Biodegradable polymers for industrial applications pdf

The renewable sources for bio-based polymers are diverse. Bio-based polymers have been synthesized from plant-based precursors containing lignocellulose fibers, cellulose esters, polylactic acid, and polyhydroxyalkanoates PHA [ 11 ]. The lignocellulosic fibers are derived from plants such as curaua, pineapple, sisal, and jute [ 18 ]. The physical properties of the final product are largely determined by the extraction method.

On the downside, even though cellulose is a bio-based material, the precursor is non-biodegradable due to the higher degree of substitution [ 4 ]. In contrast to other renewables, which are sourced from plants, agricultural waste comprises of post-harvest waste, by-products of food processing such as coconut shells [ 20 ], potato peels [ 1 ], fruit peels [ 21 ], and fruit seeds [ 22 ], which have been traditionally discarded as waste in farms and food processing facilities.

Agricultural waste is a primary source of starting materials, which are used in the production of bio-based plastics, plasticizers, and antioxidant additives [ 1 ]. Vegetable-based agricultural wastes are a vital source of polysaccharides, which are essential precursors in the development of natural plasticizers [ 23 ].

The main function of the plasticizers is to enhance the elasticity and mechanical strength of the bio-based polymers. The performance of vegetable-derived polysaccharide plasticizers relative to glycerol and other synthetic plasticizers has not been determined [ 22 ], and commercial application is limited. Agricultural waste such as mango kernel extracts, green tea extracts, essential oils, proto-catechuic acid, grapefruit seed extract, and curcumin sourced from food processing facilities are used in the development of antioxidant additives [ 1 ].

Other agro-wastes that are viable sources of natural antioxidants include pomegranate peel extract PE , mint plant extracts ME [ 21 ], Thymus vulgaris L. The phenols in the natural antioxidants are Lewis bases and electron donors, which are critical to the anti-oxidation activities. Apart from phenols, pomegranates contain gallic acid and gallates, which are natural stabilizers and indicators of aging [ 25 ]. Bashir, Jabeen, Gull, Islam, and Sultan noted that these materials had the prerequisite antioxidant activity that was linked to the ability to scavenge for OH groups and oxygen radicals in 2,2-diphenylpicryl-hydrazyl-hydrate DPPH.

The performance of these materials is comparable to synthetic antioxidants and could, therefore, replace existing additives such as the carcinogenic butylated hydroxytoluene [ 21 ]. The main challenge is that the performance of the natural additives on a commercial scale has not been confirmed.

The main function of the additives is to inhibit the UV-based photodegradation of the plastics following exposure to sunlight [ 26 ].

However, the utilization of natural additives is a new phenomenon; commercially available bio-based plastics have incorporated synthetic additives. Apart from the incorporation of natural additives, UV-induced degradation is inhibited by maleic anhydride treatment, direct, reactive mixing, and graft copolymerization during synthesis [ 27 ]. The utilization of waste from renewable sources for commercial purposes has the potential to reduce the rates of global warming, considering that compositing and landfilling contribute to global warming.

Data collected from Italy show that the recycling of agricultural waste through composting and the production of fertilizers increases global carbon emissions. In particular, 64 and 67 kg of CO 2 equivalent was generated per mg from olive waste-based compost OWC and anaerobic digester-based compost AD , respectively. Additionally, re-composting and co-composting generated between 8 and 31 kg of CO 2 per mg of compost [ 28 ].

The data obtained from the composting experiments show that recycling of agricultural waste poses a threat to the environment, and it is not ecologically beneficial as initially proposed. The significant quantities of CO 2 equivalent emissions generated per mg of compost indicate that novel methods of utilizing agricultural waste such as the production of bio-based polymers are necessary; this because the latter methods are more sustainable and have a lower ecological impact based on the LCA analyses.

Global statistics show that the production of bio-based plastics from renewable sources was low—2. The demand for bio-based plastics in food packaging is based on the unique material properties of biofilms relative to synthetic alternatives. The bio-based polymers absorb ethylene, remove water vapor, protect fruits and vegetables from microbial contamination due to the presence of anti-microbial agents [ 30 ], protect against UV radiation, and are easily recyclable [ 31 ].

Current bio-based polymers have shown effective antimicrobial performance against Bacillus subtilis, Escherichia coli, and Listeria monocytogenes [ 32 ].

The bio-based films have other essential properties that influence the development of intelligent packaging systems [ 33 ]. The leading synthetic plasticizers include polyethylene glycol, citrate ester, and oligomeric acid [ 4 ]. Rameshkumar, Shaiju, Connor and Babu [ 34 ] noted that global estimates are not entirely accurate due to the complexity of the supply chains, continuous innovation, and commercial release of new varieties of bio-based polymers.

