Improved thermal and mechanical properties of poly(butylene succinate) by polymer blending with a thermotropic liquid crystalline polyester

A novel polymer blending system consisting of poly(butylene succinate) (PBS) and a thermotropic liquid crystalline polyester [LCP: a poly(4‐hydroxybenzoate)‐based polymer] was investigated in the presence and absence of a polycarbodiimide (PCD) and/or 1,1′‐carbonyl biscaprolactam (CBC) as chain extenders. Although the LCP was immiscible with PBS, it formed elongated fibrous domains having an orientation in the flowing direction when an extensional flow was applied during the processing. Scanning electron micrograph (SEM) of the injection‐molded polymer blends supported the distribution of micro fibrils of LCP in the PBS matrix by which the efficient toughening was provided. These blend specimens showed highly improved mechanical properties along with retaining high dynamic storage‐moduli (E′) up to the melting temperature of PBS. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 39952.     

Toughening of poly(L‐lactide) by melt blending with rubbers

Poly(L ‐lactide) (PLA) was melt‐blended with four rubber components—ethylene–propylene copolymer, ethylene–acrylic rubber, acrylonitrile–butadiene rubber (NBR), and isoprene rubber (IR)—in an effort to toughen PLA. All the blend samples exhibited distinct phase separation. Amorphous PLA constituted a topologically continuous matrix in which the rubber particles were dispersed. According to Izod impact testing, toughening was achieved only when PLA was blended with NBR, which showed the smallest particle size in its blend samples. In agreement with the morphological analysis, the value of the interfacial tension between the PLA phase and the NBR phase was the lowest, and this suggested that rubber with a high polarity was more suitable for toughening PLA. Under the tensile stress conditions for NBR and IR blend samples, these rubbers displayed no crosslinking and showed a high ability to induce plastic deformation before the break as well as high elongation properties; this suggested that the intrinsic mobility of the rubber was important for the dissipation of the breaking energy. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Copolymerization and blending of poly(phthalazinone ether ketone)s to improve their melt processability

The melt processability of phthalazinone‐containing poly(aryl ether)s (PAEs) was improved through copolymerization and blending. Poly(phthalazinone ether ketone) (PPEK) copolymers containing phthalazinone and bisphenol‐A (BPA) moieties were synthesized through nucleophilic substitution polycondensation. The PPEK copolymers exhibited high glass transition temperatures, excellent thermooxidative properties, good mechanical properties and improved solubility, all of which can be tailored by changing the molar ratio of phthalazinone to bisphenol monomers. The rheological investigation indicated that the incorporation of the flexible BPA moiety into the main chain lowered the melt viscosity of the copolymers. To improve the melt processability further, polymer blends of a PPEK copolymer/polycarbonate (PC) were prepared. The results suggested that blending is an effective approach for improving the melt processability of phthalazinone‐containing PAEs. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 2575–2580, 2007     

Synthesis,optical, electrochemical,and thermal stability properties of poly(azomethine-urethane)s

In this study, the novel low band gap and thermally stable poly(azomethine-urethane)s (PAMUs) were synthesized to investigate aliphatic and aromatic group effects on some physical properties such as thermal stability, optical and electrochemical properties. For this reason, we firstly synthesized the new Schiff bases via condensation reaction of 5-nitrovanilin with aromatic and aliphatic diamines. Then, these monomers were converted to PAMUs derivatives by the step-polymerization reaction with aromatic and aliphatic diisocyanates. The structures of the compounds were confirmed by FT-IR, UV–vis, ¹H NMR, and ¹³C NMR techniques. The molecular weight distribution parameters of the compounds were determined by the size exclusion chromatography (SEC). The compounds were also characterized by solubility tests, TG–DTA, and DSC techniques. Cyclic voltammetry (CV) measurements were carried out and HOMO–LUMO energy levels and electrochemical band gaps (E^′g${E^{\prime }}_g$) were calculated from their absorption edges. Additionally, optical band gaps (E_g) were determined by using UV–vis spectra of the materials. Fluorescence measurements were carried out in THF, DMF, and DMSO solutions to determine the optimum concentrations and the maximal emission and excitation intensities.     

