Increase In Tg Research Articles

Strain‐induced post‐curing of acrylate networks

AbstractThe mechanical properties and network structure of photocurable polymers are strongly dependent on processing conditions. Here it is reported that highly crosslinked acrylate systems undergo unexpected additional post‐curing during DMTA measurements, resulting in an increase in glass‐transition temperature (Tg). A detailed study of the conditions under which this increase in Tg takes place unequivocally shows that a small (0.1%) oscillatory strain applied above Tg is responsible for additional cross‐linking reactions. The effect of strain‐induced post‐curing is confirmed by applying post‐curing treatments under oscillatory shear strain in rheological tests. Different acrylate systems were characterized and the results show that the strain induced post‐curing depends on the network structure of the polymer. In polymer networks with an initial high crosslink density the effect is pronounced while in polymers with an initial lower crosslink density no shift in Tg is observed.

Effect of high pressure processing on migration characteristics of polypropylene used in food contact materials

ABSTRACT The migration of small molecular mass organic compounds from polypropylene (PP) copolymer films into food simulants during and after high pressure processing (HPP) was studied. An overlapping temperature profile was developed to isolate the pressure effect of HPP (700 MPa, 71°C, 5 min) from equivalent thermal processing (TP) at atmospheric pressure (0.1 MPa). Chloroform, toluene, methyl salicylate, and phenylcyclohexane were chosen as surrogate compounds, and were spiked into test polymer films at concentrations of 762–1152 mg kg–1 by a solvent soaking technique. Migration (w/w) of surrogate compounds from loaded PP films into Miglyol 812 (a medium-chain triglyceride mixture) and 10% ethanol was quantified by headspace GC/MS during HPP and TP, and subsequent storage at 25°C for up to 10 days. HPP significantly delayed migration of the surrogates from PP into both food simulants relative to TP. The average migrations into Miglyol after TP and HPP were 92.2–109% and 16–60.6%, respectively. Diffusion coefficients estimated by migration modelling showed a reduction of more than two orders of magnitude for all surrogate compounds under high pressure at 700 MPa ( = 8.0) relative to equivalent TP at 0.1 MPa ( = 13.1). The relative Tg increase of PP copolymer under compression at 700 MPa was estimated as Tg+94°C. For 10% ethanol, average migrations after TP and HPP were 9.3–50.9% and 8.6–22.8%, respectively. During extended storage, migration into both simulants from HPP-treated samples was initially slower than that from untreated or TP-treated films. However, after 8–24 hours of storage, the differences in percent migration of selected surrogates were not significant (p > .05) among the treated PP films. Therefore, the physical changes of PP films that occur during HPP appear to be reversible with a return to their original dimensions and diffusion properties after decompression.

Post-processing effects on microstructure, interlaminar and thermal properties of 3D printed continuous carbon fibre composites

3D printing of continuous carbon fibre reinforced composites (CCFRC) based on fused filament fabrication (FFF) has a great potential for reproducing robust and complex geometries, generating little waste. However, 3D printed CCFRC present relatively poor interlaminar bonding and high void content in comparison to traditional composites. This work analyses the post-processing temperature effects on microstructure, interlaminar properties and thermal stability of the printed CCFRC. Treated pieces at 150 °C showed a reduction of porosity by approximately 87% and improved interlaminar strength by 145%, without modifying nominal dimensions. In addition, the increase in Tg (from 109 °C to 131 °C) is ascribed to a drying effect during the post-processing, which reduces the plasticisation of the treated parts and contributes to the general enhancement of mechanical properties of printed CCFRC coupons. The proposed post-processing moves this technology towards the development of functional composite components for high-performance structural applications.

