Post on 20-Sep-2020
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Solvent Resistance and Mechanical Properties in Thermoplastic Elastomer Blends Prepared by Dynamic Vulcanization
J.D. (Jack) Van DykeTrinity Western University, Langley, B.C., Canada
Marek GnatowskiPolymer Engineering Co. Ltd, Burnaby, B.C., Canada
Andrew BurczykDefence R&D Canada-Suffield, Canada
Mixing Methods
High shear melt mixing
Without curing agents non-vulcanized blends Continuous phase dependent on proportions in the
blend
With curing agents dynamic vulcanization Non-vulcanized component becomes continuous
phase, almost independent of proportion in blend
Non-Vulcanization vs. Dynamic Vulcanization
Objective of Present Work
Dynamic Vulcanization on a Variety of Thermoplastic / Rubber Combinations
Thermoplastics (PA, PP, and PBT)
Rubber (CIIR, NBR)
Measure
Mechanical properties
Exposure to solvents (hexane and CHCl3)
% insolubility, swelling index
DSC and SEM
Effect of % Thermoplastic on Properties
PP-CIIR Blends
0.0
5.0
10.0
15.0
20.0
25.0
30.0
35.0
18 20 25 30 35 40 50 60 100
% Polypropylene
Ten
sile S
tren
gth
(M
Pa)
Tensile Strength
(MPa)PP-CIIR Blends
0
10
20
30
40
50
60
70
80
18 20 25 30 35 40 50 100
% Polypropylene
Hard
ness (
Sh
ore D
)
Hardness (Shore D)
60-90 50-90
Tensile Strength Comparison in Blends
PA-
CIIRPP-
CIIRPA-
NBRPP-
NBRPBT-
NBR
0
15
20
25
30
35
4050
0.0
2.0
4.0
6.0
8.0
10.0
12.0
14.0
16.0
18.0
20.0
Tensile Strength
Blend Type
% Plastic
DSC Results – Thermoplastic Phase
Tm (°C) ΔHf (J/gplastic)
PA 178.7 60.6
PA/CIIR 175.6 58.1
PA/NBR 176.5 58.5
PP 163.3 80.9
PP/CIIR 161.6 83.1
PP/NBR 161.5 80.6
PBT 223.0 38.1
PBT/NBR 222.6 46.0
Phase separation
Dynamic vulcanization effects
rubber phase (curing, particle formation)
thermoplastic phase (MW reduction, graft formation, crystallization effects)
SEM OF PA/NBR BLEND
PA-NBR Blend PP-NBR Blend
0
1
2
3
4
5
6
0 8 16 24 32 40 48 56 64 72 80 88 96
Time (hrs)
Sw
elli
ng Index
100 NBR
40 PA /60 NBR
Solvent Uptake – Kinetic Studies
Rate of solvent uptake determined on rubber and blend samples
Blends achieve equilibrium relatively quickly
Example of 100 NBR and 40 PA/60 NBR
Swelling Index: PA – CIIR Blend at Different Compositions
S.I. Values consistently below theoretical line (physical mixture)
Continuous thermoplastic phase prevents solvent expansion of cured rubber phase
PA-CIIR Blends
0
1
2
3
4
5
6
7
0 10 20 30 40 50 60 70 80 90 100
% Polyamide
Sw
ell
ing
In
dex
Swelling Index
Swelling Index Values for Other Blends
PP-CIIR Blends
0
1
2
3
4
5
6
7
0 10 20 30 40 50 60 70 80 90 100
% Polypropylene
Sw
ellin
g In
dex
Swelling Index PA-NBR Blends
0
1
2
3
4
5
6
0 10 20 30 40 50 60 70 80 90 100
% Polyamide
Sw
ellin
g In
dex
Swelling Index
Swelling Index Values for Other Blends
PP-NBR Blends
0
5
10
15
20
25
30
0 10 20 30 40 50 60 70 80 90 100
% Polypropylene
Sw
ellin
g In
de
x
Swelling Index PBT-NBR Blends
0
5
10
15
20
25
30
0 10 20 30 40 50 60 70 80 90 100% PBT
Sw
ellin
g In
dex
Swelling Index
Relationship Between Swelling Index and % Elongation
Minimum elongation reached at similar composition as change in S.I. Curve
Phase inversion
Similar results for all blends studied.
PBT-NBR Blends
0
5
10
15
20
25
30
0 10 20 30 40 50 60 70 80 90 100
% PBT
Sw
ellin
g In
dex
0
100
200
300
400
500
600
Elo
ng
ati
on
(%
)
Swelling IndexElongation (%)
Conclusions
1. Dynamic vulcanization – variety of rubber plastic blends, many with elastomeric properties. Elastomeric properties seen between 20-40%
thermoplastic
2. Both rubber and plastic phases affected during the dynamic vulcanization process.
3. Solvent exposure – rapid swelling upon exposure to solvent (tested on hexane and CHCl3). Similar performance expected with other solvents.
Conclusions (continued)
4. S.I. values of blends are significantly less than expected “theoretical” values. “caging effect” at higher thermoplastic
compositions.
5. Minimum elongation values reached at phase inversion.
6. Increased compatibility in blends reduced particle size (discrete phase)
frequently produces less caging effect on the rubber phase
Acknowledgements
Defence R&D Canada – Suffield
Laboratory staff at PEC
Dave Lesewick, Christine Mah, Beverley Start
Laboratory staff at TWU
Leanne Edwards, Simon Moore, Kim Klassen
DRDC – Esquimalt (SEM results)
Bruce Kaye
Website: www.polymer-engineering-co.com/