共查询到17条相似文献,搜索用时 93 毫秒
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悬浮-乳液耦合聚合制备大粒径核-壳结构PS/PMMA复合粒子 总被引:2,自引:1,他引:1
采用在苯乙烯(St)悬浮聚合不同时期滴加甲基丙烯酸甲酯(MMA)乳液聚合组分的悬浮-乳液耦合聚合方法,制备大粒径核-壳结构复合粒子。研究发现:在St悬浮聚合初期和宏观成粒基本完成的聚合后期滴加MMA乳液聚合组分,分别得到由初级粒子凝并的非核-壳结构粒子和核-壳结构不完整的复合粒子,粒径分布较宽;在St悬浮聚合中期滴加MMA乳液聚合组分,MMA和PMMA乳胶粒子易于向PS粒子扩散或粘并,制备得到平均粒径大于100gm、粒径分布窄和核-壳结构良好的PS/PMMA复合粒子。 相似文献
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对核壳结构聚合物乳液乳胶粒的粒径及其分布进行了测试,并与同一聚合物体系的其它乳液加以比较、分析,得出其粒径最小、分布最均匀的重要结论. 相似文献
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In this article, we use the technique of multistage emulsion polymerization to synthesize the LIPN PBA/PS/PMMA and use the gravimetric analysis method to study the apparent kinetics of the reaction process and to investigate the influence of the concentration of the initially emulsifying agent, the initiator, and the extent of the crosslinking on the distribution of the particle diameter and the dynamic mechanical properties of the products. 相似文献
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Ashwini Sood 《应用聚合物科学杂志》2004,92(5):2884-2902
Effects of the operating policies—the initial initiator amount; the initial emulsifier amount; the monomer addition mode: batch or semibatch; and the monomer addition rate under “monomer‐starved conditions” for the control of particle size distribution (PSD)—were studied through a model that simulates batch and semibatch reactor operations in conventional emulsion polymerization. The population balance model incorporates both the nucleation stage and the growth stage. The full PSDs were reported, which have normally been omitted in earlier studies. It was shown through simulations that the broadness of the distributions, both initial (obtained after the end of nucleation) and final (after complete conversion of monomer), can be controlled by the initial initiator amount and the emulsifier amount. The higher initiator amounts and the lower emulsifier amounts favor narrower initial and final distributions. The shape of the initial PSDs and the trends in the average size and range were preserved with subsequent addition of monomer in the batch or in the semibatch mode, although the final PSD was always considerably narrower than that of the initial PSD. The addition of monomer in the semibatch mode gave narrower distribution compared to that of the batch mode, and also, lower monomer addition rates gave narrower distributions (larger average sizes), which was a new result. It was further shown through simulations that, under monomer‐starved conditions, the reaction rate closely matched the monomer feed rate. These conclusions are explained (1) qualitatively—the shorter the length of the nucleation stage and the larger the length of the growth stage (provided the number of particles remains the same), the narrower is the distribution; and (2) mathematically—in terms of the “self‐sharpening” effect. Experimental evidence in favor of the self‐sharpening effect was given by analyzing the experimental particle size distributions in detail. The practical significance of this work was proposed. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 2884–2902, 2004 相似文献
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Polystrene (PS) particles, generated from soap-free emulsion polymerization of styrene monomer, water, and potassium persulfate, were investigated by photon correlation spectroscopy (PCS) and TEM. The particle size distribution (PSD) was quite uniform. From the data of PCS, it could be said that lots of particles flocculated in the final stage of reaction. It was also deduced from the molecular weight distribution (MWD), measured by GPC, that, during the early stage of reaction, molecules with low molecular weight (<4000) might exist and the particles were perhaps formed through micellar-type nucleation mechanism. When initiator concentration increased, reaction rate increased but weight average molecular weight, tensile modulus, and elongation decreased. The number density of particles was found to be proportional to 0.49 power of initiator concentration. However, monomer concentration did not seem to have any great effect on all of them above. 相似文献
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利用γ 甲基丙烯酰氧丙基三甲氧基硅烷(KH-570)对纳米二氧化硅和纳米碳酸钙有机化处理,红外光谱(FTIR)测试表明,纳米二氧化硅通过有机化处理可以在表面接枝上有机基团,表现在表面处理后波数在2955,2860和1460cm-1有甲基的吸收峰,而纳米碳酸钙由于表面上已有有机基团,表面上没有接枝上新的有机基团。然后利用乳液聚合的方法制备了以表面处理过的纳米二氧化硅或纳米碳酸钙为核,丙烯酸丁酯和甲基丙烯酸甲酯为壳的有机-无机杂化材料。用凝胶渗透色谱(GPC)测定了其各种相对分子质量及其相对分子质量分布后发现,加入纳米碳酸钙后其相对分子质量有所降低,相对分子质量分布变宽;加入纳米二氧化硅后其相对分子质量有所增大,相对分子质量分布变窄。透射电镜(TEM)和粒度分布仪测试表明,乳液聚合前粒子大部分以团聚体的形式存在,粒径在1~2μm左右;乳液聚合后粒子大部分以纳米尺寸存在,粒径10~200nm。实验证明,乳液聚合是制备有机-无机纳米杂化材料非常有效的方法。 相似文献
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Jae Youn Kim W. Curt Conner Robert L. Laurence 《Korean Journal of Chemical Engineering》1998,15(3):262-272
The control of polymer particle size and PSD is of industrial importance. Very fine particles pack poorly, thereby limiting
reactor capacity, and present a dust explosion hazard. In olefin polymerization, a particle size distribution (PSD) in the
polymerization reactor has been derived using population balances. Three reasonable reaction mechanisms for Ziegler-Natta
catalysts, i.e., a simple reaction model, an active site reduction model, and a two sites model, have been used to derive
the average number of active sites. It was observed that the PSD depends not only on residence time, but also on the reaction
mechanism. It was also found that multiple active sites change the PSD slightly. The PSD, however, does not depend on initial
catalyst volume. 相似文献