Surface Free Energy Values Research Articles

Preparation and characterization of surface grafting polymer of ZrO2 membrane and ZrO2 powder

Asymmetric alumina support zirconia (ASZ) supported poly (vinyl acetate) (PVAc) membranes were prepared. Vinyltrimethoxysilane (VTMS) was selected as a silane coupling agent. Polymer layer was successfully prepared on VTMS silylated ASZ membrane by vinyl acetate free radical graft polymerization. The physicochemical characteristic of ZrO2 powders and ASZ membranes were evaluated by various analytical methods: XRD, SEM-EDS, BET, FTIR, TGA, AFM, and contact angle. The surface free energy (SFE) values of the modified membranes were determined by the Owens-Wendt method, the contact angle measurements of glycerol and water were also carried out. Surface roughness increase as graft percentage of free radical graft polymerization increase. However, the water contact angle results show that surface wettability has no definite dependence on surface roughness (AFM). The process of surface grafting was characterized by FTIR and TGA analytical techniques. The results have proved that the VTMS and PVAc chains were successfully grafted onto the ZrO2 surface. The main parameters affecting grafting percentage, namely reaction temperature, reaction time, and monomer concentrations, were investigated experimentally.

Deposition of calcium phosphate coatings using radio frequency magnetron sputtering of substituted β-tricalcium phosphate targets

The influence of magnesium and/or strontium substitutions on the deposition rate of P-TCP was investigated. Pure β-TCP, Mg-β-TCP, Sr-β-TCP and Mg/Sr-β-TCP targets were used for the coating formation. It was shown that strontium substitutions in the structure of β-TCP target increase the deposition rate of coatings. Magnesium substitutions, on the contrary, decrease this parameter. It makes it possible to increase the deposition rate of coatings formed by radio frequency magnetron sputtering without any negative effect on coatings properties. It was demonstrated that all coatings formed by radio frequency magnetron sputtering of β-TCP targets were calcium-rich. The methods of AFM and SEM revealed that coatings under study were characterized by various morphologies. Magnesium-containing coatings (Mg-β-TCP and Mg/Sr-β-TCP) had the lower value of nanohardness than other ones. All coatings were characterized by the higher value of surface free energy than titanium substrate. The coatings formed by sputtering of β-TCP, Mg-β-TCP, Sr-β-TCP had approximately the same value of this parameter.

Preparation of photocatalytic thin films with composition dependent wetting properties and self-healing ability

This paper presents the preparation of a multifunctional coating with triplet photoreactive, superhydrophobic and intelligent self-healing properties. Beside the structural and morphological behaviors of the hybrid thin films consist of fluoropolymer matrix and Ag-TiO2 photocatalyst particles, the wetting properties were also studied by static (Θ) and dynamic water contact angle measurements. The photoactivity of layers was evidenced both at solid/gas (S/G) and solid liquid (S/L) interfaces. The surface roughness (Rq = 3.7 ± 0.9 μm to 15.2 ± 1.2 μm) and thus the wetting properties and apparent surface free energy values (γstot) of the layers were adjustable from superhydrophilic (Θ = 0°; γstot = 70.2 mJ m−2) to superhydrophobic properties (Θ = 150.9°; γstot = 13.1 mJ m−2). At S/G interface the photoactivity of the layers was increased with the Ag-TiO2 photocatalyst content, however, at S/L interface the photocatalytic properties were tailored by the wetting of the films: 90% of the apolar SUDAN IV dye was photodegraded, while the aqueous Methylene Blue dye was not decomposed due to the inadequate surface adsorption. Moreover, it was also presented that the ambient moister catalysed hydrolysis/self-condensation reaction of the hydrophobic dodecyltrichlorosilane (DDSiCl3) molecules resulted self-assembled micro-protrusions on the surface of low energy photoreactive film and this mechanism resulted self-healing superhydrophobic surfaces with photocatalytic properties.

Construction and calibration of a goniometer to measure contact angles and calculate the surface free energy in solids with uncertainty analysis

Here, we present the construction and calibration of a low-cost goniometer to measure contact angles by the sessile drop method. Besides, we propose a simple and fast method to calculate the uncertainty in the determination of the surface free energy (SFE) and its polar and dispersive components through the Owens-Wendt model and tested it by using two testing liquids. The goniometer performance and the SFE uncertainty were determined on two polymers: polytetrafluorethylene (PTFE) and polyoxymethylene (POM), by using water and methylene iodide. The values of contact angle measured were used to calculate the SFE and its components with their errors. The SFE values obtained for PTFE were 17.57–17.91 mJ/m2, with a relative error lower than 5.5%, whereas those for POM were 42.80–43.23 mJ/m2, with a relative error lower than 4.3%. Both the SFE values and the errors were in the range of those previously reported. Based on the mathematical analysis of the uncertainty propagation in the determination of SFE, we concluded that the uncertainty is minimized when the testing liquids are an apolar liquid and water.

