Surface characterization of PET nonwoven fabric treated by He/O2 atmospheric pressure plasma

The surface of polyethyleneterephthalate (PET) nonwoven fabric was modified by He/O₂ atmospheric pressure plasma treatment, varying plasma exposure time. The plasma treated PET surfaces have been analyzed to investigate the chemical nature and morphology of surface by X‐ray photoelectron spectroscopy (XPS) and atomic force microscopy (AFM), respectively. The change of wettability was measured depending on plasma exposure time. XPS results indicated the presence of oxygen‐based functional groups on the PET nonwoven fabric surface after plasma treatment and oxygen content increased as exposure time increased. The mean roughness increased after 30 s exposure and further increase in exposure to 60 s led to decrease of the roughness and then again increase. The root mean square roughness followed the similar trend to mean roughness. The average difference in height, Rz, increased after plasma exposure for 30 s, while it slightly decreased after 60 s exposure. Despite of redeposition, the Rz of 90 s exposed sample increased more than two times compared with those of 30 and 60 s exposed. Wettability increased progressively up to 10 times after 90 s exposure compared with the untreated. It is attributed to the increases of hydrophilicity and surface roughness. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

常压等离子体处理芳砜纶的结构与性能研究

分别采用氦气和氦气/氧气对芳砜纶进行常压等离子体处理。采用滴水吸收实验测定处理前后纤维表面的润湿性,利用扫描电子显微镜和X射线光电子能谱仪分析处理前后纤维表面形态和化学成分的变化。结果表明:经常压等离子体处理后芳砜纶表面粗糙度增加,纤维表面碳元素含量下降,羟基、羧基等含氧或氮的极性基团增加,芳砜纶纱线的润湿性能提高,纱线强度没有明显变化,氦气/氧气等离子体处理比氦气等离子体处理效果更好。     

Study on wettability improvement and its uniformity of wool fabric treated by atmospheric pressure plasma jet

The influence of processing parameters on wettability improvement and its uniformity of wool fabric treated by atmospheric pressure plasma jet (APPJ) was explored. A woven wool fabric was treated by APPJ under various treatment conditions such as different treatment time, different oxygen flow rate, and different jet‐to‐substrate distance. The water absorption time of wool fabric was measured to determine wettability improvement. The diffusion photo of water droplet on wool fabric surface was taken by digital camera to reflect wettability uniformity. After APPJ treatment, SEM observation showed that the scales on the wool fiber surface directly facing plasma jet pores were destroyed than those on the other fiber surface. XPS analysis showed that the carbon concentration substantially decreased. The concentration of oxygen and nitrogen significantly increased and but the concentration of sulfur and silicon did not obviously changed. With the addition of oxygen gas, more polar groups such as hydroxyl and carboxyl produced on wool fiber surface. The water absorption time of wool fabric greatly reduced indicating wettability improvement. The diffusion of water droplet on wool fabric surface was also larger and more homogenous suggesting uniform plasma treatment. It was concluded that the wettability improvement and its uniformity of the treated wool fabric increased and then decreased with the increasing oxygen flow rate and jet‐to‐substrate distance, and increased with the increasing treatment time. Therefore to achieve reasonable wettability and its uniformity of the wool fabric treated by APPJ, plasma treatment conditions have to be carefully chosen. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

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。     

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.     

Surface modification of nylon 6 films treated with an He/O2 atmospheric pressure plasma jet

To investigate the effect of the gas composition of the plasma treatment on the surface modification of an atmospheric pressure plasma jet (APPJ), nylon 6 films were treated with APPJ with pure helium (He), He + 1% oxygen (O₂), and He + 2% O₂, respectively. Atomic force microscopy showed increased surface roughness, whereas X‐ray photoelectron spectroscopy revealed increased oxygen contents after the plasma treatments. The plasma‐treated samples had lower water contact angles and higher T‐peel strengths than the control. The addition of a small amount of O₂ to the He plasma increased the effectiveness of the plasma treatment in the polymer surface modification in terms of surface roughness, surface oxygen content, etching rate, water contact angle, and bonding strength. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Effect of polymer microstructure on dye diffusion in polyamide 66 fibers

