Application of Poly(acetic Acid)–Based Graft Copolymer as a Compatibilizer for Poly(L-lactic Acid)/Poly(butylenesuccinate) Blend System

Poly(L-lactic acid) (PLLA) was blended with poly(butylenesuccinate) (PBS) using a single-screw extruder to modify the poor characteristics of these polymers. Furthermore, when both polymers were blended, the graft copolymer that was synthesized by partially saponified poly(vinyl alcohol) (PSPVA) and ?-caprolactone (?-CL) was used as a novel compatibilizer. The structure of the synthesized compatibilizer was determined by ¹H or ¹³C NMR. From this result, the ring-opening polymerization of the ?-CL occurred at the hydroxyl group of PSPVA. The structures of the PLLA/PBS solvent-cast blended films could be observed via an optical microscope. From the optical microscopic observation, the structures of the solvent-cast blended films with the synthesized compatibilizer were more homogeneous than those of the solvent-cast blended films without the compatibilizer. The mechanical properties of the PLLA/PBS extruded blended films were determined by a tensile test. The result showed the tensile strength of the blended films with the synthesized compatibilizer was greater than that of the blended films without the compatibilizer.     

Synthesis,Characterization of Fulvic Acid–Poly(Methylmethacrylate) Graft Copolymers Based on Surface-Initiated Atom Transfer Radical Polymerization and its Effect on Performance of Poly(Lactic Acid)

Fulvic acid–poly(methylmethacrylate) graft copolymers were synthesized by surface-initiated atom transfer radical polymerization with fulvic acid. The result demonstrated that the hydrophobicity of fulvic acid–poly(methylmethacrylate) was improved after modification by surface-initiated atom transfer radical polymerization. Furthermore, poly(lactic acid)/fulvic acid–poly(methylmethacrylate) composites were prepared to improve the performances of poly(lactic acid) by blend melting. Compared to poly(lactic acid) with X_c of 5.38%, the X_c of poly(lactic acid)/fulvic acid–poly(methylmethacrylate) composites was 19.94%. Moreover, the impact strength of poly(lactic acid)/fulvic acid–poly(methylmethacrylate) composites was increased by 5.19% compared to poly(lactic acid). In all, this study provided an effective and feasible method for optimizing interface performance and enhancing the thermal stability of poly(lactic acid).     

A Hybrid Membrane of Poly(vinyl alcohol) and Phosphotungstic Acid for Fuel Cells

Proton conducting membranes composed of phosphotungstic acid (PWA) and poly(vinyl alcohol) (PVA) were prepared. Conductivity and Fourier transform infrared spectrometer(FTIR) measurements show that most of the acid embedded are stable in the PVA matrix when the membrane is immerged in water or methanol solution at room temperature. Conductivity of the composite membranes scatters around 10-3S·cm-1 at room temperature. The methanol crossover through the membranes is about an order of magnitude lower than that through Nafion 117 membrane.     

Preparation and Performance of Poly(Lactic Acid)-γ-Cyclodextrin Inclusion Complex-Poly(Lactic Acid) Multibranched Polymers by the Reactive Extrusion Process

The poly(lactic acid)-γ-cyclodextrin inclusion complex-poly(lactic acid) multibranched polymers were prepared by reactive extrusion process with L-lactide as raw material, stannous octoate as catalyst and the carboxyl poly(lactic acid)-γ-cyclodextrin inclusion compound as cores prepared by ultrasonic coprecipitation and carboxylation reaction. It was shown that the comprehensive performance of poly(lactic acid)-γ-cyclodextrin inclusion complex-poly(lactic acid) had been significantly improved compared with liner poly(lactic acid) by the study of structure and properties. Thus, the novel poly(lactic acid)-γ-cyclodextrin inclusion complex-poly(lactic acid) multibranched polymers have a potential use in biomedical materials. This study provided a simple and feasible preparation method for improving the performance of poly(lactic acid).     

Adhesion at Poly(Butylacrylate)–Poly(Dimethylsiloxane) Interfaces

We present an investigation of the adhesion modulation mechanisms of silica-like nanoparticles (MQ resins) incorporated in polydimethylsiloxane (PDMS) elastomers and acrylic adhesives. The Johnson-Kendall-Roberts (JKR) test has been used to gain information on the both zero velocity and the velocity dependence of the adhesive strength, avoiding as much as possible contributions to the adhesive strength of bulk dissipation in the adhesive (which is not the case with peel tests). As the incorporation of the MQ resins into the elastomers deeply affects their own mechanical properties, the loading and unloading curves of small poly(butylacrylate) (PBA) lenses on either PDMS elastomers, adsorbed PDMS and pure MQ resin layers are compared in a systematic manner. The PBA chains are observed to have a neat affinity for the MQ resin nanoparticles. When MQ resins are present at the interface, they tend to prevent facture propagation, thus producing a larger deformation of the PBA lens. The modulation of adhesion is then dominated by the corresponding dissipation inside the acrylic adhesive.     

