RESEARCH ARTICLE
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High-Impac PLA in Compa ibilized PLA/PCL Blends:
Op imiza ion o Blend Composi ion and Type and Con en o
Compa ibilize
Ainhoa Fe nández-Tena, I zia O aegi, Lou des I us a, Vic o Sebas ián,
Gonzalo Gue ica-Eche a ia, Alejand o Jesus Mülle , and No a A anbu u*
In his wo k, he effec i eness o se en comme cial compa ibilize s is es ed
in polylac ide (PLA)/poly(𝝐-cap olac one) (PCL) blends wi h diffe en
composi ions o ob ain a high-impac PLA. None o he compa ibilize s is
effec i e o 90/10 and 80/20 PLA/PCL composi ions, as no imp o emen o
he impac s eng h is obse ed. Fo he 70/30 composi ion, compa ibilize s
ha ing glycidyl me hac yla e (GMA) and ac yla e g oups in hei s uc u e a e
p o ed he mos effec i e, as he mo phological change owa ds co-con inui y
induced by hem leads o significan impac s eng h imp o emen s (o
≈345% and 90% wi h espec o he nea PLA and he noncompa ibilized
PLA/PCL 70/30 blend, espec i ely). The 70/30 PLA/PCL composi ion, as i
shows he bes balance o p ope ies, and he bes compa ibilize
(El aloyPTW) a e chosen o ca y ou he op imiza ion o he compa ibilize
con en . I is ound ha adding 6 ph o he blend esul s in highly oughened
and duc ile blends while main aining a high modulus and yield s eng h
alues. La ge compa ibilize con en s lead o e en highe impac s eng h
alues, bu he low-s ain mechanical p ope ies a e no ably educed. Thus, in
his wo k, a simple and easily scalable me hod o p oduce high-impac PLA is
shown, as i implies he compounding o h ee comme cially a ailable
componen s wi hou in ol ing any oxic sol en s.
A. Fe nández-Tena, I. O aegi, L. I us a, G. Gue ica-Eche a ia,
A. J. Mülle , N. A anbu u
POLYMAT and Depa men o Ad anced Polyme s and Ma e ials: Physics
Chemis y and Technology
Facul y o Chemis y
Uni e si y o he Basque Coun y UPV/EHU
Paseo Manuel de La dizabal 3, Donos ia-San Sebas ián 20018, Spain
E-mail: [email p o ec ed]
The ORCID iden ifica ion numbe (s) o he au ho (s) o his a icle
can be ound unde h ps://doi.o g/10.1002/mame.202300213
© 2023 The Au ho s. Mac omolecula Ma e ials and Enginee ing
published by Wiley-VCH GmbH. This is an open access a icle unde he
e ms o he C ea i e Commons A ibu ion License, which pe mi s use,
dis ibu ion and ep oduc ion in any medium, p o ided he o iginal wo k
is p ope ly ci ed.
DOI: 10.1002/mame.202300213
1. In oduc ion
Due o he cu en issues ela ed o he lack
o ossil esou ces and he accumula ion o
plas ic was e, o e he pas decades, many
esea che s ha e ocused on he in es i-
ga ion o biobased and compos able poly-
me s since hei expansion could p e en
he accumula ion o solid was e and de-
c ease he use o non- enewable esou ces.
Poly(lac ic acid) o polylac ide (PLA) is one
o he mos ex ensi ely esea ched biobased
and biodeg adable polyme s used o his
pu pose. I is cu en ly one o he mos
comme cially de eloped biopolyme s.[1,2]
PLA is syn hesized om lac ic acid, ob-
ained h ough he e men a ion o suga
o s a ch.[3] I possesses high modulus and
s eng h, good cla i y, and ba ie p ope -
ies. Thanks o hese cha ac e is ics and
i s good he mal p ocessabili y, PLA has
been used in indus ial sec o s such as ex-
ile, packaging, cons uc ion, o au omo-
i e. Mo eo e , due o i s biodeg adabil-
i y, non- oxici y, and bio eso babili y, i has
been used in biomedical applica ions such
as d ug deli e y sys ems, su u es, and is-
sue enginee ing.[1,3,4]
V. Sebas ián
Depa men o Chemical and En i onmen al Enginee ing. Uni e si y o
Za agoza
Campus Río Eb o-Edificio I+D
C/ Poe a Ma iano Esquillo S/N, Za agoza 50018, Spain
V. Sebas ián
Ins i u o de Nanociencia y Ma e iales de A agón (INMA)
CSIC-Uni e sidad de Za agoza
Za agoza 50009, Spain
V. Sebas ián
Ne wo king Resea ch Cen e on Bioenginee ing
Bioma e ials and Nanomedicine
CIBER-BBN
Mad id 28029, Spain
A. J. Mülle
IKERBASQUE
Basque Founda ion o Science
Plaza Euskadi 5, Bilbao 48009, Spain
Mac omol. Ma e . Eng. 2023,308, 2300213 2300213 (1 o 14) © 2023 The Au ho s. Mac omolecula Ma e ials and Enginee ing published by Wiley-VCH GmbH
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Al hough PLA possesses good cha ac e is ics and can be
