PVDF/PVDF-TRFE blends loaded with BaTiO3: from processing to performance testing

Oc obe 20 - 22, 2021, B no, Czech Republic, EU PVDF/PVDF-TRFE BLENDS LOADED WITH BATIO3: FROM PROCESSING TO PERFORMANCE TESTING 1Ma in CVEK, 1Mi osla MRLÍK, 1Jose OSIČKA, 1Danila GORGOL, 2Pa el TOFEL 1Tomas Ba a Uni e si y in Zlín, Uni e si y Ins i u e, Cen e o Polyme Sys ems, Zlín, Czech Republic, EU, [email p o ec ed] 2B no Uni e si y o Technology, Depa men o Physics, Facul y o Elec ical Enginee ing and Communica ion, B no, Czech Republic, EU h ps://doi.o g/10.37904/nanocon.2021.4327 Abs ac Conce ns su ounding he limi ed supply o ossil uels ha e been he subjec o much deba e. As o p omising solu ions, polyme s like poly( inylidene luo ide) (PVDF) ha e gained a en ion due o hei abili y o gene a e elec ical ene gy om he was e mechanical ib a ions. The ene gy ha es ing and ib a ion sensing po en ial o PVDF is howe e limi ed due o i s low con en o elec oac i e β-phase, which has o be inc eased by indi ec pos -p ocessing. Recen ly, a syne gis ic e ec was ound in PVDF di ec ly blended wi h i s i luo oe hylene copolyme (PVDF-T FE) due o s ong in e acial pola iza ion. In his s udy, we aim o u he inc emen he piezoelec ic pe o mance o PVDF/PVDF-T FE blends by inco po a ing a small amoun o BaTiO3 nanoc ys als ia a acile and scalable p ocessing ou e. The β-phase con en was moni o ed using FTIR and XRD. Mel heology expe imen s showed ha co-blending o PVDF-T FE as well as he addi ion o BaTiO3 sligh ly inc eased mel iscosi y and complex modulus. Despi e ha , heological da a sugges ed ha de eloped o mula ions can be p ocessed by con en ional echniques in ended o a la ge-scale p oduc ion. Mo e impo an ly, PVDF/PVDF-T FE bina y blends supplemen ed wi h BaTiO3 a e expec ed o exhibi supe io d33 compa ed o con en ional nea blends, which could make hem highly p omising o mode n ene gy ha es ing and senso - ela ed applica ions. Keywo ds: Nanohyb id, ib a ion sensing, PVDF, blending, d33, piezoelec ici y 1. INTRODUCTION The inc easing demand o he elec ical ene gy and deple ion o ossil uels a e highly conce ning ac s o he p esen ime [1]. The ene gy ha es ing sys ems ep esen an al e na i e concep o add ess his challenge by con e ing he was e mechanical ene gy, such as ib a ions, ai / luid mo emen , body mo ion e c., in o he use ul elec ical o m [2]. Fo his pu pose, piezoelec ic ma e ials a e well-sui ed since hey spon aneously pola ize when subjec ed o a mechanical s ess [1,3]. Al hough he ene gy nanogene a o s based on a ious ino ganic ma e ials (BaTiO3, ZnO, InN, GaN, CdS) o ce amics (NaNbO3, KNbO3) ha e shown high piezoelec ic coe icien s, hey a e b i le, hea y and di icul o p ocess [4]. These d awbacks can be elimina ed/ educed by using e oelec ic polyme s, mainly poly( inylidene luo ide) (PVDF) and i s copolyme s wi h i luo oe hylene (PVDF-T FE) [5] o hexa luo op opylene (PVDF-HFP) [6]. PVDF is a semi-c ys alline polyme exis ing in i e phases (α-, β-, γ-, δ- and ε-) depending on he p ocessing ou es and pos - ea men . The α- and ε-phases a e easily accessible di ec ly om polyme mel [7], hey a e howe e non-pola due o ans-gauche con o ma ion sel -canceling he dipoles [5]. The γ- and δ-polymo phs a e pola o some ex en , and hence piezo- and