Search

PRS® paraffin wax was encapsulated by means of suspension-like copolymerization of methyl methacrylate (MMA) with butyl acrylate (BA). The effects of the polymeric shell dry glass transition temperature ([T.sub.g]) and [...]

The poly ethylene terephthalate near the glass transition temperature highlights a strongly non linear elastic and viscous behaviour when biaxially stretched at high strain rates representative of the injection stretch blow moulding process. A non linear visco-hyperelastic model, where characteristics are coupled to the temperature, has already been identified from equi-biaxial tension experimental results. The weak form of the mechanical part of the model is presented and implemented into a finite element code developed in the Matlab environment and validated by comparing numerical simulation of equi-biaxial testing with the analytical solution in the isothermal case. Considering the thermal aspects, an experimental study, where PET sheets are heated using infrared (IR for short) lamps is also presented. The modeling of the IR radiation of the sheet helps to identify the thermal properties of the PET. The thermal model is then implemented in the finite element code, coupled to the 2D viscoelastic model. A discussion is made to justify the accuracy of the assumption made on homogeneity of the temperature field through the thickness. The simulation of the 20 plane stress equibiaxial test shows the important influence of the thermal aspects and the coupled thermo-mechanical software is used to quantify the self-heating phenomenon in the case of the biaxial elongations of PET sheets at high strain rates. POLYM. ENG. SCI., 53:2683-2695, 2013. © 2013 Society of Plastics Engineers, INTRODUCTION The injection stretch blow molding (ISBM) process that is managed at a temperature near or slightly above the glass transition temperature ([T.sub.g]) involves multiaxial large strains at high strain [...]

Poly(methyl methacrylate)-based copolymers were prepared by solution copolymerization of methyl methacrylate (MMA) with methacrylamide (MAAM) or methacrylic acid (MAA) in dioxane. The blends of poly (methyl methacrylate-co-methacrylamide) (MMA- MAAM) with poly(methyl methacrylate-co-methacrylic acid) (MMA-MAA) were prepared by solution blending. The thermal properties of the blends were studied by differential scanning calorimetry. A large positive deviation in the glass transition temperature (TO from the Fox equation was observed. The existence of strong hydrogen-bonding interaction between the two copolymers was indicated based on the Kwei equation and conformed by Fourier transform infrared spectroscopy. The contact angle measurements showed that the hydrophilicity of the blends is lower than the corresponding copolymers. POLYM. ENG. SCI., 53:2370-2377, 2013. 0 2013 Society of Plastics Engineers, INTRODUCTION Poly(methyl methacrylate) (PMMA) is a nonpoisonous, environmental polymeric material possessing many admirable advantages, such as high light transmittance, ease of processing, excellent dimensional stability, colorlessness, resistance to weathering corrosion, [...]

In this article, we analyzed the influence of isosorbide content on glass transition temperature and crystallinity of poly(L-lactide). Different synthesis methods were applied to determine optimal procedure for polymerization of L-lactide in the presence of isosorbide. Two procedures were performed with tin(II) 2-ethylhexa-noate as the catalyst: first, using the vacuum sealed vessel, and second, using microwave reactor bulk polymerizations. The solution polymerization (with trifluoromethanesulfonic acid as catalyst) was possible at the temperature of 40°C. Obtained polyesters had number average molecular weights ranging from 20,000 to 65,000 g [mol.sup.1], according to the gel permeation chromatography measurements. The polymer structure was characterized by Fourier transform infrared spectroscopy and proton nuclear magnetic resonance spectroscopy. Thermal properties of the obtained polymers were analyzed using thermogravimetry (TG) and differential scanning calorimetry (DSC). According to DSC measurements, the addition of isosorbide in the polyesters influenced the increase in both glass transition temperature and degree of crystallization for all samples. The results obtained by thermogravimetric analysis confirmed the strong influence of polymerization mechanism on synthesized poly(L-lactides) thermal properties. POLYM. ENG. SCI., 53:1374-1382, 2013. © 2012 Society of Plastics Engineers, INTRODUCTION Because of concerns for the global environment biodegradable polymers became appropriate alternatives for many petrochemical-based polymers. Bio-renewable and biodegradable materials, such as lactide (1) or isosorbide, are becoming more [...]

