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Composites are fabricating by reinforcing waste bambara nut shell powder (BNSP) as a bio-filler into an epoxy resin matrix. The composite is fabricated by varying the mass fractions of filler in the range of 5–35 wt%. The effects of bio-filler content on physical, mechanical, and thermal properties are evaluated. The studies reveal that the tensile strength, tensile modulus, flexural strength, and impact strength increased with increasing bio-filler content. The highest mechanical properties of BNSP-loaded epoxy composites are achieved at bio-filler mass content of 15 wt%, whereas hardness increased for 5–35 wt% with peak value at 35 wt%. The water absorption and thickness swelling of the BNSF/epoxy composites increased with increasing bio-filler contents, while the density decreased with an increase in bio-filler content. The TGA results revealed that an increasing bio-filler content decreased thermal stability, whereas the Tg and Tm of the composites increased with increasing bio-filler content. [ABSTRACT FROM AUTHOR]

In this study, wet ball milling and hot press methods were used to prepare nanocomposite from ultra-high molecular weight polyethylene (UHMWPE) as a matrix, and modified multi wall carbon nanotubes (MWCNTs) as reinforcement nano-additives. Two batches of MWCNTs were used (Pristine-MWCNTs-B1, and Pristine-MWCNTs-B2). First, the MWCNTs were oxidized (oxide-MWCNTs) by wet chemistry using strong acids, then further functionalized with an amide group (A-MWCNTs). Fourier-transform infrared spectroscopy (FTIR), and Thermal gravimetric analysis (TGA) results confirm the functionalization of the MWCNT with the amide group. Scanning electron microscopy (SEM) and X-ray diffraction (XRD) were used to examine the surface morphology and crystalline behavior of MWCNT after functionalization. Ball milling was used to mix the UHMWPE with pristine MWCNT (1.5% wt), Oxide-MWCNT (1.5% wt), and A-MWCNTs (0.5–2% wt). Then, hot press melting was used to prepare the nanocomposite sheets. Fourier transform infrared spectroscopy (FTIR) confirmed the impact of the balls milling process with time factor on UHMWPE crystallinity and the interaction of the functionalization MWCNT with the UHMWPE matrix. The structure (crystallinity, crystal size) was validated using X-ray diffraction (XRD) patterns. Thermal gravimetric analysis (TGA), differential scanning calorimeter (DSC), and universal testing machine (UTM) were utilized to analyze the structural, thermal, and mechanical properties of the nanocomposites, respectively. The results showed that UHMWPE crystallinity increased after 2 h of ball milling, while crystallinity decreased when pristine-MWCNT, oxide-MWCNTs, and A-MWCNTs (0.5–2 wt%) were added without affecting the crystal structure of UHMWPE. The results showed that adding 1.5 wt% A-MWCNTs-(B1, B2)/UHMWPE increased thermal stability by 16 °C and elongation at the break by up to 74% when used 1.5 wt% A-MWCNT-B1 and 2 wt% A-MWCNT-B2. This shows that the ball milling methods and amide group improved the dispersion and interface interaction between MWCNTs and UHMWPE matrix. [ABSTRACT FROM AUTHOR]

This study focused on an important global issue containing both environmental pollution control and energy storage. Polyaniline has been utilized as a supporting material to load paraffin in order to form highly thermal conducting and shape-stable phase change material (PCM). Three different weight percentages (wt%), i.e., 10, 15, and 20 wt%, of polyaniline have been used to obtain shape-stable composite materials. The paraffin leakage of the prepared samples PPCM1, PPCM2, and PPCM3 has been examined by 500 thermal cycles in a hot air oven at 80 °C. Among three samples, the PPCM3 composite with 20 wt% of polyaniline in paraffin has shown excellent leakage-bearing properties with only ~ 0.06% leakage after 500 thermal cycles. Further, the chemical, structural, and morphological analyses of the PPCM3 composite have been carried out by FTIR, XRD, and FESEM. The thermal performance of the prepared sample has been studied by thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC) analysis, which revealed that the impregnation of polyaniline polymer has improved the thermal stability and thermal conductivity of paraffin with a small decrement in latent heat capacity of the PPCM3 composite. The latent heat of the composite decreased by 18.36% and thermal conductivity increased by ~ 65.45% for a 20 wt% concentration of polyaniline in paraffin with the maximum latent heat capacity. To check the thermal reliability of the formulated PPCM3 composite, the composite has been subjected to thermal cycling of 500 thermal cycles. With increased thermal conductivity, high latent heat capacity, good shape stability, excellent leakage-bearing capability, and improved thermal reliability, paraffin/polyaniline composite PCMs look promising for application in thermal energy storage areas. [ABSTRACT FROM AUTHOR]

Sealants are easily subjected to microbial attachment, colonization, and deterioration in humid environment. Developing antimicrobial sealants have become an extremely imperative strategy to solve this problem. A kind of antimicrobial sealant was prepared with silane-modified polyether (SMPE) as a matrix and 3-(trimethoxysilyl) propyldimethyloctadecylammoniumchloride (TPOAC) as an antimicrobial agent in a room-temperature curing system. The tack-free time testing indicated that the introduction of TPOAC can significantly accelerate the curing rate of sealants. The effects of TPOAC on the mechanical, bonding, and thermal properties and surface wettability of the antimicrobial SMPE sealants were investigated through mechanical testing, thermogravimetric analysis (TGA), and water contact angle measurement. The mechanical properties of sealants were improved with an appropriate content of TPOAC, and the sealant exhibits optimal mechanical properties with the TPOAC content of 1.5%. Furthermore, TGA results indicated that the thermal behavior of SMPE sealants displayed a one-step weight loss process by heating in a nitrogen atmosphere and the introduction of TPOAC has little effect on the thermal stability of SMPE sealants in a nitrogen atmosphere. Moreover, the sealants exhibit more and more hydrophobic with the amount of TPOAC increased. The findings of this investigation indicated that using TPOAC as an antimicrobial agent is a practical way to obtain antimicrobial SMPE sealants with favorable properties. [ABSTRACT FROM AUTHOR]

