聚四氟乙烯宽幅车削薄板的生产技术

着重介绍用聚四氟乙烯（以下简称PTFE或F4）县浮树脂经模压法加工成圆筒状毛坯,再车削制成厚度0.5-3mm,最大宽度1.5m,长度20-160m的PTFE宽幅薄板的生产技术,用此技术生产的宽幅薄板密度为2.1-2.3g/cm^3,拉伸强度大于或等于18MPa,伸长率大于或等于百分之一百五十,介电强度大于或等于10KV/mm。     

垂直筛板流化床中FCC催化剂的流化性能

以FCC催化剂颗粒研究垂直筛板流化床内构件对气固两相流化性能的影响,考察了板孔气速、颗粒循环量和帽罩开孔比等筛板结构对流化床压降和提升量强度的影响. 结果表明,气固两相总体逆流流动条件下,帽罩内气速达4 m/s,气固高速并流喷射无气泡,两相接触好、返混小,属快速流态化. 由于没有气泡,床层压力波动小,在塔板上颗粒返混小. 垂直筛板压降随板孔气速、帽罩底隙高度增大而增大,随帽罩开孔比、板孔径增大而减小,颗粒提升量大,床层压降大. 提升量强度随板孔气速、帽罩底隙高度、颗粒循环量增加而增大,随帽罩高度与塔节高度比增大而减少,随帽罩筛孔孔径变化存在最大值. 当帽罩开孔比为1.2~2.5、板孔面积与帽罩截面积比为0.42、帽罩底隙高与板孔孔径比为0.36~0.64时帽罩流化性能较好.     

覆膜滤料用聚四氟乙烯微孔膜的制备及其性能研究

针对市场上常用4种SSG范围的聚四氟乙烯(polytetrafluoroethylene,简称PTFE)树脂原料,采用双向拉伸法制备PTFE微孔膜,分析微孔膜性能的差异,并确定最适用于覆膜滤料用PTFE树脂原料.分析了不同分子量PTFE树脂原料的相对标准密度(SSG)、粒径、挤出压力和含水率等参数,采用不同分子量树脂原料来制备PTFE微孔膜,并表征PTFE微孔膜力学、厚度、结晶度、孔径、孔隙率和透气性能.研究表明:SSG的大小会影响PTFE微孔膜的力学性能(最大力、断裂伸长率)和孔结构(孔径、孔隙率),随SSG的增大呈现先上升后下降的趋势,在2.170～2.189范围内达到最优;结晶度与SSG的大小成正相关,而微孔膜透气性能主要与其孔结构有关,与孔径和孔隙率的变化趋势具有一致性.得出结论:PTFE树脂原料SSG分布在2.170～2.189范围时,制备的PTFE微孔膜最适用于覆膜滤料领域.     

工艺参数对微注射成型等规聚丙烯拉伸性能的影响

选用等规聚丙烯为实验材料,基于正交实验设计方法进行微注射成型实验,制备了微注塑拉伸试样,并选取拉伸弹性模量和拉伸屈服应力作为力学性能指标。采用直观分析和方差分析法对拉伸实验的结果进行分析,研究工艺参数对厚度为1.0 mm和0.2 mm试样拉伸性能的影响规律及重要性,并分析了尺度效应对试样力学性能的影响。结果表明,微注塑实验的拉伸弹性模量和拉伸屈服应力都随着试样尺寸的减小而增大,且不同试样尺寸下,各工艺参数对拉伸弹性模量和拉伸屈服应力的影响规律和重要性也不同。对于厚度为1.0 mm的试样,其拉伸弹性模量受保压压力的影响最大,随保压压力增加呈现先增后减的趋势;其屈服应力受保压时间的影响最大,随保压时间增加呈现先增后减的趋势。对于厚度为0.2 mm的试样,拉伸弹性模量和拉伸屈服应力受熔体温度的影响最大,且两者均随着熔体温度的升高而减小。     

聚丙烯拉伸断裂过程中的银纹性能研究

在18℃和26℃两种测试温度下,分别以0.1、0.5、1、5、20和50 mm/min的拉伸速率对无规共聚聚丙烯(PP-R)全切痕拉伸样条进行拉伸测试,以观察PP-R的银纹性能,并对PP-R全切痕拉伸过程中应力-位移曲线、位移-屈服应力曲线和拉伸断面进行了分析。结果表明:PP-R的屈服应力随着拉伸速率的增加而增大,并且随温度的上升而减小;在较低温度和较高拉伸速率时,PP-R的全切痕拉伸断裂可能是由常临界位移控制的银纹断裂;而在较高温时,PP-R的全切痕拉伸断裂过程几乎无常临界应力和常临界位移存在,说明PP-R拉伸断裂前几乎无沿拉伸方向的银纹微纤产生。     

