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.
Polylactide (PLA) was plasticized by polyethylene glycols (PEGs) with five different molecular weights (M w = 200-20,000 g/mol). The effects of content and molecular weight of PEG on the crystallization and impact properties of PLA were studied by wide-angle X-ray diffraction, differential scanning calorimetry, scanning electron microscopy, transmission electron microscopy, and V-notched impact tests, respectively. The results revealed that PEG-10,000 could significantly improve the crystallization capacity and impact toughness of PLA. When the PEG-10,000 content ranged from 0 to 20 wt%, the increases in both V-notched Izod and Charpy impact strengths of PLA/PEG-10,000 blends were 206.10% and 137.25%, respectively. Meanwhile, the crystallinity of PLA/PEG-10,000 blends increased from 3.95% to 43.42%. For 10 wt% PEG content, the crystallization and impact properties of PLA/PEG blends mainly depended upon PEG molecular weight. With increasing the M w of PEG, the crystallinity and impact strength of PLA/PEG blends first decreased and then increased. The introduction of PEG reduced the intermolecular force and enhanced the mobility of PLA chains, thus improving the crystallization capacity and flexibility of PLA.
Hydrogen peroxide was used to oxidize gelatinized starch to oxidized starch (OS) with degree of oxidation (DO) ranging from 0.096 to 0.554 depending on the H2O2/starch molar ratios used. Then glycerol was added to OS to produce thermoplastic oxidized starches (TPOS). Titrimetric determination of carboxyl and carbonyl groups, FT‐IR, 1H‐NMR and 13C‐NMR confirmed that at H2O2/starch molar ratios < 0.7, oxidized starch contained much more aldehyde than carboxyl groups, while at molar ratios up to 2.0, peroxide oxidation produced mainly carboxyl groups. Scanning electron microscopy (SEM) revealed that the oxidized starch particles (at DO 0.385) obtained a porous structure. The effect of DO on the structure and properties of OS, as well as mechanical properties and moisture resistance of TPOS was studied, respectively. With an increase in DO, the crystallinity, intrinsic viscosity and thermal stability of OS decreased markedly, the ability of OS to take up water decreased at low DO and increased at higher DO. These observations show that hydrogen peroxide can be used to oxidize starch in a controlled way. TPOS with DO 0.385 showed the best mechanical properties, its tensile strength was 6.1 MPa after placing in 100% relative humidity for 15 days.
A novel method of starch modification was developed to obtain thermoplastic starch plastics with improved comprehensive properties. Corn starch was oxidized under mild conditions using sodium periodate to prepare dialdehyde starch, which had an acceptable average molecular weight. The dialdehyde starch with 35.2% carbonyl content was reacted with different alcohols (methanol, ethanol, and glycol) to prepare a series of novel starch derivatives, whose structures were characterized by 1H‐NMR and FT‐IR. The thermogravimetric analysis showed that these starch derivatives had an improved thermal stability compared with dialdehyde starch. Thermoplastic starch and its derivatives were prepared when water and glycerol were added as plasticizers. The modified thermoplastic starch and its derivatives had better mechanical properties than other modified starches, and lower humidity absorption than conventional thermoplastic starches. The highest tensile strength and elongation at break reached 17.5 MPa and 149%, respectively, and the highest humidity absorption was about 37%.
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