Influence of Sb2O3 particles as filler on the thermal stability and flammability properties of poly(methyl methacrylate) (PMMA)

Mechanical and thermal properties of PMMA resin composites for interim fixed prostheses reinforced with calcium β-pyrophosphate

Interim restorations are essential in fixed prosthodontics as they provide temporary protection of teeth before the insertion of the permanent restoration. Poly(methyl methacrylate) (PMMA) is widely used in the fabrication of interim-fixed restorations as it is a biocompatible material with a lot of convenient properties. However, it exhibits low impact and tensile strength and therefore it is necessary to be reinforced. Calcium β-pyrophosphate (β-CPP) is considered a promising reinforcing material for dental applications, especially for enamel regeneration due to its stability at low pH and its low wear rate. The aim of this study was to manufacture PMMA/β-CPP composites suitable for fixed-interim restorations and to study their mechanical and thermal properties. In order to enhance β-CPP dispersion into PMMA matrix, ball-milling was performed for 1 or 6 h. Three-point bending test was performed to study flexural strength, Dynamic Mechanical Analysis (DMA) to reveal the elastic and viscous moduli along with T_g, Fourier Transform Infrared Spectroscopy (FTIR) and X-Ray Diffraction Analysis (XRD) to investigate the structure of the materials and SEM for the morphological evaluation of both composite powders and polymerized specimens. Thermogravimetric Analysis (TGA) and Differential Scanning Calorimetry (DSC) experiments were performed to study their thermal properties. A statistically significant increase in flexural strength was found in the 0.5, 0.75 and 1% composite groups after 6 h ball-milling, relative to the control, with the 6 h ball milling mixed specimens, presenting the highest flexural strength values. The brittle fracture type was common to all groups. An obvious improvement of the mechanical properties and a slight improvement in the thermal stability of the composite materials values were also observed as β-CPP content was increased, while T_g values were statistically not-affected.

Assessing thermal behaviours of cellulose and poly(methyl methacrylate) during co-pyrolysis based on an unified thermoanalytical study

The objective of this study was to evaluate pyrolysis and co-pyrolysis behavior of cellulose and poly(methyl methacrylate) (PMMA) and examine the kinetics of the processes by using thermogravimetric analysis (TGA) coupled with FT-IR spectrometry. For this purpose, non-isothermal experiments were carried out using different heating rates and three prominent iso-conversional methods were used to obtain kinetic parameters at various extents of conversions from 0.1 to 0.9. Blending PMMA with cellulose had a marked effect on the process. The results of co-pyrolysis using a blending ratio of 50 wt% PMMA indicated that the highest rate of pyrolytic transformation was achieved at a conversion degree of 0.5 while activation energy ranged from 188.1 to 364.3 kJ/mol. The most intensive gas release during cellulose pyrolysis was CO₂. Co-pyrolysis was more complicated than that of pyrolysis of cellulose and PMMA due to depolymerization and radical interactions.

Facile synthesis of novel nest-shaped Sb2O3 micro/nanostructures and their optical properties

Novel nest-shaped Sb₂O₃ micro/nanostructure has been successfully prepared, and its optical properties have been investigated.