Cheng-Lung Wu

Biodegradable composition of poly(lactic acid) from renewable wood flour

Maleic anhydride-grafted poly(lactic acid) (PLA-g-MAH) was prepared by blending with wood flour (WF). The effect of MAH and WF inclusion on the mechanical and thermal properties of the composites was examined. PLA-g-MAH/WF had optimum tensile properties compared with PLA/WF. Scanning electron microscopic images indicated poor interfacial adhesion of the PLA/WF. It was enhanced after MAH was grafted onto PLA; the PLA-g-MAH/WF showed excellent compatible morphology. Results also revealed that the biodegradation of PLA and PLA-g-MAH was improved with increasing of WF content.

Synthesis and properties of novel biodegradable polyurethanes containing fluorinated aliphatic side chains

This study used 5H–octafluoropentanoylfluoride and 2-amino-2-methyl-1,3-propanediol to synthesize a novel fluoro chain extender 2,2,3,3,4,4,5,5-octafluoro-N-(1,3-dihydroxy-2-methylpropan-2-yl) pentanamide (ODMP). Furthermore, 4,4′-diphenylmethane diisocyanate served as the hard segment, polycaprolactone diol (PCL) served as the soft segment, and ODMP served as the chain extender in the novel synthesized polyurethanes (ODMP/PUs). Gel permeation chromatography revealed that the molecular weight of the ODMP/PUs increased when the ODMP content was increased. 1H and 19F nuclear magnetic resonance and Fourier transform infrared spectroscopy verified that the ODMP chain extenders were successfully synthesized and that the ODMP chain extenders were successfully incorporated into the backbone of the PUs. The interaction between the -NH (hydrogen bond) and CF2 groups in the ODMP/PUs became stronger when the ODMP content was increased. Thermal analysis revealed that the initial decomposition temperature of the ODMP/PUs decreased and the second decomposition temperature increased when the polymers’ ODMP content was increased. Higher ODMP content also resulted in the ODMP/PUs’ higher glass transition and dynamic glass transition temperatures and lower ODMP maximum stress and Young’s modulus, causing a lower elongation at break. ODMP/PUs with higher ODMP content exhibited more protrusions and more rugged surfaces. The chemical resistance of the ODMP/PUs increased when the fluorine content was increased. Scanning electron microscopy revealed that ODMP/PUs with higher PCL content exhibited higher levels of hydrolytic degradation. Finally, in vitro erythrocyte tests revealed that increasing the ODMP chain extender content reduced the average number of erythrocytes adhering to the surface of the PUs.

In situ polymerisation and characteristic properties of the waterborne graphene oxide/poly(siloxane-urethane)s nanocomposites

In this study, waterborne graphene oxide/poly(siloxane-urethane)s (GO/SWPUs) nanocomposites were in situ synthesised. Therein, siloxane units facilitated the crosslinking of polyurethanes, and GO imparted the nanocomposites with special functions. With increasing GO content, the average particle size, viscosity, and ionic conductivity of the GO/SWPU dispersion increased, but the absolute value of the zeta potential decreased; this was due to ionic interactions between the COO−NH+(C2H5)3 ions of the SWPU and COO−H+ ions of the GO. The surface roughness of the GO/SWPU film was larger as GO content was higher, which was due to a strong interaction between the GO and SWPU phases. Increasing the GO content improved the thermal resistance, dynamic glass transition temperature, and tensile strength of the GO/SWPU film, but adding more than 0.1 wt% GO yielded unfavourable results. Thus, adding GO improved the thermal and mechanical properties of the GO/SWPU nanocomposites, but this improvement was observed only up to a certain GO concentration, possibly because of the agglutination of GO in SWPU. In addition, the surface and volumetric electrical resistivities of the GO/SWPU nanocomposites decreased when the GO content were increased.

Preparation and characterization of biodegradable polyurethanes composites containing thermally treated attapulgite nanorods

In this study, polyurethane (PU) was synthesized using 4,4,-diphenylmethane diisocyanate as a hard segment, polytetramethylene glycol and polycaprolactone diol as soft segments, and 1,4-butanediol (1,4-BD) as a chain extender. Thermally treated attapulgite (TAT) was added to the PU matrix to prepare TAT/PU nanocomposites. The TEM, FT-IR, XRD and EDS were used to characterize the structure and morphology of the TAT/PU nanocomposites. The TEM results show that TAT maintains its rod-like structure in the PU matrix. The results showed that the addition of a small content of TAT resulted in no obvious changes in the Fourier transform infrared (FT-IR) spectra. XRD results showed that the main crystalline peak of TAT became more pronounced with increasing content of TAT, and EDS showed that the content of Si increased with increasing content of TAT in the TAT/PU nanocomposites. The thermal and mechanical properties were optimal at 2 wt% TAT. When TAT was added at 5 wt%, agglomeration occurred, resulting in a decrease in the thermal and mechanical properties of the TAT/PU nanocomposites. Contact angle and AFM results showed that the hydrophobicity and surface roughness increased with increasing content of TAT. SEM showed that the hydrolytic degradation was affected by the test temperature, test time, and the content of TAT. Moisture absorption tests showed that the moisture absorption of TAT/PU nanocomposites increased with increasing content of TAT and higher environmental humidity.

