Conductive Natural Rubber TPV for EMI Shielding

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Solution Overview

Problem

There is a need for an improved manufacturing process for Hevea Brasiliensis natural rubber-based thermoplastic vulcanisates that exhibit high electrical conductivities, good tensile properties, and high electromagnetic interference (EMI) shielding effectiveness, while also being highly processable and recyclable without significant loss of properties.

Innovation Solution

A method and device for manufacturing electrically conductive peroxide-vulcanised thermoplastic vulcanisates using a composition of 40.0% to 60.0% Hevea Brasiliensis natural rubber, 40.0% to 60.0% polypropylene, 1.0% to 50.0% sulfonic acid doped polyaniline, and peroxide vulcanisation agents, processed at high temperatures using an internal mixing device with controlled conditions to achieve conductivities of up to 2.1 S/cm and EMI shielding effectiveness of at least 30 dB.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If conventional TPV materials are used, then processability is good, but electrical conductivity is insufficient (volume electrical resistivity ≥10^8 ohm-cm)

Engineering Contradiction:

Improveelectrical conductivityVSAvoidprocessability

Core Design Contradiction:

ReliabilityVSEase of manufacture

Solution Approach 1:

The patent creates a composite TPV material by incorporating sulfonic acid doped polyaniline (a conductive polymer) into the thermoplastic vulcanisate matrix consisting of natural rubber and polypropylene. This composite structure enables the material to achieve high electrical conductivity (up to 2.1 S/cm) while maintaining the processability characteristics of conventional TPVs through injection molding and extrusion techniques.

Inventive Principle:

Principle #40Composite materials

2Reliability

If natural rubber based TPV is prepared with conductive additives, then electrical conductivity improves, but manufacturing complexity increases

Engineering Contradiction:

Improveelectrical conductivityVSAvoidmanufacturing process complexity

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The conductive polymer (sulfonic acid doped polyaniline) is pre-synthesized and doped before being incorporated into the TPV matrix. This preliminary preparation of the conductive additive simplifies the overall manufacturing process by eliminating the need for in-situ conductive polymer synthesis during TPV production, thus reducing manufacturing complexity while achieving high electrical conductivity.

Inventive Principle:

Principle #10Preliminary action

3Adaptability or versatility

If TPV is reprocessed multiple times, then recyclability is achieved, but electrical conductivity and tensile properties deteriorate

Engineering Contradiction:

ImproverecyclabilityVSAvoidelectrical conductivity and tensile properties

Core Design Contradiction:

Adaptability or versatilityVSReliability

Solution Approach 1:

The patent enables the TPV material to be reprocessed and recycled multiple times (demonstrated up to 4 cycles) while recovering and maintaining its functional properties. The peroxide-vulcanised crosslinked structure and well-dispersed conductive polymer network allow the material to retain its electrical conductivity and tensile properties through multiple reprocessing cycles, making it suitable for sustainable manufacturing applications.

Inventive Principle:

Principle #34Discarding and recovering

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 process produces thermoplastic vulcanisates with high electrical conductivities and EMI shielding effectiveness, maintaining these properties up to 4 cycles of reprocessing with minimal loss, making them suitable for EMI shielding products like seals and gaskets.

Implementation Method 1

electrically conductive peroxide-vulcanised thermoplastic vulcanisates

Methodology Applied

Scientific EffectPeroxide vulcanisation: Chemical Bonding

Implementation Method 2

sulfonic acid doped polyaniline with protonation level at at least 40%-100%

Methodology Applied

Scientific EffectElectrical conduction: Conduction (electrical)

Implementation Method 3

high temperature-mechanical mixing

Methodology Applied

Scientific EffectMechanical mixing: Mechanical Force

Data Source

PatentUS10584242B2Natural rubber based electrically conductive thermoplastic vulcanisates and the device for manufacturing the same

Publication Date: 2020.03.10 LEMBAGA GETAH MALAYSIA

AI summary

The various embodiments of the present invention disclose an peroxide-vulcanised TPVs based on Hevea Brasiliensis natural rubber, polypropylene and solid sulfonic acid doped polyaniline [PAni.DBSA] with useful electrical conductivities (up to about 2.1±0.2 S/cm] can be produced by using an internal mixer. The peroxide-vulcanised TPVs exhibit useful physical properties and also possess a reasonable good electromagnetic interferences shielding effectiveness. These peroxide-vulcanised TPVs could be recycled up to 4 times without significant loss of their EMI SE, electrical and physical properties. As a result, they have good potential to be used for manufacturing any EMI shielding products, such as EMI shielding seals and gaskets.