Mechanical and tribological properties of PA66/PPS blend. II. Filled with PTFE

The mechanical and tribological properties of 70 vol % PA66/30 vol % PPS blend filled with different content of polytetrafluoroethylene (PTFE) were studied in this paper. It was found that the addition of PTFE impairs the mechanical properties of PA66/PPS blend, but greatly increases the wear resistance and decreases the friction coefficient. When PTFE content exceeds 20 vol %, the friction coefficient of composite is minimum (0.15) and lower than that of pure PTFE under the same conditions (0.22). The lowest wear volume (0.44 mm³) is obtained with PA66/PPS/30 vol % PTFE composite, which decreased by 91% compared with unfilled PA66/PPS blend (4.99 mm³). The topography of transfer film and the elemental distribution were investigated by Scanning Electron Microscopy (SEM) and Energy Dispersive Spectrometer (EDS), respectively. Because of the characteristic crystalline structure, PTFE preferentially transferred to the steel ring surface and formed a thin, uniform and firmly adhered transfer layer, which reduced the ability of PA66/PPS blend to transfer and prevent the adhesion between the sample and the couterface. In addition, the superior lubrication of PTFE inhibited the frictional heat melting during sliding. All these aspects are close related to the friction and wear behavior of PA66/PPS/PTFE composite. Upon the addition of PTFE, thermal control of friction regime is not applicable to the PA66/PPS blend. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 969–977, 2006     

γ‐Irradiated poly(tetrafluoroethylene) particle‐filled low‐density polyethylene. I. Effect of silane coupling agents on mechanical,thermal, and morphological properties

Poly(tetrafluoroethylene) (PTFE) scraps were recovered as a filler material for low‐density polyethylene (LDPE) after they were degraded by Co‐60 γ‐rays under atmospheric conditions to make small‐size powder. The powder PTFE, which was called secondary PTFE (2°‐PTFE), was melt mixed with LDPE and then extruded to obtain 200 µm films. The mechanical and thermal properties and also the morphology of the fractured surface of these 2°‐PTFE–filled LDPE were studied. It was found that the addition of 2°‐PTFE resulted in thermofilm property of LDPE but it slightly decreased the thermal oxidative temperature of LDPE. The tensile strength and ultimate elongation of LDPE were found to decrease with the addition of 2°‐PTFE. However, when it is compared to the addition of virgin PTFE into LDPE, 2°‐PTFE shows better mechanical properties due to the presence of oxy groups which are capable of interacting with the main matrix. A further improvement in mechanical properties was achieved by silane coupling agent treatment of 2°‐PTFE. Silane coupling agents were found to enhance the interfacial adhesion between 2°‐PTFE and LDPE. The study on the fractured surfaces by scanning electron microscope revealed this adhesion between these two polymers. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 74: 866–876, 1999     

Emulsifier-free emulsion polymerization of tetrafluoroethylene by radiation. IV. Effects of additives on polymer molecular weight

Poly(tetrafluoroethylene) (PTFE) of high molecular weight, 4.5 × 10⁷, was incidentally obtained at earlier study of an emulsifier-free emulsion polymerization of tetrafluoroethylene by radiation. In order to clarify this phenomenon, the effects of additives, in particular radical scavengers, on the molecular weight of PTFE and its polymerization behavior were studied. It was found that the molecular weight of PTFE is increased by the addition of hydroquinone, benzoquinone, α-pinene, dl-limonene, and ethylenediamine but is decreased by oxygen and triethylamine. A PTFE latex with molecular weight higher than 2 × 10⁷ was obtained in the presence of hydroquinone. It is concluded that additives such as hydroquinone and benzoquinone, which rapidly scavenge the primary radicals (OH·, H·, and e_aq^?) in the aqueous phase but not the growing polymer radicals in PTFE particles, are most effective in increasing the molecular weight.     

The effect of PTFE on the friction and wear behavior of polymers in rolling-sliding contact

The effect of PTFE on the tribological behavior of polymers in rolling sliding contact has been investigated. The two most widely used polymers — nylon 66 and polyacetal—were used as the base material. Tests were conducted over a wide range of running conditions using a twin disc rolling-sliding test rig for both the unfilled materials and for the base materials filled with 20 wt% PTFE. The experimental results showed that the friction and wear performance of the PTFE filled polymers was superior to that of the unfilled polymers. In addition the surface cracking that was found in unfilled PA66 and was thought to be responsible for premature fracture of components such as gear teeth was suppressed by the PTFE. It is suggested that a combination of high surface temperature and high surface tensile stress, produced by friction, is required to initiate these cracks and that PTFE, by reducing friction, inhibits crack formation.     

