Polymer Modified Asphalt Preparation via Segmented Cross-Linking
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Solution Overview
Problem
Existing methods for preparing polymer modified asphalt (PMA) often result in high 135° C. viscosity and gelling issues due to non-even cross-linking of polymer molecules, leading to storage instability and performance limitations, particularly in high-temperature applications.
Innovation Solution
A process involving the preparation of a polymer-asphalt master batch and an asphalt-cross linking agent blend, followed by blending and curing, allows for controlled polymer network formation without excessive cross-linking, reducing viscosity and enhancing storage stability and performance grades.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If cross linking agent is added to polymer-asphalt blend to form polymer network, then hot-storage stability and rutting resistance are improved, but localized high concentrations cause excessive cross-linking and gelling
Solution Approach 1:
The cross-linking process is divided into two distinct stages: (1) gradual addition of cross-linking agent during initial mixing to start network formation, and (2) delayed addition of remaining cross-linking agent after polymer-asphalt blend preparation to complete cross-linking without gelling. This segmentation prevents localized high concentrations that cause gelling while ensuring adequate cross-linking for hot-storage stability.
Solution Approach 2:
The polymer and asphalt are thoroughly blended first to create a homogeneous polymer-asphalt blend before adding the cross-linking agent. This preliminary action ensures uniform distribution of polymer molecules, preventing localized high concentrations when cross-linking agent is added, thereby avoiding gelling while enabling effective cross-linking.
2Strength
If polymer molecules are cross-linked to form network, then rutting resistance and fatigue cracking resistance are improved, but excessive cross-linking increases 135° C. viscosity
Solution Approach 1:
The cross-linking process is segmented into two stages with controlled timing and dosage. The first stage uses a small initial amount of cross-linking agent during mixing to start network formation without excessive viscosity increase. The second stage adds the remaining cross-linking agent after blending to complete cross-linking for rutting resistance while avoiding excessive 135° C. viscosity.
Solution Approach 2:
The patent uses a controlled, partial cross-linking approach where the cross-linking agent is added in two stages rather than all at once. This partial action at different times ensures sufficient cross-linking for rutting resistance while preventing excessive cross-linking that would cause high 135° C. viscosity and gelling.
3Reliability
If cross linking agent is added gradually over time, then gelling is prevented, but production time and process complexity increase
Solution Approach 1:
The cross-linking process is segmented into two practical stages: (1) addition during initial mixing for network initiation, and (2) delayed addition after blend preparation for completion. This segmentation achieves storage stability without requiring extremely gradual addition over many hours, thus limiting production time increase while preventing gelling.
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 PMAs with lower 135° C. viscosity, improved high-temperature performance, and enhanced low-temperature grades, while eliminating gelling and lump formation, thus ensuring better rutting and cracking resistance and cost-effectiveness.
Implementation Method 1
it is highly desirable to have the polymer molecules cross link to each other, forming a polymer network within the asphalt to provide hot-storage stability, improved rutting resistance and fatigue cracking resistance
Implementation Method 2
Localized high concentrations of sulfur may cause excessive link-up of the polymer molecules and the formation of big lumps
Implementation Method 3
Following curing, the PMAs are typically stored at high temperatures (about 150° C.) before use
Data Source
AI summary
A process of preparing a polymer modified asphalt (PMA) comprising mixing a predetermined amount of a polymer-asphalt master batch with a predetermined amount of an asphalt-cross linking agent blend. The polymer-asphalt master batch comprises at least one polymer and a first asphalt. The asphalt-cross linking agent blend comprises a second asphalt and at least one cross linking agent. A predetermined amount of the polymer-asphalt master batch is blended with a predetermined amount of the asphalt-cross linking agent blend to form a PMA blend. Mixing of the PMA blend is performed without substantial delay following blending of the polymer-asphalt master batch with the asphalt-cross linking agent blend.