Glass Transition Temperature Of PMMA Research Articles

Solution Doping of PMMA-Based Step-Index Polymer Optical Fibers by Rhodamine B Near Glass Transition Temperature of PMMA

Solution doping is a facile approach to fabricating photoactive polymer optical fibers (POFs). However, previous studies reveal that only the cladding of step-index POFs can be doped by the solution doping method in methanol or aqueous solutions, whereas the fiber core is hardly doped. To dope the fiber core as well as the cladding, this study attempts to dope PMMA-based step-index POFs by raising the doping temperatures to near the Tg of PMMA. The results show that a considerable amount of rhodamine B (RhB) is doped in the fiber core, though the amount is still much less than that in the cladding. The highest content in the fiber core is 0.479 mg/g, which is achieved by doping the POFs in water at 110 °C for 8 h. At the same condition, the RhB content of the cladding is 11.5 mg/g. It is found that the high-temperature doping process leads to dramatic axial shrinkage and radial expansion of the POFs, due to the relaxation of the fiber core. The wrinkled cladding after doping suggests that the macromolecule orientation of the core is much higher than that of the cladding, and high orientation should be the main reason why the core is much more difficult to dope than the cladding. Additionally, the doping process at 90 °C in water does not increase the fiber loss regardless of the tremendous POF structure change. In short, the core of PMMA-based step-index POFs can be doped at a temperature near the Tg of the PMMA, making the solution doping technique more practicable for POF doping.

Quasi‐elastic neutron scattering study on dynamically asymmetric polymer blends

AbstractCompatibility between polymers with different glass transition temperatures controls the thermomechanical properties of blends. This work explores the segmental dynamics of poly(methyl acrylate) (PMA) chains when they are blended with polymers of different rigidities and miscibility. Inspired by the intriguing dynamic asymmetry of chains within the interfacial layer of nanoparticles, this study aims to understand dynamic heterogeneity in dynamically asymmetric blends of PMA/poly(methyl methacrylate) (PMMA), PMA/polystyrene (PS), and PMA/poly(ethylene oxide) (PEO) using the differential scanning calorimetry (DSC) and quasi‐elastic neutron scattering (QENS) measurements below and above the glass transition temperature of PMMA or PS. Results revealed that the segmental jump distance of PMA increased on blending due to volume enhancement. The reduced effective diffusivity of PMA in PMMA is attributed to PMMA's enhanced flexibility (lower characteristic ratio, ) and superior interaction (lower ) when compared with the PS environment. The results demonstrate that the chain rigidity and miscibility affect the free volume, interchain cooperativity, and segmental dynamics in dynamically asymmetric blends.

Float-stacked graphene–PMMA laminate

Semi-infinite single-atom-thick graphene is an ideal reinforcing material that can simultaneously improve the mechanical, electrical, and thermal properties of matrix. Here, we present a float-stacking strategy to accurately align the monolayer graphene reinforcement in polymer matrix. We float graphene-poly(methylmethacrylate) (PMMA) membrane (GPM) at the water–air interface, and wind-up layer-by-layer by roller. During the stacking process, the inherent water meniscus continuously induces web tension of the GPM, suppressing wrinkle and folding generation. Moreover, rolling-up and hot-rolling mill process above the glass transition temperature of PMMA induces conformal contact between each layer. This allows for pre-tension of the composite, maximizing its reinforcing efficiency. The number and spacing of the embedded graphene fillers are precisely controlled. Notably, we accurately align 100 layers of monolayer graphene in a PMMA matrix with the same intervals to achieve a specific strength of about 118.5 MPa g−1 cm3, which is higher than that of lightweight Al alloy, and a thermal conductivity of about 4.00 W m−1 K−1, which is increased by about 2,000 %, compared to the PMMA film.

Development of Poly(methyl methacrylate)/nano-hydroxyapatite (PMMA/nHA) Nanofibers for Tissue Engineering Regeneration Using an Electrospinning Technique.

