Dilauryl Thiodipropionate: Applications in Modified Bitumen and its Preparation Method

General Description

Dilauryl thiodipropionate is a crucial anti-aging additive in asphalt technology, specifically in modifying bitumen for road construction. Dilauryl thiodipropionate scavenges free radicals, reducing oxidative aging and enhancing pavement longevity. Its stability and protective effects in various temperatures make it valuable for preventing thermal cracking and softening. Through performance grading tests, Dilauryl thiodipropionate maintains asphalt binder specifications for diverse climates, improving durability. The preparation method involves a two-step synthesis under mild conditions, yielding high purity efficiently. Overall, Dilauryl thiodipropionate's application in modified bitumen offers a promising solution to enhance pavement performance, reduce maintenance costs, and increase infrastructure lifespan sustainably.

Figure 1. Dilauryl thiodipropionate

Applications in Modified Bitumen

Role as an Anti-Aging Agent

Dilauryl thiodipropionate is emerging as a significant anti-aging additive in the field of asphalt technology, particularly in the modification of bitumen, a material crucial for road construction. This organic compound is gaining attention for its potential to enhance the longevity and performance of asphalt pavements. The primary application of Dilauryl thiodipropionate in modified bitumen revolves around its role as an anti-aging agent. Dilauryl thiodipropionate functions by scavenging free radicals generated during the oxidation process of bitumen, which occurs both during the production phase and throughout the lifecycle of the pavement under environmental exposure. By neutralizing these radicals, Dilauryl thiodipropionate helps in reducing the rate of oxidative aging of the bitumen, thereby extending the pavement's service life and maintaining its mechanical properties for a longer period. 

Improved Rheological Properties

In practical terms, the addition of Dilauryl thiodipropionate to bitumen results in improved rheological properties. Studies, including those examining the combined effects of Dilauryl thiodipropionate and furfural, indicate that while furfural may degrade under high temperatures, Dilauryl thiodipropionate remains stable, continuing to exert its protective effects against aging. The presence of Dilauryl thiodipropionate in bitumen can lead to a lower susceptibility to temperature fluctuations, reducing the risk of thermal cracking in colder climates and softening in hotter conditions. 

Assessment through Performance Grading Tests

Moreover, the effectiveness of Dilauryl thiodipropionate in modified bitumen has been assessed through performance grading (PG) tests. The inclusion of Dilauryl thiodipropionate helps maintain the PG rating of the asphalt binder, ensuring it meets the required specifications for both high and low-temperature performance. This is crucial for roads exposed to varying climatic conditions, where thermal and oxidative stresses can degrade the pavement prematurely. Overall, Dilauryl thiodipropionate's application in modified bitumen offers a promising avenue for enhancing asphalt pavement durability and performance. By incorporating Dilauryl thiodipropionate road engineers and developers can potentially reduce maintenance costs and increase the lifespan of road infrastructure, aligning with sustainable development goals in civil engineering. ¹

Preparation Method

Synthesis Process

Dilauryl thiodipropionate is synthesized through a specific two-step process that efficiently produces different dialkyl thiodipropionate derivatives, including dilauryl thiodipropionate, under mild and environmentally friendly conditions. The preparation method begins by introducing hydrogen sulfide (H2S) gas into a mixed solution of alkyl acrylate and an aqueous solution of an inorganic base. 

Reaction Steps and Catalysts

This reaction is catalyzed by an inorganic base and occurs at temperatures ranging from 25 to 50°C under a low pressure of 0 to 0.1 MPa. The process continues until the content of the resulting reaction product reaches a concentration of 96% or higher, as confirmed through gas chromatography. Upon reaching the desired concentration, the introduction of H2S is halted, and the reaction mixture is allowed to stand, leading to phase separation. The next step involves distillation of the separated liquid to obtain a distillation product that primarily consists of dialkyl thiodipropionate. This intermediate product then undergoes a transesterification reaction with fatty alcohols (fatty alc.) that have different alkyl chains. This reaction is facilitated by a metal-organic base catalyst, ultimately yielding dilauryl thiodipropionate among other dialkyl thiodipropionate compounds. This method is notable for its reduction in reaction temperatures, simplified equipment requirements, shortened reaction times, and enhancements in both yield and purity of the product, making the synthesis of dilauryl thiodipropionate both efficient and sustainable. ²

Reference

1. Camargo I, Hofko B, Mirwald J. Effect of DLTDP and furfural on asphalt binders: Optimal dosage and PG grading. Construction and Building Materials. 2022; 314: 125489.

2. Yuan Y, Zhang XP, Zhang HJ, Wang XL. Process for preparation of dialkyl thiodipropionate. 2017; Patent Number: CN106977436.

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