Toughening effect of comonomer on acrylic denture base resin prepared via suspension copolymerization

In this article, three copolymers used as denture base resins were prepared via suspension copolymerization using butyl acrylate (BA), butyl methacrylate (BMA), or methyl acrylate (MA) with methyl methacrylate (MMA), respectively. The homopolymers and copolymers were characterized by ¹³C nuclear magnetic resonance (¹³C NMR). The influence of the three comonomers on the mechanical property was investigated in details and the fracture surfaces of copolymer specimens were examined using scanning electron microscopy (SEM). Meanwhile, the T_g values of three copolymers were examined by differential scanning calorimetry (DSC). The results indicate that, poly(methyl methacrylate) (PMMA) copolymers with BA, BMA, or MA have been successfully prepared via suspension copolymerization. The presence of BA, BMA, or MA could improve the mechanical property especially the impact strength, the toughness of the materials was remarkably improved. The toughening effect of BMA monomer is most significant. When the content of BA is 2 wt %, the flexural strength improves by 51% and the impact strength improves by 81.3%. The T_g values of three copolymers all decrease. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Evaluation of thermal conductivity and esthetic quality of denture base resin composites with acrylic polymer and nanodiamonds

The effect on the thermal conductivity and esthetic quality of acrylic denture base resins due to the addition of surface-carboxylated nanodiamonds (NDs) was evaluated using direct heat flux measurement and spectrophotometric measurement, respectively. The addition of NDs to the denture resin improved its thermal conductivity, which was highly depended on the ND content. The thermal conductivity increased significantly upon the addition of a small amount of NDs, followed by a gradual decrease with increasing ND content. The influence of the ND content on the thermal conductivity of the ND-impregnated resins was explained via experimental results and the theory of phonon scattering. Furthermore, changes in the appearance of the denture base resins caused by ND impregnation were observed to assess their esthetic qualities. The color changes in the resins with low ND contents were found to be minor. Therefore, the improved thermal conductivity and the retention of appearance of the resin can be simultaneously achieved by the addition of a small amount of NDs.     

Adhesion potential of relining materials to polyamide and PMMA-based denture base materials: effect of surface conditioning methods

This study evaluated the bond strength of relining materials to different denture base materials polyamide and polymethylmethacrylate denture base materials after various surface conditioning methods. Denture base resin specimens (N?=?128; n?=?8 per group) (10?×?10?×?2.5?mm³) were fabricated out of injection-moulded thermoplastic polyamide resin (POL) (Deflex) and heat-polymerized polymethylmethacrylate (PMMA, Dura Dent) (HC). The specimens were randomly divided into 4 main groups according to different surface conditioning methods: (a) No conditioning, control (C), (b) grinding with green stone (G), (c) application of primer (V), (d) silica coating with Al₂O₃ particles coated with SiO₂ (Rocatec) (R). Half of the specimens in each group received auto-polymerized hard relining resin (GC, GC Reline Hard) and the other half PMMA based relining resin (SC, Dura Dent). After thermocycling (×5000), the bonded specimens were tested under tensile forces (0.5?mm/min). Data (MPa) were analyzed using Mann–Whitney U and Kruskal–Wallis tests (alpha = 0.05). Bond strength of relining resins were significantly higher to PMMA than to POL, regardless of the conditioning method (p?<?0.05). While R positively affected the bond strength results (p?<?0.05) (4.99?±?1.65–3.27?±?1.31), application V or G did not show significant effect to POL-relining resin adhesion. After R conditioning, bond strength values were significantly higher in HC-GC group (7.48?±?2.32) than POL-GC group (3.27?±?1.31) (p?<?0.05). Adhesion of auto-polymerized relining materials to thermoplastic polyamide or polymethylmethacrylate denture resins could be improved after surface conditioning with silica-coating.     

Contrast on tensile and flexural properties of glass powder reinforced epoxy composites: Pilot study

Epoxy resin was filled with glass powder to optimize the tensile and flexural strength of the composite for structural applications by a research center in the University of Southern Queensland (USQ). To reduce costs, the center wishes to fill as much glass microspheres as possible subject to maintaining sufficient strength of the composites in structural applications. This project varies the percentage by weight of the glass powder in the composites. After casting the composites to the molds, they were cured at ambient conditions for 24 h. They were then postcured in a conventional oven and subjected to tensile and flexural tests. The contribution of the study was that if tensile and flexural properties were the most important factors to be considered in the applications of the composites, the maximum amount of glass powder can be added to the resin will be five (5) percent. It was also found that the fractured surfaces examined under scanning electron microscope were correlated with the tensile and flexural strength It is also hoped that the discussion and results in this work would not only contribute toward the development of glass powder reinforced epoxy composites with better material properties, but also useful for the investigations of tensile and flexural properties in other composites. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