Evaluation of the effect of saliva contamination and cleaning methods on the surface free energy and shear bond strength of resin cements to zirconia ceramics

Objective: This study was designated to evaluate the effect of saliva contamination and cleaning methods on the surface free energy and the shear bond strength of resin cement to zirconia ceramics. Materials and Methods: A total of 80 samples were copy milled (CAD/CAM) from Zirconia blank. The samples were randomly divided into (4) groups (n=20) according to method of cleaning. Group 1 (control): No saliva contamination,Group 2: The samples cleaned with distilled water,Group 3: The samples cleaned with ivoclean, Group4:The samples cleaned with re-sandblasting. Each group was subdivided into 2 subgroups according to the type of adhesive resin cement (Multilink Speed and RelyX Ultimate) used (n=10). Each subgroup was further subdivided into two divisions according to the type of test (surface free energy and bond strength) performed (n=5). One-way analysis of variance ANOVA test and Tukey’ post hoc test were done for comparing variables. Results: The control groups record the lowest mean contact angle value (25.81°±1.76°) and the highest mean surface free energy value (107.57mN/m). While the group washed with water revealed the highest mean contact angle value (39.04°±0.68°) and the lowest mean surface free energy value (98.58 mN/m). Regarding shear bond strength the results showed that the highest shear bond strength value was recorded for the control group (14.33±1.98& 13.73±1.33 MPa), for Multi-link speed and Rely-X ultimate cement respectively , followed by re-sandblasting group, followed by ivoclean group, while the lowest shear bond strength value was recorded for the group washed with water (10.9±0.53& 8.22±0.85 MPa). However, regardless of the cleaning protocol groups, Multi-link speed cement recorded a higher mean shear bond strength value than RelyX Ultimate cement. However these difference was statistically non-significant except for the group washed with water (p=0.0003) as indicated by unpaired t test. Failure modes for all groups were evaluated, failure modes was either adhesive, cohesive or mixed, with frequency ranging from 20 to 40% for each type of failure. The group washed with water showed that allof cases of failure were of the adhesive type in both cement (100%). Conclusion: Cleaning of the contaminated ceramic surface before adhesive cementation is an indispensable step in order to achieve a strong bond. Moreover, the removal of surface contaminants by sandblasting and Ivoclean paste can be considered efficient cleaning methods for zirconia surfaces

Forming nanostructured surfaces through Janus colloidal silica particles with nanowrinkles: A new strategy to superhydrophobicity

Proper nano-structuring coupled with low surface energy properties is exploited to obtain super-hydrophobic surfaces. A biomimicking hierarchically structured coating upon a material surface is obtained by depositing Janus nano-structured wrinkled colloidal particles. The morphology of the surface is thus ruled by different scales: the size of the wrinkles (few tens of nanometer), particle radius (several hundreds of nanometer) and interparticle distance. Janus wrinkled silica particles have one side exposing hydroxyl groups while the other side is partially silanized with dichlorodimethylsilane. To obtain these Janus particles, wax colloidosomes with surface covered by starting rough particles were successfully prepared. The exposed surface of rough wrinkled silica particles was then silanized, thus obtaining a Janus structure. The Janus character was prooved in different manners: the simple so called “visual test”, through Energy Filtered Transmission Electron Microscopy (was proven in different EFTEM) and by further functionalization with polypropylene grafted maleic anhydride (PPgMA).A glass microscope slide was covered by drop casting the particles obtaining super-hydrophobic features of the surface characterized by a high water contact angle (149°) and, more interestingly, by a very low water contact angle hysteresis (CAH = 2°) and roll-off angle (ROA = 1.8°). Superhydrophobicity is confirmed by the very low values of apparent surface free energy estimated with the OWRK (Owens-Wendt-Rabel e Kaelble) method. SEM and AFM analyses prove the multiple scale hierarchical roughness, from nano to micro size, that resembles the one present at the surface of the lotus leaves.

