Agglomeration in a polypropylene composite
Translated title
Agglomerering i en polypropylenkomposit
Author
Kruse, Patrick
Term
4. semester
Education
Publication year
2020
Submitted on
2020-06-02
Pages
43
Abstract
Grafenoxid fremstillet ved elektrokemisk eksfoliering blev afprøvet som forstærkende fyldstof i polypropylen (PP)-kompositter. I praksis fordelte fyldstoffet sig meget dårligt: partiklerne havde tendens til at klumpe sammen (agglomerere), hvilket begrænser styrkeforøgelsen i plastmatrixen. Dette studie undersøger problemet og forsøger at afhjælpe det med en basekatalyseret funktionalisering (tilsætning af kemiske grupper under basiske betingelser). Vi udviklede også en enkel mikromekanisk model, der kobler fyldstof-fordeling til stivhed (modstand mod deformation). Modellen pegede på, at bedre fordeling hænger sammen med højere stivhed, om end kun i begrænset omfang. I forsøg med PP reducerede funktionaliseringen ikke agglomerationen, men den øgede alligevel kompositternes stivhed med cirka 60%. Til sammenligning fordelte grafenoxid sig godt i polyvinylalkohol (PVA)—formentlig pga. blandingsmetoden og/eller god kemisk affinitet—og disse kompositter var omkring fem gange så stive som ren PVA. Samlet konkluderes, at den dårlige fordeling i PP ikke skyldtes eksfolieringsmetoden, men derimod måden fyldstoffet blev blandet ind i polymeren.
Graphene oxide produced by electrochemical exfoliation was tested as a reinforcing filler in polypropylene (PP) composites. In practice the filler dispersed very poorly: particles tended to clump together (agglomerate), which limits the strengthening effect in the plastic matrix. This study examines that problem and attempts to counter it using a base‑catalysed functionalisation procedure (adding chemical groups under basic conditions). We also developed a simple micromechanical model to relate filler dispersion to stiffness (resistance to deformation). The model indicated that better dispersion coincides with higher stiffness, although the effect was modest. In experiments on PP, the functionalisation did not reduce agglomeration, but it still increased composite stiffness by about 60%. For comparison, graphene oxide in polyvinyl alcohol (PVA) dispersed well—likely due to the mixing method and/or good chemical affinity—and those composites were roughly five times stiffer than neat PVA. Overall, the poor dispersion observed in PP was not caused by the exfoliation method but by how the filler was mixed into the polymer.
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