Influence of rheological properties on the sagging of polypropylene and abs sheet for thermoforming applications

Lau, Hoong Chuin; Bhattacharya, S. N.; Field, G.

doi:10.1002/pen.11286

Cited by 25 publications

(32 citation statements)

References 10 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The figures also display multi-mode XPP and RP-S equation fits to the experimental data. Fitting parameters for the XPP and RP-S equations were tabulated earlier in Table ( [4][5][6].…”

Section: Non-linear Rheologymentioning

confidence: 99%

Extrusion film casting of long chain branched polypropylene

et al. 2014

View full text Add to dashboard Cite

Extrusion film casting (EFC) is an important melt processing operation which is extensively used to make polypropylene (PP) films. Linear PP shows significant amount of necking and draw resonance during EFC. One of the ways to reduce necking is to introduce long chain branches (LCB) on the polymer backbone. The long branches impart extensional strain hardening behavior thereby stabilizing the melt flow. In this work, we investigate the influence of long chain branching in polypropylene on the extent of necking in the EFC process. Laboratory scale EFC experiments were performed on homopolymer PP of linear and long chain branched architectures. Simulations of the EFC process were carried out using the one‐dimensional flow model of Silagy et al., Polym. Eng. Sci., 36, 2614 (1996) into which we incorporate two different multi‐mode molecular constitutive equations namely, the ‘eXtended Pom‐Pom’ equation (XPP, for long chain branched PP) and the ‘Rolie‐Poly’ equation (RP‐S, for linear PP). Our experimental data confirm that presence of long chain branching in PP reduces the extent of necking and our numerical predictions show qualitative agreement with experimental data, thereby elucidating the role of chain architecture on the extent of necking. POLYM. ENG. SCI., 55:1977–1987, 2015. © 2014 Society of Plastics Engineers

show abstract

“…The figures also display multi-mode XPP and RP-S equation fits to the experimental data. Fitting parameters for the XPP and RP-S equations were tabulated earlier in Table ( [4][5][6].…”

Section: Non-linear Rheologymentioning

confidence: 99%

Extrusion film casting of long chain branched polypropylene

et al. 2014

View full text Add to dashboard Cite

show abstract

“…Wang et al [1] performed uniaxial tensile experiments using a Meissner-type rheometer to measure the properties of ABS and proposed a material model that considers the effects of strain rate, strain hardening, and temperature sensitivity. Lau et al [2] showed that ABS exhibited high resistance to sheet sag because of its high viscosity and high modulus of elasticity. Because of its broader molecular weight distribution, polypropylene had a sag resistance lower than that of ABS.…”

Section: Literature Reviewmentioning

confidence: 99%

Rheological measurement of the nonlinear viscoelasticity of the ABS polymer and numerical simulation of thermoforming process

Cha

Song

Hyun

et al. 2020

Int J Adv Manuf Technol

View full text Add to dashboard Cite

The thickness distribution of thermoformed products is greatly affected by the viscoelastic behavior of the extruded polymer sheet. In this work, linear and nonlinear rheological experiments are carried out to characterize the viscoelastic properties of acrylonitrile-butadiene-styrene sheets under thermoforming conditions including a wide range of temperatures, strains, and strain rates. First, aspects of linear viscoelasticity such as the storage modulus and loss modulus are measured by small-amplitude oscillatory shear experiments. The discrete relaxation spectra and the Williams-Landel-Ferry parameters are obtained from the constructed linear master curves. Then, nonlinear time-dependent extensional viscosity is measured by uniaxial extensional experiments. The parameters of the damping function are evaluated using an optimization method. In addition, the effect of the orientation of the polymer is analyzed. The uniaxial extensional stress and viscosity in the extruder direction demonstrate higher resistance against tearing and extreme thickness reduction during processing. Finally, the linear and nonlinear input parameters for the numerical simulation are prepared. Numerical simulations are performed using the Wagner model with the obtained nonlinear viscoelasticity. The thickness distribution in thermoformed ABS sheets, obtained numerically, shows good agreement with the experimentally obtained values.

show abstract

“…Numerical results are compared with experimental results for a simple rectangular cup. Lau et al [12] studied sagging behavior of different materials, such as polypropylene and ABS used for thermoforming. The dynamic shear test was conducted to measure viscoelastic properties, such as the storage modulus, loss modulus, and complex viscosity.…”

Section: Introductionmentioning

confidence: 99%

Experimental determination of the viscoelastic parameters of K-BKZ model and the influence of temperature field on the thickness distribution of ABS thermoforming

Cha

Kim

Park

et al. 2019

Int J Adv Manuf Technol

View full text Add to dashboard Cite

This study investigated an influence of the temperature field on thickness distribution of thermoformed products using complex and high-aspect-ratio mold. The optimum temperature field was obtained to achieve a more uniform thickness distribution in the thermoformed products by using finite element simulation. The material properties of acrylonitrile-butadiene-styrene (ABS) polymer sheet were obtained by two rheological measurement tests. The linear viscoelastic properties, such as the storage modulus and loss modulus, were measured by a small amplitude oscillatory shear (SAOS) test for wide ranges of frequency and temperature. The discrete relaxation time and discrete relaxation modulus were obtained by nonlinear regression. The fitting parameters C 1 and C 2 for the WLF model were obtained by curve fitting. The nonlinear viscoelastic property, such as stress relaxation modulus, was measured by a step strain test. The damping function and fitting parameter α of Wagner-Demarmels (WD) model were determined by curve fitting. Then, the Kaye-Bernstein-Kearsley-Zapas (K-BKZ) constitutive equation was utilized to the thermoforming simulation in order to investigate the material behavior of the polymer sheet. The numerical results showed that a more uniform thickness distribution could be achieved with the optimum temperature field of the sheet. The thinnest part of the products was improved by more than 30%.

show abstract

Influence of rheological properties on the sagging of polypropylene and abs sheet for thermoforming applications

Cited by 25 publications

References 10 publications

Extrusion film casting of long chain branched polypropylene

Extrusion film casting of long chain branched polypropylene

Rheological measurement of the nonlinear viscoelasticity of the ABS polymer and numerical simulation of thermoforming process

Experimental determination of the viscoelastic parameters of K-BKZ model and the influence of temperature field on the thickness distribution of ABS thermoforming

Contact Info

Product

Resources

About