Study of Elastomer Structure Microdefects by Positron Annihilation

Abstract

P. ARIFOV et al.: Study of Elastomer Structure Microdefects 565 phys. stat. sol. (a) 102, 565 (1987) Subject classification: 61.40 and 78.70; S12A complex lifetime and angular correlation study of positron annihilation in a wide range of polymers and elastomers is carried out. Pick-off annihilation from the localized states is found to be the main mechanism of positron annihilation in the studied elastomers. Influence of elementary free volumes of polymer structure as well as of chemical composition (presence of polar groups) of polymer chain elements on the concentration . Of positron traps is considered. Effective sizes of positron traps are found ranging from 6 up to 15A. It is demonstrated that the nature of positronsensitive centres is determined by the distortions in polymer chains packing close to the rigid, side groups and in places of deviations of shape of polymer chains from the linear one. Ha IUHPOKOM Kpyre 3JIaCTOMepOB H aMOP@HbIX IIOJIHMepOB IIpOBeAeHbI KOMIIJleKCHbIe Ha6JIIop2HIIH CIIeKTpOB BpeMeHH X H 3 H H IIOBMTPOHOB 12 YrJIOBOfi KOppeJIR~HH BHHHIWJIH-UHOHHOI'O H3JIYYeHHX. nOJIyYeHbI3KCIIepHMeHTaJIbHbIe HOKa3aTenbCTBa TOrO, YTO OCHOB-HbIM MeXaHH3MOM r~6 e n t l II03HTPOHHR B HCCJlejJOBaHHbIX 3JIaCTOMepaX IIBJIReTCR , ,IIHIE-O##"-aHHII~HJIXIHH k13 JIOKaJIH30BaHHOrO COCTOXHIIR. PaCCMOTpeHO BJIHRHEle MHKPO-ae@eKTOB CTPYKTYPbI, COCTaBJIHIo~HX CBO6OnHbIfi o 6 % e~ B 3JIaCTOMepaX Ha HX aHHH-rHJlRUHOHHbIe XapaKTepIICTHKH. k3CCJIeAOBaHO BJlHXHHe 3JIeMeHTHOrO COCTaBa IIOBTOPH-IoIUerOCR 3BeHa MaKpOMOJleKyJIbI H COAepXaHHH IIOJIRpHbIX rpyIIII Ha KOHUeHTpaqHIo IIO3HTpOHHfi~IyBCTBHTeJIbHbIX MHKpOIlOJIOcTefi B 3JIaCTOMepaX. OIIpeHeJIeHbI pa3MepbI MHKpOHe@eKTOB CTPYIETYPLI 3JIaCTOMepOB pa3JIH~HOrO MOJIeKyJlRpHOrO CTPOeHHH, KOTOpbIe COCTaBJIHIOT (6 A0 20) A. nOKa3aH0, YTO IIpHpOna BTHX IIO3HTpOHHHfiYyBCTBH-TeJIbHbIX Ae@eKTOB 06yCJIOBJleHa HapyIIleHHRMH YIIaKOBKH MaKpOMOJI eKyJIHpHbIX UeIlefi B6JIH3H WeCTKHX 6OKOBbIX IIpHBeCKOB, H3JIOMOB H n e p e r~6 0~ 4enH.

Positron Annihilation in Chloropolystyrenes

“…The existence of such state has been proposed many times in case of samples containing Cl and studied with the use of PAS, e.g. in aqueous solutions of Cl' ions [26], in chlorine substituted hydracarbons in non-polar liquids [27], in polyvinyl chloride on thermal degradation [28], in fluorinated elastomers with Cl in side groups [29] and for alkali chlorides [30]. In Ref.…”

Investigation of structural transformation in ripening cotton fiber by the methods of positron annihilation

“…The characteristics of annihilation spectra for the first cellulose sample appreciably differ from all the rest (Figures 3 -5, Table 2). The increasing contribution of positronium annihilation in the loosened areas (I 3 , I 4 values), the narrowing angular distribution, and the good quantitative agreement between I N and I 4 (3I N =I 4 ), as is frequently observed in amorphous polymeric materials (Arifov et al 1987), allows us to make a conclusion on the Ônon-structural', practically non-fibrillar, organization of macromolecules at the first separated stage of synthesis. During this period of time, an intensive growth in length and the formation of the external cuticle shell and primary fibril wall occur.…”

“…Positronium atoms are localized in the amorphous areas of paracrystals (A type defects) or in the amorphous intrafibrillar volume (B type defects). The high crystalline core (2) and paracrystals have a positive affinity to positrons (Arifov et al 1987). In result, we have a short time component of the positron life-time spectra connected with positron annihilation at structural defects in the paracrystalline areas and crystalline core (2) and a long-lived component connected with positron annihilation at the two type of microcavities (A-and B-type).…”

“…Resources of traditional methods for the investigation of amorphous areas are insufficient due to the absence of long-range ordering in the macromolecular configuration and arrangement. Therefore, applying the method of positronium atom annihilation to study the cotton fiber microstructure, and taking into account the principal possibility of microcavity observation at the molecular level (Varisov et al 1981;Arifov et al 1987;Tishin et al 1988Tishin et al , 1990Askadsky et al 1992), we get the required addition to the study of such a complicated amorphous -crystalline system as the cotton fiber. Small-angle neutron-scattering studies have been carried out on cellulose fibers from ramie and Populus maximowicii (cotton wood).…”