Jing Hua

Study on Preparation and Properties of HVBR Reinforced with Si69-modified Carbon Nanotubes

ABSTRACT Si69-modified CNTs/HVBR nanocomposites were prepared in dependence of different loadings of Si69-modified CNTs fabricated by mixing acid-treated CNTs with Si69 in toluene. FT-IR analysis illustrated the successful modification of CNTs. Experimental results showed that the Si69-modified CNTs could more significantly enhance the mechanical strength and thermal conductivity of the composites than the unmodified CNTs, indicating the Si69-modified CNTs could be more uniformly dispersed in the HVBR matrix, which was also verified form the SEM results. The DMA results indicated that the incorporation of Si69-modified CNTs could remarkably increase the glass transition temperature and decrease the height of the tanδ peak. GRAPHICAL ABSTRACT

m -Cresol-substituted triethyl aluminum/MoCl 5 /TBP catalytic system for coordination polymerization of butadiene

Coordination polymerization of butadiene was initiated by a catalyst system consisting of tributyl phosphate (TBP) as ligand, molybdenum pentachloride as primary catalyst and triethyl aluminum substituted by m-cresol as co-catalyst. The effects of the substitution of m-cresol on the activity of the catalyst system, molecular weight and molecular weight distribution, intrinsic viscosity and microstructures of the resulting polymers were investigated in details. The molecular weight and molecular weight distribution of the polymerization products were determined by GPC. The microstructure of the polymerization products was characterized by FTIR, 13C NMR and DSC techniques. The experimental results indicated that the polymerization activity of the reaction system and the molecular weight of the polymerization products gradually increased with the increase of the substitution content of m-cresol, namely, Al(OPhCH3)2Etu2009>u2009Al(OPhCH3)Et2u2009>u2009Al(OPhCH3)0.5Et2.5>AlEt3. The 1,2-structure contents of the polymerization products could be adjusted between 89 and 91% through the control of the substitution of m-cresol, and there was minute quantities of crystalline structures in the resulting polymers due to the increasing content of the syndiotactic 1,2-polybutadiene. In a word, the existence and increase of steric hindrance of m-cresol made it easier for polymerization products to form interdisciplinary 1,2-structure.

Ring-opening polymerization of l-lactide catalyzed by a novel molybdenum-based catalytic system

As a transparent material that can be completely biodegradable, poly(l-lactide) (PL-LA) has recently received considerable attention. In this study, it our first efforts to fabricate l-lactide (L-LA) by a novel molybdenum-based catalytic system consisting of molybdenum pentachloride (MoCl5) as the main catalyst and m-cresol substituted alkyl aluminum Al(OPhCH3)(i-Bu)2 as the co-catalyst. The effects of different types of phosphorus ligands, Al:Mo molar ratios, catalyst contents,catalyst components (separate catalysis of m-cresol aluminum and cocatalysis of Al/Mo system) and polymerization temperature were investigated. The Tg and Tm of the resulting poly(l-lactide) (PL-LA) were characterized by differential scanning calorimetry (DSC), and the molecular weight and molecular weight distribution were determined by gel permeation chromatography (GPC). The GPC results showed that the molecular weight of the PL-LA was higher than that 104 g/mol and the molecular weight distribution was narrow. The structures of PL-LA was detected by 1H NMR spectroscopy (1H NMR) and X-ray diffraction (XRD) validation, which demonstrated that a moalr ratio of Mo/Al/l-lactideu2009=u20091:30:1000 showed the higher conversion rate and molecular weight. In comparison to the separate catalysis of m-cresol aluminum, the molecular weight of PL-LA prepared by the cocatalysis of Al/Mo system was slightly improved, and the molecular chains were relatively regular and the crystallinity was higher.