The data show that there were two inherent challenges associated with the production of bio-based polymers. Firstly, the production capacity is low, and it cannot match the production of non-renewable plastics, whose production was estimated at million tons [ 10 ]. Other challenges are discussed in Section 3.

Considering the global variability in the availability of agricultural waste, the development of the materials would be concentrated in specific geographical areas.

For example, fruit peels and coconut shells are found in abundance in tropical and coastal areas, respectively [ 20 ]. Since India and China have a high fruit and vegetable production capacity [ 19 ], agro-wastes synthesized from fruit and vegetable wastes would be abundant in Asia. Coconut shells and microalgae are abundant in coastal areas and marine environments, respectively [ 20 , 35 ].

Jackfruits and other similar plants grow best in tropical and subtropical climates [ 20 ]. The data show that the production of bio-based plastics from agro-waste should be customized to suit the available precursors. The development of bio-based polymers from locally available agricultural wastes would also help to reduce the carbon footprint. PHAs are further grouped into long-chain, medium, and short-chain polymers [ 16 ]. The length of the chains predicts the utility in commercial applications; short-chain polymers are not ideal in high strength applications owing to their brittleness, high degree of crystallinity, and stiffness.

Medium chains are less susceptible to brittle fracturing owing to the high elastic modulus, flexibility longer elongation at break , and low crystallinity. However, the materials are less suitable for high-temperature applications [ 16 ]. The selection of suitable agro-waste is based on the following primary criteria: i starch content; ii cellulose and lignin and hemicellulose content iii bioavailability and impact on agricultural supply chains and food security iv complexity of the synthetic routes and desired material properties; v biodegradation [ 20 , 35 , 37 , 38 ].

Experimental data indicate that the production of biopolymers involves a tradeoff between the cellulose content and the rate of biodegradation—plant cellulose limits the rate of biodegradation but enhances the mechanical strength of the polymer films—a challenge that has been resolved by Xie, Niu, Yang, Fan, Shi, Ullah, Feng, and Chen [ 1 ].

The study reported the successful replacement of plant cellulose with bacterial cellulose [ 1 ]. The cellulose and starch content are limiting factors in the selection of agricultural waste precursors. Chemical composition of common forms of agricultural waste [ 39 ]. Bio-based polymers synthesized from different agro-wastes have distinct material properties. Thick films have better mechanical properties compared to thin films. For example, Chlamydomonas reinhardtii microalgae species yield the highest starch content after h of inoculation [ 35 ].

Based on the inoculation experiments, Chlamydomonas reinhardtii microalgae species would be highly preferred as precursors in the development of bio-based polymers compared to other species such as Scenedesmus sp and Chlorella variabilis.

Starch content is one of the primary criteria in the selection of the agricultural precursor. The preference for species with a high starch content involves a tradeoff with the rate of culture growth. Similarly, a higher cellulose content augments the mechanical strength but limits the rate of biodegradation [ 11 , 40 ]. Starch is a polysaccharide found in tubers, legumes, and cereals agro-wastes and is an ideal carbon precursor for bio-based polymers [ 41 ].

Thermoplastic starch-based polymers are practical alternatives to petroleum polymers based due to effective reinforcement properties, abundance, and tunable properties [ 38 ]. The base material, starch derived from potatoes, cereals, and corn , is abundant in the biosphere [ 35 ] and it has been extensively explored in research, as noted by Tabasum, Younas, Ansab, Majeed, Majeed, Noreen, Naeem, and Mahmood [ 42 ].

The first phase in the production of starch-based polymers from agro-wastes involves the addition of L-lactate and a catalyst Sn oct 2. W1 denotes the starting weight and final weight. The main challenge with this synthetic route is eco-toxicity. The use of toxic chemicals impacts the cradle-use-disposal cycle. Current research has shown that these materials are critical to the future of sustainable food packaging because they are flexible and light [ 34 ].

Commercial application is limited by poor water resistance, poor mechanical strength, and risk of dissolution in water—a challenge that is addressed by blending with other polymers to enhance the mechanical strength. Alternatively, TS materials are reinforced by the incorporation of ionic liquids such as 1-butylmethylimidazolium chloride in the pretreatment process and the production of bio-composites [ 44 ].

The surface treatment process results in the development of materials with greater activation energies, which predicted the rates of thermal degradation. The rate of thermal degradation influences end of life treatment and application in high-temperature applications. Other constraints include complex synthetic processes such as plasticizing, casting, and extrusion, which are difficult to replicate on a commercial scale.

The material property challenges associated with the starch-based polymers are dependent on the starch precursor. Sugar palm, microalgae, and jack fruit result in starch-based polymers with distinct properties [ 22 , 35 , 37 ], and the synthetic route should be customized to suit the polymer applications.

