Onset Temperature Of Thermal Degradation Research Articles

Nucleating and reinforcing effects of nanobiochar on poly(3-hydroxybutyrate-co-3-hydroxhexanoate) bionanocomposites.

This study promotes the use of nanobiochar (NBC) as an environmentally friendly substitute to conventional fillers to improve various properties of biopolymers such as their mechanical strength, thermal stability and crystallization properties. TGA analysis showed a slight increase in onset thermal degradation temperature of the composites by up to 5 °C with the addition of 4 wt% NBC. Non-isothermal DSC analysis determined that the addition of NBC into PHBHHx increases the crystallization temperature and degree of crystallinity of PHBHHx while isothermal DSC analysis demonstrated higher crystallization rate in PHBHHx/NBC composited by up to 54%. PHBHHx incorporated with NBC also exhibited superior tensile strength and modulus versus neat PHBHHx. Increase in mechanical strength was further proven via DMA where PHBHHx/NBC composites maintained higher storage modulus at higher temperatures when compared to neat PHBHHx. PHBHHx/NBC also exhibited no cytotoxicity effect against HaCat cells. This study demonstrates the ability of biochar to act as both nucleating agents and reinforcing agents in biodegradable polymers such as PHBHHx, which could be suitable for packaging application.

Waste natural fibers for polymer toughening and biodegradability of epoxy-based polymer composite through toughness and thermal analysis

Polymeric materials are being increasingly used to replace many metallic components due to their beneficial properties such as higher strength-to-weight ratio and corrosion resistance. However, the widespread use of polymers poses a risk to the environment as they are not biodegradable. The addition of the waste jute fiber and sawdust fiber as reinforcement to the epoxy resin improved its toughness and induced the biodegradability of the polymer. To examine the effect of the jute fiber and sawdust fiber on biodegradability, the composites were then kept in the drainage system for one year, and the impact energy and fracture morphology of the as-cast and weathered samples were examined using a drop ball impact test and a Charpy impact test. During the weathering period, weight gain was initially observed due to the water absorption by the porous fibers, but after three months, the composites started to lose weight due to the degradation of the fiber by swelling and microbial attacks. Microorganisms in the drainage system used the fiber as their energy source, which resulted in the deterioration of the fiber and the production of CO2. The production of CO2 was identified by the FTIR analysis of the weathered composite samples. TGA analysis of the as-cast and weathered samples reveals the reduction of the onset thermal degradation temperature of the weathered composites due to the degradation of the composites. The fiber disintegrated through microbial attack and the fiber swelling caused by the absorption of water by jute fiber and sawdust fiber is identified through SEM imaging. The SEM image also reveals the formation of biofilms and the growth of microorganisms at the fibers. A higher growth rate of the microorganisms was observed in the jute fiber composite than in the sawdust fiber composite, as sawdust contains a high level of lignin that protects it from degradation. The results of this study suggest that both sawdust fiber and jute fiber composites induce biodegradability in the epoxy matrix, but jute fiber was more prominent in this regard. The discovery paves the way for using natural fibers in biodegradable polymer composites, reducing polymeric pollution in the environment.

Effect of zirconia nanoparticles modified by silane coupling agent on some properties of epoxy coating

Effect of zirconia nanoparticles (zirconia NPs/ZrO2 NPs) modified by 3 wt.% (glycidyloxypropyl) triethoxysilane – GPTES (m-ZrO2 NPs) on some properties of epoxy coating such as mechanical properties, thermal stability and anti-corrosion performance was investigated. The obtained results indicated that the addition of zirconia nanoparticles to epoxy coating could enhance the properties of this coating. The addition of 2 wt.% of pure ZrO2 NPs (u-ZrO2 NPs) to the epoxy matrix could increase the mechanical properties (hardness and adhesion to the steel substrate) by approximately 10 %, the onset temperature of thermal degradation of the epoxy/u-ZrO2 NPs coating was 4.4 oC higher, and the anti-corrosion performance of epoxy coating was improved in comparison with the neat epoxy coating. Organically modified ZrO2 NPs had higher improvement for epoxy coating’s properties than pure ZrO2 NPs. The epoxy coating filled with m-ZrO2 NPs had 19.7 % higher in relative hardness, 88.73 % more in adhesion to steel substrate, 25.6 oC higher in the onset temperature of thermal degradation, and higher anti-corrosion performance in comparison with the epoxy coating filled with 2 wt.% of pure zirconia nanoparticles. The cross-section FESEM images of the epoxy/m-ZrO2 NPs coating showed that m-ZrO2 NPs could regularly disperse in epoxy polymer matrix while unmodified zirconia nanoparticles (u-ZrO2 NPs) were agglomerated to big cluster in the epoxy coating. This was the reason for the high performance of the epoxy coating filled with zirconia NPs modified by GPTES.

