ORIGINAL PAPER

Biodegradability and Mechanical Properties of Poly(vinylalcohol)-Based Blend Plastics Prepared Through ExtrusionMethod

Martina Kopcilova • Jitka Hubackova • Jan Ruzicka •

Marie Dvorackova • Marketa Julinova • Marek Koutny •

Miroslava Tomalova • Pavol Alexy • Peter Bugaj • Jaroslav Filip

Published online: 2 August 2012

� Springer Science+Business Media, LLC 2012

Abstract Plastic blend materials consisting of poly(vinyl

alcohol), glycerol and xanthan or gellan were prepared

through laboratory extrusion. Their base mechanical

properties were compared with the properties of poly(vinyl

alcohol) foil and their biodegradability in soil, compost and

both activated and anaerobic sludge were assessed. In

samples with lower polysaccharide content (10–21 %w/w)

the tensile strength of 15–20 MPa was found; the elonga-

tion at break of all blends was relatively close to the

parameter of poly(vinyl alcohol) foil. The biodegradability

levels of the blends tested corresponded to the content of

natural components, and the mineralization of the samples

with the highest carbohydrate proportion (42 %) reached

50–78 %, depending on the type of the environment.

Complete biodegradation of all samples occurred in acti-

vated sludge.

Keywords Poly(vinyl alcohol) � Xanthan � Gellan �Biodegradation

Introduction

One alternative for reducing the quantity of plastic waste is

to develop and manufacture new types or blends of

degradable polymers, which under different environmental

conditions are subject to the action of microorganisms,

light, oxygen, temperature and other factors. Biodegradable

plastics are the most important group of such polymers and

their decomposition by bacteria or fungi has been the

subject of intense research.

The group of biodegradable plastics used for manufac-

turing packaging and other materials includes poly(vinyl

alcohol) (PVA); however, it proves to be almost non-

degradable in some environments (for example, under

certain anaerobic conditions [1] or in soils and compost

[2]), either due to the absence of suitable microorganisms

or unfavourable environmental conditions. For instance,

the latter has been shown in a study by Chiellini et al., who

demonstrated the adsorption of PVA onto clay particles,

resulting in a substantial inhibition of biodegradation [3].

For these reasons, efforts should be in place to reduce

the proportion of PVA in plastics for certain applications.

One possibility is to prepare blends containing biopolymers

derived from renewable sources, such as proteins (colla-

gen), polyesters (poly-b-hydroxybutyric acid) and particu-

larly polysaccharides (starch, cellulose). The properties,

applications and biodegradability of such materials have

been explored in several studies [4–7]. Bacterial polysac-

charides, within biodegradable plastics, have not yet been

studied because of the high costs involved. Nonetheless,

they allow for various alternatives of application due to

their different structure and properties compared to plant

polysaccharides. Bacterial polysaccharides are very diverse

in structure and application; in addition, some of them

are now produced commercially in large volumes, with

M. Kopcilova � J. Hubackova � J. Ruzicka (&) �M. Dvorackova � M. Julinova � M. Koutny � M. Tomalova �J. Filip

Department of Environmental Engineering,

Faculty of Technology, Tomas Bata University in Zlın,

TGM Square 275, 762 72 Zlın, Czech Republic

e-mail: ruzickaj@ft.utb.cz

J. Ruzicka � M. Julinova � M. Koutny

Centre of Polymer Systems, TGM Sqr. 5555,

760 01 Zlın, Czech Republic

P. Alexy � P. Bugaj

Department of Plastics and Rubber, Institute of Polymer

Materials, Slovak University of Technology, Radlinskeho 9,

812 37 Bratislava 1, Slovak Republic

123

J Polym Environ (2013) 21:88–94

DOI 10.1007/s10924-012-0520-8

xanthan and gellan being the most industrially applied—in

food, pharmaceuticals and cosmetics—whilst xanthan is

also utilized in some technical spheres.

