Water holding polymers and their types .pptx

This ppt briefs about various water holding polymers and their types, characteristics and their relevance

1. Water holding polymers and their relevance Presented By Rajat Kumar (F-2024-55-M) To Nitin Sharma (Assistant Professor)

2. WATER HOLDING POLYMERS Water as universal solvent plays an pivotal role in agriculture but in some areas of this part of the world there is shortage of water , Droughts , soil desertification is common thing which challenges the food security and the sustainable development of agriculture. So water holding polymers or superabsorbent polymers (SAP’s) due to their water absorption and retention capacity can improve the water utilization and have great importance in agriculture Water holding polymers /Superabsorbent polymers – These are polymers consists great number of hydrophilic groups as chains which helps them to absorb water hundreds times of their own masses. These polymers applied to effectively ameliorate utilization of water in agriculture and reduce the irrigation water consumption .

3. TYPES OF POLYMERS NATURAL POLYMERS Cellulose Starch Lignin Chitosan SYNTHETIC POLYMERS P OLYACRYLICACID (PAA) P OLYACRYLAMIDE (PMA) P OLYVINYL ALCOHOL (PVA) P OLYURETHANE FOAM (PU) SEMI-SYNTHETIC POLYMERS Pusa hydrogel Cassava Starch-based SAP

4. CELLULOSE Cellulose is the most abundant natural organic substance in the world. It comes from a wide range of sources, including cotton, wood, plant straw and so on. Due to a large number of hydrophilic groups (hydroxyl groups) on the chain. cellulose can be readily exploited to prepare water-retention agents for agricultural applications . Nevertheless, the absorbency of neat cellulose is very low (below 30 g/g in distilled water) owing to highly dense crystalline structure. Cellulose mixed with linseed gum solutions and cross-linked by epichlorohydrin demonstrated exceptional salt tolerance, showing considerable water absorbency of about retaining agents. For example, cellulose mixed with linseed gum solutions and cross-linked by epichlorohydrin demonstrated exceptional salt tolerance, showing considerable water absorbency of about 210 g/g in 0.1 M NaCl.

5. STARCH Starch is a biomacromolecule polymerized of glucose and widely used as water retaining agents, which is strong in hydrophilicity, degradability and environmental friendliness but weak in water absorbency (below 10 g/g in distilled water), mechanical stability and salt tolerance. Grafting AA to starch is a common method to improve the water absorbency of starch-based water retention agents. AA was used to polymerize with sulfamic acid-modified starch by solution polymerization. The water absorbency of the resulting product was 1026 g/g in deionized water and 145 g/g in 0.9 wt % NaCl solution. Hybriding starch and inorganic fillers is another method to improve water absorbency even in salt solution and under load.

6. LIGNIN Lignin has also have the ability to improve the water absorption of materials. Organosolv lignin that extracted from hybrid poplar was grafted on 2-hydroxyethyl methacrylate (HEMA) to fabricate lignin-methacrylate composite hydrogels. The water retention rate and thermal stability of resultant composite hydrogels were increased by 39% and 20% .

7. CHITOSAN Chitosan is a linear chain polysaccharide derived by deacetylation of chitin, which is abundant in the outer skeleton of crustaceans and the cell walls of fungi . A range of inherent properties, such as excellent biocompatibility, biodegradability and repeatability, make chitosan a very attractive material for water retention agents. However, chitosan has horribly low water absorbency (below 10 g/g). In order to enhance chitosan’s water absorbency, (2-pyridyl) acetyl chitosan chloride (PACS) was chose to polymerize with AA and AM in aqueous solution. The resulting polymer has excellent water absorbency, which can absorb 615 times its dry weight of distilled water and 44 times its dry weight of 0.9 wt % NaCl . This product also showed good antibacterial properties against Escherichiacoli which has a broad application prospect.

8. KONJAC GLUCOMANNAN Konjac glucomannan (KGM) also has superior water absorption and film formation ability compared with starch. KGM-g-P(AA-co-AM) achieved maximum water absorption rate of 650 g/g in distilled water and 70 g/g in 0.9 wt % NaCl . The water absorption rate in distilled water of KGM-AA polymers can reach to 1941 g/g by adding kaolin as fillers, which indicates kaolin is a potential material to enhance water absorbency .

