Surface and structural properties of medical acrylonitrile butadiene styrene modified with silver nanoparticles

Acrylonitrile butadiene styrene/silver nanoparticles (ABS/AgNPs) composites were manufactured through the plastic processing method. Three different matrices were used to obtain polymer and composite samples containing 0.5 wt {\%} and 1.0 wt {\%} of silver nanoparticles, respectively. The aim of this study was to examine physicochemical properties and stability of the materials in the in vitro conditions for two years. The results showed that composites made from amorphous matrices had comparable mechanical properties after incorporation of AgNPs. The values of Young modulus and tensile strength increased after the first and second year of investigation. Silver nanoparticles did not alter the surface parameters-e.g., roughness and contact angle also retained stable values after the in vitro incubation in water solution. The scanning electron observation revealed homogeneous distribution of silver modifier in all the matrices. The 24-month incubation of materials proved the stability of the composites microstructure. The DSC analysis revealed that addition of AgNPs may decrease glass transition temperature of the composite materials which was also reduced after 12 and 24 months of incubation. The attenuated total reflectance-Fourier transform infrared (ATR-FTIR) spectroscopic studies did not indicate significant changes in the ABS matrices either upon their modification with AgNPs or after the long-term testing. The conducted studies proved that all the composites are stable and may be used for a long-term working period

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, ΔCp 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

Comparison of phase structures and surface free energy values for the coatings synthesised from linear polyurethanes and from waterborne polyurethane cationomers

WAXS, DSC and AFM methods were employed to compare phase structures of the coatings obtained from waterborne polyurethane cationomers which had been synthesised in the reaction of some diisocyanates (MDI, IPDI, TDI and HDI) with polyoxyethylene glycols (M = 600 and 2,000) and butane1,4-diol or N-methyl- or N-butyldiethanolamine and 2,2,3,3-tetrafluoro-1,4-butanediol. The structures were also analysed of the coatings derived from linear polyurethanes which had been synthesised on the basis of similar raw materials. Better rigidity was found for generally amorphous cationomer coats. Changes were discussed in the surface free energy (SFE) values and in their components, as calculated independently with the use of the van Oss–Good and Owens–Wendt methods. Polyurethane coats turned out more hydrophobic as compared to cationomer ones. In both coat types, fluorine incorporated into cationomers contributed to lower SFE values: from 50 down to about 30 mJ/m2

Preparation, Characterization, and Bioactivity Evaluation of Polyoxymethylene Copolymer/Nanohydroxyapatite-g-Poly(ε-caprolactone) Composites

In this work, nanohydroxyapatite (HAp) was functionalized with poly(ε-caprolactone) (PCL), using 1,6-hexamethylene diisocyanate (HDI) as a coupling agent, and then incorporated into the polyoxymethylene copolymer (POM) matrix using the extrusion technique. The obtained POM/HAp-g-PCL composites were investigated using FTIR, DSC, TOPEM DSC, and TG methods. Mechanical properties were studied using destructive and non-destructive ultrasonic methods, wettability, and POM crystallization kinetics in the presence of HAp-g-PCL. Moreover, preliminary bioactivity evaluation of the POM/HAp-g-PCL composites was performed using the Kokubo method. It was found that the introduction of HAp-g-PCL to the POM matrix has a limited effect on the phase transitions of POM as well as on its degree of crystallinity. Importantly, HAp grafted with PCL caused a significant increase in the thermal stability of the POM, from 292 °C for pristine POM to 333 °C for POM modified with 2.5% HAp-g-PCL. If unmodified HAp was used, a distinct decrease in the thermal stability of the POM was observed. Crystallization kinetic studies confirmed that HAp-g-PCL, in small amounts, can act as a nucleating agent for the POM crystallization process. Moreover, incorporation of HAp-g-PCL, although slightly decreasing the mechanical properties of POM composites, improved the crucial parameter in biomedical applications, namely the in vitro bioactivity

Polymer Nanocomposites: Preparation, Characterisation and Applications

Polymer nanocomposites are an interesting and rapidly growing class of novel materials with enhanced properties, and these enhancements can be observed even at low nanofiller loading [...

Fire Retardant Phase Change Materials—Recent Developments and Future Perspectives

The accumulation of thermal energy in the form of latent heat of phase transition using phase change materials (PCMs) is one of the most attractive and studied research areas with huge application potential in both passive and active technical systems. The largest and most important group of PCMs for low-temperature applications are organic PCMs, mainly paraffins, fatty acids, fatty alcohols, and polymers. One of the major disadvantages of organic PCMs is their flammability. In many applications such as building, battery thermal management, and protective insulations, the crucial task is to reduce the fire risk of flammable PCMs. In the last decade, numerous research works have been performed to reduce the flammability of organic PCMs, without losing their thermal performance. In this review, the main groups of flame retardants, PCMs flame retardation methods as well as examples of flame-retarded PCMs and their application areas were described