The natural properties of bio-based polymers are modified through the addition of tetraethoxysilane TEOS , polyvinyl alcohol PVA , and chitosan. The PVA is used to enhance mechanical properties [ 46 ]—a higher PVA ratio compared to the filler was correlated with greater mechanical strength. However, the chemicals borax and formaldehyde used in the chemical cross-linking of the biopolymers are toxic and non-biodegradable [ 21 ]. Apart from the material constraints and complex synthetic routes, the sustainability of starch-based polymers is questionable on a commercial scale because starch sources are staple foods in most countries.

From a food security perspective, large-scale commercial production of thermoplastics might be a threat to food security. The challenges and viable alternatives in the commercialization of biodegradable polymers are discussed in the next section. The production process of bio-based polymers from pineapple peel is based on a standard method that involves the extraction of biopolymers from agricultural waste.

Once the number of trace metals, ash, and carbohydrates, protein, the peels are fermented using dipotassium phosphate or ammonium sulfate and subsequently hydrolyzed with H 2 SO 4 , the biopolymers are extracted via centrifugation at a rate of rpm or higher. Additionally, the biopolymer yield is influenced by time and pH optimization. The optimal time and pH were 60 h and 9, respectively [ 48 ].

The yield data show that chemically induced fermentation was capable of complementing natural bacterial synthesis methods. The only constraint is the possible adverse effect of synthetic chemicals such as H 2 SO 4 and dipotassium phosphate or ammonium sulfate, among other chemicals, which may potentially contribute to acidification and eutrophication [ 49 ] in the environment if used in large quantities.

The production of bio-based polymers from tomato pomace follows a similar approach as the production of bio-based polymers from the pineapple peels [ 8 , 48 ], except for the melting poly-condensation step.

The mechanical properties of biopolymers derived from tomato pomace are presented in Figure 2 A. The volume of the catalyst Sn oct 2 impacted the depth of the indent caused by the Brinnell hardness, as shown in Figure 2.

Optimal depth was reported in samples with 0. Reproduced with permission from publisher. Apart from the production of bio-based polymers, fruit peels are effective in enhancing the mechanical properties of manufactured polymers. Additionally, there was good particle distribution and particle-matrix adhesion. Even though the sweet lime and lemon peel showed ideal properties in the reinforcement of the structures, the sustainability aspect remains a challenge; this is because the lemon and sweet lime fruits are edible and the commercial availability of waste fruit peels is not guaranteed.

In advanced markets, the fruit peels are used to produce value-added products such as bioactive polyphenols [ 50 ]. Phenol-containing compounds have natural antioxidant capabilities [ 21 ]. Alternatively, the peels are ingredients in the manufacturing of home-based beauty products.

The production of lactic acid and poly-lactic acid from agro-wastes is discussed in the next section. The production of lactic acid and poly-lactic acid [ 51 ] is influenced by specific strains of bacteria for fermentation and hydrolysis and the availability of agro-wastes as starting materials [ 51 ].

The fungi and bacteria strains adopted for commercial applications include Rhizopus, Pediococcus , and Streptococcus [ 51 ]. The availability of a wide array of bacteria and fungi species has an impact on the material properties biochemical characteristics, morphological, and psychological characteristics of the final product due to the variations in the fermentation processes that lead to the production of fermentable sugars such as starch and cellulose.

Apart from the utilization of different strains of bacteria, the material properties of the PLA- and lactic acid-based polymers are influenced by the pre-treatment methods cold and thermal that are primarily used to remove undesired materials. The fermentation process results in the formation of lactic acid, which is polymerized to form PLA. Biopolymers that are synthesized from agricultural wastes have a tensile strength of The high tensile strength and melting point show that the polymers are suitable for packaging applications and agricultural shading.

Merlot grape pomace fruit waste is the main form of winery agro-waste. In place of decomposition, the winery agro-wastes are a suitable source of composites that are manufactured through solvent extraction SE methods, and pressurized liquid extraction PLE.

The extracts drawn from PLE and SE methods are mixed with commercial-grade polyhydroxyalkanoate to form the matrix. The final phase of the production involves mixing the biopolymer with the poly 3-hydroxybutyratecohydroxy valerate PHBV —a copolyester containing hydroxyaleric acid to form active bio-composites [ 52 ].

The bio-composites have higher or higher than normal tensile strength compared to the virgin biopolymers or the matrix in isolation. The data presented in Table 3 and Table 4 show that the highest mechanical strength was reported in the virgin PHBV matrix.

The inclusion of the bio-based materials extracted via solvent extraction resulted in a reduction in the tensile strength and a marginal improvement in the elongation at break. Mechanical properties and optical properties of microbial synthesized starch films [ 57 ]. Comparative analysis of the mechanical properties of plant-based and petro-chemical based polymers [ 11 ].

