Poultry feather fiber is transformed into biothermoplastics using a twin screw extruder, and the plasticizing effect of four different plasticizers on the material properties is investigated. Conformational changes, viscoelastic behavior, thermal degradation, and phase transitions are assessed by means of FTIR spectroscopy, DMA, TGA, and DSC, respectively. The mechanical properties of the plasticized resins are assessed by tensile measurements, while optical transmittance is recorded using UV‐Vis spectrophotometry. The water uptake behavior of the fiber keratin and plasticized resins is also investigated.
Copolymers of 3,4‐ethylenedioxythiophene and 3‐methylthiophene have been prepared by recurrent potential pulses using monomer mixtures with various concentration ratios, their properties being compared with those of the corresponding homopolymers. In addition, different technological applications have been tested for the generated copolymers. Results indicate that the properties of the copolymers are closer to those of poly(3,4‐ethylenedioxythiophene) than to those poly(3‐methylthiophene). Furthermore, the ability of the copolymers to store charge and to interact with plasmid DNA suggest that they are very promising materials.
PHBV is produced by bacteria as intracellular carbon storage. It is advantageous concerning biocompatibility and biodegradability, but its low crystallization rate hinders the melt‐processing of fibers. This problem can be overcome by combining PHBV with PLA in a core/sheath configuration and introducing a new spin pack concept. The resulting PHBV/PLA bicomponent fibers show an ultimate tensile stress of up to 0.34 GPa and an E‐modulus of up to 7.1 GPa. XRD reveals that PLA alone is responsible for tensile strength. In vitro biocompatibility studies with human fibroblasts reveal good cytocompatibility, making these fibers promising candidates for medical therapeutic approaches.
Low density polyethylene (LDPE) was prepared into micro‐ or submicro‐spheres or nanofibers via melt blending or extrusion of cellulose acetate butyrate (CAB)/LDPE immiscible blends and subsequent removal of the CAB matrix. The sizes of the PE spheres or fibers can be successfully controlled by varying the composition ratio and modifying the interfacial properties of the blends. The surface structures of LDPE micro‐ or submicro‐spheres and nanofibers were analyzed using SEM and FTIR‐ATR spectroscopy. In addition, the crystalline structures of the LDPE nanofibers were characterized.
Low‐crystalline random and gradient P(EO‐co‐PO) copolymers and amorphous PPO and PBO of high molecular weight were synthesized by anionic coordination polymerization. Polymer gel electrolytes based on these (co)polymers were prepared and tested for long‐term performance of DSSC. The DSSC based on P(EO‐co‐PO) copolymers have longer life time compared to the homo‐PEO‐ and homo‐PPO‐based DSSC, respectively. The cells containing the chemically crosslinked copolymer gel exhibited a high efficiency of 6% after 25 d performance, whereas the solar cells based on physically crosslinked copolymer gel showed fast degradation.
A series of hydrogels based on poly(ethylenglycol) methyl ether methacrylate (PEGMEMA) is synthesized using macromonomers of three different molecular weights, in combination with varied degrees of chemical crosslinking. The effects of PEGMEMA, initiator, and crosslinker concentrations on gel yield and swelling properties are studied. In addition, the chemical structure of the gels is characterized by FTIR and solid‐state NMR spectra. The swelling and rheological behaviors of hydrogels as well as protein partitioning into the gels are discussed in terms of the network mesh size. Low protein sorption and bacteria deposition tendencies indicate that PEGMEMA‐based hydrogels could be highly beneficial for uses as fouling‐resistant materials, for instance, as protective coatings for desalination membranes.
A novel ternary hybrid of thermoplastic polyurethane/hindered phenol/hindered amine was designed and prepared. Selected hindered phenols and hindered amines were settled down, respectively, in the soft and hard phases of TPU with molecular‐level dispersion. As a result, the ternary hybrid showed a prominent enhancement in the tan δ peak value and distinct broadening of the glass transition region, due to the formation of strong interactions (hydrogen bonding) between segment and small polar molecules occurred in each phase of TPU, which demonstrated the promising future as high‐performance damping material of this ternary hybrid.
