The poly(lactic acid)/clay nanocomposites (PLACNs) were prepared by melt mixing method, then multiepoxide chain extender (CE) was added into PLACNs to induce the branched structure of poly(lactic acid) (PLA) chains. The nonisothermal cold crystallization and isothermal melting crystallization of PLA, PLACNs, and chain extended PLACNs (CEPLACNs) were characterized by DSC and studied by Avrami analysis. The results showed that the inducing of clay and CE affected the crystallization behavior of PLA in different way. Adding CE increased the overall crystallinity of PLA at cooling process, but clay had an opposite effect. Besides that, the addition of CE and clay increased the crystal nuclei number due to the heterogeneous nucleation mechanism. According to the crystallization kinetics study, the inducing of clay almost no effect on the crystal growth rate of PLA, but the branched structure had a pronounced effect for improving crystal growth rate of PLA. POLYM. COMPOS., 36:2123–2134, 2015. © 2014 Society of Plastics Engineer

Polyethylenimine (PEI) is a promising candidate for CO₂ capture. In this work, the physisorption and chemisorption of CO₂ on various low-molecular-weight PEIs are investigated to identify the effect of chain architecture on sorption. The reliability of theoretical calculations are partially supported by our experimental measurements. Physisorption is calculated independently by the reference interaction-site model integral equation theory; chemisorption is distinguished from the total sorption given by the quantum density functional theory. It is shown that, as the chain length increases, both chemisorption and physisorption drop off nonlinearly, but the decay amplitude of chemisorption is more apparent. Conversely, as the amine group approaches the central triamine unit of each oligomer, the sorption capacity decreases, affecting the sorption equilibrium in a complex way. This arises from the cooperative contribution of an increased steric effect and renormalized electronic distribution.

A methodology for preparing porous polysulfone (PSF) monolith via concentrated emulsion templating was proposed. A regular emulsion was first prepared using a solution of PSF in chloroform as the continuous phase and deionized water as the dispersed one. After the emulsion was formed, the liquid species in the emulsion was allowed to be evaporated. The solvent chloroform was first removed and the emulsion was transformed to a concentrated emulsion. Further removing the aqueous species, a porous PSF monolith was obtained. To keep the system stable throughout the process, an aminated polysulfone rather than conventional surfactants was employed. The effects of chloroform and water fractions, the nature and loading of the macromolecular surfactant, the evaporating temperature on the pore structure were investigated. Controlled porous structure with different pore size and porosity could be obtained through the method. POLYM. ENG. SCI., 2011. © 2010 Society of Plastics Engineers.

The engineering application of poly(ethylene terephthalate) (PET) was limited by its low melt viscosity and strength. Numerous chain extenders were used to enlarge the molecular weight so as to overcome these shortcomings including bisphenol-A dicyanate (BADCy), which was proven effective in one of our previous work. It was considered that tri-mer of BADCy through cyclotrimerization might strengthen the effectiveness in chain extender for PET, and the effect of BADCy tri-mer was studied in this work. With increasing the cyclotrimerization reaction temperature of BADCy monomer, the conversion to tri-mers was increased. With a fraction of BADCy tri-mer in the chain extender, the modified PET exhibited higher melt torque, intrinsic viscosity, melt modulus, and melt viscosity than those modified by BADCy monomer alone. BADCy tri-mer had a positive effect on the chain extension of PET. However, the fraction of tri-mers in the monomer/tri-mer mixture should be limited to a certain value; otherwise, the chain extension would be weakened. POLYM. ENG. SCI., 2011. © 2011 Society of Plastics Engineers

Chain extension of poly(ethylene terephthalate) (PET) with bisphenol-A dicyanate (BADCy) was studied using an internal mixer under reactive blending conditions. The reaction between PET and BADCy was confirmed by Fourier transform infrared (FTIR) and chemical titration. With increasing amount of BADCy introduced, the modified PET gave rise to higher torque during stirred in an internal mixer, higher viscosity (η′), and higher storage modulus (G′). Measurement of intrinsic viscosity showed that BADCy indeed extended the molecular weight of PET. DSC analysis represented that T_m and T_c of the modified PET were shifted to low temperatures. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010