Strengthening of poly(butylene adipate-co-terephthalate) by melt blending with a liquid crystalline polymer

Poly(butylene adipate-co-terephthalate) (PBAT) is a soft biodegradable polymer with a low melting temperature. PBAT has been melt-blended with a liquid crystalline polymer (LCP) aiming at preparing a new biodegradable polymer blend with improved mechanical properties. The phase structure and crystalline morphologies of the PBAT/LCP blends were investigated using scanning electron microscopy (SEM), differential scanning calorimetry (DSC), small-angle X-ray scattering (SAXS), and transmission electron microscopy (TEM). It was found that the LCP domains are precisely dispersed in the PBAT matrix and that these domains act as the nuclei for PBAT crystallization. The nonisothermal crystallization temperature from the melt was dramatically shifted from 50°C to about 95°C by the addition of 20% LCP. In addition, the tensile modulus of the prepared blends increases gradually with increasing LCP content, indicating the excellent strengthening effects of LCP on the PBAT matrix. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Toughness enhancement of poly(lactic acid) by melt blending with natural rubber

Rubber toughened poly(lactic acid) (PLA) was prepared by blending with natural rubber (NR)‐based polymers. The blends contained 10 wt % of rubber and melt blended with a twin screw extruder. Enhancement of impact strength of PLA was primarily concernced. This study was focused on the effect of rubber polarity, rubber viscosity and molecular weight on mechanical properties of the blends. Three types of rubbers were used: NR, epoxidized natural rubber (ENR25 and ENR50), and natural rubber grafted with poly(methyl methacrylate) (NR‐g‐PMMA). Effect of viscosity and molecular weight of NR, rubber mastication with a two‐roll mill was investigated. It was found that all blends showed higher impact strength than PLA and NR became the best toughening agent. Viscosity and molecular weight of NR decreased with increasing number of mastication. Impact strength of PLA/NR blends increased after applying NR mastication due to appropriate particle size. DMTA and DSC characterization were determined as well. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Synthesis of high molecular weight poly(l-lactic acid) and poly(d-lactic acid) with improved thermal stability via melt/solid polycondensation catalyzed by biogenic creatinine

Stereoregular high polymers of poly(l-lactic acid) (PLLA) (M_w 1.2 × 10⁵, isotacticity 96.0%) and poly(d-lactic acid) (PDLA) (M_w 1.0 × 10⁵, isotacticity 98.6%) were successfully synthesized via melt/solid polycondensation (MP/SSP) using a biogenic catalyst creatinine (CR). The follow-up monitor of the polycondensation products with ¹³C NMR technique revealed that the polymerization of MP/SSP proceeded in a stereochemical controlled way throughout the whole process as evidenced by the constant high values of isotacticity (97.8–99.4%) of produced polymers. Thermogravimetric analysis demonstrated that the decomposition temperatures (T_d,init 324.3 °C, T_{d, 5%} 347.0 °C, T_{d, max} 400.2 °C) of PLLA synthesized with catalyst CR are over 100 °C above those of PLLA synthesized with catalyst SnCl₂·2H₂O.     

The effect of carbon nanotube on the physical properties of poly(butylene terephthalate) nanocomposite by simple melt blending

Polyester nanocomposites based on poly(butylene terephthalate) (PBT) and carbon nanotube (CNT) were prepared by simple melt blending using a twin‐screw extruder. There is significant dependence of the thermal, rheological, and mechanical properties of the PBT nanocomposites on the concentration and dispersion state of CNT. The storage and loss moduli of the PBT nanocomposites increased with increasing frequency, and this enhancing effect was more pronounced at lower frequency region. The nonterminal behavior for the PBT nanocomposites was attributed to the nanotube–nanotube or polymer–nanotube interactions, and the dominant nanotube–nanotube interactions at high CNT content resulted in the formation of the interconnected network‐like structures of CNT in the PBT nanocomposites. The incorporation of a small quantity of CNT into the PBT matrix can substantially improve the mechanical properties, the heat distortion temperature, and the thermal stability of the PBT nanocomposites. The unique character of CNT dispersed in the PBT matrix resulted in the physical barrier effect against the thermal decomposition, leading to the improvement in the thermal stability of the PBT nanocomposites. This study also provides a design guide of CNT‐reinforced PBT nanocomposites with a great potential for industrial uses. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Rubber toughening of poly(lactide) by blending and block copolymerization

Copolymers of L-lactide with 15 or more mole % D-lactide are amorphous, noncrystallizable hydrolytically degradable materials. These glassy materials are brittle in tension and bending. To make these materials suitable for use as load-bearing devices in biomedical applications, toughness has to be enhanced. This is effectively accomplished by introducing a separate degradable rubber phase in the amorphous matrix. Several approaches have been explored: solution blending and coprecipitation of trimethylene carbonate and ?-caprolactone rubbers and poly(lactide), preparation of ABA triblock copolymers and blending of ABA block copolymers with the amorphous poly(lactide) matrix. In all cases very tough materials could be prepared. These materials are easily processable by compression molding at relatively low temperatures.     

