Environmentally Friendly Polymers

Environmentally Friendly Polymers

13 Environmentally Friendly Polymers Environmentally friendly or “green” polymers are those that are produced from renewable resource raw materials su...

2MB Sizes 6 Downloads 96 Views

13 Environmentally Friendly Polymers Environmentally friendly or “green” polymers are those that are produced from renewable resource raw materials such as corn or that are biodegradable or compostable. This is a developing area in packaging materials and though there are a relatively limited number of polymers used commercially, they will certainly become more numerous and more common in the future. Biodegradable plastics are made out of ingredients that can be metabolized by naturally occurring microorganisms in the environment. Some petroleum-based plastics will biodegrade eventually, but that process usually takes a very long time and contributes to global warming through the release of carbon dioxide. Petroleum-based plastic is derived from oil, a limited resource. Plastic based in renewable raw materials biodegrade much faster and can be almost carbon neutral. Renewable plastic is derived from natural plant products such as corn, oats, wood, and other plants, which helps ensure the sustainability of the earth. Polylactic acid (PLA) is the most widely researched and used 100% biodegradable plastic packaging polymer currently, and is made entirely from corn-based starch. Details on PLA are included in a following section. CellophaneÔ is a polymeric cellulose film made from the cellulose from wood, cotton, hemp, or other sources. There are several modifications made to cellulose called polysaccharides (cellulose esters), which are common including cellulose acetate, nitrocellulose, carboxymethyl cellulose (CMC), and ethyl cellulose. Details on cellophaneÔ and its derivatives are included in several following sections. Polycaprolactone (PCL) is biodegradable polyester that is often mixed with starch. Details on PLA are included in a following section. Polyhydroxyalkanoates (PHAs) are naturally produced, and include poly-3-hydroxybutyrate (PHB

or PH3B), polyhydroxyvalerate (PHV), and polyhydroxyhexanoate (PHH); A PHA copolymer called poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) is less stiff and tougher, and it may be used as packaging material. Several interesting green polymers are discussed in the next few paragraphs. These are ones for which no public permeation data have been identified. Polyanhydrides currently are used mainly in the medical device and pharmaceutical industry.1 Figure 13.1 shows the generalized structure of an anhydride polymer and two polyanhydrides that are used to encapsulate certain drugs. The poly(bis-carboxyphenoxypropane), pCCP, is relatively slow to degrade. The poly(sebacic anhydride), pSA, is fast to degrade. Separately neither of these materials can be

Figure 13.1 Polyanhydride chemical structures.

Permeability Properties of Plastics and Elastomers. DOI: 10.1016/B978-1-4377-3469-0.10013-X Copyright Ó 2012 Elsevier Inc. All rights reserved.

287

288

P ERMEABILITY P ROPERTIES

Figure 13.2 Polyglycolic acid chemical structures.

used, but if a copolymer is made in which 20% of the structure is pCCP and 80% is pSA, the overall properties meet the needs of the drug. Polyanhydrides are now being offered for general uses.

OF

P LASTICS

AND

E LASTOMERS

Polyglycolic acid (PGA) and its copolymers have found limited use as absorbable sutures and are being evaluated in the biomedical field, where its rapid degradation is useful. This rapid degradation has limited its use in other applications. The structure of PGA is shown in Fig. 13.2. Interest in the “green” materials is strong as the number of commercially available materials grows. Table 13.1 lists some of the commercial materials recently available. The following sections contain the details of several of the more common green polymers.

Table 13.1 A List of Some Environmentally Friendly Polymer Based Product Trade Name and Trademarks2 Trade Mark Aqua-Novon

Owner

Material

Novon International Inc. (USA)

PCL

Bayer AG Corporation (Germany)

Polyester amide

BioBag International AS

Polargruppen (Norway)

Mater-BiÒ

Bioceta, Biocell, Biocelat

Mazucchelli, S.p.A. (Italy)

Cellulose acetate

Biofan

Gunze (Japan)

PHB/PHBV

Biotec GmbH (Germany)

Starch

Biogreen

Mitsubishi Gas Chemical Co. (Japan)

PHB

BiomaxÒ

DuPont (USA)

PBS-co-PBST

Biomer

Biomer (Germany)

Polyester, PHB

Bionolle 1000

Showa Highpolymer Co. (Japan)

