Surface Energy Analysis Research Articles

A review of the analysis and characterisation of polymeric glass fibre sizings

Glass fibre reinforcements form the backbone of a composites industry. Possibly the most critical component involved in the manufacture of glass fibres and their composites is the fibre sizing. Yet because of the intense level of secrecy surrounding size formulations there are few who have more than a superficial understanding of sizings. Composite developers and researchers have a growing need for practical tools which can assist with the understanding of the nature and role of sizings on the glass fibres which reinforce their composites. This work reviews some of the most relevant articles from the widely dispersed literature around the analysis and characterisation of these polymeric sizings. The review covers the analysis and characterisation of the polymeric sizing layer on the glass fibre surface using high vacuum surface analysis techniques, thermal analysis, atomic force microscopy based techniques, surface energy analysis, infrared methods, and combined multiple analysis techniques. The conclusions highlight the fragmented nature of the knowledge base on sizings and the lack of reliable and reproducible reference materials on which to build real progress in the understanding of this critical technology.

Generation and Characterization of an Atmospheric-Pressure Plasma Jet (APPJ) and Its Application in the Surface Modification of Polyethylene Terephthalate

An atmospheric-pressure plasma jet (APPJ) has a lot of applications in recent years such as in material processing, surface modification, biomedical material processing, and thin film deposition. APPJ has been generated by a high-voltage power supply (0-20 kV) at an operating frequency of 27 kHz. This paper reports the generation and characterization of APPJ in argon environment and its application in the surface modification of polyethylene terephthalate (PET). The plasma jet has been characterized by electrical and optical methods. In order to characterize the plasma jet, electron density and electron temperature have been determined. The surface roughness of the untreated and plasma-treated PET samples was characterized by contact angle measurement, surface energy analysis, Fourier transform infrared (FTIR) spectroscopy, scanning electron microscopy (SEM), and atomic force microscopy (AFM).

Improvement of hydrophilicity of polyamide using atmospheric pressure plasma jet

Atmospheric Pressure Plasma Jet (APPJ) has many applications in material processing such as surface modification and biomedical material processing. APPJ has been generated by a high voltage power supply (0-20 KV) at an operating frequency of (20-30) 23 kHz. This paper reports the generation and characterization of APPJ in Argon environment and its application in the surface modification of polymeric materials. The discharge has been characterized by optical and electrical methods. In order to characterize the plasma jet, its electron temperature and electron density has been determined by optical emissions spectroscopy. The surface properties of the untreated and plasma treated Polyamide (PA) samples were characterized by contact angle measurement and surface energy analysis.
 BIBECHANA 17 (2020) 133-138

Exploring intermolecular contacts in multi-substituted benzaldehyde derivatives: X-ray, Hirshfeld surface and lattice energy analyses.

Crystal structures of six benzaldehyde derivatives (1–6) have been determined and their supramolecular networks were established by an X-ray crystallographic study. The study has shown that the compounds are linked by various intermolecular interactions such as weak C–H⋯O hydrogen bonding, and C–H⋯π, π–π and halogen bonding interactions which consolidate and strengthen the formation of these molecular assemblies. The carbonyl group generates diverse synthons in 1–6via intermolecular C–H⋯O hydrogen bonds. An interplay of C–H⋯O hydrogen bonds, and C–H⋯π and π–π stacking interactions facilitates the formation of multi-dimensional supramolecular networks. Crystal packings in 4 and 5 are further generated by type I halogen⋯halogen bonding interactions. The differences in crystal packing are represented by variation of substitution positions in the compounds. Structure 3 is isomorphous with 4 but there are subtle differences in their crystal packing. The nature of intermolecular contacts in the structures has been studied through the Hirshfeld surfaces and two-dimensional fingerprint plots which serve as a comparison in constructing different supramolecular networks. The intermolecular interaction energies are quantified utilizing theorectical calculations for the title compounds and various analogous structures retrieved from the Cambridge Structural Database (CSD). Also intermolecular interactions for the molecular pairs are exctrated from respective crystal structures. Essentially, there are some invariant and variable intermolecular contacts realized between different groups in all six structures. The ab initio DFT total lattice energy (ETot) calculations showed a direct correlation with thermal strengths of the title compounds.

The Effect of Different Plasma Treatments on the Surface Properties and Bond Strength between Lithium Disilicate and Resin Cement.

