氟树脂性能与加工应用(续17)

分别叙述了PTFE涂层、PTFE纤维和PTFE浇涛膜的性能和应用,制备原理、方法和工艺.介绍了聚四氟乙烯填充树脂的特性、用途和填充料的种类,分别叙述了PTFE悬浮树脂、PTFE分散树脂和PTFE分散液与填充料的混合工艺、方法,介绍了PTFE填充树脂与弹性体的复合材料.     

推压成型工艺对PTFE初生中空纤维力学性能的影响

聚四氟乙烯(PTFE)初生中空纤维是拉伸制备PTFE中空纤维膜的先驱体,其力学性能直接影响制膜工艺和产品性能。系统考察了推压成型温度、速度和压力条件对PTFE初生纤维力学性能的影响,并通过纤维表面微观结构分析,探究其力学性能变化的内在因素。结果表明,较高的推压成型温度和压力、较低的速度,有利于制备综合力学性能较优的PTFE初生中空纤维;纤维表面树脂初级粒子纤维化是影响其力学性能的内因;相比,推压成型温度和压力变化对树脂粒子纤维化影响较大。当推压成型温度、速度和压力分别控制为50~80℃,9~15 mm/min和38~42MPa时,纤维综合力学性能较好。     

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.     

拒油型聚四氟乙烯微孔薄膜的制备方法

在分散型聚四氟乙烯树脂(PTFE)中混入含氟表面活性剂(FS),采用双向拉伸工艺制备具有较好拒油性能的多微孔薄膜,对薄膜的拒油性能、耐洗性能、力学性能进行测试,并用表面扫描电镜(SEM)观察薄膜微观结构.结果表明:FS能够掺混在PTFE中,经双向拉伸后PTFE形成了网状微孔结构,采用共混法改性后的聚四氟乙烯薄膜具有良好的拒油性能和耐洗性能.     

助剂挤出法制备高强度聚四氟乙烯单丝

将聚四氟乙烯(PTFE)与润滑助剂航空煤油混合后均匀挤出,挤出样条脱除助剂,在低于PTFE熔点的温度下高倍拉伸,后经高温紧张热定型,制备高取向PTFE单纤维;通过拉曼光谱、X射线衍射、差示扫描量热分析等方法研究挤出PTFE拉伸过程中材料微细结构的变化,并对PTFE纤维的性能进行表征.结果表明:PTFE在挤出过程中并不会...     

湿法纺丝制备PTFE纤维的后处理工艺研究

以聚乙烯醇(PVA)为载体采用湿法纺丝制备聚四氟乙烯(PTFE)/PVA初生纤维,然后进行烧结、拉伸后处理得到PTFE纤维,考察了烧结温度、烧结时间和拉伸倍数对PTFE纤维力学性能的影响,讨论了强酸和强碱对PTFE纤维的腐蚀作用。结果表明:较佳的后处理工艺是烧结温度380℃,烧结时间30 min,拉伸倍数5,制得的PTFE纤维的线密度为14.60 dtex,断裂强度为0.871cN/dtex,断裂伸长率为261.26%,模量为0.525 cN/dtex;PTFE纤维具有优异的耐酸碱腐蚀性能。     

聚四氟乙烯推压制品成型工艺的探讨

介绍了聚四氟乙烯(PTFE)分散树脂推压成型(也称糊膏挤压成型)制品的工艺技术。用该工艺生产的PTFE管,其密度为2.10～2.30g/cm~3,拉伸强度≥25MPa,断裂伸长率≥100％,击穿强度≥18kV/mm。     

聚四氟乙烯拉伸微孔膜的结构与性能

通过挤出、压延和拉伸等工序制备了聚四氟乙烯微孔膜，采用扫描电镜（SEM）分析了微孔膜的微观结构；采用差示扫描量热法（DSC）和广角X衍射（WXRD）表征了拉伸前后聚四氟乙烯结晶度的变化；研究了拉伸温度、拉伸倍率和拉伸速率对微孔膜力学性能的影响。结果表明：聚四氟乙烯微孔膜具有小岛状结点和与拉伸方向平行的微细纤维组成的微观结构；拉伸使PTFE的结晶度显著降低；拉伸工艺是制备微孔膜的关键因素，拉伸温度220～320℃，拉伸倍率为8倍时，微孔膜的最大拉伸强度可达8．5MPa；此外较大的拉伸速率可获得尺寸分布更均匀的微孔。     

