Surface modification of ultra high modulus polyethylene fibers by an atmospheric pressure plasma jet

To improve their adhesion properties, ultra high modulus polyethylene (UHMPE) fibers were treated by an atmospheric pressure helium plasma jet (APPJ), which was operated at radio frequency (13.56 MHz). The surface properties of the fibers were investigated by X‐ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), and contact angle measurement. The surface dyeability improvement after plasma treatments was investigated using laser scanning confocal microscopy (LSCM). The adhesion strengths of the fibers with epoxy were evaluated by microbond tests. In addition, the influence of operational parameters of the plasma treatment including power input and treatment temperature was studied. XPS analysis showed a significant increase in the surface oxygen content. LSCM results showed that the plasma treatments greatly increased fluorescence dye concentrations on the surface and higher diffusion rate to the fiber center. The tensile strength of UHMPE fiber either remained unchanged or decreased by 10–13.6% after plasma treatment. The contact angle exhibited a characteristic increase in wettability, due to the polar groups introduced by plasma treatment. The microbond test showed that the interfacial shear strengths (IFSS) increase significantly (57–139%) after plasma treatment for all groups and the optimum activation is obtained at 100°C and 5 W power input. SEM analysis showed roughened surfaces after the plasma treatments. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2008     

Influence of absorbed moisture on antifelting property of wool treated with atmospheric pressure plasma

To determine the effect of moisture regain of wool on atmospheric pressure plasma treatment results, wool fibers and fabrics conditioned in 100% relative humidity (RH) and 65% RH were treated by an atmospheric pressure plasma jet with pure helium and helium/oxygen mixed gas, respectively. Scanning electron microscope (SEM) indicated that scales of wool fiber were smoothened for fibers conditioned in the 100% RH. X‐ray photoelectron spectroscopy (XPS) showed that carbon content decreased substantially after the plasma treatment. Surface chemical composition of 100% RH conditioned groups changed more significantly than the 65% RH conditioned groups. Water contact angle decreased significantly after the plasma treatments. In shrinkage test, plasma‐treated wool fabrics preconditioned in 100% RH showed the lowest shrinkage ratios of 5% and 6%, below 8% is required for machine‐washable wool fabrics according to ISO standard. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Effect of Atmospheric Plasma Treatment on Carbon Fiber/Epoxy Interfacial Adhesion

In this work the effect of atmospheric plasma treatment on carbon fiber has been studied. The carbon fibers were treated for 1, 3 and 5 min with a He/O₂ dielectric barrier discharge atmospheric pressure plasma. The fiber surface morphology, surface chemical composition and interfacial shear strength between the carbon fiber and epoxy resin were investigated using atomic force microscopy (AFM), X-ray photoelectron spectroscopy (XPS) and the single fiber composite fragmentation test. Compared to untreated carbon fibers, the plasma treated fiber surfaces exhibited surface morphological and surface composition changes. The fiber surfaces were found to be roughened, the oxygen content on the fiber surfaces increased, and the interfacial shear strength (IFSS) improved after the atmospheric pressure plasma treatment. The fiber strength showed no significant changes after the plasma treatment.     

Aging of hydrophobized surfaces of ramie fibers induced by atmospheric pressure plasma treatment with ethanol pretreatment

In order to investigate hydrophilic recovery of hydrophobic treatment of cellulose fibers, ramie fibers are ethanol-pretreated followed by atmospheric pressure plasma jet (APPJ) treatment using helium as the treatment gas and age for up to 150?days in 20?°C and 65% relative humidity. Scanning electron microscopy shows the fiber surfaces of the ethanol-pretreated?+?APPJ-treated group of freshly prepared, aged for 30?days, and aged for 150?days are covered with polypropylene matrix after fiber pullout tests. X-ray photoelectron spectroscopy shows that the freshly prepared ethanol-pretreated?+?APPJ-treated group has a 31% reduction in atomic ratio of oxygen to carbon and maintains at a similar level even after 150?days of aging. Water contact angle measurement demonstrates that the wettability of fiber surface of the freshly prepared ethanol-pretreated?+?APPJ-treated group drastically decreases and remains at the same lever after aging. Interfacial shear strength test reveals that the interfacial adhesion between PP matrix and ramie fiber for the freshly prepared ethanol-pretreated?+?APPJ-treated group increases 26% and remains substantially higher than that of the control group over time. These results indicate that the ethanol pretreatment followed by APPJ treatment is a permanent surface treatment with negligible aging for at least five months.     

