Increase In Surface Free Energy Research Articles

Nucleation and crystal growth kinetics of poly(l-lactic acid) with self-assembled DBS nanofibrils

The effect of 1,3:2,4-dibenzylidene-d-sorbitol (DBS) on the crystallization behaviors of poly(l-lactic acid) (PLLA) was examined in this study. A small amount (≤4 wt%) of DBS altered the crystallization rate and regime transition temperature of PLLA. First, the addition of DBS and the formation of self-assembled DBS nanofibrils both increased the nucleation rate of PLLA. Second, the curves of the spherulitic growth rate versus the crystallization temperature of PLLA were discontinuous and did not show the typical bell-shaped behavior for all samples. We found that the change in crystal structures (α′-to-α) affected the regime transition temperatures, which led to the discontinuity. The regime transition (regime II–III) temperatures of PLLA slightly decreased as the DBS amounts were increased. This indicates that the more regular structure (regime II) of PLLA formed at lower temperatures when more DBS was added. In addition, the spherulitic growth rate of PLLA was found to be mainly influenced by the fold surface free energy. When the DBS amounts were increased, the increase in the fold surface free energy decreased the growth rate of PLLA. Nonetheless, the Avrami exponent, n, was not significantly changed because the spherulitic growth geometry and nucleation mechanism of PLLA were basically the same. The Avrami plot also shows that the secondary crystallization began earlier due to the formation of DBS nanofibrils for the samples containing higher DBS amounts.

Surface Free Energy Modification of Crude Rubber Using Oxygen Plasma and Uv Laser Treatment

A study has been made of the surface properties of nitrile-butadiene rubber and ethylene-propylene-diene monomer crude rubber, basic raw materials for offset lithographic printing blankets manufacturing. Increased surface free energy of the crude rubber was achieved by treatment with the low-pressure oxygen plasma. After plasma activation, samples were treated using a UV laser to deactivate the surface layer. The surface free energy was calculated on the basis of contact angles with different liquids. Plasma-treated samples had higher surface free energy, especially the polar component, and the effect was larger for nitrile-butadiene rubber samples. This surface free energy decreased after exposure to UV laser light. FTIR-ATR spectroscopy was used to detect possible changes in chemical structure of the surface, but no differences were obtained. Changes of surface free energy were thus most likely a consequence of changes in the surface structure.

Optical Emission Spectroscopy Study and 3-D Surface Characterization of Silicone Rubber Exposed to Different Argon RF Plasma Powers

The present study was undertaken to investigate the effect of argon plasma treatment on the extent of Foley catheter surface modification. Foley catheter (flexible tube made of silicone rubber, used for urinary catheterization) surface was treated at different argon (Ar) RF plasma powers. The surface modification was assessed by measurement of contact angle. Contact angle study shows decrease in contact angle and increase in surface free energy shows more polar group incorporation at low power plasma treatment. Atomic force microscopy (AFM) revealed an increased average surface roughness proportional to plasma power. Optical emission spectroscopy (OES) shows various states of argon causing surface modification.

Determination of Surface Free Energy and Contact Angle for Hydrolyzed Shellac

The purpose of this research was to determine surface free energy and contact angle of hydrolyzed shellac by using sessile drop technique. It is a method for determination of contact angle by placing a drop of liquid on a substrate and the surface free energy is then calculated by using the Wus equation. The substrate in this study was the hydrolyzed shellac prepared by hydrolysis of the native shellac at various times; 0, 15, 30 and 45 min using 2.0 %w/w sodium hydroxide. Water, formamide and ethylene glycol were liquids used for the investigation of the contact angle and surface free energy. The effect of hydrolysis time tended to reduce the contact angle and increase in the total surface free energy and polar force of hydrolyzed shellac. The result could be due to the breaking of the ester bonds of shellac during the hydrolysis process causing the higher free carboxyl group giving the higher polar group indicating by higher polar force and surface free energy. Therefore, the contact angle and surface free energy detected by sessile drop technique could be of benefit for the determination of hydrolysis process.

Dependence of surface free energy on molecular orientation in polymer films

Surface free energy of mechanically drawn polycarbonate films was determined using contact angle measurements and shown to increase with orientation. The increase in polymer film surface free energy was attributed to increased polymer chain packing during orientation, supported by film density measurements, which provides enhanced intermolecular interactions. Surface free energy can therefore be increased by, or used to predict, polymer orientation.

