Natural Polymers: History
View Latest Version
Please note this is an old version of this entry, which may differ significantly from the current revision.
Contributor:
Prabaharan Graceraj Ponnusamy
,
Sudhagar Mani

Repeated and arranged polymer molecular units are present in some animal and plant biomass. They behave as fossil-based polymeric materials and are called natural polymers. The natural polymers that were extracted from different biomass resources are classified based on the resources used. They are present in animals and plants as protein macromolecules of amino acids bonded by peptides or as polysaccharide macromolecules of monosaccharides bonded by glycosidic bonds or as lipid–long chain hydrocarbon molecules containing a carboxylic acid moiety.

  • natural polymers
  • nanocomposites
  • nanocellulose

1. Introduction

Natural polymers are abundantly available in many renewable resources. At present, biomass resources are mainly utilized for the production of various food products, oil, feed grains, bioenergy, and cosmetic products. The production and utilization details of various resources used for the manufacture of natural polymers in the U.S.A. are presented in Table 1.

Table 1. Renewable resources and their production volume in the U.S.A. during the year 2017.
Renewable
Resources		 Natural Polymer Type and Compositions Production
Volume
(Million
Metric Tons)		 Current Use Reference
Milk Contains 33 g of protein/L. 80% casein and 20% whey protein 97.76 Used as a fat substitute. Butter, dry skim milk, cheese, whey, whey protein concentrate, and lactose are produced from milk. [1][2]
Pork & Beef More than 29% gelatin is available in pig skin. In beef meat, 10.6~21.9% of gelatin protein available in rib and shank 11.91 Used as meat. By-products such as skin, bones, and connective tissues are used to produce gelatin [2][3]
Wheat Contains 76.5% starch 47.38 Used for the production of food products [2][4]
Soybeans Contains 31.7 to 58.9% protein 120.07 Source for animal protein and vegetable oil [2][5]
Corn grain Contains about 70–72% starch 371.10 Source for corn meal, starch, oil, bioethanol, syrup, sugar, and feed grain [2][6]
Potato Contains 20% of potato dry matter with 60–80% of starch 22.91 Source for food products and starch [2][7]
Crustaceans (Shrimp and Crab) Crab shell contains 9.6% chitin and shrimp shell contains 4% chitin 0.32 Source for seafood and compost [8][9]
Forestry biomass resources 40~50% cellulose 139.71 Biofuels, wood products such as timber, lumber, etc. [10][11]
Agricultural biomass resources 25~40% cellulose 130.64 Source for bioenergy, biofuels, and bioproducts [10][11]
Waste (Agricultural wastes, forestry wastes) 25~50% cellulose 61.69 Source for compost, bioenergy [10][11]

