填料对氟橡胶热空气老化性能的影响

研究了片层状、颗粒状和金属氧化物等填料填充改性氟橡胶的耐热空气老化性能。结果表明,片层状填料改性的氟橡胶的耐热性能较差;颗粒状填料BaSO4填充改性的氟橡胶具有优良的耐热老化性,300℃老化24h后,氟橡胶力学性能的保持率在50％左右;金属氧化物Fe2O3和SnO2填充改性的氟橡胶具有较好的耐热老化性,300℃老化24h后,仍保持较好的力学性能,其强度分别为9．3MPa和10．3MPa。     

Natural graphite reinforced fluoroelastomer composites: Morphological,mechanical, thermal,dielectric, and solvent transport studies

Fluoroelastomer (FKM) composite embedded with natural graphite (NG) was prepared and its thermal, mechanical, dielectric, and solvent transport properties were explored as a function of NG loading. The morphology of the composites was done by AFM, SEM, and TEM analysis, and XRD provides the structural analysis. The composite with 20 phr of NG content showed the highest tensile properties and thermal stability and was supported by fracture surface SEM analysis. Enhancement in polymer-filler interaction in the composite was further confirmed by the increase in T_g value obtained from DSC analysis. The dielectric permittivity value showed tremendous increment by 30 phr of NG addition with decreased dielectric loss. The resistance to solvent uptake with increase in NG loading by the formation of tortuous pathway is also a clear evidence for the exfoliation of the graphite flakes in the FKM matrix. Better inclusion of NG in FKM matrix efficiently enhanced the thermal, mechanical, dielectric and the transport properties of the composites.     

Rheological properties and thermal transitions in millable polyurethane fluoroelastomers

A series of segmented polyurethane fluoroelastomers based on dimethylol‐terminated perfluoropolyethers (PFPEs), aliphatic diisocyanates and allyl functionality is presented. Depending on the type of diisocyanate monomer used, it was found that quite different prepolymer molecular weights were achieved. Thermal analysis by differential scanning calorimetry showed formation of polyphasic copolymers, either amorphous or semi‐crystalline depending on the monomer structure. Rheological measurements showed that much higher zero‐shear viscosity, a shorter Newtonian plateau and more marked shear thinning behaviour were achieved with polyurethanes based on hexamethylene diisocyanate (HDI) or H₁₂‐MDI monomers. Isothermal viscosity curves were fitted with either three‐ or two‐parameter empirical models, and relaxation times of the structures were estimated at the temperature of 120 °C. Copyright © 2004 Society of Chemical Industry     

碳纳米管表面处理对碳纳米管/氟橡胶复合材料形貌及界面作用的影响

采用溶液浇注法制备了碳蚋米管(CNTs)/氟橡胶纳米复合材料,并对不同表面状态的碳纳米管(原始碳纳米管,酸处理碳蚋米管、CF<,4>等离子体处理碳纳米管)在复合材料中的分散以及碳蚋米管与氟橡胶的界面作用进行了研究.研究结果表明,经CF<,4>等离子体处理后的碳纳米管在氟橡胶中的分散性明显优于混酸处理碳纳米管,激光显微拉...     

Historical Overview of the Army Contributions to Phosphazene Chemistry

The search for new elastomeric materials with a service capability over a wide temperature range and for improved fire-resistant materials formed the basis for the Army interest in polyphosphazenes. The Army Watertown phosphazene program established important working relationships with government and industrial interests, and leading academic scientists. The Watertown laboratory, along with the Army Research Office, supported not only the fundamental research exploring the synthesis and properties of this new class of inorganic polymers, but also the development of polyphosphazenes and phosphazene fluids for the Army, Navy, other government, and commercial applications. The Army Research Laboratory at Watertown was closed in August 1995 and the operations were transferred to Aberdeen Proving Ground, MD.     

Study of intumescent flame-resistant fluoroelastomer

The efficiency of different intumescent flame-retardant (IFR) formulations designed to improve the flame resistance of fluoroelastomer (FKM) composites was studied. The proportion of ammonium polyphosphate (APP) with charring-foaming agent (CFA) in IFR systems, and the addition of synergists zinc borate (ZB) and ketonealdehyde resin (KR120) were investigated to show their effect on flame resistance of FKM. According to flame resistance tests, when the mass ratio of APP to CFA was 4∶1 as well as the loadings of IFR, ZB, KR120 were 83 parts per hundred resin (phr), 13phr, 25phr, respectively, the FKM-KR120/IFR-ZB composites had good synergetic flame resistant effect. TGA data showed that IFR and synergists could obviously lower the maximum weight loss rate of FKM composites and effectively increase the char residue at high temperature. The morphological structures of the composites observed by scanning electron microscopy (SEM) demonstrated that the addition of ZB and KR120 could clearly reduce the cracks in char residue and make the char layer structure more integrated and compact.     

硫化体系对氟橡胶26在硫化氢环境中耐老化性能的影响

以3撑硫化剂、双酚AF／BPP、DCP／TAIC三种硫化体系硫化的氟橡胶26为实验材料,采用美国Cortest公司生产的高压釜测试系统,依照NACE标准对其进行不同温度下硫化氢老化试验,研究了三种硫化体系对氟橡胶26硫化特性、物理性能和耐硫化氢老化性能的影响。结果表明：采用3#硫化剂硫化体系的氟橡胶硫化特性、物理性能相对较好;不同温度下氟橡胶在气相中含硫化氢气体、试样置于液相的腐蚀环境腐蚀后,3#硫化剂硫化体系氟橡胶硬度较高,拉伸性能较好,耐硫化氢性能相对较好,但其体积变化率在不同的温度下均超过20％,很难满足硫化胶条件下的使用。