The study explores the in vitro biocompatibility and osteoconductivity of poly(methyl methacrylate)/nano-hydroxyapatite (PMMA/nHA) composite nanofibrous scaffolds for bone tissue engineering (BTE). Electrospun scaffolds, exhibiting both low and high fiber orientation, were investigated. The inclusion of hydroxyapatite nanoparticles enhances the osteoconductivity of the scaffolds while maintaining the ease of fabrication through electrospinning. SEM analysis confirms the high-quality morphology of the scaffolds, with successful incorporation of nHA evidenced by SEM-EDS and FTIR methods. DSC analysis indicates that nHA addition increases the PMMA glass transition temperature (Tg) and reduces stress relaxation during electrospinning. Furthermore, higher fiber orientation affects PMMA Tg and stress relaxation differently. Biological studies demonstrate the composite material's non-toxicity, excellent osteoblast viability, attachment, spreading, and proliferation. Overall, PMMA/nHA composite scaffolds show promise for BTE applications.

Enhanced mechanical, electrical, thermal, and optical properties of poly(methyl methacrylate)/copper oxide nanocomposites for flexible optoelectronic devices via in‐situ polymerization technique

AbstractPolymethyl methacrylate (PMMA) with varied compositions of copper oxide (CuO) nanoparticles was synthesized using in‐situ free radical polymerization. UV–visible, FT‐IR, XRD, FE‐SEM, DSC, and TGA were employed to examine their structure, morphology, and thermal properties. The broadening and intensification of UV absorption, as well as the shift in IR peaks of PMMA with the addition of CuO, confirm their interactions. The reduction in optical bandgap values with the reinforcement of nanofillers confirms the existence of intermediate energy bands in nanocomposites. XRD indicated that polymerization with CuO reduced the amorphous nature of PMMA. The FE‐SEM image revealed that the dispersion of CuO altered the nonporous, rough surface of PMMA into a homogeneous shape. The reinforcement of CuO enhanced the thermal stability and glass transition temperature of PMMA. The mechanical strength, modulus, impact strength, and rigidity of PMMA were significantly improved through in‐situ polymerization. The electrical property analysis revealed that the AC conductivity increased with frequency, temperature, and filler content. The reduction in activation energy of AC conductivity with temperature points toward their semiconducting nature. PMMA/CuO nanocomposites with higher tensile strength, lower bandgap energy, higher conductivity, and thermal properties can be used to make flexible optoelectronic devices.Highlights A series of PMMA/CuO nanocomposites were synthesized and characterized. Enhanced optical property, thermal stability, and glass transition temperature. Possess excellent dielectric constant and AC conductivity. Mechanical strength and impact resistance of PMMA were greatly enhanced. A promising material for flexible optoelectronic and power storage applications.

Physical properties of zircon‐filled poly(methyl methacrylate) composites following heating around its glass transition temperature

AbstractZircon‐filled poly(methyl methacrylate) (PMMA) composites were synthesized, and their physical properties after ambient heat treatments were investigated. The sub‐micron zircon filler was obtained by purifying local zircon sand. The heat treatments were at 25°C (untreated), 55°C, and 70°C, around the glass transition temperature of PMMA. The crystal and molecular structures of the samples were investigated using X‐ray diffraction (XRD) and Fourier transform infrared (FTIR) spectroscopy. The thermomechanical, optical, and thermal (between RT and 550°C) properties of all composites were examined using dynamic mechanical analysis (DMA), UV–Vis spectroscopy, and differential thermal/thermogravimetric analysis (DT/TGA) instruments. XRD patterns showed that there were no crystal structure changes. FTIR peaks were reduced due to the heat treatment indicating the presence of PMMA molecular degradation in the heat‐treated samples. Meanwhile, DMA data showed that the heat‐treated samples exhibit a much lower room temperature storage modulus, that is, up to half as compared to the untreated ones. Furthermore, the heat treatment also affects the optical properties, including a slight drop of transmittance in UV‐A and visible regions but a slight increase of transmittance in UV‐B and UV‐C regions. Finally, the differential scanning calorimetry/thermogravimetry (DSC/TG) data show that the heat‐treated pure PMMAs become more challenging to undergo thermal degradation (i.e., mass drop).

