Effects of surface modification by oxygen plasma on peel adhesion of pressure‐sensitive adhesive tapes

Surfaces of poly(isobutylene) (PIB) and poly(butylacrylate) (PBA) pressure‐sensitive adhesive tapes were treated by oxygen plasma, and effects of surface modification on their adhesive behavior were investigated from the viewpoint of peel adhesion. The peel adhesion between PIB and PBA pressure‐sensitive adhesive tapes and stainless steel has been improved by the oxygen plasma treatment. The surface‐modification layer was formed on PIB and PBA pressure‐sensitive adhesive surfaces by the oxygen plasma treatment. The oxygen plasma treatment led to the formation of functional groups such as various carbonyl groups. The treated layer was restricted to the topmost layer (50–300 nm) from the surface. The GPC curves of the oxygen plasma‐treated PBA adhesive were less changed. Although a degradation product of 1–3% was formed in the process of the oxygen plasma treatment of the PIB adhesive. There are differences in the oxygen plasma treatment between the PIB and PBA adhesives. A close relationship was recognized between the amount of carbonyl groups and peel adhesion. Therefore, the carbonyl groups formed on the PIB and PBA adhesive surfaces may be a main factor to improve the peel adhesion between the PIB and PBA adhesive and stainless steel. The peel adhesion could be controlled by changing the carbonyl concentration on the PIB and PBA adhesive surfaces. We speculate that the carbonyl groups on the PIB and PBA adhesive surface might provide an interaction with a stainless steel surface. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 78: 1392–1401, 2000     

Studies on tack of pressure-sensitive adhesive tapes: On the surface contamination by adhesive mass after peeling

The presence of adhesive residue on the surface of various adherends after peeling has been confirmed using a tracer technique. Adhesive bonding is found to break by a cohesive mechanism, although the unbonding process seems apparently to be due to intersurface failure. This result supports the concept for adhesive bond breaking proposed in the preceding paper: The unbonding proceeds from the viscoelastic deformation of the adhesive mass around the wetted spots on the surface. As the number of spots in a unit area is controlled by surface energy, the tack value is dependent on the critical surface tension of the adherends.     

Theory of tack of pressure sensitive adhesive. I

If the tack of a pressure-sensitive adhesive is closely related to the rolling motion of a ball on the material, it is more scientific to express tack in terms of the rolling friction coefficient, which depends on the physical properties of the materials, and not on any trivial conditions of measurements. It is shown that the rolling friction coefficient of a pressure-sensitive adhesive can experimentally be determined from the pulling cylinder method much more easily than the rolling ball method and that we can theoretically calculate the rolling friction coefficient by making some assumptions, concerning deformation and failure of a pressure-sensitive adhesive.     

Studies in the nature of adhesive tack

By measuring tack energy using a modified probe tack testing procedure, the interrelation of bulk energy and surface energy effects in pressure-sensitive adhesives was studied. Tack energy was strongly influenced by the solvent used in the preparation of the adhesive film. A procedure was empirically derived which reduced the number of variables to a single variable, yielding a single master curve in which the independent variable was the speed of probe withdrawal expressed on a logarithmic scale. The form of the curve was a simple exponential function, y = A exp (mx), where A and m are constants and y and x are the dependent and independent variables, respectively. The constant m was found to be a unique function of the type of adhesive used. A theoretical interpretation of the devised procedure was based on bulk viscoelastic effects and a combined activation energy–free volume concept of adhesive bonding. The wider implications of this are briefly discussed.     

Studies on tack of pressure-sensitive adhesive tapes: On the relationship between pressure-sensitive adhesion and surface energy of adherends

The relationship between wetting and pressure-sensitive adhesion was studied using an adhesive composed of poly(butyl acrylate) and various adherends of different surface tension. The amount of adhesive deposit was determined quantitatively by tracer technique although the unbonding process was apparently observed as interface failure. The adhesive force and amount of deposit were both dependent on the critical surface tension of the adherends. Maximum tack value and contamination were observed with adherends whose critical surface tension was close to that but a little higher than that of the adhesive. The adhesive force obtained was lower than cohesive strength of adhesive. From this evidence, a mechanism for pressure-sensitive adhesion was discussed: the bond breaks in the addesive mass around the very minute spots where interaction is at work between adhesive and adherend. Inasmuch as the density of the minute spots per unit area depends on the surface tension, the adhesive force also depends on the surface tension.     

