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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...

The interaction between rubber and carbon black in compounds for road tire treads has been analyzed by using mechanical and dynamical measurements in three cured compounds based on SBRs. The rubbers were prepared in solution by anionic polymerization, and coupled with tin compounds in which the carbon-tin bond at the end of the chain may correspond to styryl or butadienyl terminations. The interaction parameter, defined by the ratio of mechanical and dynamic terms, has been used for the first time for the evaluation of the compounds. The SBRs with tin-butadienyl bonds exhibit an improved interaction with the filler, with increasing tin content.

Following the development of new SBRs for tyre applications, several kinds of tin-polymer bonds (styryl-, butadienyl-, isoprenyl-and a-methylstyryltin) have been studied, in both branched and linear chains.Dynamic-mechanical properties of the carbon black vulcanizates have been analyzed to establish a relationship between structural parameters of polymers and compound properties. The filler-polymer interaction parameter, defined by a ratio of mechanical and dynamic terms, has been used for the evaluation of the compounds. The introduction of different types of tin-polymer bonds, in branched and linear chains of the SBRs, implies an improvement in the hysteresis properties of the vulcanizates as well as a modification of the interaction parameter. ZUSAMMENFASSUNG:Zur Entwicklung von neuen Styrol-Butadien-Kautschuken (SBRs) fur Reifenanwendungen sind mehrere Arten von Zinn-Polymer-Bindungen (Styryl-, Butadienyl-, Isoprenyl-and a-Methylstyryl-Zinn) sowohl in linearen als auch in verzweigten Ketten untersucht worden. Die dynamisch-mechanischen Eigenschaften von Vulkanisaten mit RUB wurden analysiert, um eine Beziehung zwischen den Strukturparametern der Polymeren und den Materialeigenschaften herzustellen. Der Polymer-Fullstoff-Wechselwirkungsparameter, der durch das Verhaltnis von mechanischen und dynamischen Termen definiert ist, wurde zur Charakterisierung der Verbindungen herangezogen. Der Einbau von verschiedenen Zinn-Polymer-Bindungen in lineare und in verzweigte SBR-Ketten bewirkte eine Verbesserung der Hystereseeigenschaften der Vulkanisate und eine Veranderung des Wechselwirkungsparameters.

Hot‐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 visco‐elastic behavior of the adhesives, measured by DMTA. It has been shown that at a given resin content there is a minimum on tan δ 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. © 1996 John Wiley & Sons, Inc.