Low-temperature Thermogravimetry Study of Post-Infrared-Exposure PMMA and PMMA/zircon Composites

A thermogravimetruic study of PMMA/zircon composites was performed at temperatures between 30 and 200°C, instead of above degradation temperature of PMMA at around 300°C. The focus of the study was to observe mass changes between the designated temperatures due to zircon filler and infrared (IR) exposure. Four samples were prepared, i.e. pure PMMA without IR exposure and with IR exposure, each without and with 1 wt.% zircon filler. The success of the synthesis of the composites was examined using x-ray diffraction (XRD). Thermal gravimetry (TG) data of samples at the designated temperatures were plotted to explain several thermal phenomena. Results showed that all samples exhibited a drop of 1.5-2% weight between 30 and 75°C with only a slight increase after IR exposure. The slight drop maybe due to water loss or evaporation of broken weak hydrocarbon bonds. There is a further slight increase in mass for the unexposed samples between 75 and 105°C, i.e. just before the glass transition temperature of PMMA. The mass decrease continued up to 135 °C for the unexposed pure PMMA and up to 135°C for the other samples, indicating that filler and IR exposure favored PMMA mass loss. After that, up to 200 °C, all samples gained mass which was presumably due to oxidation. The presence of filler and the IR exposure promoted a larger oxidation as a result of some breaking PMMA bonds.

PMMA stability under hydrothermal conditions

PMMA is a synthetic polymer of methyl methacrylate. PMMA is used widely in many applications and the interest in their physicochemical properties is growing. In this work, a hydrothermal study was carried out to evaluate the PMMA stability under hydrothermal conditions (up to 200°C), pH (2−10) and reaction time (up to 360 min). The water-PMMA system is affected by different mechanisms when dosed with bases or acids suggesting predominantly an interaction of ester groups with the medium. The results prove that the polymer is highly stable at the tested conditions. It is observed that water molecules are encapsulated in the polymer due to the softening and hardening during the process. This phenomenon was seen in the thermogravimetric analysis. The glass transition temperature of PMMA was slightly reduced after the treatment. This suggests that the hydrothermal process promotes the degradation of the shortest polymeric chains.

Thermomechanical Response of Fullerene-Reinforced Polymers by Coupling MD and FEM.

The aim of the present study is to provide a computationally efficient and reliable hybrid numerical formulation capable of characterizing the thermomechanical behavior of nanocomposites, which is based on the combination of molecular dynamics (MD) and the finite element method (FEM). A polymeric material is selected as the matrix—specifically, the poly(methyl methacrylate) (PMMA) commonly known as Plexiglas due to its expanded applications. On the other hand, the fullerene C240 is adopted as a reinforcement because of its high symmetry and suitable size. The numerical approach is performed at two scales. First, an analysis is conducted at the nanoscale by utilizing an appropriate nanocomposite unit cell containing the C240 at a high mass fraction. A MD-only method is applied to accurately capture all the internal interfacial effects and accordingly its thermoelastic response. Then, a micromechanical, temperature-dependent finite element analysis takes place using a representative volume element (RVE), which incorporates the first-stage MD output, to study nanocomposites with small mass fractions, whose atomistic-only simulation would require a substantial computational effort. To demonstrate the effectiveness of the proposed scheme, numerous numerical results are presented while the investigation is performed in a temperature range that includes the PMMA glass transition temperature, Tg.

Characterization and thermal kinetic analysis of PMMA/modified-MWCNT nanocomposites

This study represents the processing, characterization and thermal properties of poly(methylmethacrylate)/multi-walled carbon nanotube (PMMA/MWCNT) and PMMA/MWCNT-OH nanocomposites prepared using the solution casting method. The starting components and nanocomposites were characterized by Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), differential scanning calorimetry (DSC) and scanning electron microscopy (SEM). Morphological studies showed that MWCNT were well dispersed in the polymer matrix. Thermal degradation of nanocomposites occurred in three steps, similar to PMMA. Both MWCNT and MWCNT-OH increased the glass transition temperature of PMMA. The nanocomposite with the highest glass transition temperature of 111 °C was the one containing 0.25 wt% MWCNT-OH. Kissinger and FWO equations were used to analyze the kinetic data obtained at different heating rates. Using these equations, the activation energies were deduced to be 263 and 261 kJ/mol for PMMA in DMF, and 198 and 198 kJ/mol for PMMA in THF.