纳米Al2O3改性聚四氟乙烯力学性能的研究

通过压制和烧结 ,制备了纳米Al2 O3 改性聚四氟乙烯 (PTFE) ,并研究了改性PTFE的物理机械性能。结果表明 :纳米Al2 O3 粒子对PTFE有显著的增强作用 ,提高了复合材料的拉伸强度和硬度 ;降低了摩擦系数 ,但也使复合材料的断裂伸长率降低     

Adhesion to Sodium Naphthalenide Treated Fluoropolymers. Part II. Effects of Treatment Conditions and Fluoropolymer Structure

Films of polytetrafluoroethylene (PTFE) and perfluorinated copolymers (PFA and FEP), with a range of fabrication histories, were exposed to sodium naphthalenide (Na/naphth) etchant so as to defluorinate the surface for improved wettability, and hence adhesion. The depth of defluorination was measured gravimetrically and the nature of the chemical functionalities determined spectroscopically. For smooth films, the fluoropolymer type and crystallinity had little effect on the defluorination process. Surface area was the major variable affecting defluorination rate, although the presence of surface defects and deformation in skived films also increased the rate of defluorination. For all but the skived PTFE, there was little change in surface texture either after defluorination or subsequent stripping of the defluorinated layer by an acid etch. Acid stripping of the defluorinated layer on skived PTFE left a porous surface texture. The chemical nature of the surface could be changed by modifying the post-etch treatment of the specimen, for example by modifying the rinse procedure and the storage history of the specimen before the adhesive bond is made.     

Reactive polytetrafluoroethylene/polyamide compounds. I. Characterization of the compound morphology with respect to the functionality of the polytetrafluoroethylene component by microscopic and differential scanning calorimetry studies

Compounds of electron‐beam‐irradiated polytetrafluoroethylene (PTFE) and polyamide (PA) were produced by reactive extrusion. During extrusion, both a breakdown process of the PTFE agglomerates and a chemical reaction between PTFE and PA took place. The morphology of the compounds was characterized with differential scanning calorimetry using fractionated crystallization, with atomic force microscopy and scanning electron microscopy, and with dynamic light scattering. The particle size of the dispersed PTFE phase decreased as the irradiation dose increased. A simple theoretical model of the breakdown process of PTFE agglomerates was made for the discussion of the development of the observed degree of dispersion. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 98: 1308–1316, 2005     

除尘用过滤材料阻燃性能的研究

在容易发生火灾事故的袋式除尘场所,滤料的阻燃性能是一个重要的指标。本文采用垂直燃烧法和极限氧指数法分别对国产聚苯硫醚针刺毡、聚酯纤维针刺毡、聚酰亚胺纤维针刺毡、聚四氟乙烯针刺毡、国产聚苯硫醚与聚四氟乙烯混纺针刺毡、经聚四氟乙烯乳液处理的进口聚苯硫醚针刺毡和经聚四氟乙烯乳液处理的国产和进口的聚苯硫醚各占50%的针刺毡滤料做了系统性实验。结果表明聚酯纤维滤料的阻燃性较差,不符合阻燃标准;聚四氟乙烯滤料的阻燃性能最强,滤料经混纺PTFE纤维或者PTFE浸渍后处理能提升其阻燃能力。     

Part II. Properties of the grafted and sulfonated membranes

The physical and chemical properties of polystyrene grafted and sulfonated polytetrafluoroethylene (PTFE‐graft‐PSSA) membranes prepared by radiation‐induced grafting of styrene onto commercial PTFE films using simultaneous irradiation technique followed by a sulfonation reaction are evaluated. The investigated properties include water uptake, ion exchange capacity, hydration number and ionic conductivity. All properties are correlated with the amount of grafted polystyrene (degree of grafting). The thermal stability of the membrane evaluated by thermal gravimetric analysis (TGA) is compared with that of original and grafted PTFE films. The membrane surface structural properties are analysed by electron spectroscopy for chemical analysis (ESCA). Membranes having degrees of grafting of 18 % and above show a good combination of physical and chemical properties that allow them to be proposed for use as proton conducting membranes, provided that they have sufficient chemical and mechanical stability. © 2000 Society of Chemical Industry     

