Contact Angle Data Research Articles

Predictive modelling for contact angle of liquid metals and oxide ceramics by comparing Gaussian process regression with other machine learning methods

Wettability has a major effect on the performance of the corrosion of ceramic refractory under normal operating conditions. Contact angle measurement is available to characterize the wettability of liquid metals and oxide ceramics. Therefore, it is necessary to develop a contact angle prediction model with generalizability. This work emphasizes on developing a model for predicting the contact angle of a liquid metal with a solid oxide and analyzes the influence of factors affecting the contact angle when contact angle is predicted. In this paper, six contact angle prediction models are developed based on machine learning methods and contact angle data from the previous literature. The comparison between six contact angle prediction models evidences that the gaussian process regression (GPR) model has the best prediction accuracy and reaching 96%. Furthermore, the comparative results indicate that when surface energy of metal, surface energy of oxide, formation free energy of oxide, and bandgap energy of oxide are ignored respectively, the prediction accuracy of the model decreases by 4%, 3%, 1% and 1% respectively.

Hydrophobic Properties of CuO Thin Films Obtained by Sol-Gel Spin Coating Technique-Annealing Temperature Effect

The adhesive characteristics of sol-gel copper oxide (CuO) film surfaces at annealing temperatures ranging from 350 to 550°C were examined in this work. Hydrophobic properties of these oxide film surfaces were studied by contact angle measurements. The surface energy was calculated from contact angle data using harmonic mean method. The structural, morphological and chemical analysis of the samples were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and Fourier transform infrared (FTIR). The increase in annealing temperature induces a reduction in the hydrophilic properties of the films (adhesive properties). The rise in the hydrophobicity of the CuO surface has been claimed to be explained by a change in interfacial tension. The FTIR spectroscopy analysis revealed that the increase in the annealing temperature eliminates activated neutral species (hydroxyl groups) reacting with the surface of the sample responsible for the wettability. SEM analysis showed that the morphology of the samples is nanostructured containing agglomerates of various forms, a few hundred nanometers in size, randomly dispersed across the surface. The enhanced roughness of the produced film is primarily responsible for the increased hydrophobicity of the films. The XRD data reveal that the films are highly textured and that increasing the annealing temperature induces better layer crystallization and confirms the development of copper oxide CuO.

Wettability and interfacial phenomena in the liquid‐phase bonding of refractory diboride ceramics: Recent developments

AbstractJoining and integration technologies are integral to manufacturing of components based on ultrahigh‐temperature ceramics (UHTCs) such as transition metal diborides. Brazing is a particularly attractive joining technique because of its simplicity and versatility, but its use to join the UHTCs demands knowledge of the complex interplay among high‐temperature wettability, interfacial reactions, and chemical and thermoelastic compatibilities. This paper summarizes the research and development activities carried out over the last two decades to characterize the wettability and interfacial phenomena in brazing of refractory diboride ceramics. The contact angle data of various metal alloys on diboride‐based ceramics have been collected and critically evaluated in conjunction with an analysis of the chemistry and structure of the interface to understand the underlying mechanisms and phenomena that govern interface formation. It explores how solid–liquid interactions impact and are impacted by physical, chemical, and mechanical properties of joined materials. It also describes how this knowledge has been successfully utilized to create liquid‐phase bonded diboride‐based joints. The paper concludes with a summary of the current state of the art and highlights integration challenges and future research and technology development needs in the area.

Sliding on snow of AISI 301 stainless steel surfaces treated with ultra-short laser pulses

Surface irradiation of AISI 301 with ultra-short linearly polarized pulses between 247 fs and 7 ps resulted in laser induced periodic surface structures (LIPSS). Scanning electron microscope micrographs taken after the laser treatment show the formation of sub-micrometer sized arrays of nearly parallel ripples slightly differing from each other, depending on the specific treatment adopted. Static contact angle data indicate that LIPSS induce a marked hydrophobic behavior of the treated surfaces. The friction coefficient of laser treated and pristine AISI 301 surfaces gliding on compact snow was compared to that of ultra-high molecular weight polyethylene. The friction coefficients of the laser treated samples are intermediate between those of bare AISI 301 and of UHMWPE. The changes in contact angle and surface morphology of the samples after extensive tribometer tests were tested to investigate the durability of LIPSS.

