PBAT (short for polybutylene adipate terephthalate) is a

biodegradable Biodegradation is the breakdown of organic matter by microorganisms, such as bacteria and fungi. It is generally assumed to be a natural process, which differentiates it from composting. Composting is a human-driven process in which biodegradati ...

random

copolymer In polymer chemistry, a copolymer is a polymer derived from more than one species of monomer. The polymerization of monomers into copolymers is called copolymerization. Copolymers obtained from the copolymerization of two monomer species are some ...

, specifically a

copolyester Copolyester forms when modifications are made to polyesters, which are combinations of diacids and diols. For example, by introducing other diacids, such as isophthalic acid (IPA), or other diols, such as cyclohexane dimethanol (CHDM) to the polyes ...

adipic acid Adipic acid or hexanedioic acid is the organic compound with the formula (CH2)4(COOH)2. From an industrial perspective, it is the most important dicarboxylic acid: about 2.5 billion kilograms of this white crystalline powder are produced annually, ...

1,4-butanediol 1,4-Butanediol, colloquially known as BD or BDO, is a primary alcohol, and an organic compound, with the formula HOCH2CH2CH2CH2OH. It is a colorless viscous liquid. It is one of four stable isomers of butanediol. Synthesis In industrial sy ...

and

terephthalic acid Terephthalic acid is an organic compound with formula C6H4(CO2H)2. This white solid is a commodity chemical, used principally as a precursor to the polyester PET, used to make clothing and plastic bottles. Several million tonnes are produced annua ...

(from

dimethyl terephthalate Dimethyl terephthalate (DMT) is an organic compound with the formula C6H4(COOCH3)2. It is the diester formed from terephthalic acid and methanol. It is a white solid that melts to give a distillable colourless liquid.Richard J. Sheehan "Terepht ...

). PBAT is produced by many different manufacturers and may be known by the brand names ecoflex'', ''Wango, Ecoworld, Eastar Bio, and Origo-Bi. It is also called poly(butylene adipate-co-terephthalate) and sometimes polybutyrate-adipate-terephthalate (a misnomer) or even just "polybutyrate". It is generally marketed as a fully biodegradable alternative to

low-density polyethylene Low-density polyethylene (LDPE) is a thermoplastic made from the monomer ethylene. It was the first grade of polyethylene, produced in 1933 by Imperial Chemical Industries (ICI) using a high pressure process via free radical polymerization. Its ...

, having many similar properties including flexibility and resilience, allowing it to be used for many similar uses such as plastic bags and wraps. It is depicted as a block co-polymer here due to the common synthetic method of first synthesizing two copolymer blocks and then combining them. However, it is important to note that the actual structure of the polymer is a random co-polymer of the blocks shown.

History

Production of plastics for use in the industrial sector around the world makes up a very large market. PET (

polyethylene terephthalate Polyethylene terephthalate (or poly(ethylene terephthalate), PET, PETE, or the obsolete PETP or PET-P), is the most common thermoplastic polymer resin of the polyester family and is used in fibres for clothing, containers for liquids and foods ...

) is one of the dominant plastics within this market. It is commonly used for bottles because it makes a rigid container that is very lightweight. However, because of the stability of PET, it is also highly resistant to biodegradation, posing a significant environmental problem because of the amount of PET produced, sold, used and thrown away on a daily basis. An estimated 30% of the world production of PET goes into making these plastic bottles and only from 15% to 35% is recycled; the rest usually end up in a landfill. This has stimulated research into polymers that function comparably to PET, but are

. As with all developments in the realm of materials there are several requirements for the 'ideal' material. For biodegradable plastics, they would be: cheap, renewable, easy to produce and eco-friendly. In addition to these, the polymer should be resistant enough to be functional, such as handling the strain of being put under pressurize, and flexible so that it is easy to mold. There are no homopolymers that perfectly provide every one of these features. Therefore, researchers have turned their attention to

copolymers In polymer chemistry, a copolymer is a polymer derived from more than one species of monomer. The polymerization of monomers into copolymers is called copolymerization. Copolymers obtained from the copolymerization of two monomer species are some ...

