Juris Bitenieks

Thermo-mechanical properties of polyurethane modified with graphite oxide and carbon nanotube particles

ABSTRACT The aim of the proposed paper is to synthesize graphite oxide (GO) and use it in combination with carbon nanotubes (CNT) for the preparation of polyurethane (PU) composites. We fabricated composites with CNT/GO content of 0.05, 0.1, 0.3 wt.% with the use of ultrasonic treatment and tested their thermo-mechanical properties. Thermo-mechanical analysis (TMA) and dynamic mechanical analysis (DMA) measurements for CNT/GO composites were compared with the unfilled PU. Thermo-mechanical characteristics of storage moduli and loss moduli for CNT/GO nanocomposite were improved in comparison to the unfilled PU. The introduction of CNT/GO to the PU matrix creates strong bonding with the matrix and leads to the decrease of the glass transition temperature, new solid-solid phase transitions of polymer in the glass state. Dilatometric curves testified the remarkable changes in the glass transition of the polymer after the introduction of CNT/GO hybrid filler. Thermal expansion coefficient was calculated from the curve slopes and expressed continuously increasing expansion rate for CNT/GO composite. The measured characteristics were directly dependent from the filler content in the composite and the operated temperature.

Electrical and Mechanical Properties of Melt-Processed Polyethylene Terephthalate/Multi-Wall Carbon Nanotube Nanocomposites for Thermoelectric Materials

Nanocomposites with multiwall carbon nanotubes (MWCNTs) mixed in a polyethylene terephthalate (PET) matrix were prepared by the melt processing method. Some mechanical, electrical, and thermal properties of the composites in relation to MWCNT concentration in them were investigated, and the results obtained are presented graphically.

The Properties of Mesh Reinforced Nonwoven Composites

To create the heat-bonded geotextile with desirable properties, the mix of fibres (hemp, recycled polyethylene terephthalate and polypropylene fibres) for nonwoven webs formation and additional polypropylene reinforcing mesh are used. The results of the study on the influence of the reinforcing mesh on the properties of nonwoven composites (NWCs) are presented. Mechanical properties, water penetration and air permeability of the thermoplastic mesh reinforced NWCs depend on the hemp fibre pre-treatment time, mass per unit area and thickness of the used web and location of the reinforcing mesh. Obtained results allow concluding that mechanical as well as water penetration characteristics of the produced heat-bonded geotextiles are higher, while air permeability is comparable to the properties of the commercial prototype.

The Nonwovens Properties Made from Hybrid Fibres

The varieties of using nonwovens (NW) increases. The results of study about the influence of hybrid fibres content and technological parameters of production on properties of NW made from webs of two contents of hemp, recycled polyethylene terephthalate and polypropylene fibres, produced in two temperature and pressure conditions are presented. It is concluded that NW surface parameters and mechanical properties can be purposefully influenced with webs composition and production technology of NW. Produced NW are applicable, where lightweight and water permeable materials are necessary.

Elastic properties of UV irradiated polyethylene-octene copolymer composites with functionalized multi-walled carbon nanotubes

ABSTRACT Polyethylene-octene copolymer (E38) is melt compounded with carboxylated carbon nanotubes (CNT-COOH) in the presence of maleic anhydride grafted polyethylene (PEgMA). The effects of CNT-COOH in the amount of 1–10 wt. % on the mechanical properties of E38 based composite are investigated. It is revealed that addition of CNT-COOH considerably increases the stiffness and mechanical strength of the E38 based composites. The effect of UV irradiation on the structure as well as on the mechanical properties of E38/PEgMA/CNT-COOH composites is also investigated. Results of the investigation testify that UV resistance of the E38 based composites increases by increasing the content of CNT-COOH.

Modified silyl-terminated polyether polymer blends with bisphenol A diglycidyl ether epoxy for adhesive applications

Modified silyl-terminated polyether polymer (MS Polymer) was blended with bisphenol A diglycidyl ether (DGEBPA) epoxy at MS Polymer/epoxy ratio from 30/70 to 70/30. MS Polymer/epoxy systems were examined for two-component adhesive formulation with additional fillers. Applicability of the MS Polymer/epoxy system at the ratio of the components 60/40 is demonstrated for the development of adhesive formulation. Rheological analysis of the components A and B shows suitable viscosity values for development of two- component adhesives formulation. Curing dynamics as well as tensile stress-strain properties and Shore A hardness of the chosen adhesive formulation are reasonable for the development of MS Polymer/epoxy type adhesive.

