The volatilization of polycarbosilanes is important to the processing and performance of polymer infiltration and pyrolysis‐based ceramic matrix composites. Low molecular weight (MW) polycarbosilane is often present in preceramic polymers and enhances viscosity for the purpose of composite infiltration. Due to the volatility of low MW chains, a model was developed to semi‐empirically determine the MW distribution and then predict the mass yield and evolution of the MW distribution as a function of temperature and time for StarPCS^™ SMP‐10. The enthalpy of vaporization, the temperature dependence of the enthalpy of vaporization, the temperature dependence of the normal boiling point and a representation of the molecular weight distribution were fit using a series of thermogravimetric measurements, involving isothermal holds on a particular batch of SMP‐10. Once calibrated for SMP‐10 in this fashion, the molecular weight distribution of different batches of SMP‐10 could be fit using a thermogravimetric measurement involving a reduced temperature‐time series. The model was then predictive of mass loss over time for temperatures below the onset of curing (>90°C). Understanding this volatilization enables improved SiC yield, reduced processing time and minimizing void/bubble formation.

中文翻译：

---

用于陶瓷基复合材料的聚碳硅烷的低温演变和产率的工艺模型

聚碳硅烷的挥发对于聚合物渗透和热解陶瓷基复合材料的加工和性能至关重要。低分子量（MW）的聚碳硅烷通常存在于陶瓷前聚合物中，并出于复合渗透的目的而提高了粘度。由于低分子量链的波动性，开发了一个模型以半经验方法确定分子量分布，然后预测StarPCS ^™的质量产率和分子量分布随温度和时间的变化SMP-10。汽化焓，汽化焓的温度依赖性，正沸点的温度依赖性以及分子量分布的表示均通过一系列热重测量进行拟合，其中包括对特定批次的SMP-10进行等温保持。一旦以此方式对SMP-10进行了校准，就可以使用涉及减少温度时间序列的热重测量来拟合不同批次SMP-10的分子量分布。然后，该模型可预测低于固化开始温度（> 90°C）随时间的质量损失。了解这种挥发可以提高SiC的产量，减少处理时间并最大程度地减少空隙/气泡的形成。