^60Co辐照对PTFE表面结构和表面能的影响

为了改善氟聚合物加工性和二次加工性,研究了PTFE聚合物的加工技术。以不同剂量辐照PTFE,PTFE粉末辐照后表面晶相没有发生变化。模压辐照的PTFE,其密实性较好,表面光滑。同时,辐照PTFE后表面有大量的极性亲水基团出现,使表面极性分量增加;而色散分量变化较小。辐照产生的表面极性基团减小了由于不同模压产生的表面所引起的接触角变化。     

Calendar of events

This review reports the successful synthesis of novel oligomeric silanes having end-capped fluoroalkyl groups. Glass surface was effectively modified by these oligomeric silanes. In particular, oligomeric silanes were more reactive and effective in the surface fluoroalkylation than monomeric silanes. From contact angle measurements, surface free energies were reduced to 15–20 and 1–3 mJ/m² for the dispersive and the polar components, respectively, and the surfaces were shown to be both highly water- and oil-repellent. Modified glass surface was analyzed using XPS. A linear correlation was observed between the dispersive component of surface free energy γ_S ^d and the area ratio of the F1s peak to the Si2p peak. The structure of the siloxane layer on the modified glass surface is discussed in terms of a network interphase model.     

A Reinterpretation of Organic Liquid-Polytetrafluoroethylene Surface Interactions

The wettability of polytetrafluoroethylene (PTFE) by organic liquids is reanalyzed in terms of dispersion-polar interactions across the liquid-solid interface. The analysis provides values of γ_s ^d = 19.6 dyne/cm, and γ_S ^D = 2.0 dyne/cm for the respective dispersion and polar parts of the surface tension γ_s = 21.6 for PTFE. The definition of a polar contribution to the surface tension of PTFE clarifies detailed aspects of the wettability of this polymer by different homologous liquid series. A modified analytical definition for work of adhesion is developed and applied to this discussion.     

Improved adhesion of poly(tetrafluoroethylene) by NH3-plasma treatment

—Surface modification of poly(tetrafluor oethylene) (PTFE) by NH₃-plasma treatment was investigated by means of contact angle measurement, XPS, and ATR FT/IR spectroscopy. The modified surfaces were adhesively bonded to nitril rubber. The NH₃-plasma irradiation made PTFE surfaces hydrophilic. The contact angle of water on the modified PTFE surface was 16 deg, and the surface energy was 62-63 mJ/m². The NH₃-plasma irradiation improved adhesion between PTFE and nitril rubber using a phenol-type adhesive. The peel strength of the joints reached 8.1 × 10³ N/m. Carbonyl and amido groups were created on PTFE surfaces by the NH₃-plasma irradiation. The mechanism of the improvement of adhesion by the NH₃-plasma irradiation is discussed.     

Optical Absorption and EPR Studies on Gamma-Ray Irradiated RE<Superscript>3+</Superscript>-Doped Fluorophosphate Glasses

We have studied the effect of γ-ray irradiation on optical absorption, emission and decay characteristics of RE³⁺ (RE?=?Sm, Eu and Dy)-doped fluorophosphate glasses. Electron paramagnetic resonance (EPR) study confirms the POHC and PO₃ EC defects induced in glasses by the γ-irradiation. The presence of induced defect centers significantly affects the optical and emission properties. The optical band gap values of the studied systems increased after the γ-ray irradiation. The phonon energy and electron–phonon coupling strength of Eu³⁺-doped fluorophosphate glass were determined from the phonon sideband analysis. The emission intensity of the RE³⁺ ions increased significantly after the γ-ray irradiation. The intensity parameter, R is the ratio of the intensities of the ⁵D₀ → ⁷F₂/⁵D₀ → ⁷F₁ transitions of Eu³⁺ ion and Y/B intensity parameter is the ratio of intensities of the ⁴F_9/2 → ⁶H_13∕2/⁴F_9/2 → ⁶H_15/2 transitions of Dy³⁺ ion reveal that the local environment around the RE³⁺ ion changed after the γ-ray irradiation in the present system. The lifetime of excited states of RE³⁺ ions decreased after the γ-ray irradiation due to the formation of defects induced by the γ-ray irradiation. The CIE color coordinates were determined before and after the γ-ray irradiation for the Dy³⁺-doped glass system.     

