Glass Transition Temperature Of Polymethyl Methacrylate Research Articles

Effect of Polyvinylpyrrolidone Content on Pure Titanium Injection Molding

In water-soluble binder systems, polyethylene glycol (PEG) and polymethylmethacrylate (PMMA) are often used as primary and secondary components. The PEG/PMMA binder system is clean and environmentally friendly, but the discrepancy between the crystallization temperature of PEG and the glass transition temperature of PMMA leads to the generation of pores in the feedstock. The solidification pores have an adverse impact on the final mechanical properties of the samples. Polyvinylpyrrolidone (PVP), as a crystallization inhibitor, can inhibit the formation of porosity. In this study, spherical titanium powder with a diameter of less than 45 μm was used as metal powder; the binder system consisted of PEG, PMMA and SA. Different increments of PVP (0, 10%, 20%, 30 wt.%) were added to the PEG/PMMA binder system. The uniformity of the feedstock and the open channels generated after debinding were observed using SEM. The pores’ condition before and after debinding was studied using Micro CT, and the mechanical properties of the samples were also detected. By comparing the macroscopic and microscopic morphologies of the injected samples and mechanical properties of the sintered samples, it was found that a PVP content of 20 wt.% resulted in the best properties.

Enhancing Polymethyl Methacrylate Prostheses for Cranioplasty with Ti mesh Inlays.

Biocompatible polymers such as polymethyl methacrylate (PMMA), despite fulfilling biomedical aspects, lack the mechanical strength needed for hard-tissue implant applications. This gap can be closed by using composites with metallic reinforcements, as their adaptable mechanical properties can overcome this problem. Keeping this in mind, novel Ti-mesh-reinforced PMMA composites were developed. The influence of the orientation and volume fraction of the mesh on the mechanical properties of the composites was investigated. The composites were prepared by adding Ti meshes between PMMA layers, cured by hot-pressing above the glass transition temperature of PMMA, where the interdiffusion of PMMA through the spaces in the Ti mesh provided sufficient mechanical clamping and adhesion between the layers. The increase in the volume fraction of Ti led to a tremendous improvement in the mechanical properties of the composites. A significant anisotropic behaviour was analysed depending on the direction of the mesh. Furthermore, the shaping possibilities of these composites were investigated via four-point bending tests. High shaping possibility was found for these composites when they were shaped at elevated temperature. These promising results show the potential of these materials to be used for patient-specific implant applications.

Novel preparation method, catalytic performance and reaction mechanisms of PrxMn1−xOδ/3DOM ZSM-5 catalysts for the simultaneous removal of soot and NOx

Three dimensionally-ordered macroporous (3DOM) ZSM-5 zeolite catalysts with hierarchical pore structures have obvious advantages for the catalytic reaction systems containing reactants with different sizes. However, due to the stringent preparation conditions and confined crystallization space, the successful preparation of 3DOM ZSM-5 remains challenging. Herein, we report a novel method for the preparation of 3DOM ZSM-5 zeolite, termed the steam seed-assisted colloid crystal template (SSAC) method. The SSAC method avoids the growth of ZSM-5 crystals based on the confinement effect of the interstices of the polymethylmethacrylate (PMMA) template. The crystallization temperature of ZSM-5 is lower than the glass transition temperature of PMMA, which facilitates the formation of the 3DOM structure. Using 3DOM ZSM-5 as a support, a series of PrxMn1-xOδ/3DOM ZSM-5 catalysts were prepared via incipient wetness impregnation. These catalysts exhibited good catalytic performance for the simultaneous removal of soot and NOx, which can be attributed to the unique hierarchical pore structure, excellent redox properties, the sufficient active oxygen species and appropriate acid sites of overall catalysts. Among the synthesized catalysts, Pr0.2Mn0.8Oδ/3DOM ZSM-5 achieved the highest catalytic activity with a low soot combustion temperature of 417 °C and a wide temperature window of 128 °C-288 °C at 90% NO conversion. Finally, we proposed reaction mechanisms for the catalysts under different temperatures based on the in situ characterization results, kinetic measurements and DFT calculations.