molded wi h s anda d polyme p ocessing equipmen s,[5] i
shows ce ain d awbacks, p ima ily ela ed o i s he mal and me-
chanical p ope ies, which limi i s p oduc ion and use in diffe -
en applica ions.[1] PLA has a low glass ansi ion empe a u e
(Tg) (55–60 °C) and c ys alliza ion a e, limi ing he usage o PLA
o applica ions wi h ela i ely low se ice empe a u es.[1,4,6,7] On
he o he hand, PLA also suffe s om inhe en b i leness and a
e y low oughness a oom empe a u e. Hence, he use o PLA
may be limi ed in applica ions whe e high elonga ion o plas ic
de o ma ion a high impac a es a e equi ed.[8,9]
A widesp ead and cos -effec i e me hod o o e come he d aw-
back o he mechanical p ope ies is o blend PLA wi h duc ile
polyme s.[7,10] Poly(𝜖-cap olac one) (PCL) is a duc ile semic ys-
alline alipha ic polyes e , wi h Tgand Tm≈−60 °C and 55–
70 °C, espec i ely.[1,11] Al hough i is a nonbiobased polyme ,
PCL is biodeg adable and biocompa ible, as well as PLA. These
cha ac e is ics make PCL a sui able candida e o be blended
wi h PLA since biodeg adabili y and biocompa ibili y will be
main ained.[1,11] Due o i s low Tg, PCL exhibi s high elonga ion a
b eak (≈600%[8]) and oughness. The e o e, adding PCL o PLA
as a seconda y phase could imp o e he duc ili y and oughness
o PLA.[1]
In gene al, elonga ion a b eak o PLA has been easily en-
hanced (85-400%) by mel blending i wi h PCL,[12–18] e en i , in
some cases, poo o no inc emen has also been epo ed.[19–23]
Howe e , owing o he immiscibili y be ween bo h polyme s, im-
p o ing he impac oughness o PLA/PCL blends is mo e chal-
lenging, hough some good a emp s ha e been made in his
field. In his sense, i has been p o ed ha he PCL concen a-
ion, he c ys allini y o he PLA ma ix, he PLA/PCL iscosi y
a io, and he p ocessing condi ions a e key ac o s ha need o be
op imized o imp o e he impac s eng h o PLA.[24–29] Ne e he-
less, achie ing he op imal composi ion, p ocessing condi ions,
and mo phology is no always possible. Tha is why, high impac
s eng h alues o supe oughness a e no usually epo ed in he
li e a u e o PLA/PCL blends.[12–14,19]
To o e come his issue, diffe en kinds o compa ibilize s
ha e been used o une he mo phology and compa ibili y o
he blends and de elop a PLA/PCL blend wi h high impac e-
sis ance. Vilay e al.[30] used a polye hylene oxide-polyp opylene
oxide-polye hylene oxide (PEO-PPO-PEO) iblock copolyme as
a compa ibilize o PLA70/PCL30 blends. They obse ed a shi
in he Tgand Tmo PLA and PCL owa ds each o he , indica ing
an inc ease in compa ibili y, as well as a significan imp o emen
in he oughness o PLA/PCL blends. The au ho s a ibu ed his
o he pola in e ac ions be ween PLA, PCL, and he copolyme .
Reac i e compa ibiliza ion has also p o ed effec i e when com-
pa ibilizing PLA/PCL blends. Ha ada e al.[31] p epa ed PLA/PCL
blends wi h ou diffe en eac i e p ocessing agen s. Blends wi h
lysine iisocyana e (LTI) showed he bes esul s, significan ly
imp o ing unno ched and no ched Cha py impac s eng h. Hou
e al.[32] used diffe en amoun s o e hylene-me hyl ac yla e-
glycidyl me hac yla e (EMA-GMA) o enhance he oughness o
PLA90/PCL10 blends. Wi h 8 ph o EMA-GMA he highes im-
pac s eng h was achie ed, 64.31 kJ m−2,≈23 imes highe han
ha o nea PLA. Howe e , he me hods p oposed in he li e a-
u e do no seem easily implemen able a an indus ial le el, ei-
he because lab-syn he ized compa ibilize s o componen s ha
a e difficul o acqui e a a la ge scale we e employed o because
he blending echnique used was no con inuous.
In he p esen wo k, he ab ica ion o a high-impac PLA was
sough using an easy and indus ially scalable p ocess. Wi h his
pu pose, compa ibilized PLA/PCL blends we e p epa ed by mel
mixing in a win sc ew ex ude , using se en diffe en comme -
cially a ailable compa ibilize s. The PLA/PCL composi ion, com-
pa ibilize ype, and con en we e op imized. To do ha , he p e-
pa ed composi ions’ mo phology and he mechanical and he -
mal p ope ies we e de e mined and compa ed. As a e e ence,
he co esponding noncompa ibilized PLA/PCL blends and nea
PLA wi h he diffe en compa ibilize s we e p epa ed and cha -
ac e ized.
