Publikationsserver der RWTH Aachen University
'Quat-Primer' polymers based on b-PEI and their application in composites
Abstract
dc:descriptionThe thesis is concerned with the synthesis of functionalized polymers prepared by ring opening reaction of various functionalized five-membered cyclic carbonates and epoxides couplers with branched polyethylenimine (b-PEI). Furthermore, depending on the functionality introduced in the polymer, the application of these modified polymers (i) as primers in carbon fibre - epoxy resin composite and (ii) UV curable coatings were also investigated. The primer polymers to be used in carbon fibre epoxy resin composites should serve two functionalities (i) to bind to the surface of carbon fibres via electrostatic forces of interactions or epitaxial adsorption or both and (ii) to supply cyclic carbonate groups that can copolymerize with the amine components of epoxy resins during the curing step. Branched Polyethylenimine has primary, secondary and tertiary amino groups in the molar ratio of 31:39:30 respectively. The primary and secondary amines present in b-PEI can be selectively modified with different couplers. The strategy followed was based on difference in reactivity of secondary amine towards five-membered cyclic carbonate and epoxide ring. Five-membered cyclic carbonate reacts only with primary amine whereas epoxide ring can react with all primary, secondary and tertiary amine. The synthesis of the primer polymers is a two step process. In the first step all the primary amino groups in b-PEI were selectively modified with coupler I or II or both. In the next step the secondary amine in modified b-PEI opens the epoxide ring present in the coupler III to obtain the desired functional polymers. Due to structural similarity of the carbon fibre and graphite, highly oriented pyrolytihc graphite (HOPG) was used as model substrate. In order to study the adsorption behaviour of modified b-PEI’s onto HOPG different parameters were varied: (i) length of alkyl chain (C8, 14 and C16), (ii) the molar ratio of cationic/alkyl groups and (iii) molecular weight of b-PEI. The adsorption behaviour of these polymers onto HOPG was studied by Scanning Force Microscopy (SFM). Upon deposition on HOPG rod like structure was observed and their confirmation was controlled by the surface coverage and by the two dimensional self-assembly of aliphatic chains. The amount of adsorbed material was found to increase with the length of the used alkyl chain and maximum adsorption was observed for the C16 modified b-PEI. Furthermore, the degree of adsorption onto graphite decreased with the increase in amount of quaternary ammonium groups in the polymer. These primer coatings were applied to carbon fibre and interfacial adhesion between carbon fibre and epoxy resin was demonstrated by well known Kelley Tyson Fragmentation test. The use of primer coating increased the interfacial shear strength by 25% with respect to unsized fibre. U.V. curable coatings prepared were also prepared based on b-PEI. These coatings can be obtained in one step synthesis by polymer analogous reaction with different kind of functional carbonates containing allyl groups with b-PEI.
Degree
thesis:*- Grantor dc:publisher
- Publikationsserver der RWTH Aachen University
- Year dc:date
- 2010
Author and committee
dc:creator, dc:contributor.*- Author dc:creator
-
- Goel, Vishal
- Contributors dc:contributor
-
- Möller, Martin
Subjects
dc:subject × 6Rights
dc:rights- Statement dc:rights
-
- info:eu-repo/semantics/openAccess
- Language dc:language
- eng