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 T_g 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, T_g, and the pressure‐sensitive adhesive performance. T_g of the blend was higher than that expected from T_gs 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 T_g 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 T_g increases. However, both the curve of the peel strength and the holding power of such system did not shift along the rate axis. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 71: 651–663, 1999     

Melt versus solvent coating: Structure and properties of block–copolymer‐based pressure‐sensitive adhesives

Pressure‐sensitive adhesives (PSAs) composed of a styrene–isoprene–styrene triblock copolymer and a midblock‐associating resin were prepared via solvent and hot‐melt coating. The formulations and thermal histories up to the point of coating were identical, yet significant differences in the properties were observed as a function of the coating method. The solvent‐coated PSA showed superior shear holding power, and the hot‐melt‐coated PSA performed better in tack and peel tests. Two factors resulting from the processing conditions were responsible for these property differences. The quick cooling process occurring after hot‐melt coating led to a poorly defined microstructure and, therefore, less physical crosslinking. Rheological data for melt‐pressed and solvent‐cast PSA films confirmed these microstructural differences. The increased solubility of the tackifier in the solvent additionally created a composition gradient in the solvent coating. Annealing improved the long‐range order of both hot‐melt and solvent coatings, producing a body‐centered cubic microstructure identified by small‐angle X‐ray scattering. This microstructure improved the shear strength of both types of adhesive coatings, whereas the peel and tack properties of the solvent coatings remained inferior to those of the hot‐melt coatings because of differences in the surface compositions. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 86: 3355–3367, 2002     

保护膜用高初粘低剥离力丙烯酸酯压敏胶的研制

采用丙烯酸异辛酯、特殊丙烯酸酯单体A、丙烯酸、丙烯酸羟乙酯和甲基丙烯酸甲酯为单体,乙酸乙酯、甲苯为溶剂,偶氮二异丁腈为引发剂,制备了保护膜用高初粘、低剥离力溶剂型丙烯酸酯压敏胶。采用单因素试验法探讨了溶剂的类型与配比、引发剂用量、软硬单体配比、功能单体用量、特殊丙烯酸酯单体A的用量、固化剂种类和用量对压敏胶黏度、180°剥离强度及应用性能的影响。研究结果表明:对于保护膜用溶剂型丙烯酸酯压敏胶,通过引入外交联剂,能够显著增大其内聚力。外交联剂类型和用量对压敏胶的剥离强度、初粘性及排气性能均有很大的影响;氨基树脂固化剂在初粘性、排气性能、降低剥离强度方面表现更佳。     

热熔压敏胶,用于OPP包装带优先技术

从包装带的历史,成本,生产率,性能（使用温度、对回收纸板粘合性、对非极性基材粘合、涂胶量控制）,外观,环境污染问题等方面论证热熔压敏胶作为优先技术,应用于OPP包装带。     

Theory of tack of pressure-sensitive adhesive. II

When a cylinder is pulled on a pressure-sensitive adhesive, the bonding and debonding processes proceed simultaneously within the surface of contact. In the previous paper, the theory of rolling friction coefficient of pressure-sensitive adhesives was proposed for the case where bonding occurs instantaneously. The theory is modified in this paper so as to include both the time-dependent bonding process and debonding process at the same time. Effect of fiber-forming on rolling friction is also examined. It is ascertained that the modified theory reproduces quite well the experimentally observed features of the curves of rolling friction coefficient against velocity.     

The pressure–volume–temperature properties of three well-characterized low-density polyethylenes

Pressure–volume–temperature relationships of three low-density polyethylenes are reported in the temperature range of 30°–225°C and in the pressure range of 0–2000 kg/cm². The same materials had previously been studied by the IUPAC Working Party on Structure and Properties of Commercial Polymers with regard to basic characterization, melt rheology, processing, and end use properties. They were found to be remarkably equal in basic parameters and in some of the melt rheology, but differences among the three samples were found in other rheological properties and in the processing and end use properties of blown film. We find the PVT relationships of these three samples to be practically identical. A numerical equation of state based on the Tait equation is established. It reproduces the measured specific volume data of the melts to better than 0.002 cm³/g.     