Beyond grape pomace, sugar beet agro-wastes are practical sources of bio-composites owing to the presence of carbocal in the dried pulp [ 53 ]. The mechanical properties of the Carbocal are enhanced through the formation of an LLDPE-carbocal biopolymer, via mixing, sieving, drying, and injection mounding. There were limited necking and plastic deformation.

Biodegradable polymers are also generated by the activity of microorganisms such as Gram-negative and Gram-positive bacteria in the presence of carbon-rich materials such as agro-wastes. The bacterial production of the polymers is triggered by pH changes, limited availability of essential nutrients such as phosphorous and nitrogen [ 16 ], the composition and type of culture, and media [ 54 ]. The naturally occurring biopolymers act as biological storage systems or defense mechanisms.

Microalgae are critical to the biological storage processes that result in the development of biopolymers, through biological carbon fixation via photosynthesis. The process culminates in the formation of branched polysaccharides. PHA is the leading bio-based biopolymer that is synthesized from microbes. The synthesis of bio-based polymers from rice bran is catalyzed by the microbial activity of Sinorhizobium meliloti MTCC bacteria.

These bacteria are preferred compared to other species and synthetic methods because they do not pose a threat to the environment and generate significant quantities of agro-wastes [ 55 ]. The rate of production was augmented by the optimization of the incubation period and the addition of rice bran hydrolysate RBH at predefined intervals in the fermentation process. Other microbes, such as white rot fungi, help in the natural de-lignification of agro-wastes [ 54 ]. Microbial synthesis methods have also proven effective in the production of poly b-hydroxybutyric acid PHB —a biodegradable and high strength PHA biopolymer [ 56 ].

The bacterial synthesis of the biopolymer is dependent on the availability of a carbon-rich precursor that is utilized by the bacteria as a source of food and energy. In contrast to other microbial synthesized biopolymers, PHB is suitable for high strength applications because it has mechanical properties that are nearly identical to petroleum-based biopolymers such as PP [ 56 ].

The primary constraint is the cost, which is nine-fold higher compared to other biopolymers. The cost is attributed to the market price of the carbon-rich starting materials. This family of materials is compostable. The main applications are for the production of mulch films, shopping bags, food packaging yogurts , nappies and personal hygiene products Facco and Bastioli, In Europe, hundreds of cities use Mater-Bi bags for the collection of organic waste Bastioli, A polyester synthesised from the poly-condensation of 1,4-butanediol and a mixture of adipic and succinic acids has been blended with wheat starch by Lim Nolan-ITU Pty Ltd, The blends were found to have melting points near that of the polyester alone.

Plasticisers were also added to the starch to improve flexibility and processability of the blend. The modified blends were found to retain a high tensile strength and elongation, even at high starch concentrations.

Bioplast Biotec, Germany Bioplast grades are formulated for injection, blowing injection and flat extrusion. These grades are blends of starch and polycaprolactone. They are moisture sensitive. These blends have been developed for biodegradable film applications like lawn and leaf collection compost bags, agricultural mulch film, etc. Properties are comparable to LDPE films and better than pure polycaprolactone film. It is mainly intended for the production of trash bags and films.

The material is resistant to oils and greases and can be printed by flexography or by offset without corona surface pre-treatment. Applications are short-life products, film coating for foamed starch and fibre trays and as a substitute for food wrapping paper, packaging, etc. Biotec, undated. Cellulose and cellulose derivative For industrial applications, cellulose comes mainly from wood and in small proportions from stalks of sugar cane bagasse dry pulp after juice extraction in sugar cane.

Raw cellulose is a cheap material costing 0. The main uses of cellulose are for paper, membranes, dietary fibres, explosives and textiles. Figure 1. The strong glucosidic bonds ensure the stability of the cellulose in various media. Cellulose is generally insoluble and highly crystalline.

Chemical reactions such as etherification and esterification are conducted on the free hydroxyl groups to Classification of biodegradable polymers 9 1. Numerous derivatives are commercialised such as cellulose acetate, ethyl cellulose, hydroxyl ethyl cellulose, hydroxyl propyl cellulose, hydroxyl alkyl cellulose, carboxy methyl cellulose, fatty acid esters of cellulose Chiellini et al.

Bio-Compo Mitsufuku, Japan This material is made from cellulose powder and is suitable for thermoforming. The main applications are found in horticulture.

Cellophane Cellophane films are obtained by dissolution of cellulose in a sodium hydroxide and carbon disulphide solution Xanthation and than by recasting in a sulphuric acid bath. The aspect is brilliant and transparent. Degradation takes place after six weeks of composting. Cellophane films are mainly used in food packaging where they are appreciated for their barrier properties against micro-organisms, gases and smells.