To evaluate the roughness, surface energy, and the bond strength of lithium disilicate yielded by two different types of nonthermal plasma (NTP), oxygen- or argon-based, compared to the conventional method. Ninety-three lithium disilicate (IPS e.max Press) samples were divided into 3 groups: HF (hydrofluoric acid group); ONTP (oxygen-based NTP group); ANTP (argon-based NTP group). Surface energy and roughness analyses were performed before and after surface treatment, and bond strength testing was performed before and after 5000 thermocycles. Scanning electron microscopy (SEM) was used to characterize the surface treatments. Data were submitted to ANOVA and Bonferroni's test with statistical significance set at 5%. The ONTP group presented the highest surface energy values, followed by ANTP and HF. In addition, the ONTP group had higher surface roughness. SEM revealed exposed lithium disilicate crystals in the HF group, but a homogeneous film coverage in both NTP groups. Regarding bond strength, ANTP presented statistically significantly higher values than the other groups before thermocycling, and statistically significantly lower values than the other groups after thermocycling. The HF and ONTP groups presented statistically similar values after thermocycling. The bond strength of resin cement to lithium disilicate obtained after oxygen-based NTP was comparable with that obtained after conventional hydrofluoric acid treatment.

Surface treatment of eucalyptus wood for improved HDPE composites properties

ABSTRACTIn this study, the effect of Eucalyptus globulus wood (UE) used as a filler (5–20% w/w) on the physical and thermal properties of high‐density polyethylene (HDPE) composites was evaluated. To improve the compatibility with HDPE, the wood was modified (TE) using crude glycerol derived from biodiesel production. The addition of 20% (w/w) of UE or TE led to more rigid and durable composite materials compared to neat HDPE (about 50 or 100% increase in tensile strength, respectively). Composites also revealed 55–75°C higher temperatures at maximal degradation rates. The advantageous behavior of TE over UE in composites was attributed to the improvement of surface morphology of modified wood and it is better compatibility with the HDPE as revealed by surface energy analysis. The changes in wetting behavior of HDPE and ensuing HDPE‐TE composites (contact angles of ca 72 and 80°, respectively) explain the matrix‐filler interactions. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020, 137, 48619.

Preparation of (3-mercaptopropyl)trimethoxylsilane film on brass and its corrosion resistance in natural seawater

Preparation of 3-mercaptopropyl)trimethoxylsilane (PropS-SH) film on brass surface and its corrosion resistance performance were investigated by surface energy analysis, Fourier transform infrared reflection (FT-IR) spectroscopy and electrochemical measurements. The results indicated that the generation of PropS-SH sialne film on brass was based on spontaneous reactions to produce Cu-S, Zn-S bond and Si-O-Si bonds. When the brass substrate was covered with the prepared PropS-SH silane film, the dezincification coefficient of brass decreased from 4.45 to 0.47. The PropS-SH silane film was able to minimize the dissolution of both Cu and Zn, improving the corrosion resistance of brass in natural seawater.

First-principles investigation of β-Ge3N4 loaded with RuO2 cocatalyst for photocatalytic overall water splitting

Abstract β-Ge3N4 loaded with nanoparticulate RuO2 as a cocatalyst is the first successful non-oxide photocatalyst for overall water splitting. To get an insight into the working mechanism of this particular photocatalytic system, we have calculated geometrical structures of low-index surfaces for β-Ge3N4. Analysis of surface energies indicates that the most preferentially exposed surface is (100). The band gap of surface is narrower than that of bulk due to the dangling bonds. Dissociative water adsorption on (100) surface is thermodynamically favorable. The adsorption behavior of (RuO2)n (n = 2, 3, and 4) clusters on the β-Ge3N4(100) surface has been explored. It is found that all the clusters bind to (100) surface strongly by forming interfacial bonds so that the adsorptions are exothermic processes. The calculation on density of states for β-Ge3N4(100) surface loaded with (RuO2)n clusters reveals that photo-induced electrons tend to accumulate on (RuO2)n clusters and holes tend to stay in β-Ge3N4. Based on the theoretical indication of Type-II staggered band alignment, we have proposed that in photocatalytic water splitting reaction, oxygen evolution reaction is inclined to occur on the surface of β-Ge3N4 while hydrogen evolution reaction is apt to occur on (RuO2)n clusters. In a word, loading RuO2 nanoparticles as a reduction cocatalyst benefits the charge separation in β-Ge3N4. Furthermore, attaching (RuO2)n clusters onto β-Ge3N4(100) surface results in the redshift of absorption edge and the increase of absorption intensity. Our calculations have reasonably explained the experimental observation on the decomposition of water into H2 and O2 after loading RuO2 cocatalyst in β-Ge3N4 photocatalyst.