e oelec ic [8]. While γ-phase PVDF is ha dly accessible om α-phase using spa ially con ined sys ems; he α- o δ-phase changeo e can be ealized by so-called elec o o ming p ocess unde elec ic ields (~150 kV/mm) [5,8]. The mos desi able phase o he cons uc ion Oc obe 20 - 22, 2021, B no, Czech Republic, EU o ene gy ha es ing and sensing de ices, i.e. β-phase, can be ob ained om α-phase by s e ching (uniaxial o biaxial) a he ele a ed empe a u es [9,10], and/o by polling o PVDF ilms unde s ong elec ic ields (abo e 500 kV/mm) [5, 11]. Con a y o PVDF, he copolyme PVDF-T FE c ys alizes di ec ly in o he elec oac i e β-phase ega dless he p ocessing condi ions o pos - ea men . Besides, PVDF-T FE shows an inc eased chain mobili y enabling o each c ys allini y o up o 90%, compa ed o PVDF ha a ains he maximal c ys allini y o ~50% [5]. A p esen , he use o PVDF-T FE is limi ed due o i s complica ed syn hesis, which is e lec ed in high p ice, and ela i ely na ow wo king empe a u e ange [12]. F om hese easons, co-blending s a egy was adop ed o syne gis ically combine p ope ies o he indi idual componen s. PVDF/PVDF-T FE blends we e ound o be immiscible in he c ys alline phase [13], howe e , hei miscibili y on he lamella le el was la e con i med due o co-exis ing mixed amo phous phase [14]. Meng e al. [5] ound ha mino amoun s o PVDF-T FE signi ican ly inc eased β-phase con en o PVDF, e en beyond he ule-o -mix u es. This syne gism wi h o igins in he in e acial pola iza ion esul ed o a la ge dielec ic cons an o PVDF/PVDF-T FE when compa ed o pu e componen s. O he s a egy o enhancing he piezoelec ic ac i i y o PVDF is based on he inco po a ion o small amoun s o a ious nano ille s [15,16] o main ain lexibili y o he PVDF senso s, and e en enhance hei he mal s abili y [6]. Despi e signi ican p og ess, a li le a en ion has been paid o co-blended PVDF-based copolyme s wi h inclusions o piezoelec ic nanoc ys als. Yang e al. [6] ound ha PVDF/PVDF-HFP blends loaded wi h dopamine-modi ied BaTiO3 exhibi ed supe io pola iza ion le el (d33 = 40 pc/N) compa ed o nea PVDF/PVDF-HFP blend (d33 = 23 pc/N), and ob iously, nea PVDF (d33 = 18 pc/N). In his wo k, we aim o u he inc ease he piezoelec ic pe o mance o PVDF/PVDF-T FE blends by embedding he piezoelec ic BaTiO3 nanoc ys als. The blending p ocess was pe o med on a compounding de ice ha allows he la ge- scale p oduc ion. F om he p ocessing pe spec i e, he heological beha io o he bina y blends as well as hei BaTiO3-loaded analogues was s udied. Finally, he e ec s o PVDF-T FE and BaTiO3 on he o ma ion o he elec oac i e β-phase con en , and consequen ial d33 coe icien we e in es iga ed, implying a g ea po en ial o he de eloped nanocomposi es. 2. EXPERIMENTAL PART 2.1. Ma e ials PVDF beads (CAS numbe : 24937-79-9, densi y o 1.78 g/cm3) ha ing he a e age molecula weigh (MW) o 107 000 g/mol, PVDF-T FE (Sol ene®300/P300, CAS numbe : 28960-88-5, densi y o 1.90 g/cm3) wi h he composi ion o VDF and T FE o 70 and 30 mol%, espec i ely, and BaTiO3 nanopowde (CAS numbe : 12047- 27-7, densi y o 6.08 g/cm3) we e pu chased om Sigma-Ald ich (USA). 