The other main properties are resistance to infra-red light, oil, heat and transparency to the microwave. Labels are easy to stick on cellophane which is also printable. Cellulose acetate is mainly used in the synthesis of membranes for reverse osmosis. It is produced from cotton linter or from wood pulp. The modified cellulose is mixed with a colourant, a stabiliser, a natural plasticiser catalysing the biodegradation. This product is transparent and can be injected, extruded or blown depending on the grade type.

It can also be recycled or incinerated. The applications are 10 Biodegradable polymers for industrial applications 1. Biocellat comes from the same family of material. EnviroPlastic Z Planet Polymer Technologies, USA This is made from modified cellulose acetate by using a high temperature process which improves the biodegradability of the material.

The composting duration is low about one or two years. This product can be injected or film extruded for packaging applications. Celgreen Daicel Chemical Industries, Japan Daicel commercialises various biopolymers using this label. The grade P-CA is produced with cellulose acetate. Lignin and wood powder blends Lignin is one of the main constituents of wood. It is a very stable and complex product, insoluble in water and resistant to a number of physical and chemical treatments.

The composition of lignin slightly changes from one plant species to another and is a function of the growing conditions but it is always a threedimensional biopolymer composed of three different units of the phenyl propane family: p-hydroxy phenyl, Guaiacyl and syringic aldehydes Fig.

These units are linked by aliphatic and aromatic carbon bonds and ether bonds. In wood, the lignin is closely associated with cellulose and bound to plant polysaccharides in order to form hemicellulose.

This complex chemistry and polymer architecture is the reason why it is really difficult to isolate and to plasticise lignin by a cheap process Chiellini et al. The usual source of commercial lignin is waste liquor from the wood pulp industry. It contains sodium ligninates or lignin sulfonates. Previously, liquefaction of lignocellulosic products was achieved using several hard treatments. A second treatment used an acidic catalyst Classification of biodegradable polymers 11 1.

Today phenols can be used for the liquefaction of wood and lead to the production of thermosetting materials. Sulphuric, oxalic or phosphoric acids also enhance the liquefaction of wood.

The derivative product is then a kind of novolac based resin which can be used in adhesives, mouldings or fibres. Sugar cane waste is another raw material that can be treated in a hot solution of concentrated acetic acid in hydrochloric acid solution.

After re-concentration, the lignin is then precipitated in warm water and finally recovered by dissolution in acetone. These plastics contain wood powder, starch or lignin. The presence of lignin as a filler in other polymers improves the quality of the biodegradation.

Some of those products are reinforced with flax or hemp. Arboform Tecnaro, Germany Arboform is a thermally treated mixture of lignin, flax and hemp. This product can be injected and presents a good dimensional stability.

Applications are found in car dashboard panels, computer or television frames, GSM housings. Fasal IFA, Austria Fasal products are made with wood waste, corn floor, natural resins and small quantities of a plasticiser, lubricants and a colourant.

It can be processed by injection or extrusion without previous drying. The products look slightly like wood and can be milled, painted, or varnished in the same way as wood. It is in the form of pellets, which can be processed by extrusion or injection. Products look like wood and can be milled. Ecoplast Groen Granulaat, Holland This product is composed of wood powder, starch and a binder. It can be injected or thermoformed. Objects made from this material are composted in six weeks.

Napac Napac, Switzerland Napac results from the transformation of Chinese reeds with a natural binder starch and pine tree resin.

These raw materials can be mixed with a colourant and extruded in pellets. Pellets are then moulded by hot compression. This material is perfectly stable outdoors and is formulated to resist exposure to UV light.

The applications are flower pots, CD boxes, interior car parts and non-food packaging. In both cases, the increase of lignin improves the biodegradation of the product by fungi. New research is being conducted into the idea of modifying lignin polymer using enzymes like peroxydase or laccase. The latter enzyme has now been commercialised by a Danish company, Novo Nordisk, and will certainly promote the commercial appearance of new lignin products.

Chitin and chitosan Chitin is one of the most widespread polysaccharides in nature and is particularly abundant in the cell walls of insect cuticles, of many fungal species and of shellfish or mollusc exoskeletons. The chemical composition of chitin is based on the repetition of the unit 2 acetamidedesoxy-D-glucose or Nacetylglucosamine Flieger et al.

Chitin is composed of a linear chain of acetylglucosamine groups Fig. Most chitins and derivatives are extracted from crab shells, lobsters and shrimps or from the waste of fungi fermentation e.

The -chitin Classification of biodegradable polymers 13 1. It is also better adapted to be transformed by reactions such as acetylation, tosylation, tritylation and acetolysis. The properties of chitosan depend strongly on the molecular characteristics molecular weight and degree of acetylation.

