Biodegradable poly(butylene succinate) (PBS)/carbon fiber (CF) composites were prepared by melt blending method using twin-screw extruder followed by injection molding. Mechanical properties, crystallization behavior, morphology, crystal structure, and thermal stability of PBS/CF composites were investigated with different CF contents (0, 5, 10, 15, and 20 wt%). It was found that the tensile and impact properties of the composites were improved markedly with the addition of CF; while too much CF would lead to agglomeration and thus weaken the improvement. Scanning electron microscopic photographs on the fracture surfaces showed superior interfacial adhesion between fibers and PBS matrix. Crystallization peak temperature of PBS in its composites was increased due to the heterogeneous effect of CF. The spherulite size of PBS/CF composites decreased and the nucleation density increased drastically. The crystal structure was not affected by the incorporation of CF, as confirmed from the wide-angle X-ray diffraction analysis. thermogravimetric analysis showed that the thermal stability of PBS/CF composites was also enhanced. POLYM. COMPOS., 36:1335–1345, 2015. © 2014 Society of Plastics Engineers

Biodegradable radiopaque iodinated poly(ester-urethane) (I-PU), consisting of poly(ε-caprolactone) (PCL) diol and iodinated bisphenol A (IBPA), has been successfully synthesized via a coupling reaction of PCL-diisocyanate and IBPA with varying compositions. The IBPA with four iodine atoms per molecule was applied as a chain extender to endow the I-PUs with intrinsic X-ray visibility. The chemical structure and molecular weights of I-PUs were characterized by Fourier transform infrared spectroscopy (FT-IR), proton-nuclear magnetic resonance, and gel permeation chromatography (GPC). The effects of IBPA on the physical properties of I-PUs were systematically studied by means of differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), and wide-angle X-ray diffraction (WAXD). The DSC results showed that the crystallization of PCL segments in I-PUs was restrained with increasing amount of IBPA, which was also confirmed by WAXD. In the X-radiography analysis, all the synthesized I-PUs exhibited high radiopacity compared with an aluminum wedge of equivalent thickness. Enzymatic degradation tests showed that the incorporation of IBPA prolonged the degradation of I-PUs and distinct mass loss and degradation happened in the third month. Basic cytocompatibility conducted using rat adipose-derived cells proved that all the I-PUs and their biodegradation products were nontoxic. The radiopaque I-PUs is expected to possess a significant advantage over the traditional polymer counterparts in some related biomedical fields. © 2013 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 102A: 1121–1130, 2014.

Polyamide 6/carbon fiber (PA6/CF) composites toughened with maleated elastomers were prepared by melt blending using twin-screw extruder followed by injection molding. Three kinds of maleated elastomers, maleic anhydride (MAH)-grafted ethylene-vinyl acetate copolymer (EVA-g-MAH), MAH-grafted ethylene-propylene-diene terpolymer (EPDM-g-MAH), and MAH-grafted hydrogenated styrene-butadiene-styrene (SEBS-g-MAH), were used to toughen the PA6/CF composites. The mechanical properties, morphology, nonisothermal crystallization, and subsequent melting behavior of PA6 hybrid composites were investigated. Mechanical tests indicated that incorporation of elastomers improved the impact properties of CF-reinforced PA composites accompanied with loss of tensile strength and modulus. It was observed from scanning electron microscope photographs that modification with maleated elastomers improved the interfacial adhesion between the CFs and PA6 matrix. Nonisothermal crystallization behavior showed that three kinds of elastomers had negative effect on crystallization and retarded crystallization of PA6. Kissinger's analysis illustrated that addition of CF slightly increased the crystallization activation energy of PA6, whereas incorporation of elastomers reversed it compared with pure PA6. Furthermore, a slight decrease in crystallinity and melting peak of the composites after incorporation of elastomers was observed compared with pure PA6. Polarizing optical microscope results showed that the transcrystallinity phenomenon seemed to be also affected when the matrix was added by the elastomers. POLYM. COMPOS., 35:2170–2179, 2014. © 2014 Society of Plastics Engineers

A fibrous scaffold is required to provide three-dimensional (3D) cell growth microenvironments and appropriate synergistic cell guidance cues. In this study, porous scaffolds with different mass ratio of poly(lactic acid) to poly(3-hydroxybutyrate-co-4-hydroxybutyrate) (P(3HB-co-4HB)) for tissue engineering were prepared by a modified particle leaching method. The effect of the addition of P(3HB-co-4HB) on microstructural morphology, compression property, swelling behavior, and enzymatic degradation of hybrid scaffolds was systematically investigated. The results indicated that this method was simple but efficient to prepare highly interconnected biomimetic 3D hybrid scaffolds (PP50/50 and PP33/67) with fibrous pore walls. The cytocompatibility of hybrid scaffolds was evaluated by in vitro culture of mesenchymal stem cells. The cell-cultured hybrid scaffolds presented a complete 3D porous structure, thus allowing cell proliferation on the surface and infiltration into the inner part of scaffolds. The obtained hybrid scaffolds with pore size ranging from 200 to 450 µm, over 90% porosity, adjustable biodegradability, and water-uptake capability will be promising for cartilage tissue engineering applications. POLYM. ENG. SCI., 54:2902–2910, 2014. © 2014 Society of Plastics Engineers

