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.

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

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

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

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

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

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

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

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

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

Energy of Mixing

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

Synthesis of Reinforced Polymers

Characterization (Via DSC)

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

Morphology (cont’d) Morphology of syndio-PBd strongly depends on the nature of host rubber matrix Syndio-PBd was micro-fibrous (average length= 0.0002 mm) in isoprene or styrene containing rubber matrix (e.g. IR, SBR, …) which provided ISOTROPIC reinforcement

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

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

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

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

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.

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.