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  • Author: Rimvydas Milašius x
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Abstract

Nanofibers were electrospun from bicomponent poly(vinyl alcohol) (PVA) and modified cationic starch (CS) mixed solution PVA/CS with different mass ratios (75/25, 50/50 and 35/65) at a total concentration of 12 wt% for all polymer compositions. For comparison, pure PVA solution was used. Electrospinning technique Nanospider (Elmarco, Czech Republic) with a rotating electrode with tines was used to obtain nanofibrous web. The influence of prepared polymer solution compositions on the structure and morphology of nanofibers and webs were investigated. Analyzing the structure and morphology of the formed nanofiber webs, it was noticed that the fineness nanofibers were formed from the PVA/CS solution with a mass ratio of 50/50. This ratio of solution also lets us to obtain the nanofibrous web with less sticked nanofibers on spunbond. The increase in the CS ratio by more than 50/50 had a negative influence on the diameter of nanofibers and the structure of nanofibrous web.

Abstract

The article presents an overview of electrospinning process development from the first investigations in the field of behaviour of liquids in an electrostatic field to the electrospinning methods and investigations in the 21st century. The article presents the history of electrospinning process development, the main problems that are solved, and also indicates the gaps in the field of standardisation of nanofibrous web structure measurement and estimation. There are a lot of works in which authors analyse influences of various parameters on the electrospinning process or on the structure of electrospun web, whereas the majority of them do not analyse the quality of structure using mathematical criteria. Such a situation leads to different conclusions and makes it impossible to compare various works by different authors. Despite numerous studies in electrospinning, investigations in the electrospun nanofibrous web estimation are not sufficient. Until now, a unique standard method for measuring and estimating the fibre diameter and web porosity has not been developed. The necessity of such a method and standards is obvious, and the lack of such a standard could have a negative influence on the electrospun product introduction into the market.

Abstract

Functional textiles are one of the most important fields in textile industry and textile materials science. They include breathable, heat and cold-resistant materials, ultra-strong fabrics (e.g. as reinforcement for composites), new flameretardant fabrics (e.g. intumescent materials), optimisation of textile fabrics for acoustic properties, etc. Functional textiles became more and more important materials for various applications and interest in them grew year by year; and more and more conferences are focused on functional textiles, as well as the events which are not only textile conferences but encompass various fields of Material Science. This paper presents a short overview about the European Materials Research Society 2014 Fall meeting conference Symposium M “Functional textiles - from research and development to innovations and industrial uptake” and the projects which participated as symposium co-organisers: the European Coordination Action 2BFUNTEX funded by the EC 7th Framework Programme NMP, the COST Action MP1105 on “Sustainable flame retardancy for textiles and related materials based on nanoparticles substituting conventional chemicals (FLARETEX)” and the COST Action MP1206 on “Electrospun Nano-fibres for bio inspired composite materials and innovative industrial applications”.

Abstract

The main goal of this researcher is estimating of the possibility of long-lasting (even until 200,000 s) stress relaxation by empirical investigation, which was performed for a few thousands of seconds. The empirical investigations of longlasting stress relaxation of different types of yarns (multifilament polyester, cotton and woollen) at different levels of elongation, i.e. at 3%, 5%, 7% and 10%, were carried out. The method of long-lasting relaxation behaviour prediction by the break-point of relaxation rate as well as the linear dependence of second part of relaxation were used. It was found that the behaviour of relaxation can be described using time logarithmic scale by two straight lines, and the value of stress relaxation in long time period could be estimated by the second line. The break-point of relaxation rate of all kinds of yarns occurs in the area of 100-200 s after relaxations started. The obtained results showed that the place of relaxation break-point depends on the level of elongation but does not depend on the type of yarns.

Abstract

Electrospinning is remarkably a simple and versatile method for producing nanofibres. The diameter of nanofibres can vary from 10 nm to >1000 nm. In electrospinning, most of the attention is focused on producing fibres with a uniform diameter. It is very important to understand how the diameter and its distribution vary with the materials used and the processing parameters. An analysis of literature sources has shown that the distribution curves of the diameters obtained are very complex and do not resemble normal distributions, while they do more closely correspond to those of compound distributions. The goal of this article is to analyse the distributions of the nanofibre diameters and to propose a new method for the evaluation process of nanofibres and the quality of a nanofibre web. The uniformity of structure and the quality of nanofibres web must be described by average values. The peaks of modal values and the percentage quantity of them must be used for evaluation of a web structure.