臺灣博碩士論文加值系統

本研究主要利用分子動力學模擬(Molecular Dynamics simulation)分析探討在高分子加工過程中，當兩流動波前相遇時所產生之縫合線(Weld-Line)介面間，高分子鏈流動排向的行為及相互融合的結果。以分子動力學模擬描述在不同溫度下，縫合線兩邊高分子鏈排列以及相互擴散之排向結果。
本論文首先比照文獻探討hexadecane流體分子(C16H34)於Couette shear flow系統下，壁面性質與剪切率對滑動程度的影響；結果發現當代表壁面與流體交互作用強度的εw增大時，流體與壁面間的滑動現象將會減低，然而壁面粗糙度的增加更能夠有效減少滑動的程度；另外，隨著剪切率增加，滑動的程度則是提昇的。
論文第二部分則是以(C25H52)流體分子進行縫合線的模擬及探討，結果發現溫度低時在波前結合處的z方向(垂直於流動方向)上排向性有集中的情形，造成縫合線的現象，而溫度的提昇可以增加分子鏈相互擴散的深度，並且消弭排向性集中的情形，減低波前結合處縫合線的效應。

In this study, the orientation behavior of polymer chains in weld-line region, which usually occurs in polymer processing when two melt fronts combine together, is simulated by molecular dynamics. Simulation is carried out at different temperature to show polymer chains arrangement and their inter-diffusion in the weld interface.
The first part of this work is to simulate thin films of hexadecane (C16H34) fluid under Couette shear flow. The analysis results about slip boundary phenomena according to different wall properties and shear rates are demonstrated to be in good agreement with references. As the wall roughness or εw increase, the degree of slip will be reduced.On the other hand, larger shear rates cause more slip between fluids and wall. We also show that the fluid velocity profile is not affected by different lattice arrangement.
As to simulation of weld-line, the fluid molecule used is C25H52. Based on the results, the orientation in z-direction, which is perpendiculato the flow direction, is observed to concentrate in the weld-line region formed by two melt fronts. As temperature increases, polymer chains diffuse more into each other, and the z-direction orientation is eliminated.

中文摘要 I
Abstract II
目錄 III
圖目錄 VI
表目錄 X
符號表 XI
第一章、緒論 1
1-1研究目的與動機 1
1-2縫合線與分子鏈結構 3
1-3分子動力學模擬 7
1-3-1分子動力學模擬概論 7
1-3-2分子動力學模擬方法簡介 8
1-3-3 Lennard-Jones Potential 9
1-3-4 NVT系統簡介 10
1-3-5分子動力學與連續力學 13
第二章、文獻回顧 15
2-1簡單分子流動行為 15
2-2高分子鏈結晶排向行為 18
2-3 高分子流動系統 23
第三章、研究方法 28
3-1基本方法分析 28
3-1-1交互作用力形式 28
3-1-2壁面原子與晶格 29
3-1-3邊界條件 30
3-1-4起始條件 31
3-1-5 Orientation factor 32
3-1-6 Thermostat 33
3-2數值方法… 34
3-2-1 Cell link neighbor list 34
3-2-2運動方程式求解 35
3-3模擬流程… 38
3-3-1 Couette shear flow 38
3-3-2縫合線排向 41
第四章、結果與討論 43
4-1 Couette shear flow 43
4-1-1系統初始條件與參數設定 43
4-1-2壁面原子之kw對流速及滑動的影響 43
4-1-3εw對流速及滑動的影響 44
4-1-4剪切率對流速及滑動的影響 44
4-1-5壁面晶格排列對流速及滑動的影響 49
4-2縫合線排向及擴散行為(1) 51
4-2-1系統初始條件 51
4-2-2排向結果 51
4-2-4結果討論(1) 59
4-3縫合線排向及擴散行為(2) 60
4-3-1系統設定 60
4-3-2波前結合 61
4-3-3分子鏈擴散結果 63
4-3-4波前結合處排向性結果 68
4-3-5結果與討論(2) 72
第五章、結論與展望 73
參考文獻 74

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