PBS

Bionolle 3000

Showa Highpolymer Co. (Japan)

PBS-co-PBSA

Biopac

Biopac Ltd (UK)

Starch

Biop AG Biopolymer GmbH (Germany)

Starch, biodegradable synthetic polymer

Trespaphan GmbH (Germany)

PLA

Biotec GmbH (Germany)

Starch, PLA, copolyester

BiopolÔ

Monsanto Co. (Italy)/Metabolix, Inc. (UK)

PHB, PHV and PHAs

BiopurÒ

Biotec GmbH (Germany)

Starch

Bioska

PlastiRoll Oy (Finland)

Starch/PVA

Bio-Solo

Indaco Manufacturing Ltd (Canada)

Starch, patented additives, PE

BiostarchÒ

Biostarch (Australia)

Maize starch

Bio-Stoll

Stoll Papierfolien (Germany)

Starch, LDPE/Ecostar, additive

Bioplast GmbH (Germany)

Thermoplastic starch (TPSÒ )

BAK

Ò

Bioflex

Ò

Ò

BioPar

BiophanÒ Bioplast

Biotec

Ò

Ò

(Continued )

13: E NVIRONMENTALLY F RIENDLY P OLYMERS

289

Table 13.1 (Continued ) Trade Mark

Owner

Ò

Material

Trans Furans Chemicals (Netherlands)

Furan resin

Biothene (UK)

Biofuels from planted soy

Solvay Polymers (Italy)

PCL

CelGreen PH/P-CA

Daicel Chemical Industries Ltd (Japan)

PCL/cellulose acetate

CelloTherm

UCB Films (UK)

Regular cellulose (for microwave)

Chronopol

Chronopol-Boulder, CO (USA)

PLA

Clean Green

StarchTech Inc, MN (USA)

Starch-based biopolymers

CohpolÔ

VTT Chemical Technology (Finland)

Starch ester

Japan Corn Starch (Japan)

Modified starch

Shell Chemicals (USA/NL)

PTT

Novon International Inc. (USA)

Polyolefin þ additives

EarthShell

EarthShell Corp., MD (USA)

Starch composite materials

Eastar Bio

Eastman Chemical Company (USA)

Copolyester

ECM Masterbatch Pellets

ECM Biofilms (USA)

Additives for polyolefin products

EcoflexÒ

BASF Corporation (Germany)

Poly(butyleneadipate)-co-PBAT

Eco-Flow

National Starch & Chemical (USA)

Starch-based biodegradable products

Eco-FoamÒ

National Starch & Chemical

Foamed starch

Eco-Lam

National Starch & Chemical

Starch, PET, PP

Cargill Dow Polymers (USA)

PLA

Ecoplast

Groen Granulaat (Netherlands)

Starch

EnPol

IRe Chemical Co. Ltd (South Korea)

PBS-co-PBSA

EnPac/DuPont/ConAgra (USA)

Starch/PVA

Storopack Inc. (USA)

Polystyrene expanded products

Planet Polymer Technologies, Inc. (USA)

Cellulose acetate

EverCorn, Inc. (USA)

Starch

Japan Corn Starch Co., Ltd (Japan); Department Agrobiotechnology, Tulln, (Austria)

50% wood wastes

FLO-PAK BIO 8Ò

FP International (USA)

Starch (corn or wheat)

Gohsenol

Nippon Gohsei (Japan)

PVA

GreenFill

Green Light Products Ltd (UK)

Starch/PVA

SK Corporation (South Korea)

Starch, aliphatic polyester

Idroplax S.r.L. (Italy)

PVA

LACEAÒ

Mitsui Chemicals, Inc. (Japan)

PLA from fermented glucose

Lacty

Shimadzu Corp. (Japan)

PLA

BioRez

BiotheneÒ CAPA

Ò

Ò

Cornpol

Corterra Degra-Novon

Ò

Ò

EcoPLA

Ò

EnvirofilÔ Ò

Enviromold

EnviroPlastic

Ò

EverCornÔ Fasal

Ò

Ò

Greenpol

Hydrolene

Ò

(Continued)

290

P ERMEABILITY P ROPERTIES

OF

P LASTICS

AND

E LASTOMERS

Table 13.1 (Continued ) Trade Mark

Owner

Lignopol

Material

Borregaard Deutschland GmbH

Lignin

STOROpack (Germany)

