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为了改善激光惯性约束聚变用厚壁聚合物空心微球球形度和壁厚均匀性,文中在外水相(W2)引入聚丙烯酸(PAA),对比了不同相对分子质量PAA(L-PAA,H-PAA)与传统界面改性剂聚乙烯醇(PVA)对复合乳粒形变的影响及作用机理。结果表明,PVA通过亲疏水基团可有效稳定直径900μm复合乳粒,但大幅度降低了油水界面张力,当乳粒直径增加,油相和内水相Laplace压力降低,变形增加,PVA对直径1900μm复合乳粒稳定性下降;与PVA体系相比,LPAA体系油水界面张力大,但黏度与PVA体系基本相同,导致乳粒形成时维持力大于剥离力,不利于乳粒形成,且LPAA分子链相对较短,空间位阻较小,复合乳粒易融合、合并;H-PAA分子链长,空间位阻较大,不仅对大小直径复合乳粒稳定效果明显,而且其油水界面张力大,有利于乳粒球形化,提高了高球形度PS微球的产率。
In order to improve the sphericity and wall thickness uniformity of thick-walled polymeric hollow microspheres by laser inertial confinement fusion, polyacrylic acid (PAA) was introduced into outer aqueous phase (W2) to compare the effects of different relative molecular mass PAA (L-PAA, PAA) and the traditional interface modifier polyvinyl alcohol (PVA) on the deformation of composite emulsions and its mechanism of action. The results showed that the hydrophilic and hydrophobic groups of PVA could effectively stabilize the diameter of 900μm composite but significantly reduced the interfacial tension of oil and water. When the diameter of the emulsion increased, the Laplace pressure of the oil phase and internal aqueous phase decreased and the deformation increased. Compared with the PVA system, the interfacial tension between oil and water was large, but the viscosity was the same as that of the PVA system. As a result, the retention of the latex was greater than the peel force, which was unfavorable to the formation of the latex. The LPAA molecular chain was relatively H-PAA molecular chain length, steric hindrance, not only on the stability of large and small diameter composite grain significant effect, and its oil-water interfacial tension is conducive to Spheroidization increases the yield of high sphericity PS microspheres.