Effect of Crosslinker Amount on Properties of Poly Phenylacrylamide Gels

The monomer phenyl acrylamide was synthesized by reacting acrylamide with chloro benzene in the presence of pyridine. Fourier transform infrared spectroscopy (FT-IR) was used to characterize the resulting monomer. High conversion poly phenyl acrylamide (PPAM) containing 0, 0.5, 1, 1.5 and 2 wt % (in conversion to mass of PPAA) of N,N'-methylenebisacrylamide (MBAA) as crosslinker have been successfully synthesized. The effect of MBAA percentage on swelling parameters, clarity, mechanical and thermal properties of the prepared xerogels and hydrogels were studied. 1.5 wt % of MBAA is required to obtain clear xerogels and hydrogels. The water content (EWC), volume fraction of polymer (φ2) and weight loss during swelling decrease with increasing MBAA content. Young’s and shear modulus (E and G) increase as MBAA content increases, the values of E and G are 0.661–3.878 MPa and 0.423–2.588 MPa, respectively. The hydrogels were characterized in terms of modulus crosslinking density (ve and vt) and polymer-solvent interaction parameters (χ). The results are 0.252–0.661 mol/dm3 for ve, 0.211–0.541 mol/dm3 for vt, and 0.813–0.987 for χ. Thermal properties of polymers enhance (Tg increase) by adding MBAA. These types of polymers and their hydrogels possess new properties with potential uses in different medical applications.

Distribution characteristics of blood lipid profile in Hainan centenarians

Objective: To explore the prevalence of lipid profile and the influencing factors of dyslipidemia in centenarians in Hainan province, and provide basic data for the study of the lipid profile in centenarians. Methods: The data of this study were from the baseline data of China Hainan Centenarian Cohort Study from June 2014 to December 2016. A total of 1 002 centenarians were recruited. According to the guidelines for the prevention and treatment of dyslipidemia in Chinese adults in 2016, the prevalence of lipid profile were described and the prevalence of dyslipidemia with different clinical classifications were compared, and the main influencing factors were analyzed. Results: The median levels of TC, TG, LDL-C and HDL-C were 4.60 mmol/L, 1.05 mmol/L, 2.77 mmol/L and 1.41 mmol/L, respectively, in centenarians in Hainan. Blood lipid profile level was higher in females than in males. With the increase of BMI, TC, TG and LDL-C increased significantly, while HDL-C decreased significantly. The total prevalence of dyslipidemia was 19.1%. Smoking, BMI and area distribution were the main influencing factors of dyslipidemia. Conclusion: The prevalence of dyslipidemia in centenarians in Hainan was at a low level compared with other countries, and the blood lipid profile level was higher in females than in males.

Impact of lockdown COVID-19 on metabolic control in type 2 diabetes mellitus and healthy people

AimsThe impact of prolonged COVID-19 lockdown on metabolic control in type 2 diabetes patients and healthy individuals has not exactly been known. We aimed to evaluate the change in body weight and metabolic control in type 2 diabetic and non-diabetic healthy subjects during the prolonged lockdown period. MethodsDiabetic (n = 85), and age-and sex-matched non-diabetic subjects (n = 55) were included in this prospective study. Body mass index and metabolic parameters were compared between before and 6th months of lockdown. Changes in values were evaluated using the difference before and after lockdown. ResultsAge (54.81 ± 10.53 vs. 52.61 ± 4.88 years), gender (female, 68.2% vs. 56.4%) and, BMI (33.44 ± 6.48 vs. 31.63 ± 3.57 kg/m2) were similar between groups (p > 0.05). Before and after lockdown, BMI increased both in non-diabetic (0.54 ± 0.95 kg) and diabetic groups (1.91 ± 5.48 kg) (p > 0.05). Increase in HbA1c was more in diabetic than in non-diabetic groups (0.71 ± 1.35 vs. 0.02 ± 0.19%, p = 0.002). Glucose, LDL-C, and TG increased in diabetic (39.69 ± 74.69, 7.60 ± 34.33, and 58.21 ± 133.54 mg/dl, p < 0.05) whereas non significantly decreased in non-diabetic group (−0.51 ± 4.40, −3.52 ± 14.53, and −6.47 ± 41.77 mg/dl, respectively. After adjusting BMI, increase in blood glucose (p = 0.021), HbA1c (p = 0.018), and TG (p = 0.041) levels were more in diabetic than non-diabetic group. Duration of diabetes was an independent predictor of the change in HbA1c (OR: 1.2, 95% CI = 1.1–1.8, p = 0.032). ConclusionsBody weight gain was observed in type 2 diabetic patients and healthy subjects. This is the first study to show that prolonged lockdown COVID-19 pandemic worsened glucose regulation and increased TG level in diabetes mellitus independent of weight gain.

