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A series of alkyl sulphobetaine Gemini surfactants Cn‐GSBS (n = 8, 10, 12, 14, 16) was synthesized, using aliphatic amine, cyanuric chloride, ethylenediamine, N,N′‐dimethyl‐1,3‐propyldiamine and sodium 2‐chloroethane sulfonate as main raw materials. The chemical structures were confirmed by FT‐IR, 1H NMR and elemental analysis. The Krafft points differ markedly with different carbon chain length, for C8‐GSBS, C10‐GSBS and C12‐GSBS are considered to be below 0 °C and C14‐GSBS, C16‐GSBS are higher than 0 °C but lower than room temperature. Surface‐active properties were studied by surface tension and electrical conductivity. Critical micelle concentrations were much lower than dodecyl sulphobetaine (BS‐12) and decreased with increasing length of the carbon chain from 8 to 16, and can reach a minimum as low as 5 × 10−5 mol L−1 for C16‐GSBS. Effects of carbon chain length and concentration of Cn‐GSBS on crude oil emulsion stability were also investigated and discussed.

Basalt fiber-reinforced polymer (BFRP) bars have been increasingly applied to offshore structures, which are subjected to seawater corrosion and wet-dry cycles during their service time. This study evaluated the alkali-salt resistance performance of BFRP bars with different resin matrix types under wet-dry cycles. The tensile and shear strength of BFRP bars were tested. As a comparison, experiments of BFRP bars under continuous immersion were also conducted. The mechanisms of the two different conditions were analyzed by scanning electron microscopy (SEM). A relationship was established between the degradations under continuous immersion and wet-dry cycling. The results demonstrated that the alkali-salt resistance of vinyl resin matrix BFRP bars was superior to that of epoxy resin matrix BFRP bars under wet-dry cycles. Furthermore, according to the data obtained under continuous immersion, a time shift factor for predicting the durability of BFRP bars under wet-dry cycles was proposed.

A series of bi‐component nonylphenol alkyl sulphonate surfactants with different alkyl chains (C12/n‐NPAS, n = 8, 10, 14, 16) were synthesized through sulphonation‐alkylation‐neutralization, using a mixture of linear alpha olefins as raw materials. The chemical structures were characterized by FTIR and ESI‐MS. The purity values measured by the two‐phase titration method were all higher than 0.96 g/g (96 wt%). The effects of the raw materials composition on salinity tolerance, adsorption, and emulsification properties were also investigated. There is marked adsorption amount variation for bi‐component surfactants with a strong difference of carbon number of alkyl groups. The salinity tolerance of C12/n‐NPAS is about 40 g · L−1 of NaCl, and 0.65 g · L−1 of CaCl2. Compared with petroleum sulphonates (14 g · L−1 of NaCl, 0.08 g · L−1 of CaCl2) and LAS (22 g · L−1 of NaCl, 0.37 g · L−1 of CaCl2), NPAS surfactants show a low adsorption, excellent salinity tolerance, and emulsion stability.