The matrix's dielectric constant can be reduced with little quantity of POSS because of its unique cage skeleton structure and remained air in the caves. After epoxied, epoxy polyhedral oligomeric silsesquioxane (EPPOSS) promoted its compatibility with bisphenol A cyanate ester (BADCy) and bisphenol A benzoxazine (BA-a) by a curing processing between BADCy and EPPOSS and further copolymerizing with ring opened BA-a. Consequently, two Tgs were observed in the integrated nanocomposite, attributing to the BADCy homopolymer and the BADCy and BA-a copolymer. The more quantity of EPPOSS, the lower dielectric constants of nanocomposites achieved, as well as the initial storage modulus and Tgs due to the flexible ether bonds generated by EPPOSS. With up to 15 wt.% EPPOSS, the dielectric constant decreased to 2.72 at 1 MHz. The toughness and thermal stability of the nanocomposites also enhanced through increased the crosslinking density and inorganic Si–O–Si framework of EPPOSS. [ABSTRACT FROM AUTHOR]

In this study thermal and structural properties characterization were performed for prepared ultra-high molecular weight polyethylene/carbon nanotube (UHMWPE/CNT) nanocomposite sheets by using a melt compounding method. The sheets were prepared by using six types of CNTs; pristine single walled CNTs (SWCNTs) and multi-walled CNTs (MWCNTs), oxidized- SWCNT and MWCNT, and amide- SWCNT and MWCNT. Thermogravimetric analysis results revealed that the addition of CNTs increased the nanocomposites thermal stability (17 °C) being produced by P-MWCNT. Differential scanning calorimetry and x-ray diffraction (XRD) results show no significant crystalline structure changes compared with the pure polymer, and increase in crystallinity (4%) for O-SWCNTs additions (4%). Scanning electron microscope images showed improved bridging in the polymer matrix by using oxidized and functionalized CNTs compared with pristine CNTs. These findings suggest that the durability of UHMWPE is enhanced by this nano-modification method, improving its suitability for many lightweight, high strength material applications. [ABSTRACT FROM AUTHOR]

Developing of high-performance thermosets with outstanding thermal properties has attracted increasing attention. Herein, a combined strategy, acetylene modification and copolymerization with bismaleimide, has been utilized for a novel bio-based tri-functional benzoxazine monomer. The monomer (RES-pa) was successfully synthesized using biomass resources, resveratrol, as raw material. Three systems with different ratios (RES-pa: bismaleimide = 1:0, 1:1, 1:2) were designed. The thermal derived polymerization of three systems was monitored by DSC and in situ FT-IR. Thermal stability of derived thermosets was systemically investigated in detail by dynamic mechanical analysis (DMA) and thermogravimetric analysis (TGA). Specially, poly(RES-pa-co-DDM-BMI-1/1) is found to show a high Tg value of 374 °C and Td10 of 387 °C. Promisingly, the combined strategy used in the work may grant efficient way for design and preparation of high-performance thermosets. [ABSTRACT FROM AUTHOR]

This paper focuses on the use of castor oil plant (Ricinus communis) as filler in rotomolded parts using polyethylene (PE) and polylactic acid (PLA) as polymer matrixes. The vegetable shredded material was used in 5 and 10% weight following a dry blending procedure and then rotomolded to obtain cube test parts. This material was characterized to determine its chemical composition, thermal stability, and structure. The NaOH-treated material shows reduced hemicellulose content and higher thermal stability. Obtained composite materials were characterized in terms of mechanical (tensile, flexural, and impact) and thermal properties, morphology, and bio-disintegration behavior. The use of Ricinus as filler in rotomolded PE composite decreases, in general terms, mechanical properties of neat PE, while no significant changes in thermal or bio-disintegration properties are found. On the contrary, PLA composites show higher tensile strength and similar Young's modulus than the matrix, although with reduced flexural and impact properties. Alkali-treated Ricinus material produces parts with higher porosity and thus, lower mechanical properties than composites with untreated material. Finally, the incorporation of this vegetal material modifies to a great extent the thermal properties of the PLA matrix. The bio-disintegration rate increases due to the use of fibers, probably because of the higher moisture absorption of composites. [ABSTRACT FROM AUTHOR]

In this research, CuO2@SiO2@polythiophene nanospheres are fabricated through a facile and stepwise synthesis process. Cu@polythiophene yolk–shell nanoparticles are obtained after converting Cu2O to Cu and removing the middle layer of SiO2 by using dilute acid. Transmission electron microscopy (TEM) confirms that the movable Cu cores are encapsulated in the interior of the hollow polythiophene nanospheres. The structure, morphology and optical properties of the synthesized nanoparticles are characterized by X-ray diffraction, field emission scanning electron microscopy (FE-SEM) and ultraviolet–visible absorption spectroscopy. Uniform Cu@polythiophene nanoparticles with yolk–shell structure are applied as conductive filler in the poly(vinyl alcohol) matrix, and the effect of various nanofiller contents on the electrical, mechanical and thermal properties of the flexible polymer thin films is investigated. The FE-SEM images indicate that no agglomerates are seen on the surface of poly(vinyl alcohol) by adding the nanofiller amount up to 4 wt.%. Moreover, an increase in the direct current conductivity of nanocomposites is observed from 2 to 10 S/cm, as a result of the increase in contents of Cu@polythiophene nanoparticles from 0.2 to 3.6 wt.%. Tensile test of thin films reveals that the mechanical properties of the nanocomposites are improved by increasing the content of nanofillers, so that when compared with the pure poly(vinyl alcohol) film, the poly(vinyl alcohol) with 4 wt.% of Cu@polythiophene shows a 238% and 23% increase in Young's modulus and tensile strength, respectively. Besides, the results of the thermogravimetric analysis (TGA) indicate that the composite thin films are thermally more stable than the pure poly(vinyl alcohol) films. [ABSTRACT FROM AUTHOR]

Some disadvantages of commercial dressings have mobilized research groups to clinically improve these materials considering their cost–benefit ratio. Tissue engineering has emerged as a field that uses biomaterials in the form of scaffolds mimicking human morphofunctionality and their combination with cells in order to repair or replace damaged tissues. There is still a need for customization and characterization of the material to ensure its safety. Therefore, this study aimed to perform further characterizations of the gelatin (Gel)–coated poly(ε-caprolactone) (PCL) matrix produced in previous studies by rotary jet spinning. PCL fibers produced by rotary jet spinning were submersed in a Gel solution, inspired by the dip-coating method, followed by crosslinking with glutaraldehyde. The material was then submitted to physicochemical and biological characterization. The thermal properties were confirmed by differential scanning calorimetry. Significant differences were observed in the fiber thickness and swelling of PCL/Gel compared to PCL, while fiber spacing was greater for PCL. The crosslinked Gel appeared to increase the tensile strength of PCL, and the thermal stability of PCL/Gel was higher than that of Gel alone. In addition to the absence of cytotoxicity of the materials, the cytochemical data suggest higher cell activity on the PCL/Gel scaffold. Scanning electron microscopy reinforces this observation, indicating promising applications of PCL/Gel scaffolds in skin tissue engineering. [ABSTRACT FROM AUTHOR]