Lipase Catalyzed Synthesis of Poly(ε-Caprolactone)−Poly(Dimethylsiloxane)−Poly(ε-Caprolactone) Triblock Copolymers

Immobilized lipase B from Candida antarctica was used to synthesize copolymers of poly(ε-caprolactone) (PCL) with α,ω-(dihydroxy alkyl) terminated poly(dimethylsiloxane) (PDMS). The reactions were carried out in toluene with a 1:2 w/v ratio of the monomers to solvent at 70 oC. The PCL−PDMS−PCL triblock copolymer composition was varied by changing the feed ratio of the reactants [CL]/[PDMS] (80:20; 60:40; 40:60; 20:80 w/w, respectively). The enzymatically synthesized copolymers were characterized by GPC, FTIR, TGA, DSC and XRD. The successful synthesis of the copolymers was confirmed by the appearance of a single peak in all of the respective GPC chromatograms. An increased feed ratio of [CL]/[PDMS] produced an increase in the number-average molecular weight (M_n) of the copolymers from 4,400 g mol⁻¹ (20:80 w/w of [CL]/[PDMS]) to 13,950 g mol⁻¹ (80:20 w/w of [CL]/[PDMS]). The copolymers were shown by DSC and XRD to be semi-crystalline and the degree of crystallinity increased with an increase in the [CL]/[PDMS] feed ratio. The crystal structure in the copolymers was analogous to that of the PCL homopolymer. In enzymatic polymerization the recovery and reuse of the enzyme is highly desirable. When the lipase was recovered and reused for the copolymerization, higher molecular weight copolymers were obtained upon a second use. This appears to be due to an increased activity of the immobilized lipase following an opening up of the acrylic resin matrix in the organic medium. This improvement was not maintained for subsequent recycling of the lipase principally due to the disintegration of the acrylic resin matrix.     

β-cyclodextrin as a Partial Replacement of Phosphorus Flame Retardant for Poly(Lactic Acid)/Poly(Methyl Methacrylate): A More Environmental Friendly Flame-Retarded Blends

β-Cyclodextrin was used together with isopropylated triaryl phosphate ester flame retardant to improve the flame resistance of poly(lactic acid)/poly(methyl methacrylate). Poly(lactic acid)/poly(methyl methacrylate)/flame-retardant blend (with and without β-cyclodextrin) was evaluated using limiting oxygen index, Underwriters Laboratories-94 vertical burning test, scanning electron microscopy, and thermogravimetric analysis (in O₂ and N₂). The addition of β-cyclodextrin was able to reduce the amount of flame retardant required for poly(lactic acid)/poly(methyl methacrylate) blends to achieve self-extinguishing properties. The poly(lactic acid)/poly(methyl methacrylate)20/flame-retardant/β-cyclodextrin blends achieved Underwriters Laboratories-94, V-0, and limiting oxygen index value of 29.3%. A compact and wide coverage of char layer was formed on the burning surface of poly(lactic acid)/poly(methyl methacrylate)20/flame-retardant/β-cyclodextrin blends.     

Synthesis and Characterization of Poly(Ethyleneimine)-Modified Poly(Acrylic Acid)-Grafted Nanocellulose/Nanobentonite Superabsorbent Hydrogel for the Selective Recovery of β-Casein From Aqueous Solutions

A novel adsorbent, poly(ethyleneimine)-modified poly(acrylic acid)-grafted nanocellulose/nanobentonite superabsorbent hydrogel (PEI-PAA-g-NC/NB) was prepared by free radical graft copolymerization technique and well characterized. Swelling behavior of adsorbent was studied under different pH and temperatures. The various adsorption parameters for the adsorption of the protein, β-Casein (βCN) onto the PEI-PAA-g-NC/NB were investigated. Sips adsorption isotherm and pseudo-first-order kinetic model were best suited for the present adsorbent. The adsorption-desorption experiments were conducted with 0.1 M NaSCN for four cycles. The results of the present investigation proved that PEI-PAA-g-NC/NB is highly effective for the separation of βCN from aqueous solutions.     

