聚醯胺(polyamide, PA)商品名為尼龍(Nylon)，是一種結晶型高分子，由於結晶會嚴重影響高分子在發泡時的黏度和熔體強度，加工窗口非常窄。本研究以不同熔點的聚醯胺與添加劑進行共混以製備低密度之聚醯胺泡珠材料。
本實驗第一部分將不同熔點的聚醯胺依不同比例進行熔融混練。藉由DSC分析結果，將尼龍6(PA 6)與尼龍共聚物(PA 6C)依20:80比例配置之共混物具有雙熔峰結構，且結晶度明顯下降至20%，而雙熔峰溫差(Tm)達15°C。在共混物加入2 phr的苯乙烯-馬來酸酐共聚物(SMA)或1 phr的商用擴鏈劑(Joncryl ADR 4368 C, ADR)會使結晶度約下降到15%。
第二部分以二氧化碳對聚醯胺共混物進行二步法批次發泡，在固定含浸壓力及發泡溫度下，探討含浸溫度對於泡孔型態之影響。隨著含浸溫度上升(80~120°C)，聚醯胺共混物之膨脹倍率可達3.5倍，而加入添加劑會因為黏度上升，抑制泡孔成長。此外在實驗結果觀察到聚醯胺共混物具有bimodal泡孔結構，在80°C下含浸會有泡孔分散不均或未發泡之情形發生，此外加入添加劑會使bimodal泡孔結構更加嚴重。
第三部分以DSC及XRD分析聚醯胺發泡材料，實驗結果發現，發泡材料仍具有雙熔峰結構，而此結構可能之組成為α晶型。

Polyamide (PA), commonly known as Nylon, is a crystalline polymer. Since the crystallization seriously affects the viscosity and the melt strength of polymer during foaming, the foaming process window is very narrow. However, high temperature bead foam is quite rare in the market. In this research, different melting point polyamides was blended with additives to prepare low density polyamide bead foam.
In the first part of the experiment, polyamide with different melting points were prepared and blended in different ratio. The DSC analysis results showed that polyamide 6 (PA 6) and copolyamide (PA 6C) blends with a ratio of 20:80 have a double melting peak structure and the crystallinity is significantly reduced to 20%. The temperature difference of the double melting peak is 15 °C. Adding 2 phr of SMA (Styrene maleic anhydride) or 1 phr of chain extender (Joncryl ADR 4368 C, ADR) in the blends would make the crystallinity further dropped to about 15%.
The second part is a two-step batch foaming of polyamide blends with carbon dioxide. Under a fixed saturation pressure and foaming temperature, the effect of saturation temperature to cell morphology was discussed. When the saturation temperature were increased (80~120 °C), the expansion ratio of polyamide blends reached 3.5 times and the addition of additives would inhibit the cell growth due to the increase of viscosity. In addition, it was observed that the polyamide blend had a bimodal cell structure and the saturation in 80 °C would result in non-uniform or unfoamed cells structure, moreover adding additives can make the bimodal cell structure more severe.
In the third part, the polyamide foamed materials were characterized by DSC and XRD. The experimental results show that the foamed material still indicated a double melting peak structure after foaming, and the composition of this structure is mainly from α crystal form.

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