Optimized silyl ester diblock methacrylic copolymers: A new class of binders for chemically active antifouling coatings

This work focuses on the assessment of the erosion properties and antifouling (AF) performance of silyl ester copolymer-based coatings through laboratory and field tests. Silyl ester diblock copolymers were synthesized via the reversible addition-fragmentation chain transfer polymerization and were selected as binders for developing copper-free chemically active coatings. AF coatings were subsequently prepared using biocides (Sea-Nine™ 211, Preventol^® A4S, and zinc pyrithione). Laboratory-based bioassays, targeting the growth of selected microorganisms (bacteria and microalgae) and barnacle settlement, highlighted that the silyl ester methacrylic-based binders did not inhibit the growth of microorganisms, are essentially non-toxic to nauplii and reduced the settlement of Amphibalanus amphitrite cyprids. The corresponding biocidal coatings are potent toward bacteria and diatoms but were demonstrated to be toxic against the barnacle larvae. Field test results showed variations with geographical locations: in sub-tropical area, the silyl ester methacrylic-based coatings failed to inhibit the settlement of barnacles; however, field tests performed in Mediterranean Sea for 18 months demonstrated that biocidal silyl ester methacrylic-based coatings were promising candidates.     

Synthesis and characterization of coumarin thiazole derivative 2-(2-amino-1,3-thiazol-4-yl)-3H-benzo[f]chromen-3-one with anti-microbial activity and its potential application in antimicrobial polyurethane coating

Coumarin, thiazole and their respective derivative products are some of the oldest and most commonly known class of nitrogen and sulphur containing compounds. In recent years there has been considerable interest in this coumarin–thiazole derivatives, which have been reported to exhibit significant biological activity and are widely used as pharmaceuticals. They are capable of imparting anti-microbial activity properties when incorporated into polymers and polymer composites. In this research, coumarin–thiazole derivative 2-(2-amino-1,3-thiazol-4-yl)-3H benzo[f]chromen-3-one (compound III), was prepared and its structure was confirmed by means of its spectra data. It was also screened for its anti-microbial activity against eight different micro-organisms when physically incorporated into a polyurethane varnish formula. Experimental coatings were manufactured on a laboratory scale and applied by means of a brush on both glass and steel panels. The results of the biological activity indicated that the polyurethane varnishes containing the 2-(2-amino-1,3-thiazol-4-yl)-3H-benzo[f]chromen-3-one (compound III) derivative, exhibit a very good antimicrobial effect. The molecular modeling study revealed that it is biologically safe, it is active and it fulfills Lipinski's rule of five. The physical and mechanical resistances of the polyurethane varnish formulations were also studied to evaluate any drawbacks associated with the addition of the derivative. The studies indicate that the physical incorporation of compound III actually enhances slightly both the physical and mechanical properties.     

Expression of the transportation of corrosive media into epoxy coating using nano-indentation

Nano-hardness (H_nano) and nano-elastic modulus (E_nano) of corroded coating surface layer were investigated using nano-indentation after epoxy coated specimens were immersed in 5% NaCl solution. The penetration depths (d) of corrosive media into epoxy coating were calculated fitting the curves of (H/E)_nano vs. indentation depth (h). EIS spectra of epoxy coated specimens immersed in 5% NaCl solution for different time were measured. Finally the relationship of capacitance (C_f,T) of corroded epoxy coating with the penetration depth of corrosive media was studied. The experimental results showed that the transportation process of corrosive media into epoxy coating was studied through the profiles of (H/E)_nano with indentation depth. The penetration depth of corrosive media into the epoxy coating increases rapidly with immersed time firstly, and then increases slowly. The capacitance of corroded epoxy coating has a linear function relationship with the penetration depth of corrosive media into epoxy coating. Nano-indentation can be used to study the transportation process of corrosive media into organic coating.     