Preparation and Properties of Biodegradable Shape Memory Polylactic Acid/Poly(ε-caprolactone) Blends under Volume Elongational Deformation

In this work, a novel eccentric rotor mixer (ERM), which can generate circulating volume elongational deformation, is employed to prepare biodegradable polylactic acid (PLA)/poly(ε-caprolactone) (PCL) thermo-responsive shape-memory blends without a compatibilizer. The results of scanning electron microscopy (SEM) show that the ERM has more efficient dispersion and compatibilization for blends than conventional Banbury mixers, which is beneficial for shape-memory performance. The results of Fourier transform infrared (FTIR) and differential scanning calorimetry (DSC) also confirm the consequences. Then, morphological and mechanical properties and shape memory behaviors of the blends are investigated in detail. Co-continuous morphology is found on EF-PLA50. The blends exhibit remarkable shape-memory performance. The bending shape fixing ratio and recovery ratio of the blends are more than 94% and are still more than 90% after five shape memory cycles. With the increase of PLA content, the shape fixing ratio of blends decreases, while the shape recovery ratio increases and the shape recovery time becomes shorter. All the blends show good mechanical properties.     

Separation of Acetic Acid/Water Mixtures by Pervaporation through Poly(Vinyl Alcohol)–Sodium Alginate Blend Membranes

Abstract

Dense pervaporation (PV) membranes were prepared by blending hydrophilic polymers, poly(vinyl alcohol) (PVA), and sodium alginate (SA), which were then crosslinked with glutaraldehyde (GA) for the separation of acetic acid/water mixtures. These membranes (PVA‐SA) were characterized for morphology, intermolecular interactions, thermal stability, and physico‐mechanical properties using XRD, FTIR, TGA and tensile testing respectively. The effect of experimental parameters such as feed composition and permeate pressure on separation performance of the crosslinked membranes was determined. Sorption studies and porosity measurement were carried out to evaluate the extent of interaction and degree of swelling of the polyion membranes, in acetic acid and water as well as in mixtures of acetic acid and water. Further the results were compared with the commercial membrane (Sulzer pervap 2205). The membrane appears to have a good potential for dehydrating 90 wt% acetic acid with a reasonably high selectivity of 21.5 and a substantial water flux of 0.24 kg/m²/h/10 µm. Separation factor was found to improve with decreasing feed water concentration whereas the corresponding flux decreased. Higher permeate pressures caused a reduction in both flux and selectivity.     

Structure and Performance of Poly(vinyl alcohol)/Poly(γ-benzyl L-glutamate) Blend Membranes

Poly(vinyl alcohol) (PVA)/poly(γ-benzyl L-glutamate) (PBLG) blend membranes with different PBLG wt contents were prepared by pervaporation. Structure and surface morphologies of PVA/PBLG blend membranes were investigated by Fourier transform infrared spectroscopy (FT-IR) and scanning electron microscopy (SEM). Thermal, mechanical, and chemical properties of PVA/PBLG blend membrane were studied by differential scanning calorimeter (DSC), tensile strength tests, and other physical methods. It was revealed that the introduction of PBLG homopolymer into PVA could exert an outstanding effect on the properties of PVA membrane.     

Encapsulated Zosteric Acid Embedded in Poly[3-hydroxyalkanoate] Coatings—Protection against Biofouling

Summary The natural, non-toxic antifouling compound zosteric acid (ZA, p-coumaric acid sulfate) was encapsulated in polystyrene (PS) microcapsules (30 mg ZA /1 g PS) with an efficiency of 30 % via an in-liquid drying process. Electron micrographs showed microcapsules with smooth surfaces and a mean diameter of 200 m. The FIB method was used to cross-section a microcapsule in order to visualize the inner capsule structure and to localize ZA via element analysis. Coatings of a biocompatible polyester, poly[3-hydroxyalkanoate-co-3-hydroxyalkenoate] (PHAE), were prepared on microscopic slides. These coatings contained dispersed ZA (PHAE/ZA) or ZA-loaded PS microcapsules (PHAE/PS(ZA)). The release of ZA was monitored via conductivy measurements in water and was 4 gcm^-2d^-1 for PHAE/ZA and 0.9 gcm^-2d^-1 for PHAE/PS(ZA) coatings. To follow the initial steps of biofilm formation, coated slides were exposed to activated sludge and analyzed for cell adhesion with ESEM. ZA was effective during the burst release time of the PHAE/ZA coating, but no significant differences in biofouling were observed after 48 h. This was attributed to the minimal effective release rate of ZA, which is approximately 10 gcm^-2d^-1.     