End-capped fluoroalkyl-functional silanes. Part II: Modification of polymers and possibility of multifunctional silanes

This work reports the fluoroalkylation of polymer surfaces using novel oligomeric silanes having end-capped fluoroalkyl groups. Polymer surfaces such as cellulose, poly(ethylene terephthalate) (PET), polyethylene, and poly(methyl methacrylate) (PMMA) etc. were effectively modified by these oligomeric silanes as well as the glass surface. From the contact angle measurements, the dispersive and polar components of surface free energies were reduced to 15–20 and 1–3 mJ/m², respectively, and the surfaces were shown to be both highly water- and oil-repellent. Modified cellulose and PET surfaces were analyzed using XPS measurements. In the case of cellulose, a linear correlation was observed between the dispersive component of surface free energy γ_S ^d and the area ratio of the F1s peak to the Si2p peak. In the case of PET, the hickness of siloxane layer on the surface was shown to be less than 8 nm. The modified PET surface showed a high solvent durability against common organic and inorganic solvents except fluorochemicals and alkalis. The structure of the siloxane layer on the modified surface is discussed in terms of a network interphase model. It was also shown to be quite easy to add another function such as hydrophilicity (flip-flop character) and/or antibacterial property in addition to the water- and oil-repellency imparted by fluoroalkyl groups.     

Surface modification of poly(tetrafluoroethylene) film by plasma graft polymerization of sodium vinylsulfonate

Poly(tetrafluoroethylene) (PTFE) surface was modified by the graft polymerization of sodium vinylsulfonate, and the chemical composition of the graft-polymerized PTFE surface was analyzed by X-ray photoelectron spectroscopy. Peroxides were formed on the PTFE surface by a combination procedure of argon plasma irradiation and air exposure, and the graft polymerization of sodium vinylsulfonate was initiated by the peroxide groups at 65–80°C. The peroxide concentration is 3 × 10⁺¹³ to 5 × 10⁺¹³ numbers/cm². The average degree of polymerization of the graft polymers was 3.4 × 10³. The graft polymer is distributed over the PTFE surface, but part of the PTFE surface remains uncovered. The coverage with the graft polymer is 43%. The PTFE surface graft polymerized with sodium vinylsulfonate was somewhat hydrophilic, but the hydrophilicity was lower than that of the PTFE surface modified by plasma treatment. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 66: 77–84, 1997     

Studies on the surface free energy and surface structure of PTFE film treated with low temperature plasma

The surface free energy and surface structure of poly(tetrafluoroethylene) (PTFE) film treated with low temperature plasma in O₂, Ar, He, H₂, NH₃, and CH₄ gases are studied. The contact angles of the samples were measured, and the critical surface tension γ_c (Zisman) and γ_c (max) were determined on the basis of the Zisman's plots. Furthermore, the values of nonpolar dispersion force γ^a_s, dipole force γ^b_s, and hydrogen bonding force γ^c_s to the surface tensions for the plasma-treated samples were evaluated by the extended Fowkes equation. Mainly because of the contribution of polar force, the surface free energy and surface wettability of PTFE film which was treated with H₂, He, NH₃, Ar, and CH₄ for a short time increased greatly. Electron spectroscopy for chemical analysis (ESCA) shows that the reason was the decrease of fluorine and the increase of oxygen or nitrogen polar functional group on the surface of PTFE. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 63: 1733–1739, 1997     

Surface free energy of synthetic chalcocite from zeta potential and contact angle techniques

—The zeta potentials of synthetic chalcocite wetted with n-alkanes were determined in doubly-distilled water. Then the relationship between the coverage of the chalcocite surface with n-heptane or n-hexanol and the zeta potential in water was found. Using an empirical relation, the film pressure of n-heptane and n-hexane was determined. Next the dispersive and polar components of the surface free energy were calculated. The value of the dispersive component was also determined by contact angle measurements. The values obtained were 81.0 and 22.7 mJ/m², for the dispersive and the polar components of the surface free energy, respectively.     

