Delaroa Claire, Fulchiron René, Lintingre Eric, Buniazet Zoé, Cassagnau Philippe
Université Lyon 1, Ingénierie des Matériaux Polymères, CNRS UMR 5223, 15 Boulevard Latarjet, 69622 Villeurbanne CEDEX, France.
Saint-Gobain CREE, Grains et Poudres, 550 Avenue Alphonse Jauffret, BP 20224, 84306 Cavaillon, France.
Polymers (Basel). 2020 Sep 29;12(10):2247. doi: 10.3390/polym12102247.
The impact of polypropylene and high-density polyethylene backbone binders on the structure of organic matrix, feedstock, and ceramic parts is investigated in terms of morphology in this paper. The miscibility of wax with polyethylene and polypropylene is investigated in the molten state via a rheological study, revealing wax full miscibility with high-density polyethylene and restricted miscibility with polypropylene. Mercury porosimetry measurements realized after wax extraction allow the characterization of wax dispersion in both neat organic blends and zirconia filled feedstocks. Miscibility differences in the molten state highly impact wax dispersion in backbone polymers after cooling: wax is preferentially located in polyethylene phase, while it is easily segregated from polypropylene phase, leading to the creation of large cracks during solvent debinding. The use of a polyethylene/polypropylene ratio higher than 70/30 hinders wax segregation and favors its homogeneous dispersion in organic binder. As zirconia is added to organic blends containing polyethylene, polypropylene, and wax, the pore size distribution created by wax extraction is shifted towards smaller pores. Above zirconia percolation at 40 vol%, the pore size distribution becomes sharp attesting of wax homogeneous dispersion. As the PP content in the organic binder decreases from 100% to 0%, the pore size distribution is reduced of 30%, leading to higher densification ability. In order to ensure a maximal densification of the final ceramic, polyethylene/polypropylene ratios with a minimum content of 70% of high-density polyethylene should be employed.
本文从形态学角度研究了聚丙烯和高密度聚乙烯主链粘结剂对有机基体、原料和陶瓷部件结构的影响。通过流变学研究考察了蜡在熔融状态下与聚乙烯和聚丙烯的混溶性，结果表明蜡与高密度聚乙烯完全混溶，与聚丙烯的混溶性有限。蜡萃取后进行的压汞法测量能够表征蜡在纯有机共混物和氧化锆填充原料中的分散情况。熔融状态下的混溶性差异对冷却后蜡在主链聚合物中的分散有很大影响：蜡优先位于聚乙烯相中，而很容易从聚丙烯相中分离出来，导致在溶剂脱脂过程中产生大裂缝。使用高于70/30的聚乙烯/聚丙烯比例可抑制蜡的偏析，并有利于其在有机粘结剂中的均匀分散。当向含有聚乙烯、聚丙烯和蜡的有机共混物中添加氧化锆时，蜡萃取产生的孔径分布向较小的孔径偏移。在氧化锆体积分数达到40%的渗滤阈值以上时，孔径分布变得尖锐，证明蜡已均匀分散。随着有机粘结剂中PP含量从100%降至0%，孔径分布缩小了30%，导致更高的致密化能力。为确保最终陶瓷的最大致密化，应采用高密度聚乙烯含量至少为70%的聚乙烯/聚丙烯比例。
