Anionic polyacrylamides

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Anionic polyacrylamides soil conditioners Jozef
Kollár
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Polymeric soil conditioners, were known since the
1950s. These polymers were developed to improve
the physical properties of soil in view of

• increasing their water holding capacity
• increasing water use efficiency
• enhancing soil permeability and infiltration
  rates
• reducing irrigation frequency
• stopping erosion and water runoff
• reduce fertilizer and pesticides losses

Wide commercial application failed even though
the scientific basis for their use was quite well
established.

• Reasons
• most of the studies with polymers were performed
  in the laboratory without consideration for the
  economics at the production level in large scale
  agriculture
• complexity of application and poor distribution
  in the soil

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The most commonly used water-soluble synthetic
soil-conditioning polymers included
poly(ethylene glycol) poly(vinyl alcohol)
polyacrylates polyacrylamide
poly(isobutylene maleic anhydride)
poly(maleic anhydride-co-vinyl acetate)
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Gel forming polymers
Gel forming polymers or insoluble water
absorbing polymers were first introduced for
agricultural use in the early 1980s. These
polymers do not possess linear chain structures
as described previously but the chains are rather
crosslinked to form a three dimensional network.

• Advantages
• Great water absorbing properties
• Amount of crosslinker influenced a mechanical
  properties of hydrogels
• Reduce water stress of plants
• Hydrogels are also claimed to reduce fertilizer
  leaching

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Polyacrylamide (PAM) is one of the most widely
employed soil conditioner

• Advantages
• Low toxicity
• Safe
• Inexpensive
• Relatively stable

PAM
More recently, polyelectrolytes such as
acrylamide/acrylate copolymers have attracted
much attention as they have been shown to be most
effective in improving the properties of soils.
poly(acrylamide-co-acrylic acid)
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PAM as soil conditioner

• Reduce surface sealing
• Increase seedling emergence
• Reduce runoff and erosion
• Reduce fertilizer and pesticides losses

The adsorption of PAM to soil particles depends
on both the polymer and the soil properties. PAM
differ with respect to molecular weight, charge
density and charge type.
Principle of adhering PAM molecule to soil
particles
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Polyacrylamide Types
Granular
Emulsion
Solid
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PAM can be used in furrow or sprinkler irrigation
furrow irrigation
sprinkler irrigation
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PAM in furrow and sprinkler irrigation

• Reduces soil loss
• Prevent the loss of nutrients
• Increase infiltration
• Improvement of aggregate stability
• Increase quality of soil as well as water

PAM treated furrow following irrigation
Untreated furrow following irrigation
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Synthesis of poly(acrylamide-co-tulipalin)
hydrogels with crosslinker BIS
a-methylene-?-butyrolactone also known as
Tulipalin A, is present in white tulips and is
identified as a substance with fungitoxic
activity.
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Swelling capacity in water
dry hydrogel
swollen hydogel
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Swelling capacity in water
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Rheology of hydrogels
Rheology is study of deformation and flow of
material
prediction of viscoelastic properties of
polymers.