In fact, blending PVA with xanthan or gellan was used

in several studies aimed to a preparation and utilization of

films, hydrogels or microspheres for certain medical

applications. In these cases solvent evaporation method or

emulsion cross-linking method were applied for obtaining

biodegradable polymer matrices for controlled drug deliv-

ery [8–11]. Nevertheless, these preparation methods are not

a way for the production of biodegradable plastics intended

for various technical applications; moreover, materials

biodegradation in different environmental spheres was not

tested in any above mentioned study.

Generally, during polymers mixing the possibility of

mutual interaction between individual blend components

exists and thus the potential to influence the biodegradability

of the resultant material as well. In the case of PVA and

gellan, interaction was detected by Sudhamani et al. [12],

who studied the mechanical properties of several blends of

these two polymers. DSC thermogram data of PVA ? gel-

lan foils, prepared through the casting method, showed that

their glass transition temperature and melt isotherm shifted

towards a higher temperature with increasing proportion of

PVA; therefore, it was concluded that molecular interac-

tions between PVA and gellan had occurred [12].

For these reasons, the target of this study has been to

prepare, identify the base mechanical properties and test

the biodegradability of polymer blends of PVA ? gellan

and PVA ? xanthan, as prepared through plasticization of

basic ingredients with subsequent extrusion under indus-

trial conditions (i.e. temperatures). The results of the bio-

degradability of these blends under anaerobic conditions

have been published by Hrncirik yet and compared to PVA

blends containing starches [13]. This paper presents the

complete results of microbial degradability in various

environmental conditions and the base mechanical prop-

erties of the plastics, and contrasts these with the properties

of pure PVA or PVA foil. In addition to these, FTIR

spectra of all base component and the final blends were

measured and discussed.

Experimental

Chemicals

Poly(vinyl alcohol), PVA (Mowiol 5–88, Kuraray): total

carbon content 50.8 %, viscosity 5.5 ± 0.5 mPa s, degree

of hydrolysis 88 %

Gellan (Gellan gum, Fluka): total carbon content

31.3 %, CODCr 1,355.9 mg g-1

Xanthan (Xanthan gum, Fluka): total carbon content

31.3 %, CODCr 905.6 mg g-1

Glycerol (H.C.I. Comp.): total carbon content 39.1 %

Polymer Blends

The preparation of samples and the evaluation of their

mechanical properties were performed by the Department

of Plastics and Rubber, Institute of Polymer Materials at

the Slovak University of Technology in Bratislava. All the

polymer blends were prepared in two steps. Firstly, mix-

tures of both PVA ? glycerol and polysaccharide ?

glycerol were made ready, exposed at 130 �C for 15–45

min and cooled. Afterwards, plasticized PVA was mixed

with plasticized polysaccharide and the blend was treated

on a twin-screw Labtech extruder under the thermal pro-

file of 120–130–140–150–160–170–180–190–160–150 �C

(feed hopper-extrusion head). The screw diameter of

16 mm, L/D ratio of 40 and extruder speed of 300 rpm

were further parameters. The compositions of all final

polymer blends are given in Table 1.

Mechanical Properties of Polymer Blends

In order to measure mechanical properties, dumb-bell

shaped specimens were prepared from all the blends. Tests

for determining tensile strength and elongation at break

were performed on a 5 kN Metrotest according to the norm

ISO 527, using a crosshead speed of 1 mm min-1 to the

extent of deformation of 0–3 % and -50 mm min-1 at the

deformation [3 %, all at 25 �C [14].

