European Community for the financial support in the frame of the IINTERREG. IV - NANOLAC ... mentioned companies for supplying raw materials. This work has ... PLA was supplied by NatureWorks LLC as grade (4032D) for realization of ...
Tailoring the Properties of PLA - ZnO Nanocomposites Using Selected Additives Marius Murariu, Leila Bonnaud, Emmanuel Duquesne, Yoann Paint, Jean-Marie Raquez and Philippe Dubois
Laboratory of Polymeric and Composite Materials, Center of Innovation and Research in Materials & Polymers (CIRMAP), Materia Nova Research Center & University of Mons, 20 Place du Parc, 7000 - Mons, Belgium Introduction Polylactide (PLA), a polyester produced from renewable resources, has a key-position in the market of biopolymers for various applications (biomedical, packaging, fibers, technical parts). Following the R&D studies accomplished by CIRMAP, for the first time was reported production of PLA- ZnO nanocomposites (via melt-blending technology and using a specifically treated nanofiller to limit polyester degradation). These new nanocomposites have been successfully extrapolated in the production of fibers, films or other items, showing multifunctional properties (anti-UV, antibacterial, barrier, etc.) For some applications, these nanocomposites could have limitations (low ductility and crystallization rate, relatively low stability at high temperature and long residence time), which will all affect their processing and final performances. The aim of this communication is to assess that the properties of PLA - ZnO nanocomposites can be “tailored” with selected additives (chain-extenders, nucleating agents, plasticizers). (M. Murariu and Ph. Dubois, Advanced Drug Delivery Reviews, 2016, 107, p. 17)
Materials
PLA was supplied by NatureWorks LLC as grade (4032D) for realization of films (Mn(PS) = 133500, dispersity (Mw/Mn) =1.94, D-isomer = 1,4%). Silane treated ZnO nanofiller (ZnO(s)) was supplied by Umicore Zinc Chemicals (Belgium) as Zano 20 Plus (surface treated with triethoxy caprylylsilane, ZnO 96%). Ultranox 626A was selected as thermal stabilizer and used at preferred percentage of 0.3 wt-% in PLA.
Additives used to design the properties of nanocomposites a. Joncryl ADR- 4300F was kindly supplied by BASF as PLA chain extender (CE) with mild-epoxy functionality (Mw= 5500, epoxy equivalent by weight 445 g/mol). b. Phenylphosphonic acid zinc (PPA-Zn) with the trade name Ecopromote was kindly supplied by Nissan Chemical Industries and used as nucleating agent (NA) for PLA. c. Tributyl citrate (TBC) (Acros Organics) was used as plasticizer and also to promote PLA crystallization.
Murariu, M., et al., Current progress in the production of PLA– ZnO nanocomposites, J. Appl. Polym. Sci., 2015, 132, 42480.
Traditional DSC & isothermal crystallization tests suggest powerful nucleation ability and high kinetics for PLA(ZnO/PPA-Zn) systems. Nanocomposites very interesting for application, improved crystallization & processing…
Results and discussion
Key-role of selected additives in nanocomposites
DSC analyses of PLA - 3% ZnO nanocomposites
Why Joncryl as CE?. Especially at high ZnO loading, following the long In all cases improved thermal stability, possibility of processing at higher temperature
Weight (%)
100
80
220 °C
PLA- 5% ZnO[s] PLA- 5% ZnO[s]- 1% Joncryl
30
50 Time (min)
Χc ~ 45%
DSC cooling
crystallization ability required for some applications. Amazing degree (40-50%) and rate of crystallization can be obtained by co-adding 0.5-1% NA…
For applications requiring high ductility and impact strength, addition of plasticizers such as TBC, could be beneficially and of interest also where certain crystallization properties are mandatory…
TGA under isothermal conditions (at 220 °C & 240 °C) 40 10
Adding 1% NA,
Nucleating agents (NA) and PPA-Zn : PLA & PLA-ZnO don’t show the
(under air)
240 °C
60
residence time at high temperature, is quite difficult to limit the decrease of molecular weights and degradation of PLA even using nanofiller treated by silanes. Glycidyl functions (from CE) can react with both end groups of PLA leading to high molecular weight polymer, beneficial effects on rheological, thermal and mechanical properties…
(Films ~100 microns Sec DSC heating, thickness) 10°C/min
Mechanical properties of PLA - ZnO nanocomposites
70
(ASTM 638, v= 1 mm/min, specimens type V)
Universal V4.5A TA Instruments
Sample
UV-vis spectra of PLA and PLA-ZnO nanocomposites
Young’s
Strain at
strength, MPa
modulus, MPa
break, %
62 (± 1)
2300 (± 150)
PLA- 3% ZnO
ZnO is giving protection to UV radiation
(Films of 100- 150 microns thickness)
TEM C 73C PLA 3% ZnO 20% TBC
Max. tensile
4.9 (± 0.2)
PLA- 3% ZnO-
65
2250
6.6
1% CE
(± 2)
(± 250)
(± 3.0)
PLA- 3% ZnO-
66
2600
4.2
1% NA
(± 2)
(± 100)
(± 0.4)
PLA- 3% ZnO-
33
1850
200
15% TBC
(± 2)
(± 100)
(± 30)
Conclusions & Acknowledgements The properties of PLA-ZnO nanocomposites can be “tailored” using : a) chain-extenders, b) nucleating agents, c) plasticizers, other additives - PLA/ZnO(s)- CE : better thermal stability and processing, improved molecular & thermo-mechanical parameters, good nanofiller distribution, anti-UV properties… - Impressive PLA crystallization by the co-addition of 0.5-1% NA (PPA-Zn), flexibility, ductility and impact strength (adding 15-20% TBC), a promising progress that can open new perspectives for the application of PLA - ZnO nanocomposites
ZnO
Good distribution of ZnO NPs
TEM of PLA - 3% ZnO- 20% TBC
Authors thank the Wallonia Region, Nord-Pas de Calais Region and European Community for the financial support in the frame of the IINTERREG IV - NANOLAC project. They thank also to Anne-Laure Dechief, Oltea Murariu and Jérémy Capette for assistance in realization of experiments, and all mentioned companies for supplying raw materials. This work has been also supported by the European Commission and Wallonie – Convergence (TECHNOPOLY, POLYTISS projects), FEDER program 2014-2020 (Materia Nova, PROSTEM project - Multifunctional films, MACOBIO project – Low carbon Footprint).
