Experimental study of elongational flow and failure of polymer melts

Abstract

SynopsisA new and simple instrument for measurement of elongational flow response of polymer melts in constant uniaxial extension rate experiments is described. Quantitative stress development data are presented for a series of low-density polyethylene (LDPE), high-density polyethylene (HDPE), polystyrene (PS), polypropylene (PP), and poly(methy1 methacrylate) (PMMA) melts. For small elongation rate E, linear viscoelastic behavior was observed; while for large E, LDPE and PS showed exponential stress growth, while HDPE and PP showed only linear stress growth. Stress relaxation experiments were carried out for several of the same melts in the instrument. Elongation to break and mechaniims of f i i e n t failure were studied. HDPE and PP have a tendency to neck and exhibit ductile failure, while a t high E, LDPE and PS seem to show cohesive fracture. The elongational flow stress response data were compared to predictions of nonlinear viscoelastic fluid theory, specifically the Bogue-White formulation. The qualitative differences in responses of the melts studied were explained in terms of different dependences of the effective relaxation times on deformation rate and, more specifically, on values of the a parameter in the theory.

Time dependent effects on the rupture of molten linear polymers in extension

“…These include for example the works by Ide and White [9,10], where experimental data on limiting strain at break are reported for high-density polyethylene (HDPE), low-density polyethylene (LDPE), polypropylene (PP), polystyrene (PS) and poly(methyl methacrylate) (PMMA). In this work, the authors have found that HDPE would fail by ductile failure, while LDPE would have a failure behaviour dependent on the applied strain rate.…”

Rheological properties of branched low‐density polyethylene

“…Note in Table I our discussion below, let us consider the elongational viscosities of three resins, Dow PE510, Norchem PE952, and Rexene PE143, one from each resin manufacturer. It is seen in Figure 19 that Rexene PE143 has the lowest V E of the three resins under consideration, i.e., (7E)Rexene 143 < (VE)Dow 510 < (VE)Norchem 952 (9) Referring to Table I, the breadth of MWD of the three resins has the following ordering:…”

A Novel Elongational Rheology Control of PS by SBS and Dicumyl Peroxide

“…Extensive studies about elongational rheology indicate that strainhardening is sensitive to molecular weight distribution and long-chain branching. [1][2][3][4][5][6][7][8][9][10][11][12] In recent years, the introduction of a small mass fraction of extremely high molecular weight component into normal molecular weight polymer has been attractive and noticeable because of its effective method of strain-hardening enhancement. 2,[8][9][10][11][12] This is in harmony with the picture of PS/SBS treated at high temperature.…”