Effects of aging on the adhesive properties of poly(lactic acid) by atmospheric air plasma treatment

The aim of this study was to analyze the durability of a plasma treatment on the surface of poly(lactic acid) (PLA). We used atmospheric‐plasma treatment with air to improve the wettability of PLA by evaluating the aging effect under controlled conditions of relative humidity (RH) and temperature (25% RH and 25°C). We studied the durability of the atmospheric‐plasma treatment by measuring the contact angle, calculating the surface energy, and observing changes in the resistance of the PLA–PLA adhesive bonds. These techniques allowed us to evaluate the hydrophobic recovery phenomenon that the PLA surface suffered as a consequence of the aging process. The results provide the maximum storage time of PLA treated with atmospheric plasma at which the sample retained its good adhesion properties; this time was lower than 3 days under normal atmospheric conditions. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43040.     

Characterization of ramie fiber/soy protein concentrate (SPC) resin interface

Ramie fiber/soy protein concentrate (SPC) polymer (resin) interfacial shear strength (IFSS) was measured using the microbond technique. To characterize the effect of plasticization, SPC resin was mixed with glycerin. Fibers were also treated with ethylene plasma polymer to reduce fiber surface roughness and polar nature to control the IFSS. Fiber surfaces after ethylene plasma polymerization, and fracture surfaces of specimens before and after the microbond tests were characterized using a scanning electron microscope (SEM). Some specimens were also characterized using electron microprobe analyzer (EMPA) to map the residual resin on the fiber surface after the microbond test. Effects of glycerin concentration in SPC and ethylene plasma fiber surface treatment time on the IFSS were investigated. Preparation of SPC resin requires a large amount of water. As expected, during drying of SPC resin, the microdrops shrank significantly. The high IFSS values indicate strong interfacial interaction in the ramie fiber/SPC resin system. This strong interfacial interaction is a result of a highly polar nature of both the ramie fiber and the SPC resin and rough fiber surface. Ethylene plasma polymerization was used to control the IFSS. The plasma polymer imparted a polyethylene-like, non-polar polymer coating on the fiber surface. As a result, the fiber surface became smoother compared to the untreated fiber. Both fiber smoothness and non-polar nature of the coating reduced the ramie fiber/SPC resin IFSS. Plasticization of the SPC resin by glycerin also decreased the adhesion strength of the ramie fibers with the SPC resin. The load-displacement plots for IFSS tests obtained for different resin and fiber combinations indicate different interfacial failure modes.     

Laser scanning confocal microscope characterization of dye diffusion in nylon 6 fibers treated with atmospheric pressure plasmas

The effect of atmospheric pressure plasma treatment on wettability and dyeability of nylon 6 fibers is investigated. The plasma treatments resulted in an average of 10°–20° decrease in the advancing contact angle and 20°–30° decrease in the receding contact angle. An increased dye diffusion rate of nylon 6 fibers was observed using laser scanning confocal microscope (LSCM). Scanning electron microscope confirmed that the fiber surfaces were roughened, and X‐ray photoelectron spectroscopy showed that the polar groups on the fiber surfaces increased after the plasma treatments. As the plasma treatment time increased, a greater degree of etching was achieved and more polar groups such as hydroxyl and carboxyl groups produced on the surfaces of the nylon 6 fibers, leading to a better wettability and thus a better dyeability of the fiber. This study proved that LSCM may be effectively used in detecting the change of dye diffusion rate in nylon fibers treated with plasmas and the mounting medium should have a close refractive index as the fiber to avoid distortion of the fiber cross section image. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Experimental evaluation of the interfacial properties of carbon nanotube coated carbon fiber reinforced hybrid composites

A floating catalyst chemical vapor deposition (CVD) unit was utilized to grow CNT onto the surface of carbon fiber (CF). The surface morphology of the resultant fibers, CNT population density and alignment pattern were found to be depended on the CNT growth temperature, growth time, and atmospheric conditions within the CVD chamber. In contrast to the neat‐CF reinforced composites, improved interfacial shear strength (IFSS) between CF and matrix were obtained when the surface of CF was coated by CNT. Particularly, CF treatment condition for CNT‐coating with 700°C reaction temperature and 30 min reaction time has shown a considerable increase in IFSS approximately of 45% over that of the untreated fiber from which it was processed. The proper justification of fiber–matrix adhesion featured by composite interfacial properties was explained through IFSS. POLYM. COMPOS., 36:1941–1950, 2015. © 2014 Society of Plastics Engineers     

Influence of hygrothermal aging on dimensional stability of thin injection‐molded short glass fiber reinforced PA6 materials

