Tack Values Research Articles

Preparation and in vitro evaluation of a new fentanyl patch based on functional and non-functional pressure sensitive adhesives.

In this study, some single-layer and double-layer transdermal drug delivery systems (TDDSs) with different functional and non-functional acrylic pressure-sensitive adhesives (PSAs) were prepared. For this purpose, fentanyl as a drug was used. The effects of PSAs type, single-layer and double-layer TDDSs on skin permeation and in vitro drug release from devices were evaluated using a hydrodynamically well-characterized Chien permeation system fitted with excised rat abdominal skin. The adhesion properties of devices such as peel strength and tack values were obtained as well. It was found that TDDS with -COOH functional PSA showed the lowest steady-state flux. Double-layer TDDS displayed a constant flux up to 72 h. In double- and single-layer devices after 1 and 3 h, respectively, drug release followed Higuchi's kinetic model. Formulations with the highest percentage of -COOH functional PSA have displayed the lowest flux. The double-layer TDDSs with non-functional PSA demonstrated the suitable skin permeation rate close to Duragesic(R) TDDS and suitable adhesion properties.

Miscibility and tack of blends of poly (vinylpyrrolidone)/acrylic pressure-sensitive adhesive

In this study, miscibility and tack of blends of poly (vinylpyrrolidone) (PVP)/acrylic pressure-sensitive adhesive (PSA) were evaluated. For this purpose, appropriate amounts of PVP (2–30% w/w) were added to an acrylic PSA to obtain visually homogeneous solution. The resulting solution was evenly applied on a polyethylene terephthalate (PET) film with final specific thicknesses of 10, 40, and 70 μm by using a film applicator and miscibility as well as tack values were evaluated. With the addition of 2% (w/w) PVP the tack value decreased and increased in 5% (w/w) PVP and then continuously decreased up to 30%(w/w). It was found that the tack value was related to miscibility as well as to viscosity and the free functional group such as hydroxyl group of the blend. By the morphological analysis performed through scanning electron microscopy (SEM) and also by the study of thermal analysis using the differential scanning calorimetry (DSC) behavior of blends, it was found that the two distinct phases constituted after adding 5% (w/w) of PVP. This resulted in the acrylic PSA forming the continuous phase, and by increasing the concentration of PVP a dispersed phase was developed. The dispersed phase has a higher viscosity than the continuous phase and therefore cannot wet the adherent and hence result in lowering the tack values.

The effect of polymer molecular weight and crosslinking reactions on the adhesion properties of microsphere water-based acrylic pressure-sensitive adhesives

In this work, the effect of polymer molecular weight and crosslinking reactions on the end-use properties of the microsphere water-based acrylic pressure-sensitive adhesives (PSA) is presented. Polymer molecular weight and polymer microstructure were regulated using different chain transfer agent (CTA) concentrations and by addition of a diacrylic monomer (MM). The adhesion properties of the synthesized PSAs were characterized via measurements of tack, peel adhesion and shear strength. The results of experiments have shown that the kinetics of suspension polymerization is relatively independent on the amount of CTA and MM. The amount of gel phase in the adhesive was reduced with increasing amount of CTA agent, and gel phase amount may be considered as a function of polymer molecular weight. With a combination of CTA and MM was possible to regulate the amount of formed gel phase in the adhesive, as well sol phase molecular weight. All of the measured adhesion properties strongly depend on molecular weight of the synthesized polymer and on the amount of gel phase. For adhesives synthesized solely with addition of CTA, tack decreased with lower polymer molecular weight and consecutively also with lower amount of gel phase. The same trend was also observed for peel strength measurements, whereas a cohesive failure was observed for adhesives with low amount of gel phase. A maximum value for tack and shear strength was observed at 80wt% of gel phase. In case of syntheses with a combination of CTA and MM (amount of gel phase in range from 70 to 80wt%), tack values were distributed in quite narrow range. On the other hand, peel strength values decreased in comparison with adhesives synthesized only with CTA, regardless to the equal amount of gel phase. Poor shear strength was observed for all adhesives synthesized by combination of CTA and MM.

