Thermal and optical properties of PMMA films reinforced with Nb2O5 nanoparticles.

The article presents the thermal and physical properties of PMMA composite films with the addition of Nb2O5 nanoparticles. The addition of nanoparticles to PMMA mainly influenced the optical transmission and glass transition temperature of composite films compared to pure PMMA. It is clearly visible in the results of the conducted ellipsometric and differential scanning calorimetry tests. X-ray studies showed that the heat treatment of the samples resulted in the ordering of the polymer structure (flattening of the polymer chains). Examining the surface of the samples with scanning electron microscopy, it can be seen that Nb2O5 nanoparticles formed unusual, branched formations resembling "snowflakes".

Forensic Engineering of Advanced Polymeric Materials-Part VII: Degradation of Biopolymer Welded Joints.

Welding technology may be considered as a promising processing method for the formation of packaging products from biopolymers. However, the welding processes used can change the properties of the polymer materials, especially in the region of the weld. In this contribution, the impact of the welding process on the structure and properties of biopolymer welds and their ability to undergo hydrolytic degradation will be discussed. Samples for the study were made from polylactide (PLA) and poly(3-hydroxyalkanoate) (PHA) biopolymers which were welded using two methods: ultrasonic and heated tool welding. Differential scanning calorimetry (DSC) analysis showed slight changes in the thermal properties of the samples resulting from the processing and welding method used. The results of hydrolytic degradation indicated that welds of selected biopolymers started to degrade faster than unwelded parts of the samples. The structure of degradation products at the molecular level was confirmed using mass spectrometry. It was found that hydrolysis of the PLA and PHA welds occurs via the random ester bond cleavage and leads to the formation of PLA and PHA oligomers terminated by hydroxyl and carboxyl end groups, similarly to as previously observed for unwelded PLA and PHA-based materials.

Degradability in vitro of polyurethanes based on synthetic atactic poly[(R,S)-3-hydroxybutyrate].

The aim of the present study was to determine the degradability of aliphatic polyurethanes, based on a different amount of synthetic, atactic poly[(R,S)-3-hydroxybutyrate] (a-PHB), in hydrolytic (phosphate buffer) and oxidative (H2O2/CoCl2) solutions. The soft segments were built with atactic poly[(R,S)-3-hydroxybutyrate] and polycaprolactone or polyoxytetramethylenediols, whereas hard segments were the reaction product of 4,4'-methylenedicyclohexyl diisocyanate and 1,4-butanediol.The selected properties - density and morphology of polymer surfaces - which could influence the sensitivity of polymers to degradation processes - were analyzed.The analysis of molecular mass (GPC), thermal properties (DSC) and the sample weight changes were undertaken to estimate the degree of degradability of polymer samples after incubation in environments studied.Investigated polyurethanes were amorphous with the very low amount of crystalline phases of hard segments.The polyurethane synthesized with a poly[(R,S)-3-hydroxybutyrate] and polyoxytetramethylenediol at a molar ratio of NCO:OH=3.7:1 (prepolymer step) appeared as the most sensitive for both degradative solutions. Its weight and molecular mass losses were the highest in comparison to other investigated polyurethanes.It could be expected that playing with the amount of poly[(R,S)-3-hydroxybutyrate] in polyurethane synthesis the rate of polyurethane degradation after immersion in living body would be modeled.