Residual Monomer Content Research Articles

Vinyl methyl oxazolidinone and dimethyl itaconate as styrene substitutes for conventional high‐temperature unsaturated polyester resins

AbstractStyrene substitution is a major area of interest in the unsaturated polyester resins (UPR) industry and research. For most styrene‐free UPRs the unsaturated polyester (UP) formulation was tailored for less toxic reactive diluent monomers (RDM). The main challenge is finding a RDM that can directly substitute styrene in industrial UPR formulations without deterioration of resin and thermoset properties. Therefore, this study concerns vinyl methyl oxazolidinone (VMOX®) as a reactive diluent monomer for industrial high‐temperature UPRs. VMOX® and styrene were compared with dimethyl itaconate (DMI), methyl methacrylate, 2‐hydroxyethyl methacrylate, isobornyl methacrylate, triethylene glycol dimethacrylate and 1,4‐butanediol dimethacrylate. Further, the properties of produced resins and thermosets were investigated. The most striking result was comparable glass transition temperature, crosslink density, and residual monomer content of VMOX®‐ and styrene‐based thermosets. Subsequently, DMI was applied as a reactive co‐diluent for VMOX®‐based resins and thermosets. Significant improvement of VMOX® conversion during resin curing was observed. In conclusion, VMOX® is an excellent candidate for direct styrene substitution in industrial high‐temperature UPRs. Furthermore, the application of DMI as a reactive co‐diluent improves the reactivity of VMOX®‐based resins. The application of VMOX® and reactive co‐diluent monomer certainly creates new possibilities for direct styrene substitution in conventional UPR formulations.

The Influence of Contemporary Denture Base Fabrication Methods on Residual Monomer Content, Flexural Strength and Microhardness.

(1) Background: Digital technologies are available for denture base fabrication, but there is a lack of scientific data on the mechanical and chemical properties of the materials produced in this way. Therefore, the aim of this study was to investigate the residual monomer content, flexural strength and microhardness of denture base materials as well as correlations between investigated parameters. (2) Methods: Seven denture base materials were used: one conventional heat cured polymethyl methacrylate, one polyamide, three subtractive manufactured materials and two additive manufactured materials. High-performance liquid chromatography was used to determine residual monomer content and the test was carried out in accordance with the specification ISO No. 20795-1:2013. Flexural strength was also determined according to the specification ISO No. 20795-1:2013. The Vickers method was used to investigate microhardness. A one-way ANOVA with a Bonferroni post-hoc test was used for the statistical analysis. The Pearson correlation test was used for the correlation analysis. (3) Results: There was a statistically significant difference between the values of residual monomer content of the different denture base materials (p < 0.05). Anaxdent pink blank showed the highest value of 3.2% mass fraction, while Polident pink CAD-CAM showed the lowest value of 0.05% mass fraction. The difference between the flexural strength values of the different denture base materials was statistically significant (p < 0.05), with values ranging from 62.57 megapascals (MPa) to 103.33 MPa. The difference between the microhardness values for the different denture base materials was statistically significant (p < 0.05), and the values obtained ranged from 10.61 to 22.86 Vickers hardness number (VHN). A correlation was found between some results for the material properties investigated (p < 0.05). (4) Conclusions: The selection of contemporary digital denture base manufacturing techniques may affect residual monomer content, flexural strength and microhardness but is not the only criterion for achieving favourable properties.

Effect of Ethanol Addition on some Properties of Self-Polymerized Acrylic Resins

Background: Self-polymerized acrylic resins are widely utilized in dentistry. A higher residual monomer content is seen after polymerization of denture base resins. The literature showed that the ethanol solvent could rise the leaching of residual monomer from the polymer. The purpose of the current research was to investigate the influence of ethanol addition on hardness and roughness of acrylic resins. Materials and Methods: Sixty acrylic resin specimens were prepared and were divided into 2 main sets due to the kind of test used (surface hardness and surface roughness). There were three groups according to the ethanol concentrations. The first group was the control specimens with no ethanol, the second group was loaded with 10 ml of ethanol; and the third group was loaded with 15 ml of ethanol. The acrylic specimens were measured using the Shore A Durometer hardness and the surface roughness tester. Results: showed that the addition of ethanol significantly decrease the surface hardness of acrylic resins. The results indicated that there are significant differences between groups (P&lt; 0.0010). However, no significant differences between 10ml and 15 ml groups (P&gt;0.05). For surface roughness test, no significant differences were found among the studied groups (P&gt;0.05). Conclusions: The addition of ethanol to self-polymerized acrylic resins would significantly decrease the hardness and increases the surface roughness of acrylic resins