EPS/starch

Lunare

Nippon Shokubai Co., Ltd

Polyethylenesuccinate/adipate

Mater-BiÔ

Novamont S.p.A. (Italy)

Starch/cellulose derivative

Mazin

Mazin International (USA)

PLA

MirelÔ

Metabolix Inc. (USA)

Corn sugar

Innovia Films (UK)

Regenerated cellulose film

Cargill Co. (USA)

PLA

Procter & Gamble Co. (USA)

PHB-co-PHA

Ecostar GmbH (Germany)

Starch

Paragon

Avebe Bioplastic (Germany)

Starch

PlanticÒ

Plantic Technologies (Australia)

Corn-starch materials

Poly-NOVONÒ

Novon International

Starch additives

Polystarch

Willow Ridge Plastics, Inc. (USA)

Additives

POLYOXÔ

Union Carbide Corporation (USA)

Poly(ethylene oxide)

POVAL

Kuraray Povol Co., Ltd (Japan)

PVA

Hayashibara Biochemical (Japan)

Starch

Storopack, Inc. (Germany)

Starch

Ventus Kunststoff GmbH

Mater-Bi

Buna SOW Leuna (Germany)

Starch acetate, plasticizer

Sunkyong Ltd (South Korea)

Aliphatic-co-polyester

Rodenburg Biopolymers (Netherlands)

Starch (from potato waste)

SoronaÒ

DuPont Tate & Lyle (USA)

PDO

SoyOylÔ

Urethane Soy Systems Co. Inc. (USA)

Soy-based products

SPI-Tek

Symphony Plastic Technologies Plc (UK)

Additives

SupolÒ

Supol GmbH (Germany)

Starch plant oil and sugars

Union Carbide Corp. (USA)

PCL

Stora Enso Oyj (Finland)

Cellulose, food tray

Vegeplast S.A.S. (France)

Starch

Loose Fill

Ò

NatureFlexÔ NatureWorks

Ò

NodaxÔ Novon

Ò

Pullulan RenaturE

Ò

ReSourceBagsÔ Sconacell

Ò

Sky-green Solanyl

TONE

Ò

Ò

Trayforma Ò

Vegemat

Abbreviations: PHBV, polyhydoxybutyrate valerate; PBS-co-PBST, polybutylene succinate, copolymer poly(butylene succinate-terephthalate); PBS-co-PBSA, polybutylene succinate copolymer polybutylene succynate adipate; PHV, polyhydroxyvalerate; LDPE, low-density polyethylene; PTT, polytrimethylene terephthalate; PBAT, poly(butylene adipate-coterephthalate); EPS, expanded polystyrene; l PDO, poly(dioxanone).

13: E NVIRONMENTALLY F RIENDLY P OLYMERS

291

13.1 CellophaneÔ CellophaneÔ is a polymeric cellulose film made from the cellulose from wood, cotton, hemp, or other sources. The raw material of choice is called dissolving pulp, which is white like cotton and contains 92e98% cellulose. The cellulose is dissolved in alkali in a process known as mercerization. It is aged several days. The mercerized pulp is treated with carbon disulfide to make an orange solution called viscose, or cellulose xanthate. The viscose solution is then extruded through a slit into a bath of dilute sulfuric acid and sodium sulfate to reconvert the viscose into cellulose. The film is then passed through several more baths, one to remove sulfur, one to bleach the film, and one to add glyc-

erin to prevent the film from becoming brittle. CellophaneÔ has a CAS number of 9005-81-6. The approximate chemical structures are shown in Fig. 13.3. The CellophaneÔ may be coated with nitrocellulose or wax to make it impermeable to water vapor. It may also be coated with polyethylene or other materials to make it heat sealable for automated wrapping machines. Manufacturers and trademarks: Innovia CellophaneÔ. Applications and uses: Cellulosic film applications include tapes and labels, photographic film, coatings for paper, glass, and plastic. Medical applications for cellulosic films include dialysis membranes (Tables 13.2e13.4).

Figure 13.3 Conversion of raw cellulose to viscose.