Chitosan is soluble in water and in some organic solvents. The difference between chitin and chitosan is defined by their solubility in a dilute solution of weak acids.

Chitosan dissolves in dilute acetic acid. It presents a unique combination of properties, brought about by its polysaccharide structure, large molecular weight, and a cationic character. Chitin and chitosan are biocompatible and present antithrombogenic and hemostatic properties. These polymers can be extruded to make films for packaging applications.

They are edible and can be used in the agricultural crop protection and food sectors, and also in wastewater treatment, textiles or cosmetics and toiletries. They are also used for biomedical applications biomedical devices, and drug delivery systems. Chitosan and its derivatives form air permeable films. This property facilitates cell regeneration when the films are used to protect tissues against microbiological attack.

For this reason chitin and chitosan are also good candidates for artificial skin, and biodegradable sutures. Producers of chitine and chitosan will not be presented here because there are 63 main companies; 30 are located in Asia, 14 in the USA, 12 in Europe, 6 in Canada, and one in Russia.

They are degraded by enzymes proteases. The first industrial applications of protein as polymer were in the early s and s with casein and with soy protein. Even though protein biopolymers did not develop as quickly as starch derivates, they remained present in some niche markets such as encapsulates pharmaceutical , coatings food industry , adhesives or surfactants Guilbert, They can be classified with animal proteins casein, whey, keratin, collagen and gelatine and in plant proteins wheat, corn, soy, pea and potato proteins Chiellini et al.

Collagen and gelatine Collagen and gelatine represent the most well-known animal polymers. Collagen is a relatively non-extensible protein presenting good stiffness.

Gelatine derives from the physical and chemical denaturising of collagen. The good quality of gelatine depends on its high solubility in hot water, its polyampholite character and its intrinsic ability to form thermally reversible gels. Gelatine grades are also available in a wide range of viscosities. The classical applications are for the manufacturing of pharmaceutical products drug caps , for X-rays, photographic film development and food processing.

As a biocompatible material, gelatine displays several advantages. It does not show antigenity and is resorbable in vivo. Its physico-chemical properties can be suitably modulated. Gelatine can be plasticised thanks to the addition of water or of glycerol. There is, however, a limit to the use of this interesting material because there is a risk of viral animal contamination.

Finally blends of polyvinyl alcohol and gelatine are the object of studies and researches. Casein Casein is a natural polymer extracted from skim milk proteins. It represents a small but important percentage of all the natural polymers used for the manufacturing of water-based adhesives. The casein formulations are highly soluble in alkaline solutions and in water. Casein polymers modified or not are mainly used in the manufacture of adhesives and the packaging industry for breweries, wineries and refrigerated products.

Casein is also a binder for paints and an additive for adhesives formulations. It can also be used as a plasticiser for concrete. Beyer Richard demonstrated the feasibility of preparing casein polymer to make edible films and for food products containing this polymer. Classification of biodegradable polymers 15 Wheat and corn gluten Polymers made from gluten are flexible, resistant, transparent, and completely biodegradable.

They are thermoplastic and present a yellow or slightly brown look. They are relatively impermeable to oxygen and to CO2 but are sensitive to humidity and do not give protection against desiccation. Potential applications are the production of soluble pockets for the controlled release of a chemical product e. The world-wide production of wheat gluten is about , tons per year. Moreover, as an edible material, gluten is a good candidate for food packaging or single units of coffee or other food.

In , Henry Ford presented a car body made from soybean-based materials. Soy proteins allow the development of various biodegradable materials.

They are mainly formaldehyde-based thermoset composites. Water resistance can be improved by adding polyphosphate fillers Otaigbe and Adams, Many applications have been developed thanks to its very high Young's modulus. A grade has also been formulated for medical applications. The plasticiser is the glycerol and aminopropyltriethoxi silane is used as coupling agent. In India, many studies have been undertaken into the production of coextruded films of soy proteins with an aliphatic polyester.

The research goal is to decrease the brittle character of the material. Polypeptides of aspartic acid and lysine The wetting level of these polypeptide polymers in water is very high. They are now commercialised by Mitsui Chemical for horticultural applications.

Some of these oily products are already well known by the public from their use in paint e. Plant oils increasingly become a source of raw material to produce thermoset resins that can be mixed with natural fibres in order to achieve light and resistant composite materials.

The combination of bio-based resins with natural fibres plant and poultry or 16 Biodegradable polymers for industrial applications 1. These composites are used in agricultural equipment, automotive sheet-moulding compounds SMCs , civil and rail infrastructures, marine applications, housing and the construction industry Wool, The best candidates are triglycerides presenting a high level of unsaturation, and comprising active sites such as double bonds, allylic carbons, ester groups and carbons alpha to the ester group.

