Study Of Polymer Composites Research Articles

Segregated Structure Copolymer of Vinylidene Fluoride and Tetrafluoroethylene Composites Filled with rGO, SWCNTs and Their Mixtures.

This work is devoted to the formation and study of polymer composites with a segregated structure filled with single-walled carbon nanotubes (SWCNTs), reduced graphene oxide (rGO), and their mixtures. For the first time, polymer composites with a segregated structure filled with rGO/SWCNTs mixtures were obtained. A copolymer of vinylidene fluoride and tetrafluoroethylene (P(VDF-TFE)) was used as a polymer matrix. At a fixed value of the total mass fraction of carbon nanofillers (0.5, 1, and 1.5 wt%), the rGO/SWCNTs ratio was varied. The composites were examined using scanning electron microscopy, wide-range dielectric spectroscopy, and tested for the compression. The effect of the rGO/SWCNTs ratio on the electrical conductivity and mechanical properties of the composites was evaluated. It was shown that, with a decrease in the rGO/SWCNTs ratio, the electrical conductivity increased and reached the maximum at the 1 wt% filling, regardless of the samples’ composition. The maximum value of electrical conductivity from the entire data set was 12.2 S/m. The maximum of elastic modulus was 378.7 ± 3.5 MPa for the sample with 1 wt% SWCNTs, which is 14% higher than the P(VDF-TFE) elastic modulus. The composite filled with a mixture of 0.5 wt% rGO and 0.5 wt% SWCNTs reflected 70% of the electromagnetic wave energy from the front boundary, which is 14% and 50% more than for composites with 1 wt% SWCNTs and with 1 wt% rGO, respectively. The lowest transmission coefficient of ultra-high frequencies waves was obtained for a composite sample with a mixture of 0.5 wt% rGO and 0.5 wt% SWCNTs and amounted to less than 1% for a 2 mm thickness sample.

Potentialities of a Laser-Induced Breakdown Spectroscopy Technique in the Study of Polymer Composites.

A laser-induced breakdown spectroscopy (LIBS) technique was used to evaluate the filler content in particulate epoxy-copper composites. A potential application for a direct and fast measurement of the filler in composites through the LIBS results is suggested using calibrated samples. The methodology used in this work makes possible the incorporation of LIBS as a quantitative technique for the study of particle metal-filled epoxy composites, providing a method to obtain a direct estimation of the filler volume fraction.

Practical application of thermal analysis in the development and study of polymer composites

Modern multifunctional thermoanalytical complexes equipped with computers are inherently mobile laboratories. They are able to solve a wide variety of problems in materials science and technology, both in applied research and in the quality control of products supplied to manufacturing enterprises. Using the example of experimental data obtained in the study of the curing processes of thermosetting semi-finished products (prepregs) of polymer composite materials (PCM), the methodological possibilities of modern devices for thermal analysis are shown. They allow investigating and predicting changes in the technological properties of prepregs in a wide temperature range.

Tribological study of polymer composites which are applied at the restoration of guides of machine tools

Розроблена методика, оснащення та проведені дослідження пари тертя полімер-чавун впорівнянні з парою тертя чавун-чавун. Виконано експериментальне порівняння застосу-вання формул Ейлера і Амонтона-Кулона для розрахунку коефіцієнта тертя для паритертя «вал-втулка» і «вал-стрічка». Виявлено вплив геомодифікаторів на коефіцієнт тертя ковзання та інтенсивність приробітку. Спроектовано лабораторну установку і прове-дено оцінка плавності ходу за коефіцієнтом тертя спокою

Multivariate Analysis of Damage Events in a Polymer Composite

Our prior studies of polymer composites subjected to stress have shown that a statistical distribution of acoustic emission damage events occur in multiscale and include several damage modes. Various multiscale modeling and simulation methods have been developed by others to obtain constitutive equations, which were used to link the variables between microscopic and macroscopic scales of continuum. Very limited experimental work exists to reveal physical evidence on the multiscale damage modes, and their relationship and consequential influence on performance of materials. This paper reports an innovative approach that experimentally evidences the response of damage events in different scales to the applied stress. It shows that a strong correlation exists between multiscale damage modes, and that ensemble-normalized entropy and physical evidence can be qualitatively and quantitatively used to integrate related damage modes at different scales.

Study of polymer composites by methods of thermoactivated spectroscopy

Variations in the temperatures of structural transitions and stabilization of charges depending on the degree of filling of low density polyethylene (LDPE) are studied by the methods of radiothermoluminescense (RTL) and thermally stimulated current (TSC). The RTL spectrum of the initial LDPE exhibits three maxima at temperatures of 130, 173, and 227 K (γ-, α-, and β-relaxation). The low-temperature maxima are assumed to be related to recombination of trapped electrons with products of radiolysis (radicals) and the relatively high-temperature peak at 228, to recombination of trapped electrons with luminescence centers after tunneling through a potential barrier. Modification of LDPE by introduction of a special additive (SA) in an amount up to 2 wt % shifts the γ- and α-peaks on the RTL curve to lower temperatures and the β-peak, to higher temperatures. The TSC spectrum exhibits two maxima at temperatures of 303 and 418 K, respectively. Modification of LDPE leads to a sharp decrease in the amplitude of both peaks and shifts the maxima to higher temperatures. The peak at 418 K is due to the release of trapped charges from traps in the crystalline phase of LDPE at melting.

Study of Polymer Composites Containing Low-boiling Liquids and Gases by Differential Thermal Analysis

Study of Polymer Composites Containing Low-boiling Liquids and Gases by Differential Thermal Analysis

Non-linear Viscoelastic and Physical Ageing Characterisation of Thermoset PR-500 Epoxy Resin

It is now well known that because of their polymeric matrices (and sometimes their use of viscoelastic fibres) structural polymer composites can exhibit creep or stress relaxation behaviour, leading to delayed failure long after the initial design and fabrication process. In addition, these time-dependent viscoelastic properties are significantly influenced by the sub-T physical ageing of these materials. Therefore any durability study of polymer composites for elevated use-temperature applications should address both the nonlinear viscoelastic response and the physical ageing effect of the constituents. The material nonlinearity in the resin has a ‘softening’ effect whereas physical ageing causes polymers to become stiffer and more brittle with age, increasing the likelihood of the more rapid progression of various damage states. Therefore, coupled material nonlinear and physical ageing conditions should be analysed to predict which effect would dominate under the applied loads and duration of loading. The primary objective of this paper is to present an experimental investigation of the nonlinear viscoelastic response of the PR500 resin at various stress levels. Also, the physical ageing characterisation results for a set of temperature and stress conditions are summarised. The properties summarised were successfully used in a multi-scale micro-mechanical methodology1, to study the AS4/PR500 five-harness satin woven-fibre composite laminate. PR500 is the polymer matrix that was modelled using the data presented here.