Innovations and Opportunities in the Super Absorbent Polymers Market

Super Absorbent Polymers: Changing the Diaper Industry

Introduction
Super absorbent polymers (SAPs) are advanced materials that can absorb and retain extremely large amounts of a liquid relative to their own mass. When dry, SAPs consist of granules or fibres around 1 millimetre in diameter. However, when wet, they can swell to around 30 times their dry size. This unique ability to absorb liquid has made SAPs incredibly useful as a core component in disposable diapers and feminine hygiene products like sanitary pads and pantyliners.

How do SAPs Work?
At a molecular level, SAPs are cross-linked polymers that contain a number of hydrophilic functional groups such as carboxylic acid and sulfonic acid. These groups readily interact with water molecules through hydrogen bonding. When SAPs come into contact with liquid, the hydrogen bonds between the liquid and polymer chains cause the polymers to expand extensively through osmotic pressure. This absorption process happens extremely quickly within seconds. The polymers then maintain their swollen gel structure, preventing reabsorption of the liquid even under pressure. This super absorbency enables SAPs to absorb up to 300-400 times their own weight in fluids like urine or blood.

History and Synthesis of SAPs
The SAPs used today are mostly cross-linked polyacrylate polymers, though other polymers like polyvinyl alcohol can also be used. The first patents for super absorbent polymers date back to the late 1960s when researchers developed cross-linked starch-acrylonitrile graft copolymers. However, these early SAPs had poor absorption performance. It was not until 1978 that a Japanese company Nippon Shokubai developed highly efficient polyacrylate SAPs made through reverse-phase suspension polymerization. Nowadays, polyacrylate SAPs are manufactured through a free-radical polymerization reaction of acrylic acid that is subsequently cross-linked and surface treated. Continuous improvements in synthesis have led to SAPs w