2.2. Fab ica ion o nanocomposi es The desi ed amoun s o PVDF and PVDF-T FE we e mel -blended using a mic o-compounde DSM Xplo e MC15 (Xplo e Ins umen s, The Ne he lands) a 240°C o p oduce bina y blends wi h he weigh a ios o 100/0 and 80/20. In pa allel, analogous PVDF/PVDF-T FE blends we e ab ica ed con aining 5 w % o BaTiO3 nanopowde . In a dosing sequence, he eeds ock was g adually in oduced in o he compounde wi hin 2 minu es a 25 pm, ollowed by 10 minu e blending a 40 pm. A cons an o que indica ed homogenei y o he blends (and dispe sion o he BaTiO3). The p oduc was collec ed in a o m o ilamen . Each ilamen was cu in o pieces ha we e comp ession molded o p oduce ilms wi h a hickness o 0.5 mm. The calcula ed amoun s o g anules we e placed in o me allic molds, p e-hea ed o 5 minu es, and comp essed wi h a p essu e o 10 MPa o he addi ional 5 minu es, while empe a u e was se o 210 °C. A e wa ds, he mold was cooled down in a con olled manne o ensu e epea abili y o he p ocess. Oc obe 20 - 22, 2021, B no, Czech Republic, EU 2.3. Gene al cha ac e iza ions The dimensions and mo phology o BaTiO3 was s udied by ansmission elec on mic oscopy (TEM) on a JEM- 2100Plus (JEOL, Japan) de ice equipped wi h a LaB6 ca hode ope a ing unde he accele a ing ol age o 200 kV. P io o he analysis, he nanopowde was dispe sed in ace one and d ipped on o a ca bon-coa ed TEM g id (300 mesh, Aga Scien i ic, UK). The TEM images we e analyzed using ImageJ so wa e (Na ional Ins i u es o Heal h, USA). The su ace p ope ies o BaTiO3 we e in es iga ed h ough ni ogen adso p ion/deso p ion iso he m collec ed on a olume ic gas adso p ion analyze (BELso p Mini II, BEL, Japan) a 77K. The sample was degassed a 60 °C o 5 hou s be o e s a ing he measu emen . The speci ic su ace a ea was de e mined by B unaue - Emme -Telle (BET) me hod using da a poin s o ela i e p essu e ange om 0.05 o 0.30. The Fou ie ans o m in a ed spec oscopy (FTIR) was pe o med on Nicole 6700 (The mo-Scien i ic, USA) spec ome e equipped wi h ATR accesso y using a ge manium c ys al. The spec a we e acqui ed in a wa enumbe ange o 4000-500 cm-1 wi h a spec al inc emen o 2 cm-1 a labo a o y condi ions. The c ys allog aphic s uc u e o he samples was examined ia X-Ray di ac ions (XRD) using Mini lex 600 (Rigaku, Japan) di ac ome e wi h a Co-Kα adia ion sou ce (λ = 1.789 Å) ope a ing wi hin 2θ ange o 10- 95° wi h a scan speed o 3°/min. Rheological beha io o he mol en-s a e samples was s udied on a Physica MCR502 (An on Paa , Aus ia) heome e equipped wi h he CTD600 hea ing chambe and TC30 empe a u e con ol uni . The complex iscosi y was eco ded du ing he equency sweep om 0.1 o 100 Hz wi h a cons an ampli ude s ain o 0.05 % a he empe a u e o 230 °C. 2.4. Vib a ion sensing assembly Vib a ion sensing capabili y o he PVDF and PVDF-T FE ilms and hei BaTiO3-loaded analogues was in es iga ed on ci cula samples o 30 mm in a diame e and a hickness o 0.5 mm. P io o he measu emen , he poling o samples was pe o med a 100°C using a ield o 20 kV/mm. The samples we e p essed using a single-poin ba ; he applied mass equaled 400 g ams and equency o i s oscilla ion was se o 1 Hz. The ou pu signal was collec ed using NI-4331 esis ance subs i u ion box (Na ional Ins umen s, USA) and he inal d33 coe icien s we e calcula ed acco ding o he equa ions desc ibed elsewhe e [4,10]. 