1
Composi ion Dependen Miscibili y in he C ys alline S a e o Polyamide
6 /Polyamide 4,10 Blends: om Single o Double C ys alline Blends
Ma yam Sa a i 1, I zia O aegi 1, No a A ambu u 1, Yu Wang 2,3, Guoming Liu 2,4*, Xia
Dong 2,4, Dujin Wang 2,4, Gonzalo Gue ica-Eche a ia 1, Alejand o J. Mülle 1,5*
1 POLYMAT and Depa men o Polyme s and Ad anced 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, 20018 Donos ia-San Sebas ián, Spain
2 CAS Key Labo a o y o Enginee ing Plas ics, CAS Resea ch/Educa ion Cen e o
Excellence in Molecula Sciences, Beijing Na ional Labo a o y o Molecula Sciences,
Ins i u e o Chemis y, Chinese Academy o Sciences, Beijing 100190, China
3 Shenzhen Key Labo a o y o Polyme Science and Technology, College o Ma e ials
Science and Enginee ing, Shenzhen Uni e si y, Shenzhen 518060, China
4 Uni e si y o Chinese Academy o Sciences, Beijing 100049, China
5 IKERBASQUE, Basque Founda ion o Science, Bilbao, 48009, Spain
*Co esponding au ho s: [email protected], [email p o ec ed].
This is he accep ed manusc ip o he ollowing a icle: Ma yam Sa a i, I zia O aegi, No a A ambu u, Yu Wang, Guoming Liu,
Xia Dong, Dujin Wang, Gonzalo Gue ica-Eche a ia, Alejand o J. Mülle , Composi ion dependen miscibili y in he c ys alline s a e o
polyamide 6 /polyamide 4,10 blends: F om single o double c ys alline blends, Polyme 219 : (2021) // A icle ID 123570, which has
been published in inal o m a h ps://doi.o g/10.1016/j.polyme .2021.123570. © 2021 Else ie unde CC BY-NC-ND license (h p://
c ea i ecommons.o g/licenses/by- nc-nd/4.0/)
2
Fo Table o Con en s use only
3
Abs ac
We s udy he composi ion-dependen miscibili y o polyamide 6 and biobased
polyamide 4,10 (PA6/PA410) blends, as igge ed by c ys alliza ion d i en phase
seg ega ion. The blends we e p epa ed by ex usion in a wide composi ion ange and
s udied by X- ay di ac ion (bo h in-si u and ex-si u SAXS/WAXS), Di e en ial Scanning
Calo ime y (DSC), and Pola ized Ligh Op ical Mic oscopy (PLOM) du ing non-
iso he mal c ys alliza ion. The blends we e miscible in he amo phous s a e, as
demons a ed by a single Tg ha ollows he Fox equa ion as a unc ion o composi ion. The
blends we e also conside ed o be miscible in he mel , as no e idence o phase seg ega ion
was ound by SAXS o phase con as mic oscopy in he mel . Rema kably, he blends can
also be miscible in he c ys alline s a e in a limi ed composi ion ange. When only 10 o 20%
PA6 is p esen in he blends, co-c ys alliza ion was e idenced by DSC and WAXS and he
blends exhibi ed a single PA410 ich c ys alline phase. On he o he hand, as 30% o mo e
PA6 is added o PA410, c ys alliza ion d i en phase seg ega ion occu s and p og essi ely
inc eased wi h PA6 con en in he blends. Hence double c ys alline blends a e o med wi h
bo h PA6 ich and PA410 ich c ys alline phases. Clea e idence o he p esence o ei he
one o wo c ys alline phases was ob ained by empe a u e-dependen measu emen s
employing DSC, PLOM, WAXS and SAXS. Bo h he single and double c ys alline
PA6/PA410 blends exhibi ed good mechanical p ope ies in iew o he excellen
compa ibili y displayed by he blends. The mechanical p ope ies a e in line wi h hose
exhibi ed by miscible blends ollowing a simple ule o mix u es.
Key wo ds: biopolyme s; polyamide blends; mechanical p ope ies; nylon 6; nylon 4,10.
4
INTRODUCTION
Conce n abou he use o pe ochemical polyme s in he plas ics indus y has g own
mo e in ense o e he las decade, and e o s made owa ds hei eplacemen wi h
polyme s ex ac ed om enewable esou ces a e gaining s eng h. Biobased polyme s
p oduc ion is p edic ed o inc ease om a ound 5 million ons in 2013 o abou 17 million
ons in 2020 1. This is a esul o a combina ion o ac o s including a g owing conce n o
sus ainable de elopmen oge he wi h a highe demand o sus ainable p oduc s and he
imp o ed p ice-pe o mance cha ac e is ics o newly de eloped bioplas ics esul ing om
ecen echnological imp o emen s.
Polyamides (PAs) o nylons ha e adi ionally been used as ib es o he
manu ac u e o ab ics, bu nowadays hey a e used in many applica ions, om ca pe s 2 o
injec ion moulded and ex uded enginee ing pa s 3. Fo example, polyamide 4,10 (PA410)
is used in he au omo i e indus y o he ab ica ion o engine and c anksha co e s.
