This document summarizes a study that evaluated the use of DISPERSIXTM microspheres in highly extended HCR silicone molding and extrusion compounds. The study found that compounds containing DISPERSIXTM microspheres had significantly shorter mixing cycle times of over 40% for molding compounds and over 12% for extrusion compounds. The DISPERSIXTM microspheres also improved dispersion, lowered curing times, increased physical properties, and reduced energy consumption during mixing compared to control compounds without microspheres. Overall, the study showed that DISPERSIXTM microspheres can provide substantial processing improvements while maintaining or improving finished compound properties for silicone applications.

1. Evaluation of DISPERSIX™ in HCR Silicone Compounding
By
Erick Sharp (Speaker) – ACE Products & Consulting LLC, Uniontown, OH
Miles Dearth – The SEFA Group, Lexington, SC
Bill Black – The SEFA Group, Lexington, SC
Presented at the
2016 International Silicone Conference
A Rubber and Plastic News Event
May 17th
& 18th
Akron, OH

2. Abstract
A multi-factor, general factorial designed experiment was performed to investigate the
processing of highly extended HCR silicone molding and extrusion compounds with
aluminosilicate ceramic (ASC) microspheres. The factors selected for experiments are the
presence, particle size, dose level and grade of microspheres. This study measured dependent
variables of a) cycle time, b) MDR properties, c) dispersion, d) physical properties and e) mold
release. Introduced in this study is DISPERSIX™ a new line of inorganic multi-functional process
aids which the data in this study indicate have significant effects on processing efficiency and
the balance of property improvements not previously available to silicone compounders.

3. Introduction of DISPERSIX™ Microspheres
DISPERSIX™ aluminosilicates are recovered from various mining and post-industrial byproduct
streams and converted to micro-spherical ceramics by a patented thermo-oxidative
process. Once returned to their pristine mineral state they are size classified and modified with
inorganic and organic reactants for faster processing and superior properties.
Experiment
Equipment
All trials were mixed on a 5 liter tilt body lab mixer with tangential rotor configuration and
milled on a 6x12 lab mill.
Figure 1 Figure 2

4. Raw Materials
Molding Trial
Figure 3
Extrusion Trial
Figure 4

5. Formulation
Molding Trial
Figure 5
Extrusion Trial
Figure 6

6. Mix Procedure
Molding Formulation
1. Add JFD 2041, JFD 0620, Precipitated Silica and DISPERSIX™ (except for control)
a. Mix to 117°F
2. Add ACE-SD-BIO, ACE-SD-HS2, ACE-SD-MR1, VTEO and ½ Minusil10
a. Mix to 130°F
3. Add remaining Minusil 10
4. Drop at 135°F
5. Ten passes on lab mill
Extrusion Formulation
1. Add JFD 2041, JFD 2071, ACE-SD-HS9, ACE-SD-CaO, ACE-SD-MgO, ACE-SD-MMO
a. Mix 30 seconds
2. Add ½ Minusil 10 and DISPERSIX™ (except for control)
a. Mix to 125°F
3. Add remainder of Minusil 10
a. Mix to 150°F
4. Add DCBP
a. Mix 60 seconds and drop
5. Ten passes on lab mill
Measurable Values
a. Mixing Cycle Time
a. Seconds
b. MDR
a. Parameters
i. Molding formulations: 6’ at 355°F
ii. Extrusion formulations: 6’ at 250°F
b. Values
i. ML
ii. TS2
iii. Tc50
iv. Tc90
v. MH

7. c. Physical Properties
a. Parameters
i. Molding formulations prepped 6’ at 355°F
ii. Extrusion formulations prepped 6’ at 250°F
b. Values
i. Specific Gravity
ii. Tensile (Mpa)
iii. Elongation
iv. 100% Modulus
v. 200% Modulus
vi. Tear die b
vii. Compression Set (method B/ Plied)
d. Other
a. Amp Draw
Results
Cycle Times
Total mixing cycle times were reduced by over 40% with the DISPERSIX™ microspheres in the
molding formulation compound (Figure 7).
Figure 7