Digestibility Kinetics of Polyhydroxyalkanoate and Poly(butylene succinate-co-adipate) after In Vitro Fermentation in Rumen Fluid.

Using polyhydroxyalkanoate (PHA) materials for ruminal boluses could allow for longer sustained release of drugs and hormones that would reduce administration time and unneeded animal discomfort caused by continuous administration. The objective of this study was to determine ruminal degradability and kinetics of biodegradable polymers and blends. A proprietary PHA-based polymer, poly(butylene succinate-co-adipate) (PBSA), PBSA:PHA melt blends, and forage controls were incubated in rumen fluid for up to 240 h. Mass loss was measured after each incubation time, and digestion kinetic parameters were estimated. Thermogravimetric, differential scanning calorimetry, and intrinsic viscosity analyses were conducted on incubated samples. Generally, across treatments, mass loss was significant by 96 h with a minimum increase of 0.25% compared to 0 h but did not change thereafter. Degradation kinetics demonstrated that polymer treatments were still in the exponential degradation phase at 240 h with a maximum disappearance rate of 0.0031 %/h. Melting temperature increased, onset thermal degradation temperature decreased, and intrinsic viscosity decreased with incubation time, indicating structural changes to the polymers. Based on these preliminary findings, the first stage of degradation occurs within 24 h and PHA degrades slowly. However, further ruminal degradation studies of biodegradable polymers are warranted to elucidate maximum degradation and its characteristics.

Investigating effect of compatibilizer on polymer blend filament from post-used styrofoam and polyethylene for fused deposition modelling

This research produced the filament by blending the recycled polystyrene (rPS) from post-used Styrofoam and low-density polyethylene (LDPE). This study used polystyrene-grafted-maleic anhydride (PS-g-MA) as a compatibilizer to the rPS/LDPE blend. The formulated filaments were printed into specimens using a FDM printer. The visual inspection results showed that the printed specimens displayed better adhesion as the printing temperature and extrusion rate percentage increased. The addition of PS-g-MA also enhanced the adhesion of the printed layers. In terms of tensile properties, adoption of PS-g-MA also significantly improved the tensile strength and tensile modulus of the printed specimens. Furthermore, the addition of PS-g-MA increased the degree of crystallinity but it has shown no significant effect on the melting temperature. In addition, compatibilized rPS/LDPE blend samples possessed higher onset thermal degradation temperatures than the uncompatibilized rPS/LDPE blend sample, where higher onset thermal degradation temperature indicated that the material has better thermal stability. Overall, PS-g-MA was an effective compatibilizer to the immiscible rPS/LDPE blend filament where improvements of overall material properties and print quality can be observed, and especially with 5 wt% of PS-g-MA compatibilizer content, the tensile, thermal properties and print quality were improved the most.