Study of the physical properties of 90 P2O5 + xV2O5 (10-x) BaO (0≤x≤3%) glasses

(90 P2O5 + x V2O5 + (10-x) BaO) (x = 0, 0.75, 1.50, 2.25 and 3.00 % in moles)) prepared by a melt quenching process. The physical properties, such as density (ρ) molar volume (VM), refractive index (n), metallicity (M), electron polarizability (α) and optical basicity (Λ), and were determined.XRD, DSC, Raman spectra, optical transmission, and photoluminescence spectroscopy were investigated at room temperature. The electrical properties were studied using an AC impedance spectroscopy. The observed increase in Tg with V2O5 reflects an increase in bond strength by the presence of the VOP bonds.At the 523−773 K temperature range following the Arrhenius law, the activation energy (≈0.276 eV) decreased with the Vanaduim rate. At the 423–523 K temperature range by Mott’s VRH model the highest density of Fermi states, N(Ef) values 3.45 1025 eV−1 cm-3 were obtained with PVB2.25 sample.Finally, the study exhibited a low relaxation time τrel≈1 μs and Vanadium substutition reduces the gap to 4.12 eV and the Urbach energy to 0.26 eV.

Correlation between Glycated Haemoglobin Values and the Lipid Profile in Type 2 Diabetic Patients

Background: To investigate the relationship between glycated haemoglobin (HbA1c) and the lipid profile in patients of type-2 diabetes. Methods: The study has been conducted on 32 patients of type 2 diabetes. These are patients diagnosed with Type 2 diabetes of age group between 30 and 70 years. Blood samples were collected after 12 hours of fasting where blood samples were drawn before and after a meal from the patients to measure levels of the sugar and lipids. Various biochemical assays were carried out including fasting plasma glucose (FPG), PPBG, HbA1c and lipid profile, along with the patient’s age, and gender. The method that has been used for doing these investigations is Kit Spinreact. Results: The study found that the participants have an increase in FBG, PPBG, HbA1C, TC, TG, VLDL-C and LDL-C, with a decrease in HDL-C concentrations in type 2 diabetic patients. The result showed a correlation of HbA1c with other variables. The HbA1c significantly correlated with FBG (r=0.531, P=0.000), PPBG (r= 0.699, P=0.000), Total Cholesterol (r= 0.339, P=0.006), Triglycerides (r=0.357, P=0.004), Low-density Lipoprotein (r=0.269, P=0.031) and Very low-density Lipoprotein (r=0.364, P=0.003) where it was not correlated with HDL (r=-0.182, P=0.149). Conclusion: The HbA1c was significantly associated with all variables (lipid profile) except HDL which did not reach the significant level. These findings suggest that HbA1c level can be used as a good parameter for predicting the lipid profile of type 2 diabetic patients.

Antidiabetic Activity of &lt;i&gt;Anemarrhena asphodeloides&lt;/i&gt; Bge. Polysaccharides

The present study was aimed to investigate the anti-diabetic activity of Anemarrhena asphodeloides Bge. Polysaccharides (AAP). Wistar rats were injected with streptozotocin(STZ)to induce diabetes. The APP was prepared at first. After the rats were orally administered for 28 days, related biochemical indicator were determined. AAP was composed of mannose, galacturonic acid, galactose, glucose and xylose in the molar ratio of 12:8.1:2.7:1.3:1 with the average molecular weight of 52.4 kDa. After treatment with AAP (100 and 200 mg·kg-1) for 28 days there was a significant decrease in blood glucose, SGPT, SGOT, ALP, TC, TG, LDL, BUN and significant increase in body weight, fasting serum insulin, pancreatic insulin and HDL. The activities of SOD and CAT in liver and kidneys also increased. The results of the experiments showed that AAP exerted significant anti-diabetic activity.