Optimization of Propionic Acid Feeding for Production of Poly(3-hydroxybutyrate-co-3-hydroxyvalerate) in Fed-Batch Culture of Ralstonia eutropha

The feeding method of propionic acid for production of poly(3-hydroxybutyrate-co-3-hydro xyvalerate) [P(3HB-co-3HV)] by fed-batch culture of Ralstonia eutropha was optimized to achieve high cell density and high 3HV yield. Effects of different feeding strategies of propionic acid on the production of P(3HB-co-3HV) were investigated. A decline of specific synthesis rate of copolymer and the yield of 3HV unit from propionic acid were observed due to the propionic acid accumulation in culture broth when the feeding solution with high P/G(propionic acid to glucose) ratio was employed. It was further confirmed by controlling propionic acid concentration at a low level in the separate feeding of propionic acid. An optimal feeding strategy was demonstrated to reduce the propionic acid accumulation. The cell concentration, P(3HB-co-3HV) productivity and 3HV unit fraction reached to 163.9kg.m-3, 1.8kg.m-3.h-1, and 10.6%(by mass), respectively, resulting in a yield of 0.33g HV per g propionic acid.     

Poly(Vinylpyrrolidone)-Embedded Bismuth Ferrite—Poly(Vinylidene Fluoride-co-Hexafluoropropylene) Composites with Enhanced Dielectric Properties

The dielectric properties of poly(vinylpyrrolidone) (PVP)-modified bismuth ferrite (BFO) particles in the poly(vinylidene fluoride-co-hexafluoropropylene) (P(VDF-HFP) matrix were prepared through solution casting techniques. The composites showed enhanced dielectric constant (90) and reduced dielectric loss (<0.5) at 40?wt% of PVP-modified BFO particles. The dielectric constant of the resultant composites with PVP-modified BFO was much higher as compared to that of unmodified BFO-P(VDF-HFP) composites. The maximum remnant polarization reached (2Pr?～?1.12?µC?cm^?2) in the PVP-modified BFO-P(VDF-HFP) composites. The demonstrated approach might provide a route for using PVP-modified BFO particles to enhance the dielectric and ferroelectric performance of the composites.     

Kinetics of Phase Separation in Poly(ɛ-caprolactone)/Poly(ethylene glycol) Blends

The poly(ɛ-caprolactone)/poly(ethylene glycol) (PCL/PEG) blends reveal a miscibility window of upper critical solution temperature (UCST) character. The kinetics of liquid–liquid phase separation (LLPS) for the blends of PCL/PEG is investigated by time-resolved small angle light scattering (TRSALS). The time evolution of scattering profile is analyzed by linear Cahn–Hilliard theory for early stage of spinodal decomposition (SD). The evolution of the maximum intensity I_m(t) and the corresponding wavenumber q_m(t) obey the power-law scheme (I_m(t)∼t^β and q_m(t)∼t^−α). A relation of β=3α in late stage is obtained almost the same scaling exponents with β≅1 and α≅1/3 for various quenching depths. The α≅1/3 implied that a coarsening mechanism at the late stage of phase separation may proceed with Ostwald ripening or Brownian coalescence process. Besides, the intermediate and late stages of SD can be scaled into a universal from represented well by Furukawa’s structure factor. The percolation to cluster transition is accompanied with α∼0.13→1/3 from intermediate to late stage of SD for the off-critical mixture of PCL/PEG (4/6) blend. In this study, the experimental result demonstrates that the crystallization is a viable mechanism to lock phase-separated structure of the blends. The competition between phase separation and crystallization has been suggested to determine the final morphology.     

Surface Morphology and Properties of Poly(γ-benzyl L-glutamate)/Poly(butyl acrylate-co-methyl Methacrylate) Blend Film

Poly(γ-benzyl L-glutamate)/poly(butyl acrylate-co-methyl methacrylate) (PBLG/Poly(BA-co-MMA)) blend films were prepared by casting the polymer blend solution in dichloroethane. Surface morphology of the polymer blend film was investigated by scanning electron microscopy (SEM) and atomic force microscopy (AFM). Thermal and mechanical properties of the polymer blend film were studied using differential scanning calorimeter (DSC) and tensile tests. It was revealed that the introduction of Poly(BA-co-MMA) into PBLG could exert marked effects on the surface morphology and the properties of the PBLG film.     

