Showing papers in "Polymer Bulletin in 2010"

Removal of Cu2+ and Pb2+ ions from aqueous solutions by starch-graft-acrylic acid/montmorillonite superabsorbent nanocomposite hydrogels

Abstract: In this study, the removal of copper(II) and lead(II) ions from aqueous solutions by Starch-graft-acrylic acid/montmorillonite (S-g-AA/MMT) nanocomposite hydrogels was investigated. For this purpose, various factors affecting the removal of heavy metal ions, such as treatment time with the solution, initial pH of the solution, initial metal ion concentration, and MMT content were investigated. The metal ion removal capacities of copolymers increased with increasing pH, and pH 4 was found to be the optimal pH value for maximum metal removal capacity. Adsorption data of the nanocomposite hydrogels were modeled by the pseudo-second-order kinetic equation in order to investigate heavy metal ions adsorption mechanism. The observed affinity order in competitive removal of heavy metals was found Cu2+ > Pb2+. The Freundlich equations were used to fit the equilibrium isotherms. The Freundlich adsorption law was applicable to be adsorption of metal ions onto nanocomposite hydrogel.

Comparative pyrolysis of polyolefins (PP and LDPE) and PET

Abstract: In the present study, thermal degradation of polyolefins (PP and LDPE) and PET in a tubular reactor in an inert atmosphere was conducted. Each polymer was subjected to pyrolysis at the temperatures of 673, 773, 873, and 973 K. Yields of tar, residual coke and gas, and conversion degrees were calculated. Tars which include valuable chemicals were characterized by GC–MS, 1H-NMR, FTIR, and GPC. Pyrolysis gases (C1 + C2, C3, C4, C5, and C6 + C7) were also analyzed by GC analysis. From the comparison of data, it can be said that pyrolysis of PP and LDPE leads to the formation of tar containing mainly paraffinic structures, while aromatic structures were produced by the pyrolysis of PET.

Synthesis, characterization, and antibacterial activity of metal nanoparticles embedded into amphiphilic comb-type graft copolymers

Abstract: The synthesis, spectroscopic characterization, and antimicrobial efficiency of gold and silver nanoparticles embedded in novel amphiphilic comb-type graft copolymers having good film-forming properties have been described. Amphiphilic comb-type graft copolymers were synthesized by the reaction of chlorinated polypropylene (PP) (M w = 140,000 Da) with polyethylene glycol (PEG) (M n = 2,000 Da) at different molar ratios. Metal nanoparticles embedded graft copolymers were prepared by reducing solutions of the salts of silver or gold and the copolymer in tetrahydrofuran. The optical properties of the metal nanoparticle embedded copolymers were determined by using UV–visible spectroscopy. Surface plasmon resonance (SPR) of the gold and silver nanoparticle embedded copolymers in toluene was observed at a maximum wavelength (λmax) of 428 and 551 nm in the UV–VIS absorption spectra, respectively. The average particle diameters of the gold and silver nanoparticles were found to be 50 nm from the high resolution scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDS). Amphiphilic polymer films containing silver and gold nanoparticles were found to be highly antimicrobial by virtue of their antiseptic properties to Escherichia coli and Staphylococcus aureus.

Poly(vinyl chloride) plasticized with succinate esters: synthesis and characterization

Abstract: Phthalates pose adverse health effects due to their propensity to leach and the most common, di(2-ethylhexyl) phthalate (DEHP) and di-n-octyl phthalate (DOP), are petroleum-based Conversely, di-esters, succinates are biobased (produced from fermentation of biomass), biodegradable, and therefore potential sustainable replacements for phthalates A series of succinates, di-octyl succinate (DOS), di-hexyl succinate (DHS), di-butyl succinate (DBS), and di-ethyl succinate (DES), were mixed with poly(vinyl chloride) (PVC) The interaction of the plasticizer ester carbonyl with PVC shows an average −5 cm−1 shift of the carbonyl absorbance peak energy The glass transition temperatures (T g), were monitored by differential scanning calorimetry and dynamic mechanical analyses The T gs of DOS and DHS plasticized PVC were significantly lower than DOP plasticized PVC at a lower percent mass On the other hand, PVC plasticized with either DBS or DES exhibited a similar trend in lowering the T g as that of DOP plasticized PVC