Polyamides a e ex ensi ely used enginee ing he moplas ics, which ep esen a success in
he polyme composi es indus y due o hei excellen he mo-mechanical p ope ies, and
nowadays many di e en polyamide g ades a e comme cially a ailable, including a ious
ille - ein o ced ma e ials. The eplacemen o adi ional pe ochemical polyamides wi h
o he s ob ained om enewable esou ces would esul in he de elopmen o a ange o
en i onmen ally mo e sus ainable ma e ials, which seems o be he end in he nea u u e
4-7. In his sense, PA blends o adi ional and equen ly used PAs, such as PA6 o PA66,
wi h newly comme cially a ailable bio-PAs, ei he o ally o pa ially de i ed om
enewable esou ces, a ise as a hal way solu ion and, he e o e, he s udy o hese blends is
impe a i e.
5
Mel blending is he p e e ed me hod in he indus y o he ab ica ion o polyme ic
p oduc s, because i is sol en - ee, cos -e ec i e, as , and does no need speci ic ypes o
equipmen 8. Li e a u e conce ning polyamide blends ocuses la gely on PA6 blended wi h
PP 9-11, ABS 12-14, PE 15-17, PA66 18, PET 19 , long chain polyamides (LCPAs) 20 and
di e en ubbe s 21-22, he majo i y o which a e immiscible sys ems. Polyamide-polyamide
blend li e a u e consis s p ima ily o s udies on alipha ic/a oma ic polyamide blends 23-29,
whe eas li le wo k has been pe o med on alipha ic/alipha ic blends 2, 6-7, 30-32. In addi ion,
ew wo ks ha e been epo ed on biobased polyme blends o du able high pe o mance
applica ions 33-37, while s udies conce ning biodeg adable polyme blends o ei he
biomedical o packaging applica ions a e nume ous 33, 38-46.
Miscibili y is an impo an ac o ha mus be conside ed in polyme ic blends. A
single glass ansi ion empe a u e (Tg) and a mel ing poin (Tm) educ ion a e he mos
impo an e idences o miscibili y. Mac omolecules a e cha ac e ized by long chains ha
limi mixing en opy o a he small alues, he e o e miscible polyme blends a e
in equen . The en halpy o mixing can be la ge enough in some cases o induce posi i e
ee ene gy o mixing, indica ing ha polyme mixing is no a he modynamically
spon aneous p ocess. Consequen ly, he majo i y o polyme s exhibi phase-sepa a ion
when mixed. Mos o he sel -associa ed polyamide blends a e immiscible 6,7. Howe e ,
ansamida ion eac ion can occu a high empe a u es 20, and imp o e miscibili y, due o
he o ma ion o a copolyme a he in e phase. Fo e y small o nega i e en halpies o
mixing, he polyme mix u e is miscible. I is well known ha he ypically coa se
mo phology o immiscible blends usually esul s in undesi able physical p ope ies. Indeed,
esea ch on polyme blending has been de o ed, o a la ge ex en , o s udy he esul s o he
6
addi ion o di e en compa ibiliza ion agen s and he use o no el blending p ocedu es on
hei mo phology and p ope ies 9, 12-14, 33, 35, 47-54. Ob iously, i compa ibiliza ion is no
equi ed, blending becomes quicke and cheape . Thus, miscible polyme blends a e highly
in e es ing om an indus ial poin o iew. Miscible alipha ic polyamide blends a e sca ce
and include (PA48/PA66) 30, (PA66/PA6) 32, 55, (PA410/PA610) 3 and (PA11/PA610) 2.
Fo hese miscible blends, he quan i y o me hylene uni s linking he amide g oups along
he chain is e y simila .
In a p e ious s udy 56, PA410 was mel mixed wi h up o 25% o PA6, and some
e idences o miscibili y be ween bo h polyamides we e obse ed in his limi ed
composi ion ange. The blends displayed a single glass ansi ion empe a u e, which could
be i ed o he Fox equa ion, hus indica ing ull miscibili y in he amo phous phase o e
he composi ion ange unde s udy. On he o he hand, DSC esul s poin ed o possible
mixed c ys alline phases and co-c ys alliza ion o bo h polyamides in he blends, a leas in
he men ioned limi ed ange. Howe e , he s udied composi ion ange was e y limi ed and
no X- ay sca e ing measu emen s we e pe o med o suppo possible co-c ys alliza ion.
So a , e y ew semic ys alline polyme s a e known o be miscible wi h one ano he
( o ming double c ys alline polyme blends), and he esul ing blends exhibi ema kable
kine ic and s uc u al p ope ies 57.
The objec i e o his wo k is o s udy he miscibili y, s uc u e and physical
p ope ies o no el alipha ic semic ys alline polyamide blends, namely PA410, which is
de i ed om enewable cas o oil, and PA6, whose o igin is pe ochemical, o e he whole
ange o composi ions. Se e al cha ac e iza ion echniques we e applied including
Pola ized Ligh Op ical Mic oscopy (PLOM), Di e en ial Scanning Calo ime y (DSC),
7
and bo h Wide and Small Angle X- ay Sca e ing (WAXS/SAXS). We ha e ob ained
ema kable ma ching DSC and X- ay e idence ha demons a e ha o he blends a e
miscible in he mel and amo phous s a e and can e en co-c ys allize in a limi ed
composi ion ange (i.e., hey a e also miscible in he c ys alline s a e).