Synthesis and thermal characteristics of poly(thioarylene)s by thermal polymerization

Thermal polymerization of bis[4-(4-bromophenylthio)phenyl] disulfide (I), bis[4-(4-bromophenyloxy)phenyl] disulfide (II) and bis[(4-(4-bromophenylsulfony)phenyloxy)phenyl] disulfide (III) was carried out at 250°C in diphenyl ether. The resulting poly(thioarylene)s show high crystallinity and high thermal stability. The blends and copolymers of poly(thioarylene) were also prepared, whose thermal properties were investigated by DSC measurements.     

Enhanced crystallization of poly(lactide) stereocomplex by xylan propionate

The effect of xylan propionate (XylPr) as a novel biomass‐derived nucleating agent on the poly(lactide) sterecomplex was investigated. Addition of XylPr to an enantiomeric blend of poly(l ‐lactide) (PLLA) and poly(d ‐lactide) (PDLA) was performed in either the solution state or molten state. The solution blend of PLLA/PDLA with XylPr was prepared by mixing equal volumes of 1 wt% XylPr/PLLA and 1 wt% XylPr/PDLA solutions in chloroform and precipitating in methanol. The solution blend with XylPr showed shorter half‐time crystallization than the solution blend without XylPr in isothermal crystallization between 80 and 140 °C, although homocrystallization occurred. Enhanced stereocomplex crystallization in the solution blend with XylPr was observed at 180 °C, where no crystallization occurred in the solution blend without XylPr. Addition of XylPr to PLLA/PDLA blend in the molten state was performed at 240 °C. Thereafter, the melt blend of PLLA/PDLA with or without XylPr was either quenched in iced water or isothermally crystallized directly from the melt. Isothermal crystallization of the melt‐quenched blend with XylPr gave a similar result to the solution blend with XylPr. In contrast, the melt‐crystallized blend with XylPr formed only stereocomplex crystals after crystallization above 140 °C. Furthermore, the melt‐crystallized blend with XylPr showed a higher crystallinity index and melting temperature than the melt‐crystallized blend without XylPr. This shows that XylPr promotes stereocomplex crystallization only when the blend of PLLA/PDLA with XylPr is directly crystallized from the molten state just after blending. © 2016 Society of Chemical Industry     

Dispersion of nanoclays with poly(ethylene terephthalate) by melt blending and solid state polymerization

Melt intercalation of clay with poly(ethylene terephthalate; PET) was investigated in terms of PET chain mobilities, natures of clay modifiers, their affinities with PET, and nanocomposite solid state polymerization (SSP). Twin screw extrusion was used to melt blend PET resins with intrinsic viscosities of 0.48, 0.63, and 0.74 dL/g with organically modified Cloisite 10A, 15A, and 30B montmorillonite clays. Clay addition caused significant molecular weight reductions in the extruded PET nanocomposites. Rates of SSP decreased and crystallization rates increased in the presence of clay particles. Cloisite 15A blends showed no basal spacing changes, whereas the basal spacings of Cloisite 10A and Cloisite 30B nanocomposites increased after melt extrusion, indicating the presence of intercalated nanostructures. After SSP these nanocomposites also exhibited new lower angle X‐ray diffraction peaks, indicating further expansion of their basal spacings. Greatest changes were seen for nanocomposites prepared from the lowest molecular weight PET and Cloisite 30B, indicating its greater affinity with PET and that shorter more mobile PET chains were better able to enter its galleries and increase basal spacing. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Plastification of poly(vinyl chloride) by polymer blending

Blends of poly(vinyl chloride) (PVC) with different copolymers have been studied to obtain a plasticized PVC with improved properties and the absence of plasticizer migration. The copolymers used as plasticizers in the blends were acrylonitrile butadiene rubber, ethylene vinyl acetate (EVA), and ethylene-acrylic copolymer (E-Acry). Blends were studied with regard to their processing, miscibility, and mechanical properties, as a function of blend and copolymer composition. The results obtained were compared with those of equivalent compositions in the PVC/dioctyl phthalate (DOP) system. Better results than PVC/DOP were obtained for PVC/acrylonitrile butadiene rubber blends. The plasticizing effect on PVC of EVA and E-Acry copolymers was similar to that of DOP. It is shown that crosslinking PVC/E-Acry blends or increasing the vinyl acetate content in PVC/EVA blends, are alternatives that can increase the compatibility and mechanical properties of these blends. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 75: 1303–1312, 2000     

Thermal stability of poly(trimethylene terephthalate)