A visco-elastoplastic constitutive model of aircraft polymethylmethacrylate related to strain rate and temperature

The visco-elastoplastic mechanical behavior related to the applied strain rate and temperature around the glass transition temperature of Polymethylmethacrylate (PMMA) has been systematically investigated. The uniaxial tensile test was performed at strain rate and temperature rangs 1.0 × 10−4–1.0 × 10−2 s−1 and 363–393 K, respectively, and the Dynamic Mechanical Analysis (DMA) test was carried out between 363 K and 413 K at various frequencies. Moreover, the robust complex constitutive model considering the temperature and strain rate effect is proposed. A nonlinear viscoelastic model is established to describe the viscoelastic response on the basis of the Zhu-Wang-Tang (ZWT) model and the time temperature equivalence principle, including the dependence of strain rate and temperature. Considering the yield stress, the cooperative model is adopted. The viscoplastic mechanical response is manifested as the competition performance of the softening deformation and hardening behavior. The predicted mechanical responses maintain good consistency with the experimental results, indicating that the visco-elastoplastic constitutive model proposed can accurately predict the mechanical behavior of PMMA materials within the imposed strain rate and near the glass transition temperature range.

Miscible polymethyl methacrylate/polylactide blend with enhanced foaming behavior and foam mechanical properties

High-performance foams play significant roles in many industries. Microcellular foaming with carbon dioxide as blowing agents is an advanced and environmentally friendly technology to prepare polymeric foams with significantly refined cellular morphology. The manipulation of polymer microstructure and rheological behavior is the key to tailor its foaming behavior. In this study, polymethyl methacrylate (PMMA) was blended with polylactide (PLA) to improve its foaming behavior in one-step batch foaming with carbon dioxide as blowing agents. It was demonstrated that PMMA and PLA are fully miscible in molecular level. The presence of PLA can lead to decreased glass transition temperature of PMMA, and PMMA can suppress the crystallization of PLA. PLA can enhance the melt elasticity of PMMA at low shear oscillation frequencies but decrease the melt elasticity of PMMA at high shear oscillation frequencies. Thanks to the plasticity effect and heterogeneous nucleation effect of PLA, adding an appropriate amount of PLA can significantly broaden the foaming window of PMMA and refine cellular morphology. Microcellular PMMA/PLA foams with cell sizes less than 10 µm and expansion ratio up to 18.4 were fabricated under a foaming pressure of 17.24 MPa with 10 wt% PLA. Nanocellular PMMA/PLA foam can be achieved with the presence of 25 wt% PLA under a foaming pressure of only 6.90 MPa. The PMMA/PLA blend foams show significantly enhanced compression modulus and strength compared with neat PMMA foams. Moreover, reducing cell sizes can significantly enhance the compression modulus and strength of foams.

A laboratory study of hydraulic fracturing at the brittle-ductile transition

Developing high-enthalpy geothermal systems requires a sufficiently permeable formation to extract energy through fluid circulation. Injection experiments above water’s critical point have shown that fluid flow can generate a network of highly conductive tensile cracks. However, what remains unclear is the role played by fluid and solid rheology on the formation of a dense crack network. The decrease of fluid viscosity with temperature and the thermally activated visco-plasticity in rock are expected to change the deformation mechanisms and could prevent the formation of fractures. To isolate the solid rheological effects from the fluid ones and the associated poromechanics, we devise a hydro-fracture experimental program in a non-porous material, polymethyl methacrylate (PMMA). In the brittle regime, we observe rotating cracks and complex fracture patterns if a non-uniform stress distribution is introduced in the samples. We observe an increase of ductility with temperature, hampering the propagation of hydraulic fractures close to the glass transition temperature of PMMA, which acts as a limit for brittle fracture propagation. Above the glass transition temperature, acoustic emission energy drops of several orders of magnitude. Our findings provide a helpful guidance for future studies of hydro-fracturing of supercritical geothermal systems.