Genipin crosslinked microcapsules of gelatin A and κ-carrageenan polyelectrolyte complex for encapsulation of Neem (Azadirachta Indica A.Juss.) seed oil

Abstract: Microcapsules containing neem seed oil (NSO) were prepared using complex coacervation technique and employing gelatin A and κ-carrageenan polyelectrolyte complex. The yield of the coacervate was dependent on the ratio of the two polymers and on the pH of the medium. Viscosity and turbidity measurements were carried out in order to support the ratio of the two polymers that produced the highest yield. The encapsulation efficiency and the release rates of NSO were dependent on the amount of crosslinker, oil loading and polymer concentration. Scanning electron micrographs showed the formation of free flowing spherical microcapsules. The size of microcapsules increased with the increase of the concentration of the polymer. Fourier Transform Infrared Spectroscopy and Differential Scanning Calorimetry study showed that there was no significant interaction between NSO and carrageenan–gelatin complex.

Effect of the presence of lignin or peat in IPN hydrogels on the sorption of heavy metals

Abstract: The adsorption of metal ions Cu2+ and Ni2+ from contaminated simulated water was studied using new starch/acryl amide-based hydrogels in the presence of lignin or peat to create an interpenetrating polymer network (IPN). The chemical structure of the materials was studied using infrared spectroscopy and their morphology was observed by scanning electron microscopy (SEM). The behavior of hydrogels in water and the water transport mechanisms were characterized using Fick’s law. Metal ion sorption was analyzed using inductively coupled plasma spectrometry. Hydrogels showed maximum water absorption values at about 100 h and all of them showed a Fickean water transport mechanism. On one hand, SEM confirmed that the new material is in fact an IPN and, on the other, that the internal porosity shown is responsible for the water absorption. On the other hand, the hydrophobic nature of the dispersed phase and its concentration in the hydrogel formulation seem to influence this process, which could also influence or facilitate the diffusion/sorption of metal ions. Peat-containing hydrogels showed a slightly lower absorption capacity of these ions than lignin-containing formulations. These hydrogels have a high potential to obtain metal ion-collector membranes.

Rheological and mechanical properties of poly(lactic acid)/polystyrene polymer blend

Abstract: Properties modification by blending polymers has been an area of immense interest. In this work, rheological and mechanical properties of poly(lactic acid)/polystyrene (PLA/PS) blends were investigated. PLA/PS blends in different ratios were prepared using a laboratory scale single screw extruder to obtain (3 mm) granules. Rheological properties were studied using a capillary rheometer and the Bagley’s correction was performed. True shear rate (γr), true shear stress (τr), and true viscosity (ηr) were determined, the relationship between true viscosity and (1/T) was studied for PLA70 blend and the flow activation energy at a constant shear stress (Eτ) and a constant shear rate (Eγ) was determined. The mechanical property measurements were performed at room temperature. Stress at break and strain at break were determined. The results showed that PLA/PS blend exhibited a typical shear-thinning behavior over the range of the studied shear rates, and the viscosity of the blend decreased with increasing PLA content. Also it was found that no equal-viscosity temperature exists between PLA and PS. The mechanical results showed immiscibility between PLA and PS in the blend.

Mechanical and thermo-chemical properties of wood-flour/polypropylene blends

Abstract: The main objective of this research was to study the potential of waste polypropylene and waste wood for making wood plastic composites (WPCs). The effects of nanoclay (NC), microcrystalline cellulose (MCC), and coupling agent (MAPP) on the mechanical and thermal properties were also studied. The results showed that mechanical properties of the composites made with MCC were significantly superior to those of unfilled. Addition of MAPP could enhance the mechanical and thermal properties of the blends, due to the improvement of interface bond between the filler and matrix. The significant improvements in tensile properties of the blends composites made with MAPP and NC were further supported by SEM micrographs. The thermogravimetric analysis indicated that the addition of 5 wt% MAPP and 3 wt% NC significantly increased the thermal stability of the blends compared to the pure PP. MCC could not improve the thermal stability. The experimental results demonstrated that the waste materials used are promising alternative raw materials for making low cost WPCs.