EXPERIMENTAL SECTION
Ma e ials
Two ypes o polyamides (PAs), namely PA410 , supplied by DSM (EcoPaXX®
Q150-D, Genk, Belgium) and PA6, p o ided by Lanxess (Du e han® B30S, Cologne,
Ge many), we e used. PA410 was mel blended wi h PA6 a PA6/PA410 w % a io o
0/100, 10/90, 20/80, 30/70, 40/60, 50/50, 60/40, 70/30, 80/20, 90/10 and 100/0. To a oid
mois u e-induced deg ada ion eac ions, bo h PA410 and PA6 we e comple ely d ied using
a Wi mann D ymax ai d ye ( Ko ingb unn, Aus ia) a ound 60 h a a empe a u e o 80
°C. The PA6/PA410 blends we e p epa ed by mel -mixing me hod using a co- o a ing win
sc ew ex ude -kneade (Collin ZK 25T SCD 15 Teach-Line, Ebe sbe g, Ba a ia,
Ge many) wi h sc ew o a ion speed o 200 pm and a 260 °C. The diame e and L/D a io
o he ex ude sc ews we e 25 and 18 mm.
A wa e ba h was used o cool down he ex uda es, hen he samples we e
pelle ized and ully d ied again. Injec ion moulding p ocess was pe o med by using a
ecip oca ing sc ew injec ion moulding machine (Ba en eld PLUS 350/75, Ko ingb unn,
Aus ia). A 25 mm diame e sc ew and a 14 L/D a io we e employed. The injec ion
molding p ess closing o ce was 350 kN. Samples o ensile (sample hickness = 2 mm,
8
ASTM D-638, ype IV) and impac (sample hickness = 3.2 mm, ASTM D-256) es ing
we e ob ained. The mel and mould empe a u es we e se a 260 °C and 85 °C,
espec i ely. The p essu e ime, injec ion a e, and cooling ime we e se o 3 s, 42 cm3/s
and 15 s, co espondingly. To a oid he humidi y abso p ion a e he blend p epa a ion, all
samples we e s o ed in a desicca o .
Me hods
Di e en ial Scanning Calo ime y (DSC). A Pe kin-Elme DSC 8500 calo ime e
was employed. Tes s we e made unde an ul a pu e ni ogen a mosphe e wi h a low a e
o 20 ml/min and using in and indium as calib a ion s anda ds. All samples we e acuum
d ied a 80 ºC o e nigh . App oxima ely 5 mg we e placed inside DSC aluminium pans and
well sealed. DSC hea ing scans we e pe o med i s om oom empe a u e o 280 °C ( ha
is 30 °C abo e hei mel ing poin s) and held a his empe a u e o 3 min in o de o e ase
any p ese ed he mal his o y. Then, hey we e cooled down o 100 °C and hea ed up again
o 280 ºC. All measu emen s we e done a 20 °C/min and he mel ing empe a u e Tm was
de e mined as he empe a u e o he main peak in he second DSC scan.
Small Angle X-Ray Sca e ing and Wide Angle X-Ray Sca e ing (SAXS/WAXS)
Measu emen s a Ambien Tempe a u e. SAXS and WAXS samples wi h a 0.5 mm
hickness we e p epa ed by comp ession moulding a 290 °C and hen cooled down o oom
empe a u e a a 20 °C/min a e. SAXS and WAXS we e pe o med unde acuum a oom
empe a u e on ec angula ba s using a Xeuss 2.0 SAXS/WAXS sys em (Xenocs SA,
F ance). Cu K-α adia ion (GeniX3D Cu ULD, λ = 1.54 Å, 50 kV, 0.6 mA) was gene a ed.
A semiconduc o de ec o (Pila us 300K, 487×619 pixel esolu ion, DECTRIS,
9
Swi ze land) was used o collec he sca e ing signals. Each sample was exposed unde X-
ay o 20 min. All da a we e co ec ed by backg ound and emp y beam sca e ing.
Simul aneous SAXS/WAXS Synch o on Measu emen s. The s uc u al e olu ion
du ing hea ing and cooling was ollowed in-si u by WAXS and SAXS using synch o on
adia ion a he ALBA Synch o on adia ion acili y (beamline BL11-NCD) in Ce danyola
del Vallés, Ba celona, Spain. The samples we e placed in a Linkam ho s age (THMS-600
model) ha was linked wi h a liquid ni ogen cooling equipmen . All samples we e cooled
down om he mel (280 ºC) o 100 ºC a a 20 ºC/min cooling a e and hen hea ed up o
280 ºC a 20 ºC/min hea ing a e. WAXS/SAXS measu emen s we e aken egula ly e e y
30 seconds du ing bo h cooling and hea ing uns. The X- ay sou ce employed had an
ene gy o 12.4 keV wi h λ = 1.0 Å. A Rayonix LX255-HS de ec o was employed o he
WAXS con igu a ion, wi h a 230.4×76.8 mm2 ac i e image a ea, a 44 μm2 pixel size, and a
15.5 mm dis ance ( il angle = 27.3°). The sample de ec o (Pila us 1M) o he SAXS
mesu men s had an 168.7×179.4 mm2 ac i a e image a ea, a 981×1043 o al numbe o
pixels, a 172×172 µm2 pixels size, a 25 ames/sec a e, and a 6463 mm dis ance. The
calib a ion o he sca e ing ec o was accompulished by means o sil e behena e ( o
SAXS expe imen ) and ch omium (III) oxide ( o WAXS expe imen ).
