The effects of nano-silver loaded zirconium phosphate on antibacterial properties, mechanical properties and biosafety of room temperature curing PMMA materials

Polymethyl methacrylate (PMMA) frequently features in dental restorative materials due to its favorable properties. However, its surface exhibits a propensity for bacterial colonization, and the material can fracture under masticatory pressure. This study incorporated commercially available RHA-1F-II nano-silver loaded zirconium phosphate (Ag-ZrP) into room-temperature cured PMMA at varying mass fractions. Various methods were employed to characterize Ag-ZrP. Subsequently, an examination of the effects of Ag-ZrP on the antimicrobial properties, biosafety, and mechanical properties of PMMA materials was conducted. The results indicated that the antibacterial rate against Streptococcus mutans was enhanced at Ag-ZrP additions of 0%wt, 0.5%wt, 1.0%wt, 1.5%wt, 2.0%wt, 2.5%wt, and 3.0%wt, achieving respective rates of 53.53%, 67.08%, 83.23%, 93.38%, 95.85%, and 98.00%. Similarly, the antibacterial rate against Escherichia coli registered at 31.62%, 50.14%, 64.00%, 75.09%, 86.30%, 92.98%. When Ag-ZrP was introduced at amounts ranging from 1.0% to 1.5%, PMMA materials exhibited peak mechanical properties. However, mechanical strength diminished beyond additions of 2.5%wt to 3.0%wt, relative to the 0%wt group, while PMMA demonstrated no notable cytotoxicity below a 3.0%wt dosage. Thus, it is inferred that optimal antimicrobial and mechanical properties of PMMA materials are achieved with nano-Ag-ZrP (RHA-1F-II) additions of 1.5%wt to 2.0%wt, without eliciting cytotoxicity.

Effect of treated zirconium dioxide nanoparticles on the flexural properties of autopolymerized resin for interim fixed restorations: An in vitro study

STATEMENT OF PROBLEM

Fractures of interim fixed restorations are a common complication. The autopolymerized polymethyl methacrylate resin materials used for interim fixed restorations have limited mechanical properties, but whether adding treated zirconium dioxide nanoparticles improves mechanical properties is unclear.

PURPOSE

The purpose of this in vitro study was to evaluate the effect of treated zirconium dioxide nanoparticles on the flexural strength and elastic modulus of autopolymerized polymethyl methacrylate resin.

MATERIAL AND METHODS

A split-metal mold (60×10×3.3 mm) was used to fabricate 40 autopolymerized acrylic resin specimens. The specimens were divided into 4 groups (n=10) according to zirconium dioxide nanoparticle concentration: control (unmodified resin) and zirconium dioxide nanoparticle contents of 1, 2.5, and 5 wt%. The specimens were mixed and polymerized according to the manufacturer's instructions and stored in distilled water for 48 ±2 hours at 37 °C. The flexural strength and elastic modulus were evaluated based on the 3-point bend test where data were analyzed by using 1-way analysis of variance and Tukey post hoc tests (α=.05).

RESULTS

The flexural strength of the 1-wt% zirconium dioxide nanoparticle specimens was significantly higher than that of the control group (P<.001) but did not significantly increase further with the higher nanoparticle content (P>.05). Elastic modulus significantly decreased with 2.5-wt% zirconium dioxide nanoparticles (P=.019), while no significant changes were found with other test groups (P>.05).

CONCLUSIONS

The addition of treated zirconium dioxide nanoparticles at low concentrations increased the flexural strength of autopolymerized polymethyl methacrylate resins used in fixed interim restorations.