A Modified Apparatus for Testing the Probe Tack of Pressure-Sensitive Adhesive Materials

A modified probe-tack test is described in which a special device is capable of detecting the first contact between the probe and a pressure-sensitive adhesive (PSA) and to determine this contact as the initial dwell time. In tests using viscoelastic PSA materials (hydrogels), this modified device gives results which differ significantly from those obtained with conventional probe-tack testers. In particular, when tack values are plotted against dwell time, the modified tester reveals a regime of sigmoid low-energy tack and then a transition to the normal power-law high-energy tack. This transition behavior was studied as a function of crosshead velocity, compression pressure, adhesive rheology and adherend surface roughness. The practical implication is that far more information can be obtained from this modified device than from conventional probe-tack testers. The modified machine and methodology should prove particularly valuable as an experimental tool and for quality-control tests in the manufacture of PSA products, particularly soft and tacky viscoelastic substances.

Anti-tack Action of Polyvinylpyrrolidone on Hydroxypropylmethylcellulose Solution.

The anti-tack action of polyvinylpyrrolidone (PVP) on hydroxypropylmethylcellulose (HPMC) solution was elucidated using a probe test method. The influence of PVP of varying molecular weights at various PVP concentrations and solution temperatures on the tackiness of HPMC solution was studied. The viscosity, surface tension, cloud point and solution spectroscopy of HPMC solutions and glass transition temperature of HPMC films, with and without PVP, were investigated. The tackiness of HPMC solutions in response to the addition of PVP, at different concentrations of HPMC and using HPMC with varying contents of hydroxypropyl/methoxyl substitution, was also evaluated. PVP is a commonly used binder and adhesive. However, it reduced the tack of the HPMC solution when used at low concentrations, without affecting the state of hydration of HPMC. Lower molecular weight PVP was more effective as an anti-tack agent owing to suitable hydrodynamic size to intersperse among the HPMC chains. The degree of reduction in tack values was more pronounced for HPMC that showed a greater extent of interaction between polymer chains such as when high concentration of HPMC or low solution temperature was employed. This indicated that the tack reduction property of PVP relied on its ability to interact with the HPMC chains. The profile of reduction in tack values was affected by the contents of HPMC substitution and was a result of net reduction in the extent of hydrogen bonding between HPMC chains. It was significantly correlated to the changes of viscosity and surface tension of the HPMC solutions but not to the glass transition temperatures of the polymers prepared as solid films. The results suggested that the anti-tack action of PVP was attributed to its ability to interact with HPMC chains in the aqueous medium and consequently to reduce the extent of HPMC-HPMC bonding.

Testing the rolling tack of pressure-sensitive adhesive materials. Part II: Effect of adherend surface roughness

A novel method and custom-made apparatus for testing the rolling tack of pressure-sensitive adhesives (PSAs) and related materials were developed to measure bonding and debonding processes. The combined effects of adherend (probe) surface roughness, longitudinal load, and dwell time on bond-formation performance of five different tacky materials chosen from various application areas were studied. These materials included synthetic PSAs (acrylic tape and the hydrocolloid dressing, Granuflex®), water-remoistenable adhesive (CENTRAL®), edible wheat flour dough, and a static cling vinyl (PENSTIC®). Tack-rolling velocity curves were analyzed to study bonding and debondong processes. Each of the tested materials showed different tack behavior in response to varying probe roughness, external load, and velocity (dwell time). Surface wetting and mechanical interlocking were proposed as the mechanisms governing tack in most tested PSAs. Acrylic PSA tested on a smooth probe over a velocity range of 0.12-2.12 m/s showed higher tack values than on a rough one. A significant reduction in tack was due to restricted bond formation. Similarly, tack of Granuflex® to a smooth model skin surface showed higher values than to a rough skin surface. CENTRAL® showed typical cohesive failure when tested on silicone-coated paper. Interfacial failure and short-term bonding accounted for good tack performance on porous paper. Dough tested with aluminum probes showed cohesive failure similar to that of CENTRAL® at velocities higher than 0.2 m/s where the tack was independent of probe surface roughness. PENSTIC® adhered only to smooth glass where the tack values tended to decrease with increased velocity. Bonding and debonding processes of the various tacky materials were clearly affected by adherend surface roughness, longitudinal load, and dwell time, and could be successfully analyzed using our novel proposed method and apparatus.

