Study On Creep Behaviors Of PLLA/EVA Immiscible Blends By Adding Nanofillers

Polymer blending has been demonstrated an efficient way to prepare the new high-performance materials with relatively low research&design costs and high ability to be popularized.To date,various polymer blends have been developed and widely used in many fields ranging from building,package,automobile and electronic element to aerospace.Incorporating nanofillers into the polymer blends has then attracted the interest of researchers.The roles of nanofillers in the blends are various,such as compatibilizing effect,reinforcing effect,toughening effect or endowing the materials with other functional properties,such as conductive performance,flame retardance,electromagnetic shielding,gas barrier effect,etc.As one of the main parameters which reflect the service behavior of articles under the long-term load condition,creep stability is widely used to evaluate the dimensional stability of the structural materials under a persistent load.Good creep stability means a long service life of articles in practical application.However,researches about the creep stability of the polymer blend composites are relatively few,which restricts the application of materials to some extent.In order to explore the influencing factors of creep behavior in ternary nanocomposites,CNTs were first introduced into the immiscible polymer blends in this work.The effects of CNTs on morphology and creep behavior were investigated systematically.At the same time,annealing treatment explore the influence of crystal structure on the creep behavior.Further the interaction of immisible blends was regulated by changing the VA content and the prerequisite of ternary nanocomposite creep behavior was comparatively investigated.Besides,by considering the factors which affected the selective location of OMMT to regulate the location of OMMT in one phase,study the dispersion of nanofiller in the single-phase on the influence of materials microstructure and creep behavior.The main results obtained in this work are listed as follows:(1)CNTs are introduced into PLLA/EVA binary immiscibly blends through melt-blending.Morphology characterization finds that the nanocomposites prepared through PLLA master batch,CNTs selectively distribute at the interface between two phases and a few distribute in the PLLA phase;the nanocomposites prepare through EVA master batch,CNTs selectively distribute at the interface between two phases and a few distribute in the EVA phase.Further results demonstrate that the creep stability of the immiscible blend is apparently enhanced by adding CNTs.The mechanisms for the enhance creep stability are suggested to be related to the interfacial location of CNTs at the blend interface,the formation of the percolate CNT network structure as well as the morphological changes induced by CNTs.Further enhanced creep stability can be achieved by introducing crystalline structure to PLLA matrix,which is realized by annealing treatment.(2)A series of PLLA/EVA/CNT blend composites are prepared by regulating VA content.It find that the change of VA content does not affect the dispersion of CNTs,but can affect the microstructural morphology of the nanocomposites through the morphology characterization.When the VA content is relatively low(EVA is plastic),the creep rate is lower,although the initial creep of the composite strain is larger;when the VA content is relatively high(EVA is rubber elastomer),the initial creep strain is small,but the creep rate is relatively large.(3)OMMT is introduced into PLLA/EVA immiscible blends through melt-blending,OMMT selectively distribute in the PLLA phase,this prove the reality of the theoretical calculation.Furthermore,OMMT induce the apparent change of the blend morphologies.Rheological measurements show that OMMT form the percolated network structure at relatively high content.The mechanical properties are measured through universal tensile measurements.The results show that OMMT exhibited excellent reinforcement effect.The tensile creep behaviors of samples are evaluated at different external forces.It is demonstrated that incorporating OMMT into the immiscible PLLA/EVA blends facilitated the apparent enhancement of creep stability.The mechanisms are suggested to be related to the morphological change induced by OMMT and the formation of the percolated OMMT network structure in the blend composites.