Cellulose Based -Biodegradable Polymers.pptx

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1. Types of Biodegradable Polymers Dr.D.Syam Babu

2. Introduction Rise of environmental pollution by synthetic polymers in developing countries have reached dangerous levels. Plastics produced from petroleum resources are not biodegradable. Because they defy microbial degradation , they end up in the landfills and damage the environment. Totop that off, oil prices have increased remarkably.

3. Classification of the biodegradable polymers

4. Evolvement of Bio-Based Polymers

5. Bio-Based Polymers Bio-based polymers are materials which are produced from renewable resources.

6. There are three principal ways to produce bio-based polymers using renewable resources Using natural bio-based polymers with partial modification to meet the requirements ( eg , starch) Producing bio-based monomers by fermentation/conventional chemistry followed by polymerization ( eg , PLA, PBS , and PE) Producing bio-based polymers directly by bacteria ( eg,PHAs ).

7. Bio-based polymers are broadly divided into two main categories: Starch-based polymers. Cellulose-based polymers.

8. Starch-Based Polymers Starch is primarily made up of two polysaccharides Amylose , a mostly linear α-D ( 1,4’ )- glucan and branched amylopectin, having the same backbone structure as amylose but with many α-1,6’ -linked branch points as shown in Fig The starch chains has a lot hydroxyl groups , two secondary hydroxyl groups at C-2 and C-3 of each glucose residue, as well as one primary hydroxyl group at C-6 when it is not linked. The available hydroxyl groups on the starch chains can be oxidized and reduced, and can help in the formation of hydrogen bonds, ethers, and esters Starch comprises of 10-20 % amylose and 80-90 % amylopectin depending on the source

9. Characteristics of starch-based polymers Some of the market drivers of starch-based polymers are: Lower cost materials than some other types of biodegradable polymers such as synthetic co-polyesters and PLA because of relatively cheap agricultural feedstock and simpler manufacturing process. Environmental-friendly than synthetic biopolymers; Starch blends have better physical and mechanical properties than pure plant based polymers.

10. Starch-based polymers are used in Applications which are used in natural environment such as agricultural and fishery materials. A pplications where reuse of the product is difficult and composting organic waste is effective. A pplications with specific features, where functionality and performance can also be completely separated from the main function.

11. Starch-based polymers are typically classified into four types: Thermoplastic starch (TPS) Starchsynthetic aliphatic polyester blends StarchPBS /PBSA polyester blends StarchPVOH blend

12. 1. Thermoplastic Starch TPS is similar to other polymers with linear and branched structures, molar mass, glass transition temperature, crystallinity, and melting temperature . However , in the presence of a plasticizer such as water, glycerin , sorbitol high temperatures ( 90 180 C ) and shearing, it melts and fluidizes , enabling its use in injection, extrusion, and blowing equipment such as those for synthetic plastics.

13. 2. Starch Synthetic Aliphatic Polyester Blends High-quality sheets and films for packaging are often made from blends of biodegradable synthetic aliphatic polyesters and starch. It is typical that approximately 50% of synthetic polyester is replaced with natural polymers, such as starch. Polyesters are also modified by incorporating different functional groups such as hydroxy , amine, and carbonyl that are capable of reacting with natural starch polymers.

14. When starch is blended with degradable polyesters such as PCL, the resulting blend is fully biodegradable. This has become focus of biodegradable polymer development. Typically , up to 45% of starch is blended with degradable PCL. Although, the blend is fully biodegradable , it is not strong enough for most applications. The melting temperature is relatively low around 60 C and it gets soft at temperatures above 40 C . Because of these drawbacks, starch PCL has limited applications .

15. 3. StarchPBS /PBSA Polyester Blends One of the major starch-based synthetic aliphatic polyester blends are starch PBS/PBSA polyester blends . PBS and polybutylene succinate adi pate (PBSA) are synthesized from 1,4-butanediol and succinic and/or adipic acid at 215 225 C under high vacuum. The resulting average molecular weight of 40 kg/ mol is not sufficient. In order to increase molecular weight to the desired level, a small amount of unsaturated carboxylic acid is added under addition polymerization initiated by peroxides.