聚四氟乙烯/炭黑导电纤维的制备及性能

对炭黑（CB）改性聚四氟乙烯（PTFE）纤维进行了研究描述,将炭黑加入聚四氟乙烯制成纤维,能增加其导电性。试验表明,加入炭黑降低了聚四氟乙烯的储能模量和转化的温度。导电PTFE/CB保持了疏水性的特点。含约5%（质量分数）炭黑的聚四氟乙烯纤维的电阻率约可达到（1.963±0.389）×106Ω.m。扫描电镜结果表明炭黑粒子在聚四氟乙烯微纤维之间的分布相当均匀,而且往往会沿微纤维的方向发展形成面状网络。     

分散聚合工艺制备聚四氟乙烯及其性能研究

应用分散聚合工艺制备聚四氟乙烯(PTFE)分散树脂,研究了乳化剂全氟辛酸铵、稳定剂石蜡、引发剂过硫酸铵以及聚合压力对PTFE分散聚合体系稳定性和PTFE分散树脂性能的影响。结果表明,全氟辛酸铵用量为0.65%时,可确保PTFE分散聚合体系的稳定,得到没有凝聚粒子的PTFE乳液;全氟辛酸铵分步加入的方式降低了PTFE树脂的标准相对密度,提高了拉伸强度和断裂伸长率;石蜡用量为12%时,树脂粘釜现象明显改善;过硫酸铵用量0.020%、聚合压力1.5MPa时,PTFE分散聚合速率达到76g/(L·h),得到标准相对密度2.171、拉伸强度30.6MPa、断裂伸长率469%的PTFE分散树脂。     

A study on the nonuniform deformation of PTFE membrane during its tentering transverse stretching

To understand the deformation of biaxially stretched polytetrafluoroethylene (PTFE) membrane during the tenter frame transverse stretching process, a finite element analysis (FEA) model was established to study the stress and displacement distribution during the transverse stretching. The morphology, pore size, and mechanical properties of the membrane were also characterized. It has been found from the experimental and FEA simulation results that the tentering transverse stretching of PTFE membrane is a nonuniform stretching, the stress and displacement distribution of the PTFE membrane during tentering is nonuniform because of the nonuniform deformation and the ease of yield and plastic deformation originated from the specific structure of the virgin PTFE particles. The nonuniform thickness and pore size distribution across the membrane width resulted from this nonuniform deformation was also characterized and discussed. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Formation mechanism of porous structure in polytetrafluoroethylene (PTFE) porous membrane through mechanical operations

Polymeric porous membranes were prepared from polytetrafluoroethylene (PTFE) fine powder by a series of mechanical operations, such as extrusion, rolling, and stretching. The structure of the prepared porous membrane was well characterized by a spatial periodicity of nodes (domain of agglomerated PTFE particles) and fibril domains. The fibrils were highly oriented in the direction of the stretching operation, providing pores in the polymeric membrane as slit-like voids between adjoining fibrils. The unit size of the periodic structure varied depending on the number averaged molecular weight of PTFE and the stretching conditions, the temperature of stretching, and the stretching rate and stretching ratio. A fibril consisted of several thread-like structures that were easily formed between PTFE particles due to the rolling operation in parallel with their direction. The dependence of the steady tensile stress in the stretching operation on the PTFE molecular weight was much weaker than that presumed for noncrystalline polymeric systems. The activation energy of 11.3 kJ/mol for the growth of fibrils was only several times as large as the thermal energy at the ambient temperature. These results imply that the thread-like structures can easily be pulled out of PTFE particles. This view is in accordance with the previously proposed microstructure in PTFE particles.     

Preparation and properties of porous polytetrafluoroethylene hollow fiber membrane through mechanical operations

Porous polytetrafluoroethylene (PTFE) hollow fiber membranes were prepared from fine powder through a series of mechanical operations including paste extrusion, heat treatment, stretching and sintering. In contrast to conventional process, the heat treatment used in this study was performed at 200°C to 330°C (near the melting point) on the PTFE nascent hollow fiber (precursor of membrane). The results showed that the introduction of heat treatment step effectively improved the mechanical properties of precursors, the ultimate stress and strain increased observably with heat treatment temperature, which was beneficial to subsequently stretching precursors to make them porous. Furthermore, the morphological changes and improvement of membrane properties caused by stretching operation were investigated for porous PTFE hollow fiber membrane having finer pore size and higher porosity. The porous microstructure of nodes interconnected by fibrils varied depending on the stretching conditions, such as the stretching temperature, rate, and ratio. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42696.     

