Shuidong Zhang

Mechanical Properties and Morphology of Poly(l-Lactic acid)/Nano-CaCO3 Composites

The tensile and impact properties of poly(l-lactic acid) composites filled with nanometer calcium carbonate (nano-CaCO3) were measured at room temperature. The results showed that the tensile elastic modulus increased roughly linearly while the tensile yield strength, tensile fracture strength and tensile elongation at break (δb) decreased nonlinearly with increasing the nano-CaCO3 weight fraction (Wf); when Wf was constant, the δb increased with increasing tensile rates. Both the V-notched Izod impact strength and V-notched Charpy impact strength showed the non-linear increase with increasing Wf. The impact fracture surface was observed by means of a scanning electronic microscope to understand the toughening mechanisms.

Influence of Starch Oxidization and Modification on Interfacial Interaction, Rheological Behavior, and Properties of Poly(Propylene Carbonate)/Starch Blends

ABSTRACT The enhanced maleic anhydride-end-capped poly(propylene carbonate)/starch blends were prepared through starch oxidization and modification with a coupling agent, aluminic ester. The interfacial interaction, rheological behavior, and properties of blends were investigated through Fourier transform infrared spectroscopy, rheological measurement, mechanical property test, differential scanning calorimetric, thermogravimetric analysis, and moisture absorption test. The results show that hydrogen-bonding interaction is formed between poly(propylene carbonate) and starch, which makes the tensile strength of maleic anhydride-end-capped poly(propylene carbonate)/starch blends improved significantly. The glass transition temperature (Tg) of blends is increased when coupling agent is induced into polymer system. When increasing the content of starch modified with coupling agent from 10 to 30%, Tg values for composites increased from 30.5 to 32.8°C. Thermogravimetric analysis results show that oxidation of starch can improve the thermal stability and modification of starch through aluminic ester that can further increase the thermal stability of maleic anhydride-end-capped poly(propylene carbonate)/starch blends. Oxidation of starch has no significant effect on moisture absorption for poly(propylene carbonate)/starch blends. GRAPHICAL ABSTRACT

Structure, and thermal and mechanical properties of poly(propylene carbonate) capped with different types of acid anhydride via reactive extrusion

Three types of anhydride (maleic anhydride (MA), phthalic anhydride (PA) and pyromellitic dianhydride (PMDA)) were melt blended to end-cap poly(propylene carbonate) (PPC) by reactive extrusion. The effect of anhydride types on thermal, rheological, and mechanical properties of PPC was investigated. Results of FTIR spectra, Raman spectra and GPC indicate that the reaction mechanism between PPC with MA was different from PPC with PA and PMDA. During the extrusion processing in the presence of MA, end capping occurs for the free polymer ends and reduces chain depolymerization in a conventional way. For PA and PMDA, some non-covalent interaction may exist and it is deduced that hydrogen bonding may occur. In addition, TGA results show that the thermal degradation temperature of PPC could be improved by adding three types of anhydride, and the T−5% of PPC–PMDA was the highest and increased by 26.3 °C. The tensile strength and Youngs modulus of PPC is also improved with the addition of MA, PA and PMDA. Moreover, the value of elongation at break of all end-capped PPC still can remain higher than 1000%.

Superhydrophobic SiC/CNTs Coatings with Photothermal Deicing and Passive Anti-Icing Properties

For faster and greener anti-icing/deicing, a new generation of anti-icing materials are expected to possess both passive anti-icing properties and active deicing properties. The photothermal effect of carbon nanotubes (CNTs) is used in the field of photothermal cancer therapy, while the application in anti-icing/deicing is seldom investigated. Superhydrophobic SiC/CNTs coatings with photothermal deicing and passive anti-icing properties were first prepared by a simple spray-coating method. The results of 3D profile and microstructure observed via scanning electron microscopy demonstrate that the micronanostructure combined with peaklike SiC microstructure and villiform CNTs nanostructure makes the coatings surface superhydrophobic, exhibiting a water contact angle of up to 161° and a roll angle as low as 2°. This micronanostructure can also reduce ice anchoring and ice adhesion strength. Utilizing the photothermal effect of CNTs, the surface temperature of the coatings is rapidly increased upon near-infrared light (808 nm) irradiation. The heat is transferred rapidly to the surroundings by highly thermal conductive CNTs. The light-to-heat conversion efficiency in deicing tests is approximately 50.94%, achieving a highly efficient remote deicing effect. This superhydrophobic coating combining photothermal deicing and passive anti-icing properties is expected to be further used in various practical applications and in development of a new generation of anti-icing/deicing coatings.

Effect of Processing Methods on the Properties of Poly(lactic Acid)/Acetylated Starch Blends

Poly(lactic acid)/acetylated starch (PLA/AS) blends was prepared using a twin-screw extruder and two different types of single-screw extruder, respectively. One of the single-screw extruder was combined with conveying screw elements, providing shearing mixing, and the other with conveying screw elements and chaotic mixing screw elements, providing both shearing and chaotic mixing. To investigate the effect of processing methods on the rheological, thermal, and mechanical properties of PLA/AS blends, intrinsic viscosity tests, dynamic oscillatory rheological measurement, thermal analysis, tensile tests, and scanning electron microscopy were employed. Results show that the screw configuration of the extruder has a major influence on the properties of PLA/AS blends. Compared with PLA/AS blends prepared on the twin-screw extruder and on the single-screw extruder with shear mixing, improved dispersion of AS in the PLA matrix is found in blends produced on the single-screw extruder with chaotic mixing. The reason is that the interaction between PLA and AS phases is enhanced by chaotic mixing during the process of extrusion, facilitating to improving the thermal stability and tensile strength of the blend.