Recycled PMMA prepared directly from crude MMA obtained from thermal depolymerization of mixed PMMA waste

Recycled PMMA was prepared by directly polymerizing crude pyrolysis oils from lab-scale pyrolysis of collected industrial waste PMMA. The pyrolysis oils consisted mainly of methyl methacrylate (MMA, >85%), while the type and number of by-products from the thermal process were assigned through GC-MS analysis showing a clear correlation to the pyrolysis temperature. By-products can be removed by distillation; however, directly employing the crude oils to prepare PMMA through solution, suspension, emulsion, or casting polymerization was investigated to assess the potential for omitting this costly step. It was found that the crude pyrolysis oils could be polymerized efficiently via solution, emulsion, and casting polymerization to produce a polymer similar to the PMMA prepared from a pristine monomer. The impurities in the PMMAs prepared from the crude mixtures were investigated by extraction analyses followed by screening by GC-MS. In the case of casting polymerization, the GC-MS analysis, as expected, revealed various residual by-products, while solution and emulsion polymerization showed only very few impurities, mainly originating from the polymerization and not the feed material. Additional purification of the crude pyrolysis oils would be required for applications in casting polymerization. In contrast, direct polymerization by emulsion or solution polymerization is considered applicable for producing pristine PMMA from crude waste PMMA pyrolysis oil.

Thermal insulation properties of lightweight, self-healing, and mesoporous carrageenan/PMMA cryogels

The development of new bio-based cryogel materials with low environmental impact and various properties such as self-healing, flame-retardancy, low thermal conductivity has emerged as a cutting-edge research topic in special-purpose materials and a significant challenge. Herein, we report a simple processing methodology for preparing new mesoporous light weight thermal insulation biomass hybrid cryogels based on natural and biocompatible polymers, including marine glycosaminoglycan carrageenan moss (CM) and polymethyl methacrylate (PMMA) abbreviated as CM/PMMA under cryo conditions. The mechanical, thermal, and physicochemical characterization of the obtained hybrid cryogel was studied. The effect of increasing thickness on thermal conductivity and compressive strength was investigated. The results show that the thermal conductivity increases from 0.068 W m-1 K-1 to 0.124 W m-1 K-1 with increasing thickness. Also, the compressive strength changed from 89.5% MPa to 95.4% MPa. The results revealed that cryogel has a wrinkled surface and interconnected pores and exhibits high flexibility, self-healing ability, flame retardancy, and low thermal conductivity.

From Solid-State Cluster Compounds to Functional PMMA-Based Composites with UV and NIR Blocking Properties, and Tuned Hues

New nanocomposite materials with UV-NIR blocking properties and hues ranging from green to brown were prepared by integrating inorganic tantalum octahedral cluster building blocks prepared via solid-state chemistry in a PMMA matrix. After the synthesis by the solid-state chemical reaction of the K₄[{Ta₆Brⁱ₁₂}Br^a₆] ternary halide, built-up from [{Ta₆Brⁱ₁₂}Br^a₆]^4- anionic building blocks, and potassium cations, the potassium cations were replaced by functional organic cations (Kat⁺) bearing a methacrylate function. The resulting intermediate, (Kat)₂[{Ta₆Brⁱ₁₂}Br^a₆], was then incorporated homogeneously by copolymerization with MMA into transparent PMMA matrices to form a brown transparent hybrid composite Ta@PMMA_brown. The color of the composites was tuned by controlling the charge and consequently the oxidation state of the cluster building block. Ta@PMMA_green was obtained through the two-electron reduction of the [{Ta₆Brⁱ₁₂}Br^a₆]^2- building blocks from Ta@PMMA_brown in solution. Indeed, the control of the oxidation state of the Ta₆ cluster inorganic building blocks occurred inside the copolymer, which not only allowed the tuning of the optical properties of the composite in the visible region but also allowed the tuning of its UV and NIR blocking properties.

Role of ZnO Nanoparticles Loading in Modifying the Morphological, Optical, and Thermal Properties of Immiscible Polymer (PMMA/PEG) Blends