To improve the hemocompatibility and biocompatibility of polyurethanes (PUs), PU surface was firstly modified by poly(ethylene glycol) PEG through acryloyl chloride and subsequently grafted on carboxymethyl-chitosan (CMCS). Attenuated total reflection Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy analysis confirmed that carboxyl-chitosan was grafted onto PUs surface. The surface properties of unmodified and modified PU films were determined and compared by water contact angle assessment. After PEG and CMCS grafting, the surface energy of the PU film was increased. Furthermore, the hemocompatibility of the modified PU films was systematically evaluated by bovine serum albumin (BSA) adsorption, the dynamic blood clotting test, the platelet adhesion test, and the hemolytic test. It appears that BSA adsorption and platelet adhesion were significantly curtailed for the modified PU films. Therefore, the obtained results showed the modified PU film has better hemocompatibility. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013

Polymer/inorganic nanocomposites were significant hybrid materials because of their unique properties. The surface of bare nanoparticles (b-TiO₂) was modified by aminopropyl trimethoxy silane to obtain grafted TiO₂ (g-TiO₂) nanoparticles for the improvement of nanoparticles dispersion. The b-TiO₂ and resulting g-TiO₂ nanoparticles were introduced into poly(ε-caprolactone) (PCL) matrix to prepare PCL/TiO₂ nanocomposites by in situ polymerization. The effects of b-TiO₂ and g-TiO₂ nanoparticles on the structure, morphology, and properties of nanocomposites were characterized and compared. The results showed that the crystalline structure of PCL matrix was not affected significantly by adding b-TiO₂ or g-TiO₂ nanoparticles. The g-TiO₂ nanoparticles had a finer dispersion and better compatibility than bare TiO₂. The introduction of g-TiO₂ into PCL matrix increased the crystallization temperature and improved thermal stability of the nanocomposites with respect to untreated TiO₂. The surface-treated nanoparticles played an important role in strengthening mechanical properties of the nanocomposites because of its well dispersion and strong interfacial interaction between the nanoparticles and PCL matrix. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012

To accelerate the crystallization of poly(L-lactic acid) (PLLA) and enhance its crystallization ability, a multiamide nucleator (TMC) was introduced into the PLLA matrix. The thermal characteristics, isothermal and nonisothermal crystallization behavior of pure PLLA and TMC-nucleated PLLA were investigated by differential scanning calorimetry. The determination of thermal characteristics shows that the addition of TMC can significantly decrease the onset temperature of cold crystallization and meanwhile elevate the total crystallinity of PLLA. For the isothermal crystallization process, it is found that the overall crystallization rate is much faster in TMC-nucleated PLLA than in pure PLLA and increases as the TMC content is increased, however, the crystal growth form and crystalline structure are not influenced much despite the presence of TMC. In the case of nonisothermal crystallization, the nucleation efficiency and nucleation activity were estimated and the results indicate that excellent nucleation-promoting effect could be achieved when the weight percentage of TMC is chosen between 0.25% and 0.5%. Polarized optical microscopy observation reveals that the nuclei number of PLLA increases and the spherulite size reduces greatly with the addition of TMC. POLYM. ENG. SCI., 2012. © 2011 Society of Plastics Engineers

Poly(ϵ-caprolactone) (PCL)/titanium dioxide (TiO₂) nanocomposites were prepared by in situ polymerization of ϵ-caprolactone in the presence of modified-TiO₂ nanoparticles as initiators. The molecular weight of PCL matrix was dependent on the amount of the TiO₂ fillers. The incorporation of TiO₂ did not significantly affect the crystalline structure of PCL. Moreover, a tendency of the nanoparticles to form aggregates was observed, especially at higher fillers contents. The analysis of the crystallization process showed that the addition of TiO₂ nanoparticles accelerated the crystallization rate of PCL, and the crystallization rates increased by increasing the filler content. The crystallization activation energy dependence on the filler content observed here is probably the consequence of the two competing factors. The tendency of activation energy obtained by nonisothermal crystallization is similar to that of isothermal crystallization. POLYM. ENG. SCI., 2012. © 2011 Society of Plastics Engineers

Nonisothermal crystallization kinetics and melting behavior of poly(ε-caprolactone)-b-poly(ethylene glycol)-b-poly(ε-caprolactone) triblock copolymer (PCL-PEG-PCL), in which the weight fraction of the PCL block is 0.87, has been studied by differential scanning calorimetry (DSC). The nonisothermal crystallization data at various cooling rates are analyzed with the Ozawa, modified Avrami, and Mo models. The modified Avrami and Mo models were found to describe the nonisothermal crystallization processes fairly well. The values of the Avrami exponent n were near three, suggesting the crystallization process with a three-dimensional crystallite growth by heterogeneous nucleation mechanism. The crystallization activation energy estimated from the cooling scans using Kissinger's method was 168.9 KJ/mol. The phenomenon of the double melting behavior was observed for the PCL block during melting process after nonisothermal crystallization, being the reflection of a complicated crystallization process and the existence of the amorphous middle PEG block. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009