2. Protein-Based Natural Polymers

2.1. Proteins-Based Natural Polymers from an Animal Resource

Milk is a colloidal solution constituted of fat, minerals, vitamins, and a heterogeneous mixture of the proteins casein (80%) and whey (20%). Flexible and transparent films were produced from casein and whey proteins present in the milk. The whey proteins are the aggregate of soluble globular proteins in serum albumin [12]. The casein proteins contain four forms of protein, namely, αs1, αs2, β, and κ casein (Figure 1) [13]. The whey and casein proteins are polymerized from milk by acidification and heat treatment processes and are separated by micro- and ultra-filtration techniques [14][15]. The protein molecules tend to form films due to bonding and electrostatic interaction. The film and coating properties of casein are determined from the calcium micelles formed by the hydrophobic and electrostatic interactions of protein molecules and calcium bridging elements [16]. As the native milk protein films are brittle, plasticizers were added to weaken the bonding between protein chains. The crosslinking agents and plasticizers enhanced the mechanical and physical properties of the films [17][18].
Polymers 14 04033 g002 550
Figure 1. Casein polymer structure.
Collagen is the most abundant (about 25%) protein which is present in the cell walls of vertebrates and invertebrates [19][20]. Gelatin proteins are extracted from collagen by acetic acid hydrolysis (Figure 2). It exhibits good solubility in water. The gelatin proteins are a mixture of long and short amino acids connected by peptide bonds. The amino acid sequences determine the polymer structure and the properties of protein polymer [21]. Gelatin-based edible films and coatings were developed to use in food packaging. A gelatin polymer from fish skin was extracted with an acid-and-base treatment [22]. The improvement in the physical and mechanical properties of gelatin-based films was observed with the addition of antimicrobial, antioxidant, and lipid agents. The gelatin films and coatings were produced by dip coating, casting, and extruding [23].
Polymers 14 04033 g003 550
Figure 2. A change in collagen polymer structure during hydrolysis.
Sericin is a protein extracted from silk fibers by a degumming process using boiled water. Sericin has different amino acids such as serine, glycine, glutamate, and threonine [24]. The carboxyl, amino, and hydroxyl groups are the major polar groups present in this protein. These polar groups are reactive elements that enable crosslinking between molecular chains. As the standalone film-forming characteristics of sericin are not good, it is used with other polymers to make packaging film and coatings [25][26].
The animal proteins have good film-forming abilities, with poor tensile and water vapor barrier properties. Crosslinking and plasticizers were used to increase the tensile strength of the films. They were found suitable for edible coating and films. The water vapor transmission was increased by 100% with increased pore size by crosslinking [27]. The mechanical and barrier properties of animal protein-based natural polymers are presented in Table 2.
Table 2. Tensile and barrier properties of animal protein films.
Natural Polymer Plasticizer/
Crosslinker		 TS a
(MPa)		 YM b
(MPa)		 Elongation at Break
(%)		 Tensile Test Conditions WVP c
× 1020
(g m h−1 kPa−1 m−2)		 Reference
αs1—Casein Films -- 0.004 -- 38 Film size 20 × 50 mm. Loading Rate—50 mm/min -- [28]
αs1—Casein Films Transglutaminase (Enzyme) 0.01 -- 75   --
α, β and κ—Casein Films f -- 52 ± 0.20 1107 ± 11 8 ± 2 Loading rate—20 mm/min d -- [29]
α, β and κ—Casein Films g -- 49 ± 3 1391 ± 48 6 ± 2 --
α, β and κ—Casein Films h 10% Glycerol 36 ± 0.40 693 ± 38 25 ± 9 --
α, β and κ—Casein Films i 10% Glycerol 21 ± 0.30 497 ± 40 17 ± 1 --
α, β and κ—Casein Films j 10% Glycerol 33 ± 2 765 ± 109 15 ± 7 --
α, β and κ—Casein Films k 10% Glycerol 48 ± 2 1004 ± 40 8 ± 3 --
Whey Protein Films 40% Sorbitol 18 650 5 Loading rate—100 mm/min d -- [30]
Whey Protein Films 15% Glycerol 29 1100 4   --
Fish Gelatin Films l 10 wt.% glycerol 36.52 ± 2.98   1.79 ± 0.54 Sample size 4.75 × 22.25 mm e 5.33 ± 0.16 [22]
Fish Gelatin Films m 10 wt.% glycerol 43.02 ± 0.52   2.31 ± 0.33   5.47 ± 0.10
Fish Gelatin Films n 10 wt.% glycerol 52.36 ± 3.16   2.88 ± 0.68   6.52 ± 0.16

a TS—Tensile strength. b YM—Young’s modulus. c ASTM test for water vapor permeability—E96-95. d ASTM test for tensile strength—D882. e ASTM test for tensile strength—D1708-93. f Casein in NaOH/H2O solution and Heat treated at 130 °C/18 h. g Casein in 3-aminopropyl triethoxy silane solution—Heat treated at 130 °C/18 h. h Casein in NaOH/H2O solution- Air dried. i Casein in NaOH/H2O solution—Heat treated at 130 °C/18 h. j Casein in 3-aminopropyl triethoxy silane solution- Heat treated at 130 °C/18 h. k Casein in 3-aminopropyl triethoxy silane solution- Air dried. l Gelatin solution without pH modification. m Gelatin solution with HCl acid modified pH (2.0). n Gelatin solution with NaOH base modified pH (10.0).