Synthesis and Properties of One-Component Addition-Crosslinking Silicone Resin

A kind of MDT polysiloxane was prepared by step hydrolysis and polycondensation of alkoxysilane. It could be cured at elevated temperature with existence of microencapsulated platinum catalyst. The effects of crosslinkable groups’ contents and PhSiO1.5 content on properties of cured silicone resin were studied in detail. When the contents of crosslinkable groups were 20mol% to 30mol% and the PhSiO1.5 content was 25mol% to 30mol%, the cured silicone resin had good tensile strength, flexural strength, moderate elasticity, and low viscosity. With the increase of PhSiO1.5 content from 17mol% to 32mol%, Tg of the silicone resin could be improved by 50°C to 128°C. The thermal stability was explored by thermo gravimetric analysis. The onset temperature of thermal degradation and the center temperature of thermal degradation were 486°C and 548°C, respectively. The average dielectric constant was about 2.45 and the dielectric loss tangent value was less than 0.01. The silicone resin also showed a high-volume resistivity of 5.6×1016Ω•cm. These results suggest that such silicone resin is suitable for utilization in electronic packaging.

Viscoelastic, Thermal, and Mechanical Properties of Melt-Processed Poly (ε-Caprolactone) (PCL)/Hydroxyapatite (HAP) Composites.

Poly (ε-caprolactone) (PCL)/hydroxyapatite (HAP) composites represent a novel material with desired properties for various applications. In this work, PCL/HAP composites at low loadings were developed through melt-extrusion processing. The effects of HAP loading on viscoelastic, thermal, structural, and mechanical properties of PCL were examined. The morphological analysis revealed better dispersion of HAP at low loadings, while aggregation was noticed at high concentrations. The complex viscosity of the prepared composites increased with increasing concentration of HAP. In addition, a significant decrease in crystallinity was observed upon increase in HAP loading. However, the elongation at break increased with increasing the concentration of HAP, probably due to a decrease in crystallinity. The onset thermal degradation temperature of PCL was enhanced at low concentrations of HAP, whereas a decrease was observed at high loading. Overall, different degrees of HAP dispersion resulted into specific property improvement.

Investigation of Physico-chemical, Mechanical, and Thermal Properties of New Cellulosic Bast Fiber Extracted from the Bark of Bauhinia purpurea

ABSTRACT The alarming increase in the global pollution levels has necessitated the use of eco-friendly materials in composite making. Natural fibers derived from plant sources possess superior mechanical properties and proves to be a suitable alternate for synthetic fibers. In this paper, an attempt has been made to study the physico-chemical, mechanical, thermal, and morphological properties of new cellulosic fiber obtained from the bark of Bauhinia purpurea through various tests such as chemical, tensile, Fourier Transform Infrared Spectroscopy (FT-IR), X-ray diffraction (XRD), thermogravimetric (TG), differential scanning calorimetry (DSC), and field emission scanning electron microscopy (FESEM). From test results, Bauhinia purpurea fiber (BPF) was found to possess high cellulose (67.46 wt.%), with high crystallinity index (65.61%), and was found to offer high tensile strength (375.77 − 793.25 MPa) and large Young’s modulus (12.78–20.12 GPa). Lower density (1190 kg/m3) and high onset temperature of thermal degradation (225.55°C) make BPF more appropriate for making biodegradable composites for automobile and infrastructure sectors.

Immobilized lipase-catalyzed transesterification for synthesis of biolubricant from palm oil methyl ester and trimethylolpropane.

The present study reports the effects of three commercial immobilized lipases namely Novozyme 435 from Candida antarctica lipase B (CALB), Lipozyme TL IM from Thermomyces lanuginosus and Lipozyme RM IM from Rhizomucor miehei on the production of trimethylolpropane (TMP) ester from high oleic palm methyl ester (HO-PME) and TMP. The TMP ester is a promising base oil for biolubricants that are easily biodegradable and non-toxic to humans and the environment. Enzymatic catalysts are insensitive to free fatty acid (FFA) content, hence able to mitigate the side reactions and consequently reduce product separation cost. The potential of these enzymes to produce TMP ester in a solvent-free medium was screened at various reaction time (8, 23, 30 and 48h), operating pressure (0.1, 0.3 and 1.0mbar) and enzyme dosage (1, 3, 5 and 10% w/w). The reaction was conducted at a constant temperature of 70°C and a molar ratio of 3.9:1 (HO-PME: TMP). Novozyme 435 produced the highest yield of TMP ester of 95.68 ± 3.60% under the following conditions: 23h reaction time, 0.1mbar operating pressure and 5% w/w of enzyme dosage. The key lubrication properties of the produced TMP ester are viscosity index (208 ± 2), pour point (- 30 ± - 2°C), cloud point (- 15 ± - 2°C), onset thermal degradation temperature (427.8°C), and oxidation stability, RPVOT (42 ± 4min). The properties of the TMP ester produced from the enzymatic transesterification are comparable to other vegetable oil-based biolubricants produced by chemical transesterification.