注塑工艺对均聚聚丙烯拉伸性能的影响

采用正交试验研究了保压压力、注射压力、注射速度等注塑工艺参数对均聚聚丙烯S1003和K2760拉伸性能的影响。结果表明:保压压力为90 MPa,注射压力为80 MPa,注射速度为20 mm/s时,S1003的拉伸性能最佳。通过单因素实验对K2760的注塑工艺进行了进一步优化。结果表明:当保压压力为9 MPa,注射压力为40 MPa,注射速度为18 mm/s时,K2760的拉伸性能最佳。通过极差分析法分析了各因素的影响程度:注射速度对S1003的拉伸屈服应力和断裂标称应变影响最大,对K2760的拉伸性能影响不大;注射压力对S1003的拉伸断裂应力和拉伸弹性模量影响最大,对K2760的拉伸屈服应力影响最大;保压压力对K2760的拉伸断裂应力和拉伸弹性模量影响最大,对S1003的拉伸性能影响不大。     

聚四氟乙烯复合微滤膜的制备及性能表征

为解决聚四氟乙烯(PTFE)中空纤维膜大孔缺陷和表面亲水性差的问题,采用亲水性PTFE平板膜作过滤层,PTFE中空纤维膜作支撑层,通过裹缠的方法制备PTFE复合微滤膜。实验中最佳的拉伸倍率为300%～200%,在此拉伸倍率下,PTFE复合膜孔径分布均匀,最可几孔径为0. 35μm,最可几孔径占比为75. 9%,最大孔径小于0. 4μm,孔隙率大于80%,拉伸强度达到了9. 15 MPa,爆破强度大于0. 3 MPa,PTFE复合膜过滤层接触角为70°,纯水通量为1 107 L/(m2·h)。     

城镇燃气管道带压封堵局部应力分析

城镇燃气管道的安全运行是城镇居民安全用气的保障,针对城镇燃气管道泄漏带压封堵产生的局部应力问题,以补板修复方法为例,利用有限元分析软件ANSYS,分析内压、补板厚度和泄漏孔孔径等因素对孔结构受力的影响规律.结果表明:随着内压的增大,管道的边缘随之发生屈服,管道整体随内压呈正线性相关变化.当补口处的补板长度一定时,该位置处的补板厚度与局部应力成负相关,而与承载极限成正相关.对于开孔边缘,孔径的大小对其应力值影响最大,随着孔径的增大,其应力不断增大,直至屈服;同时孔径的大小对于孔板的交界处以及补板的内侧相对来说影响较小.     

PTFE彩色薄膜的成型工艺

本文介绍了PTFE彩色薄膜的成型工艺,包括工艺流程,所用主要设备、工艺条件及产品规格和性能。结果表明,用本文所述的原料、设备及工艺控制条件生产的PTFE彩色薄膜,其性能达到一定要求:半定向膜:宽度60、90mm;厚度0.003～0.1mm;拉伸强度≥30MPa;伸长率≥70%;直流击穿电压强度(kV/mm)>50。不定向膜:宽度60、90mm厚度0.05mm;拉伸强度≥10MPa;伸长率≥100%;直流击穿电压>30kV/mm。     

高回弹低磨损食品级PTFE密封材料研制

以硫酸钡为基本填料制备食品级聚四氟乙烯(PTFE)密封材料,考察硫酸钡含量对PTFE密封材料力学和摩擦磨损性能的影响,然后采用钛铬黄与硫酸钡协同改性PTFE密封材料,研究了协同改性的效果。结果表明,随硫酸钡含量的增加,硫酸钡填充PTFE密封材料的硬度、压缩强度和摩擦系数提高,拉伸强度、断裂伸长率和体积磨损率降低;当硫酸钡质量分数为20%时,随钛铬黄含量的增加,PTFE密封材料的压缩强度略有提高,拉伸强度和断裂伸长率总体上先上升后降低,体积磨损率和安装回弹率降低,对磨损伤宽度略有增加,硬度和摩擦系数基本无变化,当钛铬黄质量分数为2%时,密封材料的拉伸性能最高,安装回弹率在85%左右;当PTFE基体树脂含量相同时,相对于单一硫酸钡填充的密封材料,钛铬黄与硫酸钡协同改性的密封材料的拉伸和压缩性能及安装回弹率较高,而体积磨损率和对磨损伤宽度均较低。将质量分数为2%的钛铬黄与20%的硫酸钡协同改性的PTFE密封材料制成食品用密封产品,经实际生产验证,其使用寿命可达10 000 h。     

In situ small angle X‐ray scattering study on structural evolution of crosslinked polytetrafluoroethylene during deformation