硅灰石与石墨对聚四氟乙烯摩擦磨损性能的影响

以针状的硅灰石和鳞片石墨为填料,采用冷压—烧结工艺制备了不同填料含量的聚四氟乙烯（PTFE）复合材料,考察了复合材料的摩擦磨损性能,并利用扫描电子显微镜对磨痕和转移膜进行了分析。结果表明,单独填充硅灰石和石墨时,PTFE的磨损率都会随填料含量的增加而降低,硅灰石的作用要强于石墨;但硅灰石会使PTFE的摩擦因数明显增大,而石墨会使PTFE的摩擦因数降低;2种填料提升PTFE耐磨性的作用机理不同,硅灰石在摩擦过程中会在滑动界面区域上逐渐堆积,起到优先承担载荷的作用;而石墨在摩擦过程中会发生片层的滑移与剥离,有助于转移膜的形成;适量的硅灰石（含量为20 %,质量分数,下同）与石墨（含量为5 %或10 %）复合填充能产生协同效应,使PTFE的磨损率进一步降低,耐磨性比未填充的PTFE提高200倍。     

Friction and wear characteristics of copper and its compound-filled PTFE composites under oil-lubricated conditions

Four kinds of polytetrafluoroethylene (PTFE)-based composites, such as pure PTFE, PTFE + 30(v)%Cu, PTFE + 30(v)%Cu₂O, and PTFE + 30(v)%CuS composite, were prepared. Then the friction and wear properties of the PTFE composites filled with Cu, Cu₂O, or CuS sliding against GCr15-bearing steel under both dry and liquid paraffin-lubricated conditions were studied by using an MHK-500 ring-block wear tester. Finally, the worn surfaces and the transfer films of these PTFE composites formed on the surface of GCr15-bearing steel were investigated by using a scanning electron microscope (SEM) and an optical microscope, respectively. Experimental results show that the antiwear properties of these PTFE composites can be greatly improved by filling Cu, Cu₂O, or CuS to PTFE, and the wear of these PTFE composites can be decreased by two orders of magnitude compared to that of pure PTFE under dry friction conditions. Meanwhile, CuS increases the friction coefficient of the PTFE composite, but Cu and Cu₂O reduce the friction coefficients of the PTFE composites. However, the friction and wear properties of Cu, Cu₂O, or CuS-filled PTFE composites can be greatly improved by lubrication with liquid paraffin. The friction coefficients of these PTFE composites can be decreased by one order of magnitude compared to those under dry friction conditions, while the wear of these PTFE composites can be decreased by one to two orders of magnitude. The PTFE + 30(v)%Cu composite exhibits excellent friction and wear-reducing properties under higher loads in liquid paraffin-lubricated conditions, so the PTFE + 30(v)%Cu composite is much more suitable for application under oil-lubricated conditions in practice. Optical microscope investigation of transfer films shows that Cu, Cu₂O, and CuS enhance the adhesion of the transfer films to the surface of GCr15-bearing steel, so they greatly reduce the wear of the PTFE composites. However, the transfer of the PTFE composites onto the surface of GCr15-bearing steel can be greatly reduced by lubrication with liquid paraffin, but the transfer still takes place. SEM examination of worn surfaces shows that the interaction between liquid paraffin and the PTFE composites, especially the absorption of liquid paraffin into the surface layers of the PTFE composites, creates some cracks on the worn surfaces of Cu₂O or CuS-filled PTFE composites, the creation and development of the cracks reduces the load-carrying capacity of the PTFE composites; this leads to the deterioration of the friction and wear properties of the PTFE composites under higher loads in liquid paraffin lubrication. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 70: 1455–1464, 1998     

The mechanical and tribological properties of PTFE filled with PTFE waste powders

Polytetrafluoroethylene (PTFE) composites filled with PTFE waste offer interesting combination of tribological properties and low cost. PTFE composites waste was mechanically cut and sieved into powders. PTFE composites filled with PTFE waste powders were prepared by compression molding. Friction and wear experiments were carried out in a reciprocating sliding tribotester at a reciprocating frequency of 1.0 Hz, a contact pressure of 5.5 MPa, and a relative humidity of (60 ± 5)%. PTFE materials slid against a 45 carbon steel track. Results showed that a PTFE composite (B) filled with 20 wt % PTFE waste exhibited a coefficient of steady‐state friction slightly higher than that of unfilled PTFE (A), while wear resistance over two orders of magnitude higher than that of unfilled PTFE (A). Another PTFE composite filled with PTFE waste and alumina nanoparticles exhibited the highest wear resistance among the three PTFE materials. This behavior originates from the effective reinforcement of PTFE waste as a filler. It was experimentally confirmed that the low cost recycling of PTFE waste without by‐products is feasible. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 1035–1041, 2007     