The hygrothermal aging of short glass fiber reinforced polyamide 6 materials (PA6/GF) is a major problem for thin‐walled components used in the automotive sector. In this work, the thickness and glass fiber content of PA6/GF materials were varied and exposed to hygrothermal aging. The temperature and relative humidity were chosen to range from ?40 to 85°C and 10% RH to 85% RH respectively, according to automotive requirements for components in the passenger compartment. For the absorption of moisture, the diffusion behavior could not be generally described by Fick's law. However, the results indicate that the diffusion behavior is dependent on the relative humidity and thickness of the PA6/GF material. The morphology of the test specimen, which is influenced by injection molding, was also found to affect the diffusion behavior. The states of equilibrium for moisture absorption are strongly dependent on the relative humidity during hygrothermal aging and less dependent on the temperature. The maximum absorbed humidity was found at a temperature of 65°C and 85% RH, which was higher than at 85°C and 85% RH because of reduced contrary aging processes, such as postcrystallization. In certain climatic conditions and test specimen thicknesses, there was a characteristic overshoot in the mass change. This behavior could be attributed to a different degree of crystallization and lower glass fiber content. Both moisture absorption and an overshoot of the mass affected the dimensional stability of the test specimens. This effect on dimensional stability could be correlated with the glass fiber orientation. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42245.     

水分对常压等离子体处理纤维结构与性能的影响

在空气相对湿度为5%,65%和95%的条件下,应用氦气/氧气常压等离子体处理芳纶和超高强度聚乙烯纤维,采用单纤维抽拔实验测定处理前后纤维与环氧树脂间的层间剪切强度,利用原子力显微镜和X射线光电子能谱仪分析等离子体处理前后纤维表面形态和化学成分的变化.结果表明:等离子体处理纤维随着处理环境湿度的增加,水分促进了芳纶表面的...     

Influence of moisture regain of aramid fibers on effects of atmospheric pressure plasma treatment on improving adhesion with epoxy

One difference between a low‐pressure plasma treatment and an atmospheric pressure plasma treatment is that in the atmosphere, the substrate material may contain significant quantities of moisture, which could potentially influence the effects of the plasma treatment. To investigate how the existence of moisture affects atmospheric pressure plasma treatment, aramid fibers (Twaron 1000) with three different moisture regains (0.5, 4.5, and 5.5%) were treated by an atmospheric pressure plasma jet for 3 s at a gas flow rate of 8 L/min, a treatment head temperature of 100°C, and a power of 10 W. The scanning electron microscopy analysis showed no observable surface morphology change for the plasma treated samples. X‐ray photoelectron spectroscopy analysis showed the oxygen contents of the 0.5 and 4.5% moisture regain groups increased from that of the control, although the opposite was true for the 5.5% moisture regain group. The advancing contact angles of the treated fibers decreased about 8°–16° whereas their receding contact angles decreased about 17°–27°. The interfacial shear strengths of the treated fibers as measured using microbond pull‐out tests were more than doubled when the moisture regain was 4.5 or 5.5%, whereas it increased by 58% when the moisture regain was 0.5%. In addition, no significant difference in single fiber tensile strength was observed among the plasma treated samples and the control sample. Therefore, we concluded that moisture regain promoted the plasma treatment effect in the improvement of the adhesion property of aramid fibers to epoxy. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 242–247, 2006     

The effect of silica (SiO2) nanoparticles and ammonia/ethylene plasma treatment on the interfacial and mechanical properties of carbon-fiber-reinforced epoxy composites

A nanoparticle dispersion is known to enhance the mechanical properties of a variety of polymers and resins. In this work, the effects of silica (SiO₂) nanoparticle loading (0–2 wt%) and ammonia/ethylene plasma-treated fibers on the interfacial and mechanical properties of carbon fiber–epoxy composites were characterized. Single fiber composite (SFC) tests were performed to determine the fiber/resin interfacial shear strength (IFSS). Tensile tests on pure epoxy resin specimens were also performed to quantify mechanical property changes with silica content. The results indicated that up to 2% SiO₂ nanoparticle loading had only a little effect on the mechanical properties. For untreated fibers, the IFSS was comparable for all epoxy resins. With ethylene/ammonia plasma treated fibers, specimens exhibited a substantial increase in IFSS by 2 to 3 times, independent of SiO₂ loading. The highest IFSS value obtained was 146 MPa for plasma-treated fibers. Interaction between the fiber sizing and plasma treatment may be a critical factor in this IFSS increase. The results suggest that the fiber/epoxy interface is not affected by the incorporation of up to 2% SiO₂ nanoparticles. Furthermore, the fiber surface modification through plasma treatment is an effective method to improve and control adhesion between fiber and resin.     

