硫化1145NR耐有机溶剂及其自然老化行为研究

将硫化天然橡胶（1145NR）分别经乙酸乙酯、环己酮、汽油和丙酮4种有机溶剂浸泡处理后,研究其在自然环境下的老化行为及性能变化规律,并采用傅里叶变换红外光谱（FT-IR）分析溶剂溶物以探究1145NR老化原因。结果表明:经溶剂浸泡后的1145NR发生不同程度的溶胀,质量增加,邵氏硬度和拉伸强度大幅度减小;随着老化时间的推移,经溶剂浸泡过的橡胶拉伸强度加速下降,120 d后橡胶表面出现不同程度的裂纹,其损耗因子（Tan δ）和玻璃化转变温度（T_g）均较未处理的橡胶发生了改变;溶物红外分析表明,溶出成分比较复杂;后期自然老化过程中,4种溶剂浸泡后的橡胶力学性能下降程度依次是环己酮>汽油>乙酸乙酯>丙酮。     

Study of rheological behavior and miscibility of epoxidized natural rubber modified neoprene

The Mooney viscosity, curing rates, vulcanization behavior, and the relationship between molecular motion of epoxidized natural rubber (ENR) and neoprene (CR) blends at different blending ratios have been studied. The experimental results of ENR/CR blends show that the Mooney viscosity decreased gradually. Plasticization was most pronounced at an ENR/CR ratio of 75/25 and is thus the easiest to process. Owing to the ring opening of the epoxy group of ENR, the rate of crosslink formation is much faster than that of CR at higher temperature. The vulcanized rate increased with increasing ENR content. The results indicated that 175 °C and 5 min were the optimum processing conditions for ENR/CR blends. The DMA spectra showed a single damping peak for the ENR/CR blends, which suggests that ENR and CR are miscible. As seen in the Arrhenius plot of frequency against T _g, the activation energy increased with increasing ENR contents. This suggests the existence of interpenetration of these two rubber molecular networks.     

Correlation between free-volume parameters and physical properties of polyethylene-nitrile rubber blend

Positron annihilation lifetime spectroscopy (PALS) was used to study the immiscibility of a polar nitrile rubber (NBR) that had been blended with pure and waste, low- and high-density polyethylene (PE). The effect of the weight percent of the rubber added to the PE was also investigated. It was found that a complicated variation (positive and negative) in both free-volume parameters (τ₃ and I ₃) from the values of the initial polymers forms an immiscible blend. These results are supported by a significant broadening in the free-volume hole size distributions. This has been interpreted in terms of interfacial spaces created between the boundaries of the two phases. Furthermore, a correlation was established between the free-volume parameters (τ₃ and I ₃) and the electrical and mechanical properties of the before mentioned polymer blends as a function of the weight percent of waste PE.     

Surface modification of natural rubber by TiO2 film

Titanium dioxide (TiO₂) layer has been successfully formed on a natural rubber (NR) substrate through liquid phase deposition (LPD) method. Thin SiO₂ layer serving as intermediate layer between TiO₂ and NR, was produced through vapor-phase chemisorption followed by UV/ozone treatment. The stepwise modification process was monitored by FT-IR spectroscopy, water contact angles and scanning electron microscopy (SEM) measurements. The formed TiO₂ layer was characterized by UV-visible spectra, XRD, and EDX spectra, and it demonstrates photocatalytic and photoinduced hydrophilic conversion properties. Its possible application as the anti-aging layer of NR also has been tested and gained some promising results.     

The influence of aging treatments on sulfide stress corrosion cracking of PH 13-8 Mo steel welds

Slow displacement rate tensile tests were carried out to study sulfide stress corrosion cracking (SSCC) of PH 13-8 Mo stainless steel welds in a saturated H₂S solution. The welds aged in the temperature range of 482-593 °C were susceptible to SSCC; the fracture surfaces revealed mainly quasi-cleavage fractures after notched tensile tests. However, the SSCC susceptibility in terms of the percentage loss of the notched tensile strength (NTS) of the welds was dependent on the aging treatment. The SSCC resistance and the austenite content of the welds increased with the aging temperatures. The presence of greater amounts of austenite, mainly reverted austenite, in the W1100 specimen (the weld aged at 1100 °F or 593 °C) than that in other aged specimens could account for its lower hardness and better SSCC resistance. On the other hand, the AW (as-welded) specimen containing a small amount of retained austenite films in a soft matrix exhibited a slightly improved SSCC resistance than that in the W1100 specimen. The lower hardness of the AW specimen was owing to the absence of fine coherent precipitates, leading to a reduced local stress and an enlarged plastic zone located in front of the notch in the test. With lower hardness, the local stress would also be lower and less likely to exceed some critical stress for failure in the saturated H₂S solution. For the aged specimens, the hardness/strength level and the amount of reverted austenite were the important factors that affect SSCC susceptibility.     