Dynamic Mechanical The mal Analysis (DMTA). The phase beha iou o he
blend samples was in es iga ed by DMTA using a TA Q-800 iscoelas ome e . Scans we e
pe o med a 4 °C/min hea ing a e om -100 °C o 150 °C using a single can ile e
bending mode wi h a equency o 1 Hz.
Densi y. Densi y measu emen s we e pe o med using a elec onic densi ome e
(Mi age SD-120L) and n-bu anol was used as imme sion liquid. Fo each epo ed alue,
16
Ho man-Weeks ex apola ion and he alues o he equilib ium mel ing poin s ob ained
clea ly show a educ ion wi h inc easing amoun s o PA6, as can be seen in Table SI-1. The
equilib ium mel ing poin da a a e consis en wi h he appa en mel ing poin dep ession
obse ed o he PA410 ich c ys alline phase in Figu e 2b.
Figu e 2b also shows he glass ansi ion empe a u e (Tg) alues ob ained by DMTA
o all he PA6/PA410 blend composi ions. As shown, all blend composi ions display a
single glass ansi ion empe a u e, which is he usual c i e ion o deduce miscibili y in he
amo phous phase 25, 60-65. Mo eo e , he alues a e in e media e be ween hose o he nea
componen s, dec easing linea ly as he PA6 con en inc eased and hus, ollowing he Fox
equa ion o miscible blends 66. Fo his kind o sel -associa ed polyamide blends, usually,
ansamida ion imp o es he miscibili y be ween blend componen s in he mel and in he
amo phous s a e. Simila esul s ha e been ob ained o PA6/PA6I-co-T (PA6/
semia oma ic amo phous polyamide)blends 25, 60-62.
In Figu e 2c, he en halpy o usion, ΔHm, ob ained om he a ea unde he mel ing
peaks o he DSC cu es in Figu e 1b, is plo ed e sus composi ion. ΔHm1 and ΔHm2
alues we e no malized wi h espec o he con en o PA410 and PA6 in he blends,
espec i ely. ΔH o al alues o he blends a e calcula ed using ΔH o al = ΔHm1+ΔHm2 and hey
a e lowe han hose o nea PAs. As shown in Figu e 2c, bo h ΔHm1 and ΔHm2 dec eased as
he second componen in he blend inc eases.
The esul s p esen ed in Figu es 1 and 2 show ha only PA410 ich phase c ys als
a e o med up o a ce ain composi ion (i.e., 20% PA6), beyond which phase seg ega ion
du ing c ys alliza ion is igge ed and wo c ys alline phases a e o med by he blend (i.e., a
PA410 ich c ys alline phase and a PA6 ich c ys alline phase). We assume ha he blends
17
a e o ming a single phase in he mel . This is a easonable assump ion, as he blends a e
miscible in he amo phous s a e, as indica ed by hei single Tg o e he en i e composi ion
ange. On he o he hand, SAXS da a collec ed in he mol en s a e do no show any
sca e ing signal ha could indica e he p esence o wo phases. Ei he he blends o m a
single phase in he mel , o he sca e ing con as is oo weak o show di e ences be ween
he phases. Fu he mo e, phase con as mic oscopy expe imen s in he mel (no shown
he e) indica e a homogeneous mel wi hin he mic oscopic scale o he obse a ion o he
op ical mic oscope. SEM obse a ions we e also made in c yogenically ac u ed
specimens and he e we e no e idences o phase seg ega ion in he ob ained mo phology. I
is possible ha he con as be ween he wo phases is no enough o e eal any di e ence
be ween he phases, bu we we e no able o ind any p oo o phase seg ega ion in he mel
by SAXS, SEM o op ical mic oscopy.
18
020 40 60 80 100
180
185
190
215
220
225
T
c
(ºC)
PA6 con en (w . %)
(a)
T
c2
(PA6)
T
c1
(PA410)
020 40 60 80 100
40
60
220
230
240
250
T
g
T
m1
(PA410)
T
m2
(PA6)
Tempe a u e (ºC)
PA6 con en (w . %)
(b)
020 40 60 80 100
0
10
20
30
40
50
60
∆Hm1 (PA410)
∆Hm2 (PA6)
To al ∆Hm (PA410+PA6)
(c)
∆Hm (J/g)
PA6 con en (w . %)
Figu e 2. (a) C ys alliza ion empe a u e Tc; (b) Mel ing empe a u e Tm and glass
ansi ion empe a u e Tg; (c) Mel ing en halpy ΔHm o he indica ed samples as a unc ion
19
o PA6 composi ion. The shadowed egion deno es he blends ha o m a single c ys alline
phase (i.e., a PA410 ich c ys alline phase).