Effect of Ethanol Addition on some Properties of Self-Polymerized Acrylic Resins

Background: Self-polymerized acrylic resins are widely utilized in dentistry. A higher residual monomer content is seen after polymerization of denture base resins. The literature showed that the ethanol solvent could rise the leaching of residual monomer from the polymer. The purpose of the current research was to investigate the influence of ethanol addition on hardness and roughness of acrylic resins. Materials and Methods: Sixty acrylic resin specimens were prepared and were divided into 2 main sets due to the kind of test used (surface hardness and surface roughness). There were three groups according to the ethanol concentrations. The first group was the control specimens with no ethanol, the second group was loaded with 10 ml of ethanol; and the third group was loaded with 15 ml of ethanol. The acrylic specimens were measured using the Shore A Durometer hardness and the surface roughness tester. Results: showed that the addition of ethanol significantly decrease the surface hardness of acrylic resins. The results indicated that there are significant differences between groups (P&lt; 0.0010). However, no significant differences between 10ml and 15 ml groups (P&gt;0.05). For surface roughness test, no significant differences were found among the studied groups (P&gt;0.05). Conclusions: The addition of ethanol to self-polymerized acrylic resins would significantly decrease the hardness and increases the surface roughness of acrylic resins

Preparation and characterizations of antibacterial poly(methyl methacrylate) bone cement via copolymerization with a quaternary ammonium monomer of dimethylaminotriclosan methacrylate

Poly (methyl methacrylate) (PMMA) bone cement relies on the loaded antibiotic to realize the antibacterial purpose. But the exothermic behavior during setting often makes temperature-sensitive antibiotics inactivated. It is necessary to develop new material candidates to replace antibiotics. In this study, a new quaternary ammonium methacrylate (QAM) monomer called dimethylaminetriclosan methacrylate (DMATCM) was designed by the quaternization between 2-(Dimethylamino)ethyl methacrylate and triclosan, then employed as the modifier to explore the feasibility of equipping bone cement with antibacterial activity, and to investigate the variations on the physical and biological performances brought by the substitution ratio of DMATCM to MMA. Results showed that DMATCM opened its C=C bonding to participate in the MMA polymerization, and the quaternary ammonium group helped it to perform broad-spectrum antibacterial property against both Gram-positive Staphylococcus aureus and Gram-negative Escherichia coli. With an increased substitution ratio of DMATCM to MMA, the glass transition temperatures, the maximum exothermic temperatures, and the contact angles of bone cements declined, but the residual monomer contents, the fluid uptakes, and the setting times under Vical indentation increased. Long-term soaking made almost no changes to the weight loss and the mechanical properties of DMATCM-modified cements with lower substitution ratios of 0∼20%, and the activation rather enhanced the strengths of uncured AMBC-4 and AMBC-5 samples. Owing to more DMATCM exposed on the cement surface, the inhibition ring diameter produced by modified cement was improved to a maximum of 28.09 mm, and MC3T3-E1 cells performed the cell viabilities all beyond 70% and healthy adhesion after 72 h co-culturing. Taking all measured properties and ISO standards into account, the antibacterial bone cement under the ratio of 10% performed better, besides its good bactericidal effect, the other properties satisfied the requirements for clinical application.

Influence of postpolymerization time and atmosphere on the mechanical properties, degree of conversion, and cytotoxicity of denture bases produced by digital light processing