Linking molecular structures of yeast-derived biosurfactants with their foaming, interfacial, and flotation properties

Yeast-derived bola amphiphiles have attracted growing attention in various industrial sectors as green reagents. However, their physico-chemical properties relevant to mineral separation by froth flotation are poorly explored. To bridge this gap, we studied the foaming, interfacial, and flotation properties of acidic sophorolipid (ASL), acidic glucolipid (GL) and alcoholic glucoside (GS) obtained from strain engineering of the yeast Candida bombicola by molecular editing of the headgroups. Bench-scale flotation testing of a copper sulfide ore showed that ASL can effectively separate copper sulfides (85% recovery at 20% grade), GL is less effective (ca. 60% recovery and 13% grade), while GS is a poor collector. To understand this trend, we studied the interfacial and foaming properties of these three biosurfactants. The surface tension study reveals that, contrary to GS, self-assembly of both ASL and GL at the air–water interface is pH-responsive, suggesting that both the biosurfactants acquire a Π-shape. The dependence of the foaming properties of all the three surfactants on pH and concentration does not correlate with the trends in the static surface tension, suggesting the critical roles of dynamic factors, interfacial elasticity and interfacial viscosity. Hydrophobicity of djurleite (a model copper sulphide) in the presence of the three surfactants was assessed using the contact angle and Hallimond flotation methods. ASL and GL only float the pure mineral at alkaline pH, which is consistent with the contact angle data. In contrast, even though GS does not have a significant effect on contact angle, it floats djurleite in a wide pH range, which is explained by the mechanical entrainment of hydrophilic mineral particles in rich GS foams. Overall, these results demonstrate the potential of carboxylic bola biosurfactants for the recovery of copper sulfides from ores. They also bring new insights into the interfacial and foaming properties of bola biosurfactants, which can assist their introduction into other industries.

The effect of dynamic wetting pressure on contact angle measurements

HypothesisThe drop deposition technique can impact contact angle measurements. We hypothesized that the drop pinch-off, during the traditionally used pendant drop technique, significantly alters the static contact angle. The capillary waves and dynamic wetting pressure generated during the pendant drop deposition are the source for forced spreading, which can be circumvented by alternative liquid-needle drop deposition techniques. ExperimentsTo compare the role of drop pinch-off and resultant dynamic wetting pressure, we meticulously observed and quantified the entire drop deposition process using high speed imaging until the drop attains the static contact angle in both cases, namely pendant drop and liquid needle deposition technique. Conventionally used standard substrates are compared using both techniques and further compared using literature data. The capillary waves and corresponding drop shape variations are analysed for quantifying the dynamic wetting pressure by measuring drop base diameter, contact angle and centre of mass. FindingsWe compared three parameters - drop pinch-off, spreading behaviour and respective static contact angles along with the resultant dynamic wetting pressure for both the techniques, i.e., pendant drop and liquid-needle. For the pendant drop technique we observed a pronounced drop volume dependency of these parameters even though the corresponding Bond numbers are less than unity. In contrast, for the liquid needle there is no such dependency. With a theoretical argument corroborating experimental observations, this work highlights the importance of a well controlled drop deposition, with a minimum wetting pressure, in order to guarantee contact angle data that is independent of drop deposition effects, thereby only reflecting the substrate properties.

Machine Learning Prediction of TiO2-Coating Wettability Tuned via UV Exposure.

Surfaces with extreme wettability (too low, superhydrophobic; too high, superhydrophilic) have attracted considerable attention over the past two decades. Titanium dioxide (TiO2) has been one of the most popular components for generating superhydrophobic/hydrophilic coatings. Combining TiO2 with ethanol and a commercial fluoroacrylic copolymer dispersion, known as PMC, can produce coatings with water contact angles approaching 170°. Another property of interest for this specific TiO2 formulation is its photocatalytic behavior, which causes the contact angle of water to be gradually reduced with rising timed exposure to UV light. While this formulation has been employed in many studies, there exists no quantitative guidance to determine or tune the contact angle (and thus wettability) with the composition of the coating and UV exposure time. In this article, machine learning models are employed to predict the required UV exposure time for any specified TiO2/PMC coating composition to attain a certain wettability (UV-reduced contact angle). For that purpose, eight different coating compositions were applied to glass slides and exposed to UV light for different time intervals. The collected contact-angle data was supplied to different regression models to designate the best method to predict the required UV exposure time for a prespecified wettability. Two types of machine learning models were used: (1) parametric and (2) nonparametric. The results showed a nonlinear behavior between the coating formulation and its contact angle attained after timed UV exposure. Nonparametric methods showed high accuracy and stability with general regression neural network (GRNN) performing best with an accuracy of 0.971, 0.977, and 0.933 on the test, train, and unseen data set, respectively. The present study not only provides quantitative guidance for producing coatings of specified wettability, but also presents a generalized methodology that could be employed for other functional coatings in technological applications requiring precise fluid/surface interactions.