Our previous work showed that drawing polyamide 66 (PA 66) fibers at room temperature does not change the degree of crystallinity, but only increases the molecular orientation. We therefore have used a series PA 66 fibers with different draw ratios to establish a direct correlation between (noncrystalline) molecular orientation f_a and the dye diffusion coefficient D. For both acid and disperse dyes, the relationship log D ∝ f provides reasonable fits to the data for PA 66 fibers, and a similar relationship appears to be applicable to PA 6 fibers. Heat‐setting the fibers results in a continuous decrease in diffusion coefficient; unlike PA6 and PET fibers, no minimum in D was found in the region of 160°C. If this decrease in D is attributed to the increase in volume fraction crystallinity X taking place during heat‐setting, it must be deduced that log D ∝ X⁶. This dependence is surprisingly strong, but is consistent with observations we have made on PET and PA6 fibers. It is possible that some other structural rearrangement is partially or largely responsible for the decrease in diffusion coefficient, but Fourier transform infrared, density, and X‐ray diffraction measurements do not indicate any other structural changes taking place. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 3803–3807, 2003     

Effect of alcohol pretreatment in conjunction with atmospheric pressure plasmas on hydrophobizing ramie fiber surfaces

To improve interfacial adhesion between hydrophilic cellulose fiber and hydrophobic polymer matrix, ramie fibers were pretreated with isopropanol and n-butanol and then plasma treated using an atmospheric pressure plasma apparatus. For the plasma-treated fibers, the scanning electron microscopy shows increased surface roughness and the X-ray photoelectron spectroscopy analysis shows a significant increase of C–C bond in isopropanol-pretreated group, whereas for n-butanol-pretreated group the raise of C=O bonds is most noticeable. For both alcohol-pretreated and plasma-treated groups, the water contact angles increase significantly. Microbond pull-out test shows interfacial shear strengths of fiber/polypropylene (PP) samples increase by 47 and 34%, respectively, for the two groups compared with the control. Therefore, it can be concluded that the reaction between both alcohols and cellulose induced by plasma can indeed create a fiber surface with increased roughness and decreased polarity, and thus is more compatible to PP.     

Adhesion characteristics of carbon/epoxy composites treated with low- and atmospheric pressure plasmas

Although an adhesive joint can distribute load over a larger area than a mechanical joint, requires no holes, adds very little weight to structures and has superior fatigue resistance, it requires careful surface preparation of adherends for reliable joining and low susceptibility to service environments. The load transmission capability of adhesive joints can be improved by increasing the surface free energy of the adherends with suitable surface treatments. In this study, two types of surface treatment, namely the low pressure and the atmospheric pressure plasma treatment, were performed to enhance the mechanical load transmission capabilities of carbon/epoxy composite adhesive joints. The suitable surface treatment conditions for carbon/epoxy composite adhesive joints for both low and atmospheric pressure plasma systems were experimentally investigated with respect to chamber pressure, power intensity and surface treatment time by measuring the surface free energies of the specimens. The change in surface topography of carbon/epoxy composites was measured with AFM (Atomic Force Microscopy) and quantitative surface atomic concentrations were determined with XPS (X-ray Photoelectron Spectroscopy) to investigate the failure modes of composite adhesive joints with respect to surface treatment time. From the XPS investigation of carbon/epoxy composites, it was found that the ratio of oxygen concentration to carbon concentration for both low and atmospheric pressure plasma-treated carbon/epoxy composite surfaces was maximum after about 30 s treatment time, which corresponded with the maximum load transmission capability of the composite adhesive joint.     

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     

Application of confocal laser scanning microscope technique to visualize dynamic sorption behavior of perylene in cellulose acetate film