Air-dried porous powder of polymethyl methacrylate modified cellulose nanocrystal nanocomposite and its diverse applications

Owing to the advantages in storage, transportation and melt-processing, the powder form of cellulose nanocrystals (CNCs) as an attractive biomass filler is highly desired for the industrial application. Herein, by systematically tailoring the reaction conditions, we prepared the air-dried porous powder of CNCs modified with PMMA (CNCs-g-PMMA) via a green synthesis route, that is, using ceric ammonium nitrate (CAN) as an initiator in aqueous medium. Our results show that the porous powder of air-dried CNCs-g-PMMA can be easily obtained when the grafting ratio of PMMA was higher than 70 wt%. CNCs-g-PMMA porous powder demonstrates high specific surface area (47.8 m2/g), excellent hydrophobicity and oleophilicity properties. It therefore can be used as a filter for oil/water separation or as a highly efficient absorbing material. Moreover, benefiting from the improved thermal stability of CNCs and melt-processing character of PMMA, the porous powder of CNCs-g-PMMA has been converted to a transparent film by a simple compression molding. The as-prepared film demonstrates extraordinary UV shielding and mechanical stability upon heating. Particularly, there is an extraordinary increase in glass transition temperature of PMMA from 112.6 to 138.6 °C. This research provides a facile and green strategy to fabricate CNCs-g-PMMA porous powder, which shows industrial applications from different perspectives.

Effects of PVP incorporation on the properties of injection-molded high-performance ceramics with PEG-based binders

PEG/PMMA binder systems are among the most widely used water-soluble binders for ceramic injection molding. Binder-induced binder segregation in PEG/PMMA systems is mainly caused by the difference between crystallization temperature of PEG (below 50°C) and glass transition temperature of PMMA (~120°C). In this study, we have adopted the method of introduction of appropriate amount of PVP to reduce the binder-induced defects. A principle model was thus established for the suppression of PEG crystallization by PVP molecules. It was revealed that the mechanism by which PVP suppresses PEG crystallization is hydrogen-bonded formation between the carbonyl group of PVP and the hydroxyl groups of PEG molecules. This compresses the crystallization space of PEG molecules, and suppresses their crystallization. It was determined that the range of PVP content that can be safely removed via water debinding is 0–30wt/wt% PEGS. The incorporation of PVP could effectively enhance the homogeneity of the compact, reduce the size of pores formed after thermal debinding in the compact, promote densification, reduce defects after sintering and enhance the mechanical performance of the sintered bodies. Furthermore, the performance of the molded product was optimal when 20wt/wt% PEGS of PVP was added to the binder; the flexural strength and density of the resulting sintered body were 811MPa and 98.7%, respectively.

Impact of Bis-(3-triethoxysilylpropyl)tetrasulphide on the properties of PMMA/Cellulose composite

Poly(methyl methacrylate) (PMMA)-microcrystalline cellulose composites with improved interfacial interaction were prepared by solution casting method using Bis-(3-triethoxysilylpropyl) tetrasulphide (Si69) as coupling agent. The incorporation of microcrystalline cellulose into PMMA enhanced the mechanical as well as thermal properties over that of base polymer but not remarkably. So in the current study Bis-(3-triethoxysilylpropyl) tetrasulphide (Si69) is used as a coupling agent to improve PMMA-Cellulose adhesion. The composites were characterized using FTIR, 13C NMR, UV–Vis, 29Si NMR, XRD and SEM analysis. The results indicated that Si69 formed chemical bonds with both PMMA and cellulose. The effect of Si69 on the physical and mechanical properties of PMMA/Cellulose composite was investigated. Thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC) studies showed that the degradation temperature and glass transition temperature of PMMA shifted to higher temperature. The addition of silane coupling agent in to the PMMA/Cellulose improved the mechanical properties. The impact strength increased up to 72%, flexural strength by 37%. The composite exhibited 49% higher tensile strength and 50% storage modulus than pristine PMMA. The addition of cellulose to PMMA increased the dielectric constant and attained an AC conductivity of 1.4*10−4 S/m. The result proved that Si69 is compactable to both PMMA and cellulose and can be used as an effective coupling agent for PMMA/Cellulose system.