2. Expe imen al Sec ion
2.1. Ma e ials
The PLA used in his wo k was a comme cially a ailable ex u-
sion g ade PLA (Ingeo Biopolyme 4032D, 1.2–1.6% D-isome
lac ide) supplied by Na u eWo ks (Minneapolis, MN, USA). PCL
(CAPA 6800) was pu chased om Inge i y (No h Cha les on,
SC, USA) wi h a molecula weigh o 80 000 g mol−1.DowChem-
icals (Midland, MI, USA) dona ed he se en polye hylene-based
copolyme s employed as compa ibilize s. The chemical s uc u e
o each copolyme is summa ized in Table 1. Al hough he exac
chemical composi ion o BiomaxSG120 is unknown, i consis s
o an e hylene-ac yla e e polyme specifically designed o PLA,
bea ing epoxy moie ies.[33]
2.2. Sample P epa a ion
Be o e mel p ocessing, all he ma e ials we e d ied o e nigh
o a oid mois u e-induced deg ada ion. The PLA was d ied in
a dehumidifie a 80 °C, and he PCL and he compa ibilize s
we ed iedinano ena 40°C. Compa ibilized PLA/PCL blends
(PLA/PCL/C) ha ing 90/10, 80/20, and 70/30 PLA/PCL compo-
si ions we e mel blended in a Collin Teach-Line ZK25 T SCD 15
win-sc ew ex ude (L/D a io 18 and sc ew diame e 25 mm)
(Ebe sbe g, Ba a ia, Ge many). In all he cases, he con en o
he compa ibilize was se a 10 w .% wi h espec o PCL, i.e.,
90/10/1, 80/20/2, and 70/30/3. A sc ew speed o 200 pm and
a p ocessing empe a u e o 190 °C we e employed, and he ex-
uda es we e cooled in a wa e ba h and pelle ized. Noncompa -
ibilized PLA/PCL blends we e also p epa ed as a e e ence. In
addi ion, o assess i he compa ibilize s ha e any effec on he
p ope ies o nea PLA, blends o PLA wi h 3 ph o each ype
o compa ibilize (100/0/3) we e also p epa ed. Based on he ob-
ained esul s, 60/40 and 60/40/4 composi ions we e also p e-
pa ed using he compa ibilize El aloyPTW. Mo eo e , o s udy
he effec o he amoun o compa ibilize , 70/30 blends wi h 1.5,
4.5, 6, 10, and 15 ph o El aloyPTW and 60/40 wi h 8 and 16 ph
o El aloyPTW we e p epa ed. Table S1, Suppo ing In o ma ion,
summa izes all he composi ions p epa ed in his wo k.
Be o e injec ion molding, he pelle s we e d ied o e nigh in
a dehumidifie a 80 °C. Tensile (ASTM D-638 ype IV) and im-
pac (ASTM D-256) specimens we e p epa ed by injec ion mold-
ing, which was ca ied ou in a Ba en eld BA-230-E (Wi mann,
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Table 1. Polye hylene-based copolyme s used as compa ibilize s and hei composi ion.
Comonome s [w .%]
Compa ibilize nBu ylac yla e (BA) Vinyl ace a e (VA) Glycidyl me hac yla e
(GMA)
E hyl ac yla e (EA) Me hyl ac yla e (MA)
El aloy4170 21 9
El aloyPTW 28 5.3
El aloy5160 20 5.3
El aloyAC12024S 24
El aloyAC2618 18
El aloyAC2615 15
BiomaxSG120 Unknown
Ko ingb unn, Aus ia) machine equipped wi h a ecip oca ing
sc ew (L/D a io 30 and sc ew diame e 18 mm) a 190 °C. The
mold empe a u e was se a 20 °C.
2.3. Cha ac e iza ion and Tes ing Me hods
2.3.1. Dynamic Mechanical The mal Analysis (DMTA)
The phase s uc u e o he samples was s udied h ough dynamic
mechanical he mal analysis (DMTA) pe o med in a TA Ins u-
men s Q800 DMA iscoelas ome e (New Cas le, DE, USA). Mea-
su emen s we e ca ied ou in single can ile e geome y be-
ween −100 °C and 130 °C a a cons an hea ing a e o 4 °C
min−1. In he case o nea PCL, he es ing empe a u e ange
was om −100 °C o25°C. Expe imen s we e conduc ed a a
cons an equency o 1 Hz wi h an ampli ude o 15 μm. Two
samples we e analyzed pe composi ion.
2.3.2. Diffe en ial Scanning Calo ime y (DSC)
The mal p ope ies o he blends we e analyzed by diffe en ial
scanning calo ime y (DSC) in a Pe kin Elme D8000 calo ime-
e (Wal ham, MA, USA) unde d y ni ogen a mosphe e wi h a
flow o 20 mL min−1. The equipmen was calib a ed wi h indium
and in s anda ds. Samples o DSC scans we e aken om in-
jec ion molded specimens and hea ed om 25 °C o 200 °Ca
20 °Cmin
−1. F om hose hea ing scans, mel ing (Tm)andcold
c ys alliza ion (Tcc) peak empe a u es we e ob ained. The deg ee
o c ys allini y (Xc) o PLA in he injec ed specimens was de e -
mined acco ding o Equa ion 1[29]:
Xc=ΔHm−ΔHcc
w ΔH0
m
(1)
whe e ΔHmand ΔHcc a e he measu ed en halpies o mel ing and
cold c ys alliza ion, espec i ely, w ep esen s he weigh ac-
ion o PLA in he blend, and ΔHm0is he mel ing en halpy o
comple ely c ys alline PLA (93.6 J g−1[1,29]). Since he mel ing en-
do he m o PCL appea s a he same posi ion as he Tgo PLA,
he Xco PCL wi hin he blends could no be de e mined. To cal-
cula e he Xco nea PCL, a alue o 139.5 J g−1was used.[34] Two
samples we e measu ed pe composi ion.
