Toughening of epoxy resin with modified liquid natural rubbers and acrylonitrile-butadiene liquid rubbers

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dc.contributor.authorAbdulali Bashir, Ahmed Ben Saleh
dc.date.accessioned2014-11-14T07:50:36Z
dc.date.available2014-11-14T07:50:36Z
dc.date.issued2005
dc.descriptionPh.Den_US
dc.description.abstractThe preparation of liquid natural rubber (LNR) by depolymerizing deprotenized natural rubber latex was carried out. Similarly, the preparation of epoxidized liquid natural rubber (ELNR) was also undertaken. FTIR and NMR spectroscopis were used to determine the structures of LNR and ELNR and to calculate the epoxidation levels in LNR and ELNR chains. Both LNR and ELNR show the presence of hydroxyl and carbonyl end functional groups. Because of the epoxidation process, ELNR has a higher degree of epoxidation i.e., 25 mol % compared to 8.5 mol% for LNR. LNR and ELNR and two liquid commercial rubbers i.e., ETBN and CTBN were evaluated as toughening agents in an epoxy (DGEPA)-hardener (IPD) system. The four liquid rubbers were evaluated at 5, 10, 15, and 20 phr. The reactivity, thermal, mechanical and morphology properties of the liquid rubbers-EP-IPD systems were evaluated. The fracture toughness was evaluated at three different speeds i.e., 1, 100 and 500 mm/min. A general and similar trend was observed for all liquid rubbers; the gel and cure times increased with increasing of rubber content. The gel and cure temperatures for all the liquid rubbers modified EP are higher than those of the unmodified EP. The glass transition temperatures (Tg) of the modified EP were found to decrease with increasing rubber content. Generally, the tensile strength and Young’s modulus decreased with increase in rubber content followed by increment in tensile strain. The flexural strength and modulus of modified EPs are generally lower than those of the unmodified one. However, the fracture toughness of the EP was observed to improve in the presence of the liquid rubbers. The toughening effect became more apparent as the testing speed was increased. Fracture surface analysis by scanning electron microscopy (SEM) revealed the presence of a two-phase morphology for all the four liquid rubber-EP systems. The rubbery phase was distributed as rubber particles within the epoxy matrix. The gel time for ELNR-EP at 5-15 phr was shorter (4.3 to 4.4) min than for LNR-EP (5.0 to 5.4) min. The cure temperature of the ELNR-EP was between 138-143 °C which are higher than those of the LNR-EP (124-141 °C). ELNR-EP, over the range of rubber loading investigated, has a particle size distribution ranging from 0.2 to 1.88 μm which is much smaller than that of LNR-EP with a distribution ranging from 5 to 10 μm. The reactivity and the particle size distribution results indicate that ELNR is more compatible with EP than LNR. Thus, ELNR-EP, overall, displays higher tensile strength, strain at break, and flexural strength than LNR-EP. At 5 and 10 phr, LNR and ELNR did not give significant improvement in the fracture toughness when compared with ETBN and CTBN. However, at 15 and 20 phr, both LNR and ELNR were found to be good toughening agents for EP giving significant improvement in the KIC, which can be considered quite comparable to ETBN and CTBN depending on the test speeds. Also at 15 and 20 phr, both LNR and ELNR give better overall tensile and flexural properties compared to ETBN and CTBN.en_US
dc.identifier.urihttp://hdl.handle.net/123456789/498
dc.language.isoenen_US
dc.subjectMaterials and Mineral Resources Engineeringen_US
dc.subjectModified liquid natural rubbersen_US
dc.subjectAcrylonitrile-butadiene liquid rubbersen_US
dc.titleToughening of epoxy resin with modified liquid natural rubbers and acrylonitrile-butadiene liquid rubbersen_US
dc.typeThesisen_US
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