University Erlangen-Nuremberg, Institute of Particle Technology, Cauerstrasse 4, D-91058 Erlangen, Germany.
J Colloid Interface Sci. 2011 Nov 1;363(1):386-92. doi: 10.1016/j.jcis.2011.07.020. Epub 2011 Jul 22.
The formation of free radicals during wet grinding of alumina in a stirred media mill was studied by using the test radical 2,2-diphenyl-1-picrylhydracyl (DPPH). The kinetics of mechano-chemical radical formation follows a zeroth-order rate law. Particle breakage as well as mechanical activation of the surface of the alumina particles contributes to the radical formation. The rate constants of the radical formation due to mechanical activation of the particle surface k(A) and due to particle breakage k(B) depend on the milling process parameters. The radical formation during wet grinding of alumina was exploited to initiate mechano-chemical polymerization reactions of acrylic acid and acryl amide, respectively. In this way nanoparticles functionalized with polyacrylic acid and polyacryl amide, respectively, are obtained. The influence of the milling process parameters on the kinetics of mechano-chemical radical formation and on the grafted amount of polymer is discussed on the basis of stress energy and number of stress events in the mill. A correlation between the grafted amount of polyacryl amide on the alumina particles and the total radical formation rate was found showing that the concentration of mechano-chemically formed free radicals governs the efficacy of a chemical reaction at activated particle surfaces.
在搅拌式介质磨机中湿磨氧化铝时，通过使用测试自由基 2,2-二苯基-1-苦肼基（DPPH）研究自由基的形成。机械化学自由基形成的动力学遵循零级速率定律。颗粒的破碎以及氧化铝颗粒表面的机械活化有助于自由基的形成。由于颗粒表面的机械活化而导致的自由基形成的速率常数 k(A)和由于颗粒破碎而导致的自由基形成的速率常数 k(B)取决于研磨过程参数。利用氧化铝湿磨过程中形成的自由基分别引发丙烯酸和丙烯酰胺的机械化学聚合反应。以这种方式获得分别用聚丙烯酸和聚丙烯酰胺官能化的纳米颗粒。基于磨机中的应力能和应变速数，讨论了研磨工艺参数对机械化学自由基形成动力学和接枝聚合物量的影响。发现氧化铝颗粒上接枝的聚丙烯酰胺量与总自由基形成速率之间存在相关性，表明机械化学形成的自由基的浓度控制着在活化颗粒表面上化学反应的效率。