The study describes the potential use of dolomite MgCa(CO3)2 and magnesite MgCO3 carbonates micro-particles to enhance the thermal properties of bio-based polyamide 11 (PA11). These two micro-particle fillers were first carefully analyzed in terms of composition (XRD, XRF, and FTIR), microstructure (SEM) and thermal behavior (TDA/TGA). The incorporation of these mineral fillers to PA11 by extrusion using a coupling agent conducted to an increase in thermal stability compared to the neat matrix based on TGA measurements. SEM investigations revealed that the micro-particles were well distributed and dispersed within PA11, and a good interfacial adhesion with the polymer matrix was also noted. Dolomite and magnesite were successfully used to increase the thermal stability of bio-based PA11. Nevertheless, magnesite was proved to have a higher interaction with the PA11 matrix compared to dolomite by increasing its crystallization temperature based on DSC measurements and further increasing thermal stability for a low filler content. [ABSTRACT FROM AUTHOR]

This work was focused on the synthesis of polyurethane networks (PUNs) based on polycaprolactone (PCL) as soft segment (SS) and Boltorn® aliphatic hyperbranched polyester of the second pseudo generation and 4,4′-diphenylmethane diisocyanate (MDI) as the parts of the hard segments (HS), by a two-step solution polymerization. In order to find the best ratio between HS and SS to achieve good thermal and mechanical properties, suitable hydrophobicity and morphology of the PUNs, various experimental analyses were conducted. The obtained results revealed that features of the PUNs highly depend on the PCL content. The increase in the PCL content leads to the increase in thermal stability, hydrophobicity and appearance of the microphase separation, but on the other side, it also leads to the decrease in storage modulus in the rubbery plateau, crosslinking density and glass transition temperatures of PUNs. This work shows that features of PUNs can be easily adjusted for a specific application by careful selection of the SS and HS ratio. [ABSTRACT FROM AUTHOR]

We report a method of in-situ modification of phenolic resin (PR) on improving thermal stability with graphene/SiO2 hybrids at an ultralow filler loading. GO/SiO2 hybrids were prepared by electrostatic adsorption method and chemically reduced to RGO/SiO2 hybrids by NaBH4. The effect of in-situ modification of PR by GO/SiO2 and RGO/SiO2 on thermal stability of PR was studied. The results of SEM, XRD and FTIR showed that the hybrids and in-situ polymerization had a significant effect on improving the thermal property of PR. The TG and DTG analyses demonstrated that the thermal performance of PR in 350–500 °C was improved prominently. The T5% and T10% of 0.1 wt% (RGO–SiO2)/PR were increased by 165.56 °C and 89.23 °C compared with the pure PR, reaching 381.77 °C and 466.20 °C, respectively. Moreover, the R800°C of 0.1 wt% (GO–SiO2)/PR and 0.1 wt% (RGO–SiO2)/PR reached 69.86 wt% and 70.20 wt%, which increased by 10.75% and 11.29%, respectively, compared with pure PR. Therefore, the application of graphene/SiO2 hybrids in the in-situ polymerization modification of PR can significantly improve the thermal stability of PR and broaden its application fields. [ABSTRACT FROM AUTHOR]

Both pyrogallol-furfurylamine-based and pyrogallol-aniline-based di-benzoxazines (PG-FA and PG-A) possess a free hydroxyl and latent catalytic characteristics. To decrease the ring-opening polymerization (ROP) temperature of benzoxazine based on phenol and 4,4′-diaminodiphenylmethane (P-DDM) and increase simultaneously thermal property of its polymer, PG-FA and PG-A as catalysts were introduced into P-DDM. DSC and FTIR tests were used to investigate the effect of PG-FA and PG-A on the ROP of P-DDM; DMA, FTIR and TGA were performed to study their effects on the hydrogen bonds and thermal property of the cured P-DDM (PP-DDM). The results indicate that the ROP temperature of P-DDM remarkably decreased with the incorporation of PG-FA and PG-A. FTIR and DMA results illustrate that the total amounts of hydrogen bonds in PP-DDM increased with the addition of PG-FA or PG-A; however, its fraction of –OH⋯N (intra) and O−⋯+HN (intra) hydrogen bonds decreased. The decrease in –OH⋯N hydrogen bonds made the cross-linked density of polybenzoxazine increase, resulting in that the thermal stability of PP-DDM enhanced with the introduction of PG-FA and PG-A. [ABSTRACT FROM AUTHOR]

In the present study, hybrid organic–inorganic composites were fabricated from epoxy–TEOS (tetraethyl orthosilicate, Si(OC2H5)4) with various ratios (0–10 wt%) of multiwall carbon nanotubes (MWCNTs) as reinforcing nanofillers by the sol–gel method. The effect of the MWCNTs ratios on the structural, optical and mechanical characteristics and the thermal conductivity of the epoxy–TEOS/MWCNTs composites is investigated. The X-ray diffraction (XRD) analysis reveals that the pure epoxy-TEOS is amorphous, while epoxy–TEOS/MWCNTs composites are crystalline with an orthorhombic crystal structure that has an average crystallite size of 3.9 ± 0.15 nm. In addition, thermal stability and thermal conductivity were improved by adding TEOS and MWCNTs, whereas the exothermic peak temperature decreases compared with pure epoxy-TEOS. Similarly, the hardness Shore-D and tensile strength reach the optimum value at 4 wt% MWCNTs content. The significant improvement in the mechanical and thermal properties of the prepared composites could be attributed to the synergistic effect of MWCNTs and epoxy–TEOS which was emphasized by Fourier transform infrared (FTIR) spectroscopy. Moreover, epoxy-TEOS sample has high optical transmittance (T) within the visible region, but the composites samples are transparent at λ < 800 nm and have a lower value of T. The indirect optical band gap decreases from 3.59 to 2.91 eV with an increase in MWCNTs fractions from 0 to 10 wt%, respectively. However, the glass transition reflects the onset of decomposition temperatures was also considerably increased. The acquired outcomes such as a large increase in thermal conductivity and tensile stress coupled with reduced T make the composites readily applicable for a variety of applications. [ABSTRACT FROM AUTHOR]

