The effects of cross-linking agents on the mechanical properties of poly (Methyl Methacrylate) resin

Abstract Cross-linking agents are incorporated into denture base materials to improve their mechanical properties. This study investigated the effects of various cross-linking agents, with different cross-linking chain lengths and flexibilities, on the flexural strength, impact strength, and surface hardness of polymethyl methacrylate (PMMA). The cross-linking agents used were ethylene glycol dimethacrylate (EGDMA), tetraethylene glycol dimethacrylate (TEGDMA), tetraethylene glycol diacrylate (TEGDA), and polyethylene glycol dimethacrylate (PEGDMA). These agents were added to the methyl methacrylate (MMA) monomer component in concentrations of 5%, 10%, 15%, and 20% by volume and 10% by molecular weight. A total of 630 specimens, comprising 21 groups, were fabricated. Flexural strength and elastic modulus were assessed using a 3-point bending test, impact strength was measured via the Charpy type test, and surface Vickers hardness was determined. Statistical analyses were performed using the Kolmogorov–Smirnov Test, Kruskal–Wallis Test, Mann–Whitney U Test, and ANOVA with post hoc Tamhane test (p ≤ 0.05). No significant increase in flexural strength, elastic modulus, or impact strength was observed in the cross-linking groups compared to conventional PMMA. However, surface hardness values notably decreased with the addition of 5% to 20% PEGDMA. The incorporation of cross-linking agents in concentrations ranging from 5% to 15% led to an improvement in the mechanical properties of PMMA

Modelling of Adsorption Kinetic Processes—Errors, Theory and Application

Adsorption has become a competitive method in the field of wastewater and air treatment. Adsorption kinetics is one of the main factors that must be understood before the applicability of any adsorbent. In every adsorption process, linear or non-linear analysis of the kinetics is applied. The goodness of fit index (coefficient of correlation or sum of squares) is applied to access the best model. The usage of linear or non-linear from of the adsorption kinetics has an impact on the distribution of error function. Almost in every adsorption study, linear forms have been used to conclude the best kinetic model that influence the adsorption mechanism—which might be an error. Therefore, this review highlights the mistakes in the usage of linear and non-linear models. The applicability of the adsorption kinetics in wastewater treatment is also illuminated

Abstracts from the 20th International Symposium on Signal Transduction at the Blood-Brain Barriers

https://deepblue.lib.umich.edu/bitstream/2027.42/138963/1/12987_2017_Article_71.pd

Preparation and characterization of an IPN type chelating resin containing amino and carboxyl groups for removal of Cu(II) from aqueous solutions

A novel IPN type chelating resin, amino-functionalized poly (glycidyl methacrylate)/poly (acrylic acid), (pGMA/pAA), was synthesized by a combination of serial reactions including, conventional radical polymerization, amination and photopolymerization. To assess the efficacy and characteristics of the resin in removal of Cu (II), batch adsorption experiments were carried out, and the effects of different parameters such as contact time, adsorbent dosage, initial metal ion concentration, temperature, and pH on the adsorption process were investigated. The results showed that 0.5 g/L dosage and pH 5 are the optimum values to achieve the maximum adsorption capacity and the adsorption kinetic of Cu (II) was well represented by pseudo-second-order kinetic model. In addition, it was found that the adsorption was mainly controlled by the film diffusion mechanism, along with a considerable contribution of the intra-particle diffusion mechanism, and Langmuir, Freundlich and Dubinin-Radushkevich (D-R) isotherm models can be used for interpreting the adsorption process. Moreover, FT-IR analysis results and the mean free energies of adsorption clearly indicate that the ion exchange and chelation mechanisms took place as dominating mechanisms simultaneously during the adsorption process. It was also found to be that IPN resin could be used at least four times without losing its original activity. (C) 2013 Elsevier Ltd. All rights reserved

Synthesis and swelling behavior of thermosensitive poly(N-isopropyl acrylamide-co-sodium-2-acrylamido-2-methyl propane sulfonate) and poly(N-isopropyl acrylamide-co-sodium-2-acrylamido-2-methyl propane sulfonate-co-glycidyl methacrylate) hydrogels

The crosslinked copolymers and terpolymers of N-isopropyl acrylamide (NIPAm) with sodium-2acrylamido-2-methyl propane sulfonate (NaAMPS) and glycidyl methacrylate (GMA) were prepared in the presence of N,N'-methylene bisacrylamide (NMBA) as crosslinker by free radical solution polymerization at 4 degrees C. Potassium persulfate (KPS) and potassium bisulfide (KBS) were used as initiator and accelerator, respectively. While molar percentages of NaAMPS in copolymers feed were varied as 1, 2, and 3; NaAMPS and GMA were used in the molar percentages of 1 : 1, 2: 2, and 3: 3, respectively, for the terpolymer preparation. NMBA contents were kept constant as 1 or 1.5 mol % of total monomer moles in feed composition. The effects of the comonomer type, feed composition, and the crosslinker contents on the lower critical solution temperatures (LCST), equilibrium swelling values (Q) of polymers, swelling kinetics in water at room temperature, and deswelling kinetics at 55 degrees C were investigated. The results indicated that the higher the NaAMPS content in NIPAm/NaAMPS copolymer, the higher the Q and water uptake rate, but less the water release rate. However, the presence of hydrophobic GMA comonomer in the terpolymer of NIPAm/NaAMPS/GMA decreased the Q values, it increased both the water uptake and the water release rates. It was also observed that NIPAm/NaAMPS and NIPAm/NaAMPS/GMA polymers exhibit continuous phase transition behavior between 40 and 50 degrees C. (c) 2006 Wiley Periodicals, Inc