In summa y, he 10/90 and 20/80 PA6/PA410 blends o m a single PA410 ich
c ys alline phase, wi h unique Tc and Tm alues. Fo blends wi h 30 % PA6 o mo e,
c ys alliza ion d i en phase seg ega ion occu s, and he blends become double c ys alline
wi h coexis ing PA410 ich and PA6 ich c ys alline phases. The amo phous phase is
always miscible, as a single Tg is obse ed in he en i e composi ion ange.
The con ibu ion o each polyamide componen wi hin he c ys alline phase o he
o he componen was oughly es ima ed by no maliza ion o he expe imen al ΔHm alues,
using hei weigh ac ion and by compa ing hese expe imen al alues wi h he expec ed
heo e ical ones (i.e., using a simple ule o mix u es). We ha e calcula ed he inco po a ion
o PA6 chains inside he PA410 c ys als in his way, as an app oxima ion.
As can be seen in Table 2, by inc easing he PA6 con en in he blend, he
inco po a ion o PA6 chains in he c ys alline phase o PA410 dec eased. Fo ins ance, he
inco po a ion o PA6 chains wi hin he PA410 ich c ys alline phase is abou 83% o he
blend wi h 10% PA6, whe eas i dec eased o 4% o he blend wi h 50% PA6. Highe
amoun s o PA6 (mo e han 50%) seems o acili a e phase sepa a ion and p e en he
inco po a ion o any signi ican amoun o PA6 chains wi hin he PA410 ich c ys alline
phase; as judged by he changes in en halpy o mel ing. This beha io can be a ionalized
by looking a Figu e 2c whe e he en halpies o mel ing a e plo ed. The no malized
en halpy o mel ing o he PA410 ich c ys alline phase (i.e.,
∆
Hm1) has a posi i e
de ia ion om a linea ule o mix u es o hose blends ich in PA410 and he highes
posi i e de ia ions a e obse ed o he 10/90 and 20/80 PA6/PA410 composi ions (whe e
20
a single c ys alline phase was o med, as indica ed by he shadowed egion in he igu e).
As expec ed, he no malized en halpy o mel ing o he PA6 ich c ys alline phase (i.e.,
∆
Hm2) exhibi s a nega i e de ia ion om a linea ule o mix u es, as PA6 chains end o be
inco po a ed wi hin he PA410 ich c ys alline phase, he e o e deple ing he amoun o
PA6 ich c ys alline phase.
Table 2. Inco po a ion o PA6 in PA410 c ys als calcula ed by using he changes in
en halpies o he blends
PA6
(% w .)
Theo e ical
ΔHm1 (J/g)
Theo e ical
ΔHm2 (J/g)
Expe imen al
ΔHm1 (J/g)
Expe imen al
ΔHm2 (J/g)
PA6 inco po a ion
(%)
0 59 0 59 0 -
10 53 4.8 57 0 83
20 47 10 55 0 80
30 41 14 44 4 21
40 35 19 38 8 16
50 30 24 31 15 4
60 24 29 24 20 0
70 18 34 15 27 0
80 12 38 9 32 0
90
6
43
3
42
0
100 0 48 0 48 -
* Subsc ip 1 indica es PA410 and subsc ip 2 indica es PA6.
Pola ized Ligh Op ical Mic oscopy (PLOM)
PLOM was used o isually s udy blend mo phology and de ec di e ences in he
sphe uli es mo phology o he samples. PLOM images we e eco ded a e non-iso he mal
21
c ys alliza ion om he mel (see Figu e SI-1). Bo h nea PA410 and PA6 exhibi a
mic osphe uli ic mo phology ha p e en ed any measu emen o g ow h a es as he
nuclea ion densi y was always oo la ge. Howe e , we we e able o de ec he p esence o
one o wo c ys alline phases by he changes expe ienced by he bi e ingence du ing
c ys alliza ion.
Figu es 3a and 3b show PLOM mic og aphs o he 20/80 PA6/PA410 blend ha
o ms a single c ys alline phase (co esponding o a PA410 ich c ys alline phase),
acco ding o he DSC esul s (see Figu e 1). The mic osphe uli ic ex u e was seen o ming
a 230 ºC (a empe a u e a which he PA6 chains a e in he mel o co-c ys allizing wi h
PA410), u he cooling caused no signi ican changes in he mo phology, as seen in he
PLOM mic og aph cap u ed a e he sample was cooled down o 180 ºC and held a ha
empe a u e o 5 min.
On he o he hand, he mi o composi ion sample, i.e., 80/20 PA6/PA410 blend, is
capable o o ming wo sepa a e c ys alline phases upon cooling om he mel acco ding o
Figu e 1. This is co obo a ed in Figu es 3c and 3d, whe e PLOM mic og aphs a e shown.
Fi s , he sample was cooled om he mel and c ys allized a 230 ºC o 5 min, du ig
which he PA410 ich c ys alline phase o med mic oscopic sphe uli es. Then, he sample
was cooled o 180 ºC and kep a ha empe a u e du ing 5 min, du ing which he PA6 ich
c ys alline phase was o med. The ob ious change in bi e ingence be ween Figu e 3c and
3d is a s ong e idence o he second PA6 ich phase o ma ion (as a e he DSC scans
p esen ed in Figu e 1).
