Fluorinated Linear Copolyimide Physically Crosslinked with Novel Fluorinated Hyperbranched Polyimide Containing Large Space Volumes for Enhanced Mechanical Properties and UV-Shielding Application

Fluorinated hyperbranched polyimide (FHBPI), a spherical polymer with large space volumes, was developed to enhance fluorinated linear copolyimide (FPI) in terms of mechanical, UV-shielding, and hydrophobic properties via simple blend and thermal imidization methods. FPI possessed superior compatibility with FHBPI, and no obvious phase separation was found. The incorporation of FHBPI led to the formation of physical crosslinked network between FPI and FHBPI, which markedly improved the mechanical properties of the FPI, resulting in maximum enhancement of 83% in tensile strength from 71.7 Mpa of the pure FPI to 131.4 Mpa of the FPI/FHBPI composite film containing 15 wt % of FHBPI. The introduction of FHBPI also changed the surface properties of composites from hydrophilicity to hydrophobicity, which endowed them with outstanding dielectric stability. Meanwhile, the thin FPI/FHBPI composites kept the high transparency in the visible spectrum, simultaneously showing enhanced UV-shielding properties and lifetimes under intense UV ray. This was attributed to the newly formed charge transfer complex (CTC) between FHBPI and FPI. Moreover, the FPI/FHBPI composites possessed preeminent thermal properties. The properties, mentioned above, gave the composites enormous potential for use as UV-shielding coatings in an environment filled with high temperatures and strong ultraviolet rays.

Enhanced Thermal Performance and Impact Strength of UHMWPE/Recycled-PA6 Blends Synthesized via a Melting Extrusion Route

The blends of ultra-high molecular weight polyethylene (UHMWPE) and recycled-polyamide 6 (R-PA6) were prepared via a melting extrusion route using high-density polyethylene-graft-maleic anhydride (HDPE-g-MAH) as the compatibilizer. The morphologies and distributions of the chemical components of the blends were characterized by scanning electron microscopy and synchrotron Fourier transform infrared microspectroscopy. The effects of R-PA6 content on the Vicat softening temperature (VST), heat distortion temperature (HDT), and impact strength of the blends were studied. Remarkably, in comparison with those of UHMWPE, the VST and HDT of UHMWPE/R-PA6 blends with 44 wt% R-PA6 were increased to 165.1 and 98.4°C, respectively, and the Charpy impact strength and Izod impact strength of the blends were enhanced to 33.9 and 16.2 kJ/m2, respectively. In addition, it was found that the blending system containing 44 wt% R-PA6 and 48 wt% UHMWPE exhibited the best compatibility when it was prepared using 8 wt% HDPE-g-MAH. The distribution of the phases of UHMWPE and R-PA6 was uniform, and no obvious phase separation was observed in the blends.

Synthesis, characterization, and crystallization of biodegradable poly(ε-caprolactone)-poly(L-lactide) diblock copolymers

Three diblock copolymers of PCL6k-PLLA2k, PCL6k-PLLA4k, and PCL6k-PLLA6k were prepared and their crystallization behaviors were investigated. The molecular weights of the copolymers calculated from 1H nuclear magnetic resonance spectra were equivalent to the designed molecular weights. The gel permeation chromatography spectra of the copolymers showed one peak, which revealed that the copolymers were monodisperse. The crystallization capability of poly(ε-caprolactone) (PCL) decreased and that of poly(L-lactide) (PLLA) increased when the molecular weight of the PLLA block was increased from 2k to 6k. PCL spherulites in the PCL6k-PLLA2k copolymer film were smaller than those in PCL6k-PLLA4k or PCL6k-PLLA6k copolymer film. PCL spherulites in the PCL6k-PLLA2k copolymer film grew fastest within all three diblock copolymers. An obvious phase separation phenomenon was observed on the surface of PCL6k-PLLA6k copolymer film in atomic force microscopy images.

Research into the Preparation and Performance of Hydrotalcite/ MC Nylon 6 by In Situ Intercalation Polymerization

Hydrotalcite (LDHs) / MC nylon 6 composites were prepared by in- situ intercalation polymerization, followed by morphology and mechanical properties’ characterization of composites. FTIR shows that chemical structure of the molecular chain of the MC nylon 6 is not changed with adding hydrotalcite; SEM reveales that LDHs (2.5, wt-%) has good dispersion and compatibility in the MC nylon 6 matrixes; but when the amount of LDHs is excessive, the composites show obvious phase separation phenomenon. Hydrotalcite can significantly improve the mechanical properties of the composites. When the amount of hydrotalcite reaches 2.5% (wt-%), the composite has best comprehensive mechanical performance. Comparing with untreated MCPA6, the tensile strength and notched Izod impact strength are respectively increased by 68 % and 53 %.

Investigation of a Collagen-Chitosan-Hydroxyapatite System for Novel Bone Substitutes

Collagen (Col) and chitosan (Chi) are both natural polymers and have received extensive investigation in recent years in the field of tissue engineering, but there are few reports on the introduction of hydroxyapatite (HA) into the Col-Ch system. In this study, based on the miscibility of these two polymers under proper condition, hydroxyapatite (HA) was synthesis in the Col-Chi system by in-situ co-precipitate method to give rise to a novel nanocomposite. The structural characterization of such Col-Ch-HA nano-materials was carried out by using FT-IR, XRD, SEM and TGA analyses with main components and Col-Chi samples used for comparison. It was found that there exist interactions between Col and Chi molecules. The nucleation and growth of inorganic phase occurs in the Col-Chi system and final products are uniform dispersion of nano-sized HA in the Col-Chi network without obvious phase separation. This novel nanocomposite would be a promising material for bone tissue engineering.