PS/PTFE共混体系发泡行为研究

通过熔融共混法制备聚苯乙烯/聚四氟乙烯（PS/PTFE）共混材料,研究了PTFE含量及形态对PS/PTFE共混材料的流变行为以及发泡行为的影响。结果表明,PTFE原位成纤后可以显著改善PS/PTFE共混材料的流变行为,提高PS/PTFE共混材料的可发性;同时PTFE可以作为高效成核剂,促进泡孔成核,提高泡孔密度,降低泡孔尺寸,降低PS/PTFE共混材料的泡沫密度。     

氧系统单向阀中聚四氟乙烯密封环裂纹分析及改进措施研究

介绍了航天发动机氧系统单向阀中聚四氟乙烯(PTFE)密封环的主要成型工艺,采用体式显微镜和扫描电子显微镜分别从宏观形貌和微观形貌分析了PTFE密封环裂纹产生的原因。结果表明,采取PTFE粉料过筛处理和冷压预成型过程增加排气措施制备PTFE制品,有效消除了PTFE制品内部存在的空隙缺陷,改进后PTFE制品的拉伸性能优于未经过筛处理且压制过程无排气措施的PTFE制品,提高了航天产品的品质可靠性,满足了航天领域氧系统单向阀活门产品的使用要求。     

Effect of irradiation modification above melting point on the wear resistance of polytetrafluoroethylene

The cross-linked polytetrafluoroethylene (PTFE) and PTFE/carbon fiber (CF) composites were synthesized through electron beam irradiation in the molten state of PTFE at a controlled temperature of 340 ± 3°C under an inert gas atmosphere for this study. The wear resistance of raw (raw-PTFE), irradiated modified PTFE (RM-PTFE), and CF-reinforced PTFE composites were evaluated using a friction and wear testing machine. The testing was conducted under varying ambient temperatures and dynamic loads. After irradiation, the samples were sectioned into specific sizes for subsequent testing purposes. Under the test conditions of 4.64 MPa positive pressure, 800 rpm speed, and a duration of 300 s at 20°C, the wear amount of PTFE after irradiation modification is significantly reduced from 1.4103 mm to only 0.0233 mm, representing a remarkable reduction by a factor of 60. Similarly, under the test conditions of 4.64 MPa positive pressure, 200 rpm speed, and a duration of 300 s at 20°C, the friction coefficient of PTFE after irradiation modification is substantially decreased from an initial value of 0.13 to just 0.03. The observed improvement can be attributed to the transformation of PTFE's crystalline form into spherulite, accompanied by a significant enhancement in the degree of cross-linking within its molecular chain. The PTFE was supplemented with 10% CF prior to irradiation. Under the test conditions of a positive pressure of 4.64 MPa, rotation speed of 800 rpm, and a duration time of 300 s at 20°C, the wear amount of the composite material measured only 0.0007 mm, representing a reduction by a factor of 2000 compared to that observed for pure PTFE. This improvement can be attributed to the CF filler's high wear resistance properties and the composite's enhanced thermal conductivity.     

Improving hydrophobicity of polyurethane by PTFE incorporation

A simple and facile method was established of incorporating polytetrafluoroethylene (PTFE) on to polyurethane (PU) to improve hydrophobicity of PU by incorporating low levels of fluorine at a molecular level. Nanocomposites were made by preparing PU in the presence of PTFE using seeded miniemulsion polymerization method. The resulting PTFE/PU nanocomposites were characterized by transmission electron microscopy (TEM), Fourier transform infrared (FTIR) spectrometry, differential scanning calorimetric, and thermo gravimetric analysis (TGA). FTIR and TEM indicated changes observed in their structure, size and morphology. The water contact angle of PTFE/PU nanocomposite films increased with increasing amount of PTFE and more on blending with silica nanoparticles but a slight decrease in thermal stabilities of SiO₂/PTFE/PU nanocomposites were noticed. The hydrophobicity imparted by PTFE to PU surface was found to be at its best for 1 : 2 PTFE/PU latex film. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42779.     

Adhesion to Sodium Naphthalenide Treated Fluoropolymers. Part III. Mechanism of Adhesion