Ultrasound-Engineered fabrication of immobilized molybdenum complex on Cross-Linked poly (Ionic Liquid) as a new acidic catalyst for the regioselective synthesis of pharmaceutical polysubstituted spiro compounds

A novel supported molybdenum complex on cross-linked poly (1-Aminopropyl-3-vinylimidazolium bromide) entrapped cobalt oxide nanoparticles has been successfully fabricated through two different procedures, i.e. ultrasound (US) irradiations (100 W, 40 kHz) and reflux. The efficiency of the two different methods was comparatively investigated on the fundamental properties of proposed catalyst using diverse characterization techniques. Based on the obtained results, the ultrasonication method provides controlled polymerization process; as a result, well connected polymeric network is formed. In addition, the use of ultrasound waves turned out to be able to increase the particles uniformity, specific surface area (from 79.19 to 223.83 m2/g), and the onset thermal degradation temperature (Td) value (from 248 to 400 °C) of the prepared catalyst which intensifies the catalytic efficiency. Besides, US-treated catalyst demonstrated high chemical stability and maintained its cross-linked network after eight cycles recovery, while the cross-linked network of catalyst obtained under silent condition was completely disrupted. Furthermore, the ultrafast multi-step fabrication procedure was performed in less than 6 h under ultrasonic condition while a similar process promoted by a mechanical stirring method came to a conclusion after 5–6 days. Accordingly, the utility of the ultrasound irradiation was proved, and US-treated catalyst was applied for improved synthetic methodology of spiro 1,4-dihydropyridines and spiro pyranopyrazoles through different acidic active sites. Due to the significant synergistic influence between the proposed catalyst and US irradiation, a variety of novel and recognized mono-spiro compounds were fabricated at room temperature in high regioselectivity.

Green one-step synthesis of cellulose nanocrystal/ ZnO nanohybrid with high photocatalytic activity

In this work, nanohybrid of zinc oxide/ cellulose nanocrystals (ZnO/CNC) was successfully prepared by using a low cost and green method for photocatalytic degradation of methylene blue (MB). CNC had been derived through the hydrolysis reaction by citric/hydrochloric acid from the pure cellulose isolated from Vietnamese Nypa fruticans trunk. The obtained CNC with carboxyl groups could act as a stabilizing and supporting agent to anchor ZnO nanoparticles. The chemical and crystal structures, morphology, thermal and photocatalytic properties of the ZnO/CNC nanohybrid were characterized by FESEM, FTIR, XRD, FESEM, BET, EDX, TGA, DRS and photocatalytic tests. Analyses of FTIR spectra, XRD, and FESEM indicated that the ZnO nanocrystals with the size of 50 nm formed and loaded on the surface of CNC. The TGA analysis demonstrated that the ZnO loading sample (ZnO/CNC) had the thermal degradation onset temperature higher than that of neat CNC. ZnO/CNC cuold be absorpted ultraviolet light and have high value of specific surface area (SBET), based on the DRS spectra and the nitrogen adsorption – desorption isotherms analysis, respectively. ZnO/CNC displayed more photocatalytic activity than pure ZnO upon degradation of methylene blue due to strong interaction between the CNC and ZnO nanoparticles. The maximum degradation of MB was about 95% in 150 minutes for the ZnO/CNC.

