ABSTRACT:The imbedded fiber retraction method was used to assess the effect of increasing octene content and comonomer type on the compatibility of polypropylenepolyolefin elastomer (PP-POE) blends via direct measure of the interfacial tension. The interfacial tension was found to decrease monotonically with increasing octene content from a starting value of 1.5 { 0.16 dyn cm at an initial octene level of 9% down to 0.56 { 0.07 dyn cm at an octene content of 24%. These effects can be interpreted in terms of the effective decrease in the molecular weight between chain ends for the branched POE materials. The experimental data were found to be described well by a modification of the empirical relationship used to describe the effect of molecular weight on the interfacial tension for linear materials. The power-law parameter was found to be numerically equivalent for that obtained for the molecular weight dependence of linear materials. The measured interfacial tension was also found to be dependent on the type of comonomer used in the PP-POE systems. The interfacial tension ranged from 1.07 { 0.09 dyn cm for a PP-POE system made using ethylene-propylene down to 0.56 { 0.07 dyn cm for a PP -POE made using ethylene -octene ( 24% octene ) .
in Wiley Online Library (wileyonlinelibrary.com).Polyethylene (PE) has relatively poor adhesion with polar polymeric materials. In an effort to improve the adhesion between PE and thermoplastic polyurethane (TPU), maleic anhydride (MA), hydroxyl (OH), and secondary amine (NHR) functionalized PEs were blended into nonmodified PE. These functional groups will react with urethane linkages in TPU at the temperature of melt processing. We bonded these PEs to TPU via lamination and coextrusion. To compare the two processes, we determined the interfacial copolymer density R considering both advection and interfacial area generation. We found that the development of adhesion in coextrusion was much faster in comparison with lamination at the same temperature. This difference was attributed to the extensional and compressive flow in coextrusion overcoming the diffusion barrier at the interface and forcing reactive species to penetrate the interface. The effects of functional group reactivity and processing variables on adhesion were correlated with interfacial copolymer coverage. Amine functionalized PE showed dramatic adhesion improvement even at 1 wt %.
Primary and secondary amino-functionalized polyethylenes were synthesized from commercially available maleic anhydride-modified polyethylene by reaction with mono-tert-butoxycarbonyl-protected diamines, N-(tert-butoxycarbonyl)-1,6-diaminohexane (tBocHMDA), and N-(tert-butoxycarbonyl)-N-ethyl-1,6-diaminohexane (tBocEtHMDA) followed by deprotection with trifluoroacetic acid. The structures of amino-functionalized polyethylenes were characterized by NMR and IR spectroscopies, and the data compared favorably to that of the corresponding model compounds. The amino-functionalized polymers showed significantly improved adhesive strength toward thermoplastic polyurethanes as compared to the parent maleic anhydride-modified polyethylene.
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