Influence of 10-methacryloyloxydecyl dihydrogen phosphate (MDP) incorporated experimental cleaners on the bonding performance of saliva-contaminated zirconia ceramic.

To assess the efficacy of experimental cleaners containing 10-methacryloyloxydecyl dihydrogen phosphate (MDP) on the saliva decontamination of ceramic and their influence in restoring zirconia's adherence to resin cement. Four hundred sixty alumina-blasted zirconia specimens were categorized into saliva-contaminated and uncontaminated groups which were treated with ceramic primer (P), experimental cleaner 1 (C1), C1 followed by P (C1P), experimental cleaner 2 (C2), and C2 followed by P (C2P). Stainless-steel rods were then attached to the specimens using PanaviaV5 cement (Kuraray Noritake Dental; Tokyo, Japan). Tensile bond strength (TBS) test was performed after 24h and 5000 thermocycling processes. X-ray photoelectron spectroscopy (XPS) analysis and contact angle measurement of the specimen were performed. The TBS data were analyzed by Weibull analysis and three-way ANOVA. Contact angle data were analyzed by two-way ANOVA (α = 0.05). C2P groups showed the highest TBS in all conditions among tested groups. Saliva contamination led to a significant reduction of TBS in primer- and cleaner-treated groups, with no significant impact on C2P. Adhesive failure was predominant in contaminated groups except with the C1P and C2P groups. XPS revealed that a nitrogen peak was observed on contaminated groups but not in primed groups. The contact angle was significantly affected by saliva contamination, the cleaners, and/or ceramic primer usage (p < 0.001). The MDP cleaner followed by the MDP primer protocol may overcome the effect of saliva contamination and improve the resin-ceramic bond strength. It is recommended to use a combination of MDP-containing cleaner 2 and ceramic primer as a chair-side chemical pretreatment for zirconia substrate with or without saliva contamination.

To evaluate and compare the mechanical properties and wetting ability of heat polymerized polymethyl methacrylate resin after reinforcement with halloysite nanotubes and titania nanoparticles

To evaluate and compare the mechanical properties and wetting ability of heat polymerized polymethyl methacrylate resin after reinforcement with halloysite nanotubes and titania nanoparticles. A conventional heat-cured resin (DPI heat cure material) will be used as the matrix component while halloysite (group A) and titania (group B) nanoparticles as a reinforcing agent. Group C specimens will be fabricated with trevalon (Trevalon – HI). The specimens will be stored in distilled water overnight to simulate oral environment before performing the tests for determining the flexural strength (FS) and contact angle (CA). The contact angle data states that Halloysite reinforced PMMA is more hydrophilic. UTM analysis states that Flexure strength of trevalon highest amongst all the three group. Resin reinforced with halloysite had higher contact angle hysteresis hence greater retentive value and wetting ability while travelon had higher flexure strength.

Study of the contact angle of water droplet on the surface of natural K-feldspar with the combination of Ar+ polishing and atomic force microscopy scanning

Wettability is a key property of a reservoir rock, which can significantly affect the distribution and transportation of fluids (gas, oil, water, etc.) in reservoir pores which are constructed with various minerals. As for sandstone reservoirs, quartz and feldspar are the common minerals of the framework. However, the study on the wettability of feldspar is much less than that of quartz probably due to the strong heterogeneity and complex composition of natural feldspar minerals. In this study, a method for measuring the contact angle of water droplet on a natural mineral surface is proposed by combining argon ion polishing technique with atomic force microscopy scanning (Ar+-AFM method). Compared with the traditional optical goniometer measurement, this method can apparently reduce the influence of heterogeneity on the wettability of K-feldspar surface and yield more consistent contact angle data.