Study on the brewing industry waste combustion

The combustion of the waste from the brewing industry was investigated. Using the elemental analyzer and standard techniques, the elemental composition and technical characteristics of the studied sample were determined. The ignition and combustion of samples were carried out in a combustion chamber at heating medium temperatures (Tg) withinthe range of 500-700 °C. Gas-phase combustion products were analyzed using an in-line gas analyzer. The minimum ignition temperature of the sample was 337 °C. With an increase in the temperature Tg, a significant decrease in the ignition delay time of the sample was observed (by 9.7 times). The combustion process was accompanied by the formation of an intense flame near the sample surface. It was also found that, with increasing temperature of heating medium, the concentration of CO emission decreased with an inverse increase in the extremum value of CO2 emission.

Thermodynamic and Kinetic Transitions of Liquids in Nanoconfinement.

Core principles of chemistry are ubiquitously invoked to shed light on the nature of molecular level interactions in nanoconfined fluids, which play a pivotal role in a wide range of processes in geochemistry, biology, and engineering. A detailed understanding of the physicochemical processes involved in the flow, structural transitions, and freezing or melting behavior of fluids confined within nanometer-sized pores of solid materials is thus of enormous importance for both basic research and technological applications.This Account provides a perspective on new insights into the thermodynamic and kinetic transitions of nanoconfined fluids in their stable and metastable forms. After briefly introducing the unique properties of mesoporous silicas from the SBA, MCM, and FDU families that serve as the confinement matrices, combining highly ordered single and bimodal mesopore architectures with tunable pore sizes in the ∼2-15 nm range and narrow size distributions, recent studies on melting/freezing behavior of water confined in these host matrices are reviewed. While differential scanning calorimetry (DSC) reveals a linear relationship between melting point depression and pore size (independent of the pore shape), as predicted by the Gibbs-Thomson relation, variable temperature 2H wide-line nuclear magnetic resonance (NMR) spectroscopy studies confirm the core-shell model of water and give evidence for a layer-by-layer freezing mechanism, which gives rise to an apparent fragile-to-strong transition in the solidification dynamics.In contrast to the freezing/melting behavior of water, the effect of nanoconfinement on the glass transition of supercooled liquids is nonuniversal and the glass transition temperature Tg can either increase or decrease with the dimensionality and extent of confinement. This nonuniversal behavior is exemplified by the two glass-forming molecular liquids, glycerol and ortho-terphenyl (OTP). While glycerol shows an increase in Tg and a pronounced slowdown of the rotational dynamics of the constituent molecules due to a change in the molecular packing between the bulk and the confined liquid, OTP displays a linear and confining-media-dependent depression of Tg with increased confinement that is strongly influenced by the pore-liquid interface characteristics.This Account concludes with a focus on recent experimental evidence of extreme spatial and dynamical heterogeneity in both freezing and glass transition processes. This discovery was enabled by the unique mesoporous structures of SBA-16 and FDU-5, possessing bimodal architectures with two interconnected pore types of different size and shape (spherical and cylindrical). For the very first time, two melting points for water and two glass transitions for supercooled OTP, corresponding to a specific pore type, were observed. Collectively, these observations strongly suggest a close mechanistic connection between the local fluctuations in the structure and dynamics of nanoconfined liquids. While the findings reviewed in this Account provide new insights into thermodynamic and kinetic transitions of fluids, there remain many unanswered questions regarding the effects of nanoconfinement on the fundamental properties of fluids, which offer exciting future opportunities in chemical research.

Development of hydroxyapatite nanoparticles reinforced chlorinated acrylonitrile butadiene rubber/chlorinated ethylene propylene diene monomer rubber blends

AbstractHydroxyapatite nanoparticles (HA) reinforced polymer blend based on chlorinated nitrile rubber (Cl‐NBR) and chlorinated ethylene propylene diene monomer rubber (Cl‐EPDM) were prepared. Resulting blend composites were analyzed with regard to their rheometric processing, crystallinity, glass transition temperature (Tg), mechanical properties, oil resistance, AC conductivity, and transport behavior. The decrease in optimum cure time with the addition of HA is more advantageous for the development of products from these blend nanocomposites. The XRD, FTIR, and SEM confirmed the attachment and uniform dispersion of HA nanoparticles in the Cl‐NBR/Cl‐EPDM blend. The good compatibility between polymer blend and nanoparticles was also deduced by the formation of spherically shaped HA particles in the blend matrix determined by TEM analysis. DSC analysis showed an increase in Tg of the blend with the filler loading. The addition of HA particles to the blend produced a remarkable increase in tensile and tear strength, hardness, AC conductivity, abrasion, and oil resistance. The diffusion of blend composites was decreased with an increase in penetrant size. The diffusion mechanism was found to follow an anomalous trend. Among the blend composites, the sample with 7 phr of HA not only showed good oil and solvent resistance but also a remarkable increase in AC conductivity and mechanical properties.

