Title: Anionic polyacrylamides
1Anionic polyacrylamides soil conditioners Jozef
Kollár
2Polymeric 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
3The 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)
4Gel 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
5Polyacrylamide (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)
6PAM 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
7Polyacrylamide Types
Granular
Emulsion
Solid
8PAM can be used in furrow or sprinkler irrigation
furrow irrigation
sprinkler irrigation
9PAM 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
10Synthesis 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.
11Swelling capacity in water
dry hydrogel
swollen hydogel
12Swelling capacity in water
13Rheology of hydrogels
Rheology is study of deformation and flow of
material
prediction of viscoelastic properties of
polymers.