Statement of problemStudies on the effects of postprocessing conditions on the physical properties, degree of conversion (DC), and biocompatibility of denture bases produced by digital light processing are lacking. PurposeThe purpose of this in vitro study was to evaluate the effects of the atmosphere during postpolymerization and of postpolymerization time on the flexural strength, Vickers hardness, DC, cytotoxicity, and residual monomer content of denture bases. Material and methodsSix different groups of bar- and disk-shaped specimens from the denture base resin were produced, considering 2 different atmospheres (air and nitrogen) and 3 different postpolymerization times (5, 10, and 20 minutes). To determine the physical properties, the flexural strength and Vickers hardness were measured. Fourier transform infrared spectrometry was used to calculate DC. Cytotoxicity was assessed from the effect on human gingival fibroblasts. The residual monomer content was determined by using high-performance liquid chromatography. Based on the normality test by the Shapiro-Wilk method, a nonparametric factorial analysis of variances was conducted (α=.05). ResultsA significant interaction was detected between the atmosphere and postpolymerization time for hardness (P<.001) but no interaction for strength, DC, or cytotoxicity (P=.826, P=.786, and P=.563, respectively). Hardness was significantly affected by the postpolymerization time in the groups with the nitrogen atmosphere (P<.001). DC was significantly affected by the atmosphere (P=.012), whereas strength and cytotoxicity were not (P=.500 and P=.299, respectively). Cytotoxicity was significantly affected by the postpolymerization time (P<.001), but strength and DC were not (P=.482 and P=.167, respectively). Residual monomers were not detected after ≥10-minute postpolymerization time. ConclusionsThe atmosphere significantly affected hardness and DC, whereas the postpolymerization time significantly affected hardness, DC, cytotoxicity, and residual monomer content. Denture bases produced in a nitrogen atmosphere and with the 10-minute postpolymerization time showed sufficient hardness, DC, and no cytotoxicity.

Material extrusion of thermoplastic acrylic for intraoral devices: Technical feasibility and evaluation

With global demand for 3D printed medical devices on the rise, the search for safer, inexpensive, and sustainable methods is timely. Herein, we assessed the practicality of the material extrusion process for acrylic denture bases of which successful outcomes can be extended to implant surgical guides, orthodontic splints, impression trays, record bases and obturators for cleft palates or other maxillary defects. Representative materials comprising denture prototypes and test samples were designed and built with in-house polymethylmethacrylate filaments using varying print directions (PDs), layer heights (LHs) and reinforcements (RFs) with short glass fiber. The study undertook a comprehensive evaluation of the materials to determine their flexural, fracture, and thermal properties. Additional analyses for tensile and compressive properties, chemical composition, residual monomer, and surface roughness (Ra) were completed for parts with optimum parameters. Micrographic analysis of the acrylic composites revealed adequate fiber-matrix compatibility and predictably, their mechanical properties improved simultaneously with RFs and decreased LHs. Fiber reinforcement also improved the overall thermal conductivity of the materials. Ra, on the other hand, improved visibly with decreased RFs and LHs and the prototypes were effortlessly polished and characterized with veneering composites to mimic gingival tissues. In terms of chemical stability, the residual methyl methacrylate monomer contents are well below standards threshold for biological reactions. Notably, 5 vol% acrylic composites built with 0.05 mm LH in 0° on z-axis produced optimum properties that are superior to those of conventional acrylic, milled acrylic and 3D printed photopolymers. Finite element modeling successfully replicated the tensile properties of the prototypes. It may well be argued that the material extrusion process is cost-effective; however, the speed of manufacturing could be longer than that of established methods. Although the mean Ra is within an acceptable range, mandatory manual finishing and aesthetic pigmentation are required for long-term intraoral use. At a proof-of-concept level, it is evident that the material extrusion process can be applied to build inexpensive, safe, and robust thermoplastic acrylic devices. The broad outcomes of this novel study are equally worthy of academic reflection, and further translation to the clinic.

Low viscosity versus high viscosity PMMA bone cement for total joint arthroplasty: Influence of glass transition temperature, residual monomer content, transmittance of chemical functional groups, and crystallinity index on quasi-static flexural strength

The commercially available low viscosity (LV) PMMA bone cement has higher mechanical properties than high viscosity (HV) PMMA bone cement. However, the influence of glass transition temperature, residual monomer content, transmittance of chemical functional groups and crystallinity index on flexural strength is yet to be unveiled. The present study is aimed to investigate the influence of glass transition temperature, residual monomer content, transmittance of chemical functional groups and crystallinity index that contributed to the higher flexural strength of LV bone cement compared to HV bone cement. The thermal behavior analysis indicated higher glass transition temperature and residual content for LV bone cement (87.5 ± 1.80 °C and 15.56±0.62%, respectively) as compared to HV bone cement (81±2.64 °C and 13.69±0.38%, respectively). Moreover, the chemical parameters such as relatively low residual monomer content computed using Raman spectroscopy and low transmittance of chemical functional groups found in FTIR spectra for LV bone cement imply better flexural strength compared to that of HV bone cement. Results indicated the crystallinity index was higher for LV (42.78 ± 0.54%) bone cement than HV bone cement (36.41 ± 0.18%). The difference in flexural strength between LV and HV bone cements governed by glass transition temperature, crystallinity index, residual monomer content and transmittance of chemical functional groups assists in the improvement and applications of PMMA bone cement.