Dynamic Changes of Blood Lipids in Breast Cancer Patients After (Neo)adjuvant Chemotherapy: A Retrospective Observational Study.

BackgroundPrevious studies indicated that the (neo)adjuvant chemotherapy for breast cancer can cause significant dyslipidemia in patients, but how long this abnormality can persist is unclear so far. The purpose of this study is to investigate whether (neo)adjuvant chemotherapy has a long-term effect on blood lipids in breast cancer patients.MethodsA total of 159 newly diagnosed female breast cancer patients receiving the (neo)adjuvant chemotherapy subsequently and 159 female healthy controls were enrolled into the observational study. All participants’ blood lipid profiles which included TC, TG, HDL-C, and LDL-C before and at the end of the 1st and 12th month after chemotherapy were retrieved from the electronic medical record system. The blood lipid profiles and the percentage of dyslipidemia before and after chemotherapy in breast cancer patients and controls were compared.ResultsCompared with the baseline before chemotherapy, TC, LDL-C, and TG increased significantly at the end of the 1st month after chemotherapy, but only the abnormal increase in TG (2.98±0.71 mmol/L vs 2.82±0.63 mmol/L, P<0.05) and LDL-C (1.82±0.42 mmol/L vs 1.59±0.42 mmol/L, P<0.05) continued until the 12th month after chemotherapy. Levels of HDL-C in breast cancer patients and all the blood lipid parameters in controls remained stable during the observation period. The percentage of dyslipidemia in breast cancer patients rose from 41.5% at baseline to 54.1% at the 12th month after chemotherapy. Subgroup analysis demonstrated that the increase in dyslipidemia percentage was more pronounced in patients with low body mass index and aged over 50 years.ConclusionThe (neo)adjuvant chemotherapy used for treating breast cancers can cause significant abnormalities in blood lipid profiles, and the abnormal increase in LDL-C and TG can last at least 12 months after chemotherapy, which indicates long-term management of blood lipid is necessary for those patients.

Optical properties and luminescence of Er3+/Yb3+ co-doped La2O3–Nb2O5–Ga2O3 glasses prepared by aerodynamic levitation method

40La2O3–20Nb2O5–40Ga2O3 and xYb2O3–5Er2O3–(35-x) La2O3–20Nb2O5–40Ga2O3 (x = 0, 1, 5, 10) spherical transparent glasses were prepared by aerodynamic levitation method. Upconversion and near-infrared luminescence characteristics have been studied. Moreover, the thermal, mechanical, refractive index, transmittance properties of the glasses have also been discussed. Hardness and density of the glasses increase with the increase of Yb3+ concentration. The hardness of all samples are above 8.4 GPa, and density increase from 5.2504 g/cm3 to 5.817 g/cm3. The blank LNG glass has a refractive index of 2.0217 and Abbe number of 88.84, which is an excellent glass with high refractive index and low dispersion. Through DTA analysis, it is found that this series of glasses has excellent thermal stability. The glasses transition temperature (Tg) is about 800 °C. With the increase of Yb3+ concentration, Tg does not change obviously, but the crystallization initial temperature To and △T (△T = To−Tg) increase at first and then decrease. Upconversion fluorescence spectra show that green and red emission bands of 551 nm, 558 nm and 674 nm are obtained under the pump of 980 nm laser, which are two-photon emission processes. And in the near infrared region, the near-infrared emission with the emission center at 1559 nm is obtained, which corresponds to the transition from 4I13/2–4I15/2 of Er3+. The full width at half maximum (FWHM) of the prepared samples is about 120 nm, which is larger than that of ordinary glass. At the same time, with the increase of Yb3+ concentration, the change trend of fluorescence lifetime is consistent with that of near-infrared emission intensity.

