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United States Department of Agriculture

Agricultural Research Service

Research Project: DEVELOP MANAGEMENT TOOLS FOR EARLY STRESS DETECTION AND EFFICIENT AGROCHEMICAL UTILIZATION FOR PROTECTED HORTICULTURE CROPS

Location: Application Technology Research Unit

Title: Polyacrylamide Hydrogel Properties for Horticultural Applications

Authors
item Kim, Sangjoon -
item Iyer, Ganesh -
item Nadarajah, Arunan -
item Frantz, Jonathan
item Spongberg, Alison -

Submitted to: International Journal of Polymer Analysis and Characterization
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: January 6, 2010
Publication Date: July 5, 2010
Citation: Kim, S., Iyer, G., Nadarajah, A., Frantz, J., Spongberg, A. 2010. Polyacrylamide Hydrogel Properties for Horticultural Applications. International Journal of Polymer Analysis and Characterization. 15: 307-318.

Interpretive Summary: Water-holding polymers (also called hydrogels) made out of polyacrylamide (PAAm) are commonly used in container production to improve hydration of the growth substrate. This is believed to minimize crop losses during crop production and in the sales areas. However, careful studies of the effect of these materials have shown that they have a little, if any, effect on crop life and quality. The reasons for this poor performance are not understood as the synthesis and chemical properties of commercial hydrogels have not been adequately characterized, and manufacturers of the materials do not report their exact chemistry/synthesis processes. In this study PAAm hydrogels were synthesized and their properties were measured and compared to commercially available hydrogels. Hydrogel swelling, density and electron microscopic analyses showed that the commercial hydrogels were most likely not pure PAAm materials, but a polyacrylamide-based material that also contained ionic or charged groups. This modification greatly increases the water absorption properties of the hydrogels but makes the material extremely fragile. Measurements of hydrogel dehydration under controlled conditions showed that they were able to retain moisture for only a few hours. Large pores in the gels allowed the water to be easily transported out. The fragility also resulted in the gels easily breaking up into smaller pieces when handled in a typical commercial manner, which likely contributed to observed poor water retention. Hydrogels with improved water retention and structural integrity need to be produced if these materials are to have a significant impact in horticulture.

Technical Abstract: Polyacrylamide (PAAm) hydrogels are commonly employed to ensure hydration of the growth media and minimize crop losses during the crop production and postproduction phases in horticulture. However, studies of the effect of these materials have shown that they have a minimal effect on crop life and quality. The reasons for this poor performance are not understood as the commercial hydrogels have not been adequately characterized. In this study PAAm hydrogels were synthesized and their properties were measured along with those of commercially available hydrogels. Hydrogel swelling, density and SEM analyses showed that the commercial hydrogels were most likely not pure PAAm materials, but a derivative with ionic groups. This modification greatly increases the water absorption properties of the hydrogels but at a cost of extreme fragility. Measurements of hydrogel dehydration under controlled conditions showed that they were able to retain moisture for only a few hours. Large pores in the gels allowed the water to be easily transported out. The fragility resulted in the gels easily breaking up into smaller specimens which are likely to have contributed to the poor water retention. Hydrogels with improved water retention need to be produced if these materials are to have a significant impact in horticulture.

Last Modified: 12/18/2014
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