Biodegradable and thermostable synthetic hyperbranched poly(urethane-urea)s as advanced surface coating materials

Aliphatic hyperbranched poly(urethane-urea)s with different weight percentages of branch generating moiety were synthesized by a one pot A₂ + BC₂ approach. Isophorone diisocyanate was used as the A₂ type monomer, while a tri-functional dihydroxyamine compound synthesized from ?-caprolactam and diethanol amine acted as the BC₂ monomer. Evidence supporting the hyperbranched structure of the synthesized poly(urethane-urea) was obtained from ¹H NMR spectra. FTIR study confirmed the nature and extent of hydrogen bonding present in this novel macromolecule. A Gaussian band fitting procedure of the IR band at amide-I region showed that the extent of hydrogen bonding increases with the increase of weight percentage of the tri-functional compound. The tensile strength, elongation at break, impact resistance, scratch hardness and gloss followed an increasing trend with the same. The thermal degradation of the hyperbranched poly(urethane-urea) was found to be dependent on the weight percentage of the BC₂ type moiety. The kinetics of thermal degradation studied by the Ozawa method showed that the activation energy required for thermal degradation of hyperbranched polymer is higher than its linear polyurethane analog. The synthesized polymer was found to be biodegradable by Pseudomonas aeruginosa bacteria. The study showed superiority of the hyperbranched structure over the linear one. Thus the results indicated the potential usage of the studied hyperbranched poly(urethane-urea) as an advanced surface coating material.     

镀镍层的汗渍腐蚀及防护

镀镍层对手汗渍非常敏感,容易形成汗渍性指纹腐蚀。经过试验研制了镀镍层专用的水性LP-1068C和溶剂型SP-2068C防汗渍性指纹的电接触润滑保护剂。其作用是防止钢铁和铝基体腐蚀,保护镀层不失光泽,并能充当镀镍后脱水材料,同时保持和保护镀镍层固有的电气性能。试验表明:只有使用具有协同效应的保护材料,才能起到防汗渍性指纹的保护作用。     

Asymmetric supported dense lanthanum tungstate membranes

In this work, a colloidal processing route for dense asymmetric La_28−xW_4+xO_54+3x/2 membranes for hydrogen gas separation applications was established. Dip coating process conditions were optimized to obtain ≈20 μm thick dense layer supported on a porous substrate of the same composition. Surfactants based on electrosteric stabilization were evaluated to obtain stable suspensions in ethanol. The effect of the quantity and type (rice starch and carbon black) of sacrificial pore formers was evaluated for the porous substrates. Based on our results, samples made with 35–45 vol.% carbon black are the best choice to obtain highly porous supports with the optimum characteristics for the fabrication of asymmetric membranes.     

分子质量调节剂对丙烯酸酯乳液压敏胶性能的影响

采用预乳化半连续聚合法,合成了丙烯酸酯乳液压敏胶。探讨了叔十二烷基硫醇、2,4-二苯基-4-甲基-1-戊烯、乙二醇以及异丙醇等分子质量调节剂对压敏胶聚合稳定性、黏度、初粘性、持粘性和180o剥离强度的影响。结果表明,叔十二烷基硫醇和异丙醇对压敏胶的性能影响较大,2,4-二苯基-4-甲基-1-戊烯和乙二醇的影响较小;随分子质量调节剂用量增大,压敏胶的初粘性增大,持粘性和180o剥离强度先增大后降低,黏度先降低后又增大;加入2,4-二苯基-4-甲基-1-戊烯和异丙醇的乳液压敏胶聚合稳定性随分子质量调节剂用量增大而变差,加入叔十二硫醇的乳液压敏胶的聚合稳定性则随用量增大先变差后又增强,而乙二醇则与之相反。     

一种钼酸盐钝化液配制与其对镀锌钢材钝化效果的初步探索

通过对钼酸盐钝化实验的研究,了解了钼酸盐对镀锌层进行钝化的工艺,探讨了钝化液组成及工艺条件对钝化成膜及膜层耐蚀性的影响。用醋酸铅溶液对钝化膜进行点滴试验,并对其结果进行了分析,得出了一些有参考价值的结论。     

汽车发动机缸盖表面高锰酸盐转化膜工艺

汽车发动机缸盖为铝合金材质,为减少腐蚀并延长使用寿命,在实际生产过程中往往需要进行表面处理,进一步满足相应的环境安全性和适应性的要求。采用能耗少,操作简单的无铬化学氧化方法,利用电化学极化曲线、E-T曲线以及交流阻抗谱测试评估铝合金高锰酸盐化学转化膜在3.5%的NaCl水溶液中的耐蚀性能。实验结果表明,高锰酸盐转化膜在KMnO4 8 g/L,NaF 1 g/L,Na2ZrF6 0.06g/L,活性剂适量,pH值为2,处理温度为室温,浸泡时间为10 min得到了较好的化学转化膜。