Table 1 Composition of final

polymer blendsComponent Polymer blend

PVA/G10 PVA/G21 PVA/G42 PVA/X10 PVA/X21 PVA/X42

Glycerol [%] 14.7 17.4 25.2 14.7 17.4 25.2

Gellan [%] 10.5 21 42 – – –

Xanthan [%] – – – 10.5 21 42

PVA [%] 74.8 61.6 32.8 74.8 61.6 32.8

J Polym Environ (2013) 21:88–94 89

123

Determining Biodegradability in Anaerobic Mesophilic

Sludge

Preparation of inoculum: Anaerobic sludge from a local

wastewater treatment plant was centrifuged (5,0009g,

20 �C, 10 min), washed by nitrogen-bubbled water and,

following repeated centrifugation, suspended in mineral

medium [15] to reach 3–4 g L-1 of dry mass.

Testing: Evaluations were performed according to the

ISO 11734 [15], on the basis of the amounts of CH4 and

CO2 produced during the tests. Portions of 100 ml of

resuspended anaerobic sludge were placed in 250 ml vol-

ume flasks, thoroughly bubbled with nitrogen and then

20 mg of sample was added into each flask, excluding

blanks. After repeated nitrogen bubbling, all the flasks

were sealed with caps equipped with a gas-tight sampling

valve. Incubation was performed at 35 �C and the gas

phase of each flask was sampled several times per week.

CH4 and CO2 concentrations were determined by gas

chromatography (CHROM 5 equipped with a PORAPAK

Q column and TCD detector, with Helium as a carrier gas,

Tsample = 100 �C, Tt = 50 �C, Tdet = 100 �C). At the end

of each test, a concentration of inorganic carbon (IC) was

determined in liquid phase using an automatic TOC ana-

lyzer (Shimadzu 5000A). All the tests were conducted in

triplicate.

The final level of sample biodegradation was evaluated

by the relation of the amount of carbon released in the form

of both gas products (CH4 and CO2) and liquid compounds

(IC), corrected by a blank, to a theoretical amount of car-

bon in the sample, and expressed in terms of percent

mineralization.

Determining Biodegradability in Activated Sludge

Preparation of inoculum: Activated sludge from a local

wastewater treatment plant was centrifuged (5,0009g,

20 �C, 10 min) and washed three times with drinking

water. The required volume was centrifuged again and the

biomass was suspended in mineral medium [16] to reach

0.5 g L-1 of dry mass.

Testing: Respirometric determination according to the

Czech EN ISO 9439 norm [16] was employed, utilizing a

Micro-Oxymax respirometer (Columbus Instruments Co.,

USA). Samples of concentrations of 0.2 g L-1 were used

and reactor flasks were placed in a water bath at 25 ± 1 �C.

CO2 production and O2 consumption were periodically

measured.

A ratio of the CO2 actually produced (corrected by a

blank) to the theoretical quantity given by the carbon

content in the sample was employed and the biodegrada-

tion was expressed in terms of percent mineralization.

Determining Biodegradability in Compost

Preparation of inoculum: Commercial compost produced

by the AGRO CS Comp. was used throughout the study. It

was sieved through a screen of approximately 0.7 cm mesh

and left to mature for about 6 weeks at 58 �C, 50 %

humidity and under continuous aeration. After this period,

dry matter of 55.17 % and pH 6.85 were found.

Inert material: Agroperlite (AGRO CS Comp.) was used

for maintaining humidity and increasing the homogeneity

of the mixture. Water content \ 2.0 %, pH 6.0–7.5.

Mineral medium: Composition (in g per litre): KH2PO4

1.64, K2HPO4.12H2O 4.35, Na2HPO4.12H2O 8.94,

(NH4)2SO4 0.50, CaCl2 0.275, MgSO4.7H2O 0.225,

FeSO4.7H2O 0.003 and 1 ml of trace element solution

(MnSO4.4H2O 0.043, H3BO3 0.057, (NH4)6Mo7O24.4H2O

0.037, CuSO4.5H2O 0.040, Co(NO3)2.6H2O 0.025,

ZnSO4.7H2O 0.043).