Investigations of structure development, electrical and thermal properties of polyvinylidene fluoride-expanded graphite nanocomposites

From natural graphite, expanded graphite (ExGr) has been synthesized using perchloric acid. Polyvinylidene fluoride (PVDF)–ExGr nanocomposites have been synthesized through non-solvent precipitation method followed by melt crystallization at 200°C and quenching in water at room temperature. The electrical percolation threshold has been found to be above 4 wt% ExGr in PVDF. With the addition of 0.5 wt% sonicated ExGr in PVDF-7 wt% graphite, the electrical conductivity is enhanced to two orders when compared to that of PVDF-7 wt% graphite. Thermogravimetric analysis proves very good dispersion of graphite nanosheets, as there exists at least 20°C enhancement in the onset temperature of thermal degradation with the addition of 3 wt% ExGr in PVDF. Structure development in PVDF due to the incorporation of ExGr particles has been understood through lattice mismatch theory. The impedance decreases with increase in the concentration of ExGr in PVDF at room temperature due to the formation of conducting channels. In another set of experiment, annealing of solution-casted films at 120°C for 5 h results in the formation of electroactive γ-phase, as confirmed through Fourier transform infrared and X-ray diffraction (XRD) analyses of representative samples. The composites are characterized by XRD, scanning electron microscopy and transmission electron microscopy.

Supernucleation, crystalline structure and thermal stability of bacterially synthesized poly(3-hydroxybutyrate) polyester tailored by thymine as a biocompatible nucleating agent

Naturally occurring thymine (TM) was incorporated into bacterial poly(3-hydroxybutyrate) (PHB) polyester to fabricate a novel and green biocomposite. Both 0.5% and 1% TM exhibit supernucleation effect on PHB, and crystallization kinetics suggests TM significantly increased Tc and Xc, and substantially shortened t1/2 of PHB. Epitaxial nucleation caused by a perfect crystal lattice matching between PHB and TM, was proposed to elucidate nucleation mechanism of PHB. Hydrogen bond interaction exists between CO, C–O–C groups of PHB and –CH3 (or –CH)/–NH– group of TM. TM interacted with CO group of PHB crystalline phase rather than that of amorphous one. In addition, two new IR crystalline bands assigned to C–O–C group of PHB appeared in the presence of TM, which arises from shift of two amorphous ones, respectively. TM enhanced onset thermal degradation temperature of PHB, mainly attributed to increased degree of crystallinity of PHB and flame retardance effect of TM.

Physicochemical properties of corn starch affected by the separation of granule shells

The physicochemical properties of corn starch (CS) and a component of granule shells (Cs) obtained through a granule shells separation process, were studied. The shells separation was accurately visualized and confirmed by SEM and TEM images. Both CS and Cs contained three components (amylopectin, intermediate fraction and amylose) with a Mw ranging from 4.11 × 107 to 11.42 × 107 g/mol. The amylose content of CS and Cs was in the following order: Cs-83 > CS > Cs-69 > Cs-76. There were no significant differences observed between CS and Cs-83 for the dynamic modulus, apparent viscosity, peak viscosity and final viscosity, while Cs-69 and Cs-76 exhibited a decreasing trend. The DSC results revealed that the transition temperatures of CS were significantly higher than those of Cs. There was an obvious decrease in the thermal degradation onset temperature (To) for the treated samples (CS:312.26 °C, Cs-69: 311.87 °C, Cs-76: 307.62 °C and Cs-83: 307.11 °C). The crystalline patterns of CS were converted from A-type to C-type during the granule shells separation process. The relative crystallinities of Cs were significantly lower than that of CS (26.87%). The FTIR results showed that intramolecular and intermolecular hydrogen-bonding (OH) of Cs were weakened after shells separation treatment.