9. POLYACRYLIC ACID Polyacrylicacid (PAA) and sodium polyacrylate ( PNaA ) SAPs are the most widely used water retention agents as a result of superior water absorbency (300–500 g/g in water) and water retention capacity. But the effectiveness of these polymers is hampered by low salt resistance, weak mechanical strength and non-degradability. So to improve their salt-tolerance, mechanical properties and degradability the addition of clay, such as kaolin, montmorillonite and bentonite, result in increasing water absorbency and enhancing mechanical performances of these SAPs. A slow-release fertilizer with a semi-IPN structure based on kaolin-g-P( AAco -AM) and linear urea-formaldehyde oligomers (UF) showed excellent water absorbency of 68 g/g in tap water . Hybrid linear low density polyethylene (LLDPE)-g-PAA/montmorillonite showed optimum water absorbency of 800 g/g in distilled water.

10. POLYACRYLAMIDE Polyacrylamide (PAM) is secondly commonly used synthetic SAP after PAA. It has similar water absorbency to PAA. However, low salt tolerance and poor mechanical properties severely hampers its application. Thus many strategies have been proposed to enhance comprehensive performance of PAM. To increase the water absorbency of PAM, a starch-g-PAM superabsorbent was prepared and showed the maximum absorption of 1452 g/g and 83 g/g for distilled water and 0.9 wt % NaCl solution. It is also found that the introduction of NaOH-induced hydrolysis to the last stage of gel polymerization can enhance the water absorbency of the AM system.

11. POLYVINYL ALCOHOL Polyvinyl alcohol (PVA) is a synthetic hydrophilic polymer with medium water holding capacity, which can degrade with the help of bacterial enzymes. Though the water absorbency of PVA is inferior to PAM, PVA with the appropriate degree of alcoholysis have more beneficial influence on plant growth in sandy soil compared with PAM. Constructing semi-IPN by linear PVA is a general method to ameliorate the comprehensive performances of PVA based water Polymer retention agents. 3 wt % PVA was added into hemicelluloses-g-AA/bentonite matrix (HAB) and a semi-IPN was formed to enhance swelling properties. The maximum absorbency in the distilled water and 0.9 wt % NaCl .

12. POLYURETHANE FOAM Polyurethane (PU) foam is widely used in many fields. It has high mechanical strength but low water absorbency. Thus, the composite of PU foam and sodium polyacrylate ( PNaA ) was prepared to combine the advantages of both. It showed that the content of 5.5 wt % PNaA could achieve water absorption of 891% and water retention of 408% . which increased twice and eleven times respectively compared to the pure PU foam. And the strength of the composite enhanced a lot compared with the pure PNaA .

13. PUSA HYDROGEL This hydrogel is developed by IARI ,New Delhi . It exhibits maximum absorbency at tempratures (40-50 c). It absorbs water 400 times of its weight and gradually releases the same . It remains stable in soil for one year. It remains less affected by salts and low rates of application.

14. STARCH BASED-CASSAVA It is semi synthetic polymer developed by Central Tuber Crop Research Institute , Kerala. It uses cassava starch backbone and contain no detachable level of the monomer ,acrylamide . Absorbency ranges from 400-425 g/g of the dry sample.

15. CHARACTERSTICS OF SAP’S High water absorption capability. Lowest soluble content and residual monomer. High biodegradability and biocompatibility. High performance over a wide temperature range. After swelling , water becomes netral in pH . Colourlessness , odourlessness and non toxic . High Durabiility and stability during swelling and storage . Desired rate of absorption and desorption capacity . Photostability , rewetting capability for a longer time , low- cost material , and ecofriendly .

16. RELEVANCE OF WATER HOLDING POLYMERS Agriculture – The water holding polymers can be used as soil conditioners to improve soil quality and increase crop yield . They can also help to reduce the water consumption. Hydroponics – Alsta hydrogel , a potassium polyacrylate based polymer can be used in hydroponics open fields .It can absorb and release water 300-500 times and can help reduce the need for irrigation. Soil conditioning – Water holding polymers can imoprove soil’s hydro- physical , physiochemical and biological environments. Environmental quality – Water holding polymers are non polluting and biodegradable. Nutrient use and crop yield – They improve both of them.

17. 6. Seed coating – These polymers can be used for coating of seeds to improve germination rates and seedling growth. 7. Fertilizer enhancement – These can be added to fertilizer to increase its effectiveness by retaining moisture and nutrients nearv the root of the plants. 8. Drought Management – These can be used to mitigate the effect of drought by retaining water in the soil and making it available for plants when needed. 9. Soil remediation – These can be used to clean up contaminated soil by absorbing and retaining pollutants. 10. Landscaping – These can be used in landscaping to improve soil moisture retention reducing the need for frequent watering and promoting plant growth.

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