PP/PS-海泡石插层纳米复合材料的流变性能与形态结构

采用苯乙烯乳液聚合法对有机海泡石原位插层,将插层产物聚苯乙烯(PS)-海泡石与聚丙烯(PP)熔融共混制备PP/PS-海泡石插层纳米复合材料.流变测试结果表明:PP/PS-海泡石插层纳米复合材料为典型的假塑性流体,其偏离牛顿流体的程度随PS-海泡石含量增加而增大,表观黏度和零切黏度随着PS-海泡石含量的增加而减小,PS-...     

Improvement of high-temperature energy storage properties of polyimide-based nanocomposites with sandwich structure

The demand for dielectric materials that have high energy and power density properties, and are operational at high temperature has increased with the advancement in new energy technology, high-end microelectronics, and other industries. Pure ceramic and polymer capacitors are not enough to meet the ever increasing energy requirements in a wide range of applications. In this article, we report a sandwich structure nanocomposite film based on polyimide (PI) with high breakdown strength SiO₂/PI as the outer layers and high dielectric constant strontium titanate (SrTiO₃)/PI as the sandwich layer. The results showed that the prepared composites can obtain high energy storage density and low dielectric loss at high temperatures. The composites achieved an energy storage density of 5.5 J cm⁻³ and a dielectric loss of 0.004 at a temperature of 150°C when the filling amount of SrTiO₃ was 0.5 vol% and the filling amount of SiO₂ was 3 vol%. This work shows that the composites are promising dielectrics for applications at high temperature and provides a new idea for high-temperature energy storage devices.     

Improving the flexural strength of porcelain by residual stress in anorthite coating

Flexural strength is an important parameter of domestic ceramics to meet the criteria for mechanized washing, filling, and sealing process in the automatic production line. In this work, the anorthite coating was prepared using calcite, silica, and alumina as raw materials. Taking the temperature with the highest matrix strength as the optimal temperature, the influences of chemical formulation on the phase composition and the coefficient of thermal expansion (CTE) of coatings were investigated. The enhancement effect of the coating with different formulations and surface number and thickness was compared. As a result, the flexural strength of the ordinary domestic ceramic body was improved due to the residual compressive stress in the coating caused by a mismatch of CTE between the coating and the matrix. At the optimal sintering temperature (1280°C), the coating with 20 mass% alumina addition has the best strengthening effect on the body, in which the thickness of the anorthite coating is approximately 50 µm and the flexural strength has increased by 64.6%, from 88 ± 4 to 144 ± 6 MPa.     

有机蒙脱土/聚氨酯/端羟基聚丁二烯液体橡胶纳米复合材料的制备

采用单体插层法制备了有机蒙脱土(OMMT)/聚氨酯(PU)/端羟基聚丁二烯液体橡胶(HTPB)纳米复合材料,通过正交试验研究了OMMT用量、甲苯二异氰酸酯(TDI)用量、加料方法及试验温度对复合材料作为胶黏剂使用时的T型剥离强度的影响.结果表明,OMMT/PU/HTPB复合材料的最佳制备条件为OMMT 3份(质量,下同),TDI18份,采用分步加料方式,在60℃下进行反应.所得复合材料作为胶黏剂使用时其T型剥离强度比未添加OMMT的空白试样高出218.1%.X射线衍射分析表明OMMT在PU/HTPB基质中达到了全剥离的程度.     

Synthesis and characterization of epoxy based nanocomposites

Epoxy‐clay nanocomposites were synthesized to examine the effects of the content and type of different clays on the structure and mechanical properties of the nanocomposites. Diglycidyl ether of bisphenol‐A (epoxy) was reinforced by 0.5–11 wt % natural (Cloisite Na⁺) and organically modified (Cloisite 30B) types of montmorillonite. SEM results showed that as the clay content increased, larger agglomerates of clay were present. Nanocomposites with Cloisite 30B exhibited better dispersion and a lower degree of agglomeration than nanocomposites with Cloisite Na⁺. X‐ray results indicated that in nanocomposites with 3 wt % Cloisite 30B, d‐spacing expanded from 18.4 Å (the initial value of the pure clay) to 38.2 Å. The glass transition temperature increased from 73°C, in the unfilled epoxy resin, to 83.5°C in the nanocomposite with 9 wt % Cloisite 30B. The tensile strength exhibited a maximum at 1 wt % modified clay loading. Addition of 0.5 wt % organically modified clay improved the impact strength of the epoxy resin by 137%; in contrast, addition of 0.5 wt % unmodified clay improved the impact strength by 72%. Tensile modulus increased with increasing clay loading in both types of nanocomposites. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 98: 1081–1086, 2005     