Testing: A modification of the Czech EN ISO 14885-2

norm [17] was used. All the tests were conducted in gas-

tight flasks with 1,140 ml of total volume. A mixture of

10 g of compost dry matter and 20 g of Agroperlite was

dosed into the each test flask. Each sample (1.7 g) was

dissolved in 20 ml of mineral medium and added into the

flask. Blank bottles without a sample were prepared in

parallel. All reaction flasks were sealed with caps equipped

with a gas-tight sampling valve and incubated at 58 �C in

the dark. Concentrations of CO2 and O2 were determined

twice a week using an Agilent 7890A gas chromatograph

equipped with a Porapak Q column (80/100 MESH) and a

5A molecular sieve (60/80 MESH), with a TCD detector.

Aeration of all the flasks via CO2-free air was performed

after each sampling attempt and water content was checked

by weighing every entire bottle.

CO2 production was calculated for each flask, corrected

by a blank and compared to carbon content in each sample.

The level of biodegradation was expressed in terms of

percent mineralization.

Determining Biodegradability in Soil

Preparation of inoculum: Three soil types (commercial

garden soil and two types of agriculture soil) were sieved

through a screen of 0.7 cm, mixed at the ratio 2:1:1 and

kept at 5 �C and humidity of 50 %. After this, dry matter of

50.4 % and pH 6.2 were found.

Testing: A modification of the ISO 17556 method [18]

was used. All the tests were carried out in gas-tight flasks

with a total volume of 1,140 ml. 30 g of soil mixture and

30 g of Agroperlite (see above) were dosed into each flask

and 0.6 g of sample (dissolved in 20 ml of water) was

added. Solutions of (NH4)2SO4 and K2HPO4 were added to

reach the C:N:P ratio of 100:10:1. Blank bottles without

90 J Polym Environ (2013) 21:88–94

123

samples were prepared in parallel. All the flasks were

sealed with gas-tight caps equipped with a gas-tight sam-

pling valve and incubated at 25 �C in the dark. The process

of determining the CO2 and O2 concentrations, aerating the

flasks as well as evaluating biodegradability was carried

out in an identical manner to the compost tests.

Obtaining FTIR Spectra

FTIR-ATR spectra of the PVA, xanthan, gellan and blend

foils were measured using the Nicolet iS10 instrument

(Thermo Scientific, USA) with the ATR Smart MIRacleTM

adapter containing a diamond crystal, the spectral range

being 4,000–525 cm-1, resolution 4 cm-1, and the number

of scans 32. The spectra obtained were processed via

Omnic 8 software (Thermo Scientific, USA).

Results and Discussion

Base Mechanical Properties of the Blends

The results of measuring the base mechanical properties of

the plastics produced are shown in Table 2. As expected,

all the blend samples showed lower tensile strength com-

pared to PVA foil, with the rate of the decrease corre-

sponding to an increasing proportion of polysaccharides.

The samples containing xanthan reached approximately

half of the value of strength compared to PVA. Regarding

the values of elongation at break, blends containing 10.5

and 21 % of polysaccharides demonstrated properties rel-

atively close to pure PVA and only those samples con-

taining 42 % of polysaccharides proved markedly fragile.

A comparison of the mechanical properties of the blends

showed that using xanthan was more favourable, this is

because adequate samples of gellan always produced

slightly worse results.

Biodegradability of PVA, Xanthan and Gellan

Firstly, the biodegradability of all the basic components

under the conditions studied were observed. The results

obtained are summarized in Table 3.

In accordance with previous papers [2, 19], PVA was

found to be completely degradable in activated sludge over

18 days; after a acclimation period lasting several days

final CO2 production equalled 72 %. Further tests of PVA

biodegradation in compost and soil, as well as in meso-

philic anaerobic sludge, proved its low degradability under

these conditions. The data observed showed that, in these

cases, PVA mineralization did not exceed values corre-

sponding to the content of residual acetate groups. Similar

results have formerly been described by Gartiser and

Chiellini [1, 2]; these all indicate the need to lower the

amount of waste containing PVA entering such environ-

ments.

