Denture base materials reinforced with glass cloths: bending property and adhesivity

The reinforcement with glass cloth to a heat-curing base resin was studied using 11 kinds of glass cloths. The bending strength was improved by some glass cloths. The scanning electron microscope observation showed that the adhesivity of the interface between glass fibre and base resin was better for the composite resin containing twill weave than for some others with plain weave. The coating treatment of glass cloth tends to give the base resin a stronger bending strength than those of the composite resins composed of non-treated glass cloths.     

An application of monomer coating for glass-cloth-reinforced acrylic resin

This work was designed to study the application of monomer-coated glass cloths to denture base heat-curing acrylic resin, and the improvement of the bending properties and impact energy in the reinforced resins was attempted by including glass cloth with a twill weave treated by multifunctional monomers. The results, that true adhesion between fibre and resin matrix occurs, support the increases in mechanical properties when treated with the heat-cured monomer. A remarkable increase in impact energy rather than maximum strength as a bending strength was achieved in the reinforced specimen including the twill-woven glass cloth treated due to the multifunctional monomers, and the energy value in the multifunctional-treated specimen was almost twice that in the plain acrylic resin.     

Dental application of various kinds of fibres in heat curing acrylic resin

The effect of the type of fibres on bending behaviour and impact energy in reinforced acrylic resin was examined. Reinforcing materials such as inorganic glass fibre and cloth and organic polyester and Kevlar fibres were coated with a silane coupling treatment, whereas Co-Cr wire was directly used for the reinforcement. After silane coupling treatment each fibre was added to the heat curing base resin, except polyester fibre. It is concluded that the inclusion of glass linear fibre provides an effective improvement on plain acrylic base resin. An additional way to reinforce the resin matrix was given by the combined use of glass and Kevlar fibres.     

Positive direct-mask stereolithography with multiple-layer exposure: layered fabrication with stair step reduction

In this paper, we explain a new stereolithography involving the separate use of liquid photoinitiator and a base resin (photopolymer resin without photoinitiator). First, the base resin is supplied as a layer, and then a mask pattern is drawn onto the surface with photoinitiator by inkjet printing. When the surface is exposed to a UV lamp, only the pattern drawn with the photoinitiator is cured. In this process, the photoinitiator acts as a positive mask. Also, the idea of multiple-layer exposure, which may enable stair step reduction and fabrication time reduction, is introduced. The proposed idea and method are implemented in an experimental stereolithography system and some experiments are conducted using the system. As a result, the effectiveness and feasibility of the idea and method are confirmed.     

Positive direct-mask stereolithography with multiple-layer exposure: layered fabrication with stair step reduction

In this paper, we explain a new stereolithography involving the separate use of liquid photoinitiator and a base resin (photopolymer resin without photoinitiator). First, the base resin is supplied as a layer, and then a mask pattern is drawn onto the surface with photoinitiator by inkjet printing. When the surface is exposed to a UV lamp, only the pattern drawn with the photoinitiator is cured. In this process, the photoinitiator acts as a positive mask. Also, the idea of multiple-layer exposure, which may enable stair step reduction and fabrication time reduction, is introduced. The proposed idea and method are implemented in an experimental stereolithography system and some experiments are conducted using the system. As a result, the effectiveness and feasibility of the idea and method are confirmed.     

Fibre reinforcement in heat-cured,microwave-cured and visible light-cured base resins

The mechanical properties at transverse deflection, bending and impact tests were examined in three fibre reinforced resins including reinforcing materials such as inorganic glass fibre and cloth, organic Kevlar fibre and combined fibres. Both heat-cured and microwave-cured reinforced materials had almost the similar pattern to the changes in the mechanical properties, as compared with those in visible light-cured reinforced resin. Their reinforcing materials increased modulus and impact energy by about two times as compared with the bases. The visible light-cured resin was, however, not effective as a base resin when reinforced with fibres tested here, indicating that the transverse deflection and modulus values in light-cured reinforced resin were similar to that in the plain base resin.     