On the structure and morphology of polyvinylidene fluoride-nanoclay nanocomposites

Polyvinylidene fluoride (PVDF)-nanoclay nanocomposites were prepared by both solution casting and co-precipitation methods with the nanoclay loading of 1-6 wt%. The structure and morphology of the nanocomposite were investigated by wide angle X-ray diffraction (WAXD), polarized light microscopy and transmission electron microscopy (TEM) techniques. PVDF phase transformation behavior was investigated using differential scanning calorimetry and in situ thermal WAXD. All the three typical nanoclay morphologies, namely, exfoliated, partially intercalated and phase separated morphologies, were observed in the PVDF-nanoclay nanocomposites prepared by different methods. In solution-cast samples, phase separation and intercalation occurred depending upon the organic modifiers while complete exfoliation of the nanoclays was observed in the co-precipitated nanocomposites. Furthermore, unique parallel orientation of the nanoclay layers and polymer film surface was achieved in solution-cast samples. β-form PVDF was observed in all the nanocomposites regardless of the nanoclay morphology and contents. Both crystallization and melting temperatures of PVDF were increased with the addition of nanoclay, possibly due to the formation of the β-form PVDF.     

环氧树脂／蒙脱土纳米复合材料的制备与性能

重点综述了影响蒙脱土片层在环氧基体中剥离的主要因素。根据环氧树脂／蒙脱土纳米复合材料的结构特点,解释了其力学性能、热性能、耐腐蚀和阻隔性能得到明显改善的原因。     

Dynamic rheology and morphology of polylactide/organic montmorillonite nanocomposites

The effects of organic montmorillonite (OMMT) on the rheological behaviors and phase morphology of polylactide (PLA) were investigated. The rheological behaviors of nanocomposites showed mainly dependence on both temperature and OMMT content. At low OMMT loading (1 wt %), the complex viscosities showed a Newtonian plateau in low frequency region at low temperatures and converted to a shear‐thinning behaviors with increasing temperature. In comparison, at high OMMT loadings (above 5 wt %), strong shear‐thinning behaviors were observed in the full range of frequencies and temperatures. The results demonstrated rheology of PLA/OMMT is highly sensitive to the nanofillers filled materials. A pseudo‐solid‐like behavior at long scale time in the hybrids with OMMT loading was higher than 5 wt %, this response was related to the formation of a network structure across the polymer matrix due to strong interactions of PLA and OMMT that confined the relaxation process of the macromolecules. X‐ray diffraction and transmission electron microscopy indicated the nanocomposites at low OMMT loading were mainly exfoliated and intercalated nanocomposites were gradually formed with increasing OMMT loading. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Relations between structure and property of polyamide 11 nanocomposites based on raw clays elaborated by water‐assisted extrusion

Bio‐based polymers and polymer nanocomposites have known an increasing interest during the past few years. This work is focused on the elaboration and the characterization of bio‐based nanocomposites made from polyamide 11 (PA11) and nonorganomodified montmorillonite. To elaborate these materials an original elaboration process, consisting in injecting water during the extrusion, was used. Results show that thanks to this process, a well exfoliated morphology is obtained for clay contents as high as 10% wt. This was explained on the one hand by the fact that the clay is soluble in water and on the other hand by the fact that water and PA11 are miscible at high pressure and high temperature. Moreover, the morphology analyses have revealed that from 10% wt of clay, the platelets were not totally randomly distributed but they were rather organized at a mesoscopic scale. The obtaining of such clay's dispersion involves an enhancement of thermomechanical properties. For example, for a clay content of 10% wt, the Young's modulus of the material can be doubled and its degradation temperature increased. The role of the elaboration conditions on the morphology and subsequent properties of the nanocomposites are also carefully analyzed. Finally, it has been evidenced that the presence of the filler infers on both the crystalline form induced and the crystallization kinetics. In summary, this study demonstrates that, in the case of PA11 nanocomposites, the water‐assisted injection process leads to the achievement of an exfoliated morphology for clay contents as high as 10% wt that allows to obtain high performance materials and to be free from using organomodified clays. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Influence of chopped strand fibres on the flexural behaviour of a syntactic foam core system

The comparative performance in a three point bending test of syntactic foam comprising epoxy resin and glass microballoons with and without the inclusion of glass fibre in the form of chopped strands is reported. Test samples having a span‐to‐depth ratio of 16:1 were used. The data show that the glass fibre reinforced foam system had a higher strength compared to the unreinforced system. Resorting to light macroscopic and scanning electron microscopic examinations on mechanically tested samples expanded the scope of the work for a structure–property correlation to emerge. © 2000 Society of Chemical Industry     