Enhanced thermally conductive and thermomechanical properties of polymethyl methacrylate (PMMA)/graphene nanoplatelets (GNPs) nanocomposites for radiator of electronic components

In this work, multi-layer hot pressing (MLHP) method was used to prepare the graphene nanoplatelets (GNPs) filled polymethyl methacrylate (PMMA) composites. Effect of GNP content on the viscoelastic behavior and thermomechanical properties of composites was studied via rheometer, scanning electron microscope (SEM), infrared thermal imaging (ITI) and dynamic mechanical thermal analysis (DMTA), etc. According to dynamical rheological testing, thermorheological complexity was clearly displayed at elevated GNP content, based upon flow activation energy (Ea) and time-temperature superposition (TTS) principle. The infrared thermal imaging (ITI) indicated that a filler conductive network was gradually formed with increasing filler content. The average heating rate of the samples increased from 0.74 to 0.92 °C/s. The Agari model was found to fairly interpret the variation of thermal conductivity as a function of GNP loading, which agreed well with SEM observation and indicative of the formation of a GNP network structure. Dynamic thermomechanical properties of the composites were heavily influenced by the temperature distributions within the samples. The addition of GNP increased the glass transition temperature of PMMA from 116.7 to 125.9 °C, which favored enhanced thermophysical properties of PMMA. The prepared composites in this work showed wonderful mechanical properties even at relatively high temperatures (e.g., having storage modulus of 1.3–1.9 GPa and yielding strength more than 58.0 MPa at 50 °C). The current work is practically significant for further expanding the application range of PMMA/GNP nanocomposites.

Enhancing the dielectric properties of polymethyl methacrylate by using low loading graphene encapsulated styrene-butyl acrylate copolymer microspheres

With the rapid development of the electronics industry and electronic products, polymer nanocomposites with high dielectric constant and low dielectric loss will have great potential in various applications. In this work, a novel structure was obtained by absorbing reduced graphene oxide on the surfaces of styrene butyl-acrylate copolymer (rGO@SBA) microsphres through soap-free emulsion polymerization technique. Fourier-transform infrared spectrum characterization revealed the successful fabrication of rGO@SBA microspheres. SEM and TEM results indicated that rGO nanosheets were successfully loaded on the surface of SBA microspheres and the average diameter of rGO@SBA was increased to 650 nm. High dielectric permittivity rGO@SBA composites were obtained when the rGO loading was approximated to 2 wt%. The dielectric permittivity of rGO@SBA composites with 2 wt% rGO was 339 times higher than that of neat SBA. Furthermore, the electrical conductivity was also obviously enhanced. However, the dielectric loss of rGO@SBA composites was also inevitably increased. The rGO@SBA microspheres were further melt blended with polymethyl methacrylate (PMMA) matrix to obtain rGO@SBA/PMMA composites. The glass transition temperature of PMMA was increased with the content of rGO. The dielectric permittivity of rGO@SBA/PMMA composite with only 0.14 wt% rGO was increased to 15.5 at 1 kHz. On the other hand, the dielectric loss was controlled in a low level. SEM observation implied a segregated dispersion of rGO@SBA was realized in PMMA matrix. Our strategy provides a facile method to prepare high dielectric constant and low dielectric loss of rGO filled polymer composites through the fabrication of rGO encapsulated polymer microspheres.

The effect of acrylamide incorporation on the thermal and physical properties of denture resins

PURPOSEPolymethyl methacrylate (PMMA) is the most commonly used denture base material despite typically low in strength. The purpose of this study was to improve the physical properties of the PMMA based denture base resins (QC-20, Dentsply Ltd., Addlestone, UK; Stellon, AD International Ltd, Dentsply, Switzerland; Acron MC; GC Lab Technologies Inc., Alsip, Japan) by copolymerization mechanism.MATERIALS AND METHODSControl group specimens were prepared according to the manufacturer recommendations. In the copolymer groups; resins were prepared with 5%, 10%, 15% and 20% acrylamide (AAm) (Merck, Hohenbrunn, Germany) content according to the moleculer weight ratio, respectively. Chemical structure was characterized by a Bruker Vertex-70 Fourier transform infrared spectroscopy (FTIR) (Bruker Optics Inc., Ettlingen, Germany). Hardness was determined using an universal hardness tester (Struers Duramin, Struers A/S, Ballerup, Denmark) equipped with a Vickers diamond penetrator. The glass transition temperature (Tg) of control and copolymers were evaluated by Perkin Elmer Diamond DSC (Perkin Elmer, Massachusetts,USA). Statistical analyses were carried out using the statistical package SPSS for Windows, version 15.0 (SPSS, Chicago, IL, USA). The results were tested regarding the normality of distribution with the Shapiro Wilk test. Data were analyzed using ANOVA with post-hoc Tukey test (P<.01).RESULTSThe copolymer synthesis was confirmed by FTIR spectroscopy. Glass transition temperature of the copolymer groups were higher than the control groups of the resins. The 10%, 15% and 20% copolymer groups of Stellon presented significantly higher than the control group in terms of hardness. 15% and 20% copolymer groups of Acron MC showed significantly higher hardness values when compared to the control group of the resin. Acrylamide addition did not affect the hardness of the QC-20 resin significantly.CONCLUSIONWithin the limitation of this study, it can be concluded that copolymerization of PMMA with AAm increased the hardness value and glass transition temperature of PMMA denture base resins.