Modeling Equilibrium Moisture Content of γ-Ray Irradiated Rough Rice

Experimental studies show that gamma irradiation dose affects the values of equilibrium moisture content of grain at the same relative humidity and temperature of ambient. Values of the equilibrium moisture content decreased with increasing dose of γ-ray irradiation during both adsorption and desorption. Factor of irradiation dose was included in three widely used models for equilibrium moisture content; the parameters in the models were estimations from experimental data. Based on the correlation coefficient, mean relative error, and standard error of moisture, the modified Chung-Pfost equation and the modified Henderson equation were found to fit the desorption and adsorption isotherms for rough rice in the range of experimental conditions studied.     

Number-average molecular weight of radiation-degraded poly(tetrafluoroethylene). An end group analysis based on solid-state NMR and IR spectroscopy

Changes in the chemical structure of poly(tetrafluoroethylene) (PTFE) induced by electron beam irradiation at room temperature in air have been studied by ¹⁹F solid-state NMR and IR spectroscopy. Chain scission associated with the formation of trifluoromethyl (-CF₃), carboxylic acid fluoride (-COF) and carboxylic acid (-COOH) end groups was confirmed to be the predominant process under these conditions. The number-average molecular weight of radiation-degraded PTFE as a function of irradiation dose was calculated based on quantitative end group analysis. It strongly decreases with increasing dose to approximately 4000 g/mol at a irradiation dose of 4 MGy. The molar ratio of CF₃ end groups to oxygen-containing (-COF, -COOH) end groups was found to depend on the irradiation dose and the irradiation conditions. For low dose level, the molar ratio determined experimentally coincides well with the mechanism proposed for radiation-induced degradation of PTFE.     

Surface Modification of Fluorinated Polymers by Microwave Plasmas

We developed a new plasma treating method, incorporating the use of microwaves generated by an electronic cooking range. Using this method, polytetrafluorethylene (PTFE) and a copolymer of tetrafluoroethylene and hexafluoropropylene (FEP) were treated. Dialkylphthalates (DAP) were used as the standard liquids of contact angle measurements for evaluation of the wetting properties of plasma treated polymers. The components of surface tension (γ_L) due to the dispersion force (γ^d _L) and the polar force (γ^P _L) of DAP were calculated by Fowkes' equation from the contact angles (θ) on polypropylene. After plasma treatment cos θ of several standard liquids on PTFE and FEP increased. The linear relationship between γ_L(1 + cos θ)/(γ^d _L)^½ and (γ^P _L/γ^P _L)^½ was verified. γ_s and γ^d _s and γ^d _s of the plasma treated PTFE and FEP also increased. From the results of ESCA analysis, it was found that a significant amount of oxygen was introduced to the polymer surface by the plasma treatment. Peel strengths of a pressure sensitive adhesive bonded to PTFE and FEP increased approximately two-to threefold if the plasma treatment was used prior to bonding.     

