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This study aims to develop highly hygroscopic bio-based co-polyamides (CPs) by melt co-polycondensation of polyamide (PA) 56 salt and PA66 salt with varying molar fractions. The functional groups and the chemical structure of the prepared samples were determined by Fourier transform infrared (FTIR) spectroscopy and proton nuclear magnetic resonance (¹H-NMR) spectroscopy. The relative viscosity was determined with an Ubbelohde viscometer. The melting behavior and the thermal stability of CPs were investigated by differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). Furthermore, the water absorption behavior of CP hot-pressed film was studied. The results reveal that the melting point, the crystallization temperature and the crystallinity of CPs firstly decrease and then increase with the molar fraction of PA66 in CPs. The copolymerization of PA56 with PA66 leads to an obvious increase in water absorption. The CPs with PA66 molar fraction of 50% possess a high saturated water absorption rate of 17.6%, compared to 11.6% for pure PA56 and 7. 8% for pure PA66. [ABSTRACT FROM AUTHOR]

The effect of PBAT (poly(butylene adipate-co-terephthalate)) content and crystallization temperature on the crystallization and heat resistance of PLLA/PDLA blends are studied. The PBAT/PLLA/PDLA blends with different PBAT content were prepared by melt blending. Then, differential scanning calorimetry (DSC) and Vicat softening temperature (VST) were used to investigate the semicrystallization time (t1/2), crystallinity and heat resistant of the blends. The results show that the incorporation of PBAT is benefit to the rate of crystallization and t1/2 of the blends can be reduced from 1.0 min to 0.8 min at 100 °C. After annealing at 220 °C, the degree of stereo-complex (fsc), stereocomplex crystallinity (Xc,S) and VST of PLLA/PDLA blends reaches up to 100.0%, 31.1% and 204 °C, respectively. The values of the former parameters reduce to 96.0%, 15.4% and °C 194 °C after incorporating 12% PBAT. It concludes that the crystallization under high temperature contributes to the improvement of Xc,S and heat resistance. The incorporation of PBAT into PLLA/PDLA promotes the crystallization rate, while it reduces the heat resistance of the blends [ABSTRACT FROM AUTHOR]

PVDF/SiO hybrid membranes with outstanding antifouling property were prepared from PVDF/glycerol triacetate system via thermally induced phase separation method, and characterized by scanning electron microscope, energy dispersive X-ray spectrometer analyses, differential scanning calorimeter, and wide angle X-ray diffraction. Their properties such as permeability, porosity, pore size distribution, and mechanical performance were also determined. The results show that SiO nanoparticles modified by 3-aminopropyltriethoxysilane can be uniformly dispersed in membranes due to improved compatibility between PVDF solution and nanoparticles. The addition of SiO particles to PVDF/glycerol triacetate mixture has a strong effect on crystallinity of the resulting hybrid membrane, which does not affect the type of PVDF crystal structure. Water flux recovery ratio is significantly increased from 11.7 % for pure PVDF membrane to 93.8 % for PVDF/SiO hybrid membrane with addition of 8 wt% modified SiO. This remarkable promotion is related to the implantation of SiO nanoparticles into the inner surface of membrane, which effectively restrains the adsorption of bovine serum albumin on the pore walls and improves antifouling property of the final membranes. Additionally, pure water flux of the hybrid membrane is increased by 276 %, i.e., from 85 to 320 L m h, tensile strength is increased by 26.5 %, and elongation at break is increased by 85.4 % compared with that of pure membrane. [ABSTRACT FROM AUTHOR]

With bio-renewable and environmentally friendly nature, biobased polyamides have emerged as attractive alternatives to traditional petroleum-derived polymers. However, poor thermal and mechanical performance, high costs, and limited scalability significantly hinder their practical applications. Herein, a series of biobased copolyamides PA6/PA56 (CoPAs) were successfully synthesized from caprolactam, adipic acid, and the lysine-derived biobased monomers 1,5-pentanediamine. The copolyamides were characterized by gel permeation chromatography (GPC), nuclear magnetic resonance spectroscopy (1H NMR), wide-angle X-ray diffraction (WAXD), differential scanning calorimetry (DSC), dynamic mechanical analysis (DMA), thermogravimetric analysis (TGA), rheological analysis, mechanical testing, and scanning electron microscopy (SEM). The result shows the α to γ transition in the crystalline form of the copolyamides with comonomer loading. The melting temperature, crystallization temperature, and crystallinity gradually decrease due to the introduction of the odd-even structure, causing deviation in amide positions and reducing hydrogen bond formation between molecular chains. Furthermore, variable-temperature infrared (VTIR) analysis and density functional theory (DFT) calculations further confirm a decrease in intermolecular forces. Importantly, the mobility of the molecular chains in the amorphous region is significantly improved, endowing the copolyamides with sufficient degrees of freedom to cope with externally applied strains. Moreover, significant entanglement facilitates effective stress transfer during stretching. As a result, the synthesized copolyamides achieve a high strength of 51 MPa and a remarkable toughness of 199 MJ/m3, without sacrificing thermal stability and processing properties. These biobased CoPAs show great potential and prospects in the field of high-performance thermoplastic materials, films, and textiles. [Display omitted] • Hydrogen bonding decreased with the introduction of the odd-even structure. • The massive entanglements formed within the copolyamides effectively transferred the stress. • The mechanical properties of biobased copolyamides were remarkably enhanced. [ABSTRACT FROM AUTHOR]