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首页> 外文会议>International Conference on Blowing Agents and Foaming Processes; 20050510-11; Stuttgart(DE) >NUCLEATION MECHANISMS INVESTIGATED ON POLYSTYRENE/HFC-134A MIXTURES
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NUCLEATION MECHANISMS INVESTIGATED ON POLYSTYRENE/HFC-134A MIXTURES

机译：在聚苯乙烯/ HFC-134A混合物中研究的成核机理

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The conditions prevailing during the nucleation stage for the thermoplastic foam extrusion process in which physical foaming agents (PFA) are involved is one of the key steps in the design and optimization of the process. The conditions that induce the phase separation and the bubble nucleation are obviously linked to the solubility parameters, i.e. temperature and pressure at a given PFA content. It has been reported that nucleating agent can significantly modify these degassing conditions. A characterization method based on ultrasonic sensors has proven to be sensitive to the onset of the phase separation, as well as the kinetics leading to this nucleation stage. This technique has been used successfully off-line on confined samples as well as in-line, i.e. during the foam extrusion process. Ultrasonic properties (ultrasonic velocity and attenuation) and specific volume measurements were thus performed during nucleation and bubble growth of polystyrene/HFC-134a mixtures confined in a static, batch set up. Influence of temperature and pressure, as well the presence of a nucleating agent (talc), on the nucleation kinetics was investigated.
机译：在涉及物理发泡剂（PFA）的热塑性泡沫挤出工艺的成核阶段中，普遍存在的条件是工艺设计和优化中的关键步骤之一。引起相分离和气泡成核的条件显然与溶解度参数有关，即在给定的PFA含量下的温度和压力。据报道成核剂可以显着改变这些脱气条件。事实证明，基于超声波传感器的表征方法对相分离的开始以及导致该成核阶段的动力学很敏感。该技术已成功离线用于密闭样品以及在线，即在泡沫挤出过程中。因此，在静态，分批设置的聚苯乙烯/ HFC-134a混合物的成核和气泡生长过程中，进行了超声波特性（超声波速度和衰减）和比体积的测量。研究了温度和压力以及成核剂（滑石粉）的存在对成核动力学的影响。

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