Rheological properties of injection molded LDPE and mPE foams

Abstract

The rheological properties of molten LDPE and mPE foams have been measured for small‐amplitude oscillatory shear flow. The foam samples were prepared by injection molding, and the effect of injection conditions on the resultant cell structure is discussed. In all cases cellular foams with closed cells were obtained with cell densities in the range of 4 × 105 − 7 × 106 cells/cm3 and cell diameters in the range of 30–110 μm. The viscoelastic behavior of the foams is shown to be well described by the emulsion model proposed by Palierne (1) without using any fitting parameter. The linear viscoelastic properties of LDPE and mPE foams depend only on the properties of the polymer matrix and of the gas volume fraction. The Palierne model is also used to predict the linear properties of microcellular foams. Polym. Eng. Sci. 44:2158–2164, 2004. © 2004 Society of Plastics Engineers.

Microcellular injection molded polylactic acid/poly (ε-caprolactone) blends with supercritical CO2: Correlation between rheological properties and their foaming behavior

“…Polymeric foams are lightweight structural materials with low density, high impact resistance, and also good insulation property. The main commercial interest for microcellular foams is based on the claim that mechanical properties would remain those of the base polymer, along with a significant density reduction . However, the main challenges for the current foamed packaging made from synthetic polymers are to recycle cost‐effectively, and subsequently only a very small proportion is recycled, with the vast majority going to landfill .…”

The effect of injection molding conditions on the morphology of polymer structural foams

“…The rheological behavior of the gas-laden polymer melts in terms of viscoelasticity and elongational effects has been the subject of several studies in the past [7][8][9][10][11]. The effect of shear and elongational viscosity of low density polyethylene (LDPE) in foaming has been investigated in several works [7,8]. Qin et al [9] also studied the rheological behavior of foam flow during injection mold filling.…”

“…For this reason, it is more complex to predict the final foam morphology [21]. During the injection molding process, two driving forces control the bubble growth: hydrodynamics and mass transport [5][6][7][8][9][10]. Several experimental studies are available on bubble growth and cell structure for injection molded foams [5,22,23].…”

Foamability and Special Applications of Microcellular Thermoplastic Polymers: A Review on Recent Advances and Future Direction

“…Thermoplastic polymeric materials used for foaming can be classified into two broad categories, namely, homopolymers and multiphase polymeric materials. Homopolymers can be crystalline/semi‐crystalline (such as PP, [ 19,31 ] high density of polyethylene (HDPE), [ 16,58 ] low density PE (LDPE), [ 59–62 ] linear LDPE (LLDPE), [ 63 ] nylons, [ 64,65 ] polylactide (PLA), [ 66 ] poly(ε‐caprolactone) (PCL), [ 67 ] poly(butylene adipate‐ co ‐terephthalate) (PBAT), [ 68 ] poly(butylene succinate) (PBS) [ 69 ] ) or amorphous (such as PS, [ 70 ] polycarbonate (PC), [ 70–73 ] poly(vinyl chloride) (PVC), [ 74,75 ] poly(vinyl alcohol) (PVA) [ 76 ] ). Of the homopolymers used for foaming, PLA, PCL, PBAT, PBS, and PVA are biodegradable.…”