Sub-micrometer polyamide droplets dispersed in polyethylene: Dimensional stability above the melting point of polyethylene
Sub-micrometer polyamide droplets dispersed in polyethylene: Dimensional stability above the melting point of polyethylene
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DOI：
10.1016/j.polymer.2006.05.016
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发表时间：
2006-07
期刊：
影响因子：
4.6
通讯作者：
M. Sanchez;V. Mathot;G. Groeninckx;Willie Bruls
中科院分区：
文献类型：
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作者：
M. Sanchez;V. Mathot;G. Groeninckx;Willie Bruls
通过MA接枝聚乙烯作为增容剂将聚酰胺6（PA 6）精细分散于其中的茂金属催化剂聚合的乙烯-1-辛烯共聚物在高温下显示出非常规的机械行为。一旦乙烯-1-辛烯共聚物熔融，该体系仍显示出良好的机械性能和尺寸稳定性。此外，由于该体系的分散相形态，会发生所谓的分级/均匀结晶（与本体PA 6结晶温度相比，额外过冷约50°C），并且该材料可以在相同的温度范围内加工，随后将显示出良好的机械响应。这种有趣的机械行为的解释是寻求在系统的分子结构，原来是与较慢的流动动力学的矩阵链的情况下，足够高的摩尔质量。较慢的动力学是由缠结密度的增加引起的，缠结密度的增加是由于基质链和化学连接到液滴的增容剂链之间的混合/相互作用。液滴由此起到物理交联的作用。
Metallocene-catalyst polymerized ethylene-1-octene copolymers in which a polyamide 6 (PA6) is finely dispersed by means of a MA-grafted-polyethylene as compatibilizer show a non-conventional mechanical behavior at high temperatures. Once the ethylene-1-octene copolymer is melted the system still shows good mechanical properties and dimensional stability. Besides, due to the dispersed phase morphology of the system, so-called fractionated/homogeneous crystallization takes place (extra supercooling of around 50°C compared to the bulk PA6 crystallization temperature) and the material can be processed in the same temperature range in which it later on will show good mechanical response. The explanation of this intriguing mechanical behavior is sought in the molecular architecture of the system and turns out to be related to the slower flow dynamics of the matrix chains in case of high enough molar mass. The slower dynamics is caused by an increase in entanglement density due to mixing/interactions between matrix chains and compatibilizer chains chemically attached to the droplets. The droplets thereby function as physical crosslinks.