ACS Polyolefin Workshop in Tribute to Professor James E. McGrath Functionalization of Polypropylene for Energy Storage Application T. C. Mike Chung Department of Materials Science and Engineering The Pennsylvania State University University park, PA 16802 USA
Outline Introduction: Energy Storage Crosslinked PP (x-pp) PP Bonded Hindered Phenol (PP-HP) Conclusion ONR-MURI (UConn, Columbia, RPI, Akron, Penn State)
PP in Energy Storage Applica2ons Lithium Ion Ba-eries Polymer Film Capacitors Porous PP Separator Metallized BOPP Specialty applica2ons require mul2ple performance func2ons
State- of- the- Art PP Capacitors +Q -Q Cases Dielectric constant (ε) Breakdown strength (E: MV/m) Energy density (J/cc) BOPP 2.2 500 2 Target 4.4 1000 16 Energy Density = ½ εε o E 2 BOPP Research Goal: Increase dielectric constant (ε) Increase breakdown strength (E) Increase high temperature stability (T) Maintain Low energy loss (tansδ)
Functional Polypropylene CH 3 (CH 2 -CH) x (CH 2 -CH) y -OH -NH 2 -NH 3 + A - Dipolar Ion Pair π- Electrons Crosslinking Stabilizer (CH 2 ) n X Increase dielectric constant Increase breakdown strength Increase mechanical strength Increase high temp. stability Maintain low energy loss "Functionalization of Polyolefin" Academic Press, 2002
Crosslinked Polyethylene (x- PE) x- PE has been widely used in heat- resis2ng wires, high voltage cables, and hip replacements for many years. Cross- linking offers advantages of increasing temperature stability and resistance to electrical discharge, solvents, creep, and stress- cracking. Free radical mechanism Silane-moisture cure mechanism Irradiation (γ-ray or electron beam) or peroxide-induced CH 2 CH 2 * CH CH 2 (CH 2 -CH 2 ) (CH 2 -CH) x y Hydrolysis and coupling R-O-Si-O-R O R x-pe x-efficiency <80% ill-defined structures Both mechanisms can not be applied to PP and high α-olefin polymers
New Crosslinking Mechanism (CH 2 ) n [2+4] cycloaddition CH=CH 2 Polyolefin Containing Pendant Styrene Units Processible Copolymer Simple and Effective Crosslinking Reaction No External Chemical and By-product How to prepare polyolefin containing Pendant Styrene Units?
Copolymeriza2on Reac2ons A H 2 B LCB-PP x-pp Macromolecules 2007, 40, 2712 Macromolecules 2009, 42, 3750
Thermal Cross- linking Reac2on BSt contents: (a) 0.42 mol% (b) 0.73 mol%, and (c) 8,6 mol% PP-BSt with BSt contents 0.42 mol% thermally treated at 200 o C PP-BSt exhibits an effective thermal cross-linking reaction via the regiospecific [2+4] inter-chain cycloaddition reaction. No external reagent and No by-product.
High Field Breakdown Strength (a) PP, (b) x-pp-1, (c) x-pp-2, and (d) x-pp-3 (solution-cased films) Cross-linking Effects: increase breakdown strength (E) narrow breakdown distribution high thermal stability (>200 o C) Applied Phys. Lett. 2011, 98, 62901
Brief Summary Selec2ve mono- enchainment of butylenestyrene comonomer by selec2ve metallocene catalyst forms crosslinkable PP with pendant styrene units (PP- BSt). [2+4] Cycloaddi2on between two pendant styrene units is an effec2ve x- mechanism without external reagent and by- product. x- PP films shows good stability under extreme environment (temp., electric field, solvent, etc.) x- PP film offers high breakdown strength (E) and high energy storage 10 J/cc, about 5 2mes higher than current PP capacitors, and no energy loss.
Outline Introduction: Energy Storage Crosslinked PP (x-pp) PP Bonded Hindered Phenol (PP-HP) Conclusion
Thermal/Oxida2ve Degrada2on Macromol. Chem. Phys. 2001, 202, 775
Hindered Phenol Stabilizers Major Concerns: Incompatibility Low concentration Diffusion, evaporation Long term protection Dielectric loss Macromolecules 2015, 48, 2925-2934
PP- OH Copolymers CH 3 CH 2 =CH + CH 2 =CH (CH 2 ) 4 B R R TiCl 3.AA/Et 2 AlCl CH 3 (CH 2 -CH) (CH 2 -CH) x y (CH 2 ) 4 B R R NaOH/H 2 O 2 CH 3 (CH 2 -CH) (CH 2 -CH) x y (CH 2 ) 4 O H Dielectric Constant Dielectric Loss PP-OH-1: 0.7 mol% OH PP-OH-2: 1.8 mol% OH PP-OH-3: 4.2 mol% OH Macromolecules 2010, 43, 4011; Macromolecules 2013 46, 5455.
Steglich Esterifica2on Reac2on PP-OH PP-HP Effective estification No change in semi-crystalline morphology Macromolecules 2015, 48, 2925-2934
TGA Thermographs (in air) (Heating rate of 20 o C/min) PP-HP shows higher stability (>300 o C) about 50 and 90 o C higher than commercial PP and pristine PP, respectively.
TGA Thermographs (in Air) (Heating rate of 20 o C/min)
TGA Thermographs in air (Heating rate of 20 o C/min) PP-HP Polymers PP/PP-HP(4.7%) Blends PP thermal/oxidative degradation temperature is proportional to the HP (antioxidant) content in PP-HP copolymer.
PP- HP/PP Co- crystalliza2on Co-crystallization happens in PP/PP-HP blend with single and reduced melting and crystallization temperatures.
D- E Loops UConn (Yang Cao) Random PP-OH (5.7%) The Corresponding Random PP-HP
Summary A chemical route has been developed to prepare PP- PH polymeric an2oxidant. PP- HP shows significantly higher thermal and long- term stability than pure PP (>100 o C) and commercial PP with an2oxidant (>50 o C). The degrada2on temperature is propor2onal to HP content. Co- crystalliza2on of PP- PH with PP allows homogeneous distribu2on of the immobilized HP moie2es in PP matrix. PP- HP dielectric shows several desirable dielectric proper2es, with higher dielectric constant, low dielectric loss, high breakdown strength, high temp. stability, high energy density.
Associate/Assistant Professor Opening Polymer Science and Engineering The Department of Materials Science and Engineering (MatSE) at The Pennsylvania State University invites applicajons for a tenure- track faculty posidon at the Associate or Assistant Professor level to begin as early as July 1, 2016. The broad area of interest for this hire is polymer science and engineering, and outstanding candidates specializing in polymer chemistry, self- assembly, polymer membranes, energy materials and electronics are especially encouraged to apply.