Rheological investigation of form relaxation and interface relaxation processes in polymer blends

In this work, the morphology and linear viscoelastic behavior of PMMA/PP blends to which a graft copolymer PP‐g‐PMMA has been added was studied. The copolymer concentration varied from 1 to 10 wt % relative to the dispersed phase concentration. The rheological data were used to infer the interfacial tension between the blended components. It was observed that PP‐g‐PMMA was effective as a compatibilizer for PMMA/PP blends. For PP‐g‐PMMA concentration added below the critical concentration of interface saturation, two rheological behaviors were observed depending on the blend concentration: for 70/30 blend, the storage modulus, at low frequencies, increased as compared to the one of the unmodified blend; for 90/10 blend, it decreased. For 90/10 blend, the relaxation spectrum presented an interfacial relaxation time related to the presence of the compatibilizer (τβ). For PP‐g‐PMMA concentrations added above the critical concentration of interface saturation, the storage modulus of all blends increased as compared with the one of the unmodified blend. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013

Section: Discussionsupporting

confidence: 87%

Section: Resultssupporting

confidence: 73%

Linear viscoelastic behavior of compatibilized PMMA/PP blends

Souza

Calvão

Demarquette

2012

“…λ versus λ (relaxation time) and using the location of the maximum in the resulting curve as the relaxation time for the droplets 45. The rheological material functions G ′ and G ′′ were used to calculate relaxation time spectra and to determine characteristic relaxation times 47. The Carreau–Yasuda model used to determine the zero shear viscosity and relaxation time.…”

Section: Resultsmentioning

confidence: 99%

Investigation on the correlation between rheology and morphology of PA6/ABS blends using ethylene acrylate terpolymer as compatibilizer

Mojarrad

Jahani

Barikani

2010

Phase morphology and rheological behavior of polyamide 6 (PA6)/acrylonitrile butadiene styrene (ABS) polymers blends was studied using scanning electron microscopy and rheometry. The results showed that the phase morphology and rheological properties depends on blend composition. We evaluated the effect of addition of ABS as dispersed phase and EnBACO-MAH (ethylene n-butyl acrylate carbon monoxide maleic anhydride) as a compatibilizer on the morphological and rheological behaviors of PA6/ ABS blends. It was concluded that there is a good agreement between the results obtained from rheological and morphological studies. As a consequence, addition of the ABS and compatibilizer weight percent led to a significant change in morphological structure and a great mounting in the viscosity as well as the elasticity. The rheological properties results demonstrate that adding compatibilizer to polymer blends led to increasing the crossover point, which shows a transition from a high viscous to a considerably more elastic behavior. Also, the slow transition of relaxation time peak from the peak of the PA6 to the peak of the ABS implies increasing the miscibility of the PA6/ABS blend components by increasing compatibilizer content. In addition, the Carreau-Yasuda model was used to extract information on rheological properties (zero shear viscosity and relaxation time) for PA6/ABS/EnBACO-MAH blends by fitting the experimental data with this model.

“…From a microscopic point of view, the presence of these molecular species enlarges the thickness of the interface. Friedrich's team was the first to obtain experimental evidences of viscoelastic features of an interface 42–44. They found a characteristic signature of a thick interface in blends of PS/PMMA with 1 wt % of symmetric diblock copolymer poly(styrene‐ b ‐methyl methacrylate), P(S‐ b ‐MMA), or poly(cyclohexyl methacrylate‐ b ‐methyl methacrylate), P(CHMA‐ b ‐MMA).…”

Section: Results and Discusionmentioning

confidence: 99%

The role of the interface in melt linear viscoelastic properties of LLDPE/LDPE blends: Effect of the molecular architecture of the matrix

Robledo¹,

Vega²,

Nieto³

et al. 2009

The rheological properties of blends consisting of a long chain branched low-density polyethylene (LDPE) and two linear low-density polyethylenes (LLDPE) are studied in detail. The weight fractions of the LDPE used in the blends are 5 and 15%. The linear viscoelastic characterization is performed at different temperatures for all the blends to check thermorheological behavior and miscibility in the melt state. Blends containing metallocene LLDPE as the matrix display thermorheologically complex behavior and show evidences of immiscibility in the melt state. The linear viscoelastic response exhibits the typical additional relaxation ascribed to the form deformation mechanism of dispersed phase droplets (LDPE). The Palierne model satisfactorily describes the behavior of these blends in the whole frequency range explored. However, those blends with Ziegler-Natta LLDPE as the matrix fulfill the time-temperature superposition, but exhibit a broad linear viscoelastic response, further than the expected for an immiscible system with a sharp interface. The rheological analysis reveals that, in addition to the droplets form relaxation, another mechanism at lower frequencies exists. The broad linear response of the blends with the ZieglerNatta LLDPE can be explained by hypothesizing a strong interaction between the high molecular weight linear fraction of the LLDPE and the low molecular weight (almost linear) chains of the LDPE phase, forming a thick interface with its own viscoelastic properties.