Hiroshi Mizumachi

Miscibility and pressure-sensitive adhesive performances of acrylic copolymer and hydrogenated rosin systems

Relationship between the miscibility of pressure-sensitive adhesives (PSAs) acrylic copolymer/hydrogenated rosin systems and their performance (180° peel strength, probe tack, and holding power), which was measured over a wide range of time and temperature, were investigated. The miscible range of the blend system tended to become smaller as the molecular weight of the tackifier increased. In the case of miscible blend systems, the viscoelastic properties (such as the storage modulus and the loss modulus) shifted toward higher temperature or toward lower frequency and, at the same time, the pressure-sensitive adhesive performance shifted toward the lower rate side as the Tg of the blend increased. In the case of acrylic copolymer/hydrogenated rosin acid systems, a somewhat unusual trend was observed in the relationship among the phase diagram, Tg, and the pressure-sensitive adhesive performance. Tg of the blend was higher than that expected from Tgs of the pure components. This trend can be due to the presence of free carboxyl group in the tackifier resin. However, the phase diagram depended on the molecular weight of the tackifier. The pressure-sensitive adhesive performance depended on the viscoelastic properties of the bulk phase. A few systems where a single Tg could be measured, despite the fact that two phases were observed microscopically, were found. The curve of the probe tack of this system shifted toward a lower rate side as the Tg increases. However, both the curve of the peel strength and the holding power of such system did not shift along the rate axis.

Effects of miscibility and viscoelasticity on shear creep resistance of natural-rubber-based pressure-sensitive adhesives

Natural rubber (NR) was blended in various ratios with 29 kinds of tackifier resins. Miscibilities of all the blend systems were illustrated as phase diagrams. From these blend systems, we selected 8 systems having typical phase diagrams (completely miscible, immiscible, lower critical solution temperature [LCST] types) and carried out measurements of shear creep resistance (holding power). Holding time was recorded as required time for the pressure-sensitive adhesive (PSA) tape under shear load to completely slip away from the adherend. Holding time of miscible PSA systems tended to decrease as the tackifier content increased. This is attributable to a decrease in plateau modulus of the PSA with increasing tackifier content. There was rather large difference in holding time by tackifier among the miscible PSA systems; the reason for this is also considered to be a difference in plateau modulus. Holding time of an immiscible PSA system scarcely changed by tackifier content. But in another immiscible system, holding time tended to increase with increasing tackifier content. In fact, in the case of immiscible PSAs, the effect of tackifier content on holding time was different from tackifier to tackifier. This may be caused by difference in extent of phase separation.

Effects of miscibility on peel strength 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. 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 peel strength. Peel strength was measured at the angle of 180° at 20°C over the wide range of pulling rates. In the case of pressure-sensitive adhesives (PSAs), which showed phase diagrams of the completely miscible or LCST type, the peak positions in the pulling rate–peel strength curves shifted to the lower velocity as the tackifier content increased. On the contrary, completely immiscible PSAs had a smaller peel strength than miscible ones and did not give manifest shift of peaks. In most of the adhesives, the fracture mode changed from cohesive failure to interfacial failure (between adhesive and adherend), slip-stick failure, and glassy failure (between the tape and adhesive) as the pulling rate increased.

Miscibility and fracture energy of probe tack for acrylic pressure‐sensitive adhesives: acrylic copolymer/tackifier resin systems

The relationship between the miscibility of acrylic pressure-sensitive adhesive (PSA) and the fracture energy (W) (Jm−2) of the probe tack was investigated, wherein the master curve of W was compared with that of the maximum force (σmax) (gf) of the probe tack. It was ascertained that W of acrylic PSA was closely related to the miscibility between the components (acrylic copolymer and tackifier resin). In the case of the miscible blend system, the master curve of W shifted toward the lower rate side and, at the same time, the magnitude decreased as the tackifier resin content increased. The degree of the shift of W was extremely smaller than that of σmax. In the case of the immiscible blend system, the master curve of W remarkably decreased as the tackifier resin content increased, which suggests the fact that W of the PSA depended on the dynamic mechanical properties of the matrix phase and that the resin-rich phase acted as a kind of filler, thus reducing the practical performance.