Rheological, mechanical and adhesion properties of two component adhesive based on modified silyl terminated polyether polymer and epoxy resin

4 types of two component adhesives based on modified silyl-terminated polyether polymer (MS Polymer) and epoxy resin are formulated. Rheological and mechanical properties as well as weathering resistance of the developed adhesives are investigated. It is shown that curing times vary in a wide range depending on the type of MS Polymer. It is also demonstrated that kinetics of cross-linked network formation of the investigated adhesives, depending on the type of MS Polymer, considerably affects mechanical characteristics of the system: Shore A hardness, tensile strength and tensile elongation. Although under the influence of UV weathering mechanical properties of the investigated systems are decreased, the remaining tensile elongation values are not less than 30%. In parallel it is revealed that adhesive formulations, developed in the framework of this research, are most suitable for bonding with stainless steel, partially suitable for bonding with aluminium and less suitable for bonding with polyvinyl chloride.

Properties of PP/MWCNT-COOH /PP composites made by melt mixing versus solution cast /melt mixing methods

An approach on improvement of the properties of polypropylene / carbon nanotube (PP/CNT) composites is reported. PP blend compositions with carboxylic acid functionalized multi-walled carbon nanotubes (MWCNT-COOH) at filler content 1.0 wt.% were researched. One part of the composites was manufactured by direct thermoplastic mixing PP with the filler, but the other one was made from solution casted masterbatch with the following thermoplastic mixing. An increase of mechanical properties (Youngs modulus, storage modulus and tensile strength), compared to an increase of glass transition temperature indicated a reinforcement effect of CNTs on PP matrix, determined from the tensile tests and differential mechanical analysis (DMA), while the elongation was reduced, compared to PP matrix. By differential scanning calorimetry (DSC) analysis, the effect of nanofiller on the reorganization of PP crystallites was observed. A noticeable enhanced effect on increase of the crystallization temperature was indicated for masterbatch manufactured composite. An increase of thermal stability was also observed, compared to pristine PP and the composite made by direct thermoplastic mixing PP with the filler.

Carbon nanotubes and carbon onions for modification of styrene-acrylate copolymer based nanocomposites

Styrene acrylate polymer (SAC) nanocomposites with various carbon nanofillers (multiwalled carbon nanotubes MWCNTs and onion like carbon OLC) are manufactured by means of latex based routes. Concentration of the carbon nanofillers is changed in a broad interval starting from 0.01 up to 10 wt. %. Elastic, dielectric and electromagnetic properties of SAC nanocomposites are investigated. Elastic modulus, electrical conductivity and electromagnetic radiation absorption of the investigated SAC nanocomposites increase along with rising nanofiller content. The effect of the addition of anisometric MWCNTs on the elastic properties of the composite is higher than in the case of the addition of OLC. Higher electrical conductivity of the OLC containing nanocomposites is explained with the fact that reasonable agglomeration of the nanofiller can promote the development of electrically conductive network. Efficiency of the absorption of electromagnetic radiation depends on the development of conductive network within the SAC matrix.

Radiation-chemically modified PP/CNT composites

Abstract In this work, the authors studied the effects of electron beam (EB)-induced changes in stress-strain characteristics, heat shrinkage stresses, and structure characteristics on polypropylene (PP) composites containing bisphenol-A-dimethacrylate (BPDMA) as the radiation sensitizer and different contents of multi-walled carbon nanotube (CNT) filler (0–2 wt.%). The effect of stearic acid (SA) as the surface modifier on the improvement of CNT dispersion in the PP matrix was also studied. Initially, PP blends with different contents (up to 10 wt.%) of BPDMA were prepared to determine the effective concentration of the sensitizer for the modification of the PP matrix. PP/BPDMA composites and blends filled with CNTs were irradiated up to 25–50 kGy of radiation doses. The properties of unirradiated compositions and those modified by EB, were compared. Radiation-induced changes were confirmed by gel fraction and by the changes in Fourier transform infrared spectroscopy spectra. The results showed an increase in Young’s modulus, yield strength, and thermal-relaxation stresses for the irradiated PP/CNT compositions grafted with 3 wt.% of BPDMA and compatibilized with SA.