Magnetic alignment of cellulose nanowhiskers in an all-cellulose composite

Abstract: Unidirectional reinforced nanocomposite paper was fabricated from cellulose nanowhiskers and wood pulp under an externally applied magnetic field. A 1.2 Tesla magnetic field was applied in order to align the nanowhiskers in the pulp as it was being formed into a sheet of paper. The magnetic alignment was driven by the characteristic negative diamagnetic anisotropy of the cellulose nanowhiskers. ESEM micrographs demonstrated unidirectional alignment of the nanowhiskers in the all-cellulose composite paper. Comparing with control paper sheets made from wood pulp only, the storage modulus in the all-cellulose nanocomposites increased dramatically. The storage modulus along the direction perpendicular to the magnetic field was much stronger than that parallel to the magnetic field. This new nanocomposite, which contains preferentially oriented microstructures and has improved mechanical properties, demonstrates the possibility of expanding the functionality of paper products and constitutes a promising alternative to hydrocarbon based materials and fibers.

Synthesis and characterizations of waterborne polyurethane modified with 3-aminopropyltriethoxysilane

Abstract: Waterborne polyurethane (WPU) was prepared by the reaction of isophorone isocyanate (IPDI), polyether polyol (PTMG1000), dimethylol propionic acid (DMPA), and trimethylol propane (TMP) and 3-aminopropyltriethoxysilane (APTES) as coupling agent. The films of the WPU were prepared by casting emulsions on Teflon surfaces. The structure of the polyurethane (PU) was characterized by Fourier transform infrared spectrometer (FT-IR), thermogravimetry (TG), X-ray diffraction (XRD), and differential scanning calorimeter (DSC). The mechanical properties and solvent absorption of the cast films were also measured quantificationally. FT-IR indicates that –NH2 of APTES reacted with –NCO of PU prepolymer. TG analysis indicates that APTES can improve thermal stability of PU. XRD and DSC show that crystallinity of PU decreased with the increase of w(APTES). It was found that greater mechanical properties of WPU were obtained when chemical networks were formed between PU and APTES. As the mass fraction of APTES increases from 0% to 10%, water absorption decreased from 17% to 8%, ethanol absorption decreased from 46% to 30%. The particle size increases with increase of w(APTES).

An excellent ablative composite based on PBO reinforced EPDM

Abstract: Short poly(p-phenylene-2,6-benzobisoxazole) (PBO) fibers were first used to reinforce ethylene–propylene–diene terpolymer (EPDM) as thermal insulation materials. The effects of PBO fiber length and content on the mechanical and ablative properties of the composites were investigated in detail. Comparing with the severe breakage occurred in short aramid fibers as fillers, only some necking deformation is observed in PBO fibers filled EPDM after processed. After ablated by oxyacetylene flame, the carbonized PBO fibers still keep solid fibrous structure instead of hollow one of carbonized aramid fibers in the char layer. As a result, the PBO fibers/composites show significantly higher tensile strength and ablation resistant abilities than the aramid fibers/composites. Moreover, with the length and content of PBO fibers increasing, both the tensile strength and the ablation resistance of the composites increase gradually though the break elongation reduces sharply. Considering the properties requirement of thermal insulator, PBO fibers with 3.42–5.56 wt% in content and 3–4 mm in length are preferred. The mass loss rate and the erosion rate as low as 0.05 g s−1 and 0.10 mm s−1 are observed in the optimal samples, respectively, which is evidently lower than that of the best aramid fibers/EPDM-based insulations reported so far.