Dental application of crystalline monomer with urethane linkages: a thermoanalytical study on bis-GMA-based resins

The thermal properties of bis-GMA-based resins containing a synthesized crystalline DME-TDC which was dissolved to bis-GAM/TEGDMA base resin by 10 or 20wt% were examined. Camphorquinone (0.5%) and a reducing agent (0.5%) were added to the base resin before the addition of DME-TDC. A thermoanalytical study using differential thermal analysis (DTA) and differential scanning calorimetry (DSC) showed that thermal change in the DTA and DSC curves depended on the composition of the bis-GMA-based resins. Heat for curing was lowest in 50/50 base resin of 40 wt% bis-GMA/60 wt% TEGDMA, 50/50 and 60/40 base resins in DTA analysis during heating. The addition of DME-TDC to each resin increased heat requirements in 50/50 resin and decreased heat requirements in 40/60 and 60/40 resins. The thermal decomposition of 50/50 bis-GMA-based resin including DME-TDC occurred at a higher temperature than that in 40/60 and 60/40 based resin. The value of activation energy for curing performance was lowest for a DME-TDC including bis-GMA-based resin.     

二烃基五硫化物-三聚氰胺-甲醛树脂微胶囊的制备及其摩擦性能

以硫化脂肪类添加剂二烃基五硫化物(RC2540)为芯材, 三聚氰胺-甲醛树脂(MF树脂)为壁材, 采用原位聚合法合成了RC2540-MF树脂微胶囊。使用红外光谱、 SEM及热重分析(TG)等对其性能进行表征。用四球摩擦副考察了RC2540-MF树脂微胶囊作为聚乙二醇基础液添加剂时的摩擦磨损性能。结果表明: 添加质量分 数3% RC2540-MF树脂微胶囊的聚乙二醇基础液在314 N下摩擦系数可低至0.04, 磨斑直径在314 N(RC2540-MF质量分数5%)下为0.54 mm, 实验载荷则可以提高至1000 N以上。这是由于摩擦力导致RC2540-MF 树脂微胶囊破损, 活性硫化物在摩擦表面的物理、 化学吸附作用和生成的摩擦化学反应膜起到减摩和极压抗磨作用。     

Forming limit evaluation of adhesive bonded sandwich steel sheets and numerical prediction

In the present work, the effect of hardener to resin ratio of epoxy adhesive on the formability of adhesive bonded steel sheets has been studied. Forming limit curve has been evaluated by hemispherical dome tests at predefined strain-paths. They are predicted by finite element simulations using strain mapping method. Cohesive zone model has been used to model the interface between skin and adhesive core. An improvement in the forming limit of sandwich steel sheets has been observed when the hardener to resin ratio is changed from 0.6 : 1 to 1 : 1 due to the improved plasticity of adhesive core layer at 1 : 1 ratio as compared to others. The forming limit of sandwich sheet made at 1 : 1 ratio is equivalent to base steel sheet of same thickness and grade. This shows the potential use of sandwich sheet in place of base steel sheet. The forming limit curve predictions agree well with experimental data for base sheet, while reasonable agreement is observed in case of sandwich sheet. Numerical prediction of interface delamination show insignificant influence of hardener to resin ratio on the onset of delamination and significant effect of strain-paths.     

三聚氰胺和腰果壳油改性酚醛树脂的研究

用腰果壳油和三聚氰胺对酚醛树脂进行改性,可用作刹车片中各种基料的胶粘剂。研究了反应物配比、催化剂用量和反应时间等因素对改性树脂性能的影响,确定了最佳配比和生产工艺,并成功的应用于工业生产。     

基于柔性多体动力学的瓦楞成型系统建模与仿真研究

针对某型号瓦楞机的瓦楞成型系统,基于自主研发的多体动力学求解程序,建立其刚柔耦合动力学模型。其中张力辊、瓦楞辊等主要支撑辊简化为刚体模型;传送带由36自由度绝对节点坐标四边形壳单元划分网格,并考虑其树脂材料的正交各向异性特征;此外,传送带与支撑辊之间的接触采用赫兹碰撞模型和点-面检测方法描述。利用该模型,计算了传送带的偏心位移,传送带表层应力场等动响应。仿真表明:基于绝对节点坐标法建立的瓦楞成型系统的多体动力学模型,可为瓦楞机传送带的动力学行为和控制研究提供一种新的分析方法。     

Dental application of glass cloth to denture: dimensional accuracy in reinforced resins

Duplicate dentures were made from heat-cured (HC) and microwave-cured (MC) bases, and with these bases reinforced with glass cloth. The clearance as a dimensional change in the resins was measured in relation to duplicate gypsum models from a master denture model. The clearance value in resins stored in distilled water at 37°C demonstrated better dimensional accuracy as compared with base resin replicas stored in air at 37°C. When measured at 1 kg load, MC and HC base resins showed a decrease in the clearance value. MC and HC resins reinforced with glass cloth had no significant difference between the values of dimensional accuracy at each site. The MC base and reinforced resins could be useful, comparable with HC acrylic base resin, for dental applications.     