天然橡胶/顺丁橡胶共混物疲劳历程的研究

采用扫描电子显微镜、电性能测定和热重法等分析手段，研究了炭黑补强的天然橡胶／顺丁橡胶共混硫化胶的疲劳历程，探索了其内在的疲劳损伤机理。     

Processing and Mechanical Properties of Natural Rubber-ZnFe<Subscript>2</Subscript>O<Subscript>4</Subscript> Nanocomposites

We present preliminary results concerning natural rubber reinforced with nanometric ZnFe₂O₄ obtained from an industrial solid waste. The study investigate the influence of these nanometric ceramic particles on the processing as well as the mechanical properties of the obtained rubber composite, opening the possibility of partial replacement of carbon black and exposing a new potential composite material. The hardness of unfilled and reinforced rubber increased as nanometric ZnFe₂O₄ was increased. Besides, tensile properties of the reinforced rubber were measured, observing once again that as the amount of nanometric ZnFe₂O₄ particles was increased, ultimate strength improved from 2.5 MPa to almost 20 MPa.     

硅橡胶表面老化、改性与修复的研究

主要探讨了硅橡胶表面产生电晕老化的原因和电晕老化的评估方法,并介绍了氢氧化铝(ATH)等无机填料对硅橡胶表面抗电晕老化改性的影响,归纳了硅橡胶表面紫外老化发生的机理以及相应的紫外老化评估手段.另外,讨论了二氧化钛、二氧化铈等光屏蔽剂以及紫外线吸收剂对硅橡胶表面耐紫外辐照老化性能的作用,总结了硅橡胶表面出现热老化的原因、...     

金属—橡胶粘合促进剂硼酰化镍的制备及性能

研究了以碳酸镍、硼酸酯和混合羧酸合成新的金属－橡胶粘合促进剂硼酰化镍的新方法。系统地考察了各种因素对合成硼酰化镍的影响，以2－乙基己酸和硼三丁酯为有机原料合成的硼酰化镍，通过检测，与英国Manobond公司产品680℃比较，二工外光谱数据、300％定伸强度、拉伸强度、硬度和硫化曲线非常接近，而拉断伸长率、热空气老化的粘合性能则前者稍低、实验表明，制备的硼酰化镍可作用金属－橡胶粘合促进剂。     

EFFECTS OF B ON THE MICROSTRUCTURE AND HYDROGEN RESISTANCE PERFORMANCE OF Fe–Ni BASE ALLOY

利用金相显微镜、扫描电镜观察结合力学性能和抗氢性能测试研究了B对Fe--Ni基合金显微组织和抗氢性能的影响. 结果表明: B的加入有效地抑制了时效过程中晶界上大量η(Ni₃Ti) 相的析出, 晶界上仅析出少量碳化物, 从而显著提高了合金的塑性和抗氢性能. 断口观察显示, 对于无B合金, 在由峰值时效到过时效处理的过程中,由于η相的长大, 使合金发生由穿晶到沿晶断裂的转变; 热充氢后, H在η/γ界面的积聚, 促使合金发生大量沿晶断裂,而含B合金在热充氢后仍以穿晶断裂为主.     

Interfacial microstructure and properties of diamond/Cu-<Emphasis Type="Italic">x</Emphasis>Cr composites for electronic packaging applications

Diamond/Cu-xCr composites were fabricated by pressure infiltration process.The thermal conductivities of diamond/Cu-xCr(x = 0.1,0.5,0.8) composites were above 650 W/mK,higher than that of diamond/Cu composites.The tensile strengths ranged from 186 to 225 MPa,and the bonding strengths ranged from 400 to 525 MPa.Influences of Cr element on the thermo-physical properties and interface structures were analyzed.The intermediate layer was confirmed as Cr3C2 and the amount of Cr3C2 increased with the increase of Cr concentration in Cu-xCr alloys.When the Cr concentration was up to 0.5 wt.%,the content of the Cr3C2 layer was constant.As the thickness of the Cr3C2 layer became larger,the composites showed a lower thermal conductivity but higher mechanical properties.The coefficients of thermal expansion(CTE) of diamond/Cu-xCr(x = 0.1,0.5,0.8) composites were in good agreement with the predictions of the Kerner’ model.     