WETTING PROPERTIES OF CHITOSAN-MODIFIED AND PLASMA-TREATED PEEK SURFACES

In this paper, the wettability of chitosan/phospholipid (1,2-dipalmitoyl-sn-glycero-3-phosphocholine – DPPC), chitosan/lipid (cholesterol – Chol) and chitosan/protein (cyclosporine A – CsA) films on air plasma activated polyetheretherketone (PEEK) plates was studied. The layers were prepared using the solution spreading technique and their surface wetting properties were determined based on the measurements of the advancing and receding contact angles of water, formamide and diiodomethane. Moreover, based on the contact angle hysteresis model of Chibowski, values of total surface free energy were estimated. Significant changes in PEEK polarity were observed after plasma activation and modifications with Ch/DPPC, Ch/Chol and Ch/CsA layers. These molecules modulate the chitosan film surface by changing the type and magnitude of interactions, which is revealed in the values of surface free energy. These results may be important for the development and implementation of highly biocompatible bone substitution polymers coated with chitosan film with anti-fungal and anti-bactericidal properties. Those systems based on chitosan may also carry and release biologically active substances which could be relevant in the new generation of drug delivery systems.

Influence of inhibitors on the adhesion of SRB to the stainless steel in circulating cooling water.

Influence of the surface characteristics of three stainless steels (SS304, 316L and 317) and presence of scale inhibitors on adhesion kinetics of sulfate reducing bacteria (SRB) in circulating cooling water, were investigated by evaluating surface free energy, adhesion kinetic constants in a parallel plate flow chamber. Results show that the surface free energy values of SS317, SS316L and SS304 are -31.69, -24.18 and -13.92 mJ m-2, respectively. SS317 surface had higher surface hydrophobicity than SS316L and SS304. In the process of bacteria cells adhesion onto SS surfaces, electrostatic interaction for SS is slightly more than hydrophobic interaction. The number of adhering bacteria and the adhesion kinetic constants are different on the three types of stainless steel. The adhesion kinetic constants for SS317 and 316L are greater than that for SS304, which are 0.0354, 0.0282 and 0.0190 min-1, respectively. Scale inhibitors of hydrosy ethyl fork phosphonic acid (HEDP) and phosphono butane-1, 2, 4-tricarboxylic acid (PBTCA) have a certain influence on the initial adhesion of bacteria cell and adhesion kinetics constants are reduced in the presence of HEDP and PBTCA.

The plasma pretreatment influence on corrosion behavior of Ion Vapor Deposition (IVD) of aluminum coating

PurposeThe purpose of this study is to investigate the effect of plasma pretreatment on the corrosion and adhesion behavior of Al coating deposited on iron steel by ion vapor deposition (IVD).Design/methodology/approachAr plasma sputtering was carried out for 0, 5, 10 and 15 min, and then IVD Al coating was performed. Surface free energy measurements were conducted on the plasma-sputtered surfaces. Cross-sectional observations were carried out on the coating/substrate interface by using scanning electron microscopy. Corrosion resistance of the deposited films was characterized using potentiodynamic polarization curve test and electrochemical impedance spectroscopy (EIS).FindingsResults demonstrated that surface free energy values were increased by increasing the sputtering time before coating process. The corrosion current density of the IVD Al coating deposited after 15 min Ar plasma pretreatment is three orders of magnitude lower than that of steel ST37 substrate. The EIS tests confirm the excellent anticorrosive properties of the Al-coated specimens.Originality/valueWith the increase in the plasma pretreatment time, coating adhesion would ameliorate because of the presence of plasma, which makes substrates a better place for Al ions to set and prevent any gap between coatings and substrates. This fact can be attributed to an increase in the surface free energy and reduction of contact angle of substrate exposed to plasma pre-treatment.

Impact of surface tension of wastewater on biofilm formation of microalgae Chlorella sp.

The organic matter and surfactants in wastewater may cause variations in the surface tension of wastewater (STW) ranging between ∼40 and ∼70 mJ·m−2. This study focused on the influence of STW on microalgae biofilm formation. A theoretical analysis was first conducted, and then microalgae biofilm formation on hydrophilic and hydrophobic substrata in liquid and real wastewater with different surface tensions was studied. The results demonstrated that STW affected microalgae biofilm formation remarkably. When the surface tension of liquid medium (γlv) was approximately equal to the average value of surface free energy of microalgae and substrata, biofilm formation reached the minimum. Microalgae biofilm formation on a hydrophilic surface first decreased (from ∼2200 to ∼1500 cells/mm2) and then increased (from ∼1500 to 3100 cells/mm2) with the decrease in γlv (from ∼70 to ∼40 mJ·m−2), whereas biofilm on a hydrophobic surface continued to decrease (from ∼2500 to 1000 cells/mm2).