The first-order thermal degradation rates of poly(trimethylene terephthalate) [PTT] at 240-280 °C under non-oxidative conditions have been determined from the increase in allyl endgroups (¹H NMR) which closely match the rates determined from the decrease in molecular weight (intrinsic viscosity). Consequently, the predominant thermal degradation mechanism of PTT is consistent with concerted, electrocyclic oxo retro-ene chain cleavage under conditions pertinent to viable polymerization processes and efficient downstream extrusion and spinning into fiber. Although catalysts, additives and other reaction variables can influence the thermo-oxidative stability of polyesters including PTT, these factors have been found to have little or no effect on PTT thermal degradation rates under non-oxidative environments. The thermal stability of poly(butylene terephthalate) [PBT] has also been determined from butenyl endgroups (NMR) and molecular weight (IV). The activation energies (E_a) for both PTT and PBT thermal chain cleavage are similar to the reported E_as for poly(ethylene terephthalate) [PET] degradation, which is further supported by semi-empirical molecular orbital calculations on model compounds. However, both PTT and PBT undergo molecular weight decrease faster than PET. The apparent slower chain cleavage of PET is attributed to the contribution of productive chain propagation reactions due to unstable vinyl endgroups which alters the equilibrium stoichiometry compared to the relatively stable endgroups of PTT and PBT.     

Crystallization, spherulite growth, and structure of blends of crystalline and amorphous poly(lactide)s

The effects of incorporated amorphous poly(dl-lactide) (PDLLA) on the isothermal crystallization and spherulite growth of crystalline poly(l-lactide) (PLLA) and the structure of the PLLA/PDLLA blends were investigated in the crystallization temperature (T_c) range of 90-150 °C. The differential scanning calorimetry results indicated that PLLA and PDLLA were phase-separated during crystallization. The small-angle X-ray scattering results revealed that for T_c of 130 °C, the long period associated with the lamellae stacks and the mean lamellar thickness values of pure PLLA and PLLA/PDLLA blend films did not depend on the PDLLA content. This finding is indicative of the fact that the coexisting PDLLA should have been excluded from the PLLA lamellae and inter-lamella regions during crystallization. The decrease in the spherulite growth rate and the increase in the disorder of spherulite morphology with an increase in PDLLA content strongly suggest that the presence of a very small amount of PDLLA chains in PLLA-rich phase disturbed the diffusion of PLLA chains to the growth sites of crystallites and the lamella orientation. However, the wide-angle X-ray scattering analysis indicated that the crystalline form of PLLA remained unvaried in the presence of PDLLA.     

Preparation of the thermally stable conducting polymer PEDOT - Sulfonated poly(imide)

We describe the template polymerization of EDOT with sulfonated poly(amic acid) (SPAA), resulting in a stable conducting polymer aqueous dispersion, PEDOT-SPAA, with particle size ca. 63 nm. In films of PEDOT-SPAA, the sulfonated poly(amic acid) template undergoes imidization within 10 min at temperatures greater than 150 °C, resulting in PEDOT-sulfonated poly(imide) (PEDOT-SPI) with 10-fold conductivity enhancement. This material is highly thermally stable as compared to PEDOT-PSS. Thermal stability is necessary for many processing applications of conducting polymers, including annealing for OPVs and melt-processing of polycarbonate for device encasement. Isothermal TGA experiments were run at 300 °C for PEDOT-PSS and PEDOT-SPAA and we found that PEDOT-SPAA had a smaller slope for degradation. Annealing of films at 300 °C for 10 min caused the conductivity of PEDOT-PSS films to be unmeasurable (<1 × 10⁻⁵ S/cm), while those of PEDOT-SPAA increased 6-fold. Secondary doping of the PEDOT-SPAA system with additives commonly used for PEDOT-PSS was also investigated.     

Effect of polymer matrix on thermal stability of immobilised trypsin

Trypsin was markedly stabilised through immobilisation by radiation polymerisation of various monomers at low temperatures. A porous polymer matrix having a defined structure and flexibility enhanced the thermal stability. In highly hydrophilic monomer systems the resulting polymer matrix had a porous internal structure in which enzyme molecules were trapped. Trypsin was then protected from thermal denaturation and self-autolysis. In contrast, polymers formed from hydrophobic monomers were of particle form and enzyme molecules were only trapped on the surface. With high concentrations of up to 90% monomer, the resulting radiation-polymerised enzyme composites experienced limitations of substrate diffusion. There was an optimum hydrophilicity for enhancement of thermal stability of trypsin and this was found when the measured degree of hydration of the system was at a ratio of 0.35.     

聚酯热稳定性的研究

在合成聚酯试验之后,利用聚合试验装置搅拌器扭矩变化来表征聚酯加工过程中的热稳定性,比热失重法更接近聚酯加工过程,比粘度降法减少了干扰因素。研究结果表明:稳定剂种类、添加量和调配方式等均影响聚酯的热稳定性。