Adhesion of fluoropolymers to copper and to other polymers is examined using a range of fluoropolymer types (PTFE, PFA, extruded, skived and cast films), surface modification techniques such as sodium naphthalenide (Na/naphth), acid stripping and lamination to produce surfaces of controlled roughness, and three tests of adhesion (90 degree peel tests, torsional shear tests and stripping of transmission electron microscopy (TEM) replicas). A combination of chemical and physical modification is required to produce good adhesion, with the relative importance of each dependent upon the specific adhesion test used. For relatively smooth-surfaced films, Na/naphth appears to function by increasing both the chemical functionality and the mechanical integrity of a surface layer. Untreated PTFE and PFA show interfacial failure and negligible adhesion. Smooth-surfaced PTFE with superficial surface modification, e.g. after lamination to shiny copper foil or after acid stripping of defluorinated material, often fails by fibrillation of the fluoropolymer surface. For short sodium etch times, adhesion is improved and the failure mode is interfacial. For long etch times, there is a mixed mode of failure. Fibrillation in smooth-surfaced PFA systems was not observed. Adequate adhesive strength in these systems could only be achieved by an increase in the surface roughness. The best adhesion could be achieved by surface roughening, followed by Na/naphth treatment. For such PTFE surfaces plated with copper, peel and shear tests showed a mixed mode of failure, with copper and fluoropolymer found on both failure surfaces by x-ray photoelectron spectroscopy (XPS) and energy dispersive x-ray spectroscopy (EDS). Extensive fibrillation occurred at the locus of failure. Provided chemical modification is adequate to allow wetting, the roughness of the surface dominates the properties of the adhesive bond. Prolonged Na/naphth treatment (e.g. one hour) causes a reduction in peel strengths.     

Friction and wear characteristics of PTFE composites filled with metal oxides under lubrication by oil

Four kinds of polytetrafluoroethylene(PTFE)-based composites, such as pure PTFE, PTFE+30%(v)PbO, PTFE+30%(v)Pb₃O₄, and PTFE+30%(v)Cu₂O composite, were prepared. The friction and wear properties of these metal oxides filled PTFE composites sliding against GCr15 bearing steel in both dry and lubricated conditions were studied by using an MHK-500 ring-block wear tester. Then the worn surfaces of these PTFE composites and the transfer films of these PTFE composites formed on the surface of GCr15 bearing steel were examined by using a Scanning Electron Microscope (SEM) and an Optical Microscope, respectively. Experimental results show that the friction and wear properties of these metal oxide-filled PTFE composites can be greatly improved by liquid paraffin lubrication, and the friction coefficients can be decreased by one order of magnitude. Meanwhile, the interactions between liquid paraffin and metal oxide-filled PTFE composites, especially the absorption of liquid paraffin into the surface layers of these PTFE composites, reduce the mechanical strength and the load-carrying capacity of these metal oxide-filled PTFE composites. This leads to the deterioration of the friction and wear properties of these PTFE composites. Investigations of the frictional surfaces show that Pb₃O₄, Cu₂O, and PbO enhance the adhesion of the transfer films to the surface of GCr15-bearing steel, and thus promote the transfer of the PTFE composites onto the surface of GCr15-bearing steel. Therefore, they greatly reduce the wear of the PTFE composites. However, the transfer of these PTFE composites onto the counterfaces can be greatly reduced by lubrication with liquid paraffin. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 66: 85–93, 1997     

Modification of PTFE latex with P4VP/Surfactant complexes at nanoscale

Polytetrafluoroethylene (PTFE) latex nanoparticles were subjected to modification with Poly (4‐vinylpyridine) (P4VP) by in situ seeded emulsion polymerization technique using regular [sodium dodecyl sulfate (SDS)] and fluorinated [Potassium heptadecafluoro‐1‐octanesulfonate (PFS)]surfactants. The as prepared PTFE‐ (P4VP/surfactant complex) composite latex nanoparticles were characterized for structure, morphology, and thermal properties and a comparison of particles obtained by PFS and SDS was done with different W/W ratios of PTFE and 4VP monomer. The composites have shown a multistep degradation pattern that may be attributed to the P4VP, surfactant and PTFE backbone degradation. Lowering of crystal–crystal transition temperature of PTFE and increase in the glass transition temperature of the P4VP/PFS or SDS complexes was noticed in all the composites suggesting a homogeneous modification. Thus, a simple and easy way to modify PTFE has been reported which could be subsequently complexed with metal salts such that stringent high energy pretreatment methods like plasma, ozone, or irradiation techniques could be avoided. POLYM. ENG. SCI., 55:499–505, 2015. © 2014 Society of Plastics Engineers     

等离子体预处理聚四氟乙烯接枝改性提高粘接性能的研究进展

由于碳氟原子间强烈的结合力和氟原子的保护作用,使聚四氟乙烯(PTFE)具有优异的耐高温性能和极强的化学惰性,故其在苛刻环境中得到广泛应用。为了提高PTFE与其他物质的粘接性能,必须对其进行接枝改性。详细介绍了等离子体预处理PTFE的接枝改性技术,包括改性方法的特点、影响因素、接枝后的表征和应用情况等。