Hybrid resin from polyurethane-/polysiloxane-modified epoxy (PPME) has been synthesized by using palm oil-based polyol as the polyurethane component. The palm oil-based polyol used are glycerol monooleate, polyethylene glycol monooleate, 1,4-butanediol monooleate and 1,4-butanediol,9-hydroxy-10-methoxy-monostearate. These polyols have a different chemical structure with each other. Here, we studied the influence of palm oil-based polyol structure on the mechanical and thermal properties of hybrid resin from PPME. Characterization of palm oil-based polyols structure was conducted by analysis FTIR and NMR. The qualitative analysis of palm oil-based polyols was carried out by determining acid value, ester value, iod value and hydroxyl value. The mechanical properties showed that PPME hybrid resin from 1,4-butanediol,9-hydroxy-10-methoxy-monostearate has the highest mechanical properties, while the thermal properties of hybrid resin showed that there is no significant influence of the polyols structure, but all of the PPME hybrid resins have higher thermal properties than unmodified epoxy. Nevertheless, the thermal degradation of PPME hybrid resin from 1,4-butanediol,9-hydroxy-10-methoxy-monostearate at 400–450 °C has the highest residual weight. It means that it shows the highest thermal stability. [ABSTRACT FROM AUTHOR]

Magnetic Fe2O3 nanopowder was synthesized and characterized by various analytical techniques. The PVA/Fe2O3 nanocomposites were prepared by solution casting method to investigate the effect of nanofillers on their physicochemical properties. The analytical tools such as FTIR, UV–visible spectra and XRD were used to analyze the structure of Fe2O3 nanopowder and PVA/Fe2O3 nanocomposites. The uniform distribution of the Fe2O3 nanofillers on the PVA matrix was inspected using SEM. The particle size of the crystalline Fe2O3 nanofillers was observed to be less than 30 nm from the TEM micrographs. The optical characteristics of the prepared samples were investigated by analyzing their UV–visible spectra. The bandgap of PVA nanocomposites was lower than for pure PVA due to the dispersed Fe2O3 nanofillers in the PVA matrix. The thermal properties of pristine PVA and PVA/Fe2O3 nanocomposites were investigated by TGA. The PVA/Fe2O3 nanocomposite systems exhibited the improved thermal stability. The thermal degradation mechanism of PVA/Fe2O3 nanocomposite system was inspected in depth at five different heating rates under non-isothermal conditions. The electrical and mechanical properties of PVA were enhanced remarkably while increasing the % weight loading of nanopowder. [ABSTRACT FROM AUTHOR]

An energetic triblock copolymer PPG–PGN–PPG (Mn = 1886 g mol−1) was synthesized for the first time by cationic ring-opening polymerization of propylene oxide with low molecular weight poly glycidyl nitrate (PGN) (Mn = 1061 g mol−1) as a macroinitiator, in the presence of boron trifluoride etherate (BF3·OEt2) as the catalyst. The product obtained in high yield was characterized by FTIR, gel permeation chromatography and 1H and 13C NMR spectroscopy. The thermal properties of the triblock copolymer were characterized by differential scanning calorimeter (DSC). The result approved that the glass transition temperature of the triblock copolymer (Tg = − 58 °C) is lower than PGN (Tg = − 35 °C); also, it was more stable than that of PGN. The effect of heating rates (10, 20, 30 and 40 °C min−1) on the decomposition of the copolymer was evaluated. The decomposition temperature of this compound increased as the heating rate increased. The kinetic parameters such as activation energy and frequency factor for the thermal decomposition of the triblock copolymer were obtained from the DSC and DTG data by non-isothermal methods proposed by the ASTM E696, Flynn–Wall–Ozawa (FWO) and Kissinger methods. The values by the FWO method are in good agreement with ASTM and Kissinger methods. [ABSTRACT FROM AUTHOR]

This work presents a unique type of hybrid composite which shows a significant improvement in mechanical and thermal properties than that of its pristine form of filler. The acid functionalization of carbon black and its use as filler in acrylonitrile butadiene styrene (ABS)/polyaniline (PANI) blend have resulted in promising improvement in mechanical and thermal properties. With the acid-functionalized carbon black when used as filler in the same blend with a compatibilizer (nanoclay), the blend exhibits further enhancement in tensile strength, modulus and thermal stability of the composite. Finally, with a good compatibilization using nanoclay (NC), the hybrid composite have shown 58% improvement in tensile strength and improvement in thermal decomposition temperature by around 70 °C. In addition, NC assisted for the transformation of unstable interaction between ABS and PANI to more stable configuration by assisting PANI to homogeneously incorporate to the polymer matrix, thereby increases the degradation onset temperature in TGA, up to 460 °C. [ABSTRACT FROM AUTHOR]

In our previous study, SEBS was first grafted by using maleic anhydride (MA) to form SEBS-g-MA, and it was then modified by ethanolamine (EA), which was noted as EA modified SEBS-g-MA. In this study, the EA modified SEBS-g-MA was compounded with tetraethyl orthosilicate (TEOS) using the sol–gel method to form EA modified SEBS-g-MA/silica composites. The chemical structures, mechanical properties and thermal stability of the EA modified SEBS-g-MA/silica composites were characterized. SEBS-g-MA modified with EA formed imide structures with hydroxyl group. After EA modified SEBS-g-MA reacted with TEOS, the absorption peak of Si–O–Si structure was observed in the EA modified SEBS-g-MA modified SEBS/silica composites. From solid-state NMR, the structures of silica in the EA modified SEBS-g-MA/silica composites were mainly in the forms of networks made of Si bonding with three or four –O–Si groups. In TGA, the thermal stability of the EA modified SEBS-g-MA/silica was better than that of SEBS. The storage modulus and Tg of the EA modified SEBS-g-MA/silica composites were enhanced. The tensile strength and Young's modulus of EA modified SEBS-g-MA/silica was improved. [ABSTRACT FROM AUTHOR]

In the present study, it was focused on developing mechanically stronger and thermally more stable polyvinyl chloride (PVC) composites by using green reduced graphene oxide (GRGO) filler to strengthen the negative features of PVC. For this purpose, GRGO reduced by vitamin C (ascorbic acid) with antibacterial properties was selected as filler. The PVC/GRGO composites were produced via colloidal blending method at different amounts of GRGO in PVC matrix (0.1, 0.3, 0.5 and 1% by weight), while pure PVC was also produced for comparison. The XRD and FTIR results showed that GRGO incorporated in the polymer matrix; this finding was also evident in SEM analysis. TGA and DSC analyses showed that the composite with 1% loading content of GRGO provided an important improvement on the thermal stability. The tensile strength and hardness of the composite having 0.1% GRGO increased by 42% and 98%, respectively. SEM image of PVC/GRGO-0.1 composite showed the galleries of GRGO filled with PVC. As a consequence, thermal and mechanical properties of PVC can be altered by changing loading content of GRGO. Moreover, the GRGO may be a good candidate for substitution of harmful fillers for PVC-based products. [ABSTRACT FROM AUTHOR]