Synthesis and characterization of novel comb-type amphiphilic graft copolymers containing polypropylene and polyethylene glycol

Abstract: Amphiphilic comb-type graft copolymers containing polypropylene (PP) and polyethylene glycol (PEG) have been prepared. Polypropylene-g-polyethylene glycol comb-type thermoplastic amphiphilic copolymers were synthesized by the reaction between chlorinated polypropylene and polyethylene glycol in the presence of a base via a “grafting to” technique. A series of graft copolymers containing PEGs with molecular weights of 600 and 2,000 Da in the range of 4–34 mol% PEG were obtained. The amphiphilic graft copolymers with PEG segments in range between 20 and 30 mol% PEG displayed good film properties with elongation at break 275–440%. The hydrophilicity of the amphiphilic copolymers increases with the increasing PEG content in the copolymer while the mechanical properties decrease. Therefore, PP-g-PEG2000 with PEG contents in the range of 20–30 mol% PEG should be useful for medical and industrial applications where good film properties are needed.

A thermosensitive chitosan/poly(vinyl alcohol) hydrogel containing nanoparticles for drug delivery

Abstract: The synthesis and characterization of a thermosensitive chitosan (CS)/poly(vinyl alcohol) (PVA) hydrogel containing nanoparticles with different charges for drug delivery were reported. Through the electrostatic effect of –N+(CH3)3 and –COO−, the nanoparticles of N-(2-hydroxyl) propyl-3-trimethyl ammonium chitosan chloride(HTCC)–carboxymethyl chitosan (CM) were prepared. The nanoparticles with different charges were obtained by the different ratio of –N+(CH3)3 and –COO−, which were suitable for drug delivery with opposite charges, such as propranolol and diclofenac sodium, respectively. The release of the positive drug was the slowest with the hydrogels containing negative nanoparticles. Similarly, the release of the negative drug was the slowest with the hydrogels containing positive nanoparticles. However, the releases of the two drugs were both the fastest with the pure hydrogels. It indicated the addition of nanoparticles was helpful to slow the suitable drug release. Though the nanoparticles did not reinforce the gel strength, the electrostatic effect between nanoparticles and drugs reduced the burst release. Therefore, the composite gels are attractive for applications as carriers for drug delivery.

The effect of chain extenders structure on properties of new polyurethane elastomers

Abstract: Two series of polyurethane elastomers were synthesized to investigate what effect does the incorporation of various new chain extenders have on the mechanical and thermal properties of polyurethane elastomers. The polyurethane soft segments were based on poly(e-caprolactone) polyol. The hard segment was based on 1,6-hexamethylene diisocyanate in combination with 2,5-dimethyl-3-hexine-2,5-diol (DHD), hexaethylene glycol, glycerin, or castor oil. The results showed that the degradation rate and mechanical properties of the final products can be controlled through the structure of diol chain extenders or/and hard segment cross-linking present in the polyurethane elastomers. The DHD-based polyurethane displayed a relatively low glass transition temperature of −57 °C and a tensile strength of 11–14 MPa and elongation at break of 600–700%. These kinds of materials have potential application in many domains.

Tensile properties of random copolymers of propylene with ethylene and 1-butene: effect of crystallinity and crystal habit

Abstract: The tensile modulus of elasticity and yield strength of semicrystalline random copolymers of propylene with different amount on ethylene or 1-butene co-units were analyzed as a function of the crystallinity and the crystal habit/shape. Samples were prepared by cooling the melt to ambient temperature, and subsequent annealing at elevated temperature. Variation of the cooling rate between 10−1 and 103 K s−1 and of the temperature of annealing allowed preparation of semicrystalline specimens with either lamellar or non-lamellar crystals of different size, and with different crystallinity between about 30 and 70%. Young’s modulus and yield strength increase with increasing crystallinity and consistently are lower for samples containing nodular, that is, almost isometric, non-lamellar crystals of low aspect ratio. For samples of identical crystallinity and crystal habit, an only minor effect of presence of co-units in the crystalline and amorphous phases is observed.

