occurred either before or after the application of the primer. On the other hand, contamination both before and after the application of the primer could significantly reduce the shear bond strength of orthodontic brackets.

Super-Bond C&B在口腔临床40年间的应用及特点

背景:Super-Bond C&B自1982年问世以来,经过40年临床病例检验与科研积淀,在口腔多领域各种材料与界面之间的粘接有着广泛的应用场景和市场。目的:就Super-Bond C&B的发展历史、化学成分、粘接机制、临床适应证以及与其他常规树脂水门汀的区别做一综述,以帮助临床医师在口腔各种复杂病例的粘接过程中选择合适的粘接系统。方法:以中文检索词“超级粘接剂、粘接机制;超级粘接剂、化学性质;剪切粘接强度”检索万方数据库、维普数据库及CNKI中国期刊全文数据库,以英文检索词“Super-Bond C&B、MMA/TBB、4-META、Resin、Bond strength、Adhesive、Ceramics”检索PubMed数据库,检索时间范围重点为1962年至2022年7月,最后纳入67篇文献进行综述。结果与结论:Super-Bond C&B作为一种具有良好生物相容性及粘接强度的无填料纯树脂粘接系统,广泛应用于不同口腔修复体的粘固、牙体组织粘接、正畸托槽的粘固、牙周松动牙固定等口腔临床疾病治疗。Super-Bond C&B相比于其他树脂水门汀和其他粘接系统,具有良好的粘接性能、力学性能、生物学相容性、稳定的临床表现以及广泛的临床适用性,因此具有较高的临床应用价值。

Effect of Silane Coupling Agent Concentration on Interfacial Properties of Basalt Fiber Reinforced Composites

The purpose of this study is to investigate the effect of the concentration of silane coupling solution on the tensile strength of basalt fiber and the interfacial properties of basalt fiber reinforced polymer composites.The surface treatment of basalt fibers was carried out using an aqueous alcohol solution method.Basalt fibers were subjected to surface treatment with 3-Methacryloxypropyl trimethoxy silane at 0.5 wt.%,1 wt.%,2 wt.%,4 wt.%and 10 wt.%.The basalt monofilament tensile tests were carried out to investigate the variation in strength with the concentration of the silane coupling agent.The microdroplet test was performed to examine the effect of the concentration of the silane coupling agent on interfacial strength of basalt reinforced polymer composites.The film was formed on the surface of the basalt fiber treated silane coupling agent solution.The tensile strength of basalt fiber increased because the damaged fiber surface was repaired by the firm of silane coupling agent.The firm was effective in not only the surface protection of basalt fiber but also the improvement on the interfacial strength of fiber-matrix interface.However,the surface treatment using the high concentration silane coupling agent solution has an adverse effect on the mechanical properties of the composite materials,because of causing the degradation of the interfacial strength of the composite materials.

蒸压轻质混凝土板专用粘结砂浆的制备与性能研究

采用P·O42.5水泥、粉煤灰、石灰石超细粉、矿粉以及外加剂为原料制备水泥基粘结砂浆。采用正交试验确定水泥基胶凝材料的最优配合比,研究淀粉醚对纤维素醚取代率和膨胀剂对水泥基粘结砂浆的性能影响,并利用XRD和SEM分析水化产物和微观形貌,研究外加剂的作用机理。结果表明,m(水泥)∶m(粉煤灰)∶m(矿粉)∶m(石灰石超细粉)=22∶4∶4∶5时,水泥基胶凝材料的性能最优;淀粉醚适量取代纤维素醚可以增强砂浆保水性,提高砂浆强度,减少收缩;少量膨胀剂可以提高砂浆的早期强度,增加掺量则降低早期强度,提高砂浆后期强度。制备的水泥基粘结砂浆符合JC/T 890—2017《蒸压加气混凝土墙体专用砂浆》的要求。

纳米SiO_(2)界面剂对新旧混凝土界面抗渗性能和微观结构影响研究

采用试验的方法探究了纳米SiO_(2)界面剂对新旧混凝土界面劈裂黏结强度和抗渗性能的影响,其使用形式包括喷洒稀释溶液及作为增强相的砂浆界面剂两种方式,并与整体现浇试件及传统界面凿毛组的抗渗性能进行对比分析.同时,借助扫描电子显微镜(SEM)对不同纳米界面剂的黏结面微观结构进行了探究.最后,从界面强度、抗渗性能和微观机理3方面分析了纳米SiO_(2)界面剂对新旧混凝土界面黏结性能的影响.结果表明:两种纳米SiO_(2)界面剂均能不同程度地提高界面黏结强度及其抗渗性能,其中纳米SiO_(2)砂浆界面剂效果明显优于纳米SiO_(2)溶液组,且两者均存在最优掺量,分别为3.75%和2.5%;随着界面粗糙度的增加,黏结试件渗水高度和相对渗透系数逐渐降低;界面相对渗透系数与劈裂强度呈负相关,且相比于劈裂强度,相对渗透系数对界面缺陷更敏感.微观分析结果表明:纳米SiO_(2)的掺入改变了界面过渡区(ITZ)水化产物数量和C-S-H凝胶形貌,有效抑制了界面孔隙网络贯通,使ITZ微观结构更为致密.