Mechanical and Thermal Properties of Polymethyl Methacrylate‐BN Nanotube Composites

Polymethyl methacrylate (PMMA)‐BN nanotube (BNNT) composites were fabricated and their mechanical and thermal properties were analyzed. Using a 1 wt.% BNNTs fraction in a polymer, the elastic modulus of PMMA was increased up to 19%. In addition, thermal stability and glass transition temperature of PMMA were also positively affected. The thermal conductivity of PMMA with BNNT additions increased three times. The resultant BNNT‐PMMA composites possess the high electrical breakover voltages. Thus our studies clearly indicate that BNNTs are promising nanofillers for improvement of mechanical and thermal conductivity of dielectric polymers under preservation of their electrical insulation.

Influence of Nanoparticles on Glass Transition of Polymers

Tunability of glass transition temperature of poly-methylmethacrylate has been achieved using homogeneously dispersed gold nanoparticles of different weight fraction within the polymer matrix. Remarkably, depression in glass transition temperature with respect to the neat polymer was observed for poly-methylmethacrylate (120 K and 15 K) by varying the weight fraction of the gold nanoparticles contrary to the conventional results in literature which shows elevation in Tg for attractive polymer-particle interaction, as is the case here. The magnitude of the shift in glass transition temperature is large for the higher of the two molecular weight of poly-methylmethacrylate studied here. Possible explanations of the observed behavior are provided, although more experiments are underway to unravel the intricacies of the observed phenomena.

Synthesis of arsenic containing polymethylmethacrylate using p-acetyl benzylidene triphenyl arsonium ylide as photoinitiator

Arsenic containing syndiotactic polymethylmethacrylate (PMMA) using p-ABTAY (p-acetyl benzylidene triphenyl arsonium ylide)in benzene as the photoinitiator at 30 ± 0.2°C has been synthesized. The system follows non-ideal kinetics ( R p ∝ [ I] 0.25 [M]) due to both primary radical termination and degradative chain transfer reaction. The glass transition temperature of PMMA is 145°C. Analysis of the polymer by SEM technique shows the presence of arsenic in it. The polymer has been characterized by Infra-red spectroscopy.

A Direct Molding Technique to Fabricate Silica Micro-Optical Components

AbstractA technology for the direct molding and release of silica micro-optical components in polymethyl methacrylate (PMMA) molds is developed. The objectives of this work are to bypass some of the usual steps in deep x-ray lithography (DXRL) and to determine the suitability of GR650 resin (methylpolysilsequioxane) for molding thick, high aspect ratio structures. The process is initiated by DXRL exposure of PMMA, followed by spin-on glass application, a cure at 85°C to set the shape of the resin, followed by demolding. The cure is below the glass transition temperature of PMMA and the demolding process allows re-use of the mold. There is no need for electroforming in the replication process. PMMA molds with thickness of 250, 350 and 500 um were fabricated by DXRL and standard resist development. A novel metal sacrificial layer technique is used in the release process with initial yield of about 50%. Microoptical elements that were fabricated include lenses, prisms, grating structures and transmission test structures. These components are cured above 400°C after release, to convert the organosilicon polymer to a silica-like material. Weight loss from the high temperature cure was in the range of 15 to 25%, while linear dimensions of the components decreased by about 1%. Composition of the molded, cured structures was measured by XPS depth profiles.

