Minakov A A, Wurm A, Schick C
University of Rostock, Institute of Physics, Universitätsplatz 3, 18051 Rostock, Germany.
Eur Phys J E Soft Matter. 2007 May;23(1):43-53. doi: 10.1140/epje/i2007-10173-8. Epub 2007 May 18.
To study phase transition kinetics on submillisecond time scale a sensitive ultrafast nanocalorimeter was constructed. Controlled ultrafast cooling, as well as heating, up to 10(6) K/s was attained. The method was applied for the measurements of the superheating phenomenon in a set of linear polymers: iPS, PBT, PET, and iPP. A power law relation between the superheating and the heating rate holds in the heating rate range 10(-2) - 10(4) K/s. A limiting superheating of about 10% of the melting temperature was observed at rates above 10(4) - 10(5) K/s. This limit depends on annealing conditions before sample melting. The observed superheating limit, as well as the power law, can be accounted for the internal stresses near the crystalline amorphous interface in semicrystalline polymers induced by heating, which are related to the thermal expansion gradients inherent in a semicrystalline material.
为了研究亚毫秒时间尺度上的相变动力学，构建了一种灵敏的超快纳米量热计。实现了高达10⁶K/s的可控超快冷却以及加热。该方法被用于测量一组线性聚合物（等规聚苯乙烯（iPS）、聚对苯二甲酸丁二醇酯（PBT）、聚对苯二甲酸乙二酯（PET）和等规聚丙烯（iPP））中的过热现象。在10⁻² - 10⁴K/s的加热速率范围内，过热与加热速率之间存在幂律关系。在高于10⁴ - 10⁵K/s的速率下，观察到约为熔点10%的极限过热。该极限取决于样品熔化前的退火条件。观察到的过热极限以及幂律可以用加热引起的半结晶聚合物中晶态 - 非晶态界面附近的内应力来解释，这些内应力与半结晶材料固有的热膨胀梯度有关。