A novel treatment and derivatization for quantification of residual aromatic diisocyanates in polyamide resins

In the scientific context, the environmental and healthy impact of polymers is more related to the residual monomer content rather than their macromolecular structure, due to the monomer capability to interact with membrane cells. For this a novel method to stabilize and quantify residual monomeric isocyanates in high thermal resistance polyamide resins (PAs) has been developed. This new analytical method resulted in an improvement concerning the quantification of residual aromatic diisocyanates in viscous polymeric matrices by using a simple and cheap technique like HPLC-VWD. Diisocyanate monomers were derivatized with dibutylamine, resulting in stable urea derivatives that were simultaneously analysed and quantified. The method was applied to solvent-based polyamide resins, used as primary electrical insulation, for avoiding additional step of solvent removing before the analysis. The quantification of residual monomers answers to the provisions imposed by European Regulation N. 1907/2006 (REACH) for polymer registration, and the necessity of an early evaluation of the occupational risk associated with the use of diisocyanates, due to their toxicity and high reactivity towards moisture.

DYNAMICS OF INDICATORS OF MICROBIOCENOSIS OF THE ORAL CAVITY IN TREATMENT OF PATIENTS WITH COMPLETE REMOVABLE PLATE PROSTHESIS WITH THE USE OF OZONE THERAPY

Removable plate prostheses (RPP) belong to the stimuli of combined action and have a direct effect on the oral mucosa, lead to disruption of homeostasis, microbiocenosis of the oral cavity (OC) and various complications; their negative effect is exacerbated by violation of the polymerization regime and increased level of residual monomer (RM).&#x0D; Our experimental researches have shown that the use of ozone therapy with Ozone DTA provides antimicrobial effect at the level of 98.8-100%, it has a pronounced bactericidal effect against aerobic and facultative anaerobic microflora of the OP, which may be potential etiological factors of prosthetic stomatitis. Therefore, the aim of our work was to evaluate the impact of ozone therapy on the dynamics of the microbiocenosis of the oral cavity in the treatment of patients with complete removable plate prostheses in clinical settings.&#x0D; 118 patients were examined and underwent orthopedic treatment with complete RPP.&#x0D; There is a significant positive effect of the use of complete RPPs (made of plastic “Ftorax”) with control of the content of RM in their manufacture on the state of microbiocenosis of the mucous membrane of the prosthetic impression area of patients. Combination of these measures with ozone therapy is even more effective, from the standpoint of normalization of the microbiocenosis of the prosthetic impression area. The proposed therapeutic tactics have a preservative effect on the quantitative characteristics of the main resident participants of oral microbiocenoses – α-hemolytic streptococci, while reducing the proportion of stomatococci, epidermal staphylococci, veilonella and diphtheroids in the microbiocenoses of the prosthetic impression area. On the other hand, the combination of RM content control with ozone therapy provides effective elimination from the mucous membrane of the prosthetic impression area of microorganisms with high pathogenic potential.&#x0D; Observations of the composition of microbiocenoses of the mucous membrane of the prosthetic impression area of patients showed in the dynamics that the maximum changes are observed 1 month after orthopedic treatment, and they were slightly less severe after 6 months.&#x0D; Serious dysbiotic disorders were observed within 1-12 months in patients who used PPPs made of plastic “Ftorax” without control of the content of RM, which is apparently due to the effect of residual monomer on the mucous membrane of the prosthetic impression area. Patients of this group after the treatment with RPP undergo an adaptation period, when on the mucous membrane of the prosthetic impression area the population level of representatives of resident microflora is increased and at the same time the risk of colonization by microflora with high pathogenic potential increases.&#x0D; The use of the procedure of control over the content of RM in the process of making RPP from Ftorax plastic shortens the adaptation period, and 6 months after orthopedic treatment there is a steady trend to normalize the qualitative and quantitative composition of microbiocenoses of the mucous membrane of the prosthetic impression area.&#x0D; Additional application of the course of ozone therapy helps to eliminate the adverse effects of RPP (made of Ftorax plastic) on the microbiocenosis of the mucous membrane of the prosthetic impression area. This contributes to a significant reduction in the mass colonization of the mucous membrane of the prosthetic impression area by resident and transient representatives of the normal microflora, provides effective elimination of pathogens – β-hemolytic streptococci, Staphylococcus aureus, enterobacteria, and especially yeasts of the genus Candida.

