Influence of Block Copolymer on Formation and Acid Resistant Properties of Hybrid CaCO_3 Particles

Block copolymer polystyrene-b-poly（acrylic acid）（PS-b-PAA） was used as structural template for the synthesis of CaCO3 microparticles. Through this procedure, acid resistant hybrid CaCO3 micro- spheres were obtained. Acid resistant properties of this type of hybrid CaCO3 were studied. Size measurement shows that the acid resistant properties of the hybrid particles are different in different solutions, such as HCl, EDTA, and H2SO4 solutions.

“Cutting effect” of organoclay platelets in compatibilizing immiscible polypropylene/polystyrene blends

In this work, polypropylene (PP)/polystyrene (PS) blends with different organoclay concentrations were prepared via melt compounding. Differing from the results of previous reports, the organoclay platelets are mostly located in the dispersed PS phase instead of the interface. The dimensions of the dispersed PS droplets are greatly reduced and apparent compatibilization effect still exists, which cannot be explained by the traditional compatibilization mechanism. A novel compatibilization mecha- nism, "cutting" to apparently compatibilize the immiscible PP/PS blends was proposed. The organoclay platelets tend to form a special "knife-like structure" in the PS domain under the shear stress of the continuous PP phase during compounding. The "clay knife" can split the dispersed PS domain apart and lead to the dramatic reduction of the dispersed domain size.

Biomimetic Preparation of Magnetite/Chitosan Nanocomposite via In Situ Composite Method ——Potential Use in Magnetic Tissue Repair Domain

This study focused on the preparation of magnetic chitusan nanocompesite that has a potential application to bone repair and regeneration using an in situ composite method where chitosan membrane was used as the template and NaOH was used as the precipitant. X-ray diffraction analysis results show the formation of magnetite in the chitosan matrix. From the magnetic measurement, it could be concluded that the magnetic chitosan rods were superparamagnetic,and that this is the unique property of nanomagnetite. Macroscopical layer structure of the magnetic chitosan rods was observed from the photographs after mechanical test, and the microlayer structure of the rods was observed from the images of scanning electron microscopy. The mechanism for preparing the rods was discussed in detail. Transmission electron microscope was used to investigate the magnetite particles in the chitosan matrix and from the images it was concluded that the magnetite particles dispersed well in chitosan matrix with particle size of about 10 nm. The mechanical properties of the magnetic chitosan rods were measured and the blending strength was found to be 98. 8 MPa. The mechanical properties did not decline when compared with those of the pure chitosan materials.

Preparation and characterization of biodegradable aliphatic-aromatic copolyesters/nano-SiO_2 hybrids via in situ melt polycondensation

In situ melt polycondensation was proposed to prepare biodegradable aliphatic-aromatic copolyesters/nano-SiO2 hybrids based on terephthalic acid （TPA）, poly（L-lactic acid） oligomer （OLLA）, 1,4-butanediol （BDO） and nano-SiO2. TEM and FT-IR characterizations confirmed that TPA, OLLA and BDO copolymerized to obtain biodegradable copolyesters, poly（butylene terepbthalate-co-lactate） （PBTL）, and the abundant hydroxyl groups on the surface of nano-SiO2 provided potential sites for in situ grafting with the simultaneous resulted PBTL. The nano-SiO2 particles were chemically wrapped with PBTL to form PBTL/nano- SiO2 hybrids. Due to the good dispersion and interfacial adhesion of nano-SiO2 particles with the copolyester matrix, the tensile strength and the Young＇s modulus increased from 5.4 and 5.6 MPa for neat PBTL to 16 and 390 MPa for PBTL/nano-SiO2 hybrids with 5 wt.% nano-SiO2, respectively. The mechanical properties of PBTL/nano-SiO2 hybrids were substantially improved.

SYNERGISTIC MODIFICATION OF EPDM AND CROSSLINKING AGENT IN IMMISCIBLE BLENDS OF POLYVINYL CHLORIDE WITH LOW DENSITY POLYETHYLENE

The synergism of ethylene-propylene-diene monomer copolymer （EPDM） and dicumyl peroxide （DCP, a crosslinking agent） in low density polyethylene （LDPE）/poly（vinyl chloride） （PVC） blends was investigated. When EDPM and DCP are added to the blends simultaneously, the tensile properties could be improved significantly, especially for the blends with LDPE matrix. For example, incorporation of 10/1 （mass ratio） EPDM/DCP improves the tensile strength of the LDPE/PVC （mass ratio 80/20） blend from 7.9 MPa to 8.5 MPa and the elongation at break from 25% to 503%. Results from selective extraction, phase-contrast microscopy and thermal analysis reveal that the improvement in the tensile properties of the blends with LDPE matrix is principally due to the formation of a fine crosslinking network of the LDPE and EPDM phase. The outstanding modification effect of EPDM is explained by its dual functions： molecular entanglement with LDPE and the enhanced efficiency of DCP in the blends.

PREFERENTIAL INTERCALATION BEHAVIOR OF CLAY AND ITS EFFECT ON THE THERMAL DEGRADATION IN IMMISCIBLE PP/PS BLENDS

The typical immiscible PP/PS blend based clay nanocomposites were prepared via melt blending.The dispersion of clay was determined by X-ray diffraction (XRD) and transmission electron microscopy (TEM).Thermal stability and dynamic mechanical properties were measured by thermogravimetrical analysis (TGA) and dynamic mechanical analysis (DMA),respectively.Preferential intercalation behavior of clay in PP/PS blends was found.The dispersion of clay is significantly influenced by the polarity of PP and PS,meanwh...