3. RESULTS AND DISCUSSION Al hough BaTiO3 nanopowde is a comme cial p oduc , i s ele an p ope ies we e s udied o unde s and i s implica ions on he s uc u al and elec omechanical cha ac e is ics o PVDF-based blends. Figu e 1a shows i s XRD pa e n wi h a numbe o sha p peaks a 25.9° (001), 36.9° (101), 45.6° (111), 53.1° (002), 60.0° (102), 66.2° (112), 78.6° (202) and 84.3° (212) p o ing pu i y and c ys alline cha ac e o he ma e ial (PDF Ca d No. 01-075-2121). The inse displays he size and mo phology; he p ima y pa icles possessed ounded-shape wi h he a e age diame e o ~48±8 nm as de e mined by image analysis. The eco ded physiso p ion iso he m cu e was classi ied as e e sible Type-II iso he m [17], and speci ic su ace a ea calcula ed using BET me hod equaled 17 m2/g. The FTIR spec a o he PVDF and PVDF/PVDF-T FE ilms a e displayed in Figu e 1b. As seen, bo h spec a we e almos iden ical and demons a ed he coexis ence o β- and α-phase [18]. In mo e de ails, he da a showed ha he addi ion o he PVDF-T FE inc emen ed β-phase con en , which was e lec ed in a highe in ensi y o β-peak a ound 841 cm-1. A he same ime, he in ensi y o α-peaks a ound 763 cm-1 and 1210 cm-1 diminished con i ming he desi able phase ans o ma ion [5]. The e o e, bina y PVDF/PVDF-T FE blend was expec ed o achie e a supe io piezoelec ic pe o mance. Such end as no e ealed in he FTIR spec a o BaTiO3-loaded samples due o o e lapping in ensi y coming om he ille . Oc obe 20 - 22, 2021, B no, Czech Republic, EU Figu e 1 The XRD pa e n (a) o BaTiO3 nanopowde wi h inse TEM igu e, and he FTIR spec a (b) o he nea PVDF and PVDF/PVDF-T FE bina y mix u e. The XRD analysis was used o de e mine he e olu ion o he c ys alline phase in he samples. As seen in Figu e 2a, he di ac og am (Kα1, λ = 1.790 Ǻ) o nea PVDF exhibi ed 2- he a peaks a 21.9°, 40.7° and 43.9° co esponding o β-phase, and a small peak a ound 42.1° ela ed o α-phase. A e he addi ion o PVDF-T FE, he in ensi y o he β-peak signal a 21.9° d ama ically inc eased, which demons a ed he abili y o T FE o spon aneously c ys alize in o his phase, ega dless he pos - ea men [5,10]. Mo eo e , he bina y blend exhibi ed a signi ican de elopmen o α-phase co esponding o a double-peak a 19.4° and 20.1°; he la e is some imes associa ed also o γ-phase [18]. In oducing he BaTiO3 nanopowde modi ied he XRD spec a (Figu e 2b) and signi ican ly a ec ed he in ensi ies o he PVDF- ela ed peaks. By compa ing he spec a, i appea s ha he c ys alline phase was de eloped o a lowe ex en , when compa ed o he nea analogues. This phenomenon mos likely occu ed due o nano-con inemen e ec s on polyme c ys alliza ion, since BaTiO3 nanopa icles ep esen s e ic obs acles es ic ing he mobili y o he PVDF chains [19]. Despi e his e ec , he PVDF/PVDF-T FE blend loaded wi h BaTiO3 exhibi ed ema kably highe β-peak in ensi y han i s coun e pa based on PVDF. The es o he XRD spec a (2- he a abo e 28°) esembled he pa e n o BaTiO3 nanopowde . Figu e 2 XRD pa e ns o PVDF and PVDF/PVDF-T FE blends (a) and hei BaTiO3-loaded analogues (b). Rheological s udy was employed o gain a use ul insigh o he p ocessing abili y o he PVDF-based sys ems and he esul s a e shown in Figu e 3. I was ound ha s o age modulus, G’, and complex iscosi y, η*, alues o PVDF/PVDF-T FE blend we e highe han hose o nea PVDF, which was a ibu ed o a highe