Analysis of the residual monomer content in milled and 3D-printed removable CAD-CAM complete dentures: an in vitro study

ObjectiveThe study aimed to quantitatively evaluate the elution of methylmethacrylate from CAD-CAM manufactured removable complete dentures (RCDs) using high performance liquid chromatography (HPLC). MethodsThirty-two RCDs were manufactured following either the CNC-milling (Milled: n=8) or the 3D-printing (n=24) protocols. The 3D-printed dentures were further categorized into three groups based on their post-production rinsing cycles [Extended wash cycle (EWC), Standard wash cycle (SWC), and SWC with an additional Durécon coating (SWC2)]. HPLC was used to evaluate the methylmethacrylate concentrations (MMCs) eluted from the dentures in each group for different time periods (1, 2, 4, 8, and 24 hours). Mean and standard deviations were calculated for the MMCs; data was verified for normal distribution, ANOVA and post hoc tests were applied for statistical analyses (⍺=0.05). ResultsThe HPLC revealed that all the denture groups recorded some amounts of MMCs, with significant differences [F (3, 31) = 23.646, p<0.0001]. The milled denture group had the highest MMCs at 24 hours when compared to the EWC (p<0.0001), SWC (p=0.001), and SWC2 (p<0.0001) denture groups. SWC had a higher MMC than EWC (p=0.032) and SWC2 (p=0.015). No differences were found in MMCs when comparing EWC and SWC2 (p=0.989). ConclusionMethylmethacrylate concentrations were significantly lower in 3D-printed RCDs than in milled RCDs when using the resins employed in this study. Furthermore, the MMCs can be further decreased in 3D-printed RCDs when coated with an additional thin protective layer (Durécon) by following the manufacturer-recommended rinsing protocol or when an extended isopropanol wash cycle is adopted.

Water-Soluble Starch-Based Copolymers Synthesized by Electron Beam Irradiation: Physicochemical and Functional Characterization.

Modification of natural polymers for applications in the treatment of waste and surface waters is a continuous concern of researchers and technologists in close relation to the advantages they provide as related to classical polymeric flocculants. In this work, copolymers of starch-graft-polyacrylamide (St-g-PAM) were synthesized by electron beam irradiation used as the free radical initiator by applying different irradiation doses and dose rates. St-g-PAM loaded with ex situ prepared silver nanoparticles was also synthesized by using an accelerated electron beam. The graft copolymers were characterized by chemical analysis, rheology, and differential scanning calorimetry (DSC). The results showed that the level of grafting (monomer conversion coefficient and residual monomer concentration), intrinsic viscosity and thermal behavior (thermodynamic parameters) were influenced by the irradiation dose, dose rate and presence of silver nanoparticles. The flocculation performances of the synthesized copolymers were also tested on water from the meat industry in experiments at the laboratory level. In the coagulation–flocculation process, the copolymer aqueous solutions showed good efficiency to improve different water quality indicators.

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.

Durability indicatives of hydrogel for agricultural and forestry use in saline conditions

This research tested the hypothesis that the interaction between time and salinity reduces the water absorption potential of a hydrogel – Poly (Acrylamide-co-Potassium Acrylate) and influence the degradation of residual acrylamide monomer. The experimental design was completely randomized split-plot with four replications. The treatments were time periods (30, 60, 90 and 120 days) and levels of salinity of the hydrating solution (distilled water = 0.003, 0.5; 1.5; 3.0 and 6.0 dS m−1). Swelling, hydrogel composition, and residual acrylamide monomer concentration were evaluated. The hydrogel showed lowest water absorption potential (8.1 g g−1) in a saline solution of 4.20 dS m−1 after 120 days. The C/N ratio of the hydrogel increased by up to 47% in a hydrating solution with an EC of 4.4 dS m−1 at 120 days. Additionally, there was an observed shift in the wavelength of methylene, amide, and acrylate bands, that indicates degradation. Residual acrylamide monomer concentration was <0.5 mg g−1 (safe for agricultural use). After 120 days up to 85% of the residual acrylamide monomer was degraded. About the water absorption potential, the results suggest that under semi-arid conditions hydrogel durability for forestry and crops applications may be impaired by the salinity of the hydrating solution.