2.2. Protein-Based Natural Polymers from Plant Resources

Wheat grains have starch, lipids, and gluten proteins. The gluten proteins are constituted with high contents of gliadins and glutenin bonded by disulfide, hydrogen, and ionic and hydrophobic bonds. These proteins are especially characterized by their protein molecular weights and are extracted from wheat by treatment with ethanol [31][32]. Gluten-based films for packaging applications were developed with plasticizers such as glycerol and sorbitol for the improvement of tensile properties. The tensile strength of gluten-based films is less than that of polyethylene-based materials, although the percentage of elongation is comparable with polyethylene-based materials [33][34].
Soy protein isolate (SPI), which contains 92%, protein, is extracted from soybean by removing fats, carbohydrates, fibers, and moisture. The SPI is a mixture of albumins and globulins proteins with many functional groups such as carboxyl, amine, and hydroxyls. SPI is extracted from de-fatted soy flakes by treating with either water or mild alkali (pH 7–9) at 50–55 °C and precipitated by adjusting the pH to ∼4.5 with food-grade acid [35]. The tensile properties of SPI materials were modified with plasticizer and formed into films by casting or melt processing.
Zein protein is extracted from corn by treating it with aqueous ethanol extract and a dry milling process. It contains mostly α-zein, which can self-assemble into a microstructure to form a film or coating [36][37][38]. The films formed with native zein proteins are brittle and sensitive to high relative humidity.
The plant-based protein natural polymers exhibited excellent film-forming abilities. Their brittle nature and poor resistance to moisture absorbance are the limiting factors that prevent them from being considered for packaging applications. The summary of mechanical and barrier properties of plant protein-based natural polymers is listed in Table 3.
Table 3. Tensile and barrier properties of plant protein films.
Natural Polymer Plasticizer/Crosslinker TS a
(MPa)		 YM b
(MPa)		 Elongation at Break
(%)		 Tensile Test Conditions c WVP d
(g m h−1 kPa−1 m−2)		 Reference
Glutenin-rich Wheat Gluten Film 20% Glycerol 5 -- 100 Sample Size: 2.54 × 10 cm. Loading rate: 508 mm/min 6.94 × 104 [39]
Gliadin-rich Wheat Gluten Film 20% Glycerol 15 -- 350 -- 1.11 × 105
SPI Film 50% Glycerin 2.80 ± 0.30 -- 165.70 ± 15 Film size: 2.54 × 15 cm 9.66 × 10−9 [40]
Zein Film -- 6.70 ± 0.37 409.86 ± 7.62 1.96 ± 0.18 Film size: 40 × 10 × 0.47 ± 0.12 mm 1.69 × 10−4 [41]
Zein Film 10% Tributyl Citrate 17.80 ± 4.26 556.29 ± 29.42 4.53 ± 0.54   1.64 × 10−4

a TS—Tensile strength. b YM—Young’s Modulus. c Films conditioned in a chamber at 23 °C and 50% RH for at least 48 h. d ASTM test method for Water vapor permeability—E96-95.

3. Polysaccharide-Based Natural Polymers

3.1. Polysaccharide-Based Natural Polymers from an Animal Resource

Chitin is a polysaccharide extracted from crab and shrimp shells by demineralization and deproteination processes as shown in Figure 3a. The monosaccharide units of chitin have an acetyl amine group (-CH3-CO-NH) and are linked by β-(1 → 4) covalent bonds [42]. The acetyl amine group present in the chitin causes strong hydrogen bonding between adjacent polymers. The antibacterial and antifungal properties and abundant availability of chitin attracted food packaging applications [43][44][45]. The tensile strength of around 18 MPa and the percentage of elongation of 6% were achievable for films manufactured from chitin natural polymer by film casting [46].
Polymers 14 04033 g004 550
Figure 3. The production of polysaccharide natural polymers (a) Chitosan (b) Starch (c) Cellulose Nanofibrils (CNF).
Chitosan is the natural polymer manufactured from chitin by deacetylation with base agents as shown in Figure 3a. They are available in a different range of molecular weights and degrees of deacetylation. The primary functional groups available in these polymers are hydroxyl (OH), amine (NH2), and ether (C-O-C) [47]. The presence of amino groups makes chitosan a positively charged polysaccharide. Chitosan is not soluble in water but is soluble in weak acidic solutions. To develop chitosan as packaging materials, hydrophilic properties attributed to hydroxyl groups were improved by crosslinking, and the elongation at break was improved by blending with plasticizer [48]. The tensile strength and percentage of elongation at the break of the chitosan films modified by citric acid crosslinking were around 13 and 48 MPa, respectively [49].

