Prediction of processability at extrusion coating for low‐density polyethylene

The effect of processing history in a singlescrew extruder on molecular characteristics was studied by employing commercially available low-density polyethylene with no additives. Generation of long-chain branch, which is responsible for the neck-in phenomenon and draw resonance, is indicated by nonlinear viscoelastic properties of the extruded samples. Consequently, the processed samples show higher level of elastic property than the original pellet. However, thermal analysis revealed that there is no change in the distribution of short-chain branch. Moreover, both chain scission and cross-linking take place, and the chain scission is predominant above 320 C. Furthermore, processing history at low temperature depresses the melt elastic nature, although primary molecular structure is unchanged. This would be attributed to shear modification phenomenon.

Section: Resultsmentioning

confidence: 98%

“…This is very important for extrusion coating because the intensity of strain-hardening determines the degree of neck-in. 36 Further, the draw resonance would also be diminished by the increase of strain-hardening.…”

Section: Viscoelastic Propertiesmentioning

confidence: 99%

Thermal and mechanical modification of LDPE in single‐screw extruder

Ono

Yamaguchi

2009

“…3,4 In this part of our study, various grades of LDPE have been selected to verify the relationship between Neck-in and LCB. 3,4 In this part of our study, various grades of LDPE have been selected to verify the relationship between Neck-in and LCB.…”

Section: 65mentioning

confidence: 99%

“…Polymer Structure Property Relationship-Relationship of LCB and Processing Properties LCB is one of the most important microstructures that influences the processing properties, especially on Neck-in level. 3,4 In this part of our study, various grades of LDPE have been selected to verify the relationship between Neck-in and LCB. The processing test was investigated by using a laboratory extrusion coating (Collin, Germany) with fixing line speed of 4 and 12 m min 21 .…”

Section: 65mentioning

confidence: 99%

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Methods of long chain branching detection in PE by triple‐detector gel permeation chromatography

Pathaweeisariyakul

Narkchamnan

Thitisuk

et al. 2015

Long chain branching (LCB) in polyethylene is one of the key microstructures that controls processing and final properties. Gel permeation chromatography (GPC) with viscometer (IV) and/or light scattering (LS) has been intensely used to quantify LCB. The widespread method to quantify LCB from GPC with IV or LS is the method of LCB frequency (LCBf) based on the Zimm-Stockmayer (ZS) random branching model. In this work, the conventional approach was compared with the recently developed method, called gpcBR. The comparison of the sensitivity of both methods is made on highly branched polymer, that is, various grades of commercial LDPE and also on polymer with very low level of LCB, that is, a commercial HDPE with no LCB, converted into several branched test samples of gradually increasing LCB by multiple extrusion. Finally, the linkages of LCB quantities from both methods to the rheological data and processing properties are illustrated. The new gpcBR index can access lower LCB level and shows obviously better relationship with both rheological data and processing properties than LCBf from the conventional ZS model.

Processability and mechanical properties for binary blends of PP and LLDPE produced by metallocene catalyst

Ono

Ogita²,

Okamoto

et al. 2009

Processability at extrusion coating and mechanical properties of the films obtained are investigated by means of linear and nonlinear rheological measurements and tensile tests for blends of polypropylene (PP) and linear low-density polyethylene (LLDPE). Both materials are produced by metallocene catalyst. The processability of PP is found to be improved by the addition of LLDPE; the blend shows low level of motor torque and head pressure in an extruder and small level of neck-in as compared with pure PP.Further, the anisotropy of ultimate tensile strength, which is prominent for PP, is reduced by blending with LLDPE. As a result, the blend having 20 wt % of LLDPE shows appropriate properties in the molten state for extrusion coating and in the solid state as a film.