Effects of Monomer Composition of Urethane Methacrylate Based Resins on the C=C Degree of Conversion, Residual Monomer Content and Mechanical Properties

(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.

Radiation Graft-Copolymerization of Ultrafine Fully Vulcanized Powdered Natural Rubber: Effects of Styrene and Acrylonitrile Contents on Thermal Stability

Graft copolymers, deproteinized natural rubber-graft-polystyrene (DPNR-g-PS) and deproteinized natural rubber-graft-polyacrylonitrile (DPNR-g-PAN), were prepared by the grafting of styrene (St) or acrylonitrile (AN) monomers onto DPNR latex via emulsion copolymerization. Then, ultrafine fully vulcanized powdered natural rubbers (UFPNRs) were produced by electron beam irradiation of the graft copolymers in the presence of di-trimethylolpropane tetra-acrylate (DTMPTA) as a crosslinking agent and, subsequently, a fast spray drying process. The effects of St or AN monomer contents and the radiation doses on the chemical structure, thermal stability, and physical properties of the graft copolymers and UFPNRs were investigated. The results showed that solvent resistance and grafting efficiency of DPNR-g-PS and DPNR-g-PAN were enhanced with increasing monomer content. SEM morphology of the UFPNRs showed separated and much less agglomerated particles with an average size about 6 μm. Therefore, it is possible that the developed UFPNRs grafted copolymers with good solvent resistance and rather high thermal stability can be used easily as toughening modifiers for polymers and their composites.

Effect of Silicon Nitride (Si3N4) on Mechanical and Dielectric Properties of Fused Silica Ceramic Composites

Fused silica ceramics composites were widely using for the fabrication of radomes which is the vital component of a missile. The required properties were attained by the addition of small amounts of Silicon Nitride (Si3N4) to the fused silica for enhancing flexural strength and without disturbing the dielectric properties. In the present work, porous fused silica ceramic composites were fabricated using gelcasting process, a near net shaping technique. The experiments were conducted using Response Surface Methodology (RSM) central composite with face centered design with six centre points approach. The process parameters of gelcasting process such as solid loading, monomer ratio, monomer content and additive (Si3N4) were considered as input parameters and flexural strength, porosity and dielectric constant as response parameters. Single parameter and interaction parameter effect on responses were studied. The effectiveness of derived models was compared with Analysis of Variance (ANOVA) at 95% confidence level. Statistical analysis proven that input parameters have critical effect on responses. The derived RSM mathematical models have a higher R2 values (Flexural strength 97.62%, Porosity 95.12% and dielectric constant 95.93%) which shows the critical relation between actual and predicted values. The optimal responses obtained were flexural strength 86.173 MPa, porosity 39.767% and dielectric constant 6.949 corresponding parameters process parameters solid loading 47.95%, additive (Si3N4) 10.43 wt%, monomer content 15 wt% and monomer ratio 3.

Influence of Fluorine-Containing Monomer Content on the Hydrophobic and Transparent Properties of Nanohybrid Silica Polyacrylate Coating Materials

Nanosilica-modified, fluorine-containing polyacrylate hybrid coating materials, consisting of dodecafluoroheptyl methacrylate (DFMA), methyl methacrylate (MMA), 2-ethyl hexyl acrylate (2-EHA), 3-(trimethoxysilyl) propyl methacrylate (KH-570), and tetraethylorthosilicate (TEOS), are synthesized successfully by free radical polymerization and the sol–gel process. It is revealed that the content of the fluorine-containing polyacrylate hybrid coating materials from DFMA monomers significantly improves the properties of the films. The polyacrylate coating film prepared with a weight ratio of DFMA/MMA at 1:5 exhibits the largest water contact angle of 105.4°, which demonstrates that DFMA can effectively improve the hydrophobicity of the coating film. Moreover, the silicon coupling agent (KH-570) is used to graft silica with acrylate. Spherical in shape, the surface morphology of the nanohybrid film exhibits a core–shell structure, which increases the surface roughness and enhances the hydrophobic properties. The as-prepared fluorine-containing nanohybrid silica polyacrylate film possesses a high transmittance of 89–97% in the visible light region, indicating its potential as a very attractive solution in many practical areas.