16. StarchPBS /PBSA blends disintegrate in compost after 6 weeks. Some of their applications includes films for compostable trash bags, paper lamination, magnetic cards, sheets for thermoforming, extrusion forming , monofilament for fishing lines, woven nets, and ropes.

17. 4. Starch PVOH Blends Blending starch with biodegradable polyester results in phase separation and poor interfacial properties. Because PVOH degrades at high temperature when processed by melt processing, starch PVOH blend uses solution casting to produce films. However, low efficiency and high processing cost makes solution casting economically not viable and hence not the process of choice.

18. Mechanical properties of starch PVOH blends are directly impacted by the amount of the plasticizers added. Higher concentration of plasti cizer drastically improves mechanical properties and reduces waterabsorbance . In the case of citric acid, mechanical properties such as tensile strength and elongation at break are improved drastically with increase in the citric acid concentration.

19. Cellulose-Based Polymers Cellulose is a natural polymer made from long chains that are linked together by smaller molecules. These links in the cellulose chains consists of β-D-glucose. These sugar units are linked when water is eliminated by combining the H and hydroxyl group

20. There are two major cellulose-based polymers that are commonly used: 1. Cellulose esters 2. Celluloid

21. 1. Cellulose Esters Cellulose esters are part of a large family of cellulose derivatives that have found use in pharmaceutical and other applications. Cellulose ester is divided into two categories 1.1. Enteric 1.2. Nonenteric Enteric esters are those which are relatively insoluble in acid solutions but soluble in mildly acidic to slightly alkaline solutions such as cellulose acetate phthalate (CAP). Nonenteric esters are not dependent on pH solubility characteristics. They are mostly insoluble in water with the exception of cellulose acetates (CAs) with low level of acetyl

22. Ester/Cellulose ester Acid catalysis of an acid and alcohol also known as Fischer esterification process is the most important method for preparing an ester.

23. 1.1.1.Cellulose Acetate (CA) CA is the first organic ester of cellulosic family . CA is prepared by mixing cellulose with acetic anhydride using acetic acid as solvent and sulfuric acid as catalyst. Sulfuric acid reacts with acetic anhydride to form acetylsulfuric acid. During the acetylation process, both sulfuric acid and acetylsulfuric acid react with cellulose to form cellulose sulfate acid ester.

24. 1.1.2. Cellulose-Acetate Propionate (CAP) CAP was originally developed by the Celanese Plastics Company in 1931 . Similar to other acetates, it is made with the addition of propionic acid (CH3CH2COOH) in place of acetic anhydride

25. Uses Plastic grade CAP has an acetyl content in the range of 1.5 to 7 wt % and a propionyl content of about 39 to 42 wt %. Because of its high transparency, low-level light scattering, and good impact resistance, CAP is used in high-quality frames for sun glasses, personal protective equipment, and sport goggles.

26. 1.1.3.Cellulose-Acetate Butyrate Hercules Powder Company and Eastman Chemical jointly developed CAB during the mid-1930s . CAB is produced when cellulose is reacted with a mixture of sulfuric and acetic acids followed by esterification process. During the esterification process cellulose is reacted with butyric acid and acetic anhydrate.

27. This reaction is similar to the ones used in producing CA except that butyrate is also used. The end product has acetyl groups (CH3CO) and butyl groups (CH3CH2CH2CH) in the repeating cellulose unit.

28. Use CAB has acetyl content in the range of 13-15 wt %, a butyryl content of 34-39 wt %, and a free hydroxyl group of 1-2 wt %. CAB products have good dimensional stability among family of other acetates. They have excellent toughness, moisture resistance, and are available in fine colors. They are typical extruded and have found their use for automobile steering wheels, knobs, tool handles, packaging blisters, illuminated advertising signs, machine hoods, lamp covers, and dome lights

29. 1.2.Celluloid It all started when cellulose was treated with strong nitric acid to form nitrocellulose, which found some use as an explosive.