Ion beam ablation of polytetrafluoroethylene

Polytetrafluoroethylene (PTFE) was irradiated with 300 keV Ar⁺ ions to the fluences of 1 × 10¹⁴ to 1 × 10¹⁶ cm⁻²; the PTFE structural changes induced by the ion irradiation were studied by X-ray diffraction and UV–vis and IR spectroscopies. The electrical conductivity of the ion beam modified PTFE was also investigated using the standard technique, and the alterations of the surface polarity were determined by contact angle measurements. The ion irradiation leads to intensive PTFE ablation due to the breaking of the C—C bonds in the polymer molecular chains and due to the production and liberation of the molecular fragments C_xF_y. In contrast to other polymeric materials, the irradiated PTFE carbonizes to a lesser extent and the observed irradiation induced increase of the electrical conductivity is also not significant. In-coming ions cause a reduction of the crystalline phase content in the PTFE samples. © 1998 John Wiley & Sons, Inc. J Appl Polm Sci 69: 1257–1261, 1998     

表面改性在提高硅胶基体与抗菌涂层结合力中的应用

聚合物基体与抗菌涂层间结合力的大小至关重要,它决定了抗菌制品的使用寿命与抗菌效果。本研究中采用γ射线辐射改性聚合物基体表面,并接枝偶联剂（γ-APTS）获得活性表面,从而制得紧密键合在基体表面的 Ag-PTFE复合抗菌涂层。通过扫描电子显微镜（SEM）观察涂层表面形貌,X射线能量色散谱（EDS）与面分布表征涂层中各元素分布状况;ASTM D-3359法测试涂层与基体间结合力;通过对多组大肠杆菌的抑菌环试验与震荡烧瓶实验表征涂层抗菌活性。结果表明,γ射线辐照可有效提高聚合物基体表面活性,显著提高了涂层与基体间结合力,且抗菌效果优异。     

The Effect of Lowering the Surface Free Energy of Water on the Thermodynamic Work of Adhesion

The dispersive and polar force components of surface free energy have been measured for water left in contact with films dried from various emulsion adhesives. The polar component was lowered but the dispersive components were about 28 mJ m^?2 in each case. From these measurements of thermodynamic work of adhesion in the presence of contaminated water have been calculated for adhesive-polystyrene interfaces. An equation has been derived giving the dependence of thermodynamic work of adhesion upon the total surface free energy of water. It shows that the thermodynamic work of adhesion decreases as the surface free energy of water is lowered, but it eventually reaches a minimum and then may increase slightly.     

Arylidene polymers. VI. Gamma irradiation effects on the electrical conductivity behavior,IR absorption spectra,and DSC measurements of some new synthesized poly(arylidenecycloalkanones)

Gamma irradiation effects on the electrical conductivity behavior of some new synthesized poly(2,5-arylidenecyclopentanone) 1 , poly(2,6-arylidenecyclohexanone) 2 , and their co-polymers 3 , have been investigated. Thermal studies over the temperature range 300-500 K showed that the conductivity behavior follows a two-term Arrhenius-type equation. The first term has a small activation energy and predominates at lower temperature (extrinsic region), and the second term with higher activation energy predominates at higher temperatures (intrinsic region). Change in the activation parameters with the change in the γ-ray dose and the nature of the polymers are discussed. The IR absorption spectra showed a decrease in the intensity of most bands of the γ-irradiated samples. A mechanism based on the formation of trapped free radicals and their recombination has been suggested. DSC measurements indicated that the crystallization and the melting temperature transitions decreased in size considerably with the increase in the γ-ray dose until they nearly disappeared at higher γ-ray dose.     

Small angle neutron scattering studies on structural inhomogeneities in polymer gels: irradiation cross-linked gels vs chemically cross-linked gels

A comparison of network structure in a solvent was made for two types of poly(N-isopropylacrylamide) gels cross-linked by chemical reaction with N,N′-methylenebisacrylamide (BIS) (chemical gels) and by γ-ray irradiation (γ-ray gels). The cross-linking density dependence for these gels was examined by small angle neutron scattering (SANS). The SANS results indicated an increase of frozen inhomogeneities with an introduction of cross-links for both chemical and γ-ray gels. However, it was found that the effect of cross-linking is much stronger in the chemical gels than in the γ-ray gels. The differences in the structure were successfully interpreted by a statistical-mechanical theory of gels proposed by Panyukov-Rabin (Phys. Rep. 269 (1996) 1). The degree of polymerization between cross-links, N, was a decreasing function of cross-linking content for both types of gels, while that for the γ-ray gels was a weak function of irradiation dose. Quantitative analyses on BIS concentration and γ-ray dose dependence led to an experimental evidence of the existence of cross-linking saturation threshold.     