Influence of a light-activated glaze on the adhesion of Streptococcus sanguinis to the surface of polymers used in fabrication of interim prostheses.

This study aimed to investigate the adhesion of Streptococcus sanguinis to the surface of interim prostheses that were treated or not treated with a light-activated glaze, and subjected or not subjected to a thermocycling procedure. 36 specimens of each resin were divided into 4 groups: heat-activated acrylic resin; chemically-activated acrylic resin; bis-acryl composite resin (Protemp; 3M ESPE); and bis-GMA (Charisma; Heraeus Kulzer). Half of the specimens underwent application of glaze and the other half underwent mechanical polishing. Specimens were randomly distributed into groups (N=9) with and without thermocycling (2000 cycles). Surface energy, roughness and microbiological analyses were performed. Groups treated with glaze showed lower roughness when compared with the same groups without glaze treatment, before and after thermocycling, except for the bis-acryl groups after thermocycling. Surface energy values were higher in the groups treated with glaze, except the bis-acryl group before and after thermocycling. After thermocycling, the values of bacterial adhesion decreased numerically, with the exception of the chemically-activated acrylic resin group treated with glaze and the heat-activated acrylic resin group without glaze treatment. The application of glaze and the thermocycling do not influence, in a statistically significant manner, the bacterial adhesion on polymer surfaces.

Classification of the Morphologies and Related Crystal Phases of III–V Nanowires Based on the Surface Energy Analysis

Zincblende-wurtzite polytypism in III–V nanowires has been of great interest for a long time. However, full understanding and control over the crystal phase is still lacking. Here, we propose a model for the morphologies and related crystal phases of vapor–liquid–solid III–V nanowires by considering the minimum surface energies of different side wall facets as a function of the droplet contact angle. On the basis of the recent experimental data and earlier theoretical calculations of the surface energies, a simple classification of the possible growth modes is presented. It shows that the wurtzite phase forms in vertical nanowires at intermediate contact angles whereas the zincblende phase is predominant for vertical or inverse-tapered nanowires with a truncated top at larger contact angles. The small stable contact angle corresponds to faulted wurtzite–zincblende intermix. Pure zincblende phase is possible for even smaller contact angles only in the kinetic growth regimes. The wurtzite and zincblende dom...

Growth process and grain boundary defects in Er doped BaTiO3 processed by EB-PVD: A study by XRD, FTIR, SEM and AFM

The study of density of grain boundary defects and grain shape was conducted for Erbium doped Barium Titanate (BTE) thin films, which were deposited on Si(100) and Si(100)-Au substrates by electron beam physical vapor deposition (EB-PVD). The crystallite as well as grain size show strong dependence on thermal annealing. Analysis of surface morphologies revealed variations of growth, after thermal annealing process, in films deposited on Si(100) and Si(100)-Au. In films deposited on Si(100) and Si(100)-Au, the root mean square (RMS) roughness value increased from 1.95 to 6.33 nm and 1.73 to 12.9 nm, respectively. These values correspond to 3.2% and 3.7% of the deposited thickness, which is quite low in comparison to the film thickness. Diameters of cavities are observed more significant in films deposited on Si(100)-Au, which increased from 35 to 250 nm. Moreover, the evolution of growth also revealed changes in the surface morphology via surface energy analysis. The results also revealed that chemisorption and physisorption by grain boundary in Si(100)-Au substrate, makes the cavities hydrophilic. These observations are fundamentally important for understating the mechanism of formations of hydrophilic surfaces and changes in their properties owing to the interdiffusion and diffusion effects by the grain boundary. Furthermore, shape of the grains on the surface and the effects of density of grain boundary defects are discussed.

Dropwise Condensation on Multiscale Bioinspired Metallic Surfaces with Nanofeatures.