3.2. Polysaccharide-Based Natural Polymers from Plant Resource

Thermoplastic starch (TPS) is a polysaccharide polymer that is extracted from biomass such as corn, wheat, rice, potato, cassava root, barley, and oat as shown in Figure 3b. The structure of TPS is constituted of amylose and amylopectin macromolecules [50]. The tensile strength and percentage of elongation of native starch are 5 and 50 MPa, respectively [51]. Thermoplastic starch plasticized by polyols was investigated to use as an edible coating and packaging film. Tensile strengths of 10 to 30 MPa and percentages of elongation at break of 3 to 60% were obtained with 20 to 30% glycerol as a plasticizer in packaging film production with starch biopolymers [52][53].
Cellulose is an extract from plants and is the most abundant material on earth. It forms a polymeric structure with β-D-glucopyranose units having reactive hydroxyl groups in C2, C3, and C6 and linked by a covalent bond with acetal groups in C4 and C1 [54]. They are widely extracted from wood and plant biomass resources as shown in Figure 3c. The adjacent cellulose molecules form hydrogen bonds and make rigid structures during the film-forming process. The films with microcellulose fibrils showed 80 MPa tensile strength [55]. The nanocellulose films manufactured from different resources and different extraction processes exhibited distinct tensile properties. The softwood nanocellulose films manufactured by the tempo oxidation method had a tensile strength of 82 MPa and percentage elongation at a break of 1 [56].

4. Lipid-Based Natural Polymers

Wax-based natural polymers are used as edible films and coating [57]. The wax polymers constitute majorly long chain hydrocarbons and esters. They are insoluble in water but soluble in organic solvents. The temperature dependence of wax-based film is a limiting factor in using these films in packaging applications [58]. Similarly, the use of lacquers in packaging applications is limited to coatings on metallic surfaces to avoid harmful elements in packaging materials [59][60][61]. The hydroxyl groups of acetylated fatty acids were modified to enable crosslinking between molecules to increase the tensile strength of the coating. The tensile strength of these films was found to be 1.76 MPa [62][63].