Iodine, thyroglobulin and thyroid gland.

Iodine is essential in the biosynthesis of thyroid hormones that affect metabolic processes in the organism from the prenatal state to the elderly. The immediate indicator of iodine intake is the concentration of iodine in urine, but the indicator of iodine intake in the longer term of several months is thyroglobulin (Tg). Tg negatively correlated with increasing intake of iodine in population that do not suffer from thyroid disease, while a more than adequate to excessive iodine intake leads to an increase in Tg. The dependence of Tg on iodine can be described by a U-shaped curve. Thyroglobulin in serum is elevated in thyroid disease mainly in hyperthyroidism (diagnosis E05 of WHO ICD-10 codes) and in goiter (diagnosis E04 of WHO ICD-10 codes). Tg values decrease below 20 microg/l after effective treatment of patients with thyroid disease. Thyroglobulin may thus be an indicator of thyroid stabilization and the success of the thyroid gland treatment.

Urinary copper, systemic inflammation, and blood lipid profiles: Wuhan-Zhuhai cohort study

Copper have been reported to be associated with metabolic diseases. However, results on copper exposure with blood lipid profiles are inconsistent, and the underlying mechanisms of this association remain unclear. This study focused on investigating associations between urinary copper and blood lipid profiles; and exploring the potential role of systemic inflammation in such relationships. Concentrations of urinary copper, plasma C-reactive protein (CRP), and four blood lipid parameters (e.g., Total cholesterol [TC], triglycerides [TG], low-density lipoprotein cholesterol [LDL-C], and high-density lipoprotein cholesterol [HDL-C]) were measured in the adult participants from Wuhan-Zhuhai cohort. The associations between copper, CRP, and four blood lipids were assessed by the multivariable linear regression models, and the 3D mesh graphs was used to examine the joint effects of copper exposure and CRP on four blood lipid parameters. In addition, we used mediation analysis to investigate the mediated effects of CRP in the relationships between copper exposure and blood lipid profiles. Each 1% increase in urinary copper was statistically significantly associated with a 5.32% (95% CI: 2.48%, 8.24%) increase in TG after adjusting for the confounders (P < 0.05). No significant associations were observed between urinary copper and the other three blood lipid parameters (all P > 0.05). In addition, urinary copper increased monotonically with plasma CRP elevation, which in turn, was positively associated with TC, TG, and LDL-C and negatively related to HDL-C (all P < 0.05). Results from 3D mesh graphs demonstrated that increased levels of plasma CRP with higher urinary copper corresponded to higher TC, TG, LDL-C, and lower HDL-C concentrations. Mediation analysis observed that CRP mediated 6.27% in the relationships of urinary copper and TG. These findings suggest that systemic inflammation partly mediated the association between copper exposure and abnormal blood lipid, and may contribute to the development of dyslipidemias.

Poly(p-xylene disulfide) and poly(p-xylene tetrasulfide): synthesis, cure and investigation of mechanical and thermophysical properties

In this work, two polysulfide polymers were synthesized using aromatic organic monomer (α,α′-dichloro-p-xylene) and sodium disulfide (Na2S2) and sodium tetrasulfide (Na2S4) aqueous monomers. Then, the curing process of the polymers was carried out at 170° C using a rheometer. The structural characteristics of synthesized and cured samples were identified by Raman and Fourier transform infrared (FT-IR) spectroscopies. Also, morphological and thermophysical properties of samples were studied by using the X-ray diffraction (XRD) and differential scanning calorimetry (DSC), respectively. Moreover, the molecular weight of the synthesized samples was determined by proton nuclear magnetic resonance (1H NMR). Furthermore, the mechanical properties and hardness of the samples were investigated by tensile test and Shore A. The results showed that in the noncured samples during the increase of sulfur in the polymer structure, solubility was increased whereas it decreased the hardness, melting point (Tm ) and glass transition temperature (Tg ) of polymers. But in cured samples, hardness and Tg increase by increasing sulfur and the mechanical properties also improved. This is due to the increase in crosslinks. Also, Tm and solubility are not observed due to the formation of crosslinks.

Epoxidation of Cardanol's Terminal Double Bond.

