Devulcanizing Vulcanized Rubber via Controlled Shear
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Solution Overview
Problem
Current recycling methods for vulcanized rubber are inefficient and economically unviable due to the irreversible nature of vulcanization, which prevents reshaping and limits recycling to crushing or shredding, resulting in a product that cannot be chemically linked to a polymer matrix, and existing devulcanization processes are energy-intensive, difficult to implement, and produce unstable, degraded materials.
Innovation Solution
A process involving crushing vulcanized rubber into chips, kneading to homogenize temperature and shape, and applying non-degrading mechanical treatment to break vulcanization bonds while preserving residual double bonds, allowing for the creation of a polymer composite that can be chemically bonded with other polymeric materials, achieving partial or total devulcanization without degradation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If vulcanized rubber is subjected to aggressive chemical and thermal treatment to dismantle the three-dimensional network, then devulcanization is achieved, but the product exhibits degraded physical and mechanical properties that limit its use
Solution Approach 1:
The invention changes the parameters of mechanical treatment by applying specific shear rates (between 100 and 10,000 s⁻¹) and controlling temperature ranges (50-350°C) to achieve devulcanization. By precisely controlling these parameters, the process breaks vulcanization bonds while preserving the polymer chain integrity and residual double bonds, thus maintaining mechanical properties
Solution Approach 2:
The invention replaces aggressive chemical and thermal treatment with a controlled thermomechanical process. Instead of using harsh chemicals or excessive heat that degrade the material, the process uses mechanical shearing forces generated during kneading and extrusion to break the crosslinks, substituting a milder mechanical approach for harsh chemical/thermal methods
2Reliability
If high shear rate and temperature are applied to achieve partial devulcanization, then vulcanization bonds are broken, but the process requires high energy input and produces chemically degraded unstable product
Solution Approach 1:
The invention employs continuous kneading and extrusion processes that maintain optimal shear rates and temperatures throughout the treatment. This continuous action ensures efficient energy utilization by constantly renewing the mechanical stress on the rubber material, achieving thorough devulcanization without requiring excessive energy input or prolonged processing times
Solution Approach 2:
The process optimizes energy efficiency by carefully controlling the relationship between shear rate and temperature. By maintaining shear rates between 100-10,000 s⁻¹ and temperatures between 50-350°C, the process achieves devulcanization at energy levels that are significantly lower than conventional methods, while preventing chemical degradation through precise parameter management
3Ease of manufacture
If vulcanized rubber is crushed or shredded for recycling, then processing is simple, but the product cannot be chemically linked to a polymer matrix and is limited to use as filler
Solution Approach 1:
The invention extracts the vulcanization crosslinks from the rubber material through controlled mechanical shearing, while leaving the polymer chains and functional groups intact. This selective removal of crosslinks transforms the material from a rigid network structure to a processable state, enabling subsequent chemical bonding applications that simple crushing cannot achieve
Solution Approach 2:
By controlling the shear rate and temperature parameters during mechanical treatment, the invention transforms vulcanized rubber into a devulcanized state that retains chemical reactivity. This parameter-controlled transformation maintains polymer chain integrity and preserves residual double bonds, enabling the material to be chemically linked to polymer matrices and used in diverse applications beyond filler use
4Reliability
If thermomechanical treatment is applied to devulcanize rubber, then partial degradation occurs, but the product shows instability over time due to free radical recombination
Solution Approach 1:
The invention introduces antioxidants and stabilizers as intermediaries during the thermomechanical devulcanization process. These additives act as free radical scavengers that prevent unwanted recombination reactions, thereby stabilizing the devulcanized rubber composition over time while allowing effective crosslink breakdown
Solution Approach 2:
The process optimizes the relationship between shear rate and temperature to minimize free radical formation while maximizing vulcanization bond breakdown. By maintaining shear rates between 100-10,000 s⁻¹ and temperatures between 50-350°C, the process achieves devulcanization with reduced chemical degradation and improved long-term stability
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 a flexible, non-granular polymer composite that can be used in various rubber processing technologies, offering improved mechanical and physicochemical properties, enabling effective recycling and reuse in rubber formulations without altering the final product's characteristics.
Implementation Method 1
a non-degrading mechanical treatment is carried out on the kneaded rubber obtained at the end of step c) to obtain a polymer composite
Implementation Method 2
the ground rubber obtained at the end of step b) is kneaded so as to homogenize it in shape and temperature
Implementation Method 3
It is important to note that the vulcanized elastomer still has, within it, numerous residual double bonds, which are all sites that can be used later for new chemical reactions
Data Source
Figure 1~2
AI summary
The invention concerns a method of devulcanising vulcanised rubber which comprises the following steps: a) providing at least one vulcanised rubber composition; b) grinding the vulcanised rubber into chips or pellets; c) mixing the ground rubber obtained from step b) in such a way as to homogenise the form and temperature of same. d) carrying out a non-degrading mechanical treatment on the mixed rubber at the end of step c) to obtain a polymeric composite. The invention also concerns a thermoplastic material and an elastomeric mixture which comprise, in the formulation of same, at least one polymeric composite obtained by this method of devulcanisation.