Abstract
Polyetheretherketone (PEEK)/polyetherimide (PEI) blends (50/50, v/v) keeping the crystal phase of PEEK have been manufactured by alternate PEEK/PEI layer stacking. This strategy avoided the complete miscibility of both polymers, keeping layers of PEEK and PEI unmixed along the sample thickness, as well as promoting the formation of a smooth interfacial layer where PEEK and PEI were mixed. The properties of this interface after processing at molten state and different times was studied by DSC, DMA, and X-Ray synchrotron. These techniques allowed monitoring the evolution of glass transition, where isolated Tg’s for both pristine polymers were observed even after long processing time. PEEK crystallinity slightly decreased during manufacturing, whereas PEEK crystal parameters did not vary. These observations show that, although the interface—the zone where both polymers are mixed—grew, layers with pristine polymers remained even after prolonged processing time. The preservation of the PEEK crystallinity was also observed in the mechanical properties of the multilayer PEEK/PEI films, which were compared with pristine PEEK and PEI films. Multilayer samples processed for shorter times rendered higher young modulus, tensile strength, and strain at break.
Highlights
The development of technologically relevant polymer blends and polymer composites depends on the synergistic combination of two or more polymers with the aim to improve the final properties [1,2,3].Sometimes, single polymer components do not reach the end use requirements, necessitating the use of a combination of two or more polymers
This fact ensures good adhesion between layers of PEEK and PEI due to the formation of an interface where PEEK and PEI are mixed. In these multilayers of PEEK/PEI (50/50) the growing of the interface during the processing time at 400 ◦ C, considering the interface as the region where PEEK and PEI coexist, has to be associated with a decrease of PEEK crystallinity, which can be followed by DSC
Harris et al [2] observed that PEEK–PEI blends containing as little as 30% of PEEK were crystallizable but both crystallization kinetics and crystallinity itself were decreased [2,11]
Summary
The development of technologically relevant polymer blends and polymer composites depends on the synergistic combination of two or more polymers with the aim to improve the final properties [1,2,3].Sometimes, single polymer components do not reach the end use requirements, necessitating the use of a combination of two or more polymers. The properties of the final material depend strongly on the morphology, processing history, formulation, and interactions between the individual components [4]. Multilayer films have demonstrated their importance in the commercial marketplace due to their excellent optical, gas barrier, mechanical, or dielectric properties [3]. These unique properties have allowed multilayer films to be employed in several applications such as infrared (IR), visible, or ultraviolet (UV) light reflectors, films for toughness enhancing and selectivity filtering IR or UV radiation in glass window, flexible barriers in food packaging, medical applications, etc
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