Baoqing Shentu

Effect of Oleic Acid-modified Nano-CaCO3 on the Crystallization Behavior and Mechanical Properties of Polypropylene

Abstract Oleic acid (OA)-modified CaCO 3 nanoparticles were prepared using surface modification method. Infrared spectroscopy (IR) was used to investigate the structure of the modified CaCO 3 nanoparticles, and the result showed that OA attached to the surface of CaCO 3 nanoparticles with the ionic bond. Effect of OA concentration on the dispersion stability of CaCO 3 in heptane was also studied, and the result indicated that modified CaCO 3 nanoparticles dispersed in heptane more stably than unmodified ones. The optimal proportion of OA to CaCO 3 was established. The effect of modified CaCO 3 nanoparticles on crystallization behavior of polypropylene (PP) was studied by means of DSC. It was found that CaCO 3 significantly increased the crystallization temperature, crystallization degree and crystallization rate of PP, and the addition of modified CaCO 3 nanoparticles can lead to the formation of β-crystal PP. Effect of the modified CaCO 3 content on mechanical properties of PP/CaCO 3 nanocomposites was also studied. The results showed that the modified CaCO 3 can effectively improve the mechanical properties of PP. In comparison with PP, the impact strength of PP/CaCO 3 nanocomposites increased by about 65% and the flexural strength increased by about 20%.

Morphology, Rheology, and Mechanical Properties of Polylactide/Poly(Ethylene-co-octene) Blends

Polylactide (PLA)/poly(ethylene-co-octene) (POE) blends containing ethylene-glycidyl methacrylate copolymer (EGMA) as a compatibilizer were prepared by melt blending. An immiscible, two-phase structure with POE dispersed in the PLA matrix was observed by scanning electron microscopy. It was found that the POE particle size was significantly decreased by the addition of EGMA, and the POE particle size and distribution decreased with the increase of the compatibilizer content up to 2% EGMA, beyond which the POE particle size and distribution remained unchanged. The reactions between the epoxy groups of EGMA and carboxylic or hydroxyl groups of PLA were elucidated by the Fourier transform infrared spectroscopy. Rheological results showed that the G′(ω), G″(ω), and complex viscosity of PLA/POE blends significantly increased at low frequencies with the addition of EGMA. The failure mode changed from brittle fracture of the neat PLA to ductile fracture of the PLA/POE blends.

Preparation of a tetraphenylporphyrinatocobalt(II)-poly(3,4-azopyridylene) complex and its oxygen enrichment effect at an oxygen electrode

The reversible oxygen-binding properties of tetraphenylporphyrinatocobalt(II) (CoTPP) complexed with poly(3,4-azopyridylene) (PAP) were established. The CoTPP complexes functioned as oxygen carriers at the surface of a cathode to enhance the current for the reduction of oxygen. PAP was synthesized by the oxidative polymerization of 3,4-diaminopyridine in a DMF solution at 25 °C using a Cu/pyridine catalyst. The combination of the CoTPP complex and the conventional Pt/C catalyst resulted in a significant increase in the steady-state current for the four-electron reduction of O2, particularly at small overpotentials where typical fuel cells operate, based on the facilitated transport of O2 from the atmosphere to the catalyst at the electrode surface.

Thermal Degradation Behavior and Flame Retardancy of Polycarbonate Containing Poly[(phenylsilsesquioxane)-co-(dimethylsiloxane)] and Potassium Diphenyl Sulfonate

The synergistic effect of poly[(phenylsilsesquioxane)-co-(dimethylsiloxane)] (PPSQDS) and potassium diphenyl sulfonate (KSS) on the thermal degradation and flame retardancy of polycarbonate (PC) was studied. The flame retardancy of PC was improved by the combination of PPSQDS and KSS, and a V-0 rating for 1.6 mm thickness sample was successfully obtained. The thermal degradation of the flame retarded PC was characterized by thermogravimetric analysis (TGA) and the degradation activation energy (E a) was calculated according to the Kissinger and Flynn-Wall-Ozawa (F-W-O) methods. The E a value of PC was decreased by the combination of PPSQDS and KSS, indicating that the synergistic effect of PPSQDS and KSS facilitates the thermal degradation of PC and accelerates char formation.

MODIFICATION OF CeO2 AND ITS EFFECT ON THE HEAT-RESISTANCE OF SILICONE RUBBER

By means of the wet chemical surface modification, the surface of CeO2 was modified by vinyltrimethoxysilane (VTMS). Infrared spectroscopy was used to investigate the structure of the modified CeO2 and the result showed that VTMS has been attached onto the surface of CeO2. Effect of VTMS concentration on the active index of the modified CeO2 was also studied, and the result indicated that the active index of the modified CeO2 increases with the increase of VTMS concentration and the optimal concentration of VTMS is 10 wt%. The effect of the modified CeO2 on the tear strength of silicone rubber before and after aging was studied and it was found that in comparison with the unmodified CeO2 the addition of the modified CeO2 results in the significant increase of the tear strength before ageing due to the increase of the crosslinking density of silicone rubber under the experimental conditions. The tear strength of silicone rubber filled with the modified CeO2 after ageing is higher than that with the unmodif...

