Super-absorbent powders: what they are and how they work.
Superabsorbent powders are used in a wide range of products that need to absorb and retain large amounts of liquid: from diapers and incontinence products to medical applications and absorbent pads for food packaging.
Also known as SAPs, an acronym for Super Absorbent Polymers, their properties are determined by the particular structure of the polymers they contain. Composition, degree of crosslinking and manufacturing process all influence their characteristics and performance in different applications.
How super-absorbent powders work
Superabsorbent powders generally consist of crosslinked hydrophilic polymers which swell when they come into contact with water or other liquids, retaining the liquid within their structure.
The molecular structure of crosslinked hydrophilic polymers forms a three-dimensional network of long polymer chains. The degree of crosslinking influences the behaviour of the material and its absorption properties.
The ability to absorb and retain liquids is also related to the presence of hydrophilic functional groups, which interact with water molecules.
In sodium polyacrylate-based SAPs, when the material comes into contact with a liquid, the dissociation of ions generates osmotic pressure that draws the liquid into the structure. The particles gradually swell until a gel is formed.
Absorption capacity varies depending on the composition of the SAP and the liquid it comes into contact with. The presence of salts and the pressure applied to the material can also significantly affect its performance.
Where they are used
The ability to absorb and retain liquids makes SAPs suitable for a variety of applications.
In hygiene products, such as diapers, incontinence products and feminine hygiene products, they are incorporated into the absorbent core to absorb and retain liquids.
In some medical applications, superabsorbent materials can be used in products designed to manage exudates.
In food packaging, they are used in the absorbent core of pads designed to manage liquids released by packaged food.
They are also used in other industrial and technical applications where absorption and retention properties are required for specific purposes.
Spongel, a different formulation of superabsorbent material
Research into superabsorbent materials focuses not only on performance, but also on developing formulations that differ from conventional SAPs. This is the context in which Magic developed Spongel, a cellulose-based superabsorbent powder whose formulation contains 85% organic material.
Spongel absorbs and retains liquids and can be incorporated into the absorbent core of materials and products intended for different applications.
Its performance can be measured using different parameters. In saline solution, Spongel reaches a free absorption capacity of up to 70 g/g and absorption under load values of more than 20 g/g. Its ability to retain liquid after centrifugation of the saturated SAP reaches approximately 35 g/g.
Alongside its absorbent properties, Spongel has a specific end-of-life characteristic: in the configurations covered by the relevant certificate, it is OK Compost Industrial certified by TÜV Austria for industrial composting.
In 2017, Spongel also received first prize in the “Raw Materials and Innovation” category at the INDEX Awards in Geneva.
From Spongel to Airgel g-grade
One of the applications of Spongel developed by Magic is Airgel g-grade, an airlaid material designed for applications requiring high absorption capacity.
The structure of Airgel g-grade does not use thermoplastic fibres and incorporates Spongel as its superabsorbent component. In the configurations covered by the relevant certificate, Airgel g-grade is also OK Compost Industrial certified by TÜV Austria for industrial composting.
The material can be used as an absorbent component in different applications, including pads for food packaging and products for the medical and hygiene sectors.
Its structure can be configured according to the performance required by the application, by adjusting parameters such as basis weight and absorption capacity.
From material to product: the case of G-pad
In food packaging, Airgel g-grade is also used to produce G-pad, the absorbent pad developed by Magic to manage liquids released by packaged fresh food.
G-pad combines an Airgel g-grade absorbent core with a compostable film. In the configurations covered by the relevant certificate, the pad is OK Compost Industrial certified by TÜV Austria for industrial composting.
The certification therefore refers to a specific characteristic of the product and to defined end-of-life treatment conditions. Disposal should be based on the instructions provided with the product and the requirements of the local waste collection system.
Different materials for different requirements
Superabsorbent powders perform a specific function: absorbing and retaining liquids. But this function can be achieved through materials with different structures, compositions and performance characteristics.
For this reason, the choice of SAPs does not depend on a single property. Free absorption capacity, absorption under load, retention, composition and application requirements all need to be considered together.
The development of Spongel and its use in materials such as Airgel g-grade illustrate one of the areas being explored in superabsorbent research: developing different material formulations while keeping the performance required by the application at the centre of the process.
