Simulation of Intercrystalline Molecular Connections in Branched Polyethylene
Independent thesis Advanced level (professional degree), 20 credits / 30 HE creditsStudent thesis
The Nilsson model developed earlier using Monte-Carlo random walkers for simulating the intercrystalline molecular connections for linear polyethylene (PE) was extended to capture the effect of different molecular architectures, especially short chain branching (SCB). Crystal layers with orthorhombic unit cell were built and filled with random walks starting in the amorphous region. The novel knot algorithm was then used to determine the entangled loop density in addition to the tie chain concentration. This provided systems as large as 100 nm in lateral direction of the crystal to be studied on normal PC’s. Molecular architectures were designed so that polymers with constant molecular weight and short chain branching density (SCBD), molecular weight distribution with no branching, and more realistic situation with both molecular weight distribution and molecular weight dependent branching density could be introduced to the model. In addition, a Graphical User Interphase (GUI) was developed for the code. The influence of various parameters including SCBD, molecular weight, crystal thickness, amorphous thickness and temperature was then studied using the model. Although most experiments showed the dominance of entangled loops than tie chains, a more reliable conclusion can be made after resolving density problem observed; possible solutions were suggested for further investigations.
Place, publisher, year, edition, pages
tie chains; trapped entanglements; branched polyethylene; crystal; simulation
Engineering and Technology
IdentifiersURN: urn:nbn:se:kth:diva-150824OAI: oai:DiVA.org:kth-150824DiVA: diva2:745560