CRYSTALLIZATION AND MECHANICAL PROPERTIES OF POLYPROPYLENE FILLED WITH SiO2 NANOPARTICLES

Oleic acid (OA)-modified SiO2(OA-m-SiO2) nanoparticles were prepared using surface modification method. Infrared spectroscopy (IR) was used to investigate the structure of the OA-m-SiO2 nanoparticles, and the result showed that OA attached onto the surface of SiO2 nanoparticles through esterification. Effect of OA concentration on the dispersion stability of OA-m-SiO2 in heptane was also studied, and the result indicated that OA-m-SiO2 nanoparticles were dispersed in heptane more stably than the unmodified ones. OA-m-SiO2 nanoparticles can also be dispersed in polypropylene (PP) matrix in nano-scale. The effect of OA-m-SiO2 on crystallization of PP was studied by means of DSC. It was found that the introduction of OA-m-SiO2 resulted in significant increase in the crystallization temperature, crystallization degree and crystallization rate of PP, and OA-m-SiO2 could effectively induce the formation of β-crystal PP. Effect of OA-m-SiO2 content on mechanical properties of PP/OA-m-SiO2 nanocomposites was also...

Joint Effect of Compatibilizer and Organo-Montmorillonite on Compatibilization of Polyamide-6/Poly(phenylene oxide) Blend: Morphology and Properties

Compatibilizer (styrene–maleic anhydride copolymer, SMA) and organo-montmorillonite (OMMT) were introduced into immiscible polyamide-6 (PA6)/ poly(phenylene oxide) (PPO) blend to obtain quaternary nanocomposites simply by melt extrusion. OMMT tactoids formed in PA6/PPO/OMMT ternary blend would become smaller or disappear with the addition of SMA. Besides, viscosity of SMA compatibilized PA6/PPO blend decreased a lot with the addition of OMMT. Based on these results, a mechanism for joint effect of SMA and OMMT in compatibilizing PA6 and PPO was proposed. We further studied water absorption and tensile properties of the nanocomposites, which were in consistent with the proposed mechanism. GRAPHICAL ABSTRACT

One-pot synthesis of poly(2,6-dimethyl-1,4-phenylene oxide)/polystyrene alloy with CuCl2/4-dimethylaminopyridine as a versatile catalyst in water

A one-pot synthetic approach for the preparation of poly(2,6-dimethyl-1,4-phenylene oxide)/polystyrene (PPO/PS) alloy in aqueous medium was developed. The method was based on the combination of the oxidative coupling polymerization of 2,6-dimethylphenol (DMP) to form PPO in the presence of a reactive swelling agent, styrene (St), and in situ reverse atom transfer radical polymerization (RATRP) of St initiated by 2,2′-azobis[2-(2-imidazolin-2-yl)propane] dihydrochloride (AIBI) in alkaline aqueous solution. The complex of CuCl2 and 4-dimethylaminopyridine (DMAP) was utilized as the catalyst to catalyze the two types of polymerization mentioned above. Oxygen was employed as the sole oxidant to synthesize PPO. The introduction of St during the oxidative polymerization of DMP could increase the molecular weight of PPO. Finally thermodynamically compatible PPO/PS alloy was successfully prepared.

A Kinetic Study of the Thermal Degradation of Nylon-6/Attapulgite Nanocomposites

The thermal degradation behavior of nylon-6 (PA6) and PA6/attapulgite (ATP) nanocomposites was investigated by thermogravimetric analysis under non-isothermal conditions at various heating rates in nitrogen. It is suggested that during thermal degradation, ATP, as a protective barrier, can slow down degradation of polymer, but the catalytic effects of structural water and hydroxyl groups may accelerate the degradation of PA6. The combination of these two effects determined the final thermal stability of nanocomposites. The apparent activation energies of the samples were evaluated by the Kissinger and Flynn–Wall–Ozawa methods. The results showed that the presence of ATP adversely affected the thermal stability of PA6. The degradation activation energies of PA6/ATP nanocomposites decreased monotonically with increase in ATP content; thus, it is suggested that the ATP has a disadvantageous effect on the thermal stability of PA6.

OXIDATIVE POLYMERIZATION BEHAVIOR OF 2,6-DIMETHYLPHENOL IN AQUEOUS MEDIA WITH POTASSIUM FERRICYANIDE

The effects of potassium ferricyanide, sodium n-dodecyl sulfate, sodium hydroxide and temperature on the molecular weight and the yield of poly(2,6-dimethyl-1,4-phenylene oxide) (PPO) synthesized in an aqueous medium were studied. It was found that oxygen in air had little influence on the oxidative polymerization of 2,6-dimethylphenol (DMP) in the aqueous medium, and potassium ferricyanide was only an oxidant during the oxidative polymerization of DMP. Sodium n-dodecyl sulfate could stabilize polymer particles and facilitate the oxidative polymerization of DMP on the surface of polymer particles, which resulted in the increase of the molecular weight of PPO. The yield and molecular weight of PPO increased significantly with NaOH concentration at first and then decreased with NaOH concentration. The high molecular weight PPO with high yield was obtained at 50°C, but both the yield and molecular weight of PPO decreased with the further increase of temperature.