Complex investigations of structural and thermal properties of silica-titania adsorbents.

Mesoporous titanium-containing silicas with different Titania contents were investigated. The structural parameters of the materials were characterized by low-temperature adsorption/desorption of nitrogen and X-ray diffraction analysis. The thermodesorption of water using the quasi-isothermal thermogravimetry as well as the differential scanning calorimetry were used to characterize thermal and surface properties of these materials. The adsorbed water layers and the concentration of weakly and strongly bound water as well as the surface free energy on the adsorbent/water interfaces were calculated. It was stated that the increase of Titania content causes a gradual decrease of specific surface area and formation of biporous structure inside the tested materials. The water thermodesorption from the surface proceeds in two or three stages, which is connected mainly with pore distribution and TiO2 content. One can observe the increase of the total surface free energy (ΔG Σ) with the increasing TiO2 content, but the largest ΔG Σ value at the adsorbent/strongly bound water interface is exhibited by the adsorbent of intermediate content (30%) of TiO2. Freezing temperature of water contained in the pores of the studied materials is connected largely with their porous structure. Due to the well developed porous structure, the water freezing process is a multi-stage one.

Surface modification of polytetrafluoroethylene film using single liquid electrode atmospheric-pressure glow discharge

Polytetrafluoroethylene films are treated by room temperature helium atmospheric pressure plasma plumes, which are generated with a home-made single liquid electrode plasma device. After plasma treatment, the water contact angle of polytetrafluoroethylene film drops from 114° to 46° and the surface free energy increases from 22.0 mJ/m2 to 59.1 mJ/m2. The optical emission spectrum indicates that there are reactive species such as O+2, O and He in the plasma plume. After plasma treatment, a highly crosslinking structure is formed on the film surface and the oxygen element is incorporated into the film surface in the forms of —C—O—C—, —C=O, and —O—C=O groups. Over a period of 10 days, the contact angle of the treated film is recovered by only about 10°, which indicates that the plasma surface modification is stable with time.

Degradation of Perfluorotrichlorosilane Antisticking Layers: The Impact on Mold Cleaning, Ultraviolet-Nanoimprinting, and Bonded Ultraviolet-Nanoimprint Molds

A reduction of the adhesion between imprint resist and mold is crucial for defect free imprints and is commonly achieved by silane based antisticking layers. Highly stable antisticking layers are required for high throughputs and long imprint mold lifetimes. Hybrid nanoimprint molds avoid the imprint inherent residual polymer layer in UV-assisted nanoimprinting. Such hybrid molds have chemically heterogeneous surfaces of silica and, e.g., chromium oxide regions. The chemical stability of vapor-coated 1H,1H,2H,2H-perfluorodecyltrichlorosilane antisticking layers against acetone, acidic piranha, reactive ion etching and UV-assisted nanoimprinting was investigated. To evaluate the behavior of hybrid mold surfaces, flat silica and antireflective chromium-oxynitride surfaces were used. The antisticking layer on both surfaces was highly chemical resistant against acetone. A continuous antisticking layer degradation with a surface free energy increase of 0.9 mN/m per 10 min piranha treatment and 1.2 mN/m per 10 subsequent UV-assisted imprints was found for silica surfaces. On the chromium surfaces, the antisticking layer quality was much lower than on fused silica and degraded much faster. The surface free energy of silane coated chromium surfaces was increased by 2.3 mN/m after 10 imprints and the antisticking layer was completely degraded after a single 10 min piranha cleaning step. The lower antisticking layer quality on antireflective chromium was attributed to the surface itself. Additionally, the high chemical resistance of the vapor coated silane was used to successfully protect the adhesive joints of cost-efficient, adhesively bonded nanoimprint molds from being degraded by acidic piranha during mold cleaning. This can significantly increase the life-time of such bonded molds.