Effect of amylose contents of starches on physical properties and biodegradability of starch/PVA-blended films

Abstract: Recently, synthetic plastics are used widely in various fields, and with increased applications, disposal of waste plastics has become a serious problem. Therefore, development of novel plastics that are degradable by microorganisms in soil has recently been attracting much attention. In this study, starch/PVA-blended films were prepared from commercial starches with the different amylose contents, PVA, and additives by using a simple mixing process and casting method. Glycerol (GL), sorbitol (SO), tartaric acid (TA), and citric acid (CA) were used as additives. The physical properties such as tensile strength (TS), elongation at break (%E), degree of swelling (DS), and solubility (S) with amylose contents of starches were investigated. The amylose content of starches was analyzed by the colorimetric method. Thermal analysis of films was measured by using a differential scanning calorimeter (DSC). Finally, biodegradability of the films was evaluated in a 6-month soil burial test. The examination of the physical properties of biodegradable films indicates that with the higher amylose contents of starch used in preparing the film, TS, and DS of films increased, whereas %E and S decreased. The additives containing both carboxyl and hydroxyl groups, i.e. TA and CA, improved the physical properties of films. A thermal analysis of films revealed that the glass transition temperature (Tg) rose because of the increased crystallization of films with the increasing the amylose contents. Also, films degraded rapidly at the beginning and slow degradation took place until the experiment was completed. The films showed 50–80% degradation.

Cross-linked poly(ethylene vinyl acetate) (EVA)/low density polyethylene (LDPE)/metal hydroxides composites for wire and cable applications

Abstract: Formulations of chemically cross-linked poly(ethylene vinyl acetate) (EVA) and low density polyethylene (LDPE) blends containing metal hydroxides flame retardants such as aluminum hydroxide (ATH) and magnesium hydroxide (MH) were prepared. Comparison of both type of metal hydroxides in respect of their influence on flammability as well as mechanical, thermal, and electrical properties of EVA/LDPE composites is presented. Most of the investigated properties are better for composites containing MH in comparison with composites containing ATH. Influence of various EVA/LDPE ratios on investigated properties is presented as well. Importance of improving compatibility using compatibilizers to improve some of the investigated properties is described. Polyethylene grafted with maleic anhydride (PEgMA) was found to be better compatibilizer for ATH than vinyl silanes.

(S)-2-(Ethyl propionate)-(O-ethyl xanthate) and (S)-2-(Ethyl isobutyrate)-(O-ethyl xanthate)-mediated RAFT polymerization of N-vinylpyrrolidone

Abstract: (S)-2-(Ethyl propionate)-(O-ethyl xanthate) (X1) and the newly synthesized (S)-2-(ethyl isobutyrate)-(O-ethyl xanthate) (X2) were used as the reversible addition-fragmentation chain transfer (RAFT) agents for the radical polymerization of N-vinylpyrrolidone (NVP). The former showed the better chain transfer ability in the polymerization at 60 °C. Kinetics study with X1 shows the psuedo-first order kinetics upto 45% monomer conversion. Molecular weight (M n) of the resulted polymer increases linearly with increase in the monomer conversion upto around 45%. Polydispersity of the corresponding poly(NVP)s increase gradually from 1.2 to 1.9 with increase in the monomer conversion. Chain-end analysis of the resulted polymer by 1H NMR shows clearly that polymerization started with radical forming out of xanthate mediator. Living nature of the polymerization was confirmed from the successful homo chain extension experiment and also the hetero-chain extension experiment involving synthesis of poly(NVP)-b-polystyrene amphiphilic diblock copolymer.

Amphiphilic biodegradable poly(ε-caprolactone)-poly(ethylene glycol)-poly(ε-caprolactone) triblock copolymers: synthesis, characterization and their use as drug carriers for folic acid