22
(a) 20/80 (a e 5 min a 230 °C) (b) 20/80 (a e 5 min a 180 °C)
(c) 80/20 (a e 5 min a 230 °C) (d) 80/20 (a e 5 min a 180 °C)
Figu e 3. PLOM mic og aphs o : (a) he 20/80 PA6/PA410 blend a e i was i s mel ed
a 270 ºC/min o e ase any p ese ed he mal his o y and hen quenched o 230 ºC, whe e i
was allowed o c ys allize o 5 min; (b) same sample as in (a) a e i was quenched o 180
ºC and kep a ha empe a u e o 5 min; (c) he 80/20 PA6/PA410 blend a e i was i s
mel ed a 270 ºC/min o e ase he mal his o y and hen quenched o 230 ºC, whe e i was
allowed o c ys allize o 5 min; (d) same sample as in (c) a e i was quenched o 180 ºC
and held a ha empe a u e o 5 min.
SAXS and WAXS S udy a Room Tempe a u e
100 µm
100 µm
100 µm
100 µm
23
Figu e 4a shows he esul s om Wide-Angle X- ay Sca e ing (WAXS) o nea
PA6, nea PA410, and hei blends. Nea PA6 shows wo cha ac e is ic peaks a q1 = 14.22
and q2=16.77 nm-1, which a e assigned o he (200) and (002/220) plane e lec ions o he
α- o m 59, which has a monoclinic uni cell wi h a = 0.956 nm, b = 1.724 nm (chain axis), c
= 0.801 nm, β = 67.5º. PA410 shows wo well de ined in ense peaks loca ed a q1 = 14.30
and q2 = 16.70 nm-1 (alloca ed o he (100) and (010/110) plane e lec ions) and a small
peak a 4.04 nm-1 assigned o (001) plane. The uni cell pa ame e s o PA410 a e: a = 0.490
nm, b = 0.532 nm, c = 1.98 nm (chain axis), α = 49º, β = 77º and γ = 63º 63 (no e ha he
de ini ion o chain axis a e di e en o he wo polyme s). The mos in ense c ys alline
e lec ions o e lap and make he dis inc ion be ween he wo ypes o c ys als e y di icul .
Figu e 4b shows he d-spacing e alua ed om he peak posi ions o he WAXS pa e ns o
hese blend samples. The d-spacings ba ely showed any change wi h composi ion.
Al hough he wo main e lec ion peaks o polyamides a e o e lapped, i is possible o
de ec he p esence o PA410 c ys als in he blends h ough a small peak a q = 4.04 nm-1
which co esponds o he (001) plane.
A clea di e ence be ween he wo polyamides is he in ensi y a io o he wo main
peaks: Iq1 / Iq2. Fo PA6 and PA410, he in ensi y a ios a e 1.15 and 2.73, espec i ely.
Figu e SI-2 shows an example o he ex ac ion me hod used o calcula e he in ensi y a io
alues om WAXS pa e ns.
24
4 8 12 16 20
(a)
(001) (010)/(110)
PA6
90/10
80/20
70/30
60/40
50/50
40/60
30/70
20/80
10/90
In ensi y (a.u.)
q (1/nm)
PA410
(100)
(002/220)
(200)
020 40 60 80 100
3
3.3
3.6
3.9
4.2
4.5
4.8
q
2
q
1
(b)
d-spacing (Å)
PA6 con en (w . %)
020 40 60 80 100
1
1.5
2
2.5
3
Calcula ed da a by
polyamide weigh con ibu i
o
n
Expe imen al da a
In ensi y a io q
1
/q
2
PA6 con en (w . %)
(c)
Figu e 4. (a) WAXS pa e ns o all PA6/PA410 blend samples a oom empe a u e. (b)
d-spacing changes e sus PA6 con en . (c) Changes in in ensi y a io o he wo main
peaks, q1 and q2, in PA6/PA410 blends e sus PA6 con en .
The shadowed egion
deno es he blends ha o m a single c ys alline phase (i.e., a PA410 ich c ys alline
phase).
25
The a io o hese peaks e sus PA6 con en is plo ed in Figu e 4c. I he blend
samples ollowed a simple mixing ule wi hou any change o each indi idual componen ,
he in ensi y a io o hese peaks would be an a e age o he wo peaks based on hei
weigh con ibu ion (black line in Figu e 4c). Howe e , i can be seen ha he expe imen al
da a (pink pen agons in Figu e 4c) showed a clea posi i e de ia ion om a simple ule o
mix u es o composi ions wi h less han 50 % PA6.
As men ioned in he DSC sec ion, he blend samples wi h less han 50% PA6
showed calo ime ic signs o inco po a ion o PA6 chains in o he PA410 ich phase
c ys als (see Table 2). These changes in he in ensi y a io o he wo main peaks wi h he
composi ion a e addi ional e idence o he inco po a ion o PA6 chains in he PA410 ich
c ys al phase o blends wi h less han 50 % PA6. In pa icula , he maximum posi i e
de ia ion om a ule o mix u es is obse ed o he wo blends (i.e., he 10/90 and 20/80
PA6/PA410 blends) ha con ain only a single c ys alline phase as e idenced by DSC (a
PA410 ich c ys alline phase); hey a e highligh ed by he shaded egion in Figu e 4c.
