This document summarizes research into toughening poly(lactide) (PLA) through reactive extrusion with acryl-functionalized poly(ethylene glycol) (AcrylPEG). The addition of AcrylPEG improved ductility and impact resistance of PLA. Further addition of Lupersol101 (L101) initiator limited AcrylPEG migration and resulted in the formation of poly(AcrylPEG)-rich domains within PLA, improving mechanical properties. Soxhlet extraction showed an extracted low molecular weight AcrylPEG fraction and a grafted high molecular weight poly(AcrylPEG) fraction within PLA. This novel method effectively toughened PLA through in situ graft

1. PLA/AcrylPEG/L101 blend morphology
Reactive extrusion of poly(lactide) with low molecular weight acryl-functionalized poly(ethylene glycol).
An original and effective methodology to toughen poly(lactide)
Georgio Kfoury1, 2
, Fatima Hassouna1
, Valérie Toniazzo1
, Jean-Marie Raquez2
, David Ruch1
, Philippe Dubois2
1
Department of Advanced Materials and Structures (DAMS), Centre de Recherche Public Henri Tudor, rue Bommel 5 (ZAE Robert Steichen), 4940 Hautcharage, LUXEMBOURG
2
UMons Research Institut for Materials Science and Engineering, Laboratory of Polymeric and Composite Materials, University of Mons (UMONS), Place du Parc 23, 7000 Mons,
BELGIUM
State of the art
Poly(lactide) (PLA) is one of the most extensively studied biodegradable
thermoplastics derived from renewable resources. One of the main
drawbacks of PLA is its inherent brittleness, which limits its applications.
Plasticization of PLA with low molecular weight poly(ethylene glycol)
(PEG) is currently carried out to sustain this issue, but it results the
migration of plasticizer at high PEG loadings.
Conclusions
High grafting extent of AcrylPEG:
Formation of a low AcrylPEG oligomers (DP~7) fraction (extracted by Soxhlet) and a highly
grafted fraction of poly(AcrylPEG) in PLA (not extracted by Soxhlet)
Limited plasticizer migration after DMA
It comes out a much limited migration of the plasticizer, which needs to be quantified by further
physical aging.
Efficient plasticization/ductility and improved impact resistance with increasing L101
In situ generation of particular rubbery micro- and nano-domains : soft poly(acrylPEG)-rich cores
having an “immiscibility gradient” with surrounding PLA due to the grafting reaction.
Acknowledgments
Thanks to the AMS Department of CRP
Henri Tudor and the Laboratory of
Polymeric and Composite Materials (LPMC)
for the technical and scientific supports and
the Fond National de la Recherche (FNR) for
the financial support.
Molecular characterization
Original approach
In situ polymerization and free-radical grafting of acryl-
functionalized PEG onto PLA backbone via reactive
extrusion aims to reduce the migration of the plasticizer.
PLA
PLA/AcrylPEG/L101
PLA/AcrylPEG
Mechanical properties
Material/Blend
(compositions in wt. %)
Extracted ftaction
by Soxhlet (%)
Tg (°C)
DMA
Storage Modulus
E’ at 20°C (MPa)
Impact energya
(kJ/m2
)
Elongation at
breakb
(%)
PLA
PLA/L101 (99.5/0.5)
60 1800 3 4 - 5
PLA/AcrylPEG (80/20)
PLA/AcrylPEG/L101
(79.5/20/0.5)
18
8
35
40
800
1000
80
110
(No break)
250
200
Reactive extrusion (REx)
Drying PLA
under vacuum
at 60°C over
night
Dry PLA Dry material
AcrylPEG + L101
Compression moulding on a Carver
manual press :
Moulding Temperature = 180°C;
Moulding time = 10 min
REx under N2 co-rotating twin-
screw extruder DSM Xplore
(15cc):
Tmelt ~ 175°C; scew speed = 100
rpm; REx time = 5 min
0 1 2 3 4 5
0
2000
4000
6000
PLA/AcrylPEG (80/20 in wt %)
PLA/AcrylPEG/L101 (79.75/20/0.25 in wt %)
PLA/AcrylPEG/L101 (79.5/20/0.5 in wt %)
Extrusionforce(N)
Time (min)
PolyAcrylPEG
grafted on PLA
AcrylPEG
OligoAcrylPEG
(DP~7)
Efficient plasticization resulting in improved ductility and impact resistance with
increasing L101 amount
In the absence of L101, AcrylPEG migrated to the surface of the specimen after
DMA, while it was not the case in the presence of L101
Soft domains (after cryofracture) made of poly(acrylPEG) (core) surrounded with an
immiscibility gradient are observed due to the grafting of acrylPEG on PLA (shell)
Core-shell microdomains played a stress concentrator role and impact energy
dissipation  fracture inhibitors
6 8 10 12 14 16 18
Solid material after
Soxhlet Extraction
RIDresponse
Retention time (min)
PLA/AcrylPEG (80/20 wt. %)
PLA/AcrylPEG/L101 (79.75/20/0.25 wt. %)
PLA/AcrylPEG/L101 (79.5/20/0.5 wt. %)
Neat AcrylPEG
6 8 10 12 14 16 18
Solid material before
Soxhlet Extraction
RIDresponse
Retention time (min)
PLA/AcrylPEG (80/20 wt. %)
PLA/AcrylPEG/L101 (79.75/20/0.25 wt. %)
PLA/AcrylPEG/L101 (79.5/20/0.5 wt. %)
Neat AcrylPEG
6 8 10 12 14 16 18
Liquid extracted
fraction by Soxhlet
RIDresponse
Retention time (min)
PLA/AcrylPEG (80/20 wt. %)
PLA/AcrylPEG/L101 (79.75/20/0.25 wt. %)
PLA/AcrylPEG/L101 (79.5/20/0.5 wt. %)
Neat AcrylPEG
Formation of a low AcrylPEG
oligomers (DP~7) fraction
(extracted by Soxhlet)
Formation of a highly grafted
fraction of poly(AcrylPEG) in PLA
(not extracted by Soxhlet in
methanol)
Lupersol101 (L101)
715 nm
440 nm