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.

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.

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.

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.

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。

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.

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。

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.

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。

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%。

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。

Synthesis of multifunctional additives for solid propellants:Structure,properties and mechanism

To simplify the composite propellant formulation and address the current issue of the single-functionality present in existing additives,the multi-cyano,amine-based polybutadiene(AEHTPB-CN)was prepared based on AEHTPB by adopting appropriate synthesis strategies.By replacing 10% of HTPB binder in the propellant formulation,it can effectively enhance the interfacial bond strength between the propellant binder matrix and solid fillers(AP(ammonium perchlorate)and RDX(cyclotrimethylene-trinitramine)),the mechanical properties of the HTPB/AP/RDX/Al propellant were superior to blank control propellant with an improvement of 35.4% in tensile strength,62.0% enhancement in elongation at break,and reduce the propellant burn rate by 10.7% with any energy loss.The function mechanism of AEHTPB-CN was systematically elucidated through experiments and computer simulation techniques.The results show that the tertiary amine group in AEHTPB-CN can react with AP to form ammonium ionic bonds,and the hydroxyl and cyano groups can form hydrogen bonding interactions with AP,which enables AEHTPB-CN to be firmly adsorbed on the AP surface through chemical and physical interactions.For RDX,the interfacial bonding effect of AEHTPB-CN is attributed to their ability to form C-H···N≡C weak hydrogen bonding interaction between the cyano group and RDX methylene group.

Interfacial reinforcement of core-shell HMX@energetic polymer composites featuring enhanced thermal and safety performance

The weak interface interaction and solid-solid phase transition have long been a conundrum for 1,3,5,7-tetranitro-1,3,5,7-tetraazacyclooctane(HMX)-based polymer-bonded explosives(PBX).A two-step strategy that involves the pretreatment of HMX to endow—OH groups on the surface via polyalcohol bonding agent modification and in situ coating with nitrate ester-containing polymer,was proposed to address the problem.Two types of energetic polyether—glycidyl azide polymer(GAP)and nitrate modified GAP(GNP)were grafted onto HMX crystal based on isocyanate addition reaction bridged through neutral polymeric bonding agent(NPBA)layer.The morphology and structure of the HMX-based composites were characterized in detail and the core-shell structure was validated.The grafted polymers obviously enhanced the adhesion force between HMX crystals and fluoropolymer(F2314)binder.Due to the interfacial reinforcement among the components,the two HMX-based composites exhibited a remarkable increment of phase transition peak temperature by 10.2°C and 19.6°C with no more than 1.5%shell content,respectively.Furthermore,the impact and friction sensitivity of the composites decreased significantly as a result of the barrier produced by the grafted polymers.These findings will enhance the future prospects for the interface design of energetic composites aiming to solve the weak interface and safety concerns.

带肋钢筋与高强水泥土黏结性能试验研究

【目的】为揭示带肋钢筋和高强水泥土之间的黏结作用机理,利用既有水泥土固化剂配比制作了33个尺寸为150 mm×150 mm×150 mm的立方体拉拔试样。【方法】通过直接拔出试验,分析锚固长度、水泥土保护层厚度和钢筋直径对钢筋水泥土黏结性能的影响。【结果】试验表明:钢筋与水泥土界面黏结强度随着锚固长度的增加而减小,钢筋和水泥土最佳保护层厚度为钢筋直径的2至3倍。【结论】随着钢筋直径的增加,直径大于10 mm后,钢筋直径增长变化对黏结强度影响幅度变小。

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 ;

考虑黏接工艺对云纹干涉钻孔法标定系数基本机理的影响

云纹干涉法与钻孔法相结合的增量钻孔技术被公认为是一种测量内部残余应力的有效方法。该技术中使用的黏接剂在试验过程中起着将应变从结构表面传递到光栅层的关键作用。然而,在求解标定系数时,往往没有考虑黏接剂的影响。基于有限元软件,从黏接剂的材料性质、粘接层的形状和尺寸、粘接层的厚度、钻孔的增量和应变测量方法5个方面考察了黏接剂对标定系数的影响。通过比较有无黏接剂时的标定系数误差,说明了黏接剂的影响。结果表明,忽略黏接剂的影响会显著影响标定系数的精度,将黏接剂从有限元模型中剔除会导致低估标定系数,标定系数的误差超过2.5%,并且与钻孔增量和测量方法有很大关系。此外,黏接剂对薄壁构件的影响比对较厚的试件更显著。