8. MDR Data
Compared to the control, compounds containing DISPERSIX™ ASC microspheres exhibited lower
Tc90 cure times by 6 seconds, 11.4 seconds and 9.6 seconds, respectively (Figure 9). This is
thought to be due to the improved dispersion of the peroxide curing agent because DISPERSIX™
spheres act similarly to type II co-agents. It is likely that the amounts of peroxide could be
reduced when using the DISPERSIX™ microspheres.
Mooney-High (MH) as shown in FIG. 10 increases less than two Mooney units when DISPERSIX™
microspheres are present. Relative MH differences between versions of DISPERSIX™
microspheres are thought to be the result of differences in the cure network from different
surface treatments.
FIG. 8

9. 0
0.2
0.4
0.6
0.8
1
1.2
1.4
1.6
1.8
Control Dispersix
4PC
Dispersix
4PC 3
Dispersix
4PC 4
Ts2 0.38 0.38 0.37 0.37
Tc50 0.64 0.65 0.61 0.63
Tc90 1.63 1.53 1.44 1.47
Minutes
MOLDING SCORCH DATAFIG. 9
19
19.5
20
20.5
21
21.5
Control Dispersix 4PC Dispersix 4PC 3 Dispersix 4PC 4
MH 20.02 21.43 21.22 20.62
MH - MOLDINGFIG. 10

10. 2.6
2.7
2.8
2.9
3
3.1
3.2
Control Dispersix
4PC
Dispersix
4PC 3
Dispersix
4PC 4
ML 2.81 3.17 3.07 2.98
ML - MOLDINGFIG. 11

11. EXTRUSION COMPOUNDS
Total mixing cycle times (Figure 13) were reduced by over 12% with the DISPERSIX™
microspheres in the extrusion formulation compound (figure 12).
Figure 12
FIG. 13

12. 0
0.1
0.2
0.3
0.4
0.5
0.6
Ts2 Tc50 Tc90
Control 0.28 0.32 0.56
4PC 0.26 0.31 0.53
Minutes
EXTRUSION SCORCH DATA
6 MIN @ 250° F
FIG. 14
2.32
2.34
2.36
2.38
2.4
2.42
2.44
2.46
2.48
2.5
2.52
ML
Control 2.39
4PC 2.51
ML - EXTRUSIONFIG. 15

13. 8.9
9
9.1
9.2
9.3
9.4
9.5
9.6
9.7
9.8
9.9
MH
Control 9.26
4PC 9.84
MH - EXTRUSIONFIG. 16

14. Physical Properties
Conventional process aids are typically designed to improve productivity but sometimes result in
a sacrifice in physical properties. The research done by SPHERIX Mineral Products has focused
on the development of aluminosilicate ceramified microspheres that improve productivity while
maintaining or improving physical properties at low dosages. Surface modification of these
microspheres optimizes adhesion and crosslinking to the matrix elastomer for enhanced mixing,
dispersion, and flow efficiencies along with reinforcement in the cured state without significant
changes in hardness, scorch and cure rate. Molding formulations containing 5 phr DISPERSIX™
microspheres outperformed the control compound on every physical property measured. The
experimental extrusion formulations exhibited physical properties that were comparable to the
control with a notable improvement in mixing efficiency.
75
76
76
77
77
78
78
Durometer
Control 76
Dispersix 4PC 77
Dispersix 4PC 3 78
Dispersix 4PC 4 77
SHOREA
Molding HardnessFIG. 17

15. 800.0
820.0
840.0
860.0
880.0
900.0
920.0
940.0
960.0
980.0
1000.0
Tensile, psi
Control 875.9
Dispersix 4PC 943.7
Dispersix 4PC 3 990.7
Dispersix 4PC 4 932.2
PSI
Molding TensileFIG. 18
195.0
200.0
205.0
210.0
215.0
220.0
225.0
Control Dispersi
x 4PC
Dispersi
x 4PC 3
Dispersi
x 4PC 4
Elongation % 205.5 211.6 223.7 210.2
%
Molding Elongation %FIG. 19

