The deformational rigidity increases due to relaxation of stresses in oriented PP fibres. Elongation of PP fibres is accompanied by mechanical failure in all stages, which is a distinctive feature of deformation processes in these materials. Ordering of the structure of amorphous regions, manifested by an increase in the deformational rigidity of these fibres, is the result of stress relaxation in oriented PP fibres.Isotactic polypropylene is widely used for manufacturing industrial fibres, and the high strength at relatively low density should be noted above all [1][2][3]. The manufacturing process for polypropylene (PP) fibres is a multistage process, and the fibre undergoes temperature and deformation treatment in different stages [4,5]. To improve product quality and optimize industrial orientation of PP fibre, it is necessary to understand the structural processes that take place in fixing the fibre in the stitched state, i.e., as a result of stress relaxation [6].The relaxation processes that take place in stitched (loaded) fibres and yarns in many cases significantly alter their performance properties. There is currently no complete representation of the structural processes that cause such changes in the deformation properties of fibres and yarns. The change in the deformation characteristics of fibres in the stretched state must undoubtedly be taken into account for reliable prediction of the deformation properties of synthetic fibres and the articles made from them, which is not always done in practice.We established the character of the change in the rigidity of stretched film PP fibres during stress relaxation and elucidated the structural nature of these changes. We investigated PP film fibre (manufactured by Tverkhimvolokno OJSC) with a linear density of 130 tex and draw ratio of λ = 6, tensile strength of σ t = 580 MPa, and elongation at break of ε b = 22%.The deformation-strength properties in the stress relaxation and active stretching regime and the structural rearrangements that take place in stitched fibers and yarns were investigated. The studies of the mechanical properties of the fibres in active stretching (obtaining the stress-strain diagrams) and stress relaxation regimes were conducted on an Instron-1122. The tests in conditions of stopping stretching and then stretching again were performed on the same setup. IR spectroscopy was used to reveal the moleculardecomposition processes that take place in stretched oriented samples. The valence bond breaks in the macromolecules were recorded with this method based on the newly formed stable terminal groups formed as a result of decomposition. The data were obtained by frustrated total internal reflection on a Spectrum One Fourier IR spectrometer. The absorption bands at 1742 and 1650 cm -1 were considered the molecular-decomposition bands in the IR spectrum of PP [7]. Low-frequency Raman spectroscopy, which is sensitive to the regular segments of macromolecules of any type regardless of their localization both in amorphous and in crystalline ...
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.