Łukasz Piszczyk

Polyurethane Nanocomposites Containing Reduced Graphene Oxide, FTIR, Raman, and XRD Studies

Recently, graphene and other graphene-based materials have become an essential part of composite science and technology. Their unique properties are not only restricted to graphene but also shared with derivative compounds like graphene oxide, reduced graphene oxide, functionalized graphene, and so forth. One of the most structurally important materials, graphene oxide (GO), is prepared by the oxidation of graphite. Though removal of the oxide groups can create vacancies and structural defects, reduced graphene oxide (rGO) is used in composites as effective filler similar to GO. Authors developed a new polyurethane nanocomposite using a derivative of grapheme, thermally reduced graphene oxide (rGO), to modify the matrix of polyurethane elastomers, by rGO.

Processing and structure–property relationships of natural rubber/wheat bran biocomposites

In this work, wheat bran was used as cellulosic filler in biocomposites based on natural rubber. The impact of wheat bran content [ranging from 10 to 50 parts per hundred rubber (phr)] on processing, structure, dynamic mechanical properties, thermal properties, physico-mechanical properties and morphology of resulting biocomposites was investigated. For better characterization of interfacial interactions between natural rubber and wheat bran, achieved results were compared with properties of biocomposites filled with commercially available cellulosic fillers—wood flour and microcellulose. It was observed that wheat bran, unlike commercial cellulosic fillers, contains high amount of proteins, which act like plasticizers having profitable impact on processing, physical, thermo-mechanical and morphological properties of biocomposites. This is due to better dispersion and distribution of wheat bran particles in natural rubber, which results in reduction of stiffness and porosity of the biocomposites. Regardless of cellulosic filler type, Wolff activity coefficient was positive for all studied biocomposites implying reinforcing effect of the applied fillers, while tensile strength and elongation at break decreased with increasing filler content. This phenomenon is related to restricted strain-induced crystallization of NR matrix due to limited mobility of polymer chains in the biocomposites. Furthermore, this explains negligible impact of particle size distribution, chemical composition and crystallinity degree of applied cellulosic filler on static mechanical properties of highly-filled NR biocomposites. The conducted investigations show that wheat bran presents interesting alternative for commercially available cellulosic fillers and could be successfully applied as a low-cost filler in polymer composites.

Morphology and the physical and thermal properties of thermoplastic polyurethane reinforced with thermally reduced graphene oxide

Abstract In this study, thermally reduced graphene oxide (TRG)-containing polyurethane nanocomposites were obtained by the extrusion method. The content of TRG incorporated into polyurethane elastomer systems equaled 0.5, 1.0, 2.0 and 3.0 wt%. The morphology, static and dynamic mechanical properties, and thermal stability of the modified materials were investigated. The application of TRG resulted in a visible increase in material stiffness as confirmed by the measurements of complex compression modulus (E′) and glass transition temperature (Tg). The Tg increased with increasing content of nanofiller in the thermoplastic system. The addition of thermally reduced graphene oxide had a slight effect on thermal stability of the obtained materials. The incorporation of 0.5, 1.0, 2.0 and 3.0 wt% of TRG into a system resulted in increased char residues compared to unmodified PU elastomer. Also, this study demonstrated that after exceeding a specific amount of TRG, the physicomechanical properties of modified materials start to deteriorate.

Polyurethane/ground tire rubber composite foams based on polyglycerol: Processing, mechanical and thermal properties

During the synthesis of rigid polyurethane foams, petrochemical polyol was substituted with polyglycerol, the product of thermo-catalytic polycondensation of waste glycerol, resulting from biodiesel production. Two types of ground tire rubbers, untreated and thermo-mechanically reclaimed, were used to obtain “green” polyurethane-polyglycerol composite foams. Samples were prepared by a single-step method for the ratio of NCO/OH groups equal to 2. Foams containing different types of fillers showed noticeably various appearances, which suggested significant differences in the matrix–filler interactions between materials modified with untreated and reclaimed ground tire rubber. Addition of rubber particles shortened the processing time by more than 20 s and reduced the temperature during synthesis. Incorporation of ground tire rubber increased the size of the cells in comparison to unmodified foam. Modifications of rigid polyurethane foams resulted in the increase of apparent density and compressive strength even by 40% compared to neat foam. Enhancement was stronger for samples containing thermo-mechanically reclaimed ground tire rubber as a result of better developed surface of filler particles and their interfacial interactions with polyurethane matrix. Prepared polyurethane foams filled with untreated rubber particles also showed slightly enhanced thermal stability compared to neat foam.