The glass transition temperature of PMMA: A molecular dynamics study and comparison of various determination methods

The glass transition temperature (Tg) governs the mechanical and physical performances of polymeric materials and thus their ultimate applications. Although an extensive body of research has focused on the study and determination of the Tg, thermal events at and around the Tg at the molecular level have not yet been fully understood. It is widely believed that, at and around the Tg, the intermolecular interactions and the structure of polymer change resulting in dramatic variations of the bulk properties of polymers. Therefore, the Tg could be determined by tracing the changes observed in macroscopic (bulk) and microscopic properties as a polymer system cools down. In this study, we attempted to estimate the Tg of isotactic polymethylmethacrylate (is-PMMA) employing the molecular dynamics simulations based on the united atom model. To achieve this, the polymer properties including the thermal conductivity, volume, thermal expansion and Young’s module were examined. Moreover, microscopic properties such as the radial distribution function (RDF) and motions of the polymer chains by the mean squared displacement (MSD) function and the non-bonded energy were assessed. It was shown that a unique break appears on the property-temperature curves around 440K irrespective of the MD simulation method. The Tg values obtained in this work were quite consistent with the experimental results reported in the literature. The study also indicated that the Tg increases with increasing the cooling rate and molecular weight of the polymer.

Atomic-scale thermal behavior of nanoimprinted 0.3-nm-high step patterns on PMMA polymer sheets

A 0.3-nm-high step pattern was formed on a poly(methyl methacrylate) (PMMA) polymer surface by thermal nanoimprinting a sapphire template. Large-area transcription was attained under the condition of ~0.2 MPa load for 300 s at 120 °C. We also observed the thermal deformation of the atomically stepped pattern formed on a PMMA surface by in situ atomic force microscopy at high temperature and found the atomic step pattern was stable near the imprinting temperature of 120 °C and also at about 20 °C higher than the bulk glass transition temperature of PMMA (105 °C).

High-strength thermoplastic bonding for multi-channel, multi-layer lab-on-chip devices for ocean and environmental applications

A solvent vapour thermoplastic bonding process is reported which provides high-strength bonding of PMMA over a large area for multi-channel and multi-layer microfluidic devices with shallow high-resolution channel features. The bond process utilises a low-temperature vacuum thermal fusion step with prior exposure of the substrate to chloroform (CHCl3) vapour to reduce bond temperature to below the PMMA glass transition temperature. Peak tensile and shear bond strengths >3 MPa were achieved for a typical channel depth reduction of 25 µm. The device-equivalent bond performance was evaluated for multiple layers and high-resolution channel features using double-side and single-side exposure of the bonding pieces. A single-sided exposure process was achieved which is suited to multi-layer bonding with channel alignment at the expense of greater depth loss and a reduction in peak bond strength. However, leak and burst tests demonstrate bond integrity up to at least 10 bar channel pressure over the full substrate area of 100 mm × 100 mm. The inclusion of metal tracks within the bond resulted in no loss of performance. The vertical wall integrity between channels was found to be compromised by solvent permeation for wall thicknesses of 100 µm which has implications for high-resolution serpentine structures. Bond strength is reduced considerably for multi-layer patterned substrates where features on each layer are not aligned, despite the presence of an intermediate blank substrate. Overall a high-performance bond process has been developed that has the potential to meet the stringent specifications for lab-on-chip deployment in harsh environmental conditions for applications such as deep ocean profiling.

Characteristics of novel transparent poly(methyl methacrylate)/silica nanoparticle hybrid film prepared based on entanglement-agglomeration transition mechanism