Properties of carbon fiber sized with poly(phthalazinone ether ketone) resin

We studied thermoplastic poly(phthalazinone ether ketone) (PPEK) resin as a sizing agent on carbon fiber, with emphasis on its thermal stability, surface energy, wetting performance, and interfacial shear strength (IFSS). X‐ray photoelectron spectroscopy characterization was carried out to study the chemical structure of sized/unsized carbon fibers. Scanning electron microscopy and atomic force microscopy were used to characterize surface topography. TGA was used to analyze the thermal stability. Meanwhile, contact angle measurement was applied to analyze the compatibility between the carbon fibers and PPEK and the surface energy of carbon fibers. IFSS of carbon fiber/PPEK composite was examined by microbond testing. It is found that carbon fibers uniformly coated with PPEK resin had better thermal stability and compatibility with PPEK resin than the uncoated fiber. The contact angle is 57.01° for sized fibers, corresponding to a surface energy of 49.96 mJ m^?2, much smaller than that for unsized ones with contact angle value of 97.05°. The value of IFSS for sized fibers is 51.49 MPa, which is higher than the unsized fibers. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Surface modification of PBO fibers by argon plasma and argon plasma combined with coupling agents

The methods of argon plasma and argon plasma combined with coupling agents were employed to modify the poly[1,4‐phenylene‐cis‐benzobisoxazole] (PBO) fiber surface. The interfacial shearing strength (IFSS) of PBO fibers/epoxy resin was measured by the single fiber pull‐out test. The surface chemical structure and surface composition of PBO fibers were determined by FTIR and X‐ray photoelectron spectroscopy respectively. The morphology of the fiber surface was investigated by scanning electron microscopy and the specific surface area of the fibers was calculated by B.E.T. equation. Furthermore, the wettability of PBO fibers was confirmed by the droplet profile analysis method. The results showed that the elemental composition ratio of the fiber surface changed after the modification. The IFSS increased by 42 and 78% when the fibers were treated by argon plasma and argon plasma combined with the coupling agents, respectively. Meanwhile, the specific surface areas of the treated fibers were improved. In addition, compared with the modification of argon plasma, the modification of argon plasma combined with the coupling agents inhibited the attenuation phenomena of the IFSS and the wettability. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 1428–1435, 2006     

Surface modification of ultra-high strength polyethylene fibers for enhanced adhesion to epoxy resins using intense pulsed high-power ion beam

The effects of intense pulsed high power ion beam (HPIB) treatment of ultra-high strength polyethylene (UHSPE) fibers on the fiber/epoxy resin interface strength were studied. For this study, argon ions were used to treat Spectra? 1000 (UHSPE) fibers in vacuum. Chemical and topographical changes of the fiber surfaces were characterized using Fourier transform infrared spectroscopy in attenuated total reflectance mode (FTIR-ATR), X-ray photoelectron spectroscopy (XPS), dynamic wettability measurements, and scanning electron microscopy (SEM). The fiber/epoxy resin interfacial shear strength (IFSS) was evaluated by the single fiber pull-out test. The FTIR-ATR and XPS data indicate that oxygen was incorporated onto the fiber surface as a result of the HPIB treatment. The wettability data indicate that the fibers became more polar after HPIB treatment and also more wettable. Although the total surface energy increased only slightly after treatment, the dispersive component decreased significantly while the acid-base component increased by a similar amount. SEM photomicrographs revealed that the surface roughness of the fibers increased following the HPIB treatment. The single fiber pull-out test results indicate that HPIB treatment significantly improved the IFSS of UHSPE fibers with epoxy resin. This enhancement in IFSS is attributed to increased roughness of the fiber surface resulting in mechanical bonding and in increased interface area, increased polar nature and wettability, and an improvement in the acid-base component of the surface energy after the HPIB treatment.     

Influence of environmental moisture on atmospheric pressure plasma jet treatment of ultrahigh-modulus polyethylene fibers