In the present study, carbon nanotubes (CNTs)–silver nanoparticles (AgNPs)-co-doped polylactic acid (PLA) nanocomposites were prepared through two-solvent-assisted method. The morphology and structure of the prepared nanocomposites were characterized, and the thermal, mechanical and antibacterial properties of the nanocomposites were tested afterward. The results indicated that the CNTs and AgNPs were well dispersed within the PLA matrix, in which the CNTs and AgNPs attached with each other. The incorporation of these two reinforcement fillers significantly enhanced the thermal stability of the PLA. Due to strong intermolecular interactions, the CNTs and AgNPs improved the tensile strength of the PLA. Additionally, the prepared nanocomposites showed promising antibacterial effect on staphylococcus haemolyticus due to the existence of AgNPs. Having improved thermal and mechanical properties, as well as antibacterial capability, the prepared PLA nanocomposites have the application potential in packaging areas. [ABSTRACT FROM AUTHOR]

Herein, the effect of polyhedral oligomeric silsesquioxane (POSS) on compatibility, crystallization and thermal stability of polylactic acid (PLA)/polycaprolactone (PCL) blends was investigated. Scanning electron microscopy results revealed that the blend morphology became finer and much more uniform once lower contents of POSS were used. However, the compatibility level was notably reduced once the nanoparticle content increased which was attributed to the lower dispersion quality of POSS at higher concentrations. Differential scanning calorimetry results showed that lower contents of POSS suppressed the solution crystallization of PLA component due to the enhanced interactions between PLA and PCL as a result of the improved compatibility. However, at higher POSS contents, nanoparticles' nucleating effect became dominative leading to a higher degree of crystallinity. Thermogravimetric analysis showed that lower contents of POSS (1 and 2 wt%) greatly improved the thermal stability of the blend. Apart from the heat shielding role of POSS, the higher level of compatibility and, thus, more interactions between PLA and PCL were also responsible for the improved thermal stability since PCL is much more thermally stable than PLA. In conclusion, the nanoparticle-induced blend compatibility could impose positive and negative influences on different properties of PLA/PCL systems, which needs to be further investigated. [ABSTRACT FROM AUTHOR]

Polymer nanocomposite based on layered structure such as graphene, MoS2, MoO3 and WS2 has become an active field of research due to their exceptional thermal, mechanical and electrical properties. Achieving uniform dispersion of layered nanostructures within the polymer matrix is challenging because of the agglomeration of nanostructures which occurs due to the Van der Waals attraction and the cohesive nature between the two phases. In this work, we report the preparation of PVDF-modified MoS2 nanocomposites by the solvent blending method. The XRD results reveal the interaction of the negatively charged surface of MoS2 sheets and the positive CH2 group of PVDF through the predomination of β-phase. Morphological observation through SEM suggests the MoS2 induced formation of nanofibres in the composite. Enhancement in the thermal stability of the nanocomposite is observed and is possibly due to the heat barrier by the exfoliated MoS2 which in turn supports the tortuous effect. The DSC of the PVDF-modified MoS2 composite indicates the domination of β-phase and the hindrance to crystallization of PVDF. Improvement in the mechanical strength of the composites was also noticed on higher filler concentration. [ABSTRACT FROM AUTHOR]

The present paper describes the novel aliphatic polyamide 6 (PA6) copolyamides by the melt polymerization reaction of our newly synthesized aliphatic diamine monomer: N1,N6-Bis-(2-aminoethyl)adipamide (BAEA). The BAEA/CHDA (1,4-cyclohexanedicarboxylic acid) salt was prepared by pertinent long-chain polyamide with the cycloaliphatic ring and isolated as white solid, utterly characterized for the first time. The chemical structure of BAEA, BAEA/CHDA salt and copolyamides (PA6-BAEA/CHDA) was identified by 1H NMR and FT-IR spectroscopy. Depending on the chemical compositions, the viscosity and molecular weight of the copolyamides were in the range of 19,447–13,536 g mol−1 and 2.74–2.2 dL g−1. With increasing BAEA/CHDA salt molar ratio in the synthesized copolyamides, their melting temperatures (Tm) decreased from 212.7 to 170.4 °C, and the glass transition temperatures (Tg) increased from 60 to 89.4 °C. Besides, the as-synthesized all copolyamides possess nearly similar thermal stability (Td-50% = 439.59 − 443.38 °C) as neat PA6. Mechanical testing data revealed that with an increase in a proportion of BAEA/CHDA salt, Young's modulus of copolyamides is increased from 698.54 to 1093.89 MPa, while the tensile strength is increased by 8.1%. [ABSTRACT FROM AUTHOR]

Polystyrene (PS) has low impact strength and also shows poor strain hardening. In this work, poly(styrene–butadiene–styrene) triblock copolymer (SBS) was solution- and melt-blended with PS in the presence of a free-radical polymerization initiator, dicumyl peroxide (DCP), to enhance PS's thermal stability, mechanical properties, impact resistance, and strain hardening. The solution-blended PS/SBS containing 0.1% DCP annealed at 180 °C showed strong strain hardening, but the melt-blended PS/SBS annealed at the same temperature and time showed poor strain hardening. The change in the blending temperature, DCP concentration, and PS-to-SBS ratio had minimal effect on the strain hardening of melt-blended PS/SBS. The tensile strength increased with an increase in the concentration of DCP up to 0.1%, and beyond that level, the tensile strength started decreasing. The impact resistance considerably improved with an increase in the SBS loading in the PS matrix, and the enhancement was more than double of the impact resistance shown by the neat PS. [ABSTRACT FROM AUTHOR]