30. Once cellulose nitrate is synthesized, it is then mixed with camphor; a resin from the evergreen Cinnamomum camphora .

31. Some of the factors that can contribute to degradation of celluloid include T he purity of ingredient materials; The rinsing and drying processes, which may leave agents catalyzing degradation in the finished materials; T he kneading process.

32. Bacterial Polyesters Among all biodegradable polymers, polyesters are considered as a primary choice because of their hydrolyzable ester bonds. The polyesters are classified into two types: aliphatic polyesters and aromatic polyesters.

33. Some of the important characteristics of bacterial polyesters are as follows 1. They are water-resistant, and products made of the polyesters are water-tight. 2. The material can be processed by injection and blow molding . 3. Polyesters are not flexible and tend to become brittle. 4. Polyesters tend to lose their vapor barrier properties.

34. Some of the bacterial polyesters are: 1. Polyhydroxyalkanoate (PHA) 2. Polyhydroxybutyrate (PHB) 3. Poly( hydroxy - butyrate- hydroxyvalerate ) ( PHB/HV) 4. Poly( ε- caprolactone ) (PCL).

35. 1. Polyhydroxyalkanoates PHAs are a family of intracellular biopolymers produced by bacterial fermentation of sugar or lipids. They are produced by numerous bacteria to store carbon and energy.

36. Properties

37. Synthesis of PHA

38. Systems for PHA synthesis

39. Use

40. 2. Polyhydroxybutyrate PHB is the second member of the bacterial polyesters. It was synthesized from bacteria Bacillus magaterium by Lemoigne in 1925. PHBs are the class that is of interest for bio-derived and biodegradable plastics . The generalized chemical structure of PHB is:

41. 4. Synthetic Biodegradable Polymers

42. 1. Poly(lactic acid ) (PLA) PLA belongs to the family of aliphatic polyesters that are derived from renewable sources, mainly starch and sugar. It is a rigid thermo plastic polymer that can be semicrystalline or amorphous, depending on the stereochemistry of the polymer backbone. Lactic acid ( 2-hydroxyl propionic acid), the building block of PLA can exist either in D- or L-enantiomers . The properties of PLA will depend on the proportion of the enantiomers allowing production of PLA with wide range of properties to match with the performance requirements.

43. Thermal Degradation PLA tends to undergo thermal degradation in the molten state. Most of this form of degradation is related to processing of PLA which include process temperatures and the residence time in the extruder. Other factors that can contribute to thermal degradation of PLA include Hydrolysis by trace amounts of water; Depolymerization ; O xidative , random main-chain scission; I ntermolecular transesterification to monomer and oligomeric esters; I ntramolecular transesterification resulting in formation of monomer and oligomer lactides of low molecular weight.

44. 2. Poly( ε- caprolactone ) Poly(ε- caprolactone ) PCL is a semicrystalline , biodegradable polymer with melting temperature (Tm) of B 60 C and a glass transition temperature ( Tg ) of B2 60 C .

45. Synthesis PCL is synthesized by the ring opening polymerization of the cyclic monomer ε- caprolactone .

46. hydrolytic cleavage

47. 3. Poly( glycolide ) or Poly(glycolic acid) Poly( glycolide ) also known as PGA is a highly crystalline, biodegradable polymer having a melting point of 225 C and a glass transition temperature of 35 C . T

48. 4. Poly(p- dioxanone ) PDS is prepared by the ring opening polymerization of p- dioxanone .

49. 5. Bio-Derived Polyethylene Ethanol produced by fermentation from renewable resources can be used as a bio-fuel but also as a raw material for Bio-PE production. LDPE—Low-density polyethylene HDPE—High-density polyethylene