Additives distributed in a polymer film were visualized by a confocal laser scanning microscope (CLSM) in this study. Cellulose acetate (CA) was used as the polymer film material. Perylene as a fluorescence reagent and glycerol triacetate (GTA) as a plasticizer for CA, respectively, were selected and mixed for visualizing the absorption of perylene into CA. Under optimized CLSM conditions of an objective lens (dry, 20×) and diode laser (408 nm, 290–330 μW), a fluorescent penetrant, perylene, in GTA solution was detected in CA casting film within around 9 μm depth of the film in 60 minutes after starting the sorption study. It was also found that the fluorescence intensity of perylene became lower with the film depth. This finding suggested that CLSM could visualize the sorption behavior of perylene as a dynamic diffusion process. Analytical conditions, such as a scanning range along the Z axis (±10 or ±30 μm from an air‐contact surface of the CA film) and a scan speed (1 or 30 fps) of CLSM, did not affect the fluorescence intensity of the sorbed perylene. It was concluded that a newly developed analytical methodology using CLSM was sufficient for visualizing the perylene penetrant across the cross‐sectional distribution of the CA film, being capable of monitoring the sorption behavior of compounds in polymer materials without any destruction of a given absorbed film. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Dye diffusion studies in PET fibres by confocal laser scanning microscopy and the interrelation with the glass transition

Confocal laser scanning microscopy (CLSM) is used to monitor the dye penetration in poly(ethylene terephthalate) fibres during a common commercial dyeing process. The study of optical sections of fibres dyed for prolonged times in the dyeing process allows for a qualitative interpretation of the dye diffusion process, which is not possible by other techniques. A major dissimilarity was revealed between the diffusional behaviours of the two dye classes studied. The anthraquinone dyes showed a much lower temperature onset of dye penetration during the dyeing process than the benzodifuranone dyes (approximately 110 °C vs. 130 °C). Modulated differential scanning calorimetry was used to permit an understanding for this lower temperature onset and thus for the distinction in the driving forces of the dyeing mechanism between both dye classes. These driving forces were further shown to be similar for both the conventional textile fibres and the microfibres studied.     

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 multistratification and film depth on the visualized dynamic sorption behavior of perylene in cellulose acetate films by a confocal laser scanning microscope technique

The sorption behavior of a fluorescent reagent into a polymer film was visualized by confocal laser scanning microscopy (CLSM), and the effects of the additives, film types, and film depth on the diffusion coefficient (D) of the fluorescence reagent were examined. Perylene and cellulose acetate (CA) were used as a fluorescent reagent and a polymer material, respectively. Perylene dissolved in the additives triethylene glycol diacetate (TEGDA) and glycerol triacetate (GTA) was added to the CA film. Then, the evaluation of two types of CA films, a closed‐system cellulose acetate (CCA) sample and an open‐system cellulose acetate (OCA) sample, was conducted. At optimized CLSM conditions (with a scanning range at a 20‐μm depth from the CA film surface with 1‐μm intervals and a scanning speed of 1 fps), the sorption of perylene at the inner CA film was determined. The D values of perylene in the CA film were calculated pursuant to Fick's second law. Higher D values of perylene mixed with TEGDA versus those of perylene mixed with GTA were commonly obtained for the CCA sample (TEGDA: 8.9 × 10⁻¹⁵ m²/s > GTA: 1.7 × 10⁻¹⁵ m²/s) and the OCA sample (TEGDA: 11 × 10⁻¹⁵ m²/s > GTA: 3.3 × 10⁻¹⁵ m²/s) because of the higher chemical affinity of TEGDA with perylene than that of GTA. Perylene indicated a higher D value and was homogeneously distributed in the case of the OCA sample; we found that diffusivity and distribution of perylene in CA film were largely affected by the multistratification treatment. We also proved that the deeper the film depth was, the lower the diffusivity of perylene was, regardless of the types of additives and films. The factors considered for the film‐depth dependence of D were a gradual increase in the diffusion pathway for perylene caused by additive diffusion and the concentration dependence of the perylene D. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Variations in diffusion coefficient of disperse dyes in single PET fibres: monitored and interpreted by confocal laser scanning microscopy

A novel method is proposed for determining the diffusion coefficient (D) of disperse dyes in PET fibres. Concentration-distance profiles are recorded on optical sections of single fibres by confocal laser scanning microscopy. This allows for an accurate value of the true diffusion coefficient in the fibres as well as for a founded insight in the dye diffusion process and its interrelation with the glass transition, which is not possible by the commonly used methods. At 130 °C, the common industrial dyeing temperature, the diffusion coefficient showed to be constant for the dyes tested, with D being about five times larger for the anthraquinone dye than for the benzodifuranone dye. At 100-110 °C, near to the start of the glass transition region of the fibres, D could no longer be regarded as a constant for the anthraquinone dye but was concentration dependent. This was explained by the plasticising effect of the anthraquinone dye.     