Important differences were observed in the biodegrad-

ability of the two polysaccharides studied. Whereas xan-

than revealed complete biodegradability in all the

environments tested, gellan was proven to gradually

degrade in the compost and soil tests. The course of its

biodegradation in soil was characterized by an acclimation

period of nearly 1 month in length followed by partial

degradation phase, suggesting a low number of degrading

microbes in the soil used. Quite a different degradation

curve was noted in the gellan compost test. The carbohy-

drate was continuously and slowly degraded, so that after

2 months the level of CO2 production reached only 40 %,

compared to nearly 98 % of CO2 production originating

from xanthan decay. In aerobic and mesophilic anaerobic

sludge, similar levels of biodegradation for both carbohy-

drates were found, where over 80 % of CO2 production

and 60 % of carbon mineralization, respectively, were

determined.

Biodegradability of Polymer Blends

All the polymer blends prepared were tested for biode-

gradability in the same way as the individual components;

the results of these tests are summarized in Fig. 1. As

expected, for all blend types, the best biodegradability was

observed in activated sludge, without any evident accli-

mation period. Under such condition due to mixed char-

acteristics of the samples immediate CO2 production from

glycerol mineralization arose, followed by consecutive

degradation of the other two components making a certain

step-like characteristic of all the curves (data not shown).

The biodegradability of the samples in all other envi-

ronments was influenced by the low degradability of PVA

under the given circumstances; however, all the results

clearly indicate that the degree of blend mineralization

corresponded to the proportion of natural components.

Therefore, the highest values originated from samples with

Table 2 Base mechanical properties of the final polymer blends and

PVA foil

Tensile strength [MPa] Elongation at break [MPa]

PVA 35.8 ± 0.68 161.9 ± 14.55

PVA/G10 16.8 ± 1.25 141.6 ± 29

PVA/G21 14.3 ± 0.31 126.7 ± 37.27

PVA/G42 12.2 ± 0.63 10 ± 1.0

PVA/X10 20 ± 0.59 205 ± 52.18

PVA/X21 17.5 ± 0.20 134.2 ± 14.9

PVA/X42 15 ± 0.94 20 ± 1.5

J Polym Environ (2013) 21:88–94 91

123

a 42 % proportion of polysaccharides. This especially

applies to the PVA/X42 sample, for which the results from

anaerobic mesophilic sludge and compost showed miner-

alization at 60 %, while for the soil environment this value

was only about 50 %. Lower levels of decomposition were

found in blends containing 21 % of polysaccharides, where

the balance of the biodegradation products showed rates of

mineralization from 28 to 35 % for the PVA/X21 sample

and 21–25 % for the PVA/G21 sample, depending on the

type of environment. For the blends containing 10.5 % of

polysaccharides, the mineralization results not exceeded

25 %.

Increasing the degree of mineralization of samples with

an increased proportion of natural components indicates an

important characteristic of blends prepared by extrusion.

This concerns the fact that in the plastic materials so pro-

duced there are no interactions between the polymers,

which would prevent biodegradation of natural compo-

nents. This was clearly visible in the PVA blends with

xanthan, where the values identified of the samples’ min-

eralization corresponded to the relative representation of

polysaccharide and glycerol in different types and showed

that it was only poly(vinyl alcohol) which remained a non-

decomposed component in soil, compost and anaerobic

sludge. These assumptions were confirmed by the results of

the diluted organic carbon found in supernatant liquors at

the end of tests in anaerobic sludge, since the DOC con-

centrations corresponded to the proportion of PVA in the

samples weight and the volume of the sludge suspension

used (data not shown).