2.3.3. T ansmission Elec on Mic oscopy (TEM)
The mo phology o he blends was de e mined by ansmis-
sion elec on mic oscopy (TEM) using a TEM mic oscope TEC-
NAI G2-20 TWIN TEM equipped wi h LaB6 filamen ope a -
ing a an accele a ing ol age o 200 kV (The moFishe Scien-
ific, Wal ham, MA, USA). Fo ha pu pose, samples we e cu
in ul a- hin sec ions o 90 nm wi h a diamond kni e and a c yo-
genic condi ions on a Leica EMFC 6 ul amic o ome de ice (Leica
Geosys ems AG, Un e en elden, Swi ze land). Those sec ions
we e moun ed on 200-mesh coppe g ids.
2.3.4. Fou ie T ans o m In a ed-A enua ed To al Reflec ance
(FTIR-ATR) Spec oscopy
To de e mine whe he he compa ibilize s could eac wi h he
PLA and he PCL, Fou ie ans o m in a ed-A enua ed o al
eflec ance (FTIR-ATR) spec oscopy measu emen s we e pe -
o med on a Nicole 6700 FTIR coupled o an ATR accesso y
(Golden Ga e) (The moFishe Scien ific, Wal ham, MA, USA).
Measu emen s we e pe o med di ec ly o injec ion molded spec-
imens. Spec a we e eco ded be ween 400 and 4000 cm−1wi h
a esolu ion o 4 cm−1. The final spec a we e he a e age o e 32
scans.
2.3.5. Tensile Tes ing
Tensile es s we e pe o med using an Ins on 5569 ensile es e
(Ins on, No wood, MA, USA). A c osshead speed o 10 mm
min−1was used, and he elas ic modulus, he yield s eng h,
and he elonga ion a b eak we e de e mined om he ob ained
s ess-s ain cu es. A leas fi e ensile specimens we e es ed
o each epo ed alue.
2.3.6. No ched Izod Impac Tes ing
No ched Izod impac s eng h was de e mined using a Ceas
6548/000 pendulum (Ins on, No wood, MA, USA). No ches
we e machined acco ding o ASTM D-256 (dep h 2.54 mm and
adius 0.25 mm). Repo ed a e age alues we e ob ained om a
minimum o eigh impac specimens.
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Figu e 1. a) Modulus and yield s eng h and b) elonga ion a b eak and impac s eng h, as a unc ion o he PCL con en . Dashed lines ep esen a
simple addi i e law o mix u es.
3. Resul s and Discussion
Fo he sake o cla i y, he esul s ob ained in he p esen wo k
ha e been di ided in o ou sec ions. The fi s one summa izes
he esul s o he e e ence noncompa ibilized PLA/PCL blends.
In he second sec ion, as some o he copolyme s used in his
s udy ha e been epo ed o ac as impac modifie s o PLA,[35,36]
he effec o he compa ibilize s on nea PLA is b iefly analyzed.
In he hi d sec ion, he influence o he compa ibilize ype on
he p ope ies o he compa ibilized PLA/PCL/C blends is s ud-
ied. Finally, in he las sec ion, he effec o he amoun o one o
he bes compa ibilize s (El aloyPTW) is analyzed.
3.1. Re e ence Noncompa ibilized PLA/PCL Blends: Influence o
PCL Con en
The phase s uc u e o noncompa ibilized PLA/PCL blends was
s udied by DMTA. Figu e S1, Suppo ing In o ma ion, shows
he an 𝛿 e sus empe a u e plo s o PLA, PCL, and PLA/PCL
blends, while he Tg alues o bo h PLA and PCL a e summa-
ized in Table S2, Suppo ing In o ma ion. The Tgo nea PLA
and PCL we e 73.5 ±0.2 °Cand−37.6 ±0.7 °C, espec i ely. All
he PLA/PCL blends display wo an 𝛿peaks a app oxima ely he
same posi ion as he nea componen s, poin ing o he blends be-
ing immiscible, as i has been widely epo ed o mel -blended
PLA/PCL blends.[12,13,17,37,38]
Figu e S2, Suppo ing In o ma ion, shows he fi s DSC hea -
ing scans o PLA, PCL, and PLA/PCL blends. Da a ex ac ed
om hem a e summa ized in Table S2, Suppo ing In o ma ion.
