Polymeric Hydrogel Pipes for Irrigation Application

A novel generation of irrigation systems was introduced on the basis of hydrophilic, swellable, permeable, soft and flexible pipes using polymeric hydrogels. The prepared hydrogel pipes can connect to a water reservoir and buried around the root of the plant and continuously permeate water molecules directly to the root. The hydrogel pipes containing 9, 12 and 15 wt% of polyvinyl alcohol were prepared using a facile cyclic freezing–thawing technique. The effect of the polyvinyl alcohol loading level on the structural, physical and mechanical properties of the hydrogel pipes was investigated using the gel fraction, scanning electron microscopy, dynamic mechanical–thermal analysis, swelling and dehydration tests. The irrigating performances of the prepared pipes were investigated at the laboratory-scale by taking into account the effects of the polyvinyl alcohol loading level in hydrogels and the thickness of pipes. The results showed that the polyvinyl alcohol loading level has a direct effect on the gel fraction and mechanical strength of the hydrogel pipes. However, the pore size and the swelling and dehydration abilities of the hydrogel pipes were inversely depended on the polyvinyl alcohol loading level. The prepared hydrogel pipes successfully passed the laboratory-scale irrigation study and it was shown that a typical hydrogel pipe with an outer diameter of 15 mm and a length of 150 mm can continuously permeate water molecules to the soil and keep a permanent moist condition in soil around the pipe, using less than 700 mL water per 3 months.