Thermoplastic polyurethane elastomers (TPUs) containing aliphatic polycarbonate soft segments and hard segments formed by 1,1′-methanediylbis(4-isocyanatocyclohexane) or 1,6-diisocyanatohexane and a combination of two chain extenders, i.e., 2,2′-[sulfanediylbis(benzene-1,4-diyloxy)]diethanol and 3-hydroxy-2-(hydroxymethyl)-2-methylpropanoic acid (DMPA), were synthesized in a one-step catalyzed melt polyaddition process. The obtained colorless, transparent and high-molar-mass materials, which differ in the content of the soft segments (30 or 45 mol%) and DMPA (10 or 20 mol%), were subjected to a series of test. Their structure was examined by FTIR spectroscopy, and the thermal properties were studied using differential scanning calorimetry and thermogravimetry. Moreover, their Shore A/D hardness, tensile, adhesive and optical properties were determined.These modified by an ionic chain extender TPUs were characterized by generally enhanced transmittance (up to 92.7% at 800 nm), tensile strength (up to 49.3 MPa), hardness and adhesive strength, and decreased elongation at break with a slightly worsened thermal stability in comparison with the non-modified ones. [ABSTRACT FROM AUTHOR]

Polybenzoxazine (PBz)/BMI/reduced graphene oxide (rGO) nanocomposites were prepared by varying the weight percentage of rGO from 1 to 5 wt%. The exfoliated sheet morphology of rGO makes it well-dispersed in the PBz/BMI matrix. The curing process monitored by DSC analysis showed two exothermic curves. Of which one is due to the reaction between BMI and furan ring and the other due to ring-opening polymerization. The nanocomposites did not show any agglomeration even at higher loadings (5 wt%) of rGO nanofillers. The degree of dispersion of rGO nanofillers resulted in enhancement of mechanical and thermal properties of PBz/BMI/rGO nanocomposites. A very low percentage of the nanofillers of about 5 wt% could tremendously increase the thermal stability, storage modulus and dielectric properties of the nanocomposites. [ABSTRACT FROM AUTHOR]

A novel polymeric flame retardant, PBPP2, for polylactide (PLA) was synthesized via a two-step polymerization process. The flame retardancy of neat PLA and flame-retarded PLA films prepared via solution casting method with different PBPP2 ratios was then investigated. When only the 3 wt% PBPP2 was added to PLA, the limiting oxygen index was increased from 23 to 30%. Additionally, the required V-0 rating was achieved compared to neat PLA. It was also found that PBPP2 increases the maximum thermal decomposition temperature of PLA, indicating that 3 wt% of PBPP2 is sufficient to improve flame retardancy and thermal stability on PLA, simultaneously. From both the decrease in Tm and the increase in elongation for PLA with the 3 wt% addition of PBPP2, PBPP2 could be considered to also function as a plasticizer on PLA. [ABSTRACT FROM AUTHOR]

Oligoaniline (OANI) was prepared using chemical oxidative method using ascorbic acid as a dopant and ammonium persulfate as an oxidant. As-synthesized OANI was subjected for the preparation of various drug composites. All the synthesized compounds were characterized by FTIR, 1HNMR, TGA, GPC, etc. The thermal stability of the compounds was determined by TGA. The molecular weight was determined by GPC. Antibacterial studies of the synthesized compounds were investigated against four Gram-positive (Staphylococcus aureus MTCC 96, Streptococcus pyogenes MTCC 442, B. subtilis MTCC 441 and S. mutans MTCC 890) and four Gram-negative (Escherichia coli MTCC 443, Pseudomonas aeruginosa MTCC 1688, KL. pneumoniae MTCC 109 and S. typhi MTCC 98) bacteria based on their clinical and pharmacological importance. Some of the synthesized compounds showed excellent antibacterial activity as compared to individual bacterial activity of OANI and drugs to be used for preparation of composites. [ABSTRACT FROM AUTHOR]

The surface of sol-gel-synthesized nano-alumina (Al2O3) was modified by three types of silane coupling agents with different specific functionalities, namely 3-aminopropyltriethoxysilane (APTES), triethoxy(octyl)silane (OCTEOS) and bis[3-(triethoxysilyl)propyl]tetrasulfide (TESPT). The aim of the present study was to explore the effect of both unmodified and surface-modified nano-Al2O3 on the cure characteristics, mechanical properties, cross-link density and thermal stability of natural rubber (NR) nanocomposites. Results revealed that silane coupling agents were very effective to enhance maximum rheometric torque (R∞) and mechanical properties like modulus and tensile strength of nano-Al2O3-based NR nanocomposites. APTES offered higher value of cure rate index for NR compounds as compared to two other silane coupling agents. Among three silane coupling agents, TESPT provided highest improvement in the mechanical properties of NR/nano-Al2O3 composites. This might be explained by considering excellent improvement in the cross-link density of NR compounds in the presence of TESPT-treated nano-Al2O3. The incorporation of both TESPT- and OCTEOS-modified nano-Al2O3 into the NR matrix markedly improved the thermal stability of NR composites. Moreover, bi-functional silane TESPT not only increased the hydrophobicity of nano-Al2O3, but also improved the probability of sulfur cross-linking during cure process of NR compounds. [ABSTRACT FROM AUTHOR]

Three series of dichloride and dihydroxyl-terminated polysulfone telechelics (Cl-PES-Cl and HO-PES-OH, M = 2580-12,750 daltons) were prepared from bis(4-chlorophenyl) sulfone with bisphenol A, 4,4′-dihydroxydiphenyl ether and 4,4′-dihydroxybiphenyl. The glass transition temperatures and thermal stabilities of the 30 telechelics synthesized were evaluated as a function of molecular weights and the nature of the end groups. It was observed that the glass transition temperatures of lower molecular weighted dihydroxyl telechelics are higher, due to the capabilities of forming hydrogen bonds, than the corresponding dichloride telechelics. On the other hand, the increase in the glass transition temperatures was steeper with dichloride-terminated oligomers as compared to the corresponding dihydroxyl-terminated ones. In addition, dichloride telechelics manifest higher thermal stabilities than dihydroxyl-terminated oligomers. [ABSTRACT FROM AUTHOR]

In this study, modified wollastonite nanorods (MWNRs) as core and polystyrene (PS) as a shell [Core-shell nanorods (CSNRs)] was synthesized using atomized microemulsion technique. CSNRs were compounded with styrene butadiene rubber (SBR) on a two-roll mill and compressed into sheet form using compression moulding machine. The encapsulation of MWNRs into PS was confirmed by field emission scanning electron microscope (FE-SEM), transmission electron microscope, X-ray diffraction spectrophotometer (XRD) and Fourier transform infrared spectroscopy. CSNRs/SBR nanocomposites were also characterized by XRD, FE-SEM, differential scanning calorimetry, thermogravimetric analysis, universal testing machine and Mooney viscometer. Incorporation of CSNRs resulted in improvement in rheological, thermal and mechanical properties of the nanocomposites. FE-SEM images showed a perfect dispersion of the CSNRs in SBR matrix at <1 wt% loading. Thermal stability of CSNRs/SBR nanocomposites was also increased significantly by the addition of CSNRs. Graphical abstract: [ABSTRACT FROM AUTHOR]