Micro-cellular polymer foam supported silica aerogel: Eco-friendly tool for petroleum oil spill cleanup

Flexible micro-cellular open porous 3D polymer foam silica aerogel composites with exceptional oil sorption characteristics were prepared by implanting silica aerogel in the interstices of foam substrates. Silica aerogels were engineered from silane precursors namely tetraethoxysilane (TEOS) and methyltrimethoxysilane (MTMS) adopting economical, energy efficient and scalable ambient pressure drying technique. These flexible composites exhibited outstanding structural ruggedness. The foam-aerogel composites deliver superior hydrophobic characteristics in terms of contact angle data. The aerogel composites recorded an oil uptake of 31.3 g per g of the composite for engine oil and the uptake was very swift. Mechanical squeezing enables near complete oil removal from the composites. The foam aerogel composites displayed superior recyclability features, as first time absorption is retained even after 10 cycles of repeated squeezing and re-absorption operations.

Surface treatment and adhesion approaches on polymer-infiltrated ceramic network

Aim: To evaluate the effect of different surface treatments and adhesive approaches on the microshear bond strength of resin cement to a polymer-infiltrated ceramic network (PICN). Methods: PICN blocks were randomly assigned into 9 groups (n=10): CTRL: no treatment; HF: 5% hydrofluoric acid etching; HF-S: HF + silane; HF-S-A: HF-S + adhesive (Adper Single Bond 2); HF-UA: HF + universal adhesive (Single Bond Universal); SB: sandblasting with 50 μm Al2O3 particles; SB-S: SB + silane; SB-S-A: SB-S + adhesive; SB-UA: SB + universal adhesive. Resin cement microcylinders (Ø = 0.96 mm; height = 1 mm) (RelyX Ultimate) were built upon the PICN surface after roughness and contact angle measurements. Next, microshear bonding tests (μSBS) were performed (0.5 mm/min) after water storage (37ºC, 90 days) and thermocycling (12,000 cycles; 5ºC-55ºC). Failure modes were observed under stereomicroscope. Bond strength data were analyzed by two-way ANOVA/Tukey’s test and t-tests. Kruskal-Wallis/Dunn’s tests were conducted for roughness and contact angle data (α = 0.05). Results: A rougher surface and lower contact angles were observed for Sandblasting. HF-S (18.54 ± 2.03 MPa), SB-S (19.00 ± 1.66 MPa) and SB-UA (18.07 ± 2.36 MPa) provided the highest bond strength values, followed by the other treated groups. The CTRL group resulted in lower bond strength (7.18 ± 2.34 MPa). Conclusion: Hydrofluoric acid etching followed by silane application and sandblasting followed by silane or universal adhesive are useful clinical steps to enhance bonding to PICN. Adhesive applications after HF etching have no advantages in bonding to PICN.

PC12 cells proliferation and morphological aspects: Inquiry into raffinose-grafted graphene oxide in silk fibroin-based scaffold

Peripheral nerves injuries (PNIs) still associated with both clinical and social problems. Accordingly, tissue engineers’ and surgeons’ attentions have been drawn for finding efficient solutions. Herein, scaffolds based on silk fibroin (SF)/raffinose-grafted-GO (S.RafGO) nanocomposite were fabricated. Subsequently, PC12 cells growth in term of number and morphology were investigated on neat SF polymer, SF/GO (S.GO), and S.RafGO scaffolds. Characterization via scanning electron microscopy (SEM) exhibited more fibrous structures with few lamellar nanosheets for S.GO; although, S.RafGO showed extended lamellar with lower fibrous structure. Due to the incorporation of GO and raffinose-GO nanosheets into SF structure, electrical conductivity increased ~30 and 40%, respectively. Water contact angle data revealed that S.RafGO is more wettable than SF and S.GO. Real-time PCR technique detected higher expressions of the β-tubulin, MAP2 genes on S.RafGO scaffolds in comparison with S.GO and the control group. Immunocytochemistry staining studies confirmed the overexpression of neural-specific proteins including nestin, β-tubulin of S.GO, and S.RafGO nanocomposites in comparison with pure SF scaffolds.

Analysis of N-acetyl cysteine modified polydimethylsiloxane shunt for improved treatment of hydrocephalus.