The structural evolution of virgin and crosslinked polytetrafluoroethylene (PTFE) during stretching was studied by in situ synchrotron small‐angle X‐ray scattering (SAXS). Both yield and tensile stress of crosslinked PTFE increased with increasing crosslinking density. During stretching, for virgin PTFE, amorphous chains gradually turned to tensile direction at early stage, perpendicularly arranged lamellar stacks appeared at high strains (>140%). While for crosslinked PTFE, lamellar structure was observed even at lower strains; with increasing irradiation dose, the lamellar structure became obvious and the long period decreased. Four‐point SAXS patterns were observed only in 3000kGy‐dosed PTFE during deformation, which indicated that an alternately tilted lamella arrangement called herringbone structure was formed. Radiation dose induces crosslinked networks formed, which can carry part of local stress during deformation, resulting in the increase of yield and tensile stress. Crosslinking density is an important factor on structural evolution. In addition, a deformation mechanism of different crosslinked PTFE is proposed. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 39883.     

The Ultraviolet Irradiation Modification of PTFE on the Compatible Properties of Clay/EPDM Composite

Clay and ultraviolet irradiation treated PTFE filled clay/EPDM/PTFE composites were prepared. Results show that the tensile strength increase with the irradiation time, and the tribological properties of the ultraviolet irradiation treated PTFE filled clay/EPDM/PTFE composites are superior to those of clay/EPDM/PTFE composites in terms of the crosslink between the reinforcing particle and matrix. This may be due to the nanoscale effects, and the strong interaction force existed between the matrix and the clay interface.     

偶联剂处理对PTFE/纳米TiC复合材料性能的影响

对纳米碳化钛(TiC)填充的聚四氟乙烯(PTFE)复合材料进行力学与摩擦学性能测试,研究纳米TiC质量分数、偶联剂处理对PTFE复合材料力学和摩擦磨损性能的影响,用扫描电子显微镜(SEM)对拉伸断口形貌进行观察,探讨复合材料增强机理.研究结果表明:纳米TiC的填充能提高PTFE复合材料的硬度、拉伸强度和耐磨性,但其冲击强度和减摩性能有所下降;偶联剂处理纳米TiC后,复合材料的拉伸强度、冲击强度、减摩性能有所提高.拉伸断口的微观分析表明:偶联剂处理纳米TiC在PTFE基体中有较好的分散性,与基体界面结合较好.     

聚四氟乙烯改性乳聚丁苯橡胶性能研究

选取聚四氟乙烯(PTFE)分散液,采用乳液共沉法,研究其对乳聚丁苯橡胶(ESBR)性能的影响。结果表明,PTFE分散液的加入,提高了ESBR的耐油性,且其耐油性与PTFE分散液含量基本呈正比关系。此外,共混体系的力学性能也有一定改善。对于丁苯橡胶(SBR)/PTFE体系:共混比为90/10时,硬度增幅最大;在共混比为80/20时,拉伸强度达到最大值。扯断伸长率随着体系PTFE含量的增加,呈递减趋势。综合考虑,当PTFE质量份为10~20时,胶料耐焦烧性好,加工安全性较高,性能最优。     

PTFE-纳米粒子复合材料的制备及性能研究

使用硅烷偶联剂KH560对纳米Si3N4和Al2O3进行了改性,随后将其分别填充到PTFE树脂中制备了PTFE-纳米粒子复合材料,研究了不同KH560含量对复合材料密度、硬度,力学性能及摩擦磨损性能的影响。结果表明,纳米Si3N4经质量分数6%的KH560改性后,填充制备的PTFE复合材料其拉伸强度、断裂伸长率与未经改性纳米Si3N4填充复合材料相比,磨耗量高、硬度低,但密度、摩擦系数等相差不大;纳米Al2O3分别经质量分数4%的KH560改性后,对应复合材料的拉伸强度和断裂伸长率大于未改性纳米Al2O3填充复合材料,但密度、硬度、磨耗量及摩擦系数等相差不大。     

Improvements in tribological properties of polyoxymethylene by aramid short fiber and polytetrafluoroethylene

In order to improve tribological properties of polyoxymethylene (POM), the effects of aramid short fibers (ASF) and polytetrafluoroethylene (PTFE) solid lubricants, as two classes of additives, were studied. The appropriate composites of the polymer and the additives were prepared by melt mixing process. Distribution of additives in the polymer matrix was characterized by scanning electron microscopy (SEM). Mechanical properties in tension such as modulus of elasticity, yield stress, and stress-at-break as well as the fracture energy in impact test were studied to explore friction and wear mechanisms of the composites against a smooth steel surface. Tribological measurements showed that both additives reduce friction and wear of the POM. However, both additives reduced fracture energy of POM in impact test, which dismisses the role of abrasive mechanism of wear under applied conditions. On the other hand, tensile results showed that addition of ASF mechanically reinforces POM, while PTFE degrades mechanical properties of this polymer, especially yield stress. Considering the role of yield stress in the adhesive mechanism of friction and wear, this property was used to define tribological behavior of samples. Since ASF induces mechanical stiffening to POM, increase in yield stress improves tribological properties. However, PTFE introduces transfer films at the interface, thus reduction of yield stress is in favor of tribological properties of this composite. Finally, it is shown that frictional heating and contact temperature rise has a significant degrading effect on wear resistance.     

