Belkhiri Achraf, Virgilio Nick, Nassiet Valérie, Welemane Hélène, Chabert France, De Almeida Olivier
Laboratoire Génie de Production (LGP), Institut National Polytechnique de Toulouse (INP)-Ecole Nationale d'Ingénieurs de Tarbes (ENIT), Université de Toulouse, 65000 Tarbes, France.
Institut Clément Ader (ICA), Université de Toulouse, CNRS UMR 5312, IMT Mines Albi, UPS, INSA, ISAE-SUPAERO, Campus Jarlard, 81013 Albi, France.
Polymers (Basel). 2022 Sep 3;14(17):3663. doi: 10.3390/polym14173663.
Reactive thermoplastics matrices offer ease of processing using well-known molding techniques (such as Resin Transfer Molding) due to their initially low viscosity. For Polyamide 6 (PA6)/glass composites, the hydroxyl groups on the glass surface slow down the anionic ring-opening polymerization (AROP) reaction, and can ultimately inhibit it. This work aims to thoroughly control the hydroxyl groups and the surface chemistry of glass particulates to facilitate in situ AROP-an aspect that has been barely explored until now. A model system composed of a PA6 matrix synthesized by AROP is reinforced with calcinated and silanized glass microparticles. We systematically quantify, by TGA and FTIR, the complete particle surface modification sequence, from the dehydration, dehydroxylation and rehydroxylation processes, to the silanization step. Finally, the impact of the particle surface chemistry on the polymerization and crystallization of the PA6/glass composites was quantified by DSC. The results confirm that a careful balance is required between the dehydroxylation process, the simultaneous rehydroxylation and silane grafting, and the residual hydroxyl groups, in order to maintain fast polymerization and crystallization kinetics and to prevent reaction inhibition. Specifically, a hydroxyl concentration above 0.2 mmol OH·g leads to a slowdown of the PA6 polymerization reaction. This reaction can be completely inhibited when the hydroxyl concentration reaches 0.77 mmol OH·g as in the case of fully rehydroxylated particles or pristine raw particles. Furthermore, both the rehydroxylation and silanization processes can be realized simultaneously without any negative impact on the polymerization. This can be achieved with a silanization time of 2 h under the treatment conditions of the study. In this case, the silane agent gradually replaces the regenerated hydroxyls. This work provides a roadmap for the preparation of reinforced reactive thermoplastic materials.
反应性热塑性基体因其初始低粘度，使用众所周知的成型技术（如树脂传递模塑）易于加工。对于聚酰胺6（PA6）/玻璃复合材料，玻璃表面的羟基会减缓阴离子开环聚合（AROP）反应，并最终抑制该反应。这项工作旨在全面控制玻璃颗粒的羟基和表面化学性质，以促进原位AROP——这是一个迄今为止几乎未被探索的方面。由通过AROP合成的PA6基体组成的模型体系用煅烧和硅烷化的玻璃微粒增强。我们通过热重分析（TGA）和傅里叶变换红外光谱（FTIR）系统地量化了从脱水、脱羟基和再羟基化过程到硅烷化步骤的完整颗粒表面改性序列。最后，通过差示扫描量热法（DSC）量化了颗粒表面化学性质对PA6/玻璃复合材料聚合和结晶的影响。结果证实，为了保持快速的聚合和结晶动力学并防止反应抑制，在脱羟基过程、同时进行的再羟基化和硅烷接枝以及残余羟基之间需要仔细平衡。具体而言，羟基浓度高于0.2 mmol OH·g会导致PA6聚合反应减缓。当羟基浓度达到0.77 mmol OH·g时，如完全再羟基化颗粒或原始原料颗粒的情况，该反应会被完全抑制。此外，再羟基化和硅烷化过程可以同时实现，而不会对聚合产生任何负面影响。在本研究的处理条件下，硅烷化时间为2 h即可实现。在这种情况下，硅烷试剂逐渐取代再生的羟基。这项工作为增强反应性热塑性材料的制备提供了路线图。