Effects of Manufacturing and Finishing Techniques of Feldspathic Ceramics on Surface Topography, Biofilm Formation, and Cell Viability for Human Gingival Fibroblasts.

Feldspathic ceramic restorations can be obtained by different techniques (stratification or computer-aided design/computer-aided manufacturing [CAD/CAM] blocks) and finishing procedures (polishing or glaze application). This study evaluated the effects of techniques and finishing procedures on surface properties, biofilm formation, and viability of human gingival fibroblasts (FMM-1) in contact with these materials. Ceramic specimens were obtained through a stratification technique (Vita VM9) and from CAD/CAM blocks (Vita Blocs Mark II; both Vita Zahnfabrik) and their surfaces were finished by polishing (ceramisté diamond rubbers + polishing paste; "p" subgroups) or glaze spray application + sintering ("g" subgroups). Roughness (Ra and RSm parameters) and surface free energy (SFE) were measured. Early biofilm formation of Streptococcus mutans, Streptococcus sanguinis, and Candida albicans was evaluated by counting colony-forming units (CFU). MTT (3-[4.5-dimethyl-thiazol-2-yl-]-2.5-diphenyl tetrazolium bromide) cytotoxicity test evaluated cellular viability for the growth of FMM-1 after 24 hours and seven days of contact. Scanning electron microscopy (SEM) and three-dimensional optical profilometry were performed to qualitatively analyze the surface. Data were analyzed by analysis of variance, Tukey test, and t-test (all α=0.05). Polished samples presented lower roughness (Ra, p=0.015; RSm, p=0.049) and higher SFE ( p=0.00). Streptococci had higher CFU in all groups, but the CFU of C albicans was lower for polished samples. Biofilm formation was influenced by the interaction of all factors ( p=0.018), and the materials showed no cytotoxicity to FMM-1 growth. Polishing resulted in the lowest values for surface roughness and higher SFE values. Polished ceramics showed less C albicans adherence while the adherence of Streptococci was greater than C albicans in all conditions.

The influence of X-rays on the stability of selected properties of polyethylene

The evaluation of a degradation process of polyethylene (PE) in in vitro conditions under the influence of X-rays (X) and an in-cubation in two solutions simulating the environment of a living organism (SBF – simulated body fluid) was carried out. A dose corresponding to 10 standard X-ray pictures of the skeletal system as well as Ringer's and saline solutions at 40°C were used in the study. The paper presents the results of the influence of the 12-month studies on the selected surface properties of the material: surface wettability and abrasiveness. The value of surface free energy (SFE) was determined on the basis of the wetting angle measurements. The conductivity of the incubation fluids was also analyzed. The obtained results indicate that the adopted dose of X-ray radiation has no significant effect on the wettability of the surface of polyethylene. The nature of the surface layer of polyethylene did not change as a result of the 12-month incubation and remained hydrophilic. For the samples incubated in both immersion fluids, a decrease in surface free energy (SFE) was observed. For both the irradiated material and the control group, no significant changes in the mass of the samples and the conductivity of the incubation fluids were found, which indicates the stability of polyethylene. However, the abrasion value increased by approximately 26%. With the passage of the incubation time, a decrease in the value of this parameter was observed for the polyethylene subjected to radiation. No significant changes were found for the control group.

Synthesis of biofunctional coating for a TiZr alloy: Surface, electrochemical, and biological characterizations

This study formed a biofunctional coating for a Ti15Zr alloy to improve the surface characteristics, the electrochemical behavior, and the biological properties of this implant material. Ti15Zr discs (15 mm in diameter × 1 mm thickness) were obtained in three versions: machined, SLA®-treated (control groups), and modified by plasma electrolytic oxidation (PEO) (experimental group). Surface features such as topography, composition, surface roughness, surface free energy, and hardness were assessed. Electrochemical tests were conducted with body fluid solution (pH 7.4). The albumin protein adsorption was measured by the bicinchoninic acid method, and the adhesion of Streptococcus sanguinis was determined. The surface treatments modified the material’s topography. SLA promoted surface roughness higher than that of the other groups, whereas PEO surfaces presented the highest values of hardness and surface free energy. PEO increased the polarization resistance and the corrosion potential, and decreased capacitance and corrosion current density values. In addition, plasma treatment improved the albumin adsorption without being favorable to biofilm adhesion. PEO appears to be the most promising alternative for Ti15Zr alloys, since it improved surface characteristics and electrochemical behavior, as well as enhancing the adsorption of albumin on the material surface with fewer tendencies to bacterial adhesion.