Abstract: Amphiphilic biodegradable poly(e-caprolactone)-poly(ethylene glycol)-poly (e-caprolactone) (PCEC) triblock copolymers have been successfully synthesized by the ring-opening polymerization of e-caprolactone (e-CL) employing SnOct as catalyst and double-hydroxyl capped PEG (DHPEG) as macro-initiator. The triblock structure and copolymer composition were conformed by FT-IR, 1H-NMR, and GPC. Using a membrane dialysis method, PCEC micelles were prepared with a core–shell type. The critical micelle concentration (CMC) of PCEC triblock copolymers was determined by fluorescence technique using pyrene as probe, and CMC values decreased with the increase of PCL chain length. From the observation of transmission electron microscopy (TEM), the morphology of polymer micelles was spherical in shape. Micelles size measured by dynamic light scattering (DLS) exhibited a narrow size distribution. Folic acid (FA) was then used as a model drug to incorporate into PCEC micelles. The diameter, drug loading, and drug release rate of PCEC micelles were influenced by the feed weight ratio of FA and copolymer, and polymer composition. In addition, in vitro release experiments of the drug-loaded PCEC micelles exhibited sustained release behavior without any burst effects and the release behavior was also affected by the pH of release media.

Alkyd resins based on waste PET for water-reducible coating applications

Abstract: Simultaneous glycolysis and neutral hydrolysis of waste PET flakes obtained from grinding post-consumer bottles was carried out in the presence of xylene and an emulsifier at 170 °C The product was separated from ethylene glycol (EG), water, and xylene by filtration, and was extracted by water at boiling point thrice The remaining solid was named water insoluble fraction (WIF) The filtrate was cooled to 4 °C, and the crystallized solid obtained by filtration was named water soluble crystallizable fraction (WSCF) These fractions were characterized by acid value (AV) and hydroxyl value (HV) determinations WSCF and WIF were used for preparation of the water-reducible alkyd resins Three long oil alkyd resins were prepared from phthalic anhydride (PA; reference alkyd resin) or depolymerization product of the waste PET (PET-based alkyd resin), glycerin (G), fatty acids (FA), and glycol (EG; reference alkyd resin) or depolymerization product of the waste PET (PET-based alkyd resin) Film properties and thermal degradation stabilities of these alkyd resins were investigated Physical properties (drying times and hardness) and thermal degradation stabilities of the PET-based alkyd resin is better than these properties of the reference alkyd resin

Dynamic mechanical, thermal, and morphological study of ABS/textile fiber composites

Abstract: In this work, acrylonitrile–butadiene–styrene ABS terpolymer was mixed with acrylic fiber, cotton fiber, and waste textile fiber (WTF) (50/50 wt% cotton/acrylic fiber) with 10 and 30 wt% of fiber content in a batch mixer. The composites with 30 wt% of acrylic fiber showed the highest stabilized torque, while the compositions with 30 wt% of cotton were situated at the lowest values in torque rheometry. The fiber addition up to 30 wt% did not have effect on the degradation behavior of ABS matrix. The composites with 30% textile fiber showed a higher degradation step, which is related to fiber degradation. The fiber content resulted in a considerable increase in stiffness at all temperatures as can be observed on the dynamic mechanical thermal properties (DMTA). The reinforcing effect was higher in the region above the glass transition temperature, T g, of the matrix, this is primarily due to the larger difference in mechanical properties between the filler and the matrix as it goes from the glassy to the rubbery state.

Synthesis and characterization of star-shaped block copolymers with polyhedral oligomeric silsesquioxane (POSS)core via ATRP

Abstract: Star-shaped PMMA-b-PS block copolymers with POSS core were prepared by atom transfer radical polymerization of St using star-shaped POSS/PMMA-Cl as a macroinitiator in presence of CuCl, 2,2,-bipyridine, toluene at 110 °C. The core-first method, which used an active multifunctional core to initiate the growth of polymer chains, was applicable to making star-shaped block copolymers with POSS core. The structure of hybrid star-shaped PMMA-b-PS block copolymers was characterized by GPC and 1H NMR, respectively.