Table 13.2 Permeability of Oxygen through Polyvinylidene Chloride (PVDC) Coated CellophaneÔ Film3 Temperature ( C) Test Method Relative humidity (%) Source document units 3

35

20

JIS Z1707

ASTM D3985

0

65

85

100

0.07

0.26

0.71

2.06

0.03

0.10

0.28

0.81

2

Permeability coefficient (cm mil/100 in. day) Normalized units 3

2

Permeability coefficient (cm mm/m day atm) Sample thickness: 0.023 mm.

292

P ERMEABILITY P ROPERTIES

P LASTICS

OF

AND

E LASTOMERS

Table 13.3 Permeation of Various Gases through Cellulose (CellophaneÔ)4 Permeability Coefficient 

Penetrant

Temperature ( C)

Source Document Units 1010 (cm3 cm/cm3 s cm Hg)

Normalized Units (cm3 mm/m2 day atm)

Helium

20

0.0005

0.033

Hydrogen

25

0.0065

0.427

Nitrogen

25

0.0032

0.210

Oxygen

25

0.0021

0.138

Carbon dioxide

25

0.0047

0.309

Hydrogen sulfide

45

0.0006

0.039

Sulfur dioxide

25

0.0017

0.112

Water

25

1900

12500

Table 13.4 Oxygen Gas Transmission Rate and Water Vapor Transmission Rate of Innovia CellophaneÔ Films5

Product Code

Film Structure

Oxygen Gas

Water Vapor

Transmission Rate

Transmission Rate

Source Document Units (cm3/ 100 in.2 day bar)

Normalized Units (cm3/ m2 day atm)

Source Document Units (g/ 100 in.2 day)

Normalized Units (g/m2 day)

DM 320

Nitrocellulose coated one side

0.19

3.0

10

183

DMS 345

Nitrocellulose coated one side

0.19

3.0

10

183

‘K’ HB20 (or XS)

Polyvinylidene coated both sides

0.19

3.0

LST 195

Nitrocellulose coated both sides

0.19

3.0

MST/ MT33

Nitrocellulose coated both sides

0.19

3.0

P00

Uncoated

0.19

3.0

>95

>1700

P25

Uncoated

0.19

3.0

>95

>1700



0.65

70

1.3

12

1284

24

Oxygen test method: ASTM F1927, at 24 C and 5% relative humidity. WVTR test method: ASTM E96, at 38  C and 90% relative humidity.

13: E NVIRONMENTALLY F RIENDLY P OLYMERS

293

13.2 Nitrocellulose Nitrocellulose is made by treating cellulose with a mixture of sulfuric and nitric acids. This changes

Figure 13.4 Structure of nitrocellulose.

the hydroxyl groups (eOH) in the cellulose to nitro groups (eNO3) as shown in Fig. 13.4. Nitrocellulose, also know as gun cotton and the main ingredient of smokeless gunpowder, decomposes explosively. In the early twentieth century, it was found to make an excellent film and paint. Nitrocellulose lacquer was used as a finish on guitars and saxophones for most of the twentieth century and is still used on some current applications. Manufactured by (among others) DuPont, the paint was also used on automobiles sharing the same color codes as many guitars including Fender and Gibson brands. Nitrocellulose lacquer is also used as an aircraft dope, painted onto fabric-covered aircraft to tauten and provides protection to the material. Its CAS number is 900470-0. Nitrocellulose is not usually used for film applications but more commonly is part of multilayered film structures, especially those based on CellophaneÔ. Manufacturers and trade names: Innovia Films CellophaneÔ. Applications and uses: Food wrap (Table 13.5).

Table 13.5 Permeation of Gases at 25  C through Nitrocellulose Film6 Permeability Coefficient Permeate Gas

Pressure Differential (mm Hg)

Source Document Units (cm3 mm/cm2 s cm Hg  109)

Normalized Units (cm3 mm/cm2 day atm)

Helium

4.68

6.9

Nitrogen

5.21

0.116

Oxygen

4.995

1.95

128

Carbon dioxide

4.567

2.12

139

Sulfur dioxide

4.442

1.76

116

Ammonia

4.04

Water

2.195

Ethane

4.92

0.063

4.1

Propane

4.57

0.0084

0.6

n-butane

4.34

57.1 6295

~0

453 7.6

3749 413355

~0

294

P ERMEABILITY P ROPERTIES

OF

P LASTICS

AND

E LASTOMERS

13.3 Cellulose Acetate Cellulose acetate is the acetate ester of cellulose. It is sometimes called Acetylated cellulose or xylonite. Its CAS number is 9004-35-7 and the approximate chemical structure is shown in Fig. 13.5. Manufacturers and trade names: Celanese Cellulose Acetate; Eastman Chemical Company Tenite. Applications and uses: Cellulose acetate is used as a film base in photography, as a component in some adhesives, and as a frame material for eyeglasses; it is also used as a synthetic fiber and in the manufacture of cigarette filters, found in screwdriver handles, ink pen reservoirs, x-ray films (Tables 13.6 and 13.7).