Early Response of Fibroblasts and Epithelial Cells to Pink-Shaded Anodized Dental Implant Abutments: An In Vitro Study.

This research aimed to assess whether pink-shaded anodized surfaces could enhance the adhesion of soft tissue cells compared with untreated machined titanium surfaces. Two types of Ti-Al-V titanium samples were prepared: machined titanium (Ti) and anodized titanium (AnoTi). The microstructure was studied by means of a scanning electron microscope. X-ray photoelectron spectroscopy (XPS) was carried out as well. The wetting properties were investigated by the sessile drop technique with water and diiodomethane. To investigate the biologic response in vitro, the epithelial cell line HaCaT and the fibroblastic cell line NHDF were used. Cell adhesion, morphology, and proliferation were evaluated. The microstructure of the tested surfaces was irregularly smooth for both types of samples with no relevant morphologic differences. The XPS and HR-XPS performed on the AnoTi samples confirmed the presence of Ti, O, and C, along with Ti oxides. Following the optical contact angle measurements, the anodization process induced a slight transition toward the hydrophobic regime. Consequently, the surface free energy values differed significantly between the anodized and the machined samples. Anodized Ti significantly increased the adhesion and proliferation of both epithelial cells and fibroblasts when compared with the pristine Ti controls. Compared with the clinical standard, anodized surfaces could enhance the adhesion of the two major cell types within the peri-implant soft tissues, which makes pink anodization a promising option for implant dentistry.

Influence of Application Time and Etching Mode of Universal Adhesives on Enamel Adhesion.

To investigate the influence of application time and etching mode of universal adhesives on enamel adhesion. Five universal adhesives, Adhese Universal, Bondmer Lightless, Clearfil Universal Bond Quick, G-Premio Bond, and Scotchbond Universal, were used. Bovine incisors were prepared and divided into four groups of ten teeth each. SBS, Ra, and SFE were determined after the following procedures: 1. self-etch mode with immediate air blowing after application (IA); 2. self-etch mode with prolonged application time (PA); 3. etch-and-rinse mode with IA; 4. etch-and-rinse mode with PA. After 24-h water storage, the bonded assemblies were subjected to shear bond strength (SBS) tests. For surface roughness (Ra) and surface free energy (SFE) measurements, the adhesives were simply applied to the enamel and rinsed with acetone and water before the measurements were carried out. Significantly higher SBS and Ra values were obtained with etch-and-rinse mode than with self-etch mode regardless of the application time or type of adhesive. Although most adhesives showed decreased SFE values with increased application time in self-etch mode, SFE values in etch-and-rinse mode were dependent on the adhesive type and application time. Etching mode, application time, and type of adhesive significantly influenced the SBS, Ra, and SFE values.

Adhesion and Early Colonization of S. Mutans on Lithium Disilicate Reinforced Glass-Ceramics, Monolithic Zirconia and Dual Cure Resin Cement.

Monolithic zirconia and glass ceramics are increasingly used in implant crowns. Limited data is available on bacterial adhesion and early biofilm formation on these materials. Four different materials were investigated: (1) Lithium disilicate glass-ceramics (LDS), (2) Fully stabilized zirconia (FSZ), (3) Partially stabilized zirconia (PSZ), and (4) Dual curing cement (DCC). The materials' surfaces were characterized with spinning disc confocal microscopy and by water contact angle and surface free energy (SFE) measurements. For the adhesion tests the materials were rolled in suspensions of Streptococcus mutans. Early biofilm formation was studied on the materials and allowing the biofilms to form for 24 h. S. mutans cell counts were determined by plate culturing. ANOVA and post-hoc Tukey's tests (p⟨0.05) were used for statistical evaluation. The LDS surfaces were clearly hydrophilic with the highest SFE value (p⟨0.001). For S. mutans adhesion, the ranking of the materials from lowest to highest was: LDS = FSZ ⟨ DCC ⟨ PSZ (p⟨0.05). No significant differences among the materials were noticed in biofilm formation. LDS has lower S.mutans adhesion than other materials examined in this study, but the difference was not reflected in early biofilm formation.

