Abstract

The authors experimentally studied the behavior of evaporation, convection in the liquid, and temperature of the free surface of a pendant droplet of aqueous solution of PEGDA/Irgacure 2959 before and after the onset of polymerization under UV radiation. Data on the temperature of the free surface of droplet were obtained for a wide range of the initial concentration of the polymer base \(C_{0}\). For \(C_{0}= 35\)% and less, no polymerization area was observed (according to thermal images). The temperature gradients observed over the droplet surface were very low (less than 0.3°C). At \(C_{0}= 65\)% and \(C_{0}= 90\)%, the average temperature \(T_{\rm S}\) on the free surface of droplet changed during polymerization by 2.8C° and 3.7°C, respectively. After polymerization, \(T_{\rm S}\) for the hydrogel became higher than \(T_{\rm S }\) of droplet of pure water. The average velocity of motion of polyamide particles \(U_{C}\) for water was 2.2–2.4 times higher than that for the PEGDA solution with the initial concentration \(C_{0} = 65\)%, which is associated with the higher viscosity of the solution. At the onset of polymerization, the velocity \(U_{C}\)dropped to 0 mm/s in a very short time. With increase in the concentration \(C_{0}\) in the pre-polymer, the time of polymerization reaction start decreased significantly, which shortened the time in which the particles stopped completely. Different limiting factors govern evaporation of a water droplet and a hydrogel droplet. The evaporation rate of droplet of hydrogel decreased with time due to the porous structure of the hydrogel.

中文翻译：

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不同浓度组分的 PEGDA/Irgacure 水溶液液滴中的聚合

摘要

作者通过实验研究了紫外线辐射下聚合开始前后的蒸发行为、液体中的对流行为以及 PEGDA/Irgacure 2959 水溶液悬滴液滴自由表面的温度。在聚合物基\(C_{0}\)初始浓度的较宽范围内获得了液滴自由表面温度的数据 。对于 \(C_{0}= 35\) % 及以下，没有观察到聚合区域（根据热图像）。在液滴表面观察到的温度梯度非常低（小于 0.3°C）。在\(C_{0}= 65\) %和 \(C_{0}= 90\) %时， 聚合过程中液滴自由表面的平均温度\(T_{\rm S}\)变化了2.8C分别为°和3.7°C。聚合后， 水凝胶的\(T_{\rm S}\) 变得高于  纯水滴的\(T_{\rm S}\) 。聚酰胺颗粒在水中的平均运动速度 \(U_{C}\) 比初始浓度 \(C_{0}=65\) %的PEGDA溶液高2.2~2.4倍，这与溶液的粘度越高。聚合开始时，速度 \(U_{C}\)在很短的时间内降至 0 mm/s。随着预聚物中\(C_{0}\)浓度的增加  ，聚合反应开始的时间显着减少，从而缩短了颗粒完全停止的时间。不同的限制因素控制水滴和水凝胶滴的蒸发。由于水凝胶的多孔结构，水凝胶液滴的蒸发速率随着时间的推移而降低。