Interdiffusion in microlayered polymer composites of polycarbonate and a copolyester

Pollock, G.; Nazarenko, Sergei; Hiltner, A.; Baer, E.

doi:10.1002/app.1994.070520205

Cited by 30 publications

(16 citation statements)

References 14 publications

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“…Occasional articles reported the interdiffusion occurring in the coextrusion process. In a pioneering work, Baer and co-workers studied the interdiffusion in microlayered polymer systems such as PC/copolyesters, 23 nylon/ethylene vinyl alcohol, 24 and high density polyethylene/linear low density polyethylene. 25 They proposed an interdiffusion model based on Fick's diffusion law that related the mutual diffusion coefficient to the change in the glass transition temperatures and crystallization behaviors.…”

Section: Introductionmentioning

confidence: 99%

Critical Role of Interfacial Diffusion and Diffuse Interphases Formed in Multi-Micro-/Nanolayered Polymer Films Based on Poly(vinylidene fluoride) and Poly(methyl methacrylate)

Lü

Lamnawar

Maazouz

et al. 2018

ACS Appl. Mater. Interfaces

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It is known that the macroscopic properties of multilayer polymer films are largely dominated by the diffuse interphase formed via interfacial diffusion between neighboring layers. However, not much is known about the origin of this effect. In this work, we reveal the role of interfacial diffusion and the diffuse interphase development in multilayer polymer films, based on a compatible poly(vinylidene fluoride)/poly(methyl methacrylate) system fabricated by forced-assembly micro-/nanolayer coextrusion. Interestingly, the layer morphology is found to prevail in all investigated multilayer films, even for the nanolayered system where the interdiffusion is substantial. It is also demonstrated that, in the presence of macromolecular and geometrical confinements, interfacial diffusion significantly alters the crystalline morphology and microstructure of the resulting micro-/nanolayered films, which leads to quantitatively different dielectric and rheological properties. More importantly, the combination of dielectric relaxation spectroscopy and energy-dispersive X-ray analysis further reveals that multiple diffuse interphases with various length scales exist in the multilayer structures. The presence of these multiple interphases is explained in terms of a proposed physical picture for the interdiffusion of fast-mode mechanism occurring in the coextrusion process, and their length scales (i.e., interphase thicknesses) are further mapped quantitatively. These findings provide new insights into the effects of interfacial diffusion and diffuse interphases toward tailoring interfaces/interphases in micro-/nanolayered polymer structures and for their advanced applications.

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Section: Introductionmentioning

confidence: 99%

Critical Role of Interfacial Diffusion and Diffuse Interphases Formed in Multi-Micro-/Nanolayered Polymer Films Based on Poly(vinylidene fluoride) and Poly(methyl methacrylate)

Lü

Lamnawar

Maazouz

et al. 2018

ACS Appl. Mater. Interfaces

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“…Static mixers are distributive mixers operating by repeated splitting, stretching, and recombining the polymer melt streams. This concept of blending polymers, which has also been used to generate multilayered blend morphologies (25)(26)(27), has a number of advantages over the commonly used dispersive processing methods for generating in-situ composites. First, the TLCP phase dimensions can be controlled very flexibly by varying the number of mixing elements of the static mixer (20,24).…”

Section: Introductionmentioning

confidence: 99%

Effect of processing history on the morphology and properties of polypropylene/thermotropic liquid crystalline polymer blends

