1. In-Situ Polymerization of Crystalline Polymer in Elastomer Matrix
A.F. Halasa
University of Akron
College of Polymer Science
Bill Hsu The Goodyear Tire Co.

2. Agenda Background / Objective Synthesis of Crystalline Polymer
Morphology by TEM
Properties
Summary

3. Syndiotactic-1, 2-Polybutadiene
(SPBD)
A lightweight reinforcing filler
Co-curable with rubber
Increase modulus, stiffness, green strength,…
Reinforcement depends
on crystallinity
Hard to disperse high
melting SPBD

4. Disadvantages of Fluxing and Milling Syndio-PBd in Gum Rubber Matrix
High flux temperature and high shear mixing are required for adequate dispersion
Breakdown of rubber matrix occurs
Fluxing reduces crystallinity of syndio-PBd
Low melting syndio-PBd can be well mixed with rubber but reinforcement was not revealed

5. Use of Syndio-1, 2-PBd in Rubber Application
UBEPOL VCR
Manufactured by UBE Industries
A block (blend ?) of Syndio-1, 2-PBd (Tm=204°C) with low Mooney cis-1,4- PBd (ML-4 = 25)
Use in conjunction with other rubber to improve processability, flex-crack resistance and green strength

6. UBE VCR Process
One pot, two steps polymerization---

7. UBEPOL VCR Block copolymers of cis-1,4/1,2-vinyl Polybudienes
* Data supplied by UBE Industries
Sample * Mw
(x 10-4) Mn
Mw/Mn
% syndio-PBd
ML-4
VCR 309
45.9
17.1
2.7 9 39
VCR 412
45.1
18.4
2.5 12 45
VCR 617
46.2
17.6
2.6 17 63
VCR 512
44.2
15.5
2.9 43

8. UBEPOL VCR
Processing and cure properties largely determined by low Mooney PBd
Reinforcement of rubber compounds not revealed

9. Objective
To prepare well dispersed, high melting syndiotactic-1, 2-polybutadiene in rubber to achieve maximum reinforcement

10. Concept and Theory
The concept is that the new monomer growth is controlled by the host polymer viscosity
The growth of the new monomer molecular weight control its solubility and miscibility in the host polymer
The new polymer high molecular weight make it immiscible and crystalline in the host polymer

11. Energy of Mixing

12. Synthesis of In-Situ Syndio-PBd in Rubber Matrix
The new process involves the addition of a second monomer to a preformed polymer cement and polymerizing the homogenously distributed monomer with added catalyst in the matrix of the preformed elastomer

13. Synthesis of Reinforced Polymers

14. Characterization (Via DSC)

15. Morphology
The morphology and dispersion of crystalline polymer were studied using Transmission Electron Microscopy (TEM)
Crystalline polymer was well dispersed in the rubber matrix

16. Morphology (cont’d)
Morphology of syndio-PBd strongly depends on the nature of host rubber matrix
Syndio-PBd was micro-fibrous (average length= mm) in isoprene or styrene containing rubber matrix (e.g. IR, SBR, …) which provided ISOTROPIC reinforcement

25. Compound Evaluation
A blend of 50:50 SPBD/IR and NR was evaluated against three all NR containing compounds
Significant improvements in modulus, bending stiffness and cut-grown resistance were observed
Tensile strength and elongation at break were reduced

26. Compound Properties Replace 50% of NR with SPBD/PI (20% SPBD)* A 457
* All NR containing compounds have base value of 100
Compound
Modulus (50%)
Tensile
Elongation
Bending Stiffness (5%)
Cut-growth Resistance
Hardness A
457 77 61
1000
155 B
213 83 67
252
567 C
190 85 82
200

27. Micro-fibrous Syndio-PBd in PBd Matrix
Micro-fibrous Syndio-PBd in PBd matrix can be formed using polyisoprene as the dispersion agent:

28. Micro-fibrous Syndio-PBd in PBd Matrix (cont’d)
Micro-fibrous Syndio-PBd is well dispersed in cis-1,4-PBd matrix using this process
Morphology is significantly different than that of UBEPOL VCR

30. Summary
Crystalline polymers can be prepared in rubber cements via the In-Situ process.
The In-Situ process provides a fine dispersion of crystalline polymer within the rubbery matrix which might not be achieved through Banbury mixing.
The crystalline polymer was already dispersed in the host rubber matrix. Previous mixing problems were eliminated.
Excellent rubber reinforcement was achieved using the In-Situ SPBD/IR composite.

31. Summary (cont’d)
Syndio-PBd was micro-fibrous in the rubber matrix containing isoprene or styrene.
The observed “isotropic” reinforcement was attributed to micro-fibrous SPBD produced in the In-Situ process.
Micro-fibrous SPBD can be formed in PBd matrix using Polyisoprene as the dispersing agent.