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Transitioning PVC plastisol technology toward bio-based systems: Processing principles, challenges and opportunities of poly(3-hydroxybutyrate)
Summary
Most vinyl-like coatings (think faux leather, printed textiles) are made with PVC plastic softened by phthalate chemicals, additives linked to hormone disruption and other health concerns. This review paper takes stock of efforts to replace that PVC with PHB, a biodegradable plastic made by bacteria, explaining why it's technically tricky to work with but highlighting the roadmap researchers need to make it a real substitute. It's not a new product yet, but it's a snapshot of progress toward coatings that could someday be safer for both people and the environment.
Plastisols are among the most versatile polymer dispersion systems used in coatings, screen printing, artificial leather, technical textiles, and related applications owing to their low-temperature processability and excellent film-forming characteristics. Conventional plastisol technology is almost exclusively based on poly(vinyl chloride) (PVC), whose processing relies on diffusion-controlled plasticizer absorption, gelation, and particle fusion. However, increasing environmental concerns and regulatory restrictions associated with phthalate plasticizers and chlorine-containing polymers have stimulated growing interest in the development of sustainable bio-based alternatives. Among potential candidates, poly(3-hydroxybutyrate) (PHB) has attracted considerable attention because of its renewable origin, biodegradability, and favorable mechanical properties. Nevertheless, the successful development of PHB-based plastisols remains challenging because their processing behavior differs fundamentally from that of conventional PVC plastisols. In contrast to the diffusion-dominated gelation mechanism of PVC, PHB exhibits rapid crystallization kinetics, narrow thermal processing windows, and complex crystallization-induced phase evolution, resulting in significant challenges for particle coalescence, film formation, and process control. This review critically examines the fundamental principles governing plastisol technology and compares the processing mechanisms of PVC- and PHB-based systems. Particular emphasis is placed on particle morphology, plasticizer diffusion, gelation and fusion behavior, crystallization kinetics, rheological evolution, heat transfer, and thermo-kinetic processing phenomena that govern final coating performance. Existing approaches for PHB plastisol formulation are critically evaluated, and the major scientific and technological barriers to industrial implementation are identified. Finally, key knowledge gaps are identified, and a research roadmap is proposed that emphasizes crystallization control, predictive thermo-kinetic modeling, and scalable processing strategies for industrial PHB plastisol technologies in advanced coating applications.