MMA‐EHA copolymers with different compositions and with a low amount of AA were synthesized and used as impact modifier for epoxy networks. The effect of the copolymers on the tensile and dynamic mechanical properties as well as impact resistance of the epoxy network was evaluated. The addition of 10 phr of low‐molar‐mass MMA‐EHA copolymer with defined composition resulted in a significant increase in impact resistance without any significant changes in the tensile strength, modulus, and glass transition temperature. The morphology of the modified epoxy network depends upon the copolymer composition.
New talc/PBAT hybrid materials were prepared through reactive extrusion. First, PBAT was free‐radically grafted with MA to improve the interfacial adhesion between PBAT and talc. Then, the resulting MA‐g‐PBAT was reactively melt‐blended with talc through esterification reactions of MA moieties with the silanol functions from talc. Sn(Oct)2 and DMAP were used as catalysts. Interestingly, the tensile properties for these compatibilized composites were improved due to a better interfacial adhesion between both partners. XPS showed the formation of covalent ester bonds between the silanol functions from talc particles, and the MA moieties grafted onto the polyester backbones.
A 3D spongy collagen cryogel was prepared using DAS as the cross‐linker. FTIR and CD studies demonstrate that crosslinking is achieved through the reaction of the DAS aldehyde groups with the free amino groups in collagen without affecting the triple helix of collagen. SEM demonstrates that the cryogel has a heteroporous structure with interconnecting pores. DSC measurements reveal that the cryogels have improved thermal stability in comparison with pure collagen. Moreover, the ESR shows that the water uptake of the cryogel decreases with DAS content. Evaporation tests indicate that the cryogel can hold moisture for a long time. Since both collagen and DAS are nontoxic and the resultant cryogel is blood‐compatible, the cryogel is expected to be useful, e.g., as wound dressing.
The synthesis of 5,11,17,23‐amino‐25,26,27,28‐propoxycalix[4]arene (calix[4]amine, 4 ) starting from 5,11,17,23‐nitro‐25,26,27,28‐propoxy‐calix[4]arene ( 3 ) via microwave‐assisted transfer hydrogenation is reported. Furthermore, the calix[4]amine ( 4 ) is functionalized with an acrylamide moiety. The swelling behavior in water, the influence on the glass transition temperature, and the shear modulus of a crosslinked N,N‐dimethylacrylamide (NDA) polymer with 5,11,17,23‐acrylamido‐25,26,27,28‐propoxycalix[4]arene ( 5 ) and EGDMA, respectively, are investigated.
We demonstrate solution blending of PVDF with PECA obtained by controlled polymerization of ECA. This method circumvents the processing detriments posed by the instant cross‐linking of CAs when encountering aprotic solvents such as DMF, a common PVDF solvent. The slower polymerization of ECA was tracked using NMR spectroscopy. The polymer mixture solutions were spin‐coated to study the film morphology, wettability, and surface energy. The polymer films show strong contribution of basic polar surface energy that can be beneficial in biomedical applications. DSC and TGA were also performed on the blended polymers. The DSC thermograms show clear suppression of PVDF melting point, which provides evidence of two‐polymer miscibility.
Curaua fibers were treated with ionized air to improve the fiber/phenolic matrix adhesion. The treatment with ionized air did not change the thermal stability of the fibers. The impact strength increased with increase in the fiber treatment time. SEM micrographs of the fibers showed that the ionized air treatment led to separation of the fiber bundles. Treatment for 12 h also caused a partial degradation of the fibers, which prompted the matrix to transfer the load to a poorer reinforcing agent during impact, thereby decreasing the impact strength of the related composite. The composites reinforced with fibers treated with ionized air absorbed less water than those reinforced with untreated fibers.
This paper demonstrates how the electric‐field‐assisted thermal annealing of octadecylamine‐functionalized SWNT/PMMA films induces an increase in the composite transversal conductivity of several orders of magnitude and a decrease in the lateral conductivity. This difference has been rationalized in terms of the nanotube alignment into the polymer matrix along the electric field direction. This result provides an initial understanding of how electric fields can be used to control the bulk physical properties of such nanocomposites.