Kinetics of thermal degradation and lifetime study of poly(vinylidene fluoride) (PVDF) subjected to bioethanol fuel accelerated aging

PVDF was prepared by compression molding, and its phase content/structure was assessed by WAXD, DSC, and FTIR-ATR spectroscopy. Next, PVDF samples were aged in bioethanol fuel at 60 °C or annealed in the same temperature by 30 ─ 180 days. Then, the influence of aging/annealing on thermal stability, thermal degradation kinetics, and lifetime of the PVDF was investigated by thermogravimetric analysis (TGA/DTG), as well as the structure was again examined. The crystallinity of ~41% (from WAXD) or ~49% (from DSC) were identified for unaged PVDF, without significant changes after aging or annealing. This PVDF presented not only one phase, but a mixture of α-, β- and γ-phases, α- and β-phases with more highlighted vibrational bands. Thermal degradation kinetics was evaluated using the non-isothermal Ozawa–Flynn–Wall method. The activation energy (Ea) of thermal degradation was calculated for conversion levels of α = 5 ─ 50% at constant heating rates (5, 10, 20, and 40 °C min─1), α = 10% was fixed for lifetime estimation. The results indicated that temperature alone does not affect the material, but its combination with bioethanol reduced the onset temperature and Ea of primary thermal degradation. Additionally, the material lifetime decreased until about five decades (Tf = 25 °C and 90 days of exposition) due to the fluid effect after aging.

Effect of casting solvent on the structure development, electrical, thermal behavior of polyvinylidene fluoride (PVDF)–carbon nanofiber (CNF) conducting binary and hybrid nanocomposites

The role of two solvents, namely N,N-dimethylformamide (DMF) and N,N-dimethylacetamide (DMAc), on the dispersion of CNF in PVDF matrix has been studied when the composites are synthesized by non-solvent precipitation route followed by melt crystallization at 200 °C and quenching in water. The electrical conductivities of melt-crystallized PVDF–CNF, PVDF-7 wt% graphite-CNF nanocomposites synthesized using DMAc solvent are higher than that of composites synthesized using DMF solvent. Thermogravimetric analysis of PVDF-7 wt% graphite, PVDF-3 wt% CNF suggests that the onset temperature of thermal degradation of the composite synthesized using DMAc is 20 °C higher than that of the same composite synthesized by using DMF. The SEM analysis of cross section of melt-crystallized, water-quenched PVDF-3 wt% CNF clearly proves better dispersion of CNF when DMAc solvent is used. Structure development in the polymer when CNF is incorporated has been understood in terms of lattice mismatch theory. DSC analysis proves the nucleating ability of CNF when incorporated in the polymer matrix as crystallization temperature (Tc) is enhanced by 5 °C. At low frequency (40 Hz), the intergranular capacitance is more than two times higher for PVDF-3 wt% CNF composites synthesized by using DMAc solvent when compared to that of DMF employed composites. The enhancement of storage modulus at − 90 °C for PVDF-7 wt% CNF composites synthesized by using DMAc solvent when compared to that of DMF employed same composite supports better dispersion of CNF in PVDF matrix in the former case as revealed by DMA.

Investigating Methylene Blue Adsorption and Photocatalytic Activity of ZnO/CNC Nanohybrids

Nanohybrids of zinc oxide/cellulose nanocrystals (ZnO/CNCs) were successfully prepared by using a low cost and green method for adsorption and photocatalytic degradation of methylene blue (MB). CNCs have been derived through the hydrolysis reaction by citric/hydrochloric acid from the pure cellulose isolated from Vietnamese Nypa fruticans trunk. The influence of the Zn2+ ion concentration on the morphology, microstructure, and thermal properties as well as the photocatalytic activity of the ZnO/CNC nanohybrids was investigated in detail. Analyses of FTIR spectra, XRD, and SEM indicated that the ZnO nanocrystals with the size of 50 nm formed and loaded on the surface of CNC. Based on the DRS spectra and the nitrogen adsorption–desorption isotherms (BET) analysis, the absorption of ultraviolet light with a strong absorption band around 400 nm was found for all the ZnO/CNC nanohybrids, and the values of specific surface areas (SBET) of materials can be controlled by changing the concentration ratio of Zn2+ ion and CNC. The TGA analysis demonstrated that the ZnO loading samples (ZnO/CNC) had the thermal degradation onset temperature higher than that of neat CNC. The effect of MB removal showed the results which were contributed not only by the adsorption ability of CNC but also by the photocatalytic activity of ZnO. The photocatalytic efficiency significantly depended on the content of ZnO loading. The maximum degradation of MB was about 95% in 150 min for the ZnO/CNC-1.0 sample in which the concentration ratio of zinc-precursor Zn(NO3)2·6H2O and CNC was 1.0.