High-performance hybrid polymer blends can be prepared by blending different types of polymers to improve their properties. However, most polymer blends exhibit phase separation after blending. In this study, polymethylmethacrylate/polyethylene glycol (PMMA/PEG) polymer blends (70/30 and 30/70 w/w) were prepared by solution casting with and without ZnO nanoparticles (NPs) loading. The effect of loading ZnO nanoparticles on blend morphology, UV blocking, glass transition, melting, and crystallization were investigated. Without loading ZnO NP, the PMMA/PEG blends showed phase separation, especially the PEG-rich blend. Loading PMMA/PEG blend with ZnO NPs increased the miscibility of the blend and most of the ZnO NPs dispersed in the PEG phase. The interaction of the ZnO NPs with the blend polymers slightly decreased the intensity of infrared absorption of the functional groups. The UV-blocking properties of the blends increased by 15% and 20%, and the band gap energy values were 4.1 eV and 3.8 eV for the blends loaded with ZnO NPs with a PMMA/PEG ratio of 70/30 and 30/70, respectively. In addition, the glass transition temperature (T_g) increased by 14 °C, the crystallinity rate increased by 15%, the melting (T_m) and crystallization(T_c) temperatures increased by 2 °C and 14 °C, respectively, and the thermal stability increased by 25 °C compared to the PMMA/PEG blends without ZnO NP loading.

Copper alumina @ poly (aniline-co-indole) nanocomposites: synthesis, characterization, electrical properties and gas sensing applications

Poly(aniline-co-indole)/copper alumina (PANI-co-PIN/Cu–Al₂O₃) with excellent AC conductivity, dielectric properties, and ammonia gas detecting capabilities were synthesised via in situ chemical oxidative polymerization. The presence of Cu–O bonding vibrations and shift of some characteristic peaks in the Fourier transform infrared spectroscopy (FT-IR) revealed the successful encapsulation of Cu–Al₂O₃ nanoparticles in the copolymer. The XRD studies showed the crystalline peaks of Cu–Al₂O₃ in the PANI-co-PIN nanocomposites. The high-resolution transmission electron microscopy (HR-TEM) images confirmed the reinforcement of the inorganic moiety in the copolymer. The results from thermogravimetric analysis (TGA) showed that the inclusion of Cu–Al₂O₃ in the copolymer matrix greatly increases the thermal stability of PANI-co-PIN. The alternate current (AC) conductivity and dielectric properties of nanocomposites were higher than pure PANI-co-PIN. The improved electrical properties of nanocomposites were due to strong contact between the copolymer and metal oxide surfaces. The gas sensing properties of synthesized copolymer nanocomposites showed excellent sensitivity and response towards ammonia gas at room temperature. The PANI-co-PIN/5 wt% Cu–Al₂O₃ nanocomposite has the best gas sensing characteristics. The higher AC conductivity, dielectric properties and gas sensing characteristics of PANI-co-PIN/Cu–Al₂O₃ might be used to develop electrochemical sensing devices.

PANI-co-PIN/Cu–Al₂O₃ nanocomposites synthesised via in situ polymerization showed excellent electrical and NH₃ gas sensing properties.

In Vitro Fracture Resistance of Endodontically Treated Premolar Teeth Restored with Prefabricated and Custom-Made Fibre-Reinforced Composite Posts

(1) Background: The study aimed to compare and analyse the differences between the features of prefabricated fibre-reinforced composite (FRC) posts and custom-made FRC posts in the form of a tape and confirm the necessity of using FRC posts in teeth treated endodontically in comparison to direct reconstruction with a composite material. (2) Methods: Sixty premolars after endodontic treatment were used. The teeth were divided into four groups (n-15). Group 1: teeth with embedded prefabricated posts (Mirafit White); group 2: teeth with embedded prefabricated posts (Rebilda); group 3 teeth with embedded custom-made posts in the form of a tape (EverStick); group 4: teeth without a post restored with composite material. The compressive strength of the teeth was tested using the Instron-5944 testing machine until the sample broke. The crystal structure of the investigated posts was detected with the X-ray diffractometer (3) Results: During the experiment, the maximum values of forces at which the damage of the restored premolar teeth after endodontic treatment occurred were obtained. The best results were obtained for teeth rebuilt with Rebilda Posts (1119 N), while teeth with cemented Mirafit White posts were the weakest (968 N). Teeth without an embedded FRC post, rebuilt only with light-cured composite material, obtained the lowest value-859 N. (4) Conclusions: The use of FRC posts increases the resistance to damage of an endodontically treated tooth when compared to direct restoration with light-cured composite material.

