聚醚酮酮(PEKK)具有Ⅰ、Ⅱ两种晶型结构,其中晶型Ⅰ为稳态晶体,晶胞尺寸大,而晶型Ⅱ尺寸较小,热稳定性较差,对力学的贡献有限。因此,需要调控热压成型工艺促进晶型Ⅰ的生成,并抑制晶型Ⅱ。通过模压成型法研究预热及退火处理对诱导Ⅰ型结晶的影响,结果表明,在熔融温度下充分预热处理后再压制成型,分子链有较高的运动能力,满足晶型Ⅰ生长的慢成核条件,从而充分诱导Ⅰ型结晶,并抑制Ⅱ型结晶。380℃预热处理后,PEKK板材的力学性能得到显著提升,拉伸强度和杨氏模量分别达到104MPa和2.61GPa。此外,还发现在中高温区域进行退火处理也会促进晶型Ⅱ的生长,导致材料的力学性能下降;而增加降温速率,则会提高材料的刚性,初始模量提升至2.80GPa。
Polyetherketoneketone (PEKK) has two crystalline forms.The form Ⅰ is a stable crystalline with a large cell size,while the form Ⅱ is small in cell size and has poor thermal stability,leading to limited contribution to the mechanical properties.Therefore,it is necessary to promote the formation of the form Ⅰ and inhibit that of the form Ⅱ by controlling the thermal treatments.The effect of preheating and annealing treatments was studied to imporve the formation process of the form Ⅰ.The PEKK molecular chains had high movability after the preheating treatment above the melting temperatures,and thus can meet the slow nucleation condition for the enhanced growth of the form Ⅰ and inhibited the form Ⅱ crystallization.The preheating at 380℃ can improve the tensile strength and Young's modulus of the naturally cooled PEKK film up to 104MPa and 2.61GPa,respectively.On the other hand,the annealing at the medium high temperatures induced certain form Ⅱ growth,leading to softening phenomenon.When the cooling rate was very fast,although the form Ⅱ was not activated,the film's stiffness was improved,as reflected by the increased modulus up to 2.80GPa.
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基金资助
中央高校基本科研业务费专项资金(2232021G-01)
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