Figure 13.5 Chemical structure of cellulose acetate.

Table 13.6 Permeability of Various Gases at 35  C through Cellulose Acetate Membranes7 Permeability Coefficient Permeant Gas

Source Document Units (cm3 (STP)$cm/cm2 s cm Hg)

Normalized Units (cm3 mm/m2 day atm)

1.00  109

Helium Oxygen Argon Nitrogen Krypton Xenon Carbon dioxide

1.30  10

10

7.70  10

11

2.60  10

11

3.50  10

11

9.70  10

12

6.30  10

10

656.6 85.4 50.6 17.1 23.0 6.4 413.7

Table 13.7 Permeability of Various Gases at 22  C through Dense and High-Flux Cellulose Acetate8 Source Document Units

Normalized

Dense Cellulose Acetate (cm3 (STP)$cm/ cm2 s cm Hg)*

High-Flux Cellulose Acetatea (cm3 (STP)/ cm2 s cm Hg)

Helium

1.36  109

2.80  105

893

1.84  106

Neon

2.40  1010

6.00  107

158

3.94  104

Gas

Dense Cellulose Acetate (cm3 mm/ m2 day atm)*

1.90  106

Oxygen

High-Flux Cellulose Acetatea (cm3 cm/ m2 day atm)

1.25  105

Argon

3.20  1011

1.10  106

Methane

1.40  1011

7.00  107

9.2

4.60  104

Nitrogen

1.40  1011

6.00  107

9.2

3.94  104

Propane

<1013

3.00  107

21

7.22  104

1.97  104

See also Figs. 13.6e13.10.aWhile the membrane thickness for fully dense membrane can be measured, the nominal thickness of high-flux material cannot be used to calculate permeability from flow rates. For this reason, permeation rates, not permeabilities, are given for high-flux sample.

13: E NVIRONMENTALLY F RIENDLY P OLYMERS

13.4 Ethyl Cellulose Ethyl cellulose is similar in structure to cellulose and cellulose acetate but some of the hydroxyl (eOH) functional groups in the cellulose are replaced by the ethoxy group (eOeCH2eCH3). Ethyl cellulose has a CAS number of 9004-57-3 and its structure is shown in Fig. 13.11.

295

Manufacturers and trade names: Dow EthocelÔ, Ashland AqualonÒ . Applications and uses: Pharmaceutical applications, cosmetics, nail polish, vitamin coatings, printing inks, specialty coatings, food packaging (Tables 13.8e13.10).

Figure 13.6 Permeation rates of noble gases at 22  C through high-flux cellulose acetate films.8 *The nominal thickness of high-flux material cannot be used to calculate permeability from flow rates. For this reason, permeation rates, not permeability coefficients, are given.

Figure 13.7 Permeation rates of common gases at 22  C through high-flux cellulose acetate films.8 *The nominal thickness of high-flux material cannot be used to calculate permeability from flow rates. For this reason, permeation rates, not permeability coefficients, are given.

296

P ERMEABILITY P ROPERTIES

OF

P LASTICS

Figure 13.8 Permeation of noble gases at 35  C through cellulose acetate films.7

Figure 13.9 Permeation of common gases at 35  C through cellulose acetate films.7

AND

E LASTOMERS

13: E NVIRONMENTALLY F RIENDLY P OLYMERS

297

Figure 13.10 Permeation of hydrogen sulfide vs. temperature through plasticized and unplasticized cellulose acetate films.9

Figure 13.11 Structure of ethyl cellulose.