pola i y o he o me p o iding s onge in e ac ions, and hus mo e esis ance o low [20]. The addi ion o BaTiO3 nanoc ys als u he inc eased he G’ and η* alues due o well-known s i ening e ec s o igid ino ganic pa icles when dispe sed in polyme ma ix. Oc obe 20 - 22, 2021, B no, Czech Republic, EU Figu e 3 The mel heology da a o he PVDF and PVDF/PVDF-T FE blends (solid symbols) and hei BaTiO3-loaded analogues (open symbols) ep esen ed as s o age modulus (a) and complex iscosi y (b). The elec omechanical capabili y o he PVDF-based elemen s can be p ede e mined by he β-phase con en [11] and he p esence o nano ille s [6], besides he o he ele an ac o s [10]. Table 1 displays he eco ded d33 alues o he in es iga ed samples. As seen, he PVDF/PVDF-T FE blend exhibi ed a supe io d33 coe icien when compa ed o he nea PVDF due o he abili y o PVDF-T FE o c ys allize di ec ly in o he β-phase [5], which co ela es well wi h he XRD pa e n (Figu e 2a). The addi ion o BaTiO3 nanopowde u he enhanced d33 alues (by 23.6 % and 41.7 %, espec i ely, compa ed o nea analogues), which s ems om i s inhe en piezoelec ic cha ac e . F om hese easons, he PVDF/PVDF-T FE wi h BaTiO3 inclusions exhibi ed he highes d33, and hus, he bes ib a ion sensing and ene gy ha es ing capabili y among he samples. I is p esumed ha u he imp o emen s could be achie ed by inc easing he concen a ion o BaTiO3 nanoc ys als. Table 1 The d33 alues o he PVDF and PVDF/PVDF-T FE ilms and hei BaTiO3-loaded analogues Sample ID 100/0 80/20 100/0 + BaTiO3 80/20 + BaTiO3 d33 (pC/N) 14.8±1.7 15.1±1.4 18.3±1.1 21.4±0.7 4. CONCLUSION In his wo k, he p ocessing and ene gy ha es ing capabili ies o he nea PVDF, PVDF/PVDF-T FE blend, and hei BaTiO3-loaded analogues we e in es iga ed. The ma e ials we e ab ica ed using indus ially scalable echniques, such as compounding and comp ession molding. The FTIR showed ha bina y blend exhibi ed a highe con en o he elec oac i e β-phase, wi hou any addi ional in e en ions o pos -p ocessing. The XRD analysis con i med he p esence o β-phase ia cha ac e is ic signal a 21.9°, and also, a mino con en o α- phase a 19.4° and 20.1°. The in ensi y o hese peaks was a enua ed in BaTiO3-loaded analogues, mos p obably, due o nano-con inemen e ec s on polyme c ys alliza ion. The co-blending o PVDF-T FE and he p esence o BaTiO3 nanoc ys als esul ed o inc eased G’ and η* alues, bu hese ac o s syne gis ically enhanced d33 coe icien up o 21.4±0.7 pC/N, which is highly ele an o in ended applica ions. ACKNOWLEDGEMENTS The au ho s g a e ully acknowledge he Czech Science Founda ion (g an no. 19-17457S) o he inancial suppo . This wo k was also suppo ed by he Minis y o Educa ion, You h and Spo s o he Czech Republic - DKRVO (RP/CPS/2020/003) and (RP/CPS/2020/006). Oc obe 20 - 22, 2021, B no, Czech Republic, EU REFERENCES [1] WANKHADE, S.H., TIWARI, S., GAUR, A., MAITI, P. PVDF-PZT nanohyb id based nanogene a o o ene gy ha es ing applica ions. Ene gy Repo s. 2020, ol. 6, pp. 358-364. [2] GAUR, A., KUMAR, C., TIWARI, S., MAITI, P. E icien ene gy ha es ing using p ocessed poly( inylidene luo ide) nanogene a o . ACS Applied Ene gy Ma e ials. 2018, ol. 1, pp. 3019-3024. [3] RAMADAN, K.S., SAMEOTO, D., EVOY, S. 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