Samyn Pieter, Rastogi Vibhore K
Chair of Bio-Based Materials Engineering, University of Freiburg, Werthmannstrasse 6, D-95070 Freiburg, Germany.
SIRRIS-Department Circular Economy and Renewable Materials, Wetenschapspark 3, B-3590 Diepenbeek, Belgium.
Nanomaterials (Basel). 2022 Dec 6;12(23):4329. doi: 10.3390/nano12234329.
The emulsification of biowaxes in an aqueous environment is important to broaden their application range and make them suitable for incorporation in water-based systems. The study here presented proposes a method for emulsification of carnauba wax by an in-situ imidization reaction of ammonolysed styrene (maleic anhydride), resulting in the encapsulation of the wax into stabilized organic nanoparticles. A parameter study is presented on the influences of wax concentrations (30 to 80 wt.-%) and variation in reaction conditions (degree of imidization) on the stability and morphology of the nanoparticles. Similar studies are done for encapsulation and emulsification of paraffin wax as a reference material. An analytical analysis with Raman spectroscopy and infrared spectroscopy indicated different reactivity of the waxes towards encapsulation, with the bio-based carnauba wax showing better compatibility with the formation of imidized styrene (maleic anhydride) nanoparticles. The latter can be ascribed to the higher functionality of the carnauba wax inducing more interactions with the organic nanoparticle phase compared to paraffin wax. In parallel, the thermal and mechanical stability of nanoparticles with encapsulated carnauba wax is higher than paraffin wax, as studied by differential scanning calorimetry, thermogravimetric analysis and dynamic mechanical analysis. In conclusion, a stable aqueous emulsion with a maximum of 70 wt.-% encapsulated carnauba wax was obtained, being distributed as a droplet phase in 200 nm organic nanoparticles.
在水性环境中对生物蜡进行乳化，对于拓宽其应用范围并使其适合纳入水基体系而言至关重要。本文所呈现的研究提出了一种通过氨解苯乙烯（马来酸酐）的原位酰亚胺化反应来乳化巴西棕榈蜡的方法，从而将蜡包裹在稳定的有机纳米颗粒中。针对蜡浓度（30至80重量%）以及反应条件变化（酰亚胺化程度）对纳米颗粒稳定性和形态的影响进行了参数研究。作为参考材料，对石蜡的包裹和乳化也进行了类似研究。利用拉曼光谱和红外光谱进行的分析表明，这些蜡在包裹方面具有不同的反应活性，生物基巴西棕榈蜡与酰亚胺化苯乙烯（马来酸酐）纳米颗粒的形成表现出更好的相容性。这可以归因于巴西棕榈蜡具有更高的官能度，相较于石蜡，它能与有机纳米颗粒相产生更多相互作用。同时，通过差示扫描量热法、热重分析和动态力学分析研究发现，包裹有巴西棕榈蜡的纳米颗粒的热稳定性和机械稳定性高于石蜡。总之，获得了一种稳定的水乳液，其中包裹的巴西棕榈蜡含量最高可达70重量%，以液滴相分布在200纳米的有机纳米颗粒中。