298

P ERMEABILITY P ROPERTIES

OF

P LASTICS

AND

E LASTOMERS

Figure 13.12 Permeation of various gases vs. temperature for Dow EthocelÔ ethyl cellulose film.11

Table 13.8 Permeation of Gases through Ethyl Cellulose6 Permeability Coefficient

Permeant Gas Helium Nitrogen

Source Document Units 3 109 3 (cm mm/cm2 s cm Hg) 53.4 4.43

Normalized Units (cm3 mm/ m2 day atm) 3510 291

Oxygen

14.7

965

Argon

10.2

670

Carbon dioxide

113

7420

Sulfur dioxide

264

17,300

Ammonia

705

46,300

8930

586,000

Water Ethane

9.2

604

Propane

3.7

243

n-Butane

3.87

254

n-Pentane

3.7

243

n-Hexane

7.66

503

13: E NVIRONMENTALLY F RIENDLY P OLYMERS

299

Table 13.9 Permeation of Various Gases at 35  C through Membranes Made from Ashland AqualonÒ Ethyl Cellulose10 Permeability Coefficient Source Document Units 109 [cm3 (STP) cm/cm2 s cm Hg] Material Grade

Ethoxy Content (%)

EC K-100

47.2

EC N-100 EC T-10

Carbon Dioxide

Helium

Oxygen

Methane

Nitrogen

8.9

4.9

1.46

0.88

0.41

47.9

11.6

6.6

1.94

1.24

0.58

49.6

14.7

7.9

2.33

1.41

0.65

Normalized Units (cm3 mm/m2 day atm) EC K-100

47.2

78

43

12.8

7.7

3.6

EC N-100

47.9

102

58

17.0

10.9

5.1

EC T-10

49.6

129

69

20.4

12.3

5.7

Pressure differential: 10 atm. Table 13.10 Permeation Selectivity of Various Gases Pairs at 35  C through Membranes Made from Ashland AqualonÒ Ethyl Cellulose10 Material Grade

Ethoxy Content (%)

a(CO2/ CH4)

a(O2/ N2)

a(He/ CH4)

a(CO2/ N 2)

a(O2/ He)

EC K-100

47.2

10.1

3.5

5.7

21.8

1.7

EC N-100

47.9

9.4

3.3

5.4

20.0

1.7

EC T-10

49.6

10.4

3.6

5.6

22.5

1.8

See also Fig. 13.12.

13.5 Polycaprolactone PCL is biodegradable polyester with a low melting point of around 60  C and a glass transition temperature of about 60  C. PCL is prepared by ring opening polymerization of 3-caprolactone using a catalyst such as stannous octanoate. The structure of PCL is shown in Fig. 13.13. PCL is degraded by hydrolysis of its ester linkages in physiological conditions (such as in the human body) and has therefore received a great deal of attention for use as an implantable biomaterial. In

Figure 13.13 Structure of polycaprolactone.

particular, it is especially interesting for the preparation of long-term implantable devices. A variety of drugs have been encapsulated within PCL beads for controlled release and targeted drug delivery. PCL is often mixed with starch to obtain a good biodegradable material at a low price. Manufacturers and trade names: Perstorp CAPAÒ (previously Solvay), Dow Chemical Tone (discontinued). Applications and uses: The mix of PCL and starch has been successfully used for making trash bags in Korea (Yukong Company) (Tables 13.11e13.14).

300

P ERMEABILITY P ROPERTIES

OF

P LASTICS

AND

E LASTOMERS

Table 13.11 Water Vapor Permeation at 20  C and 100% RH through Polycaprolactone Film12 Source Document Units, Vapor Permeation Rate Orientation Speed (m/min)

g mm/m2 day kPaa

g mm/m2 day atma

1.046

2.2

64

6485

0.051

18.5

3

304

Film Thickness (mm)

a

Vapor permeation rates do not usually contain a pressure differential; see reference for description of nonstandard test method.

Table 13.12 Oxygen Permeation at 35  C and 0% Relative Humidity through Polycaprolactone Film12 Source Document Units

Normalized Units

Orientation Speed (m/min)

Permeability Coefficient (cm3 mm/m2 day kPa)

Permeability Coefficient (cm3 mm/m2 day atm)

1.046

2.2

945

96

0.051

18.5

1000

101

Film Thickness (mm)

Test equipment: Mocon Ox-Tran 2/20 Modular System.

