A master thesis from Aalborg University
Agglomeration in a polypropylene composite
[Agglomerering i en polypropylenkomposit]
Author(s)
Term
4. semester
Education
Publication year
2020
Submitted on
2020-06-02
Pages
43 pages
Abstract
Elektrokemisk exfolieret grafen-oxid har været anvendt som et styrkeøgende additiv i en polypropylenkomposit, men havde en høj grad af agglomerering. Dette reducerer den styrkeøgende effekt, additivet har på polymermatricen, og dette fænomen er undersøgt og forsøgt imødekommet i denne rapport, ved brug af en basekatalyseret funktionaliseringsprocedure. En mikromekanisk model er også udviklet, hvilket viste at bedre dispergering medfører større forøgelser af komposittens stivhed, dog kun i en mindre grad. Den anvendte funktionaliseringsprocedure kunne ikke ændre agglomereringen af additivet, men forøgede komposittens stivhed med omkring 60\%. Kompositter af grafen-oxid i polyvinyl-alkohol testes også, fordi additivet dispergerer godt i en sådan komposit pga. den specifikke blandingsmetode anvendt og/eller de gode interaktionsegenskaber mellem de to. Sammenlignet med ren polyvinyl-alkohol havde kompositten fem gange højere stivhed. Fra de ovennævnte resultater konkluderes det at den dårlige dispergering set i polypropylenkompositterne ikke var et resultat af exfolieringsmetoden, men rettere måden hvorved fyldmaterialet inkorporeres i polymeren.
Electrochemically exfoliated graphene oxide has been used as a strength-enhancing filler in a polypropylene composite, but was found to exhibit abysmal levels of filler dispersion. This is thought to reduce the enhancing effects the filler can impart on the matrix, and this phenomenon is investigated and sought counteracted in this report, using a base-catalysed functionalisation procedure. A micromechanical model is also developed and it showed better dispersion coincided with higher stiffness increase, although only to a minor degree. The employed functionalisation procedure did not influence the agglomeration of the filler, but could increase the stiffness of the composite by around 60\%. Composites of graphene oxide in polyvinyl-alcohol is also tested, as the filler disperses well in such a composite due to the particular method of mixing and/or the good chemical affinity between the two. A five-fold increase in stiffness was observed, compared to specimens of pristine polyvinyl-alcohol. From the aforementioned results it is concluded the poor degree of dispersion observed in polypropylene composites were not a result of the method of exfoliation, but rather the manner in which the filler was mixed with the polymer.
Keywords
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