FEM Analysis and Experimental Study on the Bending Strength of Ceramic Tiles with the Top- and Back-Sided Polyurea Coating

Mechanical properties enhancement of ceramic tiles by a simple coating technique using polyurea was investigated. Solventless polyurea coatings were employed. The effect of coating sides of the ceramic substrate and film thickness on the mechanical properties were examined in three-point bend tests. The back-coated ceramic tile demonstrated a significant improvement in bending strength (by 25–50%) as compared to the top-coated one. The stress distribution in the substrate was analyzed by the finite element method, and the mechanism of improving mechanical properties was discussed.Изучена возможность улучшения механических свойств керамической плитки путем нанесения покрытия из полимочевины. Использовано покрытие из полимочевины без растворителя. Влияние стороны нанесения покрытия на керамическую основу и толщины пленки на механические свойства исследовано при испытаниях на трехточечный изгиб. Прочность при изгибе керамической плитки с покрытием на нижней стороне существенно лучше (на 25...30%) по сравнению с таковой покрытия, нанесенного на ее лицевyю поверхность. Выполнен анализ распределения напряжений в основе с помощью метода конечных элементов и проведено обсуждение механизма улучшения механических свойств

Analysis of equations of state for polymers

AbstractIn the literature there are several studies comparing the accuracy of various models in describing the PvT behavior of polymers. However, most of these studies do not provide information about the quality of the estimated parameters or the sensitivity of the prediction of thermodynamic properties to the parameters of the equations. Furthermore, there are few studies exploring the prediction of thermal expansion and compression coefficients. Based on these observations, the objective of this study is to deepen the analysis of Tait, HH (Hartmann-Haque), MCM (modified cell model) and SHT (simplified hole theory) equations of state in predicting the PvT behavior of polymers, for both molten and solid states. The results showed that all equations of state provide an adequate description of the PvT behavior in the molten state, with low standard deviations in the estimation of parameters, adequate sensitivity of their parameters and plausible prediction of specific volume, thermal expansion and isothermal compression coefficients. In the solid state the Tait equation exhibited similar performance to the molten state, while HH showed satisfactory results for amorphous polymers and difficulty in adjusting the PvT curve for semicrystalline polymers.</p

High pressure analysis of the multiple melting endotherms of poly(ethylene succinate) and poly(butylene succinate)

The origin of the multiple melting peaks in two linear polyesters, poly(ethylene succinate) (PES) and poly(butylene succinate) (PBS), of isothermally crystallized samples was investigated by differential scanning calorimetry (DSC) at atmospheric pressure and high-pressure differential thermal analysis (HP-DTA) at elevated pressures. In PES, the DSC melting curves showed three endothermic peaks at slow heating rates, which decreased to two with increasing heating rates. The HP-DTA curves showed that the area (qualitative) and peak height of the high-temperature peak decreased with increasing pressure and merged with the low-temperature peak at pressures above 450 MPa. This behavior supported the melting, recrystallization, and remelting model for the observed multiple melting endotherms. In PBS, the DSC melting curves were similar to those seen in PES. The HP-DTA curves were also similar to PES up to 400 MPa, but above this pressure the area and the peak height of the high-temperature peak and the temperature difference between the high- and low-temperature peaks remained unchanged. This observation suggested that the two peaks in PBS were due to the melting of two populations of crystals with different lamellar thickness originally present in the sample. The multiple melting behavior in isothermally crystallized PBS is proposed to incorporate both the melting of two populations of crystals and melting, recrystallization, and remelting

Dominant factors affecting the pressure dependence of melting temperatures in homologous series of aliphatic polyesters

The pressure dependence of the melting temperature of six aliphatic polyesters belonging to two different homologous series, poly(x-succinate) and poly(x-adipate) having even number of methylene groups (2,4,6) in the alkylene segment (x) was investigated by high pressure differential thermal analysis (HP-DTA) up to 500 MPa. The phase diagrams of these polyesters were newly determined except for poly(ethylene adipate). The dTm/dpo at atmospheric pressure was obtained from the quadratic equation and the trend of dTm/dpo with respect to the number of methylene groups in the monomer unit in each homologous series is discussed. Amorphous densities at 25 °C, expansion and compressibility coefficients in the melt of these polyesters are also reported. The entropy of fusion (ΔSm), enthalpy of fusion (ΔHm), volume change on melting (ΔVm), conformational entropy (ΔSor) and volume entropy (ΔSv) were correlated with respect to the number of methylene groups in the alkylene segment. ΔVm and ΔSv displayed a similar trend as that of dTm/dpo while ΔSm, ΔSor and ΔHm showed an increasing trend. The influence of these parameters on dTm/dpo is discussed in the context of the Clapeyron equation

Non-isothermal melt crystallization of poly(tetramethylene succinate) under high pressure: characterization and kinetics

The non-isothermal melt crystallization behavior (characterization and kinetics) of poly(tetramethylene succinate) (PTMS) under high pressure was investigated using high pressure differential thermal analysis (HP-DTA). Wide angle X-ray diffraction (WAXD), small angle X-ray scattering (SAXS), differential scanning calorimetry (DSC), polarized optical microscopy (POM), and density measurement were used to study the crystal structure, the melting temperature and the morphology of the samples crystallized under various pressures. No new crystal structure or formation of extended chain crystals were found in the pressure crystallized samples. Optical micrographs revealed nucleation density decreased and spherulite morphology changed (presence of banding pattern) above 300 MPa. DTA crystallization curves showed a single exothermic peak at all pressures which shifted to higher temperatures with increasing pressure and became broad above 300 MPa. The kinetics was studied using the Ozawa model. A change in the nucleation pattern was predicted from the Ozawa exponent, instantaneous at low pressures and sporadic above 300 MPa. From kinetic and morphological results it was found that a critical pressure region existed around 300 MPa

Structural changes in poly(trimethylene adipate) and poly(trimethylene succinate) during melt crystallization studied using in situ infrared spectroscopy

This paper investigates the structural changes occurring in poly(trimethylene adipate) (PTAd) and poly(trimethylene succinate) (PTSu) during melt crystallization using differential scanning calorimetry (DSC) and in situ Fourier transform infrared (FT-IR) spectroscopy. Cooling thermograms revealed that PTAd had a faster crystallization rate than PTSu. Infrared (IR) bands of the two polyesters were assigned by correlating with the IR bands of polymers containing the trimethylene and the diacid segments. The bands at 1478, 1459, 1393, and 1364 cm−1 in PTAd and 1475, 1459, 1393, and 1361 cm−1 in PTSu were designated to the CH2 of the trimethylene segment. Changes in the IR band absorbance intensities of the CH2 and the C–O–C groups were monitored with time during melt crystallization. Structural changes of the trimethylene and diacid segments of PTAd occurred synchronously, while in PTSu the two segments changed sequentially. Normalized band intensities showed a time lag between the trimethylene and succinic acid segments. The acid segment showed a faster change compared to the trimethylene segment. Fourier transform infrared spectroscopy is shown to be a useful technique to study conformational changes during crystallization in polymers

A brillouin scattering study of a polymer blend showing upper critical solution temperature behaviour

10.1007/BF01033106Polymer Bulletin236609-614POBU