This entry is adapted from the peer-reviewed paper 10.3390/polym14194033

References

  1. Khwaldia, K.; Perez, C.; Banon, S.; Desobry, S.; Hardy, J. Milk proteins for edible films and coatings. Crit. Rev. Food Sci. Nutr. 2004, 44, 239–251.
  2. U.S. Department of Agriculture, E.R.S. Available online: https://www.ers.usda.gov/data-products/ (accessed on 18 September 2022).
  3. Mitchell, H.H.; Zimmerman, R.L.; Hamilton, T.S. Determination of the amount of connective tissue in meat. J. Anim. Sci. 1927, 1927, 257.
  4. Domenek, S.; Feuilloley, P.; Gratraud, J.; Morel, M.H.; Guilbert, S. Biodegradability of wheat gluten based bioplastics. Chemosphere 2004, 54, 551–559.
  5. Wang, J.; Chen, P.; Wang, D.; Shannon, G.; Zeng, A.; Orazaly, M.; Wu, C. Identification and mapping of stable QTL for protein content in soybean seeds. Mol. Breed. 2015, 35, 1–10.
  6. Rouf Shah, T.; Prasad, K.; Kumar, P. Maize—A potential source of human nutrition and health: A review. Cogent Food Agric. 2016, 2, 1166995.
  7. Robertson, T.M.; Alzaabi, A.Z.; Robertson, M.D.; Fielding, B.A. Starchy carbohydrates in a healthy diet: The role of the humble potato. Nutrients 2018, 10, 1764.
  8. Muñoz, I.; Rodríguez, C.; Gillet, D.; Moerschbacher, B.M. Life cycle assessment of chitosan production in India and Europe. Int. J. Life Cycle Assess. 2018, 23, 1151–1160.
  9. Lowther, A.; Liddel, M.; Yencho, M. Fisheries of the United States 2018: Current Fishery Statistics no. 2018; National Oceanic and Atmospheric Administration: Silver Spring, MD, USA, 2020.
  10. Wang, S.; Dai, G.; Yang, H.; Luo, Z. Lignocellulosic biomass pyrolysis mechanism: A state-of-the-art review. Prog. Energy Combust. Sci. 2017, 62, 33–86.
  11. Langholtz, M.; Stokes, B.; Eaton, L. 2016 Billion-ton report: Advancing domestic resources for a thriving bioeconomy (executive summary). Ind. Biotechnol. 2016, 12, 282–289.
  12. Chen, H. Functional properties and applications of edible films made of milk proteins. J. Dairy Sci. 1995, 78, 2563–2583.
  13. Dalgleish, D. Milk proteins. Chemistry and physics. In Food Proteins; Fox, P.F., Condon, J.J., Eds.; Applied Science Publishers: London, UK, 1982; pp. 155–178.
  14. Metzger, W. Method of Producing Casein Film. U.S. Patent No. 5,681,517, 28 October 1997.
  15. Patel, S. Emerging trends in nutraceutical applications of whey protein and its derivatives. J. Food Sci. Technol. 2015, 52, 6847–6858.
  16. Horne, D.S. Casein structure, self-assembly and gelation. Curr. Opin. Colloid Interface Sci. 2002, 7, 456–461.
  17. Sothornvit, R.; Krochta, J.M. Plasticizer effect on mechanical properties of β-lactoglobulin films. J. Food Eng. 2001, 50, 149–155.
  18. Hristov, P.; Mitkov, I.; Sirakova, D.; Mehandgiiski, I.; Radoslavov, G. Measurement of casein micelle size in raw dairy cattle milk by dynamic light scattering. In Milk Proteins–From Structure to Biological Properties and Health Aspects; Intech: Rijeka, Croatia, 2016.
  19. Sibilla, S.; Godfrey, M.; Brewer, S.; Budh-Raja, A.; Genovese, L. An overview of the beneficial effects of hydrolysed collagen as a nutraceutical on skin properties: Scientific background and clinical studies. Open Nutraceuticals J. 2015, 8, 29–42.
  20. Schmidt, M.M.; Dornelles, R.C.P.; Mello, R.O.; Kubota, E.H.; Mazutti, M.A.; Kempka, A.P.; Demiate, I.M. Collagen extraction process. Int. Food Res. J. 2016, 23, 913–922.
  21. Bigi, A.; Panzavolta, S.; Rubini, K. Relationship between triple-helix content and mechanical properties of gelatin films. Biomaterials 2004, 25, 5675–5680.
  22. Etxabide, A.; Leceta, I.; Cabezudo, S.; Guerrero, P.; de la Caba, K. Sustainable fish gelatin films: From food processing waste to compost. ACS Sustain. Chem. Eng. 2016, 4, 4626–4634.
