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.

No abstract

The microstructure of cotton fiber (sort 175-F, 4 type) at various ripeness stages has been investigated by measuring the spectra of positron life-time and the angular correlation of annihilation radiation. It has been established that the macro strength (breaking load) depends on the concentration and sizes of microdefects (radius less than 10 Å ) in amorphous interfibrillar areas. These defects can be studied by registering the characteristics of positron and positronium atom decay and which are hard to reach by traditional physical methods for the analysis of the cotton fiber structure.

No abstract

The relaxation of polyimid films after the axial tension has been investigated by measuring life-time of positrons and angular correlation of annihilation photons. The nonmonotonic change of mean life-time while relaxing the free film has been found. Two range of changes of positron-sensitive properties can be seen: "rapid" relaxation for 4-5 hours (characterized by reducing life-time of short-lived component) and "slow" relaxation (characterized by reducing the intensity of longlived component).The results of this investigation have been compared with those of measuring of sample density and dielectric losses. The possible explanations and the changes of mechanizms of relaxation with the conditions of deformation and "the rest" of polymers are analyzed.