The evaluation of some flexural properties of a denture base resin reinforced with various aesthetic fibers

This study was performed to determine whether some flexural properties of a denture base resin material could be improved through reinforcement with five types of aesthetic fibers at 3% concentration by weight and in 2, 4, and 6 mm length. Five specimens of similar dimensions were prepared for each of the test groups; base resin and the same resin with glass, rayon, polyester, nylon 6 and nylon 6,6 fibers in three different lengths. Flexural properties were evaluated by using a 3-point bending test. A visual examination was also made to determine mode of fracture of the specimens. The incorporation of different fibers in varying lengths had no significant effect on flexural strength of the resin. The specimens reinforced with nylon 6,6 fibers of 6 mm length showed the highest flexural strength. Young’s modulus and maximum load suggests that such reinforcement makes resin resistant to fracture.     

Application of multifunctional base monomer to dental composite resins

Experimental composite resin systems were prepared with visible-light-cured multifunctional matrices to which various amounts of organic composite filler were added. In comparison with the unfilled resins, the filled resin systems were tested for Knoop hardness, compressive and diametral tensile tests, thermal properties, and water sorption. Analyses of the results obtained for the unfilled resins indicate that the increased hardness and mechanical strength were dependent on the multifunctional base monomer. The effective composite resin system was the one that was filled with organic composite filler in the multifunctional comonomer having triethylene glycol dimethacrylate as a diluent monomer.     

耐热型ABS共聚物的研制

用N 苯基马来酰亚胺 (PMI)作耐热改性组分 ,通过不同的方法合成了耐热型ABS(丁二烯 苯乙烯 丙烯腈 )共聚物 ,并且平衡了热性能和机械性能 ,尽可能的使基体树脂与橡胶粒子接枝壳体的化学结构相近 ,获得了一种高品质的耐热型ABS材料。     

水下修复防腐涂料用环氧树脂改性研究

通过合成工艺优化,成功制备了叠氮化环氧树脂E20-N3,并将E51树脂与E20-N3树脂按质量比80∶20共混,得到的树脂清漆固化后的附着力可达16.1 MPa,较未改性树脂清漆的附着力有大幅度提高。     

Thermoanalytical evaluation of visible-light-curved composites

Kinetic analysis of thermogravi metric data in visible-light-cured composite restoratives has been carried out and a comparison was made with that for a conventional chemically-cured composite. The results reveal that the thermal decomposition of polymers as the base resin in the composites rnay be governed by a single process, and the value of activation energy is different in decomposing the base resins thermally. The different values suggest that the kinds of base resins and the catalysts may have an effect on the thermal decomposition.     

Boron removal from aqueous solutions by ion-exchange resin: column sorption-elution studies

A column sorption-elution study was carried out by using a strong base anion-exchange resin (Dowex 2 x 8) for the removal of boron from aqueous solutions. The breakthrough curve was obtained as a function of feed flow rate and the total and breakthrough capacity values of the resin were calculated. The boron on the resin was quantitatively eluted with 0.5M HCl solution at different flow rates. Three consecutive sorption-elution-washing-regeneration-washing cycles were applied to the resin in order to investigate the reusability of the ion-exchange resin. Total capacity values remained almost the same after three sorption-elution-regeneration cycles. The Thomas and the Yoon-Nelson models were applied to experimental data to predict the breakthrough curves and to determine the characteristic column parameters required for process design. The results proved that the models would describe the breakthrough curves well.     

聚苯乙烯－二乙烯基苯共聚物树脂的溶胀干燥动力学

研究了聚苯乙烯－二乙烯基苯交联树脂作为空气清新剂的缓释基材在不同条件下的干燥过程。发现交联树脂具有明显的缓释作用，香料挥发量以指数函数的形式下降，其中以２％ＤＶＢ加入量的交联树脂的缓释作用尤为显著，同时树脂粒径的大小也对香料的挥发速率产生明显的影响。     

一种高性能水性涂料研究

研究了一种水性涂料基础配方，通过实验分析了颜料、填料、树脂、水等基础成分对涂料施工和成膜性能的影响。涂层附着力达1级，硬度达到3H，摩擦系数小于0．2，耐磨性良好，可耐300℃高温5h无变化。