Polyurethane-Modified Bitumen from Waste PET
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Solution Overview
Problem
Bitumen used in asphalt pavements fails to meet high-performance criteria in extreme climates, leading to heat- and fatigue-induced cracks and rutting, and the use of styrene-butadiene-styrene (SBS) polymer additives is costly and not environmentally friendly.
Innovation Solution
A modified bituminous mixture is developed using polyurethane synthesized through a polymerization reaction from waste polyethylene terephthalate (PET) and/or combined with SBS, reducing the amount of SBS needed and incorporating recycled PET, which enhances the performance and durability of bitumen while lowering production costs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If bitumen is modified with SBS polymer additive to improve performance in extreme climates, then the durability and resistance to heat- and fatigue-induced cracks are improved, but the production cost increases
Solution Approach 1:
The patent changes the chemical composition parameters of the bitumen modifier by replacing SBS polymer with polyurethane synthesized from waste PET and diisocyanate. This parameter change maintains the performance improvement (elastic recovery, crack resistance) while reducing production cost through the use of cheaper, recycled materials.
Solution Approach 2:
The patent employs waste PET bottles as the starting material for polyurethane synthesis. By utilizing discarded, low-value plastic waste instead of expensive virgin SBS polymer, the invention achieves cost reduction while maintaining functional performance in modified bitumen.
2Ease of manufacture
If waste PET is directly incorporated into bitumen to reduce costs, then the production cost decreases, but the performance improvement is limited and insufficient for high-performance applications
Solution Approach 1:
The patent replaces the simple mechanical mixing of waste PET with bitumen with a chemical reaction system. By introducing diisocyanate to react with PET and form polyurethane in situ, the invention transforms a physical blending approach into a chemical synthesis approach, achieving superior performance.
Solution Approach 2:
The patent creates a composite material system where waste PET, diisocyanate, and bitumen combine through chemical reaction to form polyurethane-modified bitumen. This composite approach integrates the advantages of recycled material (cost reduction) with chemical bonding (performance enhancement).
3Reliability
If polyurethane is synthesized from waste PET through chemical depolymerisation to BHET and then polymerization, then the performance and durability are significantly improved, but the manufacturing process complexity increases
Solution Approach 1:
The patent merges the depolymerisation and polymerization steps into an integrated two-stage process. By combining waste PET collection, BHET synthesis, and polyurethane formation in a coordinated sequence, the invention manages process complexity while achieving high performance outcomes.
Solution Approach 2:
The patent performs preliminary chemical treatment of waste PET to convert it into BHET monomers before the final polyurethane synthesis. This preliminary action prepares the recycled material in a reactive form suitable for polymerization, ensuring both performance and process manageability.
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 modified bituminous mixture improves the quality and performance of asphalt pavements, reducing maintenance needs and environmental impact by using recycled materials, achieving similar performance to high-SBS bitumen at lower costs and with enhanced durability.
Implementation Method 1
adding ethylene glycol to a reactor containing waste polyethylene terephthalate (PET) bottles; heating the contents of the reactor at 195-200° C. for 3 hours under atmospheric pressure to undergo a glycolysis reaction
Implementation Method 2
adding BHET monomers, as a diol monomer, obtained through recycling reactions from waste PET products; following the addition of BHET monomers into the reactor, adding butanediol as a chain extender so that the polymerization reaction is initiated
Data Source
AI summary
A method for preparing a modified bituminous mixture is developed according to the present invention, this method comprising the steps of fluidizing bitumen as the main component of the mixture at 130-140°C; transferring the fluidized bitumen into a mechanical mixer running at 120 rpm stirring speed; producing a polyurethane-bitumen mixture by adding polyurethane, as an additive in hot form, obtained through a polymerization reaction of BHET monomers obtained through a recycling reaction of waste PET products, as a diol monomer with diisocyanate monomer and a chain extender into bitumen in said mixer while stirring continues; stirring further this mixture for a predetermined time at a predetermined stirring speed to obtain a homogeneous polyurethane-bitumen mixture; following the completion of the stirring process, obtaining a homogeneous polyurethane-added modified bituminous mixture.