SAXS pa e ns o nea polyamides and all blend samples a 25 ºC a e shown in
Figu e 5a. Su p isingly, all samples exhibi ed a single peak ha can be in e p e ed as he
sca e ing a ibu able o lamella s acks, and he long pe iods (Lp) we e calcula ed om he
qmax alues a e Lo en z co ec ion by Equa ion 1.
𝐿𝐿𝑝𝑝= 2𝜋𝜋
𝑞𝑞𝑚𝑚𝑚𝑚𝑚𝑚
Eq (1)
SAXS pa e ns in Figu e 5a exhibi ed a single peak co esponding o lamella
packing o abou 7.5-10.0 nm depending on blend composi ion. Figu e 5b p esen s he
changes in he long pe iod (Lp) as a unc ion o PA6 con en . In he 0-60% PA6 ange, Lp
32
40/60
2950±40
72.4±2.2
96±30
31±5
50/50
2930±40
73.4±2.5
129±51
33±2
60/40
2920±160
75.9±4.9
64±63
33±4
70/30
2800±180
72.7±5.9
118±75
36±1
80/20
2690±30
71.8±1.0
129±73
36±1
90/10
2610±30
70.0±0.7
108±66
41±2
100/0
2500±10
67.0±1.8
157±42
44±2
Acco ding o li e a u e, he e a e h ee ac o s ha can be di e en in he nea
componen s and in he blends and, he e o e, in luence he Young’s modulus: c ys allini y
69-70, ee olume 69-70 and o ien a ion 69. As discussed in p e ious sec ions, he blends
showed c ys alline con en s below he linea i y be ween he pu e polyamides, showing a
nega i e de ia ion om he ule o mix u es (Figu e 2c). The e o e, his canno be he
cause o he obse ed posi i e modulus beha iou .
Possible blending-induced changes o he ee olume we e s udied by means o
densi y measu emen s. Figu e SI-8 shows he densi y alues o PA6/PA410 blends. As can
be obse ed, he blends showed alues ha a e in e media e be ween hose o he pu e
componen s, wi h a sligh posi i e de ia ion om he simple addi i i y ule. Simila esul s
ha e been obse ed in se e al o he wo ks 69-74. In his case, he 50/50 PA6/PA410
composi ion, o ins ance, shows a posi i e de ia ion o 0.002 g/cm3 wi h espec o
linea i y (i.e., a 0.20 % inc ease). The same composi ion shows a posi i e de ia ion in he
Young’s modulus o 256 MPa (9.6 %). Vallejo and cowo ke s 70 obse ed compa able
a ia ions in speci ic olume and modulus o miscible PEI/PBT blends. In ac , hey
33
a ibu ed he modulus beha iou o he changes obse ed in he speci ic olume o he
blends.
A possible change in he le el o o ien a ion o he blends wi h espec o he pu e
componen s was s udied by means o bi e ingence measu emen s. Al hough he s anda d
de ia ion and dispe sion o he da a ob ained was high, a posi i e a e age de ia ion o 68%
in bi e ingence was obse ed o all he composi ions.
I is widely known ha he le el o o ien a ion can a ec he Young’s modulus
beha iou 69, 71. As a consequence, injec ion moulded ma e ials end o show highe moduli
han, o ins ance, comp ession moulded ma e ials, as he o me a e usually mo e o ien ed
69, 71 and his, along wi h densi y, con ibu es o he posi i e de ia ion o modulus.
020 40 60 80 100
2200
2400
2600
2800
3000
3200
3400
Young's modulus (MPa)
PA6 con en (w %)
(a)
020 40 60 80 100
50
60
70
80
90
100
Yield s ess (MPa)
PA6 con en (w %)
(b)
34
020 40 60 80 100
0
40
80
120
160
200
240
S ain a b eak (%)
PA6 con en (w %)
(c)
020 40 60 80 100
0
20
40
60
80
100
Impac s eng h (J/m)
PA6 con en (w %)
(d)
Figu e 8. Young’s modulus (a), yield s ess (b), s ain a b eak (c), and impac s eng h
(d) o PA6/PA410 blends e sus PA6 con en .
These esul s poin o he Young’s modulus beha iou being a ec ed by bo h he
a o emen ioned nega i e de ia ion in he olume o mixing and he changes in he le el o
o ien a ion in he blends wi h espec o he nea polyamides. Howe e , i seems ha he
con ibu ion o he o me o Young’s modulus is s onge han ha o he la e , as he
endency obse ed in bi e ingence does no exac ly i ha o he Young’s modulus.