Poly(lactic acid) plasticized with 15 and 20 wt.‐% of polyadipate was melt‐blended with different amounts of an O‐MMT (1–5 wt.‐%) to prepare nano‐biocomposites. The effect of plasticizer and nanofiller contents on the morphology and on thermal, mechanical and barrier properties of PLA‐based nano‐biocomposites was evaluated in order to understand their structure‐properties relationships. The oxygen transmission rate was notably reduced (around 45%) with increasing amount of clay due to an increased tortuosity. However, for clay concentrations above 3 wt.‐%, a significant detriment in ductile properties could also be observed. For a given amount of nanofiller, the increasing plasticizer concentration improved the clay dispersion through the polymeric matrix.
A new technique for design and preparation of self‐reinforced starch films is introduced. The films were based on a high‐amylose corn starch that was chemically modified in different ways. Hydroxypropylation was used to decrease gelatinization temperature and improve processability. The reinforcing component consisted of cross‐linked starch granules, where the crosslinking increased granule thermal stability and moisture resistance. Distribution of the cross‐linked starch was imaged by CLSM, and the matrix/particle interface was studied by SEM. Modulus and tensile properties of the starch film were increased by about 30 and 20%, respectively, after addition of rigid cross‐linked starch particles. A perfect interface between matrix and reinforce agent was obtained.
The present work provides a critical review of polymer crystallization studies using SALS; experimental methods, analysis techniques, observations and their relations with respect to other techniques are discussed. Furthermore, the fact that nucleation might be accompanied by large scale density fluctuations has been investigated for the flow‐induced crystallization of iPB. SALS was applied to measure density and orientation fluctuations, whereas complementary results were obtained from optical microscopy. The observations from both crystallization and melting experiments seem to indicate that the detected density fluctuations result from the presence of weakly anisotropic structures, rather than being an indication of densification before the onset of crystallization.
The effects of incorporated nano/micro‐diamond (NMD) on the physical properties, crystallization, thermal/hydrolytic degradation of poly(L ‐lactic acid) (PLLA) were investigated for a wide NMD concentration range of 0–10 wt.‐%. Incorporated NMD increased the tensile modulus and strength of PLLA films but decreased the elongation at break of PLLA films. Incorporated NMD accelerated the crystallization of PLLA during heating and cooling and increased the absolute crystallization enthalpy of PLLA films (except for an NMD concentration of 10 wt.‐% during cooling) but did not alter the crystallization mechanism. Incorporated NMD increased and decreased the thermal stability of PLLA films for NMD concentrations of 1–5 and 10 wt.‐%, respectively, and increased the hydrolytic degradation resistance of PLLA films.
A novel technique is described that uses stretching‐controlled thermal micromolding with etched metal surfaces as templates for the mass‐production of superhydrophobic polymer films. First, the metal surface is etched and then used as a template to thermally replica‐mold the polymer (e.g., polyethylene). The resulting film surfaces exhibited stable superhydrophobicity with water contact angles >150° and sliding angles ≈7°. SEM imaging demonstrates that the microstructure on the superhydrophobic surface is formed by stretching from the microholes of the template during separation. This technique can be easily combined with melt‐flow casting for manufacturing superhydrophobic polymer surfaces on a large scale.
The crystallization behavior of poly(L ‐lactide) (PLLA) was investigated in the presence of benzenetricarboxylamide (BTA) derivatives as crystal nucleators. BTA‐cyclohexyl (BTA‐cHe) was the most effective nucleating agent, but induced a complete loss of transparency of the processed material. On the other hand, BTA‐n‐hexyl (BTA‐nHe) enhanced crystallization with little increase in haze. PLLA containing BTA‐cHe enhanced PLLA crystallization in α‐form crystal whereas BTA‐nHe enhanced α′‐form (incomplete α‐form) with forming smaller spherulites. TEM revealed BTA‐nHe had completely dissolved in the PLLA matrix in melt and recrystallized during the thermal annealing process. It was also found that the size of the recrystallized BTA‐nHe was in the nanometer range to effectively nucleate the PLLA crystals.