A major cause of hydrocephalus shunt failure is cell adhesion and obstruction of shunt catheter holes. An estimated 50% of pediatric shunts fail in the first 2 years of insertion, decreasing cell attachment and catheter obstruction can prolong the lifetime and effectiveness of the device. From previous studies, it was shown that treatment of the polydimethylsiloxane (PDMS) surface of a standard catheter with an N-acetyl-cysteine (NAC/1-ethyl-3-(3-dimethylanimopropyl)carbodiimide hydrochloride/N-hydroxysuccinimide) layer increases the wettability of the surface and has been shown to decrease cell adhesion. Other studies indicate that NAC's antioxidant behavior induces glutathione and in turn modulates cell inflammatory pathways. The current study explores the longevity of the NAC coating from the surface of the catheter over time and shows its effect on valve function. Using SEM imaging, contact angle testing, and nanodrop spectrophotometry, this release was quantified for shunt samples incubated for 0, 10, 30, 60, and 90 days. Contact angle showed a significant increase in wettability of the surface when shunts were treated with NAC, confirming successful surface modification. Pressure assays determined that if the coating is release it had no detrimental downstream effects, such as on the shunt valve mechanism. SEM imaging revealed slight deformations in surface coating indicative of salt deposition on the modified shunt samples, while nanodrop spectrophotometry and contact angle data trends suggested some discharge of the NAC coating from the catheter surfaces. The effects of NAC on cell activity may transform the way hydrocephalus is treated in the future by increasing the longevity of the shunt to protect from obstruction.

Interfacial improvement of poly (lactic acid)/tannin acetate composites via radical initiated polymerization

A wholly bio-composite based on poly (lactic acid) (PLA) and tannin acetate was successfully prepared via in situ reactive extrusion using dicumyl peroxide (DCP) to improve interfacial adhesion. The composites based on PLA and tannin acetate with high acetylation degree exhibited increased molecular weight as compared with reactive extruded PLA, together with the improvement of Young’s modulus and tensile strength. The rheology results showed that reactive extruded PLA/tannin acetate composites exhibited increased complex viscosity and modulus storage, indicating the strong interfacial adhesion of PLA and tannin acetate. Besides, Glass transition temperature, thermal stability, and crystallinity degree were all enhanced as a result of better interaction by radical initiated polymerization. From contact angle data, free radical extruded composites had a more hydrophobic characteristic compared with PLA, which might be interesting for food packaging application. This approach opens up a pathway to diversify the applications of tannin as a component for bio-composite preparation.

Dynamic contact angle measurements on lubricant infused surfaces

HypothesisEven though lubricant-infused surfaces (LISs) are known to affect the mobility of working fluid depending on the infused lubricant, previous studies have not yet quantified their slippery property. This study proposes the slippery nature of the LIS can be assessed by dynamic contact angles of the working fluid on the LIS and its scaling model. ExperimentsWe measured the apparent dynamic advancing and receding contact angles on a LIS using a modified Wilhelmy plate technique for the first time. Lubricant having different viscosities was infused into the sanded polytetrafluoroethylene surface to fabricate the LIS. The surface was immersed into or withdrawn from an aqueous glycerol-water solution by varying the capillary number and the lubricant viscosity. FindingsThe dynamic contact angles on LIS was found to be sensitive to changes in both the lubricant viscosity and the capillary number. The cube of the dynamic contact angles on the LIS was proportional to θD3~Ca1, which follows a conventional hydrodynamic theory. In addition, the decreasing lubricant viscosity shifted the cube of the dynamic contact angles to high capillary numbers. Our dynamic contact angle data coincided with the prediction from a scaling law derived in this study.

A novel hybrid technique to enhance oil production from oil-wet carbonate reservoirs by combining a magnetic field with alumina and iron oxide nanoparticles

This paper examined a new study into the effect of combined magnetic field and nanoparticles (NPs) on oil-wet carbonate reservoirs. A novel hybrid enhanced oil recovery (EOR) technique was used to investigate the effect of a magnetic field and aluminium oxide (Al2O3) and iron oxide (Fe2O3) nanoparticles (NPs) on oil recovery from Austin chalk, based on measurements of contact angle, surface tension, rock compaction and rock surface charge. An Amott cell with a surrounding magnetic belt was used to perform spontaneous imbibition tests. When oil-wet cores with an extremely low recovery factor (RF) of 2.73% were imbibed with deionized water, the effect of the combination of magnets and alumina was pronounced and an incremental RF of 14.7% was recorded. However, changing the displacing fluid from deionized water to seawater led to a lower recovery of 9.2%, which can be attributed to the poor dispersion of alumina NPs. Adding iron oxide NPs to the displacing fluid in the presence of magnets also resulted in higher recovery factors, with increases of 22.27% and 12.78% observed for deionized water and seawater respectively. The analysis of zeta potential, contact angle and surface tension data suggests that the combined driving mechanisms of alteration in wettability and interfacial forces caused the improvements found in oil recovery from oil-wet carbonate rocks during water-based nanoparticle flooding when exposed to a magnetic field. In addition, concentrations of aluminium oxide and iron oxide NPs were reduced by factors of 40 and 5 respectively compared to previous studies. Hence, this technique offers cleaner EOR, allows the oil industry to optimize oil production with the lowest chemical use by implementing magnets, ultimately increasing revenue in the long term.