As poin ed ou in he in oduc ion, PLA shows a e y slow c ys al-
liza ion a e. As a consequence, PLA is unable o c ys allize du -
ing injec ion molding. On he con a y, PLA chains can ea ange
and c ys allize du ing hea ing in he DSC. In nea PLA, he cold
c ys alliza ion appea s a 101.3 °C. In he PLA/PCL blends, he
cold c ys alliza ion empe a u e (Tcc) shi s owa ds lowe empe -
a u es as he PCL con en inc eases. This shi is a consequence
o he nuclea ing effec exe ed by he PCL[12,19,31,38] inducing he
lowe cold c ys alliza ion o PLA.[24,25,39] As shown in Figu e S2
and Table S2, Suppo ing In o ma ion, he Tmo PLA shows a
dec easing end wi h he PCL con en , hough he a ia ions a e
sligh . On he con a y, he addi ion o PCL sligh ly enhances he
c ys allini y deg ee o PLA due o he al eady discussed nuclea -
ing effec .[19] Ne e heless, he diffe ences be ween he Xco nea
PLA and PLA wi hin PLA/PCL blends a e small.
Figu e 1 shows he mechanical pa ame e s ob ained by ensile
and impac es s o he e e ence noncompa ibilized PLA/PCL
blends as a unc ion o he PCL con en . Dashed lines ep esen a
simple addi i e law o mix u es. The da a o he impac s eng h
alue o nea PCL is no shown in Figu e 1b since he speci-
mens did no b eak du ing he impac es . PLA and PCL show
Young’s modulus o 3730 MPa and 424 MPa, espec i ely. In non-
compa ibilized PLA/PCL blends, i is obse ed ha he modulus
dec eases linea ly as he amoun o PCL inc eases (Figu e 1a),
which is ypical o PLA/PCL sys ems.[12,18,20,37] Simila ly, he
yield s eng h also dec eases wi h inc easing he PCL con en ,
showing a nega i e de ia ion om he addi i e law o mix u es.
As poin ed ou in he in oduc ion, b i leness is one o he
main d awbacks o PLA. Indeed, he elonga ion a b eak o he
nea PLA employed in his wo k is 3%. By con as , he PCL
does no b eak un il i has eached a de o ma ion o 442%. In
Figu e 1b, i can be seen ha adding 10 w .% o PCL o PLA
leads o a significan imp o emen in he elonga ion a b eak,
eaching a alue o 172%. The duc ili y con inues inc easing
sligh ly wi h u he addi ion o PCL, displaying a posi i e de ia-
ion om he law o mix u es. Simila ends we e seen in o he
wo ks, hough he b i le-duc ile ansi ion happens a highe
PCL con en s.[15,16,37]
Rega ding he impac s eng h, PLA displays a alue o 22 J
m−1, ano he demons a ion o i s inhe en agili y, whe eas PCL
does no b eak unde he es ing condi ions employed in his
wo k. The impac s eng h o he noncompa ibilized PLA/PCL
blends does no significan ly change un il 30 w .% o PCL is
added o PLA, a composi ion ha shows a alue almos double
o ha o nea PLA. Thus, e en i by adding 10 w .% o PCL, he
duc ili y o PLA is imp o ed significan ly, mo e han ha con-
en is needed o inc ease he impac s eng h, and conside ably
highe PCL con en s a e equi ed in o de o enhance he ough-
ness o PLA. Ne e heless, despi e he impac s eng h o PLA
being imp o ed in he 70/30 composi ion, he a ained alue is
s ill low o applica ions whe e high impac s eng h is equi ed.
The mo phology o he noncompa ibilized blends was ana-
lyzed by TEM (Figu e 2) o de e mine he eason behind he
change in oughness obse ed when he PCL con en changes
om 20 w .% (33 J m−1) o30w .%(53Jm
−1). In he
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Figu e 2. TEM mic og aphs o a) 80/20 and b) 70/30 blends.
mic og aphs, he ligh g ey a eas (low con as ) co espond o he
PLA phase, whe eas he da k g ey (high con as ) one ep esen s
he PCL. As can be seen, bo h blends show a biphasic mo phol-
ogy ega dless o he amoun o PCL, co obo a ing he immisci-
bili y be ween PLA and PCL. A sea-island mo phology is obse ed
o he 80/20 blend (Figu e 2a), whe e PCL d ople s a e sligh ly
elonga ed due o he o ien a ion induced du ing injec ion mold-
ing. Wi h 30 w .% o PCL (Figu e 2b), bigge and mo e elonga ed
PCL pa icles a e obse ed. Bo lhoko e al.[37] also no ed ha as
he pe cen age o PCL in PLA ma ix was inc eased, PCL pa i-
cles became bigge and mo e i egula , leading o a la ge pa icle
size dis ibu ion.
Conside ing he a o emen ioned impac s eng h alues,
he o ma ion o a mo phology be ween sea-island and co-
con inuous, which ea u es PCL pa icles wi h diffe en sizes and
i egula shapes, is deemed necessa y o he PCL o cause he
imp o emen o he impac s eng h o he PLA.
3.2. Re e ence PLA/0/C Blends: Influence o Compa ibilize Type
on Nea PLA
Table S3, Suppo ing In o ma ion, summa izes he he mal pa-
ame e s om DMTA and DSC o nea PLA and he 100/0/3
PLA/PCL/C composi ions wi h he diffe en compa ibilize s. The
addi ion o he compa ibilize s does no influence he Tg,Tm,o
Xco PLA. By con as , he Tcc o PLA is educed om 101.3 °C
o 94.4–92.0 °C, wi h he excep ion o he compa ibilize s El al-
oyAC2018 and El aloyAC2015, o which he educ ion is smalle .