One of the main differences between low-pressure and atmospheric-pressure plasma treatments is that there is little moisture involved in the low-pressure plasma treatment, although moisture could exist at the wall of the vacuum chamber or react with the substrate after plasma treatment, while in the atmospheric-pressure plasma treatment moisture exists not only in the environment but also in any hygroscopic substrate. In order to investigate the influence of environmental moisture on the effect of atmospheric pressure plasma treatment, ultra-high-modulus polyethylene (UHMPE) fibers were treated using an atmospheric-pressure plasma jet (APPJ) with 10 l/min helium gas-flow rate, treatment nozzle temperature of 100°C and 5 W output power. The plasma treatments were carried out at three different relative humidity levels, namely 5, 59 and 100%. After the plasma treatments, the surface roughness increased while the water-contact angle decreased with increasing relative humidity. The number of oxygen containing groups increased as the environmental moisture content increased. The interfacial shear strength of the UHMPE fiber/epoxy system was significantly increased after the plasma treatments, but the moisture level in the APPJ environment did not have a significant influence on the adhesion properties. In addition, no significant difference in single fiber tensile strength was observed after the plasma treatments at all moisture levels. Therefore, it was concluded that the environmental moisture did not significantly influence the effect of atmospheric-pressure plasma treatment in improving interfacial bonding between the fiber and epoxy. The improvement of the interfacial shear strength for the plasma-treated samples at all moisture levels was mainly due to the increased surface roughness and increased surface oxygen and nitrogen contents due to the plasma etching and surface modification effect.     

Effects of electrophoretically deposited carbon nanofibers on the interface of single carbon fibers embedded in epoxy matrix

Electrophoretic deposition (EPD) was used to deposit carboxylic acid-functionalized carbon nanofibers (O-CNFs) on the surface of single carbon fibers. Using the single fiber fragmentation technique and Weibull analysis, interfacial shear strength (IFSS) was estimated for different fiber surface treatments. Samples for sized, unsized, O-CNF deposited sized, and O-CNF deposited unsized carbon fibers were tested. Additionally, the effects of EPD were investigated by testing sized and unsized carbon fiber samples exposed to an electric field in water. Removal of the fiber sizing decreased IFSS by approximately 27%, but addition of O-CNFs to the unsized fiber surface led to an increase of 15% compared to the sized base fiber. The O-CNF deposited sized fibers provided IFSS increases of 207.6% and 66.9% for 1 and 5 min deposition durations, respectively. The surface morphology of all samples was characterized, and those containing homogeneous deposition of closely bound O-CNFs provided the highest IFSS values. Exposing sized fibers to the electric field for 1 min led to an IFSS increase of 79%, while unsized fibers undergoing the same treatment provided increases of 7.7% and 46% compared to the base sized fiber and unsized fiber samples, respectively.     

Hydrophobic surface modification of ramie fibers by plasma-induced addition polymerization of propylene

The low affinity between hydrophilic cellulose fibers and hydrophobic matrices leads to poor interfacial bonding, reducing the mechanical performances of natural cellulose fiber-reinforced composites. This study illustrates plasma-induced addition polymerization of propylene to create a hydrophobic surface on ramie fibers for enhancing their bonding with polypropylene (PP). Plasma treatment with propane is applied for comparison. The advancing contact angles of the plasma-treated ramie fibers are raised from 66.3° to 106.1° and the interfacial shear strengths with PP are enhanced up to 36.4%, likely resulted from the increase in fiber surface roughness observed under a scanning electron microscope and the introduction of plasma-grafted PP and alkyl groups on fibers surfaces proven by X-ray photoelectron spectroscopy. It is also revealed that plasma treatment with propylene is highly effective in increasing surface carbon content (from 68.3% to 82.4% in 0.5 min) and more efficient than the treatment with propane, though both plasma treatments show substantial modification efficacies to the fiber surfaces. The treatment duration affects surface roughness more than surface chemical composition, and the optimized treatment time is around 1 min. The modification method developed in this research has the potential to be used for surface modification of fibers for many applications.     

常压等离子体改善合成纤维吸湿性的研究

用氦气作为等离子体的气体源、对涤纶、锦纶6、高强度聚乙烯纤维,Twaron 1000芳纶4种合成纤维进行常压等离子体处理,改善纤维的吸湿性能。结果表明:常压等离子体处理,对涤纶和锦纶6的表面有一定的刻蚀作用,但对高强度聚乙烯纤维、Twaron 1000芳纶的表面没有明显影响;经常压等离子体处理后,合成纤维表面氧、氮有所增加,吸湿性能得到提高,强度没有显著变化。     

热处理温度对PBO纤维性能的影响

PBO纤维因其具有高强度、高模量、高耐热性以及高化学稳定性等性能而被公认为目前综合性能最好的有机纤维。对自制的初生PBO纤维分别在500℃、550℃、600℃、650℃和700℃进行高温热处理,并对处理后纤维的力学性能、耐热性能、表面形貌以及界面性能进行测试。结果表明,500℃下热处理后PBO纤维拉伸强度最大为4.72GPa,随着热处理温度升高,纤维的力学性能下降;600℃下热处理后PBO纤维的初始分解温度最高为641.3℃;随着热处理温度的提高,PBO纤维的表面粗糙度在增加,同时其界面剪切强度(IFSS)也随着温度的升高而增大。