The purpose of the present article is to modify the surface of nano-titanium dioxide (TiO) and to investigate the reinforcing effect of both unmodified and surface-modified nano-titanium dioxide (TiO) on the mechanical properties and thermal stability of natural rubber (NR) nanocomposites. Surface of nano-TiO is modified by polyethylene glycol (PEG) and polypropylene glycol (PPG). The effective surface modification of nano-TiO is evaluated by Fourier transform infrared (FTIR) spectra and field emission scanning electron microscopy (FESEM). The result notifies that the final properties of NR nanocomposites are dramatically improved in the presence of surface-modified nano-TiO in comparison to unmodified nano-TiO. The excellent reinforcing capability of surface-modified nano-TiO is due to its better hydrophobicity and uniform dispersion within the NR matrix, as confirmed from morphological analysis. Furthermore, due to its small size PEG is better surface modifier for nano-TiO than PPG. [ABSTRACT FROM AUTHOR]

Novel X-type polyester 5 containing 5-nitro-2,4-dioxybenzylidenecyanoacetate groups as nonlinear optical (NLO) chromophores, which constitute parts of the polymer backbone, was prepared and characterized. Polyester 5 is soluble in common organic solvents such as N, N-dimethylformamide and acetone. Polymer 5 shows a thermal stability up to 280 °C from thermogravimetric analysis with glass-transition temperature obtained from differential scanning calorimetry of near 116 °C. The second harmonic generation (SHG) coefficient ( d) of poled polymer film at the 1064 nm fundamental wavelength is 1.78 pm V. The dipole alignment exhibits a thermal stability even at 4 °C higher than glass-transition temperature ( T), and no significant SHG decay is observed below 120 °C due to the partial main-chain character of polymer structure, which is acceptable for NLO device applications. [ABSTRACT FROM AUTHOR]

The effects of allophane (ALL) as a synergistic agent on the flame retardancy and thermal stability of intumescent flame-retardant (IFR) polypropylene composites were studied by limiting oxygen index (LOI), UL-94 test, cone calorimeter test (CONE) and thermogravimetric analysis. The incorporation of ALL led to enhanced thermal stability, LOI value and UL-94 ratings. CONE tests indicated that heat release rate, peak rate of heat release, smoke production rate, total smoke production and mass loss values of PP/IFR/ALL sample were much lower than those of PP/IFR and pure PP samples. Fourier transform infrared spectrometry result proved the presence of silicoaluminophosphate which can act as a catalytic agent to enhance the oxidative dehydration crosslinking charring process. Scanning electron microscopy and Raman spectra observation demonstrated that ALL could promote forming homogenous and compact char layer. The mechanical properties of PP composites were also improved by the loading of ALL. [ABSTRACT FROM AUTHOR]

Thermal stability and thermal degradation kinetics of nanocomposites play an important role in many applications. In this study, nanocomposites based on poly (lactic acid) (PLA)/graphene containing 0.5 and 1 wt% were prepared via solution method. Functionalized graphene were prepared by acid treatment followed by grafting PLA on their surfaces. The functionalized graphene was characterized using fourier transform infrared spectroscopy (FTIR), Raman, elemental analysis, Fourier transform infrared attenuated total reflection (FTIR-ATR), Dynamic mechanical thermal analysis (DMTA) and thermogravimetry analysis (TGA). The results revealed a successful functionalization reaction. The morphology of nanocomposites was investigated by scanning electron microscopy (SEM). Thermal kinetics of samples was studied using TGA in multiple heating rates (5, 10, 20 and 30 °C/min). Flynn-Wall-Ozawa (FWO) and Vyazovkin (VYZ) methods were considered as isoconversional models. Although the assumptions of the applied models were different, there was a good agreement between the models and obtained activation energies. [ABSTRACT FROM AUTHOR]

Differences on physicochemical properties of poly(pentadecanolide) (PPDL) synthesized by enzymatic ring-opening polymerization at two different temperatures, 70 and 90 °C, using Novozyme 435 were assessed. PPDL synthesized at 90 °C presents lower molecular weight and crystallinity than the one prepared at 70 °C. It was detected by FTIR that PPDL synthesized at 90 °C presents a large amorphous phase with more terminal OH groups. A difference in the melting and crystallization behavior was detected by differential scanning calorimetry, where the melting of the PPDL synthesized at 90 °C presents multiple melting and crystallization events at lower temperature than those exhibit by PPDL synthesized at 70 °C which presents a well-defined single melting and crystallization event. The differences in melting and crystallization behavior are attributed to the presence of a larger amorphous phase in PPDL synthesized at 90 °C due to increased number of terminal OH groups that disrupt the crystalline structure. Thermal stability is also higher in PPDL synthesized at 70 °C since the onset of decomposition starts 50 °C above that observed in PPDL obtained at 70 °C. [ABSTRACT FROM AUTHOR]

Thermal stability and degradation kinetic of the polyimides containing pendent-substituted azobenzene units were investigated by thermogravimetric analysis in nitrogen at different heating rates. Freeman-Carroll, Coats-Redfern and Flynn-Wall-Ozawa methods were utilized to obtain the kinetic parameters (activation energy E, pre-exponential factor A and order of reaction n) or variation of activation energy with conversion degree from thermogravimetric and derivative thermogravimetric curves. The thermogravimetric analysis revealed that the decomposition of azopolyimides proceeds in three or four stages, regardless of heating rate. [ABSTRACT FROM AUTHOR]

Requirements for adequate permeability of polymeric materials to gases and vapors, good barrier and mechanical properties of polymers have boosted interest in developing new strategies to improve these properties. Research and development in polymeric materials coupled with appropriate filler, matrix-filler interaction and new formulation strategies to develop composites have potential applications in various types of packaging (agricultural produce, dried food, frozen food etc.). In this study, LDPE composites containing various types of fillers (zeolite TMAZ 7, nanoclay Cloisite 20A and precipitated calcium carbonate, CaCO) were prepared using extrusion/injection molding. The microstructural and morphological changes as well as mechanical features of samples were characterized by scanning electronic microscopy and by tensile tests. The thermal degradation of LDPE composites was studied using thermogravimetric analysis. Barrier properties (permeability, the diffusion and the solubility constant) in modified LDPE samples were determined. It is found that used minor clay concentration is already very effective for achievement of good morphology. In the presence of nanoparticles, at lower content, the value of oxygen permeability of LDPE decreases. Also, the results have revealed that the samples containing fillers have increased thermal stability in comparison to pure LDPE. [ABSTRACT FROM AUTHOR]