Thus, simila o PCL addi ion, low amoun s o compa ibilize s in
PLA cause a nuclea ion effec on i s c ys alliza ion p ocess.
Figu e 3 shows he mechanical pa ame e s ob ained by ensile
and impac es s o nea PLA and 100/0/3 composi ions. The
da a o PLA a e ep esen ed wi h s aigh dashed lines. As ex-
pec ed, i hei so na u e is conside ed, he addi ion o com-
pa ibilize s o nea PLA p oduces small dec eases in i s modu-
lus and yield s eng h (Figu es 3a,b, espec i ely), ega dless o
he ype used. On he con a y, he effec o he compa ibiliz-
e s on he elonga ion a b eak o PLA diffe ed significan ly om
one ano he as a unc ion o hei chemical s uc u e. As can be
obse ed in Figu e 3c, when compa ibilize s ha con ain epoxy
moie ies wi hin hei chemical s uc u e a e used (BiomaxSG120,
El aloyPTW, El aloy4170, and El aloy5160), he elonga ion a
b eak inc eases up o alues highe han 135%. Wi h compa ibi-
lize s ha con ain e hyl ac yla e comonome s (El aloy2618 and
El aloy2615) he esul an elonga ion a b eak alues a e lowe
han he ones men ioned be o e bu s ill highe han ha o nea
PLA. By con as , he blend wi h El aloyAC12024S, which con-
ains me hyl ac yla e as a comonome , shows no imp o emen
in he duc ili y o he PLA. F om hese esul s, i is clea ha he
in e ac ions/ eac ions ha migh occu be ween he copolyme s
and he PLA a e diffe en depending on he chemical s uc u e
o he comonome s cons i u ing he copolyme s. This effec will
be discussed la e on. On he o he hand, i mus be no ed ha
al hough adding a sui able compa ibilize o PLA is enough o
inc ease i s elonga ion a b eak conside ably, i does no al e he
impac s eng h o PLA, as shown in Figu e 3d.
3.3. Compa ibilized PLA/PCL Blends (PLA/PCL/C): Influence o
he Compa ibilize Type
Figu e 4a,b show, espec i ely, he Tg alues o PCL and PLA o
all he s udied PLA/PCL/C composi ions. The addi ion o com-
pa ibilize s has no influence on he Tgo PLA, ega dless o he
copolyme na u e. As shown in Figu e 4a, he Tgo PCL displays
mo e a ia ions, al hough no significan end can be app eci-
a ed. As also men ioned in he SI, bo h he low in ensi y and he
wid h o he ansi ion make i difficul o de e mine he Tgo
he PCL accu a ely. Simila ly, he Tcc,Tm,andXco PLA show no
significan changes wi h he inco po a ion o he compa ibiliz-
e s, as can be seen in Figu e 5. In he case o Xc, he e a e mo e
de ia ions om he alue o nea PLA, bu conside ing he e o
in he measu emen s, he diffe ences encoun e ed a e no e y
significan , and he a ia ions do no ollow any specific ends.
Figu e 6 shows he mechanical pa ame e s ob ained by en-
sile and impac es s o each PLA/PCL/C composi ion. As can
be obse ed, he modulus and yield s eng h do no significan ly
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Figu e 3. a) Modulus, b) yield s eng h, c) elonga ion a b eak, and d) impac s eng h o nea PLA and PLA/0/C blends. Dashed lines ep esen he
alues o nea PLA.
a y wi h he used compa ibilize , ega dless o he PLA/PCL
composi ion. I is no ewo hy ha , e en in he compa ibilized
blends wi h 30 w .% o PCL, he modulus emains ela i ely high
(≥2480 MPa) in all he cases. These esul s sugges ha he s ud-
ied blends could be used in applica ions whe e high s iffness is
equi ed. The d op in he yield s eng h is conside able compa ed
wi h nea PLA, bu he alues do no diffe oo much om he
ones o PLA/PCL blends.
As can be obse ed in Figu e 6c, he addi ion o he compa i-
bilize s ba ely affec ed he ini ially high elonga ion a b eak al-
ues o he blends, and he compa ibilized blends showed duc ili y
alues highe han 160%, ega dless o he PLA/PCL composi-
ion and he ype o compa ibilize used. This is ue excep o
90/10 and 80/20 blends compa ibilized wi h El aloyAC12024S
ha showed elonga ion a b eak alues significan ly lowe han
hose o he e e ence noncompa ibilized PLA/PCL blends. This
was coinciden ally he only compa ibilize ha did no imp o e
he duc ili y o nea PLA (Figu e 3c). Mey a e al.[40] blended a
PLA wi h an e hylene-me hyl ac yla e (EMA) copolyme wi h he
same MA pe cen age (24 w .%). Al hough hey used an EMA
copolyme amoun as high as 20 w .%, no significan imp o e-
men in he elonga ion a b eak o PLA was obse ed ( om 1.95%
o nea PLA o 3.76%), sugges ing poo compa ibili y be ween
PLA and EMA copolyme . Simila ly, o he wo ks also epo ed
Figu e 4. Tg alues o a) PCL and b) PLA, ob ained by DMTA, o each PLA/PCL/C composi ion. Dashed lines ep esen he alues o e e ence noncom-
pa ibilized PLA/PCL blends.