Effects of Poly(ϵ-caprolactone) on Structure and Properties of Poly(lactic acid)/Poly(ϵ-caprolactone) Meltblown Nonwoven

To obtain flexile poly(lactic acid)-based melt-blown nonwoven filtration material, poly(lactic acid)/poly(?-caprolactone) melt-blown nonwoven with various components were melt-spun by melt-blown processing in the Melt-blown Experiment Line. The 3 wt.% tributyl citrate to poly(?-caprolactone) was added in the composites as compatibilizer. The effect of poly(?-caprolactone) on the structure, morphology, mechanical and filtration properties of poly(lactic acid)/poly(?-caprolactone) melt-blown nonwoven was reported. Scanning electron microscopy micrographs revealed good dispersion of the additive in the fiber webs. The crystallinity of melt-blown webs with poly(?-caprolactone) was more than that of poly(lactic acid) alone. The tensile strength, ductility and air permeability of poly(lactic acid) melt-blown nonwovens were enhanced significantly. The input of poly(?-caprolactone) increased the diameter of fibers and decreased the filtration efficiency of poly(lactic acid)/poly(?-caprolactone) melt-blown nonwoven.     

Surface Energy and Thermal Stability Studies of Poly(dimethyl siloxane)–Poly(alkyl(meth)acrylate) Copolymers

The correlation between the surface energy and thermal stability of polymers plays an important role in engineering of plastic materials. In this work, microstructural characteristics of copolymers of poly(dimethyl siloxane) with benzyl methacrylate, ethyl methacrylate, and methyl acrylate are correlated with their surface energy and thermal stability. The poly(dimethyl siloxane) segments in the copolymer chains affected the hydrophobic behavior. The surface energy of the synthesized copolymers decreased by increasing segments of alkyl methacrylates. The thermal stability of copolymers suggesting that heat resistance of poly(dimethyl siloxane) copolymers used in this correlation can be improved by adjusting the units of alkyl methacrylates in copolymers.     

Gaseous Products formed by γ-Irradiation of Poly(l,4-Butylene Terephthalate), Poly(Ethy1ene Terephthalate) and Poly(Ethy1ene 2,6-Naphthalenedicarboxylate)

Summary A comparative investigation of gaseous products formed by γ-irradiation of poly( 1,4-butylene terephthalate), PBT; poly(ethylene terephthalate), PET; and poly(ethylene 2,6-naphthalene-dicarboxylate), PEN has been performed. These polyesters were irradiated under vacuum at doses from 0.5 to 4 MGy. The gases formed were analyzed by gas chromatography – mass spectrometry, and their radiation-chemical yields (G) were calculated. Hydrogen, carbon monoxide and carbon dioxide, as the main products, and methane of low quantity were found after radiolysis of all polyesters studied. Other hydrocarbons such as ethane, propane, propene and n-butane were also detected in gases mixture resulted from irradiation of PBT. Traces of ethane were also registered in the radiolysis products of PET. Irradiation of PEN did not lead to formation of hydrocarbons other than methane. The total G values and compositions of the formed gaseous mixtures depended on chemical structure of the irradiated polyesters. Mechanism of gaseous products formation has been discussed. Received: 17 October 2002/Revised version: 5 February 2003/Accepted: 6 February 2003 RID="*" Correspondence to Roustam Aliev     

Studies on the Sorption of Palladium using Cross‐Linked Poly (4‐Vinylpyridine‐Divinylbenzene) Resins in Nitric Acid Medium

Various cross‐linked (4, 8, and 12%) gel‐type weak‐base poly(4‐vinylpyridine) (PVP) resins were studied for palladium recovery from nitric acid medium. The sorption of palladium was found to decrease with an increase in cross‐linkage of the resin. 8 and 12% PVP resins exhibited maximum D _Pd(II) values at 2–6 M HNO₃, whereas 4% PVP resin showed maximum D _Pd(II) values at lower acidities (0.1 M HNO₃). FT‐IR, SEM, and XPS techniques were used for the characterization of palladium‐loaded resins. Detailed studies were carried out with the resin of modest cross‐linkage i.e., 8% PVP resin. The sorption isotherm studies revealed that the maximum palladium loading approaches the theoretical capacity of the resin, presuming the sorption of palladium as divalent anion at 4 M HNO₃. The pseudo‐second order kinetics model yielded the best fit for the experimental data of sorption kinetics. An increase in temperature accelerates the rate of palladium extraction and also the addition of chloride ions increases the palladium uptake. Column studies were performed using 4 and 8% PVP resins in 2 and 4 M nitric acid concentrations. The loaded palladium could be eluted efficiently with acidic thiourea solution.