Plastisol foaming process. Decomposition of the foaming agent, polymer behavior in the corresponding temperature range and resulting foam properties

• Published in: Polymer engineering and science Vol. 53; no. 8; pp. 1712 - 1718
• Main Authors: Verdu, J., Zoller, A., Marcilla, A.
• Format: Journal Article
• Language: English
• Published: Hoboken Wiley Subscription Services, Inc., A Wiley Company 01.08.2013; Wiley; Society of Plastics Engineers, Inc; Blackwell Publishing Ltd; Wiley-Blackwell
• Subjects: Applied sciences; Blowing agents; Bubbles; Cellular; Chemical properties; Chemical Sciences; Composition; Decomposition; Decomposition (Chemistry); Deformation; Density; Engineering Sciences; Exact sciences and technology; Foaming; Foaming agents; Forms of application and semi-finished materials; Identification and classification; Materials; Mechanics; Plastic foams; Plasticizers; Plastisols; Polymer industry, paints, wood; Polymeric composites; Polymers; Polyvinyl chloride; Production processes; Shear modulus; Technology of polymers; Thermal properties; Viscosity; Spain; Viscosity; Plastisol; Shear modulus; Thermal decomposition; Adipate polymer; Ester polymer; Temperature effect; Blowing agent; Mechanical properties; Experimental study; Cellular plastic; Property processing relationship; Density; PVC plasticizer; Azo compound; Additive; Foaming process; Technological properties; Plastics; Rheological properties; Azodicarbonamide; Viscosity effects; Decomposition rate; Decomposition reaction; Foam properties; Temperature range; Heat of decomposition; Diethyl phthalate
• ISSN: 0032-3888; 1548-2634
• DOI: 10.1002/pen.23430

The decomposition of azodicarbonamide, used as foaming agent in PVC—plasticizer (1/1) plastisols was studied by DSC. Nineteen different plasticizers, all belonging to the ester family, two being polymeric (polyadipates), were compared. The temperature of maximum decomposition rate (in anisothermal regime at 5 K min−1 scanning rate), ranges between 434 and 452 K. The heat of decomposition ranges between 8.7 and 12.5 J g−1. Some trends of variation of these parameters appear significant and are discussed in terms of solvent (matrix) and viscosity effects on the decomposition reactions. The shear modulus at 1 Hz frequency was determined at the temperature of maximum rate of foaming agent decomposition, and differs significantly from a sample to another. The foam density was determined at ambient temperature and the volume fraction of bubbles was used as criterion to judge the efficiency of the foaming process. The results reveal the existence of an optimal shear modulus of the order of 2 kPa that corresponds roughly to plasticizer molar masses of the order of 450 ± 50 g mol−1. Heavier plasticizers, especially polymeric ones are too difficult to deform. Lighter plasticizers such as diethyl phthalate (DEP) deform too easily and presumably facilitate bubble collapse. POLYM. ENG. SCI., 2013. © 2012 Society of Plastics Engineers