Mechano‐Optical Characterization of Extrusion Flow Instabilities in Styrene‐Butadiene Rubbers: Investigating the Influence of Molecular Properties and Die Geometry

• The extrusion flow instabilities of two commercial styrene-butadiene rubbers are investigated as they vary in isomer content (1,4-cis, 1,4-trans, and 1,2 con- formation) of the butadiene monomer and the molecular architecture (linear, branched). The investigated samples have similar multimodal molecular weight distribution. Two geometries of extrusion dies, slit and round capillary, are compared in terms of the type and the spatial characteristics of the flow instabilities. The latter are quantified using three methods: a highly pressure sensitive slit die, online and offline optical analysis. The highly pressure- sensitive slit die has three piezoelectric pressure transducers (Δt ≈ 10−3 s and Δp ≈ 10−5 bar) placed along the die length. The characteristic frequency (fChar.) of the flow instabilities follows a power law behavior as a function of shear rate to a 0.5 power for both materials, f Char. ∝ γ app.. A qualitative model is used to predict the spatial characteristic wavelength (λ) of the flow instabilities from round capillary to slit dies and vice versa. Slip velocities (Vs) are used to quantify the slippage at slit and round capillary dies as well.

Ämnesord

NATURVETENSKAP  -- Kemi -- Polymerkemi (hsv//swe)

NATURAL SCIENCES  -- Chemical Sciences -- Polymer Chemistry (hsv//eng)

TEKNIK OCH TEKNOLOGIER  -- Materialteknik -- Bearbetnings-, yt- och fogningsteknik (hsv//swe)

ENGINEERING AND TECHNOLOGY  -- Materials Engineering -- Manufacturing, Surface and Joining Technology (hsv//eng)

TEKNIK OCH TEKNOLOGIER  -- Materialteknik -- Textil-, gummi- och polymermaterial (hsv//swe)

ENGINEERING AND TECHNOLOGY  -- Materials Engineering -- Textile, Rubber and Polymeric Materials (hsv//eng)

Nyckelord

qualitative modeling

sharkskin

flow instabilities

die geometry

SBR

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