航天器用GD414硅橡胶材料的湿热老化试验与贮存寿命预测

采用加速老化的试验方法对航天器用GD414硅橡胶材料的湿热老化性能进行研究，建立航天器用GD414硅橡胶材料贮存寿命的湿热老化模型，并利用该模型对GD414硅橡胶的贮存寿命进行预测。结果表明:温湿度对GD414硅橡胶材料的力学性能和电气性能影响较大，随着老化时间的延长，拉伸强度和击穿电压总体呈下降趋势；拉伸试样表面颜色逐渐加深，断口形貌没有发生明显的改变；红外光谱测试结果显示，GD414硅橡胶在湿热老化试验过程中没有产生新的官能团；在20 ℃、相对湿度为60%的条件下，GD414硅橡胶材料的贮存寿命为17.1 a。     

Properties of the AK4-1 alloy after additional aging under stress

Conclusions Several relationships were found between the original aging and the mechanical properties of plates and slabs of alloy AK4-1 in tests of the long-term strength, elongation, and fracture toughness after prolonged holding at 135 and 150°C (below the artificial aging temperature) under tensile stress.Under these conditions the naturally aged slabs and also plates and slabs aged 6, 7, and even 12 h at 190–195°C undergo additional aging consisting of additional decomposition of the solid solution, precipitation of hardening phase, and an increase of the density of the precipitates. As the result of this the long-term strength of the less-aged plates and slabs at testing temperatures of 135 and 150°C exceeds that of the plates and slabs aged at 190–195°C for 12 h, although the long-term ductility is considerably lower.Preliminary holding at 135 and 150°C under tensile stress increases _b and _0.2. After holding under stresses of 24 and 22.5 kg/mm² for up to 0.9 of the average time to failure these characteristics remain at their original levels or exceed them. The ductility characteristics ( and ) decrease after holding under stress, particularly for samples aged naturally. The same is true for the fracture toughness and the work of fracture for samples with started cracks. However, with increasing holding time they become almost identical after all aging conditions. The effect of additional aging increases with an increase of the stress during holding.Khar'kov Institute of Mechanization and Electrification of Agriculture. Translated from Metallovedenie i Termicheskaya Obrabotka Metallov, No. 8, pp. 45–50, August, 1969.     

Tensile properties of haynes alloy 230 and inconel 617 after long exposures to LiF-22CaF2 and vacuum at 1093 K

As a part of a study of a space-based thermal energy storage system utilizing the latent heat of fusion of the eutectic salt LiF-20CaF₂ (mole%), the two wrought Ni-base superalloys Haynes alloy 230 and Inconel 617 were subjected to molten salt, its vapor, and vacuum for periods as long as 10,000 h at 1093 K. Following exposure, the microstructures were characterized, and samples from each superalloy were tensile tested between 77 and 1200 K. Neither the structure nor mechanical properties revealed evidence for additional degradation due to exposures to the salt. Although some loss in tensile properties was noted, particularly at 77 K, this reduction could be ascribed to the influence of simple aging at 1093 K.     

时效制度对2099铝锂合金力学和应力腐蚀性能的影响

采用透射电镜,拉伸性能测试和慢应变拉伸等手段研究时效制度对2099铝锂合金微观组织和力学及应力腐蚀性能的影响。研究采用1组T6(175℃/48 h)制度和2组T8制度对试样进行处理。实验发现,T8状态下试样的抗拉强度均高于T6态。同时T8态中双级时效制度(2.5%预变形,120℃/12 h+150℃/48 h)相比于单级时效制度(2.5%预变形,150℃/48 h)具有更优异的综合性能。对2099合金进行应力腐蚀测试,试样并未发生强度损失现象,然而失效却加速。合金经过T8双级时效后,抗拉强度、屈服强度和延伸率分别为590 MPa、570 MPa,9.3%。     

Remarkable reinforcement of natural rubber by deformation-induced crystallization in the presence of organophilic montmorillonite

A remarkable reinforcement of natural rubber (NR) was achieved by adding a low content of organically modified montmorillonite (OMMT). Mechanical tests demonstrated that the most noticeable enhancement in the tensile strength of NR was at a OMMT content of 5 wt.%. In order to gain further insight into the mechanism of reinforcement by OMMT, the deformation-induced crystallization behavior and morphology of NR/OMMT nanocomposites with different OMMT contents were investigated by synchrotron wide angle X-ray diffraction and transmission electron microscopy. The results show that the variation in the degree of strain-induced crystallization is consistent with that of tensile strength. The peak in tensile strength at 5 wt.% OMMT content can be ascribed to the fact that strain-induced crystallization is the essential factor in reinforcement of NR. Further, the nanomorphology of OMMT dispersed in a NR matrix plays a decisive role in the crystallization behavior of NR during deformation. An increase in the exfoliation of OMMT leads to an increase in the promotion of deformation-induced crystallization of NR.     