  23. Ramos, M.; Valdés, A.; Beltran, A.; Garrigós, M.C. Gelatin-based films and coatings for food packaging applications. Coatings 2016, 6, 41.
  24. Dash, R.; Mukherjee, S.; Kundu, S. Isolation, purification and characterization of silk protein sericin from cocoon peduncles of tropical tasar silkworm, Antheraea mylitta. Int. J. Biol. Macromol. 2006, 38, 255–258.
  25. Sothornvit, R.; Chollakup, R.; Potjanart, S. Extracted sericin from silk waste for film formation. Songklanakarin J. Sci. Technol. 2010, 32, 17–22.
  26. Zhang, Y.-Q. Applications of natural silk protein sericin in biomaterials. Biotechnol. Adv. 2002, 20, 91–100.
  27. Yildirim, M.; Hettiarachchy, N.S. Properties of films produced by cross-linking whey proteins and 11s globulin using transglutaminase. J. Food Sci. 1998, 63, 248–252.
  28. Motoki, M.; Aso, H.; Seguro, K.; Nio, N. ALPHA.s1-Casein film prepared using transglutaminase. Agric. Biol. Chem. 1987, 51, 993–996.
  29. Ghosh, A.; Ali, M.A.; Dias, G.J. Effect of cross-linking on microstructure and physical performance of casein protein. Biomacromolecules 2009, 10, 1681–1688.
  30. McHugh, T.H.; Krochta, J.M. Sorbitol- vs glycerol-plasticized whey protein edible films: Integrated oxygen permeability and tensile property evaluation. J. Agric. Food Chem. 1994, 42, 841–845.
  31. Wieser, H. Chemistry of gluten proteins. Food Microbiol. 2007, 24, 115–119.
  32. Shewry, P.R.; Tatham, A.S.; Forde, J.; Kreis, M.; Miflin, B.J. The classification and nomenclature of wheat gluten proteins: A reassessment. J. Cereal Sci. 1986, 4, 97–106.
  33. Mojumdar, S.C.; Moresoli, C.; Simon, L.C.; Legge, R.L. Edible wheat gluten (WG) protein films. J. Therm. Anal. Calorim. 2011, 104, 929–936.
  34. Micard, V.; Belamri, R.; Morel, M.H.; Guilbert, S. Properties of chemically and physically treated wheat gluten films. J. Agric. Food Chem. 2000, 48, 2948–2953.
  35. Ma, C.Y. Soybean|soy concentrates and isolates. In Reference Module in Food Science; Elsevier: Amsterdam, The Netherlands, 2015.
  36. Wang, Y.; Padua, G.W. Nanoscale characterization of zein self-assembly. Langmuir 2012, 28, 2429–2435.
  37. Paraman, I.; Lamsal, B.P. Recovery and characterization of α-zein from corn fermentation coproducts. J. Agric. Food Chem. 2011, 59, 3071–3077.
  38. Parris, N.; Dickey, L.C. Extraction and solubility characteristics of zein proteins from dry-milled corn. J. Agric. Food Chem. 2001, 49, 3757–3760.
  39. Hernández-Muñoz, P.; Kanavouras, A.; Ng, P.K.; Gavara, R. Development and characterization of biodegradable films made from wheat gluten protein fractions. J. Agric. Food Chem. 2003, 51, 7647–7654.
  40. Rhim, J.-W.; Lee, J.H.; Ng, P.K.W. Mechanical and barrier properties of biodegradable soy protein isolate-based films coated with polylactic acid. LWT—Food Sci. Technol. 2007, 40, 232–238.
  41. Shi, K.; Yu, H.; Lakshmana Rao, S.; Lee, T.C. Improved mechanical property and water resistance of zein films by plasticization with tributyl citrate. J. Agric. Food Chem. 2012, 60, 5988–5993.
  42. Kurita, K. Chitin and Chitosan: Functional biopolymers from marine crustaceans. Mar. Biotechnol. 2006, 8, 203.
  43. Kabalak, M.; Aracagök, D.; Torun, M. Extraction, characterization and comparison of chitins from large bodied four Coleoptera and Orthoptera species. Int. J. Biol. Macromol. 2019, 145, 402–409.
  44. Aranday-García, R.; Saimoto, H.; Shirai, K.; Ifuku, S. Chitin biological extraction from shrimp wastes and its fibrillation for elastic nanofiber sheets preparation. Carbohydr. Polym. 2019, 213, 112–120.
  45. Agbaje, O.B.A.; Shir, I.B.; Zax, D.B.; Schmidt, A.; Jacob, D.E. Biomacromolecules within bivalve shells: Is chitin abundant? Acta Biomater. 2018, 80, 176–187.
