Polyoxymethylene (POM)- and polyamide 6 (PA6)-based biocomposites were investigated in order to evaluate the reinforcing efficiency of a biocarbon filler (BioC). Both types of composites were prepared by melt-blending extrusion with 10, 20, and 30 wt% of BioC. Samples were prepared by the injection molding method and subjected to a detailed analysis consisting of mechanical and thermo-mechanical tests, thermal analysis, and microscopic observations. In order to evaluate the durability of the composite, accelerated thermal and hydrothermal tests were performed. The results reveal significant differences between PA6- and POM-based composites, both in terms of mechanical properties and fracture mechanisms. Water uptake tests confirmed the strong hygrophytic character of PA6-based composites; for the hydrophobic POM-based composites, the increased water uptake suggests strong moisture adsorption of the biocarbon. A heat aging test revealed that the exposure to elevated temperatures did not lead to a significant deterioration of properties for POM- and PA6-based materials.

A comparative study of biocarbon reinforced polyoxymethylene and polyamide: materials performance and durability

This study focuses on the characterization of 3D printed parts by fused deposition modelling (FDM) technique made from a composite filament, highly loaded of stainless-steel microparticles, prepared at different infill density (0, 50, 100%). Thermo-mechanical properties, morphological aspects and heat transport behaviour of the developed specimens have been investigated by dynamic-mechanical analysis (DMA), thermal diffusivity measurements and scanning electron microscopy (SEM). Experimental results allowed to attest a drastic reduction of storage modulus in the range of testing temperatures by reducing the infill density. In the meantime, an increment of dissipation factor was shown in lesser stiff samples at temperatures near to the ambient. The same increasing trend did not appear in the case of thermal diffusion that showed closer values for samples at 0 and 50% of infill, and an augment in the case of infilling level of 100%. This outcome, explained through SEM pictures, was attributed to the difficulty in realization of perfect empty internal structures within 3D parts. A supporting analysis by IR spectroscopy was conducted on the composite surface to gain qualitative information about constituting polymer filament. Further considerations on the porosity of systems have been obtained elaborating SEM micrographs with ImageJ software.

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Characterization of 3D Printed Highly Filled Composite: Structure, Thermal Diffusivity and Dynamic-mechanical Analysis

Polyoxymethylene (POM)- and polyamide 6 (PA6)-based biocomposites were investigated in order to evaluate the reinforcing efficiency of a biocarbon filler (BioC). Both types of composites were prepared by melt-blending extrusion with 10, 20, and 30 wt% of BioC. Samples were prepared by the injection molding method and subjected to a detailed analysis consisting of mechanical and thermo-mechanical tests, thermal analysis, and microscopic observations. In order to evaluate the durability of the composite, accelerated thermal and hydrothermal tests were performed. The results reveal significant differences between PA6- and POM-based composites, both in terms of mechanical properties and fracture mechanisms. Water uptake tests confirmed the strong hygrophytic character of PA6-based composites; for the hydrophobic POM-based composites, the increased water uptake suggests strong moisture adsorption of the biocarbon. A heat aging test revealed that the exposure to elevated temperatures did not lead to a significant deterioration of properties for POM- and PA6-based materials. 

A comparative study of biocarbon reinforced polyoxymethylene and polyamide: Materials performance and durability

Due to the low stability of oxymethylene units and their high heat sensitivity, polyoxymethylene (POM) shows weak thermal resistance. Therefore, by using a stabilizer the thermal stability of POM w...

Thermal stabilization of polyoxymethylene by copolymerization and modified phenolic stabilizer: examining the effects of catalyst, retardant, and stabilizer

Polyoxymethylene (POM) and graphene nanoplatelets (GNP) nanocomposites were produced and their thermal properties investigated by thermogravimetric analysis (TGA) and differential scanning calorime...

Polyoxymethylene/graphene nanocomposites: thermal, crystallization, melting and rheological behavior:

Nanostructured hydroxyapatite (HA) functionalized with poly(ethylene glycol) (HA-g-PEG) of different molar mass was used as a thermal stabilizer to prepare polyoxymethylene (POM) composites by a melt processing method. The chemical and crystalline structure of (HA-g-PEG) and POM/HA-g-PEG composites was investigated by means of FTIR and XRD. The thermal properties, degree of crystallinity, and melting behaviour of POM-based composites were analysed with TG, DSC, and TOPEM DSC methods. The tensile strength, Young’s modulus, toughness, and wettability of POM were investigated as well. A preliminary assessment of bioactivity, in vitro chemical stability, and formaldehyde release from POM/HA-g-PEG composites by Schiff’s test was also performed. An SEM/EDX method was used to observe the morphology of POM/HA-g-PEG composites. The results indicate that the addition of 1% HA-g-PEG slightly increases the melting temperature and degree of crystallinity. In small amounts, HA-g-PEG particles probably act as nucleating agents for the POM crystallization process. Incorporation of 5% HA-g-PEG to POM caused a decrease in the crystallinity of the polymer matrix, as a result, some mechanical properties of POM/HA-g-PEG composites also decreased. The thermal stability of POM/HA-g-PEG composites improved significantly from 309°C for unmodified POM to 342°C for POM/10.0% HA-g-PEG 600. The most effective thermal stabilizer was synthesized with the lowest mass-average molar mass PEG. The in vitro bioactivity test confirmed that, as the average molar mass of PEG in HA-g-PEG hybrids increased, POM-based composites indicated higher bioactivity. The in vitro chemical stability analysis results showed that both the POM matrix and the HA-g-PEG additive remain stable during the whole incubation time. Importantly, after seven days of dynamic incubation, no formaldehyde was detected in all filtrates, which is crucial in biomedical applications, among others.

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Thermal Stabilization of Polyoxymethylene by PEG-Functionalized Hydroxyapatite: Examining the Effects of Reduced Formaldehyde Release and Enhanced Bioactivity

Ewelina Karaś

Papers

Thermal Stabilization of Polyoxymethylene by PEG-Functionalized Hydroxyapatite: Examining the Effects of Reduced Formaldehyde Release and Enhanced Bioactivity