The cadmium sulfide/polystyrene (CdS/PS) nanocomposites with concentration (0, 2, 4, 6, and 8) wt% of CdS nanoparticles were prepared by solution casting method and characterized through fourier transform infrared spectroscopy (FTIR) and transmission electron microscopy (TEM) measurements. The particle size of nanoparticles is found to be around 15 nm. Glass transition and mechanical behavior of CdS/PS nanocomposites were investigated using dynamic mechanical analyzer (DMA). The mechanical properties such as Young's modulus and tensile strength were determined at room, as well as at elevated temperatures through their stress-strain curves. The result shows that glass transition temperature ([T.sub.g]) is shifted toward the higher temperature after the addition of CdS nanoparticles. The mechanical properties increased at low wt% loading of CdS nanoparticles and decreased for higher wt% loading of CdS nanoparticles. It was also found that mechanical properties decline with increase in the temperature. POLYM. ENG. SC1., 53:1223-1229, 2013. © 2012 Society of Plastics Engineers, INTRODUCTION As a result of the insatiable demand for new materials in emerging field like nanotechnology, the preparation and characterization of semiconductor-polymer nanocomposites is a rapidly evolving area of research [...]

Hot-embossing (HE) experiments were conducted on polymethyl methacrylate (PMMA) across its glass transition temperature from 92 to 142 ° C. The glass transition temperature (Tg) of the PMMA used in this study was ~ 102 ° C. The polymer samples were embossed to a depth of 0.8 mm (800 µm). The experiments were carried out at various temperatures for different hold times of 30, 90, and 180 sec during the embossing process. A few additional experiments were conducted at 142 ° C with cooling of the samples as well. The force required for embossing and the final depth of the embossed features were analyzed. Polymers, including PMMA, show significantly different material behavior around and above [T.sub.g]. The same was seen in the aforementioned tests; the trends observed for the force as well as the final depth changed considerably around 122 ° C ([T.sub.g] + 20). These findings will be used in developing material models for use in simulating the hot-embossing process. POLYM. ENG. SCI., 52:1284-1292, 2012. © 2012 Society of Plastics Engineers, INTRODUCTION Polymethyl methacrylate (PMMA) is an amorphous thermoplastic used in various industrial applications. PMMA is compatible with human tissues and allows for high-resolution features to be embossed onto it, thus [...]

We synthesized series of shape memory polyurethanes with amorphous reversible phase [(T.sub.g]-SMPUs) and systematically studied their microphase structure and shape memory properties. The (T.sub.g]-SMPUs having no or less hard phase showed lower shape recovery. When the volume fraction of hard phase was in the range of 20-30%, the (T.sub.g]-SMPUs exhibited the highest shape recovery. As the fraction of hard phase increased further the shape recovery decreased, because more polymer components with higher glass transition temperatures ((T.sub.g]s) would participate in strain storage. For the (T.sub.g]-SMPUs having similar (T.sub.g]s, those polymers having higher volume fraction of hard phase exhibited higher shape fixity, broader shape recovery region, and larger recovery stress. Increasing deformation strain could raise shape fixity and recovery stress but broaden shape recovery region. The highest recovery stress of a material could be achieved when the deformation occurred at its glass transition temperature below which decreasing deformation temperature could not increase recovery stress further. POLYM. ENG. SCI., 52:1015-1026, 2012. @ 2011 Society of Plastics Engineers, INTRODUCTION Shape memory polyurethanes (SMPUs) aroused increasing interests from both academia and industry in the past decades because of their extensive application potential in many fields [1-11]. SMPUs are the [...]

A study was conducted to determine the thermal transition, mechanical properties, phase morphology and blending of poly(phenylene sulfide) (PPS)/polyamides mixtures. It was found that semicrystalline aliphatic polyamides exhibit crystalline melting points while amorphous polyamides show a glass transition temperature. Experiments showed that a smaller viscosity difference between the blend components produces a finer dispersed phase. Most PPS/semicrystalline, aliphatic polyamide blends have poor strength, while PPS/amorphous polyamide blends are stronger than the pure PPS resin.