Beata Macherzyńska

Polyurethane/graphene nanocomposites as phase change materials for thermal energy storage

In this work polyurethane/graphene nanocomposites containing segments of poly(ethylene glycol) with defined molecular weight were obtained as new phase change materials for thermal energy storage. The prepared materials were investigated by means of DSC, TG, SEM and ultrasonic non-destructive methods. Enhancements in the thermal stability and thermal conductivity in polyurethane systems modified with graphene were found which is important for thermal energy storage applications. Additionally materials modified with graphene showed lower supercooling in comparison to samples without graphene.

Microscopic Studies of the GC/Poly-NiTMHPP/Nafion Electrochemical Nitric Oxide Sensor

Glassy carbon (GC) discs and platinum microcylindrical electrodes were modified with a layer of nickel(II) tetrakis 3-methoxy-4 hydroxyphenyl porphyrin (poly-TMHPP-Ni) of different loadings (Γ) between 0.6 and 10 nmol/cm2, and subsequently with a Nafion layer. The topography and in some cases the thickness of films were measured by means of contact mode AFM. SEM and optical microscopy observations were used for the comparative studies on a larger scale. The useful range of the coverage with modifying polymer was investigated. The optimal value of loading for the sensor was found to be in the range of 6-8 nmole of poly-TMHPP-Ni per cm2. We observed the Nafion layer uniformity in nanometric scale.

The Influence of Nanohydroxyapatite on the Thermal, Mechanical, and Tribological Properties of Polyoxymethylene Nanocomposites

The influence of nanohydroxyapatite on the glass transition region and its activation energy, as well as on the tribological and mechanical properties of polyoxymethylene nanocomposites, was investigated using DMA, TOPEM DSC, nanoindentation, and nondestructive ultrasonic methods. It was found that the glass transition for unmodified POM was in the lower temperature range than in POM/HAp nanocomposites. Moreover, and activation energy were larger for POM/HAp nanocomposites. Friction coefficient was higher for POM/HAp nanocomposites in comparison to both POM homopolymer and POM copolymer. Simultaneously, the indentation test results show that microhardness is also higher for POM/HAp nanocomposites than for POM. From ultrasonic investigations it was found that the highest values of both longitudinal and transverse propagation waves and Young’s and shear modulus for POM homopolymer (DH) and POM copolymer T2H and their nanocomposites can be attributed to their higher degree of crystallinity in comparison to UH copolymer. Moreover, for POM/HAp nanocomposites with 5% of HAp, ultrasonic longitudinal wave velocity was almost constant even after 1000000 mechanical loading cycles, evidencing an enhancement of mechanical properties by HAp nanoparticles.