Characterization of Blend PA6 +EPDM (60/40) by Tensile Tests

This paper presents a characterization of PA6 and the blend PA6+EPDM (60/40) by tensile tests in order to evaluate several mechanical properties for impact resistance applications. Results were found to be dependend on test rate (10 mm/min, 250 mm/min and 1000 mm/mm). SEM investigation point out a homogenous structure. The blend has better value of energy at break, for the higher test speed: for v=250 mm/min this characteristic has the value of energy at break 29.7 J and the blend has 76.3 J. At 1000 mm/min, PA6 has this charcateristic of 20 J, but for the blend, it is almost insensitive for the two higher test speeds (76.3 J at 250 mm/min and 72.4 J at 1000 mm/min, respectively) as compared to the neat polymer that decreases this feature when thr test spee increases. At the lowest teste speed, the values of energy at break for the materials in this study are close (90.2 J for PA6 and 87.7 J for the blend). The results from tensile tests pointed out that the formulated blend is recommended for impact resistance applications.

Conductive and Edge Retaining Embedding Compounds: Influence of Graphite Content in Compounds on Specimen’s SEM and EBSD Performance

Since marginal sharpness is often an issue in metallographic samples preparation, various mounting compounds are commercially available which address these issues. Nevertheless, the conductivity of such products is not sufficient for electron backscatter diffraction measurements (EBSD) and products which are electrically conductive often result in a lack of marginal sharpness. Therefore, this study is focussed on the modification of commercially available embedding compounds (epoxy based and phenolic based hot embedding compounds) with graphite to increase their electrical conductivity. To verify the applicability of the modified embedding compounds, the austenitic steel grade 1.4301 was chosen for investigation via scanning electron microscopy and EBSD. Results indicate a good performance during SEM-investigations of the epoxy-based resins, even at 0 wt.-% graphite contents, whereas the phenolic resin-based embedding compound is only applicable for SEM-investigation > wt.-5 % of graphite. Best performance at EBSD measurements were achieved with phenolic resin based hot mounting compounds with glass fibres and an addition > 10 wt.-% graphite.

SEM Evaluation of Endosequence BC Sealer Hiflow in Different Environmental Conditions

The aim of the present study is to evaluate the setting and sealant ability of two different bioceramic sealers in two different environmental conditions: humid and wet environment. Ex vivo root canal treatment was performed on 24 freshly extracted teeth. Irrigation was performed with Niclor NaOCl 5% and EDTA 17%, then obturated with a bioceramic sealer in the two different environmental conditions listed above. Furthermore, scanning electron microscope (SEM) investigation was performed to verify the presence of gaps and the setting ability of the two sealers in two different environmental conditions was evaluated. While presence of gaps was found mainly in the wet specimens, on the other hand, regarding the setting ability, there is no statistically significant difference between the two different samples. Therefore, even if humid conditions represent the gold standard in terms of lower gaps dimension, since there is no methodology standardizing the drying procedure of the root canal, it is compulsory to investigate the sealing ability of the bioceramic sealers, even in wet conditions. Thanks to the findings shown in the present study, it is demonstrated that even in wet conditions the ability of the sealer to set does not change and such clinical situation could affect the bioceramic sealer protocol.

Tribology of Polymer Blends PBT + PTFE

This paper presents results on tribological characteristics for polymer blends made of polybutylene terephthalate (PBT) and polytetrafluoroethylene (PTFE). This blend is relatively new in research as PBT has restricted processability because of its processing temperature near the degradation one. Tests were done block-on-ring tribotester, in dry regime, the variables being the PTFE concentration (0%, 5%, 10% and 15%wt) and the sliding regime parameters (load: 1 N, 2.5 N and 5 N, the sliding speed: 0.25 m/s, 0.5 m/s and 0.75 m/s, and the sliding distance: 2500 m, 5000 m and 7500 m). Results are encouraging as PBT as neat polymer has very good tribological characteristics in terms of friction coefficient and wear rate. SEM investigation reveals a quite uniform dispersion of PTFE drops in the PBT matrix.