Degradation of Perfluorotrichlorosilane Antisticking Layers: The Impact on Mold Cleaning, Ultraviolet-Nanoimprinting, and Bonded Ultraviolet-Nanoimprint Molds

A reduction of the adhesion between imprint resist and mold is crucial for defect free imprints and is commonly achieved by silane based antisticking layers. Highly stable antisticking layers are required for high throughputs and long imprint mold lifetimes. Hybrid nanoimprint molds avoid the imprint inherent residual polymer layer in UV-assisted nanoimprinting. Such hybrid molds have chemically heterogeneous surfaces of silica and, e.g., chromium oxide regions. The chemical stability of vapor-coated 1H,1H,2H,2H-perfluorodecyltrichlorosilane antisticking layers against acetone, acidic piranha, reactive ion etching and UV-assisted nanoimprinting was investigated. To evaluate the behavior of hybrid mold surfaces, flat silica and antireflective chromium-oxynitride surfaces were used. The antisticking layer on both surfaces was highly chemical resistant against acetone. A continuous antisticking layer degradation with a surface free energy increase of 0.9 mN/m per 10 min piranha treatment and 1.2 mN/m per 10 subsequent UV-assisted imprints was found for silica surfaces. On the chromium surfaces, the antisticking layer quality was much lower than on fused silica and degraded much faster. The surface free energy of silane coated chromium surfaces was increased by 2.3 mN/m after 10 imprints and the antisticking layer was completely degraded after a single 10 min piranha cleaning step. The lower antisticking layer quality on antireflective chromium was attributed to the surface itself. Additionally, the high chemical resistance of the vapor coated silane was used to successfully protect the adhesive joints of cost-efficient, adhesively bonded nanoimprint molds from being degraded by acidic piranha during mold cleaning. This can significantly increase the life-time of such bonded molds.

Surface modification of poly(ethylene terephthalate) (PET) by magnet enhanced dielectric barrier discharge air plasma

In order to study the effect of magnet enhanced plasma on polymer surface, a dielectric barrier discharge (DBD) setup with and without magnet is presented and used to modify poly(ethylene terephthalate) (PET) films at atmospheric pressure in ambient air. Surface analysis and characterization of the air plasma-treated PET films are performed using contact angle measurements, surface free energy, Atomic Force Microscopy (AFM) and X-ray Photoelectron Spectroscopy (XPS). The results show that air plasma leads to an obvious decrease in contact angle and increase in surface free energy. And surface wettability of the PET films treated by DBD with magnet is better than that without magnet. AFM images show an increase in surface roughness due to plasma etching. It is shown that O and N elements are introduced onto PET film surfaces as oxygen- and nitrogen-containing functional groups. The oxygen-containing groups can be identified as C O, C O and O C O. Their concentrations of the PET films treated with magnet are more than those treated without magnet. The difference is attributed to more active particles generated in DBD with magnet. Therefore, magnet field plays an important role in improving surface wettability of polymers.

Effect of low-surface-tension EDTA solutions on the wettability of root canal dentin

This study was conducted to evaluate the effect of reducing the surface tension of ethylenediaminetetraacetic acid (EDTA) solutions on the wettability of root canal dentin. Forty-two extracted teeth were sectioned at the crown, and the apical third and remaining mid-root portion was bisected longitudinally. The root halves were embedded in resin blocks. The experimental groups were treated with 17% EDTA, EDTA-T, and REDTA alone or followed by 2.5% NaOCl. Surface free energies of samples were calculated by measuring contact angles. Surface tension measurements of all solutions were performed with pendant drop method. The addition of surfactant to the EDTA solution significantly decreased the surface tension of solutions (P < .01). Combined and single use of experimental solutions and NaOCl significantly decreased the water contact angle and increased the surface free energy of root canal dentin (P < .05). EDTA-T alone or combined with NaOCl also increased surface free energy compared with EDTA solution (P < .05). The use of low-surface-tensioned EDTA compounds alone or in combination with NaOCl increased the wettability of root canal dentin.

Role of interface in dispersion and surface energetics of polymer nanocomposites containing hydrophilic POSS and layered silicates

Three different hydrophilic nanofillers – natural and synthetic layered silicate as well as octaammonium polyhedral oligomeric silsesquioxane (POSS) – were incorporated into polyamide-6 by a solution-mixing method. The surfaces of the resulting polymer nanocomposites were characterized by X-ray diffraction, polarized optical microscopy, Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy and contact angle measurements. All polymer nanocomposites displayed enhancement in surface hydrophilicity as well as increase in surface free energy due to surface enrichment of the nanofillers. The degree of enhancement was found to depend on both nanofiller type and dispersion state. Interfacial interactions in the form of hydrogen bonding played an important role in affecting the dispersion state of the layered silicates. Exfoliated layered silicates caused a larger increase in hydrophilicity than aggregated layered silicate. On the other hand, aggregated POSS molecules were able to induce a large increase in hydrophilicity. Significant spreading of water was also observed on surfaces containing POSS molecules. Surface models have been proposed to explain these phenomena.