Investigation into etching mechanism of polyethylene terephthalate (PET) films treated in helium and oxygenated‐helium atmospheric plasmas

This research makes an investigation into the etching mechanism of atmospheric plasma conditions on the surface of polyethylene terephthalate (PET) films. Two types of untreated PET films (S/200 and S/500) were exposed to plasma for 0 to 5.0 min in 30‐s increments. The first set of each film type was treated in helium plasma, while the second was treated in oxygenated‐helium plasma. Differential Scanning Calorimetry (DSC) was used to characterize pre‐ and post‐exposure films. Weight changes and the degree of solubility were also determined. Based on peak area results, the percent crystallinity of PET S/200 increased by an average of 4.57% (helium treated) and 13.56% (oxygenated‐helium treated), while the S/500 showed only a small increase. There was no significant change in the melting or crystallization temperatures of either film type, indicating a decrease in amorphous content versus an increase in crystalline material. Weight loss analysis supports this theory. Solubility testing revealed a continual decrease in swelling as exposure time was increased. A model was developed to predict the change in the degree of solubility for polyphase surfaces considering the etching rate per phase. The model was applied to PET with good correlation between the model and experimental data. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 94: 2383–2389, 2004     

Changes in wettability with time of plasma-modified perfluorinated polymers

Treatment of fluorinated ethylene propylene (FEP) and polytetrafluoroethylene (PTFE) by plasmas established in water vapour or ammonia gas enabled the rapid and facile modification of their surface chemistries. Under comparable plasma conditions, ammonia plasma exposures produced considerably lower air/water contact angles than water vapour plasmas. On storage of samples in air at ambient temperature, contact angles increased markedly within a few days on ammonia plasma-treated samples but remained constant over many weeks on water plasma-treated surfaces. Angle-dependent X-ray photoelectron spectroscopy (XPS) demonstrated a very low depth of modification in the case of ammonia plasma exposure, whereas the oxygen content of water plasma-treated samples was invariant with depth within the XPS analysis region. The long-term stability of water plasma-treated fluorocarbon polymer surfaces is believed to be due to this deep modification which prevents polymer chain reorientation, whereas the shallow modification in ammonia plasmas allows the rapid partial burial of the newly attached chemical groups inside the polymer. When ammonia plasma-treated samples stored in air were immersed in water, the contact angles remained constant, suggesting that the buried groups could not resurface. Contact angle measurements provided a simple and sensitive method for studying the time-dependent reduction in plasma treatment effects and the segmental mobility of modified fluorocarbon polymer surfaces; very shallow reorientation movements can be detected.     

Investigation of hydrogen plasma treatment for reducing defects in silicon quantum dot superlattice structure with amorphous silicon carbide matrix

We investigate the effects of hydrogen plasma treatment (HPT) on the properties of silicon quantum dot superlattice films. Hydrogen introduced in the films efficiently passivates silicon and carbon dangling bonds at a treatment temperature of approximately 400°C. The total dangling bond density decreases from 1.1 × 10¹⁹ cm^-3 to 3.7 × 10¹⁷ cm^-3, which is comparable to the defect density of typical hydrogenated amorphous silicon carbide films. A damaged layer is found to form on the surface by HPT; this layer can be easily removed by reactive ion etching.     

大孔结构重油加氢脱金属催化剂的制备、表征及重油在催化剂中有效扩散系数的求解

以大孔拟薄水铝石为原料,沥青残渣为造孔剂,经超临界干燥和焙烧得到催化剂载体,通过浸渍活性组分得到重油加氢脱金属催化剂并进行扩散实验。结果表明,制备条件对重油加氢脱金属催化剂的物性影响较大,通过对各种制备因素进行优化并对催化剂进行表征和扩散实验,进一步表明制备的催化剂具有较大的比表面积、孔容、适宜的孔分布及大孔结构,适合加工金属含量较高的原油,重油分子在添加造孔剂催化剂中的有效扩散系数变大。