Molecular parameters and their relation to the adhesive performance of emulsion acrylic pressure‐sensitive adhesives. II. Effect of crosslinking

Acrylic emulsion pressure‐sensitive adhesive (PSA) films generally have much lower shear holding power than that of their solvent‐borne counterparts for the same peel and tack. This is due to their discrete microgel morphology in the film. In contrast, film cast from solution‐polymerized acrylic PSA forms a continuous network as a result of crosslinking acrylic acid and aluminum acetyl acetonate (AAA) in the film following the solvent evaporation. Novel acrylic emulsion PSA was made by copolymerizing ≤1 wt % isobutoxy methyl acrylamide (IBMA) in the polymer backbone. The IBMA grafted the linear portion of the acrylic polymer with the microgels upon heating the film, which resulted in a significant increase in the shear holding power. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 79: 2558–2564, 2001     

Characterizing acrylic foam pressure sensitive adhesive tapes for structural glazing applications-Part II: Creep rupture results

The objective of this study was to determine relevant, primary mechanical characteristics of high-performance acrylic foam pressure sensitive adhesive (PSA) tapes, an alternate fastening method for structural glazing applications. Traditional fastening methods for structural glazing typically employ structural silicones and, consequently, relevant ASTM test standards and specifications appear to be more appropriate for silicones and similar products that exhibit limited time dependence. This study was aimed at characterizing and evaluating acrylic foam PSA tapes for structural glazing applications, and because of their time dependence, viscoelastic characterization was included. Since there may be significant differences in the viscoelastic responses of acrylic foam PSA tapes and silicones, the study may account for important differences between acrylics and silicones in structural glazing applications. The acrylic foam PSA used in the study was 3M™ VHB™ Tape G23F. For comparison, parallel ramp-to-fail tests were also conducted on 3 silicones: two one-part and one two-part compositions. Mechanical characteristics determined for the VHB™ Tape included the viscoelastic properties over a range of temperatures and test rates. Mechanical characteristics available in the literature were assumed for the silicones and confirm their limited time dependence. Ramp-to-fail strength data (Part I paper) and creep rupture (accompanying paper, Part II paper) data was collected for the VHB™ Tape and the silicones. Using the time–temperature superposition principle, master curves of VHB™ Tape storage and loss moduli in shear and tension were developed with data from a dynamic mechanical analyzer (DMA). The thermal shift factors obtained from these constitutive tests were successfully applied to the VHB™ Tape creep rupture and ramp-to-fail data collected at 23, 40, and 60 °C, resulting in master curves of ramp-to-fail strength (in Part I of paper) and creep rupture durability (Part II paper) in shear and tension.     

Effect of model fillers on the adhesive strength of pressure-sensitive tapes

—The effect of various model fillers, namely glass beads, 'Spheriglass', and PTFE powder, on the adhesive strength of natural rubber (NR) and poly(n-butyl acrylate) (PBA) tapes has been investigated. Glass fillers treated with alkyl chlorosilane were also used. The adhesive strength was measured over a range of rates and temperatures, and corrections for the thickness of the adhesive and volume fraction of the polymer were introduced into the rate term. It was observed that the adhesive strength of PBA tapes filled with 20% PTFE is comparable to that of the control sample without filler. The strength measured over a range of strain rates increased for both untreated and treated Spheriglass-filled adhesives. Filled NR adhesives showed an enhanced strength only at very high strain rates. With 40% PTFE, this increase was quite apparent. The mechanism of improvement of the strength of adhesion due to the incorporation of a filler is explained. The addition of a filler introduces an additional mechanism of energy dissipation during deformation of the adhesive and a higher energy will be expended due to debonding of the filler and hysteresis.     

UV crosslinkable microsphere pressure sensitive adhesives—influence on adhesive properties

In the following study, a synthesis and characterization of UV crosslinkable acrylic pressure sensitive adhesives are presented. Different amounts of unsaturated photoinitiator 4-acryloyloxy benzophenone (4-ABF) were added in t-butyl acrylate/2-ethylhexyl acrylate monomer mixture and then polymerized using a suspension polymerization technique. The adhesive suspension was coated on a pilot coating machine, dried by application of IR and subsequently crosslinked under UV light. The copolymerized 4-ABF photoinitiator will produce reactive radicals upon absorption of UV light, which are capable of initiating a rapid chain reaction with neighboring C-H positions of polymer side chains, what leads to formation of crosslinked polymer structures. UV crosslinking process was monitored by ATR-FTIR spectroscopic technique. Adhesion properties of the synthesized materials were determined using standard measurements of tack, peel and shear strength. Results have shown that all adhesive properties are strongly influenced by the degree of crosslinking of the microspheres, which increased with higher amounts of added 4-ABF photoinitiator. All the three measured adhesive properties showed a substantial decrease even at small amounts of added 4-ABF. The decrease in adhesion may be correlated with higher crosslinking density, what also resulted in higher gel phase amounts. Determination of glass transition temperature showed minor difference between adhesive coatings.