GRAFT COPOLYMERIZATION OF p-ACRYLOYLOXYBENZOIC ACID AND p-METHACRYLOYLOXYBENZOIC ACID ONTO ISOTACTIC POLYPROPYLENE
The monomers, p-acryloyloxybenzoic acid (ABA) and p-methacryloyloxybenzoic acid (MBA) were synthesized by condensation reaction of corresponding acid chlorides with p-hydroxybenzoic acid in alkaline medium. The polymerization of the monomers were studied by several techniques. Polyacryloyloxybenzoic acid (PABA) was obtained by & / #947 / -radiation induced, solution and bulk melt polymerization by initiation of dicumyl peroxide (DCP). Polymethacryloyloxybenzoic acid (PMBA) could be obtained by only bulk melt polymerization.
The graft copolymerization of the monomers onto isotactic polypropylene, IPP, was successfully carried out only with bulk melt polymerization. The IPP used in the graft copolymerization was firstly subjected to & / #947 / -radiation to create active sites for grafting. The graft copolymerization of the monomers, ABA and MBA onto IPP were initiated by these active sites. The grafting was studied at constant concentration of the monomers in the reaction mixture (50%) and at different reaction temperatures (170, 185, 202, 215 and 225° / C). The maximum grafting of PABA and PMBA were found to be 33.1% and 33.9% in the graft copolymers, respectively. The maximum grafting was reached in shorter times at higher temperatures, and it also increased with the increase of concentration of the monomers in the reaction medium. The graft copolymerization was also carried out
by using initiator, DCP at 170° / C, however, the grafting extent was lower due to the homopolymerization of the monomers and the direct reactions between peroxides of initiator and peroxides on IPP.
The graft copolymers were characterized by several techniques, DSC, WAX, TG/IR, MS, SEM and mechanical testing. The formation of both crystalline forms of (& / #61537 / 1 and & / #61537 / 2) were observed in the products obtained at 170° / C. The graft copolymerization of ABA did not have any significance on the formation of both forms of & / #61537 / form, while MBA lead to increase in & / #61537 / 2 form. The & / #61538 / crystalline modification formed in PABA-g-PP products obtained at 185° / C and at higher temperature and also in the second run of DSC studies after fast cooling. & / #61538 / form was not observed in graft copolymers of PMBA
The decomposition mechanism of PABA, PMBA and the graft coproducts were studied by mass spectrometry and TG/IR. The polymers degraded predominantly by decomposition of side groups giving phenol, benzoic acid, hydroxybenzoic acid, carbondioxide and cyclodiene mainly.
The mechanical properties of the graft copolymers showed an improvement particularly in tensile strength and modulus. The maximum tensile strength and modulus of PABA-g-PP were found as 41.1 and 881 MPa, and the values of PMBA-g-PP were measured as 35.9 and 721 MPa, respectively. These values were 28.1 and 486 MPa for irradiated IPP and 33.9 and 632 MPa for virgin IPP, respectively. The copolymerization of ABA did not alter the impact properties of the graft copolymer, while a slight decrease was observed in PMBA-g-PP samples.
The tensile and impact fractured surface of the graft copolymers studied by scanning electron microscopy showed homogeneous structure. The brittle nature with some extent of ductility was seen in the samples.
| Identifer | oai:union.ndltd.org:METU/oai:etd.lib.metu.edu.tr:http://etd.lib.metu.edu.tr/upload/12605177/index.pdf |
| Date | 01 July 2004 |
| Creators | Cetin, Sedat |
| Contributors | Tincer, Teoman |
| Publisher | METU |
| Source Sets | Middle East Technical Univ. |
| Language | English |
| Detected Language | English |
| Type | Ph.D. Thesis |
| Format | text/pdf |
| Rights | To liberate the content for public access |
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