FTIR Characterization

Infrared spectra of PVA, xanthan, gellan and final blends

are shown in Figs. 2 and 3. In FTIR spectrum of pure PVA

major bands related to hydroxyl and acetate groups are

present. The broad band observed at 3,300 cm-1 is asso-

ciated with the O–H stretching vibrations from the inter-

molecular and intramolecular hydrogen bonds. The

vibration band observed at 2,909 cm-1 refers to the C–H

stretching vibrations from alkyl groups. The bands at 1,731

and 1,245 cm-1 are associated to the C = O stretching

vibrations and C–O–C functional groups, respectively,

originating from remaining acetate groups [20].

FTIR spectrum of xanthan shows strong band at

3,300 cm-1 due to O–H stretching vibrations and two

carbonyl bands at 1,723 cm-1 corresponding to acetate or

Table 3 Biodegradability of

pure PVA, xanthan and gellan

under differing conditions

(mean ± SD, for n = 3 or 4)

Mineralization [%]

Activated sludge Anaerobic sludge Compost Soil

Test time 20 days 34 days 47 days 48 days

Gellan 86.92 ± 1.32 72.69 ± 3.85 35.21 ± 1.88 35.78 ± 1.40

Xanthan 91.39 ± 0.96 77.00 ± 0.67 97.76 ± 0.29 76.12 ± 1.83

PVA 68.13 ± 0.96 8.28 ± 0.17 8.48 ± 0.10 B1

Fig. 1 Mineralization of all

polymer blends under differing

conditions (mean ± SD, for

n = 3 or 4)

92 J Polym Environ (2013) 21:88–94

123

pyruvate groups, respectively, and at 1,600 cm-1 charac-

teristic of a carboxylate group [21].

FTIR spectrum of the pure gellan shows very large band

at 3,312 cm-1 corresponding to O–H stretching vibrations

from hydroxyl groups. The bands located in the range

2,882–2,926 cm-1 can be assigned to the CH3 and CH2

stretching vibrations groups. In the wavenumber regions

from 700 to 2,000 cm-1, a band at 1,600 cm-1 is attributed

to glycosidic bond and that at 1,404 cm-1 is associated to

the C–H bending [22]. The bands at 1,023–1,149 cm-1 are

due to ethereal and hydroxylic C–O stretching, respectively

[23].

In FTIR spectra of final blends the adsorption peaks at

1,600 cm-1 proportional to the xanthan or gellan content

are clearly visible, while the peaks at 1,731 cm-1 and at

1,245 cm-1, representing PVA ester groups, are reasonably

reduced. Similar trend is evident in the wavenumber region

of 1,100–1,000 cm-1 (C–O stretch and O–H bending).

Obtained results proved mixed character of the blends,

without formation of any new bonds; interaction in the

form of the hydrogen bonds between polysaccharides and

PVA in the blends described in the range of

3,000–3,500 cm-1 by Sudhamani et al. [12] were not by

our measures found.

Fig. 2 FTIR spectra of xanthan,

PVA and their blends

Fig. 3 FTIR spectra of gellan,

PVA and their blends

J Polym Environ (2013) 21:88–94 93

123

Conclusions

Plastic materials on the basis of poly(vinyl alcohol) that

contained xanthan or gellan were prepared. The results of

the base mechanical properties and biodegradability have

shown that, of the natural carbohydrate polymers, xanthan

was the more preferable type, as blends containing this

polysaccharide demonstrated more favourable properties

than samples with the same proportion of gellan. Even

though blends with a high proportion of carbohydrates

(42 %) were found to show a high degree of biodegrad-

ability, this occurred at the expense of their mechanical

properties. Therefore, PVA-based plastics with a content of

around 20 % of xanthan prepared through plasticization of

basic component with subsequent extrusion appear to be an

alternative for applications where maximum tensile

strength is not a requirement. Thus, such plastic materials

can help to reduce PVA inputs into the environment, where

PVA biodegradation proves rather limited.

