PMID- 18348582
OWN - NLM
STAT- PubMed-not-MEDLINE
DCOM- 20080611
LR  - 20080430
IS  - 0743-7463 (Print)
IS  - 0743-7463 (Linking)
VI  - 24
IP  - 9
DP  - 2008 May 6
TI  - Confined flow of polymer blends.
PG  - 4494-505
LID - 10.1021/la7036636 [doi]
AB  - The influence of confinement on the steady-state morphology of two different 
      emulsions is investigated. The blends, made from polybutene (PB) in 
      polydimethylsiloxane (PDMS) and polybutadiene (PBD) in PDMS, are sheared between 
      two parallel plates, mostly with a standard gap spacing of 40 microm, in the 
      range of shear rates at which the transition from "bulk" behavior toward 
      "confined" behavior is observed. For both cases, the influence of the 
      concentration was systematically investigated, as well as the shear rate effects 
      on the final steady-state morphology. By decreasing the shear rate, for each 
      blend, the increasing droplets, i.e., increasing confinement for a fixed gap 
      spacing, arrange themselves first into two layers, and when the degree of 
      confinement reaches an even higher value, a single layer of droplets is formed. 
      The ratio between the drop diameters and the gap spacing at which this transition 
      occurs is always lower than 0.5. While decreasing the shear rate, the degree of 
      confinement increases due to drop coalescence. Droplets arrange themselves in 
      superstructures like ordered pearl necklaces and, at the lower shear rates, 
      strings. The aspect ratio and the width of the droplet obtained from optical 
      micrographs are compared to predictions of the single droplet Maffettone-Minale 
      model (MM model(1)). It is found that the theory, meant for unconfined shear 
      flow, is not able to predict the drop deformation when the degree of confinement 
      is above a critical value that depends on the blends considered and the shear 
      rate applied. A recently developed extension of the MM model is reported by 
      Minale (M model(2)) where the effect of the confinement is included by using the 
      Shapira-Haber correction.3 Further extending this M model, by incorporating an 
      effective viscosity as originally proposed by Choi and Showalter,4 we arrive at 
      the mM model that accurately describes the experiments of blends in confined 
      flow.
FAU - Tufano, C
AU  - Tufano C
AD  - Eindhoven University of Technology, Department of Mechanical Engineering, 
      Eindhoven, The Netherlands.
FAU - Peters, G W M
AU  - Peters GW
FAU - Meijer, H E H
AU  - Meijer HE
LA  - eng
PT  - Journal Article
DEP - 20080319
PL  - United States
TA  - Langmuir
JT  - Langmuir : the ACS journal of surfaces and colloids
JID - 9882736
EDAT- 2008/03/20 09:00
MHDA- 2008/03/20 09:01
CRDT- 2008/03/20 09:00
PHST- 2008/03/20 09:00 [pubmed]
PHST- 2008/03/20 09:01 [medline]
PHST- 2008/03/20 09:00 [entrez]
AID - 10.1021/la7036636 [doi]
PST - ppublish
SO  - Langmuir. 2008 May 6;24(9):4494-505. doi: 10.1021/la7036636. Epub 2008 Mar 19.