聚合物纖維線徑與順向性對單根聚環氧乙烯奈米纖維之熱傳導率影響

Abstract

高分子聚合物在材料分類中，通常屬於熱的不良導體，但因其本身具備可饒性、不導電、重量輕盈等特性，若能增強其熱傳性能，將會為電子散熱元件增添新的解熱方案。根據文獻指出，藉由調配不同濃度的半結晶高分子聚環氧乙烯(Polyethylene Oxide, PEO)溶液與使用靜電紡絲(Electrospinning)系統製備出PEO奈米纖維薄膜，再將不同濃度的PEO奈米纖維薄膜在常溫下進行熱傳導率量測，發現低濃度的PEO奈米纖維薄膜擁有最高的熱傳導率，原因在於低濃度的PEO奈米纖維薄膜檢測出最高的順向性(Orientation)，間接說明在非結晶區域(Amorphous region)中，PEO奈米纖維排列方向趨於一致，更有效傳遞能量，使得熱傳率與順向性呈現相依關係，但此機制是藉由量測PEO奈米纖維薄膜之熱傳導率，所總結出順向性作為熱傳導率增強的因素，而對於單根PEO奈米纖維是否會因線徑、順向性等因素影響其熱傳導率，目前仍處於未知數，因此本研究將探討線徑和順向性對單根PEO奈米纖維的熱傳導率之關係，藉由靜電紡絲與調配不同濃度的PEO溶液，製備出不同線徑和不同順向性的PEO奈米纖維，後續透過微機電製程，製備懸浮微元件以量測PEO奈米纖維的熱傳導率。從環境溫度對熱傳導率的關係中，發現在常溫300K下，隨著線徑越小，其熱傳導率有所增加；接著探討順向性對熱傳導率之關係，在常溫300K下，隨著順向性增加，其熱傳導率也跟著增加。

In material classification, polymer materials are generally considered thermal insulators. However, due to their inherent properties of flexibility, electrical insulation, and light weight, enhancing their thermal conductivity could provide new solutions for thermal management in electronic cooling components. According to the literature of Lu et.al, polyethylene oxide (PEO) is one kind of semicrystalline polymers. PEO nanofiber films were fabricated by preparing PEO solutions with different concentrations of solute and using an electrospinning system. The thermal conductivity of these films was measured at room temperature, revealing that low-concentration PEO nanofiber membranes exhibited the highest thermal conductivity. This is attributed to the highest orientation observed in low-concentration PEO nanofiber membranes, which indirectly suggests that in the amorphous region, the alignment of PEO nanofibers becomes more uniform, enabling more efficient energy transfer. This indicates a correlation between thermal conductivity and orientation. However, this mechanism was deduced from measurements of the thermal conductivity of PEO nanofiber membranes, leaving the effects of factors such as fiber diameter and orientation on the thermal conductivity of individual PEO nanofibers unknown. Therefore, this study aims to explore the relationship between fiber diameter, orientation, and the thermal conductivity of single PEO nanofibers. By using electrospinning and preparing PEO solutions with varying concentrations of solute, PEO nanofibers with different diameters and orientations were fabricated. Subsequently, their thermal conductivity was measured using suspended microdevices fabricated via MEMS technology. Finally, The relationship between ambient temperature and thermal conductivity revealed that at room temperature (300 K), smaller fiber diameters corresponded to higher thermal conductivity, showing an inverse trend. Additionally, the relationship between orientation and thermal conductivity showed a positive correlation, with thermal conductivity increasing alongside improved orientation at 300 K.