Synthesis of Methyl-(γ-chloropropyl)dichlorosilane Catalyzed by Silica-supported Karstedt-type Catalyst

Methyl-（γ-chloropropyl）dichlorosilane was synthesized under the catalysis of a silicasupported Karstedt-type catalyst. By orthogonal experimental design method, the optimum reaction parameters such as reactants ratio, reaction temperature and time, and the dosage of catalyst, were determined. At the optimum reaction condition the product yield reached 78.42%, which is higher than that reported in the literatures.

Flame retarded polymer nanocomposites: Development,trend and future perspective

Polymer nanocomposites are a new class of flame retarded materials which have attracted much attention and considered as a revolutionary new flame retardant approach.A very small amount of nano flame retardants (normally < 5 wt%) can significantly reduce the heat release rate (HRR) and smoke emission (SEA) during the combustion of polymer materials.Moreover,the addition of nano flame retardants can also improve the mechanical properties of polymer materials compared with the deterioration of traditional flame retardants.This paper reviews the recent development in the flame retardant field of polymer nanocomposites and also introduces the related research in our lab.The challenges and problems are discussed and the future development of flame retarded polymer nanocomposites is prospected.

A METHOD TO QUANTIFY CRAZING DEFORMATION BY TENSILE TESTS FOR POLYSTYRENE/POLYOLEFIN ELASTOMER IMMISCIBLE BLENDS

A method to quantify crazing deformations by tensile tests for polystyrene （PS） and polyolefin elastomer （POE） blends was investigated. The toughness of PS/POE blends, reflected by the Charpy impact strength, increased with the content of POE. SEM micrographs showed the poor compatibility between PS and POE. In simple tensile tests, it is very easy to achieve the ratio of crazing deformation, i.e. K by measuring the size changes of samples. The K values decreased with increasing the content of POE, and the deformations of PS/POE blends were dominated by crazing. The plots of the change of volume （△V） against longitudinal variation （△I） showed a linear relationship, and the slope of lines decreased with the content of POE. Measuring samples at the tensile velocities of 5 mm/min, 50 mm/min, and 500 mm/min respectively, the K values kept unchanged for each PS/POE blends.

DYNAMICS OF α AND α' RELAXATION IN LAYERED SILICATE/POLYSTYRENE NANOCOMPOSITES STUDIED BY ANELASTIC SPECTROSCOPY

The dynamics of polymer chains in layered silicate/polystyrene nanocomposites was studied by anelastic spectroscopy. Two thermal activated peaks （or and α＇ peaks） appeared when the specimens were heated to a high temperature and they were related to glass transition and liquid-liquid transition, respectively. The activation energy was calculated based on Arrhenius equation and it showed that the activation energy of glass transition （Eg） is much higher than that of liquid-liquid transition （EH）. Furthermore, the most interesting result for the activation energy was that there were two contrary trends for Eg and Ell, Eg decreased and Ell increased with the addition of clay platelets. The fragile parameter was analyzed and the variation of fragile parameters for the two transitions was also contrary to each other with the addition of clay platelets. All the results indicated that the confinement effect of clay platelets on the dynamics of polymer chain was scale dependent, and perhaps, the two transitions were produced by different mechanisms.

BIODEGRADABLE ALIPHATIC/AROMATIC COPOLYESTERS BASED ON TEREPHTHALIC ACID AND POLY(L-LACTIC ACID):SYNTHESIS,CHARACTERIZATION AND HYDROLYTIC DEGRADATION

Biodegradable aliphatic/aromatic copolyesters, poly（butylene terephthalate-co-lactate） （PBTL） were prepared via direct melt polycondensation of terephthalic acid （TPA）, 1,4-butanediol （BDO） and poly（L-lactic acid） oligomer （OLLA）. The effects of polymerization time and temperature, as well as aliphatic/aromatic moiety ratio on the physical and thermal properties were investigated. The largest molecular weight of the copolyesters was up to 64100 with molecular weight distribution index of 2.09 when the polycondensation was carried out at 230℃ for 6 h. DSC, XRD, DMA and TGA analysis clearly indicated that the degree of crystallinity, glass-transition temperature, melting point, decomposition temperature, tensile strength, elongation and Young＇s modulus were influenced by the ratio between TPA and OLLA in the final copolyesters. Hydrolytic degradation results demonstrated that the incorporation of biodegradable lactate moieties into the aromatic polyester could efficiently improve hydrolytic degradability of the copolymer even though it still had many aromatic units in the main chains.

Flame-retardant Coating by Alternate Assembly of Poly(vinylphosphonic acid) and Polyethylenimine for Ramie Fabrics

A novel intumescent flame retardant coating, consisting of poly（vinylphosphonic acid） （PVPA） as the acid source and branched polyethylenimine （BPEI） as the blowing agent, was constructed on the surface of ramie fabrics by alternate assembly to remarkably improve the flame retardancy of ramie. The PVPA/BPEI coating on the surface of individual fibers of ramie fabric pyrolyzes to form protective char layer upon heating/burning and improves the flame retardancy of ramie. Thermogravimetric analysis reveals that the PVPA/BPEI-coated ramie fabrics left as much as 25.8 wt% residue at 600 ~C, while the control （uncoated） fabric left less than 1.4 wt% residue. Vertical flame test shows that all PVPA/BPEI-coated fabrics have shorter after-flame time, and the residues well preserved the original weave structure and fiber morphology, whereas, the uncoated fabric left only ashes. Microscale combustion calorimetry shows that the PVPA/BPEI coatings greatly reduce the total heat release by as much as 66% and the heat release capacity by 76%, relative to those of the uncoated fabric.