Acrylate Copolymer/Ultraviolet Curable Oligomer Blends as Pressure-sensitive Adhesives

For the blends of acrylate copolymer [poly(2-ethylhexyl acrylate-co-acrylic acid); P(2EHA-AA)] with ultraviolet (UV) curable oligomer [urethane acrylate oligomer; UAO], pressure-sensitive adhesive (PSA) properties, such as peel adhesion, probe tack, and holding power were examined. The values of peel adhesion and probe tack of the P(2EHA-AA)/UAO blends were dramatically reduced by UV irradiation. On the other hand, all blends had a high holding power even if these blends were cured by UV irradiation. The mechanism of reduced PSA properties was investigated via dynamic mechanical properties, DSC, and dynamic contact angle (DCA). The peel adhesion decreased monotonically with increasing storage modulus, E′, and loss modulus, E″, for all non-UV and UV-cured blends. Since modulus values and glass transition temperatures, Tg, of these blends after UV irradiation were higher than those of these blends before UV irradiation, we judged that the reduced peel adhesion and probe tack values were caused by the modulus increase and the Tg increase due to UV irradiation. In other words, the ability of the deformation energy of UV-cured blends to influence the adhesive tests was reduced by the curing process. The DCAs of non-UV-cured blends were the same as those of UV-cured blends. We presumed that the segment mobility of the polymer chain on the surface did not contribute to the reduced peel adhesion and probe tack values.

Influence of nonrubber constituents on tack of natural rubber. I. At very short times of contact (pendulum test)

The effect of nonrubber constituents such as proteins and lipids on tack of natural rubber (NR) was studied. Tack or adhesion at short contact time was determined for contact between crosslinked rubbers and glass plates. Various types of natural rubber, with or without nonrubber constituents, were prepared. Synthetic polyisoprene was used as a reference because of its chemical similarity. In this work, the impact pendulum test was carried out to study very short contact times tc of the order of milliseconds. The results show an increase of tack energy with tc for all the rubbers. This is attributed to an increase in true contact area with time and to a modification of the interfacial energy. Furthermore, the natural rubber without lipids and also polyisoprene exhibited the highest tack values while whole natural rubber remained always the less tacky. These results cannot be explained by differences in either the bulk viscoelastic properties of the crosslinked materials or their overall surface energy. The presence of a thin layer of varying composition at the surface of the rubbers appears to be the essential factor that affects the tack properties of the crosslinked materials. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 78: 1486–1494, 2000

Effects of miscibility on probe tack of natural‐rubber‐based pressure‐sensitive adhesives

Natural rubber (NR) was blended in various ratios with 29 kinds of tackifier resins, which were prepared from rosin, terpenes, and petroleum. Miscibilities of all the blend systems were illustrated as phase diagrams in our previous articles. From these blend systems, we selected 7 systems having typical phase diagrams [completely miscible, completely immiscible, and lower critical solution temperature (LCST) types] and carried out measurements of probe tack. Probe tack values were measured at various rates of separation and temperatures to obtain master curves. In the case of miscible pressure sensitive adhesives (PSAs) at the condition of measurement, the peak position in the master curve of probe tack shifted to the lower velocity (higher temperature) as the tackifier content increased. On the contrary, immiscible PSAs had much smaller probe tack values than miscible ones and did not give manifest shift of peaks. © 1998 John Wiley & Sons, Inc. J. Appl. Polym. Sci. 70: 771–776, 1998

Segregation Behavior Found in Poly(2-ethylhexyl acrylate)/Poly-(vinylidenefluoride-co-hexafluoro acetone) Blends

The surface and bottom compositions of poly(2-ethylhexyl acrylate) (P2EHA)/poly-(vinylidene fluoride-co-hexafluoro acetone) [P(VDF-HFA)] blends were investigated by XPS analysis. In these blends, the enriched P(VDF-HFA) layer was observed from the top surface to a few nm depth, while the P2EHA component segregated at the bottom (the surface in contact with release liner). The probe tack values of the bottom side were remarkably larger than those of the surface side for the P2EHA/P(VDF-HFA) blends because the characteristic segregation structure was formed. We expected that the P2EHA/P(VDF-HFA) blends could be utilized as a non-backing pressure sensitive adhesive (PSA) tape. The effects of the film thickness of the blends and the molecular weights of P2EHA on the segregation structure were also examined. We thought that segregation behavior found in P2EHA/P(VDF-HFA) blends was caused by several factors, such as surface tension, miscibility, density, and rate of solvent casting.

NMR spectroscopy, polymer motion, and “Tack” of model printing inks

AbstractPolymer motion in solution and in model printing inks (as measured by NMR spectroscopy) was compared to the “tack” or tensile stress developed in the splitting of thin fluid films. For model inks based on polyisobutene, at constant pigment content, increasing the polymer content caused polymer motion to slow down, and caused the tack to increase. At constant polymer content, increasing the pigment level had much less effect on polymer motion. At 20% pigment content, tack values were little different from those of the corresponding polymer solutions. This suggests that the tensile stress developed in an ink film as it splits is related to the motion of its polymeric ingredients, but is much less dependent on the concentration of dispersed solid pigment.