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Figu e 5. a) Tcc,b)Tm,andc)Xco PLA o each PLA/PCL/C composi ion. Dashed lines ep esen he alues o he e e ence noncompa ibilized PLA/PCL
blends.
Figu e 6. a) Modulus, b) yield s eng h, c) elonga ion a b eak, and d) impac s eng h o each PLA/PCL/C composi ion. Dashed lines ep esen he
alues o he e e ence noncompa ibilized PLA/PCL blends.
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Figu e 7. TEM mic og aphs o a) 70/30/El aloy5160 3, b) 70/30/El aloyAC12024S 3, and c) 70/30/El aloyPTW 3.
small o no imp o emen s in duc ili y when blending PLA o
o he polyme ic ma e ials wi h EMA copolyme s.[41–43] This in-
dica es ha he p esence o me hyl ac yla e g oups in he com-
pa ibilize leads o a p ema u e ailu e o he blends, a leas a
low PCL con en s. A high PCL con en s, he effec o PCL p e-
ails o e ha o El aloyAC12024S.
Figu e 6d shows he impac s eng h o all he s udied
PLA/PCL/C blends. As can be seen, o blends con aining 10 and
20 w .% o PCL, he impac s eng h alues o he compa ibilized
blends do no diffe om one compa ibilize o ano he . Mo e-
o e , he ob ained alues a e almos equal o hose o noncom-
pa ibilized PLA/PCL blends in he case o 90/10/1 composi ions
and sligh ly highe o 80/20/2 composi ions. In con as , o he
70/30/3 blends, he effec o each compa ibilize is significan ly
diffe en . While wi h El aloy5160, an impac s eng h alue o 60
Jm
−1is achie ed, a alue sligh ly highe han ha o he non-
compa ibilized 70/30 blend (53 J m−1), wi h BiomaxSG120, El-
aloyPTW, and El aloy4170, impac s eng h alues be ween 97
and 100 J m−1a e ob ained, which a e 345% and 90% highe han
ha o he nea PLA and he noncompa ibilized 70/30 blend, e-
spec i ely. Fu he mo e, in e media e alues be ween 66 and 81
Jm
−1a e ob ained wi h El aloyAC12024S, El aloyAC2618, and
El aloyAC2615.
To shed ligh on he easons o he diffe ences obse ed in
he impac s eng h, he mo phology o he blends was ana-
lyzed by TEM. Figu e 7 shows he TEM mic og aphs o 70/30/3
composi ions wi h he compa ibilize s ha showed he lowes ,
in e media e, and highes impac s eng h alues, espec i ely:
El aloy5160, El aloyAC12024S, and El aloyPTW. As can be ob-
se ed in he mic og aphs, e en i he PLA/PCL composi ion is
he same in he h ee blends, he final mo phology a ies wi h
he used compa ibilize . Wi h El aloy5160 (Figu e 7a), de o med
PCL d ople s dispe sed all o e he PLA ma ix a e seen. On he
o he hand, El aloyAC12024 (Figu e 7b) induces he elonga ion
o PCL d ople s compa ed o he mo phology o he noncompa -
ibilized 70/30 blend (Figu e 2b). Finally, he p esence o El al-
oyPTW causes he change o he mo phology o he noncompa -
ibilized 70/30 blend in o a cocon inuous s uc u e. I is wo h
men ioning ha inside PCL d ople s, da ke zones a e obse ed
in all he mic og aphs (ma ked wi h g een a ows). These zones
co espond o he compa ibilize phase, which possesses highe
elec onic densi y. The p esence o hese black pa icles in he
PCL phase implies ha he compa ibilize s, ega dless o hei
chemical s uc u e, ha e a highe affini y owa ds he PCL phase.
I he impac s eng h alues o he analyzed blends a e
aken in o accoun , and conside ing ha o all he blends, he
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Figu e 8. TEM mic og aph o 80/20/El aloyPTW 2.
c ys allini y, and he he mal ansi ions a e qui e simila , i can
be concluded ha he diffe en mo phologies induced by he
p esence o he diffe en compa ibilize s a e he esponsible o
he a ia ions obse ed. Since he es o he pa ame e s ha may
affec he mo phology a e kep cons an , he chemical s uc u e
o he diffe en compa ibilize s mus be esponsible o p omo -
ing he o ma ion o one o ano he ype o mo phological s uc-
u e and, consequen ly, be e o wo se impac s eng h alues.
The esul s in Figu e 6d indica e ha achie ing a cocon inuous
mo phology is he key o ob aining highly oughened blends, and
he bes comonome combina ion o do so is he one composed
o GMA and ac yla e g oups (BiomaxSG120, El aloy4170, and El-
aloyPTW).