The effects of dicumyl peroxide/vinyltriethoxysilane treatment and nanoclay content were investigated for low-density polyethylene (LDPE)/clay nanocomposites. LDPE was treated with 0.1 phr of DCP with, respectively, 1 phr and 3 phr VTES (System A), and with 0.2 phr of DCP with the same amounts of VTES (System B), and then mixed with different contents (1, 3, and 5 wt%) of modified clay (Cloisite 15A). The morphology and extent of crosslinking, as well as the thermal, mechanical, and thermomechanical properties were studied. X-ray diffraction results of all the VTES-treated LDPE/clay nanocomposites showed an increase in interlayer spacing, which indicates that the polymer chains were intercalated between the clay layers. Transmission electron microscopy micrographs of System B showed some evidence of exfoliated clay layers, indicating that the system exhibited a mixed morphology. The clay-containing samples had better thermal stability than LDPE, but the thermal stability did not differ much for the two systems. VTES observably decreased the melting enthalpy of LDPE, while the presence of clay had little influence on this value. This is somewhat contrary to the gel content results that showed a decrease in the extent of crosslinking in the presence of and with increasing clay content. VTES/DCP treatment and the presence of clay observably changed the dynamic mechanical and tensile behaviour of the LDPE. [ABSTRACT FROM AUTHOR]

Preparation of new types of modified poly(ether-imide-urethane)s, P a-c and P a-c, with good thermal stability and improved solubility was investigated. Two new bis(ether-azide)s bearing benzoxazole or benzothiazole pendent groups were synthesized by treating 2-[3,5-bis(4-trimellitimido-phenoxy)-phenyl]benzoxazole ( 1), or 2-[3,5-bis(4-trimellitimido-phenoxy)-phenyl]benzothiazole ( 1) with ethyl chloroformate in the presence of triethylamine, and subsequent by a nucleophilic reaction with sodium azide, respectively. Two series of modified polymers with moderate inherent viscosities between 0.21 and 0.32 dL g were prepared from bis(ether-azide)s 2 and 2 with several aromatic diols in dry toluene under refluxing in the presence of 1,4-diazabicyclo[2.2.2]octane (DABCO, triethylenediamine) as a catalyst. The polycondensation reaction readily proceeded in desirable yields as one-pot reactions starting from 2 to 2 without the separate synthesis of the corresponding bis(ether-isocyanate)s. In addition, the corresponding unsubstituted poly(ether-imide-urethane)s, P a-c, were prepared under identical experimental conditions for comparative purposes. All of the resulted polymers were thoroughly characterized by spectroscopic methods and thermogravimetry. The solubilities of modified polymer in common organic solvents as well as their thermal stability were enhanced compared to these of the corresponding unmodified polymers. The glass transition temperature, 10 % weight loss temperature and char yields at 800 °C were, respectively, 13-28 °C, 19-32 °C and 3-7 % higher than those of the unmodified polymers. [ABSTRACT FROM AUTHOR]

Candida is a genus of yeast, and lipase B isolated from Candida antarctica (CALB) has been utilized as a biocatalyst for the synthesis of a variety of organic compounds including polyesters and polylactones. Among the various immobilization media reported in the literature, the porous acrylic resin utilized in Novozym-435 has been widely studied. Here, we report the enzyme recovery and reuse for the synthesis of poly(ε-caprolactone) in toluene at 70 °C for 4 h per cycle for up to 10 reaction cycles, which consistently resulted in polymers with a weight-average molecular weight, M, of ~50,000 g mol and a polydispersity index of ~1.4. In addition, the thermal properties of the resin particles used in Novozym-435, with and without the enzyme, were evaluated by TGA and DSC analysis. The effect of mechanical agitation on the enzyme stability, recovery, and reuse was also discussed. These results may have significance to enzymatic polymer synthesis as well as to the enzyme immobilization on acrylic resins and other matrices. [ABSTRACT FROM AUTHOR]

Melt blending of linear low density polyethylene (LLDPE) and polylactide (PLLA) was performed in an extrusion mixer with post extrusion blown film attachment with and without compatibilizer-grafted low density polyethylene maleic anhydride. The blend compositions were optimized for tensile properties as per ASTM D 882-91. Based on this, LLDPE 80 (80 wt% LLDPE & 20 wt% PLLA) and M-g-L 80/4 (80 wt% LLDPE, 20 wt% PLLA and 4 parts compatibilizer per hundred parts of resin) were found to be an optimum composition. FTIR reveals that the presence of compatibilizer shifts carbonyl peak hence some increase in interaction between LLDPE and PLLA. Morphological characteristics of the fracture surface of with and without compatibilizer blends were examined by scanning electron microscopy. It shows that use of compatibilizer enhances the dispersions of PLLA in LLDPE matrix. Thermogravimetric (TG) analysis of blends shows the M-g-L 80/4 blend has higher thermal stability among studied blends. The degradation study under different pH of soil compost gives that in alkaline condition and the presence of compatibilizer was favorable for degradation. This blend may be used for packaging application. [ABSTRACT FROM AUTHOR]

Biodegradable star-shaped PLLA-ESO copolymers were synthesized by the bulk copolymerization of l-lactide ( l-LA) and epoxidized soybean oil (ESO) with stannous octanoate as the catalyst. Effects of molar ratios of monomer to catalyst, and various amounts of ESO on copolymerization were studied. The resulting copolymers were characterized by FTIR, H NMR, GPC, etc., which confirmed the successful synthesis of star-shaped copolymers of l-LA and ESO. The thermal and mechanical properties of samples were also investigated by means of DSC, TGA and tensile testing. The results showed that the PLLA-ESO copolymers possed lower glass transition temperature, melting point, crystallinity, and maximum decomposition temperature than those of neat polylactide. Tensile testing demonstrated that PLLA-ESO copolymer had better ductility than linear PLLA. It was also found that the amount of catalyst almost had no influence on the weight average molecular weight of PLLA-ESO copolymers, but which could be controlled by variation of molar ratios of l-LA to ESO. [ABSTRACT FROM AUTHOR]