Facile and solvent-free synthesis of a novel bio-based hyperbranched polyester with excellent low-temperature flexibility and thermal stability

In this work, a novel biobased hyperbranched polyester (HBPE) with excellent low-temperature flexibility (low Tg) and thermal stability, was prepared from the self-polycondensation of AB2 monomer based on methyl ricinoleate (MR), a commercially available derivative from castor oil. The AB2 monomer was facilely synthesized by UV-initiated thiol-ene addition between MR and 2-mercaptoethanol in the absence of solvents. The reaction parameters were systematically optimized, and the highest yield up to 98 % was achieved with almost complete conversion of double bond within 2 h. A series of HBPEs were then obtained via bulk polymerization of the AB2 monomer under different conditions. Among the four transesterification catalysts investigated, Ti(OBu)4 was demonstrated to be the most efficient one due to the higher polymerization efficiency and molecular weight (Mn = 13,000∼17,000 g/mol) of as-obtained HBPEs. And the degree of branching (DB) was estimated to be in the range of 0.30∼0.42. Notably, the HBPEs with dangling chains exhibited a low glass transition temperature (Tg) of ―42.8∼―59.2 °C, indicative of excellent low-temperature flexibility. TGA results indicated that the onset thermal degradation temperature under nitrogen exceeded 310 °C for all the HBPEs. In comparison to the polyrincinoleate as a linear polyester analogue, the HBPE behaved like Newtonian fluid behaviors with lower complex viscosities.

Effects of dioctyl phthalate on the properties of poly(vinyl chloride)/organically modified montmorillonite nanocomposites

The effects of dioctyl phthalate (DOP) loading on morphology and thermal and mechanical properties of the poly(vinyl chloride)/organically modified montmorillonite/DOP (PVC/O-MMT/DOP) nanocomposites are studied in this paper. Results of transmission electron microscope (TEM) indicate that O-MMT is partially intercalated and exfoliated in all PVC/O-MMT/DOP nanocomposites. It shows that the addition of DOP has no obvious influence on the dispersion of O-MMT in the PVC/O-MMT/DOP nanocomposites. Young’s modulus and tensile strength of the PVC/O-MMT/DOP nanocomposites are significantly decreased as the amount of DOP is increased. The thermal degradation onset temperature and glass transition temperature (Tg) of the PVC/O-MMT/DOP nanocomposites are decreased as the amount of DOP is increased. On the other hand, the elongation at break of the PVC/O-MMT/DOP nanocomposites is increased as the amount of DOP is increased. Also, the first thermal degradation weight loss (ΔY) of the PVC/O-MMT/DOP nanocomposites is increased as the amount of DOP is increased. While increasing DOP loading, the PVC/O-MMT/DOP nanocomposites change from a rigid product to a semirigid product and finally into a flexible product.

Synthesis, Molecular Docking Simulation, and Enzymatic Degradation of AB-Type Indole-Based Polyesters with Improved Thermal Properties.

We report the facile synthesis of a series of indole-based hydroxyl-carboxylate (AB-type) monomers by a one-step procedure. These monomers were successfully polymerized by melt polycondensation to yield AB-type polyesters with a varied number of flexible methylene units in the backbones. These indole-based AB-polyesters showed decent thermal stability according to the TGA results (onset thermal degradation temperature of >330 °C), and their glass transition temperatures are dependent on the length of the methylene bridge (Tg ≈ 62-102 °C) according to the DSC results. Furthermore, DSC and WAXD measurements revealed that these polymers did not crystallize from melt, but the ones with flexible structures could crystallize from solution. Molecular docking simulations showed favorable interactions between indole-based polyesters and polyethylene terephthalate hydrolase (PETase) from Ideonella sakaiensis. This was corroborated by the experimental results, which indicated that the PETase enzyme has degrading activity on the indole-based AB polyesters except for the one with the highest degree of crystallinity.