Supplementary Information
Determination of the failure stresses for fluid-filled microcapsules that rupture near the
elastic regime.
Ruben Mercadé-Prieto,a Rachael Allen,a David York,b Jon A. Preece,c Ted E. Goodwin,d
Zhibing Zhanga,*
a
School of Chemical Engineering, University of Birmingham, Edgbaston, Birmingham B15
2TT, UK.
b
Procter and Gamble Technical Centre, Newcastle upon Tyne NE27 0QW, UK.
c
School of Chemistry, University of Birmingham, Edgbaston, Birmingham B15 2TT, UK.
d
ENCAPSYS® , Appleton, P. O. Box 359, Appleton, WI 54912-0359, USA.
*: Tel: (+44) (0) 121 414 5334, Fax: (+44) (0) 121 414 5324, E-mail: Z.Zhang@bham.ac.uk.
(a)
(b)
Figure S1. Zoomed-in section of the bent region as shown in Fig. 2 of a microcapsule (h/r =
4.8%, E = 100 MPa) at  = 0.18, indicating the maximum principal stress (a) and the von
Mises stress (b). The thickness planes of the four failure criteria discussed in the text are also
shown in detail.
(a)
(b)
(c)
(d)
Figure S2. Stress diagram using the local coordinates shown in the insets, for a microcapsule
with h/r = 4.8% and E = 100 MPa compressed to a fractional deformation  = 0.18. Note that
the most stressed area for S11 in (a) is different from that for the other stresses.
(a)
(b)
Figure S3. Position of Av,MIS and Min,MIS in a microcapsule subjected to different
compressive fractional deformations. The positions relate to the uncompressed microcapsule
as shown in the inset of Fig. 5(b).
Figure S4. Comparison of the three different normalized failure stress criteria developed in
Section 3. Note that all the three criteria produce similar failure stress values.
Table S1. Comparison between the elastic modulus and strengths of different TEOS based
materials found in the literature and the results obtained in the present study with TEOSMTMS microcapsules.
Material
E (MPa)
Strength (MPa)
Reference
TEOS-poly(tetramethylene oxide)
10-500
10-40
[1]
TEOS-poly(methylsiloxane)
10
3
[2]
TEOS-hydroxypropyl cellulose
NA
5-18
[3]
TEOS-polyester
NA
5-50
[4]
300-500
30-60
[5]
TEOS-starch-polyvinyl alcohol
1200-1600
25-50
[6]
TEOS-poly(urethane acrylate)
NA
2-9
[7]
~450
11-18 ± 10
Present study
TEOS-polyurethane
TEOS-MTMS
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