Kongying Zhu

Strategies for anti-icing: low surface energy or liquid-infused?

Anti-icing is of great importance in society since icing on facility surfaces may bring about serious disasters and economical losses in fields such as aerospace, transportation and electrical communication. Development of polymeric coatings with excellent anti-icing behaviours has been one of the practical topics in recent years. Control of the chemical compositions and topological surface structures is vital to anti-icing coatings. In this review, we summarize the recent progresses on polymeric anti-icing coatings prepared from low surface energy, hydrophilic or amphiphilic polymers. Surface characteristics of the anti-icing coatings including morphology, wettability and ice adhesion strength are discussed. Comparisons between representative studies, including low surface energy coatings and liquid-infused slippery surfaces will be highlighted, with emphasis on the polymer substrate properties and innovative aspects. This review is aimed at giving a brief and crucial overview of the strategies for preparation of icephobic coatings and fulfillment of the anti-icing behaviours.

Enhancement of icephobic properties based on UV-curable fluorosilicone copolymer films

UV-curable films composed of thiol-terminated fluorosilicone methacrylate triblock copolymers (PDMS-b-(PFMA-SH)2), thiol-functionalized PDMS (PDMS-SH) and octavinyl POSS (OVPOSS) were developed for the purpose of icephobic application. The PDMS-b-(PFMA-SH)2 copolymers were firstly synthesized via reversible addition–fragmentation chain transfer polymerization of dodecafluoroheptyl methacrylate (12FMA) or 2-perfluorooctylethyl methacrylate (17FMA), and followed by thiol-modification of the end groups. The results of differential scanning calorimetry and X-ray diffraction revealed the presence of perfluoroalkyl side groups in P17FMA as presented in the crystalline structure. These endowed the P17FMA-containing films with higher receding contact angles (100.2–113.5°) as compared with the P12FMA-containing films. In icephobicity investigations of the prepared films, it was found that the rebound of the impacting droplet was influenced by the receding contact angle, surface roughness, and temperature of the film surface. Water droplets could rebound from the horizontal and tilted (30° and 45°) P17FMA-containing film surfaces down to −15 °C, allowing surface dewetting before the water droplets froze, while the droplets adhered to the P12FMA-containing film surfaces. Moreover, the ice shear strengths of all the prepared film surfaces were lower than 210 kPa, only about 15% of the value on the bare aluminum surface. Therefore, P17FMA-containing UV-curable films could be a potential candidate for icephobic applications.

Preparation and Characterization of Melamine-Formaldehyde Resin Micro- and Nanocapsules Filled with n-Dodecane

Capsules containing phase change materials (PCMs) have been widely studied for applications in heat transfer, heat storage and temperature control. The average diameter of encapsulated PCMs usually has a large effect on the physical properties of these functional materials. The aim of this study was to prepare and characterize encapsulated n-dodecane, a kind of PCM with a phase change temperature at about −10°C, in micro- and nanoscales via an in-situ polymerization method with melamine-formaldehyde resin (MF) as the shell. By analyses with scanning electronic microscopy, Fourier transform infrared spectroscopy and 13C nuclear magnetic resonance, it was found that the obtained capsules containing n-dodecane were on microns or several hundreds of nanometers size with spherical shape and smooth surface, and the agglomeration of the capsules was mainly dependent on the average diameters which was controlled by the stirring rate during emulsification of n-dodecane, as well as the concentration of the emulsifying agent and the reaction temperature. Thermogravimetric analysis showed that the n-dodecane capsules increased their thermal stability with decreased diameter. The results of differential scanning calorimetry showed that the supercooling degree of n-dodecane in nanocapsules was somewhat higher than that in the microcapsules, and the suppression of supercooling is considered.

Effect of Polyhedral Oligomeric Silsesquioxane and Sorbitol on Properties of Isotactic Polypropylene

Isotactic polypropylene(iPP) was modified by the introduction of polyhedral oligomeric silsesquioxanes(POSS) and 1,3:2,4-bis(3,4-dimethylbenzylidene)sorbitol(DMDBS). Chemical combination of (3-mercapto)-propyl-heptaisobutyl POSS with DMDBS(POSS-DMDBS), and physical mixing of DMDBS with octaisobutyl POSS (iso-POSS/DMDBS) or trisilanolisobutyl POSS(tri-POSS/DMDBS) were applied respectively to modifying iPP, and the effects of POSS and DMDBS on crystallization, rheological and mechanical properties of iPP were systematically investigated. The results indicate that iso-POSS/DMDBS and tri-POSS/DMDBS were more effective than POSS-DMDBS on the improvement of the crystallization behavior of iPP due to the higher crystallization temperature, while the crystallinity of iPP containing POSS-DMDBS was enhanced, approximately approached to that of iPP containing tri-POSS/DMDBS. The tensile strength of iPP with POSS-DMDBS was significantly increased from 34 MPa to 40 MPa, as high as that of iPP with iso-POSS/DMDBS. The different effects caused by the specific interaction between POSS and DMDBS could possibly be applied in the modification of iPP.

Amphiphilic Copolymers Containing POSS and SBMA with N-Vinylcaprolactam and N-Vinylpyrrolidone for THF Hydrate Inhibition

Icelike gas hydrates deposited in the pipelines under low temperatures and high pressures could remarkably reduce the transport efficiency, and a low dosage of water-soluble polymers could act as kinetic hydrate inhibitors (KHIs) to prevent gas hydrate formation. It was believed that the hydrophobic moiety in the water-soluble polymers played a vital role in enhancing the KHI performance. In this work, amphiphilic copolymers containing hydrophobic polyhedral oligomeric silsesquioxane (POSS) and superhydrophilic sulfobetaine methacrylate (SBMA) as well as N-vinylcaprolactam (VCap) and N-vinylpyrrolidone (VP) were prepared, and an efficient effect of the obtained amphiphilic copolymers on tetrahydrofuran (THF) hydrate inhibition was found. When a certain amount of the amphiphilic copolymers was introduced, the THF hydrate as an analogue of structure II gas hydrates presented a prolonged induction time and gave rise to a looser state rather than a crystalline solid. Analyses of low-field nuclear magnetic resonance and differential scanning calorimetry verified that there were strong interactions between the copolymer and water molecules by incorporation of SBMA units, which could enhance the KHI properties of the prepared amphiphilic copolymers. Additionally, the hydrophobic POSS in the amphiphilic copolymers could possibly modulate the hydrophilic/hydrophobic balance, contributing to the synergistical ability of the copolymers for THF hydrate inhibition. It was suggested that the amphiphilic copolymers containing POSS and zwitterionic units with VCap or VP could have potential for the inhibition and antiaggregation of gas hydrates in the transportation pipelines.