Evaluation of Tack Behaviour of Coating Solutions

AbstractA new apparatus was constructed and a method was suggested to measure the tackiness of tablet coating solutions. The method is simple, rapid, reproducible and it can be used to fulfil either researchal or control investigations.Water solutions/or dispersions/of seven different coating materials widely used in the industry were investigated. On the basis of experimental results it was concluded that increase in concentration of solution led to increase in tackiness. By the evaluation of the data gained from the tack values vs. concentration curves it was possible to choose the concentration of coating solution which proved to be the most favorable from the aspects of both producing requirements and tackiness.The construction and the evaluation of the so called “Tack curves” showing the change of tackiness in time. The data of these curves add further useful informations to the optimization of the production parameters of coating.

Adhesive tack and green strength of EPDM rubber

AbstractMeasurement of tack of EPDM (ethylene‐propylenediene terpolymer) rubber with natural rubber (NR) of four different molecular weights, styrene‐butadiene rubber (SBR), butadiene rubber (BR), bromobutyl rubber (BIIR), and polychloroprene rubber (CR) was done over a range of rates of testing, contact times, and temperatures of contact. The effect of different additives, namely carbon black, phenol‐formaldehyde resin, coumarone‐indene resin, and methyl methacrylate is also reported. Green strength of all the rubbers was measured. Tack strength increases with increase in contact time for all the rubbers. Adhesive tack between EPDM and low‐molecular‐weight NR is much higher than that between EPDM and NR of high molecular weight. Tack strength of EPDM with BIIR is the highest among the tack values obtained for synthetic rubbers. The adhesive tack between EPDM and natural/ synthetic rubber passes through a maximum when plotted against temperature of contact. It increases with testing rate. All these phenomena could be explained in terms of interdiffusion of rubber chains under different conditions and solubility parameter of two contacting rubbers. It was observed that tack strength varies with (contact time)1/2 and (rate)1/2 in accordance with the reptation theory. Phenol‐formaldehyde resin (PF) or coumarone‐indene (CI) resin in EPDM improves the tack strength quite significantly. The resin in the NR phase does not have a marked effect. The presence of carbon black decreases adhesive tack strength between EPDM and NR. The surface of EPDM, however, becomes smoother with the addition of the additives. Peel tests and commercial tack tests give similar results in the tack strength between EPDM/NR and EPDM/SBR.

Studies on tack of pressure–sensitive adhesive tapes

AbstractIt has been found that tack values of pressure‐sensitive adhesives are dependent on the surface energies for adherends. The parabolic curves with maxima are obtained from the plots of tack values versus critical surface tensions for the substrates. The maximum occurs at the region where the two surface tensions are almost similar. On the other hand, tack is measured as a dynamic value indicated as the force necessary to deform the adhesive mass. To explain why the tack values is controlled by the surface character of the adherend, a mechanism is proposed for adhesive bond breaking. Primarily, bonding occurs by wetting the surface with adhesive. When the adhesive bond breaks by external force, unbonding proceeds from the viscoelastic deformation of the adhesive mass around the wetted spots on the surface of the adherend. As the total area of wetted spots is determined by surface energy, the tack value is dependent on the critical surface tension of the adherend.

A Tackmeter for Rubber Testing

Abstract In the hand test for tackiness commonly used, two surfaces of the compound are pressed together for a short time and are then separated, the force required for separation giving a measure of the tackiness of the compound. The magnitude of the separating force depends largely on such factors as the load applied to the contacting surfaces, the duration of application ef the load, and the surface area in contact, but none of these factors can be controlled within reasonable limits of reproducibility. Moreover, the results of this test can be recorded only in rather general terms such as “fair”, “good”, so recorded results may vary from one operator to another and they depend very largely on the experience of the individual operator. It thus becomes evident that in any investigation which calls for the evaluation of the tack properties of a fair number of different compounds, some method of test is required in which the personal element is entirely eliminated. In the course of an investigation into the tackiness of GR-S compounds, Busse, Lambert, and Verdery (J. Applied Physics 17, 376 (1946)) designed an apparatus which enabled the measurement of tack values to be put on a quantitative basis, and the principles of the apparatus reported by them have been embodied in the tackmeter described below.