Fe₃O₄ nanoparticles were indirectly implanted onto functionalized multi-walled carbon nanotubes (MWCNTs) leading to a nanocomposite with stronger magnetic performance. Poly(acrylic acid) (PAA) oligomer was first reacted with hydroxyl-functionalized MWCNTs (MWCNTs-OH) forming PAA-grafted MWCNTs (PAA-g-MWCNTs). Subsequently, Fe₃O₄ nanoparticles were attached onto the surface of PAA-g-MWCNTs through an amidation reaction between the amino groups on the surface of Fe₃O₄ nanoparticles and the carboxyl groups of PAA. Fourier transform infrared spectra confirmed that the Fe₃O₄ nanoparticles and PAA-g-MWCNTs were indeed chemically linked. The morphology of the nanocomposites was characterized using transmission electron microscope (TEM). The surface and bulk structure of the nanocomposites were examined using X-ray diffraction, X-ray photoelectron spectrometer (XPS), and thermogravimetric analysis (TGA). The magnetic performance was characterized by vibrating sample magnetometer (VSM) and the magnetic saturation value of the magnetic nanocomposites was 47 emu g⁻¹. The resulting products could be separated from deionized water under an external magnetic field within about 15 s. Finally, the magnetorheological (MR) performances of the synthesized magnetic nanocomposites and pure Fe₃O₄ nanoparticles were examined using a rotational rheometer. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2010

A methodology for reinforcement of liquid ethylene–propylene–dicyclopentadiene copolymer (liquid-EPDM) based elastomer with multiwalled carbon nanotubes (MWCNTs) was proposed. Acid-treated MWCNTs were first reacted with poly(acryloyl chloride) (PACl) leading to a grafted encapsulation, which were subsequently reacted with hydroxy ethyl acrylate (HEA) to generate vinyl groups. Thus obtained vinyl groups functionalized MWCNTs (vinyl-MWCNTs) were characterized using Fourier transform infrared spectroscopy, transmission electron microscopy, and thermogravimetric analysis. The vinyl-MWCNTs were blended with liquid-EPDM and subjected to co-curing; an intercrosslinked structure was obtained via the free radical polymerization among the vinyl groups on vinyl-MWCNTs and the double bonds on liquid-EPDM. As a result, the vinyl-MWCNTs and the cured EPDM matrix were covalently linked. The chemical interfacial interaction between vinyl-MWCNTs and the cured matrix were observed by scanning electron microscope, which provided obvious reinforcement of elastomer. POLYM. ENG. SCI., 2010. © 2010 Society of Plastics Engineers

Crude silica was modified with silsisquioxane (SSO), which was originated from vinyltriethoxysilane, leading to modified silica. The modified silica with vinyl groups was employed to reinforce polydimethylsiloxane (PDMS) through participating in the hydrosilation reaction. Inorganic–organic hybrid network was formed to obtain higher mechanical properties. Fourier transformation infrared spectroscopy (FTIR) confirmed that the vinyl groups were bonded to the surface of silica. Transmission electron microscopy (TEM) showed that the diameter of the modified silica increased and the shape became irregular. The effects of the amount of SSO, the loading of modified silica, and the vinyl/hydrogen mole ratio on the mechanical properties of the cured PDMS system were investigated. It was found that 40 parts of SSO could result in a sufficient surface modification of the silica. The tensile strength and the modulus (reflected by the stress at 100% elongation) kept increasing with increasing loading of silica. When the vinyl/hydrogen mole ratio was 1:1, the most effective reinforcement was obtained. POLYM. ENG. SCI., 48:74–79, 2008. © 2007 Society of Plastics Engineers