  46. King, C.; Shamshina, J.L.; Gurau, G.; Berton, P.; Khan, N.F.A.F.; Rogers, R.D. A platform for more sustainable chitin films from an ionic liquid process. Green Chem. 2016, 19, 117–126.
  47. Madeleine-Perdrillat, C.; Karbowiak, T.; Raya, J.; Gougeon, R.; Bodart, P.R.; Debeaufort, F. Water-induced local ordering of chitosan polymer chains in thin layer films. Carbohydr. Polym. 2015, 118, 107–114.
  48. Ma, X.; Qiao, C.; Wang, X.; Yao, J.; Xu, J. Structural characterization and properties of polyols plasticized chitosan films. Int. J. Biol. Macromol. 2019, 135, 240–245.
  49. Guerrero, P.; Muxika, A.; Zarandona, I.; De La Caba, K. Crosslinking of chitosan films processed by compression molding. Carbohydr. Polym. 2019, 206, 820–826.
  50. Lörcks, J. Properties and applications of compostable starch-based plastic material. Polym. Degrad. Stab. 1998, 59, 245–249.
  51. Zhang, Y.; Rempel, C.; McLaren, D. Chapter 16—Thermoplastic starch. In Innovations in Food Packaging, 2nd ed.; Han, J.H., Ed.; Academic Press: San Diego, CA, USA, 2014; pp. 391–412.
  52. Talja, R.A.; Helén, H.; Roos, Y.H.; Jouppila, K. Effect of various polyols and polyol contents on physical and mechanical properties of potato starch-based films. Carbohydr. Polym. 2007, 67, 288–295.
  53. Jimenez, A.; Fabra, M.J.; Talens, P.; Chiralt, A. Edible and biodegradable starch films: A review. Food Bioprocess Technol. 2012, 5, 2058–2076.
  54. O’Sullivan, A.C. Cellulose: The structure slowly unravels. Cellulose 1997, 4, 173–207.
  55. Spence, K.L.; Venditti, R.A.; Habibi, Y.; Rojas, O.J.; Pawlak, J.J. The effect of chemical composition on microfibrillar cellulose films from wood pulps: Mechanical processing and physical properties. Bioresour. Technol. 2010, 101, 5961–5968.
  56. Zhao, Y.; Moser, C.; Lindström, M.E.; Henriksson, G.; Li, J. Cellulose nanofibers from softwood, hardwood, and tunicate: Preparation–structure–film performance interrelation. ACS Appl. Mater. Interfaces 2017, 9, 13508–13519.
  57. Saucedo-Pompa, S.; Rojas-Molina, R.; Aguilera-Carbó, A.F.; Saenz-Galindo, A.; de La Garza, H.; Jasso-Cantú, D.; Aguilar, C.N. Edible film based on candelilla wax to improve the shelf life and quality of avocado. Food Res. Int. 2009, 42, 511–515.
  58. Donhowe, G.; Fennema, O. Water vapor and oxygen permeability of wax films. J. Am. Oil Chem. Soc. 1993, 70, 867–873.
  59. Melvin, C.; Jewell, E.; de Vooys, A.; Lammers, K.; Murray, N.M. Surface and adhesion characteristics of current and next generation steel packaging materials. J. Packag. Technol. Res. 2018, 2, 93–103.
  60. Grassino, A.; Pezzani, A.; Squitieri, G. Characterisation of different types of lacquers used in food packaging: Lacquer adhesion tests. Acta Aliment. —Acta Aliment. 2007, 36, 27–37.
  61. Allman, A.; Jewell, E.; de Vooys, A.; Hayes, R. Inter-layer adhesion performance of steel packaging materials for food cans under retort conditions. J. Packag. Technol. Res. 2018, 2, 115–124.
  62. Zuo, H.; Cao, Z.; Shu, J.; Xu, D.; Zhong, J.; Zhao, J.; Wang, T.; Chen, Y.; Gao, F.; Shen, L. Effect of structure on the properties of ambient-cured coating films prepared via a Michael addition reaction based on an acetoacetate-modified castor oil prepared by thiol-ene coupling. Prog. Org. Coat. 2019, 135, 27–33.
  63. Ruiz, M.M.; Schroeder, W.F.; Hoppe, C.E. The use of a fatty acid/β-Hydroxyester blend to enhance the surface hydrophilicity of crosslinked poly(ethylene glycol) coatings. Prog. Org. Coat. 2019, 135, 313–320.
More
© Text is available under the terms and conditions of the Creative Commons Attribution (CC BY) license; additional terms may apply. By using this site, you agree to the Terms and Conditions and Privacy Policy.
This entry is offline, you can click here to edit this entry!
Video Production Service
Feedback