By using the same synthetic techniques that have been applied in the synthesis of petrochemical-based polymers, these active sites can be used to introduce polymerisable groups on the triglyceride Fig. Castor oil contains ricinoleic acid presenting a hydroxyl group that allows polymer formation.

This OH group participates in the formation of polyurethane and polyesters. Chemical functionalities such as aromatic or cyclic structures are introduced in the chemical structure of the triglyceride to improve stiffness in the polymer network. The material produced with this kind of resin and reinforced with fibres shows very high mechanical properties e. The chemistry of thermoset resins made from plant oils could be addressed in a separate chapter. In this overview we will simply mention that from plant triglycerides, it is possible to produce polyolefins, polyurethane, polyesters, polyethers or polyamide resins.

These Classification of biodegradable polymers 17 Table 1. Table 1. Generally, a decrease of the length of the aliphatic chain causes a decrease of the melting and glass transition temperatures. These products are easier to process and are more flexible. Most of these polymers are biocompatible and bioresorbable.

This is why numerous applications, generally patented, are in the medical or veterinary sector implants, sutures. Nevertheless, certain companies have developed more usual products. Polyhydroxyalkanoate PHA Polyhydroxyalkanoate is a polyester identified in by the microbiologist Maurice Lemoigne. It can be synthesised by various bacteria Alcaligenes Eutrophus, cyanobacteria.

There are numerous potential applications for PHA cosmetics containers, disposable articles, medical implants, paper coatings. Moreover, PHA can be formulated in many grades, from elastic products to crystalline ones, it is a good candidate for blends and easy to process with traditional equipment Whitehouse, It is naturally not crystalline, and is converted in a more crystalline form during the extraction process. Research has been undertaken to avoid this transformation step that causes a decrease in the mechanical properties.

The properties of PHB are similar to those of polypropylene, except for its biodegradability. It is also more rigid, more brittle and denser than PP. It resists oxidation but presents low chemical resistance. PHB is insoluble in water and relatively resistant to hydrolysis, the opposite of most biopolymers. Pellets are commercialised for classical plastic transformation processes.

The low viscosity of the melted polymers allows the injection of objects with thin walls. Composting duration is about two months.

The originality of the grades is the variation in the nature of the radical of the ester. This company also produces PHA products. Genetically modified plants are also studied for producing PHB. Potential plants are watercress, colza Arabidopsis thaliana , corn and tobacco but yields are very low, just a few percent of the total weight of the vegetable.

This is an advantage found in many other blends of biodegradable plastics. The same fact is observed for blends of poly 3-hydroxybutyrate and polyethylene glycol. This is due to the hydrophilic character of polyethylene glycol. It is now the property of Metabolix.

It is a copolymer of hydroxybutyrate and hydroxyvalerate. This thermoplastic is adapted for injection and blow moulding, fibre and film production. Adaptations of the product for foaming, laminating and thermoforming processes are in development. The antistatic properties of Biopol make it a good candidate for electric and electronic packaging applications. Despite its high degree of crystallinity, Biopol is sensitive to hydrolysis.

Companies e. This last material is an elastomere. Metabolix has transferred the coding genes in Escherichia coli K12 agreed strain by the FDA for the production of food Classification of biodegradable polymers 19 additives. The difference in terminology indicates simply the synthesis method chosen to produce the polymer from lactic acid.

The interest in this material started in the s with the work of Carothers but the molecular weight and the mechanical properties were weak.

In , DuPont patented a PLA presenting higher molecular weight and in , the first co-polymers allowed the production of medical resorbable sutures. PLA comes from the esterification of lactic acid produced by fermentation. The micro-organism can be Lactobacilli, Pediococci or certain fungi such as Rhizopus Oryzae for example.

From lactic acid, there are two pathways to produce PLA. The first one has been developed by Mitsui Toatsu. First of all, the aqueous lactic acid solution is purified and concentrated. Then, the direct condensation and cyclisation reactions are performed at elevated temperatures in the presence of a catalyst. The condensate is removed by distillation.

This process produces a polylactic acid of high molecular weight presenting a broad distribution. The second process is indirect. First, a lactide is produced from two lactic acid molecules by cyclisation and dimerisation. Lactide oligomers can then be polymerised in polylactide.

The dimerisation step is a critical and more expensive pathway. The Cargill Dow process consists in producing a low molecular weight polylactic acid by the first process. Then, the PLA is depolymerised and converted in lactide which is transformed in PLA with a higher and more homogeneous molecular weight distribution.