纳米载银磷酸锆的有机改性及其对3D打印的义齿基托复合材料性能的影响

以γ甲基丙烯酰氧基丙基三甲氧基硅烷偶联剂(MPS)对纳米载银磷酸锆(6S-NP3)进行表面改性,再通过溶液聚合在其表面接枝甲基丙烯酸甲酯(MMA),得到有机改性纳米载银磷酸锆(P-6S-NP3)。将P-6S-NP3与义齿基托树脂混合,通过3D打印制备了义齿基托复合材料。使用傅里叶变换红外光谱仪(FT-IR)和扫描电镜(SEM)对改性前后6S-NP3的结构和形貌进行了表征,考察了6S-NP3和P-6S-NP3在义齿基托复合材料中的分散情况,测试了改性前后6S-NP3的水接触角、粒径分布,以及义齿基托复合材料的机械性能和抑菌性能。结果表明,MPS和MMA已成功接枝到6S-NP3表面,改性后的6S-NP3平均粒径降低,疏水性增强,在义齿基托复合材料中的分散性更好。采用P-6S-NP3制备的义齿基托复合材料的机械性能与对大肠杆菌和金黄色葡萄球菌的抑菌效果明显提高。     

环氧树脂/蒙脱土纳米复合材料的制备和性能

利用插层法制备了环氧树脂/蒙脱土纳米复合材料。X射线衍射分析表明,改性使蒙脱土层间距变大,制备出的环氧树脂/蒙脱土纳米复合材料剥离结构较好。性能测试表明,复合材料的力学性能和热性能均比纯环氧树脂有所提高:拉伸强度提高了70.8%,无缺口冲击强度提高了64.5%,热变形温度提高了17.7℃。     

MCM-41的孔径和添加量对环氧树脂力学性能的影响

以1,3,5三甲苯(TMB)为扩孔剂,水热合成了5种不同孔径(2.7～5.9 nm)的介孔二氧化硅MCM-41粉体,采用溶液共混法制备了MCM-41环氧树脂复合材料,研究了MCM-41孔径和添加质量对复合材料力学性能的影响。结果表明,添加1%最大孔径的MCM-41时,复合材料的力学性能达到最佳,拉伸强度、弯曲强度、弯曲模量分别比纯环氧树脂提高了54.6%、30.1%、68.3%。     

Effect of alkali treatment on the flexural properties of Hildegardia fabric composites

A uniaxial natural fabric of Hildegardia populifolia was treated with 5% sodium hydroxide solution for 1 h, and the resulting changes were analyzed by polarized and scanning electron microscopic techniques. The untreated and treated H. populifolia fabric was reinforced in epoxy and toughened with 10% polycarbonate. The variation of the flexural strength and flexural modulus with different fabric contents and fiber orienrations was studied. The effect of sodium hydroxide and a silane coupling agent on the flexural properties of the composite was also studied. It was observed that the flexural properties increased on alkali treatment and when the coupling agent was used. The morphology of the cryogenically fractured surfaces indicated good bonding between the matrix and the reinforcement when a coupling agent was used. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 1297–1302, 2006     

1-甲酰基苯并三唑席夫碱的合成及荧光性能

以苯并三唑、甲醛、伯胺为原料,合成了3种新的1-甲酰基苯并三唑席夫碱,分别简称为FBTTS、FBTSC和FBTAP。其最佳反应条件是以TBAB为相转移催化剂,三氯甲烷作溶剂,反应温度控制在50~55℃。通过IR、元素分析等检测手段,确证了3种新席夫碱的相应结构,并对其荧光性能进行了初步测试。     

Effect of different preparation routes on the structure and properties of rigid polyurethane‐layered silicate nanocomposites

To identify the effect of reactive preparation on the structure and properties of rigid polyurethane (PU)‐layered silicate nanocomposite, a range of nanocomposites were prepared by combining the various precursors in different sequences. The morphology of the samples was characterized by XRD and TEM. Tensile properties and dynamic mechanical thermal properties were measured. The reactions between the layered silicates and PU precursors were monitored via FTIR to gain an understanding of the participation of nanofiller in the polymerization reaction, and the impact of this on system stoichiometry. The XRD and TEM results provided evidence that morphology can differ significantly if different synthesis methods are used. However, the mechanical properties are dominated by the stoichiometry imbalance induced by the addition of the layered silicates. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 2894–2903, 2006