Mingcai Chen

Epoxy resins toughened by poly(propylene carbonate)

Poly(propylene carbonate) (PPC) was used as a toughening agent for improving the brittleness of cured epoxy resins (EP). Methyl tetrahydrophthatic anhydride (MTHPA) was used as a curing agent. The activation energies for the reactions of PPC/MTHPA and EP/MTHPA measured by FTIR were 115.8 and 66.5 kJ/mol, respectively, while for the composite system of PPC/EP/MTHPA, the activation energy obtained from DSC was 52.9 kJ/mol. Gel contents, DMA, and DSC displayed that the cured resins of PPC/EP/MTHPA were phase-separation crosslinking systems and most of PPC could react with MTHPA or the epoxy group. The toughness of cured resins was reinforced by the addition of PPC. The optimum mechanical properties and toughness for cured resins of PPC/EP/MTHPA corresponded to the system containing 20 phr PPC, which achieved a 33% increase in tensile strength and a 45% increase in the fracture toughness at no expense of the elongation of cured resins.

Studies on miscibility of poly(phenylene oxide)-based ionomer/polystyrene-based ionomer blends

The phase behavior of series of blends obtained from mixing carboxylated poly(phenylene oxide) with sulfonated polystyrene and their respective neutralized ionomers was studied by differential scanning calorimetry. A substantially broader range of miscibility was observed when both blend components were functionalized, compared with blends in which only one of the components contained an acid group or was an ionomer. The properties of metallic cations which were used to neutralize the acid groups in the blends were found to have an effect on the miscibility. The miscibility of the two acid polymers or their ionomers depended on the difference of their functionalization level instead of on the absolute percentage of functional groups on each polymer. It was found that the two acid polymers or their ionomers remained miscible as long as they had a similar percentage of functional groups.

Studies on the blends of carbon dioxide copolymer. III. NBR/PPC systems

In this paper, the blends of the carbon dioxide copolymer, poly(propylene carbonate) (PPC), with nitrile rubber (NBR) were studied by DSC, DMA, TEM and TG. PPC can enhance the mechanical properties of NBR, while oil resistance and tensile set at break of NBR/ PPC systems were as good as that of NBR. The coagent of triallylisocyanurate or maleic anhydride with carbon black can much improve the curing efficiency of dicumyl peroxide in NBR/PPC systems.

Siloxane-modified poly(acrylic acid) synthesized in supercritical CO2

Copolymerization of acrylic acid and 3-[tris(trimethylsilyloxy)silyl]propyl methacrylate (TMSPMA) in supercritical carbon dioxide was successfully carried out. The products were obtained in the form of dry white powder with diameter about 0.2 μm. Viscosities of 2% aqueous solution of the copolymers dramatically increased as the content of TMSPMA in the copolymer increased and it was much higher than that of poly(acrylic acid). In addition, the viscosity of the copolymers showed a strong dependence on pH with a maximum at pH 5.0, which is due to the cooperation of intermolecular association and electrostatic repulsion.

In‐situ composite based on polypropylene and nylon6

Polypropylene (PP) and Nylon6 were extruded with a single screw extruder. Nylon6 could form microfibrils in a PP matrix. When the blends were compression-molded at the temperature between the melting temperature of PP and that of Nylon6, these fibrils could be maintained in the matrix. The existence of Nylon6 microfibrils could improve the impact strength, but the tensile strength of the composites decreased. Differential scanning calorimetry (DSC) analysis show that Nylon6 microfibrils could affect the crystallization of PP slightly.

Absorption of low molecular weight solutes into polyurethane in supercritical carbon dioxide

Absorption of a series of low molecular weight solutes into polyurethane was investigated in supercritical carbon dioxide with different conditions. The effect on the amount of solutes absorbed in polyurethane due to these factors such as pressure, temperature, absorption time, decompression time, the character of solutes, and the amount of cosolvent was examined by a gravimetric method. The absorption mechanism was discussed. The desorption of solutes in polyurethane showed a dependence on the logarithm of time.