Analysis of Influencing Factors on the Structure and Surface Properties of Palygorskite

The relationship between surface properties and water vapor absorption performance was studied according to crystal structure and surface free energy of purified palygorskite. The results show that the unit cell volume of samples increases along with the increase of temperature ranging from 0 to 200 °C, leading to the increase of water vapor absorption. The intensity of diffraction peak, crystal plane spacing and unit cell volume decrease with the increase of the heat temperature ranging from 200 to 800°C, leading to the decrease of water vapor absorption. The intensity of diffraction peak almost disappears when the temperature is over 800°C. The palygorskite turns into non-crystallization, and the new phase of diopside appears. The surface free energy and polarity component increase along with the increase of heat-treatment temperature, and the dispersion component is obviously relevant to water vapor absorption performance.

Surface Characterization of Oxygen Plasma Treated Nano-SiO&lt;sub&gt;2&lt;/sub&gt; Sol-Gel Coating UHMWPE Filaments

UHMWPE filaments have a low surface free energy and therefore often require a modification of their surface properties before any use. Atmospheric pressure plasmas treatment is a convenient and environmentally friendly way to obtain these modifications by introducing new chemical groups at the surface without affecting the bulk properties. This paper studies the influence of nano-SiO2 sol-gel coating pretreatment on atmospheric pressure plasma jet (APPJ) treatment of ultrahigh molecular weight polyethylene (UHMWPE) fibers when a mixture of 100% helium and 1% oxygen used as the treatment gas. The surface properties of the plasma-treated UHMWPE filaments are characterized using contact angle measurements and ATR-FTIR spectroscopy. The UHMWPE filaments show a remarkable increase in surface free energy after plasma treatment. ATR-FTIR spectroscopy of the plasma-treated UHMWPE filaments reveals that plasma treatment introduces oxygen-containing functionalities on the UHMWPE filaments surface leading to the increased surface free energy.

Surface Characterization of Helium Plasma Treated Nano-SiO&lt;sub&gt;2&lt;/sub&gt; Sol-gel Coated UHMWPE Filaments by Contact Angle Experiments and ATR-FTIR

Ultrahigh molecular weight polyethylene (UHMWPE) Filaments has a low surface free energy and therefore modification of their surface properties before any use is often needed. Atmospheric pressure plasmas treatment is a convenient and environment friendly way to obtain these modifications by introducing new chemical groups at the surface without affecting the bulk properties. This paper studies the influence of nano-SiO2 Sol-gel coated pretreatment on atmospheric pressure jet (APPJ) treatment of UHMWPE fibers with helium used as the treatment gas. The surface properties of the plasma-treated UHMWPE Filaments are characterized using contact angle measurements and ATR-FTIR spectroscopy. The UHMWPE Filaments show a remarkable increase in surface free energy after plasma treatment. ATR-FTIR spectroscopy of the plasma-treated UHMWPE Filaments reveals that plasma treatment introduces oxygen-containing functionalities, such as ketones, aldehydes, alcohols and carboxylic acids on the UHMWPE Filaments surface leading to the increase of surface free energy.

Influence of (phospho)lipases on properties of mica supported phospholipid layers

The effect of enzymes: lipase from Candida cylindracea (L Cc ), phospholipase A 2 from hog pancreas (PLA 2) and phospholipase C from Bacillus cereus (PLC) to modulate wetting properties of solid supported phospholipid bilayers was studied via advancing and receding contact angle measurements of water, formamide and diiodomethane, and calculation of the surface free energy and its components from van Oss et al. (LWAB) and contact angle hysteresis (CAH) approaches. Simultaneously, topography of the studied layers was determined by Atomic Force Microscopy (AFM). The investigated lipid bilayers were transferred on mica plates from subphase of pure water by means of Langmuir–Blodgett and Langmuir–Schaefer techniques. The investigated phospolipid layers were: saturated DPPC (1,2-dipalmitoyl- sn-glycero-3-phosphocholine), unsaturated DOPC (1,2-dioleoyl- sn-glycero-3-phosphocholine), and their mixture DPPC/DOPC. The obtained results revealed that the lipid membrane degradation by the enzymes caused increase in its surface free energy due to the amphiphilic hydrolysis products, which may accumulate in the lipid bilayer. In result activity of the enzymes may increase and then break down the bilayer structure takes place. It is likely that after dissolution of the hydrolysis reaction products in the bulk phase, patches of bare mica surface are accessible, which contribute to the apparent surface free energy changes. Comparison of AFM images and the free energy changes of the layers gives better insight into changes of their properties. The observed gradual increase in the layer surface free energy allows controlling of the hydrolysis process to obtain the surfaces of defined properties.