Structure, Mechanical, Thermal and Fire Behavior Assessments of Environmentally Friendly Crude Glycerol-Based Rigid Polyisocyanurate Foams

In this work, rigid polyisocyanurate foams were prepared at partial substitution (0–70 wt%) of commercially available petrochemical polyol, with previously synthesized biopolyol based on crude glycerol and castor oil. Influence of the biopolyol content on morphology, chemical structure, static and dynamic mechanical properties, thermal insulation properties, thermal stability and flammability was investigated. Incorporation of 35 wt% of crude glycerol-based polyol had reduced average cell size by more than 30% and slightly increased closed cell content, simultaneously reducing thermal conductivity coefficient of foam by 12% and inhibiting their thermal aging. Applied modifications showed also positive impact on the mechanical performance of rigid foams. Increase of crosslink density resulted in enhancement of compressive strength by more than 100%. Incorporation of prepared biopolyol resulted in enhancement of thermal stability and changes in degradation pathway. Up to 35 wt% share of crude glycerol-based polyol, foams showed similar flammability as reference sample, which can be considered very beneficial from the environmental point of view.

Thermal and Mechanical Properties of Microporous Polyurethanes Modified with Reduced Graphene Oxide

Microporous polyurethanes (MPU) were modified by adding 0.25%–1.25 wt% of reduced graphene oxide (RGO). The materials were prepared without solvent via in situ polymerization. From a technological point of view, it is very important to obtain functional materials by using reacting compounds only. The thermal characteristics of obtained MPU were investigated using TGA, DSC, and DMA techniques. In comparison to nonmodified microporous polyurethane, the thermal stability and mechanical properties of the modified systems have significantly improved. The temperature corresponding to the maximum degradation rate () for nanocomposites containing 1% and 1.25 wt% of RGO was 51°C higher than that observed for pure microporous PU system. The increase of tensile strength was also observed for matrix with the addition of 0.5 wt% RGO nanofiller.

Mechanical, Structural and Diffusion Studies of Hydrogel Polyurethane Nanocomposites Containing Modified Montmorillonite

Polyurethane hydrogels nanocomposites belong to a new class of hybrid biomaterials with unique swelling properties in comparison to unmodified hydrogels. These materials combine the typical properties of gels (elasticity and permeability) with the reinforcing properties of clay nanoparticles. Therefore, nanohydrogels might be applied in pharmacy for the controlled release and delivery of drugs and other biologically active agents, as well as in cosmetology as strong absorbents. We synthesized nanohydrogel polyurethanes with Cloisite® 30B organically modified clay nanoparticles of montmorillonite to obtain hybrid materials possessing great swelling properties. These materials were studied by XRD, DMA, and water absorption capacity measurements. The synthesis procedure yielded stable and homogeneous hydrogel materials. Addition of clay nanoparticles causes an increase in the absorptivity of water molecules in the polyurethane matrix.

Foamed Polyurethane Composites With Different Types of Ash – Morphological, Mechanical and Thermal Behavior Assessments

Incorporation of two types of ash particles into flexible polyurethane foams has been investigated, wood ash from gasification process and fly ash resulting from coal burning in power plant. Samples were modified with 5, 10 and 15 wt% of fillers. Structure, mechanical and thermal properties of obtained foams were investigated. Incorporation of both types of ash particles resulted in materials showing satisfactory mechanical properties, simultaneously decreasing their density. Addition of fly ash inhibited noticeably thermal degradation of material, because of the thermal insulation effect of gas trapped in the spherical ash particles. Results of research show that fly ash can be successfully used as a modifier of thermal properties in polyurethane foams, enhancing the economical aspect of the production through the decrease of materials density and incorporation of low cost filler.

The Study on Application of Biopolyols Obtained by Cellulose Biomass Liquefaction Performed with Crude Glycerol for the Synthesis of Rigid Polyurethane Foams

In this work rigid polyurethane foams (PUR) were obtained by replacement of 0–70 wt% of petrochemical polyol with bio-polyol obtained via cellulose liquefaction in presence of crude glycerol. The foams with different content of a bio-polyol were prepared by single step method for NCO/OH ratio equals 1.5. The prepared materials were analyzed in terms of their morphology, chemical structure, thermal stability and basic physical and mechanical properties. The effects of photo-oxidative and thermo-oxidative aging on chemical structure, apparent density and mechanical properties of the biomass based rigid polyurethane foams were investigated and discussed.

Two-step Conversion of Crude Glycerol Generated by Biodiesel Production into Biopolyols: Synthesis, Structural and Physical Chemical Characterization

In this work biopolyols were synthesized via two-step process from crude glycerol and castor oil. For better evaluation of analyzed process, the impact of its time and temperature on the structure and properties of biopolyols was determined. Obtained results fully justified conducting of synthesis in two steps. Prepared materials were characterized by hydroxyl value and water content comparable to polyols industrially applied in manufacturing of polyurethane materials. Synthesized biopolyols were characterized in terms of their chemical structure using spectroscopic techniques: Fourier transform infrared (FTIR) spectroscopy and nuclear magnetic resonance spectroscopy. Obtained data confirmed the influence of synthesis’ parameters on the chemical structure of prepared biopolyols and correlated with their other parameters. On both stages of reaction, collected by-products were also analyzed with FTIR spectroscopy.