Tatjana Ivanova

Epoxy composites filled with high surface area-carbon fillers: Optimization of electromagnetic shielding, electrical, mechanical, and thermal properties

A comprehensive analysis of electrical, electromagnetic (EM), mechanical, and thermal properties of epoxy resin composites filled with 0.25–2.0 wt. % of carbon additives characterized by high surface area, both nano-sized, like carbon nanotubes (CNTs) and carbon black (CBH), and micro-sized exfoliated graphite (EG), was performed. We found that the physical properties of both CNTs- and CBH-based epoxy resin composites increased all together with filler content and even more clearly for CBH than for CNTs. In the case of EG-based composites, good correlation between properties and filler amount was observed for concentrations below 1.5 wt. %. We conclude that CBH and, to a lower extent, EG could replace expensive CNTs for producing effective EM materials in microwave and low-frequency ranges, which are, in addition, mechanically and thermally stable.

Creep of Poly(Vinyl Chloride)/ Chlorinated Polyethylene Blends

The results of experimental investigations of the creep behavior of blends of poly(vinyl chloride) (PVC) with chlorinated polyethylene (CPE) are presented. Eight types of specimens with the PVC/CPE weight ratios of 100/0, 90/10, 80/20, 60/40, 40/60, 20/80, 10/90, and 0/100 are examined. The creep tests were continued for 1000 h. It is discussed how the blend composition affects the elastic and inelastic behavior of the material. The elastic compliance of the blend can be determined from the properties of its components by using the Kerner and Budiansky equations for heterogeneous systems with a phase structure of statistic-dispersion type. The creep compliance (the total current compliance minus the elastic compliance) obeys the power law of creep with coefficients depending on the blend composition.

Thermal and elastic properties of poly(vinyl chloride) (PVC) + chlorinated polyethylene (CPE) blends

Abstract. Eight types of PVC + CPE blends with different weight ratios (PVC/CPE = 100/0, 90/10, 80/20, 60/40, 40/60, 20/80, 10/90, and 0/100) are tested. Data on the heat conductivity, thermal diffusivity, and heat capacity of the blends investigated are reported. Primary attention is paid to the structural approach for effective elastic constants: bulk, shear, and Youngs modulae. The blends are considered as random mixtures of two isotropic constituents. It is found that the elastic moduli may be well represented by the Kerner and Budiansky equations.

Prediction of the Stress-Relaxation Behavior of Thermoshrinkable Radiation-Modified Polymer Materials

The results of investigating nonirradiated and gamma-irradiated (to an absorbed dose of 150 kGy) specimens of an ethylene-octene copolymer are presented. The thermal properties (melting endotherm and crystallization exotherm) are determined by the method of differential scanning calorimetry. The behavior of the material in short-term tension is discussed. The primary attention is given to the temperature-time dependence of the mechanical properties of the materials under creep and stress relaxation. The long-term stress relaxation is predicted from short-term creep tests at elevated temperatures using the temperature-time correspondence principle. The results obtained indicate that the material investigated may be used for thermoshrinkable polymer products with long-term serviceability.

Recycled Polycarbonate Based Nanocomposites

Post-consumer polycarbonate (RPC) blends with various amounts (5, 10, 30 wt. %) of ethylene vinyl acetate copolymer (EVAc) are investigated as potential nanocomposite matrices. At EVAc weight content of 10 wt.% maximum tensile strength σM and impact strength AI increase is observed in comparison to neat RPC. Addition of EVAc, however, reduces resistance to creep as well as decrease thermal stability of the investigated compositions. Addition of montmorillonite nanoclay (MMT), however, allows increase modulus of elasticity E and yield strength σY of the investigated RPC blend with 10 wt. % of EVAc. Besides it creep resistance and thermal resistance of the investigated system is increased to certain extent.

PC/ ABS Nanocomposites with Layered Silicates : Obtaining, Structure and Properties

Due it increasing use in electronics, polymers, mainly acrylonitrile-butadiene-styrene (ABS) and its blend with polycarbonate (PC), are making considerable part of electronic waste. It has been proven that halogenated flame retardants used in polymers for electronics are toxic to environment and human health. Aim of the research is to evaluate the effects of nanostructured montmorillonite clay (D43B) addition on the mechanical and thermal characteristics of PC, ABS and its binary blends. The effect of substitution of virgin polymers in the blend with recycled ones has been also investigated. It has been determined that as far as the recycled polymer content in the composites does not exceed 10wt.%, tensile and thermal properties of the systems are not considerably affected. Addition of D43B up to 1,0-1,5wt.% contributes to the increment of mechanical stiffness, strength and thermal stability of the composites.

Impact of non-functionalized and ionic liquid modified carbon nanotubes on mechanical and thermal properties of ethylene- octene copolymer nanocomposites

In this article the development and characterization of composites made from metallocene based ethylene-octene copolymer (EOC) with 38% octene content, non-modified or modified multi walled carbon nanotubes (MWCNTs), covalently functionalised with long chain hexadecyl moiety imidazolium ionic liquid (IL-f-MWCNTs), is presented. The procedure of MWCNTs functionalization is discussed. In order to obtain a good dispersion of the filler, composites with MWCNTs and IL-f-MWCNTs in the concentration range of 0.5-12 wt.% were made by ultrasonication / thermoplastic mixing method. The results indicated improvement in mechanical properties with increase of the filler content. The methodology of the development of EOC matrix nanocomposites with IL-f-MWCNTs showed advantages of the conductive material creation with high mechanical stiffness compared to direct melt mixing of EOC with non-modified MWCNTs. A notable enhancement of thermal stability was observed in case of both pristine MWCNTs and IL-f-MWCNTs containing EOC nanocomposites, which was attributed to scavenging action of the nanofiller. Modification of EOC with IL-f-MWCNTs showed somewhat increased efficiency in enhancing overall thermal stability of the composites because of better dispersion of the nanofiller due to compatibilizing effect of IL modifier.

Multi-Component Composites Based on Polypropylene, Ethylene-Octene Copolymer and Zinc Oxide

Multi-component blends of polypropylene (PP), ethylene-1-octene copolymer (EOC) and zinc oxide (ZnO) are prepared by melt mixing using two-roll mill. Samples prepared by compression moulding have been investigated by using differential scanning calorimeter (DSC). It is found that addition of ZnO particles decreases PP melting point and increases crystallinity degree of PP. ZnO works as nucleation agent for PP by increasing quantity of crystallization centers, but at the same time decreasing structure quality. Because of the structure change mechanical properties are affected. At lower nanoparticle concentration some reinforcement effect I observed, while at higher particles concentration brittlening occurs. Crystalline structure and particles nature increases thermal stability of PP and PP/EOC blends.

Manufacturing, structure and properties of recycled polyethylene terephthalate /liquid crystal polymer/montmorillonite clay nanocomposites

Polyethylene terephthalate (PET)/liquid crystal polymer (LCP)/monthmorillonite clay (MMT) compositions were obtained by melt mixing. Their mechanical, structural, rheological and thermal properties were investigated.

Thermal stability of polyacetal/ethylene-octene copolymer/zinc oxide nanocomposites

In this work we investigate binary blends of polyoxymethylene and ethylene octene copolymer (EOC) and their composites with nanostructured zinc oxide (ZnO). EOC content in the composites varies from 0 to 50 wt. %. The amount of ZnO filler in the composites is changed in the interval from 0 to 5 wt. %. Thermal properties of composites are investigated with thermogravimetric analysis and differential scanning calorimetry. It is observed that ZnO addition increases thermal stability of the investigated composites.