Branched Isoolefin Elastomer Melt Processability
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Solution Overview
Problem
Saturated isobutylene-based polymers and their blends face challenges with low green strength, narrow molecular weight distributions, slow relaxation times, and poor processability, which limits their application in areas requiring improved compatibility, co-curability, and filler dispersibility while maintaining aging resistance and air barrier properties.
Innovation Solution
Development of branched polyisobutylene elastomers with a saturated polymer backbone, incorporating isoolefin, styrenic, and multiolefin monomers, specifically isobutylene, p-methylstyrene, and divinylbenzene, to enhance green strength and relaxation characteristics, along with the use of fluorinated hydrocarbons to increase polydispersity and facilitate melt processing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If linear isobutylene-p-methylstyrene copolymers are used, then aging resistance and air barrier properties are maintained, but green strength is low and processability is poor
Solution Approach 1:
The patent changes the molecular weight distribution parameter by incorporating a chain transfer agent during polymerization, achieving a broader MWD (polydispersity index of 2.0-5.0) while maintaining the saturated backbone structure. This parameter change improves green strength and processability without sacrificing aging resistance
Solution Approach 2:
The patent creates a composite polymer system by copolymerizing isobutylene with p-methylstyrene and a chain transfer agent, producing a copolymer that combines the aging resistance of saturated polymers with improved processability characteristics. The composite structure achieves both durability and manufacturability
2Adaptability or versatility
If narrow molecular weight distribution is maintained, then polymer compatibility is limited, but manufacturing precision is preserved
Solution Approach 1:
The patent deliberately changes the molecular weight distribution parameter from narrow to broad (polydispersity index of 2.0-5.0) by incorporating a chain transfer agent. This broader distribution enhances polymer compatibility and blend homogeneity while maintaining controlled manufacturing through defined copolymer composition ranges
3Reliability
If saturated hydrocarbon backbone is used, then aging resistance is improved, but filler dispersibility and co-curability are poor
Solution Approach 1:
The patent applies local quality by introducing p-methylstyrene units at specific locations along the isobutylene chain. These styrenic units provide reactive functionality and improved filler interaction at localized sites, while the majority saturated isobutylene backbone maintains aging resistance. This localized functionalization enables both durability and compatibility
Solution Approach 2:
The patent creates a composite polymer structure combining saturated isobutylene segments with unsaturated p-methylstyrene segments. This composite architecture provides both the aging resistance of saturated polymers and the filler dispersibility and co-curability of unsaturated polymers
4Adaptability or versatility
If isobutylene-isoprene copolymers are used, then filler dispersibility is improved, but molecular weight distribution becomes too broad and green strength decreases
Solution Approach 1:
The patent changes the comonomer type from isoprene to p-methylstyrene, maintaining the unsaturated functionality needed for filler dispersibility while controlling the molecular weight distribution through chain transfer agent incorporation. This achieves optimal balance between green strength and filler interaction
Solution Approach 2:
The patent uses local quality by incorporating p-methylstyrene units that provide reactive sites for filler interaction, while the saturated isobutylene backbone maintains structural integrity and green strength. This localized functionality achieves filler dispersibility without compromising strength
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The branched elastomers exhibit improved green strength, relaxation characteristics, and processability, enabling better compatibility and filler dispersion, thus expanding their application in air barriers and tire innerliners with maintained aging resistance.
Implementation Method 1
Compared to chlorinated hydrocarbon solvents used in the polymerization of isobutylene-isoprene copolymers, the fluorinated hydrocarbon solvents generally produce butyl polymers with a narrower molecular weight distribution or polydispersity (Mw/Mn)
Data Source
AI summary
A branched isobutylene-styrenic elastomer with a broad molecular weight distribution is disclosed comprising an interpolymer of an isoolefin monomer as isobutylene, a styrenic monomer such as p-methylstyrene, and a multiolefin such as divinylbenzene. The elastomer has improved green strength, relaxation characteristics, and processability in melt processing, while retaining excellent aging characteristics and barrier properties, and can be used in a blend with a linear isobutylene-p-alkylstyrene elastomer to improve processability of the linear elastomer. Also disclosed are a method for processing the linear elastomer with an effective amount of the branched elastomer to improve processability, and nanocomposites, curable compositions, cured compositions and useful articles formed from the branched elastomer and the linear-branched elastomer blends.