In this investigation, the terminal double bonds of the side chain epoxidized cardanol glycidyl ether (SCECGE) molecule were further epoxidized in the presence of Oxone® (potassium peroxomonosulfate) and fluorinated acetone. Regular methods for the double bond epoxidation are not effective on the terminal double bonds because of their reduced electronegativity with respect to internal double bonds. The terminal double bond functionality of the SCECGE was epoxidized to nearly 70%, increasing the epoxy functionality of SCECGE from 2.45 to 2.65 epoxies/molecule as measured using proton magnetic nuclear resonance (1H-NMR). This modified material—side chain epoxidized cardanol glycidyl ether with terminal epoxies (TE-SCECGE)—was thermally cured with cycloaliphatic curing agent 4-4′-methylenebis(cyclohexanamine) (PACM) at stoichiometry, and the cured polymer properties, such as glass transition temperature (Tg) and tensile modulus, were compared with SCECGE resin cured with PACM. The Tg of the material was increased from 52 to 69 °C as obtained via a dynamic mechanical analysis (DMA) while the tensile modulus of the material increased from 0.88 to 1.24 GPa as a result of terminal double bond epoxidation. In addition to highlighting the effects of dangling side groups in an epoxy network, this modest increase in Tg and modulus could be sufficient to significantly expand the potential uses of amine-cured cardanol-based epoxies for fiber reinforced composite applications.

Elucidating the Role of Interfacial Hydrogen Bonds on Glass Transition Temperature Change in a Poly(Vinyl Alcohol)/SiO2 Polymer-Nanocomposite by Noncovalent Interaction Characterization and Atomistic Molecular Dynamics Simulations.

A thorough experimental investigation of polymer-glass transition temperature (Tg ) is performed on poly(vinyl alcohol) (PVA) and fumed silica nanoparticle (SiNP) composite. This is done together with atomistic molecular dynamics simulations of PVA systems in contact with bare and fully hydroxylated silica. Experimentally, PVA-SiNP composites are prepared by simple solution casting from aqueous solutions followed by its characterization using Fourier-transform infrared spectroscopy (FTIR), dynamic mechanical analysis (DMA), and dynamic scanning calorimetry (DSC). Both theoretical and experimentally deduced Tg are correlated with the presence of hydrogen bonding interactions involving OH functionality present on the surface of SiNP and along PVA polymer backbone. Further deconvolution of FTIR data show that inter-molecular hydrogen bonding present between PVA and SiNP surface is directly responsible for the increase in Tg . SiNP filler and PVA matrix ratio is also optimized for a desired Tg increase. An optimal loading of SiNP exists, in order to yield the maximum Tg increase arising from the competition between hydrogen bonding and crowding effect of SiNP.

Wear and thermal resistance properties of aluminium particulate microcomposites

Wear resistance and thermal stability are not fundamental properties of materials, but their effects are inevitable in applications involving two-body contact because of friction-induced wear and heat. Wear resistance and thermal stability of epoxy containing 10% by weight of 66.34 μm aluminium particles were examined using mass loss per sliding distance approach and glass transition temperature (Tg) was used as a parameter for thermal stability. The results obtained revealed a reduction in the wear rate due to addition of aluminium particles. About 62, 58 and 39% reductions at 9 N/0.65 m s−1; 9 N/1.3 m s−1 and 25 N/1.3 m s−1, respectively imply that both sliding speed (v) and the applied load (F) contribute to an increase in the wear rate. A lower coefficient of friction of epoxy aluminium composites signifies lower surface wear rate in comparison with that of the epoxy polymer upon contact with another body in applications. The linear model establishes that v with a P value of 0.0046 has a greater significant influence on the wear resistance of the composite than F with a higher P value (0.0103). By the model, the epoxy aluminium composite under 24.63 N is expected to experience a wear rate of 0.000537 g m−1 which is 1380% lower than that established by the results of the experiment. About 36% increase in Tg is observed and 2FI model affirms that there is a gradual increase in Tg with heat flow through the sample during the glass transition period. Hence, the 2FI model having adequate precision of 164 > 4 is appropriate to be used for navigating a design phase for thermal stability properties.