Multi-reactive mesogen system for polymer-stabilised vertical alignment liquid crystal displays

ABSTRACT This study investigates a new binary reactive mesogen system, consisting of a photoinitiator and a UV-B reactive mesogen (RM), for polymer-stabilised vertical alignment (PS-VA) and compares it to an industry standard RM. Analysis of the achieved PS-VA by relevant parameters, such as tilt generation, showed that the new material combination shows the same high level of performance as the industry standard. Additionally, the new materials were tested on their reliability parameters such as voltage holding ratio and residual monomer content and completely fulfiled the high industry requirements. The advantages of this novel binary system lie in the fact that it adds an additional degree of freedom allowing for the system to be better adapted to new liquid crystal hosts and the design of the UV-B RM. It is designed to be inactive under irradiation conditions in production and in the finished display product, unless the photoinitiator is present. This opens up the possibility for a significant decrease in production time by making the need for complete removal of residual monomer during production obsolete.

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.

Study of properties of acrylic, epoxy and epoxy acrylic compositions structured by the methods of convection heating and heating in the field of high-frequency current

This work is devoted to the development and study of the processes of accelerated structuring of polymer composite materials in the field of high-frequency current (microwave field) which are used in the electronic and instrument-making industries, etc. The complex of properties and the features of structuring of epoxy, acrylic and epoxy acrylic polymer composite materials in the microwave field are investigated. In comparison with the traditional method of structuring and polymerization (convection heating), the structuring in the microwave field equally affects the properties of the studied polymer composite materials, regardless of the chemical nature of the oligomer. The action of the microwave field for all studied polymer composite materials causes an increase in the degree of conversion of binders and a decrease in the content of residual monomer (methyl methacrylate) in thermoplastic acrylic polymer composite materials. In addition, the microwave treatment provides the completeness of chemical and physicochemical processes of the formation of rational structure of polymer composite materials with stable properties. The conducted research allows recommending various regimes of the structuring of the studied polymer composite materials taking into account operating conditions. These regimes ensure the reduction of structuring duration and provide a high level of mechanical and operational properties.

Determination of the residual monomer concentration of ε‐caprolactam in polyamide‐6 using thermogravimetric analysis coupled with Fourier transform infrared spectroscopy gas analysis

AbstractFor the anionic polymerization of ε‐caprolactam to polyamide‐6 the residual monomer concentration in the final polymer is an important characteristic. To determine this residual ε‐caprolactam monomer concentration, a fast and fail‐safe method was developed, which couples thermogravimetric analysis (TGA) with Fourier transform infrared spectroscopy (FTIR) gas analysis. FTIR allows an identification of the types of gasses released during heat treatment. Calibration of the infrared absorbance of ε‐caprolactam and the corresponding mass loss in TGA allows a quantitative evaluation of the ε‐caprolactam monomer release. Low‐heating rates and powdery samples guarantee high‐precision measurements.

A GAS CHROMATOGRAPHY STUDY ON THE EFFECT OF TWO DIFFERENT CURING CYCLES ON THE RESIDUAL MONOMER CONTENT OF TWO DIFFERENT HEAT CURE DENTURE BASE RESINS.

The conversion of monomer to polymer is not complete in denture base resins and residual monomer left can cause mucosal irritation, inflammation, and allergic reactions in tissues adjacent to dentures. The mechanical properties of denture base resins have been found to be lacking with increased residual monomer content. Therefore, it is desirable to reduce the residual monomer content in the processed denture. In the present study Gas chromatography method was used to determine the levels of residual methyl methacrylate monomer of two different brands of heat cure denture base resins processed by two different polymerization cycles. The study concluded that while processing the denture sufficient length of boiling phase should be given and for each brand, manufacturer’s instructions should be strictly followed while selecting polymerization cycle.

The effect of titanium dioxide on the moisture absorption of polyamide 6 prepared by T-RTM

In recent years, the replacement of metal components with composites is becoming more and more common in the automotive industry. Thermoplastic composites are recyclable, which meets requirements. Impregnating the reinforcing material is difficult but caprolactam is a good choice because in melt state, it has similar viscosity to that of water. Polyamide 6 can be produced from caprolactam by ring opening in-situ polymerisation. We produced PA 6 samples from caprolactam using T-RTM. We examined the effects of the manufacturing parameters on morphology on residual monomer content and crystalline proportion. Then we filled the samples with TiO2 and examined the same parameters. Finally, we tested the effects of crystallinity, residual monomer content and the filler on moisture absorption.