Bandzierz, K.

Bielinski, D.

Blume, Anke

Dierkes, Wilma K.

Dryzek, E.

Dryzek, J.

Kleczewska, J.

Reuvekamp, Louis A.E.M.

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Application of PALS to Study Structure of Elastomers

University of Twente Research Information

tiiiiiiiiiIIiIIIIItII4IPL0. Katarzyna Bandzierz: Applicątion of PALS to Study Structure of ElastomersK. Bandzierzt'*, J. Kleczewskal, L. Reuvekamp2, J. Dryzek', E. Dryzek3, W. Dierkes2,D. M. Bieli skil and A. Blume21lnstitute of Polymer and Dye kchnology, Ł dź University of Technology, Stefanowskiego 12/16,90-924 Ł dź, Poland'Elastomer kchnology & Engineering, University of TWente, Drienerlolaan 5, 7500 AE Enschede,The Netherlands3Institute of Nuclear Physics, Polish Academy of Science, Radzikowskiego 752,31-342 Krak w, Polandemail : katarzyna. bandzi erz@ gmail. comCrosslink density, defined as a number of network chains per cubic centimeter of a sample,describes a three-dimensional structure of elastomers. Due to the fact that the crosslink densityinfluences to a high extent numerous properties of elastomers, its comprehension anddeterminability is fundamental. Hereunder, the structure and packing of macromolecular chains, andthe number and length of crosslinks between them, influence the size of free volumes. However, thestructure of elastomers can be highly complicated, due to complexity of reactions which occurduring high-temperature curing process. Precise characterization of structure of crosslinkedelastomer systems still remains challenging. A powerful technique, which can serve to investigatethe microstructure of polymeric materials is Positron Annihilation Lifetime Spectroscopy (PALS).The subject of the study were sets of samples on the matrix of styrene-butadiene rubber (SBR),crosslinked with use of three types of curing systems - dicumyl peroxide (DCP), zincdialkyldithiophosphate in combination with rhombic sulphur (ZDT/S8), and N-cyclohexyl-1-benzothiazole sulfenamide with rhombic sulphur (CBS/SB), differing significantly in the length andstructure of crosslinks, but similar according to crosslink density. The room temperature PALSstudies were employed to provide information on the free volumes, which were correlated withcrosslink density, determined with use of equilibrium swelling in toluene and calculated on the basisof Flory*Rehner equation. The lifetime of o-Ps as a function of crosslink density exhibits in generala downward trend. For DCP cured samples, the shortening of o-Ps lifetime is very little, whereas forCBS/Ss and ZDTlSs, the rE value considerably drops with increase in crosslink density. However,the r: values are scattered and cannot be directly assigned to the formation of crosslinks and moredense packing. The intensity of the rs cofirponent, i.e., 13 decreases with increasing crosslink density,indicating on reduction of free volumes fraction. The change of Is value is very little for peroxidecured samples, in contrary to CBS/Ss and ZDTlSa. It demonstrates that the obtained data arestrongly dependent on the type of curing system used - particular types of molecules, such asrhombic sulphur and/or accelerators, present in the elastomer matrix. They can significantlyinfluence, by inhibition or quenching, formation of o-Ps.These studies reveal that the obtained values from PALS for crosslinked elastomers, due tovarious possible types and amounts of curatives incorporated into the polymer matrix, cannot bealways directly correlated with crosslink density, what is often overlooked in scientific publications.

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https://ris.utwente.nl/ws/files/5536088/_2016.49_PSPA15_Bandzierz.pdf

Application of PALS to Study Structure of Elastomers

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University of Twente Research Information