Synthesis of a hydroxyapatite/poly(methyl methacrylate) nanocomposite using dolomite

Hydroxyapatite/poly(methyl methacrylate) (HA-PMMA) nanocomposites are extensively used in biomedical fields. Therefore, the design and development of low-cost and industrially viable novel methods are essential to synthesize HA-PMMA nanoparticles. In this letter, we report such an economical, simple and industrially applicable novel method to synthesize nanosized HA-PMMA composite particles using extensively distributed dolomite.

Effects of alumina nanoparticles on the microstructure, strength and wear resistance of poly(methyl methacrylate)-based nanocomposites prepared by friction stir processing

In this study, alumina-reinforced poly(methyl methacrylate) nanocomposites (PMMA/Al₂O₃) containing up to 20vol% nanoparticles with an average diameter of 50nm were prepared by friction stir processing. The effects of nanoparticle volume fraction on the microstructural features and mechanical properties of PMMA were studied. It is shown that by using a frustum pin tool and employing an appropriate processing condition, i.e. a rotational speed of 1600rpm/min and transverse velocity of 120mm/min, defect free nanocomposites at microscale with fine distribution of the nanoparticles can successfully been prepared. Mechanical evaluations including tensile, flexural, hardness and impact tests indicate that the strength and toughness of the material gradually increases with the nanoparticle concentration and reach to a flexural strength of 129MPa, hardness of 101 Shore D, and impact energy 2kJ/m² for the nanocomposite containing 20vol% alumina. These values are about 10% and 20% better than untreated and FSP-treated PMMA (without alumina addition). Fractographic studies indicate typical brittle features with crack deflection around the nanoparticles. More interestingly, the sliding wear rate in a pin-on-disk configuration and the friction coefficient are reduced up to 50% by addition of alumina nanoparticles. The worn surfaces exhibit typical sliding and ploughing features.

Preparation of self-healing polyurethane/functionalized graphene nanocomposites as electro-conductive one part adhesives

We report the synthesis and investigation of the electrical conductivity and self-healing properties of moisture curable polyurethane (PU) adhesives filled with functionalized graphene nanosheets and isophorone diisocyanate (IPDI) loaded poly(methyl methacrylate) (PMMA) nanocapsules. For this purpose, chemically functionalized graphene was prepared by covalently grafting 4-(4,5-diphenyl-1H-imidazol-2-yl)phenol (DIP) on the surface of graphene oxide and synthesized PMMA nanocapsules were loaded with IPDI. Both nanofillers were then dispersed in a polyurethane matrix and the effects on the adhesion properties of the adhesives in aluminum–aluminum metal joints were studied. The results showed that by surface modification and better exfoliation of graphene nanosheets, the electrical conductivity was increased from 2.2 × 10⁻⁹ S m⁻¹ to 4.1 S m⁻¹ for pure PU and 10 wt% graphene based nanofiller loaded PU, respectively. The thermal stability, electrical conductivity, shear strength and self-healing process of the ECAs were also studied. The results provide evidence that the prepared adhesives have the potential for applications in electronic device packaging.

One part moisture curable adhesives based on polyurethane/functionalized graphene nanocomposites were synthesized and showed good electrical conductivity, thermal stability, shear strength and self-healing properties.

Organic-Inorganic Composite Films Based on Gd3Ga3Al2O12:Ce Scintillator Nanoparticles for X-ray Imaging Applications

Organic-inorganic nanocomposite self-standing films of Gd₃Ga₃Al₂O₁₂ (GGAG) uniformly dispersed in poly(methyl methacrylate) (PMMA) and polystyrene polymer are prepared for radiography application. GGAG:Ce nanoscintillator has been chosen because of its high light output and fast decay time. The nanopowder of GGAG is synthesized by coprecipitation method and dispersed in the polymer matrix by a simple blending technique. The nanocomposite films of thickness in the range of 150-450 μm with a very high inorganic content is achieved by this technique. These films are characterized by their uniformity, optical absorption, photoluminescence, and radioluminescence. These films are further tested for their application in radiography by recording X-ray images using a commercially available charge-coupled device camera. A resolution of 10 lp/mm is obtained using GGAG:PMMA composite film with 50% loading, confirming their application in imaging devices.