Hou e al.[32] analyzed he effec o diffe en concen a ions o
he EMA-GMA e polyme on he mo phology and p ope ies o
PLA/PCL blends ha ing a composi ion o 90/10. They obse ed
ha some o he compa ibilize s adhe ed o he PCL dispe sed
pa icles se ing as a b idge be ween he PCL pa icles and PLA
ma ix h ough he chemical eac ions be ween he epoxy g oups
o he EMA-GMA and he ca boxyl and hyd oxyl end g oups o
PLA and PCL, which led o an imp o emen o he in e acial
adhesion. This possibili y is analyzed in he ollowing sec ion.
Mo eo e , he au ho s obse ed ha , a high EMA-GMA con-
en s, he compa ibilize pa icles also connec ed he PCL pa -
icles be ween hem, esul ing in a shish-like s uc u e. A sim-
ila beha io –coalescence and elonga ion o he PCL phase– is
obse ed in he p esen wo k, bu only when some compa ibiliz-
e s we e used. Mo eo e , he ex en o he mo phological change
seems o be dependen on he comonome s p esen in he com-
pa ibilize , as discussed in he p e ious pa ag aphs.
On he o he side, as obse ed in Figu e 6d, he compa ibiliz-
e s effec i ely enhance he impac s eng h o he noncompa ibi-
lized blends only when 30 w .% o PCL is added o he blends.
To asce ain why hei p esence is ineffec i e in he o he s ud-
ied composi ions, Figu e 8 shows he TEM mic og aph o he
80/20 blend compa ibilized wi h El aloyPTW. I he mo pholo-
gies o he noncompa ibilized 80/20 (Figu e 2a) and he 80/20/El-
aloyPTW 2 (Figu e 8) blends a e compa ed, i can be obse ed
ha he dispe sed phase is u he elonga ed in he p esence o
he compa ibilize , showing almos a fib il-like shape. Howe e ,
a cocon inuous mo phology is no eached. In conclusion, when
PLA/PCL blends a e compa ibilized wi h El aloyPTW, he mo -
phology o he blends changes owa ds a co-con inuous mo phol-
ogy. None heless, PCL con en s highe han 20 w .% a e needed
o achie e a comple ely co-con inuous s uc u e, which is neces-
sa y o imp o e he impac s eng h in he blends unde s udy.
Based on he abo e esul s, 60/40 and 60/40/El aloyPTW 4
blends we e p epa ed o confi m i he cocon inui y is espon-
sible o he imp o ed oughness. The noncompa ibilized 60/40
blend shows an impac s eng h o 148 J m−1, which is 6.6 imes
highe han ha o nea PLA. Despi e his, when he same blend
is compa ibilized wi h El aloyPTW, an impac s eng h o 383
Jm
−1is achie ed. I has o be highligh ed ha he specimens
o his las composi ion do no en i ely b eak du ing he impac
es s, which means ha he eal impac s eng h o 60/40/El al-
oyPTW 4 is e en highe han he epo ed alue.
Figu e 9 shows he TEM mic og aphs o c yogenically ac-
u ed su aces o 60/40 and 60/40/El aloyPTW 4 blends. In he
PLA60/PCL40 blend, a mo phology nea o cocon inui y is seen,
indica ing ha he phase in e sion could be close o ha com-
posi ion. Fo PLA/PCL blends, cocon inui y has been obse ed
a PCL con en s be ween 40 and 55 w .%.[18,28,37,44] As can be ob-
se ed in Figu e 9b, he su ace o 60/40/El aloyPTW 4 shows a
cocon inuous s uc u e, he eby confi ming ha El aloyPTW in-
duces a change in he mo phology o PLA/PCL blends owa ds
cocon inui y, which in u n causes a significan imp o emen in
impac s eng h.
3.4. PLA/PCL/El aloyPTW Blends: Effec o Compa ibilize
Con en
To see he effec o he amoun o compa ibilize on he p ope ies
o he PLA/PCL/C blends, a compa ibilize was selec ed among
hose ha ga e he bes esul s in he p e ious sec ion. Thus, El-
aloyPTW was chosen and added in diffe en con en s o 70/30
blends since hese composi ions showed he bes balance o me-
chanical p ope ies.
Figu e 10 shows he Tg alues o PLA and PCL o all he
70/30/El aloyPTW blends. While he Tgo PLA does no a y sig-
nifican ly, he Tgo PCL shows an inc easing end wi h inc eas-
ing he El aloyPTW con en . These esul s a e in ag eemen wi h
he ones epo ed by Hou e al.[32] who obse ed a shi in he Tg
o PCL as hey inc eased he con en o EMA-GMA in PLA/PCL
blends, due o he in e acial in e ac ions be ween he end g oups
o PLA and PCL wi h he epoxy g oups o he compa ibilize .
The imp o ed in e acial adhesion p o oked by he compa ibi-
lize and i s endency o loca e inside he PCL phase (as will be
shown and discussed la e ), hinde ing he mobili y o he PCL
phase, could be he easons behind he beha io obse ed o he
Tgo he PCL.
As p e iously men ioned, he epoxy g oups wi hin he com-
pa ibilize s ha e been epo ed o be able o eac wi h he ca -
boxyl and hyd oxyl end g oups o PLA and PCL du ing mel
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