Microstructural evolution and corrosion behavior of friction stir processed fine-grained AZ80 Mg alloy

Friction stir processing (FSP) and subsequent aging heat treatment were used to modify the microstructure of AZ80 magnesium alloy. The influence of FSP and aging heat treatment on the corrosion behavior was systematically studied by using potentiodynamic polarization, immersion, and slow strain rate tensile tests. The results revealed that FSP led to grain refinement, rapid dissolution of β-phase, and the deflection of c-axis from transverse direction (TD) and processing direction (PD) by approximately 55° and 25°, respectively, improving the static corrosion and stress corrosion cracking (SCC) resistance. The aging heat treatment rendered a little influence on the grain size and slightly affected the grain orientation. The content of β-phase in FSP-5 and FSP-24 samples was 8.1 and 21.8 wt.%, respectively. Static corrosion and SCC resistance of FSP-5 and FSP-24 samples were lower than those of the FSP samples. Compared with FSP-5 sample, the amount of β-phase and the proportion of Al₂O₃ increased in FSP-24 sample, leading to enhanced static corrosion and SCC resistance. SCC behavior was controlled by anodic dissolution, whereas the presence of hydrogen accelerated the SCC.     

Thermal residual stresses in co-continuous composites

The thermal residual stresses in two types of co-continuous composites copper/aluminum oxide (Cu/Al₂O₃) and aluminum/aluminum oxide (Al/Al₂O₃) were measured by neutron diffraction experiments. These stresses were generated during the cooling after high processing temperature. The coefficient of thermal expansion (CTE) mismatch of metal and ceramic phases led to significant amount of thermal stresses. In both the composites, the metallic phase was found to be under tension and aluminum-oxide phase under compression. Even though the magnitude of compressive stress in both the composites was similar; the two metal-phases had very different magnitude of tensile stresses. The difference in volume fraction, CTE, elastic stiffness and plastic flow properties led to this difference. The hydrostatic stresses were found to be predominant in both the phases. Finite element simulations were used to predict the stress distributions inside each phase and at the interfaces. A representative unit cell approach was considered to represent the composite. Concept of effective ΔT was utilized to simulate the thermal stress distribution inside the two phases in the unit cell. This model utilized the neutron diffraction measurements to predict the stress distribution inside each phase and at the interface. The simulations showed that significant amount of tensile stresses develop at the metal–ceramic interfaces.     

Influence of cooling rate after homogenization on microstructure and mechanical properties of aluminum alloy 7050

The influence of cooling rate (0.009?C220 °C/s) after homogenization on the microstructure and mechanical properties of high strength aluminum alloy 7050 was investigated by tensile testing, optical microscope, X-ray diffraction, scanning electron microscope, and transmission electron microscope. A lower cooling rate after homogenization resulted in lower mechanical properties after aging. The drop in strength was significant when the cooling rate was decreased from 0.5 °C/s to 0.1 °C/s. A lower cooling rate gave rise to a larger amount of remnant S(Al₂CuMg) phase and a higher fraction of recrystallization after solution heat treatment. Consequently, the increase in strength after aging due to precipitation hardening and substructure hardening was less significant in the case of slow cooling. This was supposed to be responsible for the lower mechanical properties due to a lower cooling rate after homogenization.     

The effect of thermal cycling on the mechanical properties of sic whisker reinforced magnesium alloy-based composites

The effect of thermal cyclings on mechanical properties at room and some elevated temperatures of SiC whisker-reinforced magnesium-matrix composites produced by squeeze casting and hot extrusion are clarified. Subsequent thermal cycling produces internal stress at the matrix/SiC whisker interfaces causing fatigue. The mechanical properties of composites are more influenced by the low thermal cycling of 298 K— 77 K than the high thermal cycling 673 K—298 K. The high thermal cycling of 673 K—298 K has only a slight affect on such mechanical properties as tensile strength and proof stress at temperatures lower than 473 K. However, at 473 K and 573 K, the thermal cyclings there almost no influence on the mechanical properties of SiC whisker reinforced AE42 alloy-matrix composites.