The present study is focused on polylactic acid (PLA) blending with bio nanoadditives, such as Tonsil^® (clay) and Aerosil^®, to obtain nanocomposites for a new generation of food packaging. The basic composition was enhanced using Sorbitan oleate (E494) and Proviplast as plasticizers, increasing the composite samples’ stability and their mechanical strength. Four mixtures were prepared: S1 with Tonsil^®; S2 with Aerosil^®; S3 with Aerosil^® + Proviplast; and S4 with Sabosorb. They were complexly characterized by FT-IR spectroscopy, differential scanning calorimetry, mechanical tests on different temperatures, and absorption of the saline solution. FTIR shows a proper embedding of the filler component into the polymer matrix and DSC presents a good stability at the living body temperature for all prepared samples. Micro and nanostructural aspects were evidenced by SEM and AFM microscopy, revealing that S3 has the most compact and uniform filler distribution and S4 has the most irregular one. Thus, S3 evidenced the best diametral tensile strength and S4 evidenced the weakest values. All samples present the best bending strength at 18 °C and fair values at 4 °C, with the best values being obtained for the S1 sample and the worst for S4. The lack of mechanical strength of the S4 sample is compensated by its best resistance at liquid penetration, while S1 is more affected by the liquid infiltrations. Finally, results show that PLA composites are suitable for biodegradable and disposable food packages, and the desired properties could be achieved by proper adjustment of the filler proportions.

(1) Background: This study investigated the influence of Bis-GMA, TEGDMA, UDMA, and two different polyethylene glycol (PEG)-containing, UDMO-based co-monomers on the Young’s modulus and flexural strength, degree of methacrylate C=C double bond conversion and residual monomer elution of experimental dental resins. (2) Methods: Urethane methacrylate-based monomer was synthesised via a radical chain growth polymerization mechanism using PEG in order to improve the mechanical properties. Dental resins were formulated using Bis-GMA, UDMA, or UDMO as base monomers combined with TEGDMA as a dilution monomer and DMAEM + CQ as the photo-initiator system. Degree of conversion (DC), mechanical properties, and residual monomer content of light-activated methacrylate resin formulations were evaluated and statistically analysed by ANOVA and a Tukey’s test. (3) Results: PEG-containing UDMO resins had lower Young’s modulus and elastic strength than UDMA-derived resin for all irradiation times. The highest DC (67,418%) was observed for the PEG-containing UDMO-based resin formulation when light cured for 40 s. For all samples, DC increased with the photo-polymerization time. The amount of residual monomer decreased after increasing the light-curing period from 20 to 40 s, resin with UDMO content 0.01 mol of PEG having the smallest amount of free eluted monomer. (4) Conclusions: A strong structure–property relationship exists in photo-cured dimethacrylate-based dental resins. The time and quantity of the photochemical initiation system can influence the physical–mechanical properties of the resins but also the monomers in their composition.

The purpose of the present study is to analyze the effect of the new nanofiller type graphene–gold nanoparticles on the surface structure and surface properties of some dental nanocomposites based on BisGMA/triethyleneglicol dimethacrylate matrix. Materials used in our study were three experimental nanocomposites, two of them based on graphene–gold nanoparticles as filler of different percent. As reference material, a commercial dental nanocomposite product named Herculite XRV Ultra was used. FTIR-ATR spectroscopy was used to determine the residual double bonds and the degree of conversion (DC) after 1 and 21 days of immersion in distilled water at 37 °C. The difference in DC between the experimental materials was statistically analyzed by one tail, paired Student’s t-Tests, using Graph Pod. Surface properties were evaluated through surface free energy using contact angle measurement while roughness and topography was assessed using Atomic Force Microscopy (AFM). To determine the amount of filler particles and thermal behavior of organic matrix, the nanocomposites were investigated by thermal analysis. According to the experimental results, the dental nanocomposites with highest percent in graphene–gold nanoparticles present a better value for the surface free energy. AFM investigations reveal differences in the term of roughness properties and suggest that in order to improve the surface properties is necessary to use a higher percent of graphene–gold nanoparticles as filler. The degradation process of major nanocomposites constituents is observed at temperatures between 240 and 620 °C. Entire results sustain this, but the future studies in order to evaluate the biological properties of the experimental nanocomposites will be made.