: combinations of polymers that have chemical and mechanical properties that complement each other. This led to identifying poly(butylene adipate-co-terephthalate) (PBAT) as a potential copolymer for blending. PBAT is a random copolymer known for being flexible and tough. This makes it ideal for combination with other

polymers that have high

elastic modulus An elastic modulus (also known as modulus of elasticity) is the unit of measurement of an object's or substance's resistance to being deformed elastically (i.e., non-permanently) when a stress is applied to it. The elastic modulus of an object is ...

and strength, but are very

brittle A material is brittle if, when subjected to stress, it fractures with little elastic deformation and without significant plastic deformation. Brittle materials absorb relatively little energy prior to fracture, even those of high strength. Bre ...

. This allows for the production of blended copolymers that can replace industry-standard plastics with environmentally safe and biodegradable plastics that will harmlessly disappear in a short period of time. The most important reason for using PBAT as the flexible complement to other polymers is that it will preserve

biodegradability Biodegradation is the breakdown of organic matter by microorganisms, such as bacteria and fungi. It is generally assumed to be a natural process, which differentiates it from composting. Composting is a human-driven process in which biodegradati ...

; as long as both copolymers can degrade, the blended copolymer will also degrade.

Properties

PBAT is classified as a random copolymer due to its random structure. This also means that it cannot crystallize to any significant degree due to the absence of any kind of structural order. This leads to several physical properties: wide melting point, low

and stiffness, but high flexibility and toughness. The flexibility and toughness of this polymer makes it ideal for blending with another biodegradable polymer that is strong and rigid for bottle production. The drawback of this polymer is that if it has high flexibility and toughness, then it will not be strong and rigid. This makes it non-ideal for any situation in which a strong, rigid container is desired. An example of this would be transparent barriers, such as those made of plexiglass (

Poly(methyl methacrylate) Poly(methyl methacrylate) (PMMA) belongs to a group of materials called engineering plastics. It is a transparent thermoplastic. PMMA is also known as acrylic, acrylic glass, as well as by the trade names and brands Crylux, Plexiglas, Acrylite, ...

), a transparent glass substitute. PBAT is fully biodegradable when composted due to the presence of butylene adipate groups. The high stability and mechanical properties come from the terephthalate portions. Does not degrade in marine and fresh water. The

CAS Registry Number A CAS Registry Number (also referred to as CAS RN or informally CAS Number) is a unique identification number assigned by the Chemical Abstracts Service (CAS), US to every chemical substance described in the open scientific literature. It inclu ...

of PBAT is 60961-73-1.

Preparation

PBAT is synthesized from the polymer of

and

and the polymer of

(DMT) with 1,4-butanediol. Adipic acid and 1,4-butanediol are polymerized to create their

polyester Polyester is a category of polymers that contain the ester functional group in every repeat unit of their main chain. As a specific material, it most commonly refers to a type called polyethylene terephthalate (PET). Polyesters include natural ...

(plus water). DMT and 1,4-butanediol are also reacted to form their polyester (plus

methanol Methanol (also called methyl alcohol and wood spirit, amongst other names) is an organic chemical and the simplest aliphatic alcohol, with the formula C H3 O H (a methyl group linked to a hydroxyl group, often abbreviated as MeOH). It is a ...

). This polyester is then added to the butylene adipic acid polyester by using tetrabutoxytitanium (TBOT) as a

transesterification In organic chemistry, transesterification is the process of exchanging the organic group R″ of an ester with the organic group R' of an alcohol. These reactions are often catalyzed by the addition of an acid or base catalyst. The reaction can ...

catalyst; an overabundance of 1,4-butanediol influences chain lengths. The result is a copolymer of the two previously prepared polymers. This is a random copolymer, because there is no control on the

dispersity In chemistry, the dispersity is a measure of the heterogeneity of sizes of molecules or particles in a mixture. A collection of objects is called uniform if the objects have the same size, shape, or mass. A sample of objects that have an inconsi ...

of the

polymer A polymer (; Greek '' poly-'', "many" + ''-mer'', "part") is a substance or material consisting of very large molecules called macromolecules, composed of many repeating subunits. Due to their broad spectrum of properties, both synthetic a ...

chain lengths or block structuring in the copolymerization reactions; repeat positions are not controlled. If A =

of adipic acid and B = polyester of DMT, each with 1,4-butanediol, then the chain structuring could look like any of these: AABABBABA or ABABAAAABB or ABABABBBBA; there is no selectivity for A and B reacting with themselves or each other.

