Transformation of polyethylene into a vitrimer by nitroxide radical coupling of a bis-dioxaborolane†,Polymer Chemistry

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Transformation of polyethylene into a vitrimer by nitroxide radical coupling of a bis-dioxaborolane†
Polymer Chemistry ( IF 4.1 ) Pub Date : 2019-04-04 00:00:00 , DOI: 10.1039/c9py00253g
Florent Caffy _{1,

2,

3,

4,

5} , Renaud Nicolaÿ _{1,

2,

3,

4,

5}

Affiliation

Vitrimers are a new class of polymeric materials that combine the re-processability of thermoplastics with the superior chemical and thermo-mechanical properties of thermosets. Transformation of existing thermoplastics, especially commodity plastics, into vitrimers during their processing is an exciting challenge that could greatly facilitate the industrial development of these materials. In this study, we combined nitroxide chemistry, for radical grafting, and boronic ester metathesis, as an associative exchange reaction, to prepare PE vitrimers via a single-step reactive extrusion of commercial HDPE. After studying the grafting efficiency of a model nitroxide carrying a dioxaborolane moiety, a bis-dioxaborolane bearing two nitroxide functions was used to synthesize vitrimers. The functionalization degree and its impact on the degree of crystallinity of vitrimers were quantified. The flow properties, thermal stability and thermo-mechanical properties of the resulting vitrimers were also studied. We found that associative exchange reactions allow full stress relaxation and provide processability to the vitrimers up to approximately 200 °C. Above this temperature, the thermolabile alkoxyamine bonds within the cross-links irreversibly dissociate, resulting in a material with a zero-shear viscosity comparable to that of the starting HDPE. The recyclability of these vitrimers was successfully exemplified with successive cycles of processing and mechanical testing, while their creep resistance at 80 °C was compared to that of their HDPE precursor.

中文翻译：

通过双二氧杂硼环烷的氮氧化物自由基偶联将聚乙烯转化为发质剂†

搪瓷是一类新型的聚合材料，将热塑性塑料的可再加工性与热固性塑料的优异化学和热机械性能结合在一起。现有的热塑性塑料，特别是商品塑料，在加工过程中转变为微粉聚合物是一个令人振奋的挑战，可以极大地促进这些材料的工业发展。在这项研究中，我们结合了用于自由基接枝的氮氧化物化学和硼酸酯易位，作为缔合交换反应，通过商业HDPE的一步反应挤出。在研究了带有二氧杂硼烷部分的一氧化氮模型的接枝效率后，使用具有两个氮氧官能团的双-二氧杂硼烷合成了三聚体。定量功能化程度及其对微晶聚合物结晶度的影响。还研究了所得微粉的流动性能，热稳定性和热机械性能。我们发现，缔合交换反应可完全缓解应力，并为微晶纤维素提供可加工性，温度最高可达约200°C。高于该温度，交联内的不耐热烷氧基胺键不可逆地解离，从而产生零剪切粘度与起始HDPE相当的材料。

更新日期：2019-04-04

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