Nonwetting surfaces engineered from intrinsically hydrophilic metallic materials are promising for self-cleaning, anti-icing, or condensation heat transfer applications where the durability of commonly applied hydrophobic coatings is an issue. In this work, we fabricate and study the wetting behavior and the condensation performance on two metallic nonwetting surfaces with varying number and size of roughness tiers without the need for further hydrophobic coating procedure. On one hand, the surface resembling a rose petal exhibits a sticky nonwetting behavior as drops wet the microscopic roughness features with consequent enhanced drop adhesion, which leads to filmwise condensation. On the other hand, the surface resembling a lotus leaf provides super-repellent nonwetting behavior prompting the continuous nucleation, growth, and departure of spherical drops in a dropwise condensation fashion. On a lotus leaf surface, the third nanoscale roughness tier (created by chemical oxidation) combined with ambience exposure prompts the growth of drops in the Cassie state with the benefit of minimal condensate adhesion. The two different condensation behaviors reported are well supported by a drop surface energy analysis, which accounts for the different wetting performance and the surface structure underneath the condensing drops. Further, we coated the above-mentioned surfaces with polydimethylsiloxane, which resulted in filmwise condensation due to the smoothening of the different roughness tiers. Continuous dropwise condensation on a hierarchical bioinspired lotus leaf metallic surface without the need for a conformal hydrophobic coating is hence demonstrated, which offers a novel path for the design and manufacture of noncoated metallic super-repellent surfaces for condensation phase change applications, among others.

Fabrication of super-tough ternary blends by melt compounding of poly(lactic acid) with poly(butylene succinate) and ethylene-methyl acrylate-glycidyl methacrylate

Herein, we describe the fabrication of novel super-tough ternary blends by simple melt compounding of poly(lactic acid) (PLA) with poly(butylene succinate) (PBS) and ethylene-methyl acrylate-glycidyl methacrylate (EGMA). The occurrence of reactions between the above three constituents was evidenced by mixing torque and Fourier transform infrared spectroscopy analyses and resulted in improved interfacial adhesion. Moreover, surface energy analysis indicated that EGMA was selectively localized at the PLA-PBS interface, and the cryofracture morphologies of as-prepared samples indicated that the inclusion of EGMA improved the compatibility between PLA and PBS phases. Compared to virgin PLA, the ternary blend containing 10 wt% PBS and 12 wt% EGMA exhibited a 32 times higher impact strength (98 kJ/m2), an only 44% loss of tensile strength (38 MPa), and superior stretchability (elongation at break = 460%). The observed property improvements were ascribed to in situ reactions between PLA, PBS, and EGMA and to the formation of elastic graft copolymers at phase boundaries. Ultimately, comparison of as-prepared samples with previously reported blends demonstrated that the former exhibited superior toughness and comparable stiffness, revealing that our work opens new avenues to expand the applications of PLA-based biodegradable products.

Lewis acidity controlled heme catalyst for lithium-oxygen battery

Despite their high theoretical energy density, lithium-oxygen (Li−O2) batteries suffer from limited cyclability originating from poor charging efficiency. In an effort to overcome this critical issue, a variety of catalysts have been introduced, but much room still remains for further advancement in catalyst design. By benchmarking hemoglobin in red blood cells that carry oxygen at a well-defined center of the molecular cage, herein, we report heme as an air-cathode catalyst with iron (Fe) active sites. Furthermore, the coordination of electron-withdrawing ligands, such as thiocyanate (SCN) and azide (N3), to the Fe center enhances its Lewis acidity to weaken the binding of oxygen intermediates (O2∗) towards more facile decomposition of the main discharging product (Li2O2). Density functional theory calculations and surface energy analysis of Fe coherently support the advantageous role of the ligand engineering in enhancing the reversibility of a Li−O2 battery.

The effect of fibre sizing on the modification of basalt fibre surface in preparation for bonding to polypropylene

In this study, the effect of fibre sizing on the modification of basalt fibres in preparation for use with a polypropylene matrix (PP) was investigated. Fibres were coated by the manufacturer with a standard available epoxy (EP) sizing and four experimental PP focused sizings (PPs1-4). Fibre with no sizing was produced to act as a control. The surface topography of sized fibre was analysed by SEM and AFM, indicating that PP sized fibres displayed a more inhomogeneous coating of the fibre. Furthermore, PP sizing resulted in an increase in AFM measured roughness by ∼360%, translating to a 12.5% increase in surface area, over both unsized and EP fibres. Scratching of the fibre surface revealed, that in general, the coating thickness of PP was ∼30 nm thicker than EP sizing despite the same application parameters. XPS revealed that the sizing in all cases adhered to the fibre surface with an increase in potential reactive sites present on PP sized fibres. Analysis of fibre surface energy showed that the overall surface energy of fibres remained similar but the use of PP focused sizing resulted in a decrease of the polar component. Overall, this investigation shows that sizing has a significant effect on the fibre’s surface: changing its topography and chemistry and hence, has an evident potential for increased mechanical and chemical bonding. This was further confirmed by single fibre fragmentation testing which highlighted that sizings PPs2-4 increase the interfacial shear strength by up to 117% compared to non-sized fibres.