The Effects of Phenyltrimethoxysilane Coupling Agents on the Properties of PTFE/Silica Composites

A study on PTFE reinforced with SiO₂ was described. This study included the manufactural process of SiO₂-reinforced PTFE and the effects of the content of silane (Z6124) on the properties of the composites material, such as thermal, dielectric properties, tensile strength and morphology, etc. PTFE/silica composites of 60 wt% SiO₂ loaded with a different coupling agent content were mixed by a high-speed dispersion machine and prepared by a two-roll milling machine. Our results show that the sample treated with 3 wt% silane has the highest tensile strength and optimum dielectric properties. Furthermore, the tensile strength and coefficient of thermal expansion (CTE) increase, and the water absorption decreases, with an increasing silane content. These experiments reveal that silane treatment can reduce the overall hydrophilicity of the composites. Finally, predictions on dielectric and CTE properties are discussed. It has been found that experimental values of the dielectric constant agree well with those predicted by the rule of mixture.     

Supercritical CO2 processing and annealing of polytetrafluoroethylene (PTFE) and modified PTFE for enhancement of crystallinity and creep resistance

A method is reported to improve creep resistance in tension for polytetrafluoroethylene (PTFE) and modified PTFE (M-PTFE). PTFE and M-PTFE from different sources were annealed in air, N₂ or supercritical CO₂ (scCO₂) at a range of temperatures, pressures and time intervals. Annealing PTFE in scCO₂ increases crystallinity from 9 to 53%, depending on the material and annealing conditions. No corresponding increase occurs for samples annealed in air or N₂. In comparison to as-received PTFE, significant improvements in tensile creep resistance (18-60%) are observed also dependent upon the material and annealing conditions. For a given temperature and duration, the increase in PTFE tensile creep resistance after annealing in air or N₂ is greater than after annealing in scCO₂ despite the higher crystallinity for post-scCO₂ processed PTFE. Density measurements indicate that the effect of increased crystallinity is counterbalanced by scCO₂-generated microvoids, particularly at higher pressures, leading to smaller creep resistance. In contrast, thermal annealing in air or N₂, which does not significantly change the density or enhance the crystallinity of PTFE or M-PTFE, yields better tensile creep resistance. The detailed morphological origin of improved resistance to tensile creep is unknown, but stress relief by thermal annealing is evident.     

纳米粒子混合填充聚四氟乙烯复合材料的性能

采用模压成型法制备纳米Si3N4或SiC与纳米Al2O3混合填充的聚四氟乙烯(PTFE)复合材料,研究不同质量分数的纳米Si3N4或SiC与5%纳米Al2O3混合填充对PTFE复合材料力学与耐磨性能的影响,利用扫描电子显微镜(SEM)观察复合材料拉伸断面的微观结构,探讨其增强机理.结果表明:纳米SiN4或SiC与Al2O3混合填料均能使PTFE复合材料的硬度和耐磨性提高,且填充Si3N4/Al2O3的PTFE复合材料的硬度、拉伸性能、冲击强度和耐磨性均优于填充SiC/Al2O3的,其中5%Si3N4与Al2O3混合填充的PTFE复合材料有较好的综合性能.微观分析表明:Si3N4/Al2O3在PTFE基体中分散性较好,说明Si3N4与Al2O3具有较好的协同作用.     

纳米SiC粒子的表面处理对PTFE/纳米SiC复合材料的性能影响

对表面处理与未处理纳米SiC填充的聚四氟乙烯(PTFE)复合材料进行力学与摩擦学性能测试,研究了纳米SiC含量和表面处理对复合材料力学和摩擦磨损性能的影响,用扫描电子显微镜对拉伸断面形貌进行观察,探讨了复合材料的增强机理。结果表明,未处理纳米SiC填充PTFE后,其复合材料的硬度和耐磨性均有不同程度的提高;表面处理纳米SiC后,PTFE/纳米SiC复合材料的拉伸强度、冲击强度、减摩性能均比未处理的有所提高;表面处理SiC在PTFE基体中有较好的分散性,与PTFE基体界面的结合较好,未处理纳米SiC在PTFE基体中分散性较差。