Direct bonding of organic polymeric materials

Direct bonding of organic polymeric materials can be realized when their surfaces are prepared in such a way that they are clean, smooth and susceptible to direct-bonding. In the surface-preparation process, tribo-chemical polishing is an essential step. Polymeric materials such as polymethylmethacrylate (PMMA), polyarylate, polyimide and polycarbonate were bonded either to themselves, to another polymer or to an inorganic material such as silicon or fused silica. The surfacial bond energy of the room temperature bond is surprisingly high: 0.1–0.2 J/m 2. Heating strengthens the direct bond; for example, for a bonded PMMA/PMMA wafer pair annealed at the glass-transition temperature of PMMA (105°C), the surfacial bond strength increases to 7.8 J/m 2. This indicates that the bonded surfaces are fused and are interlinked by chemical bonds. When polymers are bonded to low-thermal-expansion materials such as Si and fused silica, during annealing treatments, thermal stresses can induce fracturing of the inorganic part of the bonded wafer pair. By limiting the maximum annealing temperature or the size of the bonded area, fracturing can be avoided.

Direct bonding of organic materials

Direct bonding of polymethylmethacrylate (PMMA) is described as an example of the applicability of direct bonding to organic materials such as polymers. Direct bonding of a PMMA wafer to itself and to silicon and fused silica wafers is realized. At room temperature, the value of the bond energy indicates the presence of weak chemical interactions at the bonded interface. Heating a bonded PMMA/PMMA wafer pair to the glass transition temperature of PMMA (105 °C) and higher temperatures causes the two surfaces to fuse and the interface to become bridged by polymer chains.

X-radiation-induced changes in thermal expansion and glass transition temperature of polymethylmethacrylate

Journal of Polymer Science Part C: Polymer LettersVolume 27, Issue 8 p. 259-261 Article X-radiation-induced changes in thermal expansion and glass transition temperature of polymethylmethacrylate P. Mallikarjuna Reddy, P. Mallikarjuna Reddy Department of Physics, Sri Krishnadevaraya University, Anantapur 515 003 AP, IndiaSearch for more papers by this authorN. Manohara Murthy, N. Manohara Murthy Department of Physics, Sri Krishnadevaraya University, Anantapur 515 003 AP, IndiaSearch for more papers by this authorK. Mohana Raju, K. Mohana Raju Department of Polymer Science, Sri Krishnadevaraya University, Anantapur 515 003 AP, IndiaSearch for more papers by this author P. Mallikarjuna Reddy, P. Mallikarjuna Reddy Department of Physics, Sri Krishnadevaraya University, Anantapur 515 003 AP, IndiaSearch for more papers by this authorN. Manohara Murthy, N. Manohara Murthy Department of Physics, Sri Krishnadevaraya University, Anantapur 515 003 AP, IndiaSearch for more papers by this authorK. Mohana Raju, K. Mohana Raju Department of Polymer Science, Sri Krishnadevaraya University, Anantapur 515 003 AP, IndiaSearch for more papers by this author First published: July 1989 https://doi.org/10.1002/pol.1989.140270803Citations: 1AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinkedInRedditWechat Citing Literature Volume27, Issue8July 1989Pages 259-261 RelatedInformation

Polymeric debris in synovium after total joint replacement

In studying a series of synovial biopsy specimens from patients with loose joint replacements, we were able to differentiate reliably between polymethylmethacrylate and ultra high-molecular-weight polyethylene by observing alterations in their birefringence with changes in temperature. The glass transition temperature of polymethylmethacrylate (when it softens from a glass-like to a rubber-like state) is about 105 degrees centigrade. Polyethylene melts at 135 degrees centigrade. The birefringence in polyethylene returns after it has been melted and then cooled; this is not true of methylmethacrylate fragments heated above their glass transition temperature. When cooled, methacrylate fails to regain its birefringence. In addition, free particles of the two plastics were studied in vitro to validate this method of differentiation. We recommend its use routinely in histological studies of patients with loosening.