Weakened foreign body response to medical polyureaurethane treated by plasma immersion ion implantation

Modern polyurethane elastomers are suitable materials for human implants. However, the immune system of an organism recognizes the polyurethane as a foreign body. A medical polyureaurethane, based on polyether, 2,4-toluenediisocyanate and aromatic diamine was treated by 20 keV nitrogen ions. The polyureaurethane surface was subsequently investigated by atomic force microscopy, electron spin resonance spectroscopy, Fourier transform infrared attenuated total reflection spectroscopy, wettability and surface energy analysis to observe the surface structure transformations associated with the ion implantation. The protein covalent attachment on the modified surface was observed. Endothelial cell attachment and proliferation showed preferences of the modified surface. Polyureaurethane samples were implanted into rats for 5 months. Histology data showed that the immune reaction to the modified polyureaurethane was weaker and the capsule wall is thinner for the modified polyureaurethane, than for the untreated polyureaurethane.

Dynamic wetting of an occlusion after droplet impact

This paper investigates how and under which conditions the lamella of an impacting droplet is punctured by the presence of a small occlusion. Better understanding the conditions which lead to the rupture of the lamella is critical to produce defect free coating layers in the context of spray coating, for example. An analytical model based on surface energy analysis is proposed to obtain the critical thickness below which the liquid layer above the occlusion is unstable and lamella rupture occurs. Furthermore, we have developed a three dimensional multiphase lattice Boltzmann code to confirm the surface energy analysis and study the influence of key parameters like size of the occlusion, impact velocity and wettability of substrate on hole formation. Results show that a hole is more likely to appear as the diameter of the occlusion, the impact velocity, and the hydrophobicity of the surface increase.

On the detection of carbon fibre storage contamination and its effect on the fibre\u2013matrix interface

Contamination caused by inappropriate carbon fibre (CF) storage may have an impact on their end use in reinforced composite materials. Due to the chemical complexity of CFs it is not easy to detect potential contaminants, especially at the early stage during manufacturing and handling. In this paper, X-ray Photoelectron Spectroscopy (XPS), Fourier Transform Infrared (FTIR) spectroscopy and Surface Energy Analysis (IGC-SEA) were used to assess the surfaces of CFs stored in polyolefin zip-lock bags for possible contamination. Only after over 2 months in-bag storage, was XPS capable of detecting a minor increase in nitrogen on the CF surface while FTIR revealed the presence of fatty acid amides and fatty acids, both associated with the storage media. However neither of these techniques were sensitive enough to show significant evolution of the amount of contamination as a function of storage time. In contrast, IGC-SEA distinguished surface energy differences between CFs before and after storage. These differences were found to change as a function of storage time, which were attributed to increases in contamination amounts. Single fibre fragmentation tests indicated that the surface contamination had potential to disrupt the fibre-matrix interface. These findings provide a new method for assessing the surface contamination of CFs with potential application to other materials.

Alignment of liquid crystal molecules on self-assembled monolayer with fluorinated alkyl chain at different deposition time

We demonstrated a homeotropic liquid crystal (LC) alignment state on fluorinated self-assembled monolayers (FSAMs) deposited by gas-phase method as a function of deposition time. The gas-phase method to deposit FSAMs was simple process and cost-effective. Contact angle data and surface energy analyses of the FSAMs showed that film formation occurs, and showed a correlation with the homeotropic alignment of LC molecules on the FSAMs. Stable LC alignments on FSAMs were achieved at deposition time over 60 min. In addition, high transparency and thermal stability of FSAM further enhanced its possibility as a LC alignment layer.

Quantifying the surface properties of enzymatically-made porous starches by using a surface energy analyzer

The behavior of starch during processing and its performance in products is influenced by the surface energetics/structure of the constituent particles. This work investigates the effect of enzymatically-produced porous maize starch particles on their energetic surface properties using inverse gas chromatography-based surface energy analysis (SEA). Three modified maize starch samples treated with amylase (AM), glucoamylase (AMG) and cyclodextrin-glycosyltransferase (CGT), were used for the study. The dispersive surface energy varied from 36.71 (native) to 43.34 mJ/m2 (AMG < CGT < AM). Enzyme catalysis resulted in porous starches with a more acidic (AMG) and a more basic (AM) surfaces. CGT exhibited similar acid-base balance as native starch but with higher concentration of active sites on the surface. This is the first study on the surface energy of enzymatically-treated porous starch materials using SEA, revealing significant information regarding the surface interactions that can affect performance of food and pharmaceutical products.