Aggregation and transport behavior of goethite colloids as affected by dissolved organic matter and pH: Electrostatic vs. hydrophilic interactions

Wettable surfaces in aqueous media experience hydrophilic repulsion forces, which have been thoroughly examined for interactions between biocolloids. However, there is no systematic assessment yet on the effects of hydrophilic repulsion on aggregation and transport behavior of soil mineral colloids. The aim of this study was to fill that gap in knowledge, with an emphasis on whether hydrophilic or electrostatic forces govern the respective interactions. For that, the interactions of hydrophilic goethite colloids were examined by batch aggregation experiments and colloid breakthrough experiments using columns filled with hydrophilic quartz sand. To induce electrostatic interactions ranging from attractive to repulsive, colloid zeta potential was modified via changes in dissolved organic matter concentration and pH. Classic DLVO and the extended DLVO (XDLVO) theory that includes hydrophilic interaction energies were applied using electrophoretic mobility measurements and sessile drop contact angle data. Results showed that for each case in which hydrophilic repulsion was predicted to be stronger than electrostatic attraction, the latter always controlled the colloid aggregation and transport behavior in the experiment. The likely reason was that the irregular shape and surface roughness of the colloids, as shown by SEM images, rendered the short-range hydrophilic repulsion ineffective, so that the more long-range electrostatic interactions predominated. We conclude that in contrast to biocolloids, hydrophilic repulsion did not have a relevant effect on the interactions between soil mineral colloids. Hence, our study clearly shows that for the aggregation and mobility of soil mineral colloids, soil parameters affecting their surface charge are more important than parameters affecting their wettability.

Data on characterization and performance of aspartic acid functionalized graphene oxide-polysulfone mixed matrix membranes.

Structure and microstructure characterization are very important for determining the membrane hydrophilicity, morphology, porosity, and mechanical properties that affect the membrane separation performance and durability. This article analyzes the morphological differences between graphene oxide (GO) and functionalized graphene oxide (f-GO) based on data from SEM imaging. nalysis of the morphology of mixed matrix membrane (MMMs) through SEM, mechanical properties through DMA and hydrophilicity through contact angle data. This dataset will support the original research article “Mixed matrix membranes containing aspartic acid functionalized graphene oxide for enhanced oil-water emulsion separation” (Abdalla, Wahab and Abdala, 2020; doi.org/10.1016/j.jece.2020.104269). The data reported here also include raw data for stress vs strain measurements, mass recorded during permeation test and pure water fluxes at different pressures for all prepared MMMs.

Transition in the Acid–Base Component of Surface Free Energy of Ice upon the Premelting of Its Second Molecular Bilayer

Molecular disordering of the ice surface occurs below the bulk melting temperature of 273 K, termed surface premelting. The top-most molecular layer begins gradually premelting at 200 K, and has been linked to its low coefficient of friction through an increase in molecular mobility. The second molecular bilayer premelts around 257 K, but no study has linked this transition to a change in any macroscopic phenomena. Here, we show that the thermodynamic work of adhesion between polydimethylsiloxane (PDMS) and ice changes abruptly at 257.0 $\pm$ 0.1 K. Surface-sensitive sum frequency generation spectroscopy shows that there are no molecular level changes at the PDMS surface or the ice-PDMS interface near the transition in adhesion, indicating that the transition arises from changes of the ice surface. Using existing contact angle data in the literature, we show that this transition is due to a decrease in the acid-base component of the surface free energy of ice by 17 $\pm$ 2 mJ/m$^2$ at 257.0 $\pm$ 0.1 K. The change in surface energy provides a possible explanation for a variety of unexplained phenomena seen across the literature including ice adhesion, friction, and the morphology of snowflakes.