Highly Bendable In-Ga-ZnO Thin Film Transistors by Using a Thermally Stable Organic Dielectric Layer

Flexible In-Ga-ZnO (IGZO) thin film transistor (TFT) on a polyimide substrate is produced by employing a thermally stable SA7 organic material as the multi-functional barrier and dielectric layers. The IGZO channel layer was sputtered at Ar:O₂ gas flow rate of 100:1 sccm and the fabricated TFT exhibited excellent transistor performances with a mobility of 15.67 cm²/Vs, a threshold voltage of 6.4 V and an on/off current ratio of 4.5 × 10⁵. Further, high mechanical stability was achieved by the use of organic/inorganic stacking of dielectric and channel layers. Thus, the IGZO transistor endured unprecedented bending strain up to 3.33% at a bending radius of 1.5 mm with no significant degradation in transistor performances along with a superior reliability up to 1000 cycles.

The Effects of Cryomilling CNTs on the Thermal and Electrical Properties of CNT/PMMA Composites

In this study, the cryomilling of carbon nanotubes (CNTs) was carried out to accomplish better dispersion without using any hazardous chemicals. Accordingly, different samples of CNTs were prepared by varying the milling speed (10, 20, and 25 Hz) and time (5, 10, and 15 min) and incorporated into the poly(methyl methacrylate) (PMMA) matrix. The changes of the morphology were analyzed by utilizing a field emission scanning electron microscope (FESEM) and a high-resolution transmission electron microscope (TEM). Qualitative analysis of the cryomilled CNTs was carried out using Raman spectroscopy, and their surface area was determined via Brunauer–Emmett–Teller (BET) analysis. Subsequently, thermogravimetric analysis was conducted to evaluate the thermal properties, whereas the surface resistivity and electromagnetic interference shielding effectiveness for the electrical conductivity were also examined. It was observed that the composite with Cr-20-10 showed better thermal stability and lower resistivity in comparison to the others because, as the cryomilling time and frequency increased the distribution, dispersion and surface area also increased. Consequently, a better interaction between CNTs and PMMA took place.

Transparent 'solution' of ultrathin magnesium hydroxide nanocrystals for flexible and transparent nanocomposite films

Transparent solutions of nanocrystals exhibit many unique properties, and are thus attractive materials for numerous applications. However, the synthesis of transparent nanocrystal solutions of magnesium hydroxide (MH) with wide applications is yet to be realized. Here, we report a facile two-step process, which includes a direct reactive precipitation in alcohol phase instead of aqueous phase combined with a successive surface modification, to prepare transparent alcohol solutions containing lamellar MH nanocrystals with an average size of 52 nm and an ultrathin thickness of 1-2 nm, which is the thinnest MH nanoplatelet reported in the literatures. Further, highly flexible and transparent nanocomposite films are fabricated with a solution mixing method by adding the transparent MH nanocrystal solutions into PVB solution. Considering the simplicity of the fabrication process, high transparency and good flexibility, this MH/polymer nanocomposite film is promising for flame-resistant applications in plastic electronics and optical devices with high transparency, such as flexible displays, optical filters, and flexible solar cells.

Novel hybrid PVA–InZnO transparent thin films and sandwich capacitor structure by dip coating method: preparation and characterizations

In this paper, a very simple and cost effective dip coating method to obtain novel hybrid PVA–InZnO transparent thin films and sandwich capacitor structures for future transparent device applications.

Surface functionalization of zirconium phosphate nanoplatelets for the design of polymer fillers

Inorganic-organic hybrid materials were synthesized by covalent attachment of epoxides to the surface of zirconium phosphate (ZrP) nanoplatelets. X-ray powder diffraction, FTIR, and TGA were utilized to confirm the presence of the modifiers and exclusive functionalization of the ZrP surface. NMR experiments were conducted to confirm the formation of P-O-C bonds between surface phosphate groups and epoxide rings. The applicability of the organically modified products was demonstrated by their use as fillers in a polymer matrix. Subsequently, a two step intercalation and surface modification procedure was utilized to prepare polymer nanocomposites that were imparted with functionality through the encapsulation of molecules within the interlayer of surface modified ZrP.