Commercial sources

PBAT is produced commercially by

BASF BASF Societas Europaea, SE () is a German multinational corporation, multinational chemical company and the List of largest chemical producers, largest chemical producer in the world. Its headquarters is located in Ludwigshafen, Germany. The ...

under the trademark ecoflex and in a blend with poly(lactic acid) called ecovio, by Novamont as Origo-Bi and in a blend with starch called Mater-Bi, by Zhuhai Wango Chemical Co Ltd under the name Wango, by JinHui Zhaolong as Ecoworld and in a blend with starch called Ecowill, and by

Eastman Chemical Eastman Chemical Company is an American company primarily involved in the chemical industry. Once a subsidiary of Kodak, today it is an independent global specialty materials company that produces a broad range of advanced materials, chemicals and ...

as Eastar Bio. Furthermore, suppliers in China and other nations now produce PBAT. These companies include Zhejiang Biodegradable Advanced Material Co. Ltd, Dongguan Xinhai Environmental Protection Material Co., Ltd., Hangzhou Ruijiang Chemical Co., Ltd., and Jiangsu Torise Biomaterials Co., Ltd. in China as well as Green Chemical Co., Ltd. and WILLEAP in South Korea.

Current and future uses

PBAT is marketed commercially as a fully

biodegradable plastic Biodegradable plastics are plastics that can be decomposed by the action of living organisms, usually microbes, into water, carbon dioxide, and biomass. Biodegradable plastics are commonly produced with renewable raw materials, micro-organisms, ...

, with BASF's ecoflex showing 90% degradation after 80 days in testing. Particular applications that are highlighted by the manufacturers include

cling wrap Cling may refer to: * "Cling", a song by Days of the New from their 1997 album ''Days of the New'' (album) * Cling, a C++ interpreter; see CINT * "Cling Cling", a song by Japanese girl group Perfume from the 2014 album ''Cosmic Explorer'' * Cling ...

for food packaging, compostable

plastic bags A plastic bag, poly bag, or pouch is a type of container made of thin, flexible, plastic film, nonwoven fabric, or plastic textile. Plastic bags are used for containing and transporting goods such as foods, produce, powders, ice, magazines, c ...

for gardening and agricultural use, and as water resistant coatings for other materials, as in

paper cups A paper cup is a disposable cup made out of paper and often lined or coated with plastic or wax to prevent liquid from leaking out or soaking through the paper. It may be made of recycled paper and is widely used around the world. History Paper ...

. Due to its high flexibility and biodegradable nature, PBAT is also marketed as an additive for more rigid biodegradable plastics to impart flexibility while maintaining full

of the final blend. PBAT is already widely marketed and used for all of the above applications, but is also being investigated as a component in antimicrobial films. In such films, PBAT serves as the bulk of the film with the antimicrobial agent being incorporated during processing. The antimicrobial films would be used in food packaging to inhibit bacterial growth, helping to preserve food products safely.{{cite journal, author=Luis Bastarrachea , author2=Sumeet Dhawan , author3=Shyam S. Sablani , author4=Jae-Hyun Mah , author5=Dong-Hyun Kang , author6=Jinwen Zhang , author7=Juming Tang, title=Biodegradable Poly(butylene adipate-co-terephthalate) Films Incorporated with Nisin: Characterization and Effectiveness against Listeria innocua, journal=Journal of Food Science, year=2010, volume=75, issue=4, pages=E215–E224, url=http://www.bsyse.wsu.edu/tang/main/publications/pdfdocs/articles-published/tang184.pdf, accessdate=14 February 2014, doi=10.1111/j.1750-3841.2010.01591.x, pmid=20546402

References

Polyesters Terephthalate esters