Using polydisperse poly(methyl methacrylate) (PMMA) and SiO2 nanoparticles with an average particle diameter of ~15 nm, transparent PMMA/SiO2 hybrid films could be fabricated based on the agglomeration mechanism of nanoparticles in the suspension. The calculated distance between the particles in the transparent films was ~30 nm, corresponding to the actual measured value of 31 nm obtained from the small-angle X-ray scattering intensity. Upon heating the transparent hybrid films to 140 °C, above the glass-transition temperature of PMMA, the transmittance of UV light decreased significantly with the heating time for hybrid films with Mw=9.6 × 104 and a critical molecular weight (Mc) of 3 × 104 or greater, at which PMMA chains show effective entanglement. However, for hybrid films with Mw=0.3 × 104 and with the Mc or a lower molecular weight, the initial high transmittance was sustained over the entire wavelength range even after a long period of heating, and no agglomeration of the SiO2 nanoparticles was observed. Such molecular weight dependence was also observed for monodisperse PMMA/SiO2 hybrid films, leading to an examination of the difference in the rates of polymer chain entanglement and disentanglement. The critical molecular weight (Mc), at which the entanglement effect of the PMMA chain occurs is ~3 × 104. When the PMMA molecular weight in the hybrid suspension and film is such that Mc < Mw, such formation of molecular chain entanglements acts as a driving force for the agglomeration of SiO2 particles. In cases in which the PMMA molecular weight in the hybrid suspension and film is such that Mw< Mc, because no effective entanglements are formed, there is no driving force for the agglomeration of the SiO2 nanoparticles.

Influence of drying procedure on glass transition temperature of PMMA based nanocomposites

A literature review of poly(methyl methacrylate) (PMMA) nanocomposites shows inconsistent results regarding the influence of the addition of nanofillers on the mobility of the system. In academic research, solvent based preparation methods are often used to prepare nanocomposites with the aim to obtain a good and controlled dispersion. However, little attention is paid to the influence of the used solvent on the properties of the nanocomposites. We show that in PMMA nanocomposites prepared via solution casting from different solvents, the apparent decrease in glass transition temperature is caused by insufficient drying and that when an adequate drying procedure is used, an increase in glass transition temperature is always observed.

Heat treatment effect on erosion behavior of poly(methylmethacrylate) for optical transmittance efficiency

Influence of heat treatment on optical transmittance of poly(methyl methacrylate) (PMMA) samples was investigated under solid particle erosion. Heat treatment was employed at 85°C for 1, 2 and 3h. Effect of heat treatment on physical, chemical, mechanical and thermal properties of PMMA samples was investigated by differential scanning calorimeter (DSC), thermogravimetric analysis (TGA), Fourier transform infrared (FTIR) spectroscopy, Vickers microhardness measurement methods. After these analysis, both pristine and heat treated PMMA samples were eroded at 15°, 30°, 45°, 60°, 75° and 90° impingement angles. Then, optical transmittance of all eroded PMMA samples was inspected by a UV–Vis spectrometer. Scanning electron microscopy (SEM) was used to explain the erosion mechanisms and to compare the roughness and optical transmittance of eroded PMMA surfaces.Heat treatment under glass transition temperature of PMMA increased the Tg and hardness values. According to erosion test results, both pristine and heat treated PMMA samples were showed ductile erosion behavior. However; maximum and minimum optical transmittance values of eroded pristine PMMA samples were obtained for the angles of 15° and 90°, respectively. A positive effect of heat treatment on optical transmittance of PMMA was obtained for all impingement angles, but most pronounced effect was seen for 15°.

Computational simulation for optimizing the thermal hyperfine patterning process and its experimental verification

Polymer for NanoImprint Lithograph (NIL) process has been developed as well as development of the process and equipment. It is significant to develop the investigation technique of thermal nano-indentation behavior and mechanical properties of polymer to fabricate high quality nanostructure by varying a variety of T(Thermal)-NIL process parameters. Necessity of database construction for material properties dependent on time at the room and elevated temperature has been growing because a NIL process has been widely used in industries. The D/B has been accumulated through many NIL simulation at room temperature. However, D/B construction at high temperature has not been performed. This paper demonstrates computational process for thermal nanoindenation by using ABAQUS to optimize hyper-fine patterning process through thermal nanoindentation. The experimental and numerical results are compared to validate the computational method. Therefore, PMMA was nanoindented under forming conditions which minimize the elastic recover and pile-up. Thermal nanoindentation experiments were conducted at the temperature between 110 and 150°C. Continuous Stiffness Measurement (CSM) was performed during thermal nanoindentation by using a nanoindenter and hot stage. The effect of the maximum indentation depth of 2000 nm on mechanical properties at glass transition temperature of PMMA was investigated.