Machiels

Denys

Dam

et al. 1997

Polymer Engineering & Sci

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Preparation, morphology, and mechanical properties were studied of blends of a thermotropic liquid crystalline polymer (TLCP) with two different grades of polypropylene, one with and one without overlap in processing temperatures, using two different blending methods. The highly viscous grade (PP-1) was of sufficient thermal stability to be blended with the TLCP (Vectra A950) in a single-screw extruder with an Egan mixing section on the screw. The low viscous grade (PP-2) could not be processed at the same temperature a s the TLCP because of degradation. Its blends were, therefore, prepared by a special coextrusion technique, i.e. feeding the two components from two separate extruders to a Ross static mixer. In both methods drawing of the extrudate is necessary to obtain satisfactory mechanical properties. The PP-1 /TLCP blends had to be extruded twice in order to obtain proper mixing. The morphology of these blends ranges from a pronounced skin-core morphology at low extrudate draw ratio (DR = 3) to a high-aspect ratio fiber/matrix morphology at high draw ratio (DR = 15). The morphology of the PP-2/TLCP blends was always a high-aspect ratio fiber/matrix morphology even at low draw ratios.The TLCP fibers were generated in this coextrusion process under conditions where the viscosity of the dispersed phase was higher than the viscosity of the matrix. Breakup experiments demonstrate that fibers of a thickness of approximately 1 pm disintegrate into droplets within a few seconds at temperatures above the melting point of the TLCP. This is probably the cause of the skin-core morphology obtained with single-screw extrusion. Tensile modulus and strength of all blends increase with extrudate draw ratio. The deformation of the TLCP phase in the drawn blends is less than affine, probably because of slip between the phases. The moduli of the PP-1/TLCP blends as a function of the draw ratio can be described well by a modified Halpin-Tsai equation taking into account both changes in aspect ratio and molecular orientation of the TLCP fibers. The level of reinforcement in the PP-2/ TLCP blends is lower than expected, probably because of the low temperature of drawing. This demonstrates a limitation of the coextrusion process: blending at temperatures that are too low reduces mechanical properties.

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“…The concentration profiles for different times were obtained by solving Ficks equation with a step-function profile at zero time and zero composition gradient at both boundaries of the interdiffusion element at any time during diffusion. A similar analysis was introduced previously when interdiffusion was studied in polycarbonate-copolyester microlayers (4,5).…”

Section: Novel Structures B Y Microlayer Coextrusionmentioning

confidence: 84%

“…Subsequently, interdiffusion can be investigated in a controlled manner. For example, by using microlayers, it was possible to study interdiffusion of polycarbonate (PC) and a miscible copolyester (Kodar) in short term experiments (4,5).…”

Section: Introductionmentioning

confidence: 99%

Novel structures by microlayer coextrusion—talc‐filled PP, PC/SAN, and HDPE/LLDPE

Mueller

Nazarenko

Ebeling

et al. 1997

Polymer Engineering & Sci

136

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Numerous examples in the literature illustrate how the coextrusion of film with three or more polymeric layers is economically used to achieve a desirable mix of end‐use characteristics. More recently, layer‐multiplying devices permit two polymers of widely dissimilar solid‐state properties to be combined into unique microlayer and nanolayer structures with hundreds or thousands of alternating layers. If the layers are thin enough, the key properties of the constituents can combine synergistically. The microlayer structure is also an effective research tool. Because the microlayer and nanolayer structures contain large specific interfacial areas, they are ideal for fundamental studies of phenomena such as interdiffusion and adhesion. Three examples of microlayered materials with up to 1024 layers illustrate the versatility of this coextrusion process: talc‐filled PP, PC/SAN, and HDPE/LLDPE.

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Interdiffusion in microlayered polymer composites of polycarbonate and a copolyester

Cited by 30 publications

References 14 publications

Critical Role of Interfacial Diffusion and Diffuse Interphases Formed in Multi-Micro-/Nanolayered Polymer Films Based on Poly(vinylidene fluoride) and Poly(methyl methacrylate)

Critical Role of Interfacial Diffusion and Diffuse Interphases Formed in Multi-Micro-/Nanolayered Polymer Films Based on Poly(vinylidene fluoride) and Poly(methyl methacrylate)

Effect of processing history on the morphology and properties of polypropylene/thermotropic liquid crystalline polymer blends

Novel structures by microlayer coextrusion—talc‐filled PP, PC/SAN, and HDPE/LLDPE

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