Adsorption of cationic dye on N , O -carboxymethyl-chitosan from aqueous solutions: equilibrium, kinetics, and adsorption mechanism

Abstract: In order to improve the adsorption capacity of chitosan (CTS) for methylene blue (MB) cationic dye, a series of N,O-carboxymethyl-chitosans (N,O-CMCTS) were prepared under heterogeneous conditions by controlling the reaction time. The adsorption of MB from aqueous solution onto N,O-CMCTS was studied. The effects of degree of substitution (DS) of N,O-CMCTS, initial pH of the dye solution and adsorption temperature were investigated in detail. The results showed that the adsorption capacities of N,O-CMCTS increased with the increase of DS and N,O-CMCTS with DS of 0.72 exhibited the highest adsorption capacity (349 mg/g). The adsorption kinetics of N,O-CMCTS was found to follow the pseudo-second-order model. The adsorption equilibrium of N,O-CMCTS fitted very well with the Langmuir isotherm model, showing maximum monolayer adsorption capacity of 351 mg/g. The adsorption mechanism of N,O-CMCTS was also discussed by means of FTIR spectra and XPS. The results revealed that the –OH, –NH2, and –COOH groups of N,O-CMCTS were involved in the adsorption process. The desorption studies showed that N,O-CMCTS could be regenerated and used for the adsorption of MB repeatedly.

Characterization of polydimethylsiloxane–polyurethanes synthesized by graft or block copolymerizations

Abstract: We synthesized polydimethylsiloxane–polyurethane dispersions modified with graft copolymerization (PDMS-G-PUDs) and polydimethylsiloxane–polyurethane dispersions modified with block copolymerization (PDMS-B-PUDs). We systematically investigated the effects of PDMS’s structure, content, and molecular weight on properties of copolymer including viscosity, particle size, and stability of dispersions as well as the properties of the film formed by dispersions including gloss, contact angle, water resistance, oil resistance, and mechanical properties. The results demonstrated that the viscosity, particle size, water resistance increased but gloss decreased with the increase of PDMS content and molecular weight. In addition, we compared the properties of PDMS-B-PUD films and PDMS-G-PUD films with the same amount of PDMS and similar molecular weight. PDMS-G-PUD films showed higher water and oil resistance, but lower gloss and poorer mechanical properties. Scanning electron microscopy–energy dispersive spectroscopy analysis (SEM–EDS) indicated that the films of PDMS-G-PUD had better microphase separation and PDMS surface enrichment.

Synthesis and characterization of biocompatible poly(ethylene glycol)-functionalized polyurethane using click chemistry

Abstract: Functionalization of azide moiety-containing polyurethane (PU) with alkyne-decorated poly(ethylene glycol) (PEG) was accomplished by Cu(I)-catalyzed Huisgen [3+2] dipolar cycloaddition click chemistry. The azide moiety containing poly(e-caprolactone)diol was synthesized by the copolymerization of α-chloro-e-caprolactone with e-caprolactone using ring-opening polymerization and further used for PU synthesis. The PEG-functionalized PU was characterized using FT-IR, NMR, and GPC. The hydrophilicity of synthesized polymers was measured using contact angle and water content tests. In vitro cytotoxicity results showed that the amphiphilic PEG-functionalized PU exhibits good biocompatible behavior, which supports the importance of functionalized PU for biomedical applications.

Crystallization, hydrolytic degradation, and mechanical properties of poly (trimethylene terephthalate)/poly(lactic acid) blends

Abstract: Crystallization, melting, hydrolytic degradation, and mechanical properties of poly(trimentylene terephthalate)/poly(lactic acid) (PTT/PLA) blends have been investigated. The blends show a single and composition-dependent glass-transition temperature (T g) over the entire composition range, implying that these blends are fully miscible in the amorphous state. The observed T g is found to increase with increasing PLA content and fitted well with the Gordon–Taylor equation, with the fitting parameter k being 0.91. The cold-crystallization peak temperature increases, while the melt-crystallization peak decreases with increasing the PLA content. Both the pure PTT and PTT/PLA blends cannot accomplish the crystallization during the cooling procedure and the recrystallization occurs again on the second heating. Therefore, on the thermogram recorded, there is exothermal peak followed by endothermal peak with a shoulder. However, to pure PLA, no crystallization takes place during cooling from the melt, therefore, no melting endothermic peak is found on the second heating curve. WAXD analysis indicates PLA and PTT components do not co-crystallize and the crystalline phase of the blends is that of their enriched pure component. With increasing PLA content, the hydrolytic degradation of the blend films increases, while both the tensile strength and the elongation at break of the blend films decrease. That is to say, the hydrolytic degradation of the PTT/PLA blends increases with the introduction of PLA at the cost of the decrease of the flexibility of PTT.