Development of a Promising Method for Producing Oligomeric Mixture of Branched Alkylene Guanidines to Improve Substance Quality and Evaluate Their Antiviral Activity against SARS-CoV-2

This paper reports the synthesis of branched alkylene guanidines using microfluidic technologies. We describe the preparation of guanidine derivatives at lower temperatures, and with significantly less time than that required in the previously applicable method. Furthermore, the use of microfluidics allows the attainment of high-purity products with a low residual monomer content, which can expand the range of applications of this class of compounds. For all the samples obtained, the molecular-weight characteristics are calculated, based on which the optimal condensation conditions are established. Additionally, in this work, the antiviral activity of the alkylene guanidine salt against the SARS-CoV-2 virus is confirmed.

Fast, inexpensive, and reliable HPLC method to determine monomer fractions in poly(3-hydroxybutyrate-co-3-hydroxyvalerate)

The determination of the monomer fractions in polyhydroxyalkanoates is of great importance for research on microbial-produced plastic material. The development of new process designs, the validation of mathematical models, and intelligent control strategies for production depend enormously on the correctness of the analyzed monomer fractions. Most of the available detection methods focus on the determination of the monomer fractions of the homopolymer poly(3-hydroxybutyrate). Only a few can analyze the monomer content in copolymers such as poly(3-hydroxybutyrate-co-3-hydroxyvalerate), which usually require expensive measuring devices, a high preparation time or the use of environmentally harmful halogenated solvents such as chloroform or dichloromethane. This work presents a fast, simple, and inexpensive method for the analysis of poly(3-hydroxybutyrate-co-3-hydroxyvalerate) with high-performance liquid chromatography. Samples from a bioreactor experiment for the production of poly(3-hydroxybutyrate-co-3-hydroxyvalerate) with Cupriavidus necator H16 were examined regarding their monomer content using the new method and gas chromatography analysis, one of the most frequently used methods in literature. The results from our new method were validated using gas chromatography measurements and show excellent agreement.Key points∙ The presented HPLC method is an inexpensive, fast and environmentally friendly alternative to existing methods for quantification of monomeric composition of PHBV.∙ Validation with state of the art GC measurement exhibits excellent agreement over a broad range of PHBV monomer fractions.

UV Polymerization of Methacrylates—Preparation and Properties of Novel Copolymers

More environmentally friendly polymeric materials for use in corrosive conditions were obtained in the process of UV polymerization of terpene methacrylate monomers: geranyl methacrylate and citronellyl methacrylate and the commercially available monomer methyl methacrylate. Selected properties (solvent resistance, chemical resistance, glass transition temperature, thermal stability, and decomposition course during heating) were evaluated. It was found that the properties of the materials directly depended on the monomer percentage and the conditioning temperatures used. An increase in the geranyl or citronellyl methacrylate monomer content in the copolymers reduced the solubility and chemical resistance of the materials post-cured at 50 °C. The samples post-cured at 120 °C were characterized by high resistance to polar and non-polar solvents and the chemical environment, regardless of the percentage composition. The glass transition temperatures for samples conditioned at 120 °C increased with increasing content of methyl methacrylate in the copolymers. The thermal stability of copolymers depended on the conditioning temperatures used. It was greater than 200 °C for most copolymers post-cured at 120 °C. The process of pyrolysis of copolymers led to the emission of geranyl methacrylate, citronellyl methacrylate, and methyl methacrylate monomers as the main pyrolysis volatiles.

Preparation and Characterization of Optically Active Polyurethane from Rotatory Binaphthol Monomer and Polyurethane Prepolymer

Optically active polymers are promising multifunctional materials with great application potentials. Herein, environmentally friendly optically active polyurethanes (OPUs) were obtained by introducing rotatory binaphthol monomer to polyurethane. The influence of binaphthol monomer content on the structure, mechanical properties, infrared emissivity, and thermal insulation of OPUs was studied intensively. Structure characterization indicated that the optically active polyurethanes have been successfully synthesized. The OPU synthesized with BIMOL and BDO at the mole ratio of 1:1 presented better thermal resistance. In addition, OPUs showed enhanced tensile strength and stretchability with the increase of BINOL content to a certain extent due to its rigid structural features and high molecular weight. The optically active polyurethanes showed lower infrared emissivity values (8–14 μm) than waterborne polyurethane (WPU), and the infrared emissivity decreased from 0.850 to 0.572 as the content of the BINOL monomer increased. Moreover, OPU4 exhibited the best heat insulation and cooling ability with about a 7 °C temperature difference. The thus-synthesized optically active polyurethanes provide an effective solution for developing highly effective thermal insulation materials.