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thermal degradation of pbat

2023-11-27

thermal degradation of pbat (Polybutyrate Adipate Terephthalate)

Introduction: PBAT (Polybutyrate Adipate Terephthalate) is a biodegradable thermoplastic polymer that is widely used in various industries due to its advantageous properties and environmentally friendly nature. However, like any polymer, PBAT is susceptible to thermal degradation when exposed to high temperatures for an extended period. This article aims to explore the thermal degradation process of PBAT and its impact on the polymer's properties.

Thermal degradation process: PBAT starts to degrade when the temperature exceeds its glass transition temperature (Tg), which is typically around 45-65 degrees Celsius. At this temperature range, the long chains of PBAT start to move more freely, leading to an increase in the molecular mobility. Higher temperatures result in increased chain movement, eventually leading to chain scission and fragmentation.

Effect on molecular weight: thermal degradation of pbat primarily affects the molecular weight of the polymer. When subjected to high temperatures, the long polymer chains start to break into smaller segments, causing a reduction in the average molecular weight. This decrease in molecular weight directly impacts the mechanical properties of PBAT, such as tensile strength and impact resistance.

In addition to chain scission, thermal degradation can also lead to cross-linking in PBAT. Cross-linking occurs when the broken chains react with each other, forming strong chemical bonds. This process results in the formation of a three-dimensional network, making the polymer more rigid and less flexible. While cross-linking can prevent further chain scission, it also reduces the polymer's overall processability and flexibility.

Effect on thermal properties: The thermal properties of PBAT are significantly affected by thermal degradation. The degradation products generated during the process, such as volatile organic compounds (VOCs), can lower the polymer's thermal stability. This decrease in thermal stability reduces the maximum processing temperature of PBAT, making it more challenging to mold and process.

Furthermore, thermal degradation of pbat can increase the polymer's crystallinity. The broken chains and larger molecular fragments tend to rearrange and form ordered crystalline structures. This increase in crystallinity alters the polymer's melting and crystallization temperatures, leading to changes in its thermal behavior.

Effect on mechanical properties: As mentioned earlier, the reduction in molecular weight due to thermal degradation affects the mechanical properties of PBAT. In particular, the tensile strength, elongation at break, and impact resistance are significantly affected. The breaking of polymer chains weakens the intermolecular forces, resulting in a decrease in the polymer's overall strength and elongation ability. This degradation-induced decrease in mechanical properties limits the potential applications and reliability of PBAT in various industries.

Conclusion: Thermal degradation is an essential aspect to consider when using PBAT in applications where high-temperature exposure is expected. The degradation process primarily affects the molecular weight, thermal properties, and mechanical properties of the polymer. Understanding how PBAT degrades under thermal stress allows for better optimization of processing conditions and formulation of suitable additives to inhibit degradation. By minimizing thermal degradation, PBAT can retain its desirable properties, making it a sustainable and viable alternative to conventional polymers in various industries.