PROCESSING OF BIODEGRADABLE BLENDS

ALEXY Pavol

Slovak University of Technology in Bratislava Faculty of Chemical and Food Technology

Institute of Polymer Material

Processing properties of chosen biodegradable polymers

Polymer Properties during melt processing

PVA

-high sensitivity to thermal degradation during melt processing - high viscosity of melt -good film forming properties in film blowing technology

PCL

-good thermal stability during melt processing -low viscosity of melt -slow crystallization

PHA

-very sensitive to thermal degradation -molecular weight and viscosity of melt decreas very fast during melt processing -final thin wall products are very brittle

PLA

-good thermal stability during processing in the melt -high sensitivity to moisture during melt processing -good film forming properties -physical ageing , high brittleness of thin wall products

STARCH -high sensitivity to thermal degradation -high viscosity of TPS

These properties affect:

Processing properties

Viscosity at given temperature and shear rate

Sensitivity to degradation under processing condition

Mechanical properties of melt

Morphology of polymer blend

Processing stability of polymer or polymer blend

Final properties of products (mainly mechanical)

Usually : -thermal analysis (DSC, TG, DTA)

-re-extrusion and MFI measurement

Processing stability of biopolymers – testing method

Processing stability of biopolymers and oscillation rheometry

Two basic possibilities of oscillation test mode: Frequency sweep Strain sweep

t

t

Shear rate increases with increasing of deformation

angle at constant frequency

Shear rate increases with increasing deformation

frequency at constant angle

Testing of processing stability using oscillation rheometry

0

500

1000

1500

2000

2500

3000

3500

4000

0 10 20 30 40 50

h* [

Pa.s

]

[1/s]

a) PLA, T = 190°C

Frequency sweep Strain sweep

0

200

400

600

800

1000

1200

0 10 20 30 40 50

h* [

Pa.s

]

[1/s]

b) PHB, T = 190°C

Frequency sweep Strain sweep

0

400

800

1200

1600

2000

0 10 20 30 40 50

h* [

Pa.s

]

[1/s]

c) PCL, T = 190°C

Frequency sweep Strain sweep

Testing of processing stability using oscillation rheometry

Degradation test at constant strain and constant frequency

0

1000

2000

3000

4000

5000

0 10 20 30

h*(

t) [

Pa

.s]

time [min]

PLA

PLA, 170 PLA, 180 PLA, 190

PLA, 200 PLA, 210

0

0,2

0,4

0,6

0,8

1

1,2

0 10 20 30

h*(

t)re

l

time [min]

PLA

PLA, 170 PLA, 180 PLA, 190PLA, 200 PLA, 210

Testing of processing stability using oscillation rheometry

Degradation test at constant strain and constant frequency

0

0,2

0,4

0,6

0,8

1

1,2

0 5 10 15 20 25

h*

rel

(t)

t [min]

T = 210°C

PLA PHB PE PP

20000

25000

30000

35000

40000

45000

50000

55000

0 200 400 600 800

MV [

g.m

ol-

1]

h*(t) [Pa.s]

0

0,2

0,4

0,6

0,8

1

1,2

0 2 4 6 8 10

h*

rel (t

)

time [min]

Testing of processing stability using oscillation rheometry

Effect of moisture on processing stability of PLA

0

50000

100000

150000

200000

250000

300000

350000

400000

0 0,2 0,4 0,6 0,8

Mv [

g.m

ol-

1]

Water content [%]

0.00%

0.05%

0.38%

0.65%

Testing of processing stability using oscillation rheometry

Effect of stabilizers on processing stability of PLA

0

0,2

0,4

0,6

0,8

1

1,2

1,4

0 5 10 15 20 25

h *

rel

(t)

time [min]

T = 170°C

PLA

PLA+S1

PLA+S2

Viscosity relations versus morphology of blends

10-6 10-5 10-4 10-3 10-2 10-1 100 101 102 103

103

102

101

100

10-1

Ca kr

it

m1/m2

dispergation

without dispergation s

RCa

.

Viscosity relations versus morphology of blends

Plasticizer content increasing

PLA/TPS blends containing various amount of plasticizer for starch (90%of starch)

Viscosity relations versus morphology of blends

PLA/TPS with regulator of starch viscosity at 50% of starch content

Effect of TPS viscosity modification on mechanical properties

0,00

10,00

20,00

30,00

40,00

50,00

0 0,2 0,4 0,6 0,8 1 1,2

y

[MP

a]

modifier conc. [wt.%] PLA/TPS/M

0

10

20

30

0 0,2 0,4 0,6 0,8 1 1,2

b [

MP

a]

modifier conc. [wt.%] PLA/TPS/M

0

50

100

150

200

250

300

0 0,2 0,4 0,6 0,8 1 1,2

e b [

%]

modifier conc. [wt.%] PLA/TPS/M

Conclusion

New method for processing stability of biodegradable polymers was described based on oscillation rheometry

Oscillation rheometry is suitable also for evaluation of efficiency of stabilisers for biodegradable polymers

Type of created morphology of biodegradable blend is strongly deterimined by processing conditions, mainly by viscosity ratio between blended polymers

In special cases of processing conditions the oriented structures can be created. This leads to reinforced sturctures with enhanced mechanical properties which cannot by

achieved by individual polymeric components of the blend.

Aknowledgement

Prof. Ivan Chodák, DrSc. Prof. Dušan Bakoš, DrSc. Prof. Ivan Hudec, PhD and my PhD. Students: Mirolava Mikušová Katarína Tomanová Michal Mihalík Roderik Plavec

Thank you