16. 100% Modulus 200% Modulus
Control 410.5 861.5
Dispersix 4PC 438.5 889.6
Dispersix 4PC 3 435.4 896.3
Dispersix 4PC 4 434.7 891.3
0.0
100.0
200.0
300.0
400.0
500.0
600.0
700.0
800.0
900.0
1000.0
Molding ModulusFIG. 20
85.0
90.0
95.0
100.0
105.0
110.0
115.0
Tear Die B, lbs
Control 93.8
Dispersix 4PC 100.2
Dispersix 4PC 3 110.1
Dispersix 4PC 4 109.6
Molding TearFIG. 21

17. Method B, Plied
Control 33.6%
Dispersix 4PC 27.1%
Dispersix 4PC 3 28.9%
Dispersix 4PC 4 27.0%
Molding CompressionFIG. 22

18. Duromete
r
Elongation
%
100%
Modulus
200%
Modulus
Tear Die
B, lbs
Control 80 241.8 379.8 782.6 177.1
4PC 79 258.0 356.4 746.4 176.1
0
200
400
600
800
1000
Extrusion Physical PropertiesFIG. 23A
Specific Gravity Tensile, (Mpa)
Control 1.524 6.6
4PC 1.489 6.7
0
2
4
6
8
Extrusion Physical PropertiesFIG. 23B

19. Energy Consumption
The physical dispersive action of the microspheres is enhanced by surface chemistry and
improved silica reinforcement while the Amperage draw during compounding decreased by up
to 50% compared with the control.
0
2
4
6
8
10
12
Average AMP Draw
Control 12
Dispersix 4PC 6
Dispersix 4PC 3 7
Dispersix 4PC 4 7
Amp Draw - MoldingFIG. 24

20. Dispersion
By visual observation the compounds with the DISPERSIX™ microspheres had better dispersion
and less powder agglomerations in the milled slab.
Control Batch
DISPERSIX™ Batch
FIG. 25
FIG. 26

21. Conclusions
HCR silicone compounds containing DISPERSIX™ microspheres consistently processed cleaner,
quicker and with better dispersion. The mixer body was cleaner and the batch discharged
better with the DISPERSIX™ microspheres compounds. The DISPERSIX™ microspheres acted in
a ball bearing like effect to break down the raw materials and improve dispersion. This had a
dramatic improvement on the mixing cycle time. The cycle time improvement seems to be
greater on formulations that have a higher level of reinforced filler being added. When molding
slabs for testing the compounds with DISPERSIX™ microspheres had better release from the
mold. This was a consistent observation throughout the entire study.
The development objectives of SPHERIX Mineral Products as demonstrated by the foregoing
experimental mixes in obtaining process improvements without an adverse effect on the
rheology and physical properties have been apparently achieved. The better dispersion
apparently further enhanced the rheology. It is likely that the peroxide level could be slightly
reduced when used in DISPERSIX™ compounds. In molding compounds with a high level of
precipitated and ground silica, significant improvements in physical properties and process
efficiency were demonstrated. Experiments with predispersed fumed silica-containing
extrusion compounds showed comparable physical properties with processing efficiency
benefits in the use of DISPERSIX™ microspheres. Further study in the dispersion of fumed silica
in silicone base compounds is warranted.
The data in the foregoing studies supports the general conclusion that DISPERSIX™
microspheres provide substantial cycle time improvements, enhanced dispersion and reduced
power load, while maintaining equal or better physical properties in the finished compound.
Acknowledgements
A special thanks to John Summers and Polychem Dispersions for their assistance in running
these trials.
A special thanks to HB Chemical for providing raw materials for these trials.