Table 13.13 Water Vapor Permeation at 20  C and 100% RH through Films Made from Blends of Polycaprolactone, Starch and Glycerol12 Film Composition: PCL/Starch/ Glycerol (wt%)

a

Film Thickness (mm)

Orientation Speed (m/min)

Source Document Units

Normalized Units

Vapor Permeation Rate (g mm/m2 day kPaa)

Vapor Permeation Rate (g mm/m2 day atma)

0/60/40

0.469

0

190

19,300

2/58/40

0.204

0

100

10,100

10/54/36

0.665

0

215

21,800

10/54/36

0.195

3.8

100

10,100

20/48/32

0.208

2.2

65

6600

20/48/32

0.070

9.9

30

3040

30/42/28

0.460

0

88

8900

30/42/28

0.217

2.2

26

2600

30/42/28

0.051

8.8

11

1100

100/0/0

1.046

2.2

64

6500

100/0/0

0.051

18.5

3

300

Vapor permeation rates do not usually contain a pressure differential; see reference for description of nonstandard test method.

13: E NVIRONMENTALLY F RIENDLY P OLYMERS

301

Table 13.14 Oxygen Permeation at 35  C and 0% Relative Humidity through Films Made from Blends of Polycaprolactone, Starch and Glycerol12 Film Composition: PCL/Starch/ Glycerol (wt%)

Film Thickness (mm)

Source Document Units

Normalized Units

Permeability Coefficient (cm3 mm/m2 day kPa)

Permeability Coefficient (cm3 mm/m2 day atm)

Orientation Speed (m/min)

0/60/40

0.469

0

0

0

2/58/40

0.204

0

0

0

10/54/36

0.665

0

0

0

10/54/36

0.195

3.8

0

0

20/48/32

0.208

2.2

17

1.7

20/48/32

0.070

9.9

1

0.1

30/42/28

0.460

0

42

4.3

30/42/28

0.217

2.2

21

2.1

30/42/28

0.051

8.8

20

2.0

100/0/0

1.046

2.2

945

96

100/0/0

0.051

18.5

1000

101

Test equipment: Mocon Ox-Tran 2/20 Modular System.

13.6 Poly(Lactic Acid) PLA is derived from renewable resources, such as corn starch or sugarcanes. PLA polymers are considered biodegradable and compostable. PLA is a thermoplastic, high-strength, high-modulus polymer that can be made from annually renewable sources to yield articles for use in either the industrial packaging field or the biocompatible/bioabsorbable medical device market. Bacterial fermentation is used to make lactic acid, which is then converted to the lactide dimer to remove the water molecule that would otherwise limit the ability to make high-molecular-weight polymer. The lactide dimer, after the water is removed, can be polymerized without the production of the water.

Figure 13.14 Conversion of lactic acid to polylactic acid.

This process is shown in Fig. 13.14. The PLA CAS number is 9002-97-5. Manufacturers and trade names: FKur Bio-FlexÒ , Cereplast Inc. CompostablesÒ , Mitsubishi Chemical FozeasÒ , NatureEorks LLC IngeoÔ, Alcan Packaging CeramisÒ -PLA. Applications and uses: Biomedical applications, such as sutures, stents, dialysis media, and drug delivery devices. It is also being evaluated as a material for tissue engineering; loose-fill packaging, compost bags, food packaging, and disposable tableware. PLA can be in the form of fibers and nonwoven textiles. Potential uses: upholstery, disposable garments, awnings, feminine hygiene products. See also Figs. 13.15e13.19.

302

Figure 13.15 Permeation coefficient of methane vs. temperature through linear polylactic acid film.14

Figure 13.16 Permeation coefficient of carbon dioxide vs. temperature through linear polylactic acid film.14

Figure 13.17 Permeation coefficient of nitrogen vs. temperature through linear polylactic acid film.14

P ERMEABILITY P ROPERTIES

OF

P LASTICS

AND

E LASTOMERS

13: E NVIRONMENTALLY F RIENDLY P OLYMERS

303

Figure 13.18 Permeation coefficient of oxygen vs. temperature through linear polylactic acid film.14

Figure 13.19 Permselectivity of carbon dioxide/methane vs. temperature through linear polylactic acid film.14