Acknowledgments This work was supported by the Grant Agency

of the Czech Republic (GACR P108/10/0200) and also with support

from Operational Program Research and Development for Innova-

tions co-funded by the European Regional Development Fund

(ERDF) and the national budget of the Czech Republic, within the

framework of the project Centre of Polymer Systems (reg. Number:

CZ.1.05/2.1.00/03.0111).

References

1. Gartiser S, Wallrabenstein M, Stiene G (1998) J Environ Polym

Degrad 6:159

2. Chiellini E, Corti A, Politi B, Solaro R (1999) Polym Degrad Stab

64:305

3. Chiellini E, Corti A, Politi B, Solaro R (2000) J Polym Environ

8:67

4. Ishigaki T, Kawagoshi Y, Ike M, Fujita M (1999) World J

Microbiol Biotechnol 15:321

5. Kenawy ER, Cinelli P, Corti A, Miertus S, Chiellini E (1999)

Macromol Symp 144:351

6. Park JS, Park JW, Ruckenstein E (2001) J Appl Polym Sci

80:1825

7. Alexy P, Bakos D, Hanzelova S, Kukolikova L, Kupec J, Char-

vatova K, Chiellini E, Cinelli P (2003) Polym Test 22:801

8. Dumitriu CL, Popa M, Vasiliu S, Sunel V (2004) J Macromol Sci,

Pure Appl Chem 41:727

9. Agnihotri SA, Aminabhavi TM (2005) Drug Dev Ind Pharm

31:491

10. Kumar TMP, Umesh HM, Shivakumar HG, Ravi V, Siddara-

maiah (2007) J Macromol Sci, Pure Appl Chem 44:583

11. Ray S, Banerjee S, Maiti S, Laha B, Barik S, Sa B, Bhattacharyya

UK (2010) Drug Deliv 17:508

12. Sudhamani RS, Prasad MS, Udaya Sankar K (2003) Food Hy-

drocoll 17:245

13. Hrncirık J, Pseja J, Kupec J, Bernkopfova S (2010) J Polym

Environ 18:98

14. Slovak Standard STN ISO 527-2 (1998) Plastics: determination of

tensile properties. Slovak Standards Institute, Bratislava, Slovak

Republic

15. ISO 11734 (1998) Water quality: evaluation of the ultimate

anaerobic biodegradability of organic compounds in digested

sludge. Method by measurement of the biogas production. Inter-

national Organization for Standardization, Geneva, Switzerland

16. Czech Standard EN ISO 9439 (2001) Water quality: evaluation of

ultimate aerobic biodegradability of organic compounds in

aqueous medium. Carbon dioxide evolution test. Czech Institute

for Standardization, Praha Czech Republic

17. Czech Standard EN ISO 14855-2 (2008) Determination of the

ultimate aerobic biodegradability and desintegration of plastic

materials under controlled composting conditions: method by

analysis of evolved carbon dioxide. Czech Institute for Stan-

dardization, Praha Czech Republic

18. ISO 17556 (2003) Plastics: determination of the ultimate aerobic

biodegradability in soil by measuring the oxygen demand in a

respirometer or the amount of carbon dioxide evolved. Interna-

tional Organization for Standardization, Geneva, Switzerland

19. Hoffmann J, Reznıckova I, Kozakova J, Ruzicka J, Alexy P,

Bakos K, Precnerova L (2003) Polym Degrad Stab 79:511

20. Mansur HS, Costa ED, Mansur AAP, Barbosa-Stancioli EF

(2009) Mater Sci Eng C-Mater Biol Appl 29:1574

21. Hamcerencu M, Desbrieres J, Popa M, Khoukh A, Riess G (2007)

Polymer 48:1921

22. Noor ISM, Majid SR, Arof AK, Djurado D, Claro Neto S,

Pawlicka A (2012) Solid State Ion (in press)

23. Lee MW, Chen HJ, Tsao SW (2010) Carbon Polym 82:920

94 J Polym Environ (2013) 21:88–94

123