1.33 dtex×38 mm涤纶细特短纤维生产工艺探讨

对生产1.33 dtex×38 mm的涤纶细特短纤维的工艺条件进行了探讨。当原料特性黏度在0.656~0.680 dL/g,纺丝温度在286~288℃,环吹风温在23~27℃,风速在1.4 m/s,风湿在80%,一级拉伸温度控制在33~36℃,二级拉伸温度在73~74℃,一级拉伸倍数在3.16~3.22,二级拉伸倍数在1.10~1.16时,成品丝品质较好。     

机箱托架导轨胶膜粘接新工艺技术

对机箱托架导轨的材料选用聚四氟乙烯软带,粘接采用胶膜粘接工艺进行了全面研究,确定了胶膜粘接热压工艺参数:热压温度130~140℃,时间15~20min,压力3~4kg/cm2。对胶膜粘接工艺(新工艺)和胶黏剂粘接工艺(老工艺)进行了比较,结果表明:选用的胶膜粘接工艺参数合理,在最佳工艺参数条件下,胶膜粘接的剥离强度是胶黏剂粘接强度的1.5倍以上,工艺周期同胶黏剂粘接周期相比,缩短了70%以上,满足机箱托架导轨粘接要求,因此胶膜粘接工艺是托架导轨粘接首选。     

PTFE薄膜横向拉伸变形行为及其有限元分析

采用分步位移加载和弹塑性材料模型,在应力应变曲线及材料基本参数的基础上,对PTFE薄膜横向拉伸过程进行了实验研究和有限元分析,得到了均匀横向拉伸和横向拉伸过程中薄膜的应力和位移变形分布状态及规律。实验和模拟结果表明,由于PTFE薄膜在低应力下易发生塑性变形,在横向拉伸过程中存在明显的应力和位移分布不匀,并导致薄膜在面内发生弓曲变形。研究结果对通过扩幅实现双向拉伸薄膜的非均匀变形控制具有参考价值。     

PTFE纤维制备技术的研究进展

介绍了聚四氟乙烯(PTFE)纤维的结构和物理化学性能;详述了PTFE纤维制备技术,如载体纺丝(湿法纺丝、干法纺丝)、糊料挤出纺丝、熔体纺丝、切割膜裂法等纺丝工艺,比较了各种纺丝工艺的优缺点,载体纺丝法制备PTFE纤维技术较为成熟,可制备线密度较小的纤维;叙述了PTFE纤维在过滤材料、医学材料、密封填料和纺织工业等方面的应用;指出我国PTFE纤维发展的关键是改进及开发新的制备技术,提高PTFE纤维的质量及产量。     

Formation and structure of polytetrafluoroethylene fibrils

Polytetrafluoroethylene (PTFE) is a semi‐crystalline polymer whose fibrils can be easily formed by stretching because of its low tensile activation energy. We prepared two series of PTFE samples with different elongations and degrees of crystallinity, respectively. The morphology analysis of the first series determined that cavities were formed in the PTFE matrix under stretching, and this was a prerequisite for forming fibrils. The barrier between cavities became long and slim under tension, and grew into fibrils finally. It could be found that higher crystallinity is more suitable for forming fibrils. The main part of the fibrils' structure was semi‐crystalline, and the degree of crystallinity could grow under stretching. Besides, the thickness of the lamellae decreased, while the crystalline grain refined at the same time. In the measurement of X‐ray diffraction, it could be found that the lattice plane (108) was more sensitive to stretching, which could rotate to other positions. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 130: 3710–3717, 2013     

PTFE微孔薄膜张力控制用磁粉制动器的应用研究

研究了覆膜滤料用PTFE微孔薄膜生产过程中对横拉部分放卷机的张力控制。建立了张力控制的数学模型,对张力调节原理和张力控制系统进行研究。经过理论分析和应用实例验证,实际激磁电流最大值低于磁粉制动器额定激磁电流,试验型号的磁粉制动器适用于PTFE微孔薄膜生产过程中横拉放卷的张力控制。