A hot‐melt pressure‐sensitive adhesive based on styrene‐butadiene‐styrene rubber. The effect of adhesive composition on the properties

Abstract

SYNOPSISHot-melt pressure-sensitive adhesives based on styrene-butadiene block copolymers with aliphatic and aromatic tackifying resins and plastifying oils have been analyzed. The importance of the resin structure in the compatibility with the block copolymer and the influence of the different paraffinic-naphthenic character of the oil in PSA performance have been shown. Ternary systems with a fixed polymer content (30%) and with variable resin and oil contents show a good miscibility over the whole range of compositions, and only one glass transition temperature was found in each composition. The relationship between chemical composition and bulk performance are expressed in terms of the viscoelastic behavior of the adhesives, measured by DMTA. It has been shown that at a given resin content there is a minimum on tan 6 peak vs. temperature, the melt viscosities present a plateau region and the tack strength shows a maximum. An important conclusion is that phase separation is not a requirement for maximum tack; some restricted miscibility is enough, present in a few microdomains of the blend. 0 1996 John Wiley & Sons, Inc. I NTRODU CTlO NHot-Melt pressure-sensitive adhesives are generally blends of block copolymers with modifying resins and other additives in order to improve the characteristics and performance.The viscoelastic properties of the bulk adhesive depend on the chemical composition of its components and are related to the final properties of these materials.'-" In a general sense, the bonding and debonding processes that take place, corresponding to the adhesion to a surface and to the resisce to separation, respectively, are viscoelastic processes. Bonding takes place a t low rates and a t low deformation. On the contrary, debonding is a high rate and high deformation process. Because of these general rheological characteristics, the properties of the adhesive are strongly dependent on their composition, qualitative and quantitatively considered and, therefore, on the compati-* To whom correspondence should be addressed Journal of Applied Polymer Science, Vol. 62, 1263-1275 (1996) 0 1996 John Wiley & Sons, Inc.CCC 0021-S995/96/OS1263-13 bility of the components in a system that it is multiphase. As a consequence of the varied composition in the blends of the main component, elastomer, with tackyfing resins and oils, the thermal transitions and the dynamic-mechanical relaxations may be very variable, conditioning the performance and final properties such as tack, peel strength, and shear strength. Thus, thermal transition measurements have been carried out by Differential Scanning Calorimetry (DSC) and the viscoelastic relaxations have been determined by Dynamic Mechanical Thermal Analysis (DMTA) , by observing the differences in mechanical properties as a function of Changes in the storage ( E ' ) and loss ( E " ) moduli or in the tan 6 = E " / E r have been used to characterize the behavior of both the pure components and the blends. Earlier studies on natural rubber-based adhesives and the influ...

Dynamic mechanical properties in blends of poly(styrene‐b‐isoprene‐b‐styrene) with aromatic hydrocarbon resin

“…SIS consists of two incompatible blocks in the solid state, the isoprene segments with lower T g and the styrene segments with upper T g , which form a microphase‐separated structure at room temperature 17–19. The material can be considered as an elastermeric matrix physically vulcanized by the aggregation of polystyrene (PS) end blocks, which also act as reinforcing filler 20–22.…”

Rheological and physical characterization of pressure sensitive adhesives from bio‐derived block copolymers

“…Although it has been found that two‐phase systems generally violate the time‐temperature superposition, the master curves of loss tangent delta are also shown in Figure for validation. The level of compatibility between the tackifiers and the biopolymer can also be evaluated from Figure as Galan et al . have shown in their work on HMPSAs based on SBS rubber.…”

“…Although it has been found that two-phase systems generally violate the time-temperature superposition, the master curves of loss tangent delta are also shown in Figure 7 for validation. The level of compatibility between the tackifiers and the biopolymer can also be evaluated from Figure 7 as Galan et al 28 have shown in their work on HMPSAs based on SBS rubber. Generally, more intense peaks correspond to higher levels of compatibility between the components, and from Figure 7 it can be concluded that at low and intermediate frequencies tackifiers 3 and 5 have better compatibility with the biopolymer rather than tackifier 4 as they display more intense peaks.…”

Blending the Effectiveness of Anionic Polymerization with the Versatility of RAFT by Use of the Atom Transfer Radical Addition–Fragmentation Technique

“…For this reason, techniques for the sequential application of both methods would enable the construction of a much broader palette of heterogeneous copolymers. Styrene/diene based block copolymers, which are used extensively in various industries such as paving and construction, adhesives, and paints and coatings, could be supplanted with styrene/butyl acrylate analogs. A natural strategy for the marriage of RAFT and anionic polymerization is the construction of CTA functionality from the terminus of a living polyanion.…”