Grafting of poly(ethylene-block-ethylene oxide) onto a vapor grown carbon fiber surface by γ-ray radiation grafting

To modify the surface of vapor grown carbon fiber (VGCF), poly(ethylene-block-ethylene oxide) (PE-b-PEO, M_n=1400, PEO content=50 wt%) was successfully grafted onto the surface by using γ-ray irradiation of the PE-b-PEO-adsorbed VGCF in solvent-free system. It is found that the percentage of polymer grafting reached 15.0% when the PE-b-PEO-adsorbed VGCF was irradiated by γ-ray over 40 kGy dose at 110 °C, but at the lower irradiation temperature of 75 °C, the grafting reaction scarcely proceeded. This indicates that polymer radicals formed by γ-ray irradiation were successfully trapped by VGCF surface above melting point of PE-b-PEO. On the other hand, when the dispersion of VGCF in THF solution of PE-b-PEO was irradiated, the percentage of PE-b-PEO grafting was less than 4.0%. It was confirmed by a field-emission scanning electron microscope (FE-SEM) that the surface of the VGCF was uniformly covered by grafted PE-b-PEO. In addition, the surface free energy of ungrafted and PE-b-PEO-grafted VGCF was determined.     

The Use of AFM and Surface Energy Measurements to Investigate Drug-Canister Material Interactions in a Model Pressurized Metered Dose Inhaler Formulation

The aim of the project was to investigate the interactions between micronized salbutamol sulphate, budesonide, and formoterol fumarate dihydrate and different canister surfaces materials (Aluminium, anodized aluminium, perfluoroalkoxy, fluorinated ethylene propylene—polyether sulphone, and polytetrafluoroethylene) used in pressurized metered dose inhalers (pMDIs).

The surface component approach for polar and apolar interfacial interactions was used to predict the adhesion behavior of micronized drugs with the inner surfaces of pMDI canisters. This was achieved using a combination of in situ colloid probe atomic force microscopy (AFM) measurements and theoretical treatment of the surface free energy measurements, via a contact angle–based technique of the interacting surfaces.

All three drugs exhibited similar dispersive surface energy free values. A greater variation was, however, found in the polar component of the surface free energy measurements. These results were also reflected in the dispersive and polar components of the canister materials. Moreover, the linear relationship between the work of adhesion and AFM measured adhesion was shown to be correlated on the polar contributions of the surface free energies of the interacting materials. AFM measurements indicated that salbutamol sulphate was found to have the strongest adhesive forces with respect to the canister surface materials while budesonide and formoterol fumarate dihydrate appeared to have similar adhesive characteristics. The present study suggests that investigations into the design and characterization of pMDI formulations would benefit from considerations of the polar contribution of the surface free energy and relative work of adhesion of the drug and various components of a pMDI system.     

Surface modification of polyethersulfone hollow-fiber membranes by γ-ray irradiation

The fouling of ultrafiltration membrane is often caused by gel formation on the membrane surface. This gel layer arises due to concentration polarization or macromolecular adsorption on the membrane surface. The gel layer affects both the hydraulic permeability and the rejection properties of the membrane. In this report, the adsorption of porcine albumin and the concentration polarization effect on modified and unmodified polyethersulfone (PES) hollow-fiber membrane is studied. PES ultrafiltration hollow-fiber membranes were modified by the grafting of polyethylene glycol (PEG) polymer on the internal surface using γ-ray irradiation method. The modified hollow fibers were less susceptible to fouling than were the unmodified fiber. The performance of both modified and unmodified hollow fibers was tested as a function of feed flow rates and protein concentrations. © 1994 John Wiley & Sons, Inc.