13.7 Poly-3-Hydroxybutyrate PHAs are naturally produced and include PHB (or PH3B), PHV, and PHH. A PHA copolymer called PHBV is less stiff and tougher, and it may be used as a packaging material. Chemical structures of some of these polymers are shown in Fig. 13.20. Manufacturers and trade names: FKur Bio-FlexÒ , Cereplast Inc. CompostablesÒ , Mitsubishi Chemical FozeasÒ , NatureWorks LLC IngeoÔ, Alcan Packaging CeramisÒ -PLA. Applications and uses: Biomedical applications, such as sutures, stents, dialysis media, and drug delivery devices. It is also being evaluated as a material for tissue engineering; loose-fill packaging, compost bags, food packaging, and disposable tableware. PLA can be in the form of fibers and nonwoven textiles.

Figure 13.20 Structures xyalkanoates.

of

several

polyhydro-

304

P ERMEABILITY P ROPERTIES

OF

P LASTICS

AND

E LASTOMERS

Table 13.15 Permeability Coefficients for Poly-3-Hydroxybutyrate (PHB) Membranes13 Temperature ( C)

Methanol

Ethanol

n-Propanol

Water

Source Document Units, Permeability Coefficient Barrers 30

e

e

e

520

50

1130

890

480

750

55

1590

900

520

990

60

1640

920

530

1050

65

2090

1230

590

1900 3

2

Normalized Units, Permeability Coefficient (cm mm/m day atm) 30

e

e

e

34,100

50

74,200

58,400

31,500

49,200

55

104,000

59,100

34,100

65,000

60

108,000

60,400

34,800

68,900

65

137,000

80,800

38,700

125,000

5% error.

Potential uses: upholstery, disposable garments, awnings, feminine hygiene products (Table 13.15).

References 1. Jain JP, Modi S, Domb AJ, Kumar N. Role of polyanhydrides as localized drug carriers. J Control Release 2005;103:541e63. 2. Chiellini E. Environmentally compatible food packaging. In: Environmentally compatible food packaging. Cambridge (UK): Woodhead Publishing Ltd; 2008. p. 371e95. 3. EVAL film properties comparison. Supplier technical report. Kuraray Co., Ltd; 2003. 4. Affinity polyolefin plastomers. Form No. 305-01953-893 SMG. Dow Chemical Company; 1993. 5. Innovia specification sheets. Edition USA; 2005. 6. Hsieh PY. Diffusibility and solubility of gases in ethylcellulose and nitrocellulose. J Appl Polym Sci 1963;7(5):1743e56. Available from: http:// doi.wiley.com/10.1002/app.1963.070070515. 7. Nakai Y, Yoshimizu H, Tsujita Y. Enhanced gas permeability of cellulose acetate membranes under microwave irradiation. J Memb Sci 2005;256:72e7. Available from: http:// linkinghub.elsevier.com/retrieve/pii/ S037673880500147X. 8. Gantzel PK, Merten U. Gas separations with high-flux cellulose acetate membranes. Ind Eng

Chem Process Des Dev 1970;9(2):331e2. Available from: http://pubs.acs.org/doi/abs/10. 1021/i260034a028. 9. Heilman W, Tammela V, Meyer J, Stannett V, Szwarc M. Permeability of polymer films to hydrogen sulfide gas. Ind Eng Chem 1956;48: 821e4. 10. Houde A, Stern S. Permeability of ethyl cellulose to light gases. Effect of ethoxy content. J Memb Sci 1994;92(1):95e101. Available from: http://linkinghub.elsevier.com/retrieve/pii/ 0376738894800162. 11. Brubaker DW, Kammermeyer K. Separation of gases by means of permeable membranes. Permeability of plastic membranes to gases. Ind Eng Chem 1952;44(6):1465e74. Available from: http://pubs.acs.org/cgi-bin/doilookup/?10. 1021/ie50510a071. 12. Myllyma¨ki O, Mylla¨rinen P, Forssell P, et al. Mechanical and permeability properties of biodegradable extruded starch/polycaprolactone films. Packag Technol Sci 1998;11(6):265e74. 13. Poley LH, Silva MGD, Vargas H, Siqueira MO, Sa´nchez R. Water and vapor permeability at different temperatures of poly (3-hydroxybutyrate) dense membranes. Polı´meros 2005;15:22e6. 14. Lehermeier H. Gas permeation properties of poly(lactic acid). J Memb Sci 2001;190: 243e51.