Preparation and characterization of biodegradable polyurethanes composites filled with silver nanoparticles-decorated graphene

In this study, polyurethane (PU) was synthesized using 4,4,-diphenylmethane diisocyanate (MDI) as a hard segment, polycaprolactone diol (PCL) as the soft segments and 1,4-butandiol (1,4-BD) as a chain extender. Nanosilver/graphene (Ag/G) was added to the PU matrix to prepare Ag/G/PU nanocomposites. EDS, SEM and XRD are used for assaying the silver content and characterization of Ag/G. TEM, FT-IR, XRD and EDS were used to characterize the structure and morphology of the Ag/G/PUs nanocomposites. The TEM results show that Ag/G belongs to sheet structures and is dispersed in a PU matrix. The SEM showed that the strong interfacial adhesion between the Ag/G and PU is indicated. FT-IR spectra analysis shows that the functional group of PU is free of obvious changes by adding a small amount of Ag/G in the PU matrix. XRD results showed that the main crystalline peak (26°) of Ag/G became more apparent with increasing content of Ag/G, and EDS showed that the content of Ag increased with increasing content of Ag/G in the Ag/G/PUs nanocomposites. The thermal stability and mechanical properties of Ag/G/PUs nanocomposites are improved with increasing content of Ag/G. Contact angle and AFM results showed that the hydrophobicity and surface roughness increased with increasing content of Ag/G. Moreover, the Ag/G/PUs nanocomposites exhibit antibacterial activities toward Staphylococcus aureus as well as Escherichia coli and their antibacterial rates increase with increasing Ag/G. In addition, the electrical conductivity measurements showed that both surface and volume resistance of the Ag/G/PUs nanocomposites decreased as the amount of Ag/G increased.

Preparation and Characterization of Polysulfone/Nanosilver-Doped Activated Carbon Nanocomposite

In this study, nano silver-doped activated carbon (Ag/C) acted as an inorganic additive and was blended with a polysulfone (PSF) matrix in a tetrahydrofuran (THF) solution, thereby forming nano silver- doped activated carbon/polysulfone (Ag/C/PSF) composites. Subsequently, the silver content and characterization of the Ag/C were identified using energy-dispersive X-ray spectroscopy (EDS), scanning electron microscopy (SEM), and X-ray diffraction (XRD). The FTIR, XRD, EDS and SEM were used to characterize the structure and morphology of the Ag/C/PSF composites. The FTIR spectra analysis revealed that adding a small volume of Ag/C in a PSF matrix did not substantially affect the functional groups of the matrix. The XRD results showed that the characteristic crystallization peaks of Ag/C/PSF (2θ = 26°) increased as the Ag/C content increased. The EDS results revealed that silver elements were inlaid into Ag/C/PSF composites, and the SEM results demonstrated strong interfacial interaction between the Ag/C particles and PSF matrix. The results of thermogravimetric analysis and differential scanning calorimetry appeared that adding Ag/C particles increased the thermal decomposition temperature and glass transition temperature of the Ag/C/PSF composites. From a stress–strain analysis, the added Ag/C particles enhanced the tensile strength of the PSF matrix. The results of contact-angle and atomic-force microscopy measuring showed that the hydrophobicity and surface roughness increased when Ag/C content increased. The antibacterial test results revealed that the Ag/C/PSF composites exhibited excellent antibacterial activity against both Staphylococcus aureus and Escherichia coli. In addition, the electrical conductivity measurements showed that volume resistivity of the Ag/C/PSF composites decreased with the amount of Ag/C increase.

Biodegradable polyurethanes: novel effects of the fluorine-containing chain extender on the thermal, physical and water vapor permeation properties

This study synthesized a novel fluoro chain extender, namely 2,2,3,3,4,4,4-heptafluoro-butynic acid 2,2-bis-hydroxymethyl-butyl ester (HFBA), by using 2,2,3,3,4,4,4-heptafluorobutanoyl chloride and trimethylolpropane. Novel polyurethanes (PUs), namely HFBA/PUs, were subsequently synthesized by adopting a hard segment (4,4′-diphenylmethane diisocyanate, MDI), a soft segment (polycaprolactone diol, PCL), and the synthesized chain extender (HFBA). The results of proton nuclear magnetic resonance spectroscopy, fluorine-19 nuclear magnetic resonance, and Fourier transform infrared spectroscopy (FT-IR) demonstrated the successful synthesis of the HFBA chain extender. Gel permeation chromatography revealed that the molecular weight of the HFBA/PUs increased with the HFBA content. Through FR-IR and X-ray photoelectron spectroscopy, we observed a strong hydrogen bond interaction between the NH groups and CF2 or CF3 groups in the HFBA/PUs. This interaction increased with the HFBA content. Additionally, increasing the HFBA content increased the initial decomposition temperature, glass transition temperature, dynamic Tg (Tgd), tensile strength, and Young’s modulus of the HFBA/PUs. These results were because HFBA was a hard segment, which stimulated a stronger interaction between the NH groups and CF2 or CF3 groups in the PUs. By contrast, the HFBA/PUs had low elongation-at-break values. Atomic force microscopy revealed a higher number of bump-like protrusions and higher surface roughness levels among HFBA/PUs with higher HFBA content ratios. Finally, we coated the HFBA/PUs onto polyethylene terephthalate fabrics and discovered that the coated fabrics demonstrated high waterproofing and water vapor permeability levels.

Isothermal Crystallization Kinetics Effect on the Tensile Properties of PLA/PTT Polymer Composites

A poly(lactic acid)/poly(trimethylene terephthalate) (PLA/PTT) composite was prepared by melt blending to improve the PTT crystallization rate. Morphology analysis of PLA/PTT fractured surfaces demonstrated the compatibility of its components. Thermogravimetric analysis revealed that the thermodegradation of a PLA/PTT sample was higher than that of PLA. Differential scanning calorimetry was used to evaluate the crystallization behavior. The Avrami equation described the isothermal crystallization kinetics. The Hoffman–Weeks parameters indicated that the PLA presence increased slightly the PTT nucleation. The tests of PLA, PTT, and PLA/PTT specimens in tension showed that a percent elongation of the PLA/PTT composite was between that of PLA and PTT; however, the tensile strength of the PLA/PTT composite was similar to that of PLA.