Esterification of cellulose with acyl-1H-benzotriazole

Abstract: For the first time, the acylation of cellulose was realized by activation of carboxylic acid with 1H-benzotriazole. The reaction could be carried out under mild conditions. The acyl-1H-benzotriazole reacts with cellulose leading to cellulose acetate, butyrate, caproate, benzoate, myristate, and stearate with DS values between 1.07 and 1.89. The reaction proceeds completely homogeneously in dimethyl sulfoxide (DMSO)/TBAF × 3H2O (tetrabutylammonium fluoride trihydrate) using acyl-1H-benzotriazole as acylation agent. The cellulose esters were characterized by means of 1H NMR, GPC measurements, and solubility tests.

Effects of [Bmim]OH on structure and conductive properties of alkaline PVA/[Bmim]OH membranes

Abstract: A series of alkaline polyvinyl alcohol/1-ethyl-3-methylimidazolium hydroxide (PVA/[Bmim]OH) electrolyte membranes were developed via a direct blending and solution casting method. The structure and conductive properties of PVA/[Bmim]OH membranes with various concentrations of [Bmim]OH were systematically studied using X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX), attenuated total reflectance Fourier-transform infrared (ATR-FTIR), tensile-strength analysis, and AC impedance spectroscopy. When blended, the PVA/[Bmim]OH membrane exhibited superior ionic conductive and the maximum ionic conductivity was found around 0.0196 S cm−1 when the weight ratio of [Bmim]OH to PVA was 2.0. A model was proposed to illustrate the structure of PVA/[Bmim]OH membranes and the effect of [Bmim]OH on the ionic conductivity of the PVA matrix. The results and the model indicated that the addition of [Bmim]OH could significantly improve the electrochemical properties of the membranes, which is a promising candidate for direct methanol fuel cells (DMFCs) applications.

Supermolecular structure of wood/polypropylene composites: I. The influence of processing parameters and chemical treatment of the filler

Abstract: Wide-angle X-ray scattering (WAXS) and scanning electron microscopy (SEM) were used to investigate the effect of chemical modifications of wood as well as processing parameters on the supermolecular structure and morphology of wood/polypropylene (PP) composites. The surface of the filler was modified to enhance the adhesion between hydrophilic cellulose and hydrophobic polymer. Wood modification was performed by esterification with anhydrides (maleic, propionic, phthalic, crotonic and succinic) and by physical treatment with NaOH. The composites for structural characterization were prepared by the compression moulding method and injection technique. A new design of the compression mould, which ensured the wood pulling, was proposed. It was found that the polymorphs of PP matrix developed due to melt-shearing strongly depended on the pulling temperature as well as on the type chemical modification of wood. The modification of wood caused a significant decrease in the ability to generate the hexagonal phase of PP. Moreover, at a higher temperature of the mould, the amount of hexagonal phase of PP matrix slightly decreases. These investigations are very significant because characterize influence of real parameters processing as well as surface modification of filler on structure of composite materials.

The effects of physical and chemical interactions in the formation of cellulose aerogels

Abstract: Aerogels are low density materials which are produced from wet gels, and find a variety of potential uses. The relative importance of shape/geometry and self-association of the starting materials for the production of aerogels is studied herein. Aerogels were produced from microcrystalline cellulose (MCC) and its functionalized analog, carboxymethyl cellulose (CMC). With increasing functionalization, CMC gains the potential for self-association, differentiating itself from MCC. The present study explores the preparation of aerogels from MCC and CMC, comparing performance with and without significant self-association potential, and more broadly evaluating the production of low density structural materials from renewable cellulose. It was observed that the self-association present in CMC substantially increases aerogel mechanical properties when compared those of non-interactive MCC. Aspect ratio is proposed to also be an import parameter in the structure–property relationship for these materials.