Rheological study on the adhesion properties of the blends of ethylene vinyl acetate/terpene phenol adhesives

Measurements of the shear, tensile, peel, and creep strength of ethylene vinyl acetate (EVA)/CaCO3/terpene phenol adhesive system at three different ratios [100/60/0 (EVA-O), 80/48/20 (EVA-20), and 60/36/40 (EVA-40) by weight, using wood and aluminum as adherends] were conducted. Over a wide range of temperatures and rates of deformation, adhesion shear, tensile, and peel strength results, as well as the creep response over a broad range of temperature and stresses, were found to yield a single master curve by means of the reduced-variable technique. It was observed that the peak of E′ representing Tg, shifted toward higher temperatures as the amount of terpene phenol in the blend was increased. The most obvious effect of increasing the tackifier resin was the shifting of the adhesion strength master curves to the direction of lower rates. The shift was associated with the rise in Tg as the blend ratio was increased. The influence of the tackifier resin in modifying the viscoelastic properties of the adhesive was further described in a comparison of the adhesion strength master curves with corresponding dynamic viscoelastic curves of the adhesive films. The master curves for the creep response of the adhesives showed that the stress-breaking time relationship shifts toward longer time for EVA-40 with high Tg. Thus, it was found that the strength of adhesion is due mainly to dynamic effects in the adhesive of a viscous nature in the same way to the cohesive strength of the viscoelastic materials.

Miscibility between natural rubber and tackifiers. I. Phase diagrams of the blends of natural rubber with rosin and terpene resins

Natural rubber (NR) was blended in various ratios with 17 kinds of tackifiers, which were prepared from rosin and terpenes. The blends were heated to various temperatures (20–120°C) in order to investigate their miscibility. The blends were visually observed for transparency or opacity at each temperature and further observed under an optical microscope for any existence of phase-separated structure. Miscibility of the blends is illustrated as phase diagrams in this article. Phase diagrams of all blends investigated in this study were classified into four types: completely miscible, lower critical solution temperature, upper critical solution temperature, and completely immiscible. The miscible range of a blend system tends to become smaller as the molecular weight of a tackifier increases. The data also indicate that the esters of hydrogenated rosin and of disproportionated rosin show comparatively good miscibility with NR whereas polymerized rosin and its esters have poor compatibility with NR in most cases.

Synthesis and characterization of aromatic polymers derived from 5‐perfluoroalkylisophthalic acid

A series of polyisophthalamides and polyisophthalates having perfluorinated side chains were prepared from 5-perfluoroalkylisophthaloyl dichlorides. The aromatic polyamides and polyarylates synthesized by conventional low temperature solution polycondensation and interfacial polycondensation, respectively, had inherent viscosities of 0.19 to 1.28 dL g -1 in yields of 65 to 100%. Solubilies of the resulting polymers were improved by incorporating nonafluorobutyl groups but not improved by incorporating heptadecafluorooctyl groups. Although the effect on the glass transition temperature (T g ) of incorporating perfluoroalkyl groups into the aromatic polyamides or polyarylate backbone is great, the incorporation maintained the thermal stability of the polymers. In spite of the rigid nature of perfluoroalkyl groups, T g s were decreased by incorporating perfluoroalkyl groups. The value of the contact angle of water on the aromatic polyamides films gradually increased with incorporation of the perfluoroalkyl groups. On the other hand, the value of the contact angle remarkably increased when perfluoroalkyl groups were incorporated into polyarylates. The Owens γs were also calculated for some aromatic polyamides by measuring contact angles of diiodomethane on the polymer films. The γs were estimated at 23-37 mN m -1 and about 10% of them were contributed by hydrogen bonding.

Miscibility and PSA Performance of Acrylic Copolymer and Tackifier Resin Systems

The influence of miscibility of an acrylic PSA and several tackifier resin systems upon PSA performance was investigated. When the acrylic copolymer and the resins were blended in various proportions, three types of mixing state were found: miscible system, partially miscible system and immiscible system. In the case of miscible systems, PSA performance (tack, peel strength and shear resistance) depended upon the viscoelastic properties of the PSA. In the case of completely immiscible systems, the above PSA performance depended primarily upon the viscoelastic properties of a continuous matrix phase, and the separated resin phase acted as a kind of filler. In the case of partially miscible systems, the PSA performance changed discontinuously at the resin concentration where phase separation occurred. It suggests that the phase structure of a PSA greatly influences the PSAs performance.

Miscibility Between Ethylene Vinyl Acetate Copolymers and Tackifier Resins

Abstract A series of ethylene vinyl acetate copolymer (EVA) were blended with various kinds of tackifiers and the miscibility between the components was investigated. The miscibility of the blend is illustrated as a phase diagram. The EVA and modified rosin systems tended to have a phase diagram with lower critical solution temperature (LCST), whereas the EVA and petroleum resin systems tended to have that with upper critical solution temperature (UCST). The phase diagrams of EVA/tackifier resins systematically changed as VAc content in the copolymer increased, which is accounted for by the classical Flory-Huggins theory.

Bonding and Debonding Processes in Tack of Pressure-Sensitive Adhesives

Abstract Rolling friction coefficient of two acrylic pressure sensitive adhesives (PSAs) are measured as a function of velocity at several temperatures. It is found that the time (or velocity)-temperature superposition procedure is applicable for one PSA, while it is not for the other. The authors came to the conclusion that the rate of increase of the true contact area is different for the two adhesives. The time-temperature superposition is possible only in the case where the activation energy of the bonding process is equal to that of the debonding process.