Preparation Of Isocyanate Functionalized Polyolefin And Study On Compatibility Of Polyolefin/Nylon 6 Blends

Polymer blending is a very important method for preparing materials with excellent mechanical properties,however,most polymers are thermodynamically immiscible,and polymer blends with excellent mechanical properties can not be obtained via physical blending.In order to improve the compatibility of the blends,it is necessary to add compatibilizers during the blending process.Adding block or graft copolymers into the blends is the most effective means for reactive blending.Obviously,the choice of the suitable compatibilizers is the key issue for the improvement of compatibility of immiscible blends.Hence,two new kinds of compatibilizers were prepared,and the effect on the compatibility of polyolefin/nylon 6 blends was studied in this thesis.A new kind of polar monomer,3-isopropenyl-α,α-dimethylbenzyl isocyanate(TMI)was used to modify the polypropylene(PP)by the melt-grafting method,the effect of influencing factors included DCP concentration,St concentration,TMI concentration,reaction time,reaction temperature and screw speed on the grafting degree was studied.The result showed that TMI was successfully grafted onto PP;St could greatly improve the grafting degree of TMI and reduce the degradation of PP;Through the study on the mechanism,it was believed that when there was St(comonomer)in the reactive system,St was firstly grafted onto PP,then TMI was grafted onto the free radical of St,as a result,alternate copolymer of St and TMI was formed;The process conditions as followed were favorable for the preparation of PP-g-TMI with high grafting degree:PP-100 g,DCP-0.4 g,TMI-10 ml,St-7.5 ml,reaction temperature-190℃,reaction time-10 min,screw speed-60 rpm.Then PP-g-TMI was added into PP/PA6 blends as the reactive compatibilizer,the FT-IR analysis,extraction analysis,balancing torque analysis and DSC analysis confirmed that the PP-g-PA6 copolymer was formed via the reaction between the isocynate functional group(-NCO)of PP-g-TMI and terminal amine group(-NH₂)of PA6.The larger of the grafting degree and content of PP-g-TMI,the more PP-g-PA6 were formed.The result of mechanical property analysis and morphological structure analysis showed that PP-g-TMI could effectively improve the compatibility of PP/PA6 blends;The compatibility was getting better and better when the grafting degree was increased;As the content of PP-g-TMI increasing,the compatibility was firstly improved and then was declined,the best compatibility was obtained when 8 phr PP-g-TMI was added into the blends.The influencing factors on the reactive blending were studied,the result showed that the blending temperature could not be lower than 230℃,blending time could not be less than 10 min and the screw speed should be 60 rpm at least;Besides,the two-step adding method was better than the one-step adding method.The melt-grafting of TMI onto EPDM in the presence of St as comonomer was researched,the FT-IR confirmed the occurrence of the grafting reaction between TMI and EPDM,and the important effect of St for the grafting reaction was also verified.EPDM-g-TMI was added into EPDM/PA6 blends as the compatibilizer,the FT-IR analysis,extraction analysis,balancing torque analysis and recrystallization behavior analysis confirmed the formation of EPDM-g-PA6 copolymer in the reaction between EPDM-g-TMI and PA6 component.The result of glass-transition temperature analysis,impact strength analysis and morphology analysis showed EPDM-g-TMI could effectively improve the compatibility of EPDM/PA6 blends;The compatibility was better when the grafting degree was increased;When the content of EPDM-g-TMI was increased,the compatibility was improved and then was declined,the best compatibility of EPDM/PA6 blends was obtained when 6 phr EPDM-g-TMI was added.On the base of the preparation of PP-g-TMI,a new kind of reactive extrusion method,anion active polymerization was used to synthesize the PP-g-PA6 copolymer,the result of FT-IR analysis showed that the PP-g-PA6 was successfully synthesized.PP-g-PA6 was then added into the PP/PA6 blends as the non-reactive compatibilizer,the morphology showed that PP-g-PA6 could effectively compatibilize the PP/PA6 blends;The compatibility was getting better when the content of PP-g-PA6 was increased,the partical diameter could be reduced to be 200 nm when 6 phr EPDM-g-TMI was added into the EPDM/PA6 blends;The compatibilizing effect of PP-g-PA6 with long PA6 branched chain was better than the PP-g-PA6 with short PA6 chain.