Figu e 8b illus a es he yield s ess alues o he blends, which co espond o he
ensile s eng h alues in all cases. As can be seen, his pa ame e dec eased as he
concen a ion o PA6 in he blend inc eased, showing a pe o mance close o linea i y
be ween he nea componen s. In p e ious wo ks, i has been obse ed ha he yield s ess
usually ollows he same endency as he Young’s modulus 69-70. Howe e , examples o
miscible sys ems in which he posi i e de ia ion obse ed in he Young’s modulus is no
ep oduced in he yield s ess 64 (and ice e sa 71) a e also a ailable in li e a u e. As a
ma e o ac , miscible blends usually show a mechanical pe o mance ha is in e media e
35
be ween ha o he nea componen s, as a consequence o he dispe sion o he componen s
a a molecula scale 69.
Figu e 8c shows he s ain a b eak alues o he PA6/PA410 blends e sus he PA6
con en . As can be obse ed, all he composi ions main ained he duc ile na u e o bo h nea
componen s and alues inc eased uni o mly as he PA6 con en inc eased, ollowing he
ule o mix u es. Al hough posi i e 65, 72-73, 75 and nega i e 68, 76 de ia ions ha e also been
obse ed in li e a u e, his is he usual beha iou in miscible blends 69, 77. The s anda d
de ia ions o he alues o all he composi ions we e signi ican ly high, p obably because
all he samples b oke du ing he cold d awing p ocess, which usually leads o high, hough
non-signi ican , sca e ing o he esul s ob ained.
Figu e 8d shows he impac s eng h alues o he blends as a unc ion o he PA6
con en . As can be obse ed, bo h PAs and hei blends show low impac esis ance alues,
wi h a sligh nega i e de ia ion om he simple ule o mix u es. This is because
polyamides a e e y c ack-sensi i e ma e ials 78-80; hence, no ched specimens show b i le
ac u e in high-speed de o ma ion es s such as impac es s.
Nega i e de ia ions in impac esis ance ha e o en been obse ed in miscible
polyme blends 18, 68, 70-73 and, in many cases 68, 70, 72-73, hey ha e been a ibu ed o he
densi ica ion o he amo phous phase – mo e speci ically, o he loss o ee olume. Thus,
i can be s a ed ha in PA6/PA410 blends he posi i e de ia ion obse ed in he densi y is
esponsible o he impac s eng h beha iou .
Fu he mo e, in c ack-sensi i e ma e ials such as nylons, i has been p oposed 18 ha
he p esence o weak poin s wi hin he ma e ial (such as sphe uli e bounda ies, nodes and
36
in e lamella egions18, o e en a pa ially miscible componen 71) could ease c ack
ini ia ion and p opaga ion, hus educing he impac pe o mance o he blends wi h espec
o he one o pu e componen s.
CONCLUSIONS
Blending o e s an e ec i e way o uning he physical p ope ies o polyme s. In
his wo k, we ha e sys ema ically s udied he miscibili y, c ys alliza ion s uc u e,
mo phology, and mechanical p ope ies o PA410 and PA6 blends co e ing he en i e
composi ion ange. The blends exhibi ed only one Tg in be ween he Tg o he indi idual
nea polyme s, which, oge he wi h he PLOM obse a ion indica ed comple e miscibili y
in he amo phous phase and no mac oscopic phase sepa a ion. DSC and WAXS esul s
indica ed ha a ac ion o he PA6 chains coc ys allized wi hin he PA410 uni cells when
he ac ion o PA6 was less han 50%. Fo he blends con aining a majo i y ac ion o
PA6, sepa a e c ys alliza ion o PA6 ich and PA410 ich phases was a o ed. The
mechanical p ope ies o he blends, such as Young’s modulus, impac s eng h and s ain
a b eak changed wi h composi ion loca ing in be ween he nea polyme s, which ag ees
wi h he ypical cha ac e o compa ible blends.
ACKNOWLEDGEMENTS
We would like o acknowledge he inancial suppo om he BIODEST p ojec ; his
p ojec has ecei ed unding om he Eu opean Union's Ho izon 2020 esea ch and
inno a ion p og amme unde he Ma ie Skłodowska-Cu ie g an ag eemen No 778092.
We also hank inan ial suppo om he Basque Go e nmen h ough p ojec IT309-19.
G.L., D.W. and A. J. M. hank he suppo om he Na ional Key R&D P og am o China
37
(2017YFE0117800) and he Na ional Na u al Science Founda ion o China (51820105005,
21922308). I. O aegi acknowledges he g an awa ded by he Basque Go e nmen . G.L. is
g a e ul o he You h Inno a ion P omo ion Associa ion o he Chinese Academy o
Sciences (Y201908). The POLYMAT/UPV/EHU eam would like o hank unding om
ALBA synch o on acili y h ough g an ed p oposal numbe : 2018093081 (Ma ch 2019)
and he Basque Go e nmen h ough g an IT1309-19.
Suppo ing In o ma ion (SI)
The equilib ium mel ing poin Tm0 alues(Table SI-1), op ical mic og aphs o he samples
(Figu e SI-1), he calcula ion me hod o he in ensi y a io om WAXS da a (Figu e SI-2),
WAXS da a (Figu e SI-3), SAXS da a (Figu e SI-4), he long pe iod alues o he samples
(Figu e SI-5), Lp alues a 210 ºC (Figu e SI-6), he chemical s uc u es o PA6, PA410 and
PA6/PA410 blend (Figu e SI-7) and he densi y alues o PA6/PA410 blends (Figu e SI-8).
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