Brackets are metallic dental devices that are very often associated with acidic soft drinks such as cola and energy drinks. Acid erosion may affect the bonding between brackets and the enamel surface. The purpose of this study was to investigate the characteristics of brackets’ adhesion, in the presence of two different commercially available drinks. Sixty human teeth were divided into six groups and bonded with either resin-modified glass ionomer (RMGIC) or resin composite (CR). A shared bond test (SBS) was evaluated by comparing two control groups with four other categories, in which teeth were immersed in either Coca-Cola^TM or Red Bull^TM energy drink. The debonding between the bracket and enamel was evaluated by SEM. The morphological aspect correlated with SBS results showed the best results for the samples exposed to artificial saliva. The best adhesion resistance to the acid erosion environment was observed in the group of teeth immersed in Red Bull^TM and with brackets bonded with RMGIC. The debonded structures were also exposed to Coca-Cola^TM and Red Bull^TM to assess, by atomic force microscopy investigation (AFM), the erosive effect on the enamel surface after debonding and after polishing restoration. The results showed a significant increase in surface roughness due to acid erosion. Polishing restoration of the enamel surface significantly reduced the surface roughness that resulted after debonding, and inhibited acid erosion. The roughness values obtained from polished samples after exposure to Coca-Cola^TM and Red Bull^TM were significantly lower in that case than for the debonded structures. Statistical results evaluating roughness showed that Red Bull^TM has a more erosive effect than Coca-Cola™. This result is supported by the large contact surface that resulted after debonding. In conclusion, the prolonged exposure of the brackets to acidic drinks affected the bonding strength due to erosion propagation into both the enamel–adhesive interface and the bonding layer. The best resistance to acid erosion was obtained by RMGIC.

This study focuses on the development of bioactive packaging materials by incorporating grape pomace and copper particles into polylactic acid (PLA) composites. The goal is to increase the shelf life of packaged foods while benefiting the health of consumers through the use of these active materials. 6 recipes of composite materials based on polylactic acid and Proviplast 2624 plasticizer were obtained. The additives added were: grape pomace, added at 0.5%, 1% and 1.5%, and copper particles, formed using PEG 600 + CuSO₄, added at 2%, 5% and 8%. Material characterization techniques: FTIR Spectroscopy, used to study the chemical structure. Differential scanning calorimetry (DSC): examined thermal transitions such as glass transition and melting temperatures. Thermogravimetric analysis (TGA) and differential thermogravimetry (DTG): evaluated thermal stability and degradation temperatures. Scanning electron microscopy (SEM) and atomic force microscopy (AFM): analyzed the surface morphology and structure. Mechanical tests: evaluated tensile strength, elongation at break and flexibility. Thermal property analyzes revealed that the additives acted as plasticizers, reducing the intermolecular forces between PLA chains, which decreased the glass transition temperature (Tg), cold crystallization temperature (Tcc) and melting temperature (Tm). The addition of grape pomace and copper particles decreased the degradation temperature of PLA composites, indicating a slight reduction in thermal stability. The transformation temperatures changed and the nature of the thermal transitions (exothermic or endothermic) varied with additive concentrations. Mechanical properties indicated a reduction in tensile strength with increasing additive concentration. Elongation at break and longitudinal modulus of elasticity increased significantly, especially with grape pomace, improving the flexibility of PLA. These changes indicate that the material can absorb more energy before breaking, making it more ductile and more suitable for flexible packaging applications. Increased flexibility and improved thermal resistance ensure that these materials can withstand the demands of packaging, handling and shipping. The combination of improved flexibility, thermal resistance and moderate tensile strength makes these PLA-based composites incorporated with grape pomace or copper particles, enhance the aspect of sustainability by recycling agricultural waste, making the material both ecological and functional, making it a viable option for active food packaging.

Ceramic slurry wastes have a significant hazardous potential when dumped. Their recycling as raw material is a sustainable approach for the development of nature-friendly applications. The microstructure and mechanical properties play a key role in the success of this sustainable recycling. Ceramic slurry samples resulting from the wall and floor tiles production facility were analyzed. The mineral composition was investigated by XRD combined with mineralogical microscopy and the microstructure was investigated by SEM microscopy coupled with EDX spectroscopy and elemental mapping. The ceramic slurry contains: quartz, kaolinite, mullite and small amounts of lepidocrocite. Quartz and mullite particles have sizes in the range of 5–100 μm and kaolinite has small particles of around 1 to 30 μm. Iron hydroxide crystallized as lepidocrocite is finely distributed among kaolinite aggregates. It makes the slurry unable to be reused in the technological process because of the glaze staining risk, but it does not affect the material cohesion. Thus, the cylindrical samples were prepared at progressive compactions rates as follows: 1808.55; 1853.46; 1930.79 and 2181.24 kg/m³ and dried. Thereafter, were subjected to a compression test with a lower compression strength of 0.75 MPa for lower density and a higher strength of 1.36 MPa for the higher density. Thus, slurry compaction enhances the kaolinite binding ability. The Young’s Modulus slightly decreases with the compaction increasing due to local microstructure rigidizing. This proves the binding ability of kaolinite, which properly embeds quartz and mullite particles into a coherent and resistant structure. The fractography analysis reveals that fracture starts on the internal pores at low compaction rates and throughout the kaolinite layer in the samples with high compactness. The observed properties indicate that the investigated ceramic slurry is proper as a clay-based binder for sustainable ecological buildings, avoiding the exploitation of new clay quarries. Also, it might be utilized for ecological brick production.