Study on the synthesis of new blocked polyisocyanates as crosslinking agents for hydrophobic polyurethane powder clear coatings

Abstract Blocked polyisocyanate crosslinkers for powder coatings were synthesized using isophorone diisocyanate (IPDI), formic acid and e-caprolactam. They were modified with fluorinated polyols. Two kinds of catalyst i.e. dibutyltin dilaurate and dibutyl phosphate for the synthesis were employed. The chemical structures of these compounds were confirmed by nuclear magnetic resonance (NMR) spectroscopy. The molecular mass distribution was investigated using gel permeation chromatography (GPC). During the thermal degradation of modified polyisocyanate three main stages of decomposition can be seen. The degradation of modifier occurs in the last decomposition stage at temperature range of 375 – 500 °C, which is confirmed by coupled TG-FTIR technique. Additionally, polyurethane powder coating systems composed of polyester resin and modified blocked polyisocyanate, were examined. The cross-linked polyurethane powder coatings resulted in improved thermal stability and surface properties i.e. lower roughness and surface free energy values as well as higher hydrophobicity, oleophobicity, gloss, scratch and abrasion resistance.

Effects of argon low temperature plasma on PLA film surface and aging behaviors

The main objective of the study is to investigate the effects of argon low temperature plasma on PLA film properties and determine the effect of storage time on the value of surface free energy and its polar and dispersive components. The effects of the different treatment time on PLA film are analyzed. The contact angle measurements and subsequent SFE calculation have been done immediately after the treatment as well as after 1, 7, 14, 30, and 60 days. Furthermore, the chemical changes have been studied using XPS and surface topography has been analyzed with confocal microscopy. The results show a significant improvement in the film wettability. This improved wettability is manifested by a 40% reduction in the contact angle of the water and a 43% increase in SFE values. Moreover, the highest values of surface free energy are noted after 6 min plasma treatment, but results for shorter treatment time such as 2–4 min are more stable over time. The SFE increases from 40.1 mJ/m2 to 57.4 mJ/m2 after 6 min activation, however after 60 days storage SFE value decreases to 44.8 mJ/m2, compared to decrease from 56.7 mJ/m2 to 50.1 mJ/m2 for 2 min activation.

Abstracts from The Aerosol Society Drug Delivery to the Lungs 27 Edinburgh International Conference Centre Edinburgh, Scotland, UK December 7-9, 2016.

The aim of this project was to explore drug deposition mechanisms on the aluminium canisters employed with Pressurised Metered Dose Inhalers (pMDIs). The investigation explored the influence of various surface treatments, applied to the canisters, to drug deposition phenomena. Physicochemical characterisation of the canisters was performed after the application of different surface treatments to explore potential links between: surface topography, surface chemical composition, total surface energy, and drug caking appearing on the canister walls. The coating treatments which were tested were; Fluorinated Ethylene Propylene (FEP) lacquer, vapour deposited Parylene and a 3M-proprietary, fluid-applied fluorosilane. Anodisation was also explored both with and without additional fluorosilane treatment. A number of surface physicochemical characterisation techniques were employed, namely; Scanning Electron Microscopy (SEM), X-Ray Photoelectron Spectroscopy (XPS) and Contact Angle (CA) analysis. The data from these analyses were correlated with those from a Drug Deposition test employing drug quantification by UV spectrophotometry. The results obtained indicated a direct correlation of drug deposition on canister walls to the total surface free energy. The lowest total surface free energy values and lowest deposition values were seen when the 3M-proprietary fluorosilane coating was applied as the final treatment. In this case a surface free energy value of 15.73 mN/m and a percentage drug deposition of 7% compared to the calibration can, were achieved.

Effect of cocoa fat content on wetting and surface energy of chocolate

The aim of this study was the quantification of the effect of the cocoa fat content on the wetting characteristics and surface free energy of different chocolate compositions. On the market, there are many different types of chocolate products which differ both in the sensory and physico-chemical properties together with their raw material compositions and the contents of the individual components. This paper focuses on differences in the use of different types of fats - cocoa butter, milk fat, equivalents or cocoa butter substitutes in chocolate products. Studied samples (prepared at Carla, Ltd. Company) were followed by static contact angles of wetting measurements and by calculated surface free energies. There were investigated the effects of fat content and used fat types of the chocolate products on their final wettabilities and resulting surface free energies. There was found a linear dependence between total fat content and the surface free energy, which was gradually increasing with increasing fat content. Additionally, there were performed TG DTG and NIR spectrometry measurements of the tested materials with the aim to determine the melting point of studied fats used, as well as to determine and identify individual fat components of chocolate products which may affect the resulting value of surface free energy.