压装PBX用新型有机硅中性聚合物键合剂的合成及应用

以丙烯腈、甲基丙烯酸甲酯、丙烯酸羟乙酯、γ–甲基丙烯酰氧基丙基三甲氧基硅烷为聚合单体,通过自由基溶液聚合反应制备了一系列压装高聚物黏结炸药(PBX)用新型有机硅中性聚合物键合剂(LBA–315)。通过傅里叶变换红外光谱(FTIR)、核磁共振氢谱(1H–NMR)、元素分析、电感耦合等离子体发射光谱仪(ICP–OES)、凝胶渗透色谱(GPC)等确定了产品的结构。分子动力学模拟研究表明,LBA–315键合剂的效果优于传统的中性聚合物键合剂(NPBA)和硅烷偶联剂γ–氨基丙基三乙氧基硅烷(KH550)。X射线光电子能谱(XPS)测试结果表明,LBA–315键合剂对1,3,5–三氨基–2,4,6–三硝基苯(TATB)具有较好的包覆效果。初步应用研究表明,LBA–315键合剂应用于高聚物黏结炸药配方中,使炸药药柱常温抗拉强度和最大延伸率分别提高了89.3%和88.2%。

嵌段型含氟中性聚合物键合剂的合成及应用

以丙烯腈、甲基丙烯酸甲酯、丙烯酸羟乙酯、甲基丙烯酸六氟丁酯为聚合单体,偶氮二异丁腈(AIBN)为引发剂,2–(2–氰基丙基)二硫代苯甲酸酯(CPDB)为链转移剂,通过控制加料顺序,采用可逆加成–断裂链转移(RAFT)活性自由基聚合工艺,一锅法制备了一种嵌段型含氟中性聚合物键合剂(LBA-311键合剂)。用核磁共振氢谱(^(1)H–NMR)、高效液相色谱(HPLC)、元素分析、凝胶渗透色谱(GPC)对所合成的中间产物及产品进行了结构表征与分析。结果表明,所合成的嵌段型含氟中性聚合物键合剂分子量和分子结构可控。与硝胺填料奥克托今(HMX)的界面作用研究表明LBA–311键合剂与HMX之间具有较好的浸润性和黏结强度。初步应用研究表明,LBA–311键合剂应用于叠氮高能固体推进剂配方中,使推进剂药柱常温拉伸强度和最大延伸率分别提高了51.9%和57.3%,具有较好的应用前景。

All—Bond Ⅱ牙本质粘合剂在牙体修复中的应用

作者自1995年5月至9月应用All—Bond Ⅱ粘合剂和复合树脂行牙体修复121例。经一年临床观察All—Bond Ⅱ有较强的粘接力,具有亲水性、能在潮湿的牙面上粘合、符合生理要求,对牙髓刺激较少,但在近髓的窝洞仍需垫底。也可以作为牙本质过敏的脱敏剂。

造孔剂对陶瓷结合剂CBN砂轮组织结构及性能的影响

为研究不同造孔剂对陶瓷结合剂CBN砂轮组织结构及性能的影响,在一定条件下,制备添加不同造孔剂的陶瓷结合剂CBN砂轮试样,对其进行抗折强度、抗冲击强度和气孔率的分析,并对其进行磨削实验。结果表明:同等条件下,添加玻璃空心球的CBN试条气孔率最高,抗折强度和抗冲击强度下降程度较小,兼顾了强度和锋利性的两方面要求;通过磨削实验得到,当加入体积分数约20%的玻璃空心球时,砂轮磨削时的功率最小,同时能得到粗糙度低、表面质量优异的工件。