Preparation and Far Infrared Emission Properties of Natural Sepiolite Nanofibers

Sepiolite nanofibers were prepared by high-speed air current superfine technique, using natural sepiolite samples as raw materials. Through characterization by scanning electron microscope (SEM), X-ray diffraction (XRD), dynamic contact angle meter and tensiometer (DCAMT) and Fourier transform infrared spectroscope (FTIR), it was found that the defibered sepiolite nanofibers with an average diameter of about 100 nm and length greater than 9 microm had a better far infrared emitting performance than acid-purified sepiolite as the contrast sample, and the defibering treatment led to the improvement of far infrared emitting performance of sepiolite due to the increase of surface free energy, the increase of infrared active bond vibrations, and the decrease of cell volume caused by the distortion of structural channel.

Effects of Particle Size on Far Infrared Emission Properties of Tourmaline Superfine Powders

Tourmaline superfine powders with different particle sizes were prepared by grinding, superfine ball milling, and high-speed centrifugation. The powders were characterized by scanning electron microscopy, X-ray diffraction, dynamic contact angle meter and tensiometry, and Fourier transform infrared spectrometry. The results show that tourmaline powders exhibit improved far infrared emission properties as the particle size decreases. The increased surface free energy and proportion of the polar component are considered to play an important role for their properties. The spontaneous polarization is increased, and the dipole moment of tourmaline is stimulated to a high energy level more easily for the chemical bond vibration, so that the energy is apt to emit by transition. In the range of 2000-500 cm(-1), the emissivity values of the samples with D50 size of 2.67 microm and 0.2 microm are 0.973 and 0.991, respectively.

Adhesion Characteristics of Carbon Black Embedded Glass/Epoxy Composite

The surface of glass/epoxy composite material was embedded with carbon black which was dispersed in methyl ethyl ketone (MEK) during the curing process to enhance the adhesion strength of the glass/epoxy composite structure. The morphological effect of the carbon black on the surface of composite was observed using scanning electron microscopy (SEM) and atomic force microscopy (AFM). Quantitative chemical bonding analysis with X-ray photoelectron spectroscopy (XPS) was also performed to observe chemical bonding states on the surface. The lap shear strength of the glass/epoxy composite adhesive joints where composite adherends were embedded with carbon black was investigated with respect to the type and amount of embedment. Also, the tensile properties of the carbon black embedded glass/epoxy composites were measured to observe the mechanical degradation of the composite due to the MEK. The surface free energies of carbon black embedded composites were determined from the van Oss–Chaudhury–Good equation to correlate the lap shear strength of the adhesive joints with the surface free energies of composite adherends. From the experimental results, it was found that the carbon black embedment of the composite adherend improved much the bond strength due to the increased surface roughness on nano-scale as well as increased surface free energy.

Bacterial adhesion onto materials with specific surface chemistries under flow conditions

Staphylococcus epidermidis adhesion onto materials with specific chemical functionalities, under flow, was investigated by using surfaces prepared by self-assembly of alkyl silane monolayers on glass. Terminal methyl (CH(3)) and amino (NH(2)) groups were formed by chemical vapor deposition of silanes, at elevated temperature. Carboxyl (COOH) terminated groups were prepared by further modification of NH(2) groups with succide anhydride and positively charged NH(2) groups by adsorption of poly-L: -lysine hydrobromide. Hydroxyl (OH) terminated glass was used as control. Surface modification was verified by contact angle measurements, atomic force microscopy and X-ray photoelectron spectroscopy. A parallel plate flow chamber was used to evaluate bacterial adhesion at various shear rates. Adhesion was found to be depended on the monolayer's terminal functionality. It was higher on the CH(3) followed by the positively charged NH(2), the non-charged NH(2) groups, the COOH and minimal on the OH-terminated glass. The increase in the material surface free energy significantly reduced the adhesion of a hydrophilic bacterial strain, and this is in accordance with the predictions of the thermodynamic theory. However, the increase in the shear rate restricted the predictability of the theory and revealed macromolecular interactions between bacteria and NH(2)- and COOH-terminated surfaces.