固体推进剂用新型Schiff碱类高效键合剂的合成及性能表征

为提高丁羟四组元推进剂和CL-20/GAP推进剂的力学性能,解决新的推进剂填料基体界面“脱湿”问题,设计合成了新型Schiff碱键合剂;采用傅里叶红外光谱仪、扫描电子显微镜及万能材料拉伸机等对键合剂的键合效果和推进剂的力学性能进行了表征。结果表明,合成的新型Schiff碱键合剂包含键合剂必备官能团且在AP表面存在明显键合,新型Schiff碱键合剂有望取代有毒MAPO,可明显提高丁羟四组元推进剂的力学性能,使丁羟四组元推进剂常温拉伸强度达到0.7 MPa,常温延伸率大于55%,高温延伸率大于50%,低温延伸率大于60%,并可以明显改善丁羟四组元推进剂的工艺性能;在CL-20/GAP推进剂中,新型Schiff碱键合剂可同时提高推进剂的拉伸强度和延伸率。

基于钙镁复合膨胀的无收缩混凝土技术研究与应用

避免管内混凝土收缩脱空是保障钢管混凝土拱桥施工质量且进一步增加跨径的关键措施之一。试验研究了掺入不同配合比的钙镁复合膨胀剂管内混凝土,在恒温和变温条件下的体积变形与力学性能。结果表明:总掺量不变的情况下,20℃恒温时管内混凝土膨胀率随CaO掺量增加而明显增大,模拟实际工程的典型变温条件下,复合膨胀剂中MgO掺量为50%时,管内混凝土最终可残余约22με的膨胀变形,可实现钢管混凝土结构无收缩。外约束作用可提高掺入膨胀剂的管内混凝土抗压强度,不同龄期较自由状态提高了4.5%~7.7%。

Super-bond加金属舌面背板修复下前牙缺失的临床观察

目的:评价Super-Bond粘结剂加金属舌面背板修复下前牙缺失的临床效果。方法:应用Super-Bond粘结剂加铸造金属舌面背板修复下前牙缺失。结果:40例患者随访24个月。有效30例,显效8例,无效2例,有效率为95%。结论:该方法操作简便,牙体预备量小,修复美观效果好,对松动下前牙有固定作用并能有效恢复咀嚼功能。

固位钉对All-Bond2粘结强度的影响

目的 探讨固位钉对All-Bond 2粘结强度的影响。方法 应用All-Bond 2为粘结剂 ,将 15个离体牙随机分为 3组 ,测试加金属固位钉前后光敏复合树脂粘结离体牙表面的剪切粘结力 ,分析固位钉的作用。结果 实验I组 (不加固位钉 )的剪切粘结力为 2 5 .87+ 5 .10Kgf;实验II组和实验III组是将固位钉攻入牙本质内 ,深度分别为 2mm和 3mm ,其剪切粘结力分别为 :2 5 .77+ 3 .72Kgf及 2 6 .2 6 + 3.14Kgf。经统计学处理 ,三组间无显著性差异。结论 复合树脂与牙齿间的粘结强度与加或不加固位钉无相关性 ;

水下自护混凝土与钢筋握裹力试验研究

随着水下自护混凝土技术的推广和应用,其关键工艺参数水下保护剂浓度对水下自护钢筋混凝土结构性能的影响成为关注的热点。基于水下自护技术,在常用工作浓度范围内,对水下自护混凝土的素混凝土力学性能、混凝土与钢筋握裹力、微观孔隙结构开展了试验研究。试验结果表明:在不同水下保护剂浓度下,水下自护素混凝土抗压强度水陆强度比均超过80%;混凝土与钢筋握裹力水陆强度比约在40%~65%,水下保护剂浓度越高,混凝土与钢筋握裹力水陆强度比越低;混凝土基质区域孔隙率和混凝土与钢筋握裹力存在负相关关系;水下保护剂能够有效提升水下自护混凝土的力学性能,但水下保护剂浓度的提升会对混凝土与钢筋握裹力强度造成不利影响。因此,合理选择水下保护剂浓度并增加钢筋用量是提升水下自护钢筋混凝土工程的可靠性的重要举措。