The properties of PLA change from one producer to another but general properties are resistance to fat, food oil, humidity, solvent and smells. Some grades are really bright and transparent but are also more brittle. PLA can be processed by extrusion, thermoforming, injection, blow moulding, fibre spinning or stretching.

It is printable and heat sealable. The actual or potential applications are found in the crop and food sectors films, food packaging, soft drinks and for non-woven materials in hygienic products.

The properties of biocompatibility and of bioresorption of PLA permits the development of suture threads and clips, orthopaedic fixations screws, pins and of resorbable implants Clarinval, Some of the main products are given below. Cargill has also developed fibres for clothes, hygiene products or carpets. Due to the closed properties and similar applications of the products from Cargill Dow LLC and Mitsui Chemicals, a research and commercial collaboration has been decided between both these giants of PLA production.

Lactron Kanebo Goshen, Japan Lactron are fibres dedicated to the production of nets used in agriculture or for fishing. It exists also as a non-woven product used in hygiene products and this is a medical grade. Solanyl Rodenburg Biopolymers, Holland The production capacity of Rodenburg Polymer is about 8, tonnes per year and 40, tonnes per year has been announced PLA is made here from potatoes.

Grades for injection are commercially available and allow the injection of objects presenting thin walls 0. Another application is for the release of fertiliser rods. Galactic Belgium Pellets are commercialised for the production of films and fibres. Galactic is involved in new application developments. Chemists have mainly worked to decrease its mechanical alteration Classification of biodegradable polymers 21 Table 1. The most studied natural polymer is cis-polyisoprene produced by the rubber tree Hevea Braziliensis.

Nowadays, this molecule is also synthesised by adding polymerisation from isoprene. The main research trends have been directed at inhibiting its degradation by adding, for example, aromatic amines, antioxidants or some other constituents during the vulcanisation process. Composite Blends of two or more biopolymers are not presented here, they are included in the paragraph describing the main constituent of their matrix.

Starch or lignin are often added as a filler. Polyesters represent a large family of polymers having in their structure the potentially hydrolysable ester bond Fig. The polyesters can be classified following the composition of their main chain. There are aliphatic and aromatic polyesters 1. Advanced Search Find a Library. Your list has reached the maximum number of items. Please create a new list with a new name; move some items to a new or existing list; or delete some items.

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Rent this article via DeepDyve. European Bioplastics a Bioplastics facts and figures. Accessed on 01 Mar Government of India Chemical and petrochemicals statistics at a glance. European Commission Plastic waste—strategy and background. FICCI Potential of plastics industry in northern India with special focus on plastic culture and food processing. J Polym Environ 20 2 — Article Google Scholar.

Smith R Biodegradable polymers for industrial applications. Woodhead Publishing, Limited, pp 3—29, —, —, — Exp Polym Lett 3 6 — Carbohyd Polym — Prog Polym Sci — Hernandez-Munoz P, Kanavouras A Development and characterization of biodegradable films made from wheat gluten protein.

J Agric Food Chem 51 26 — Membranes 6 2 Polym Testing — Ahvenainen R Novel food packaging techniques. Wood head Publishing, Limited, Cambridge. Book Google Scholar. Halley P Biodegradable packaging for the food industry. Packag Bottling Int 4 4 — Google Scholar. Blackwell Publishing, Oxford, pp — Packag Technol Sci — European Bioplastics b Biopolymers facts and statistics.

Institute for Bioplastics and Composites. Hochschule Hannover University of Applied sciences and arts. Accessed 27 Jan J Food Sci Technol 46 5 — J Food Sci Technol 46 6 — Baruipur for modified atmosphere packaging.

Int J Food Prop 14 3 — Food Bioproc Technol Int J — Food Eng Rev — Int J Food Prop 14 5 :1— Shahi for preserving quality and extension of shelf-life. Postharvest Biol Technol — Trends Biosci 6 2 — Emir J Food Agric 25 5 — J Food Sci Technol 52 7 — J Food Sci Technol 51 11 — Innov Food Sci Emerg Technol — Robertson GL Food packaging: principles and practice, 3rd edn.

In: Revie W ed The Uhlig corrosion handbook, 2nd edn. Wiley, New York, p Robertson GL Food packaging principles and practice, 2nd edn. In: Chiellini E ed Environmentally compatible food packaging. Woodhead Publishing Ltd, Cambridge, pp 29— Chapter Google Scholar. Polymers — Malathy AN, Santhosh KS, Nidoni U Recent trends of biodegradable polymer: biodegradable films for food packaging and application of nanotechnology in biodegradable food packaging.

Curr Trends Technol Sci — Averous L, Pollet E Environmental silicate nano-biocomposites. Springer, London. Bastioli C Hand book of biodegradable polymers. Rapra Technology Limited, Shropshire. J Food Sci Technol 52 9 —