ORIGINAL ARTICLE
Jou nal o Polyme s and he En i onmen (2025) 33:512–527
h ps://doi.o g/10.1007/s10924-024-03377-4
F om he con amina ion o oceans wi h pe sis en plas ic
was es o he ha m ul e ec s o mic oplas ic inges ion by
wildli e, he de imen al e ec s o con en ional plas ics on
biodi e si y and ecosys em heal h a e becoming inc eas-
ingly e iden [2]. Bioplas ics a e a p omising and sus ain-
able al e na i e p oposed by he scien i ic communi y o
deal wi h his en i onmen al c isis.
De i ed om enewable esou ces such as plan s a ches,
ag icul u al byp oduc s, o mic obial e men a ion, bioplas-
ics p esen a compelling solu ion o mi iga e he ecologi-
cal oo p in associa ed wi h con en ional plas ics [3]. The
use o biobased and biodeg adable plas ics (pa icula ly
de i ed om was e and byp oduc s o he ag o- ood indus-
y) eme ges as a cu ing-edge s a egy o add ess he en i-
onmen al challenges associa ed wi h con en ional plas ics
[4]. In con as o o he ypes o bioplas ics, hose based
on ag icul u al aw ma e ials o e signi ican ad an ages.
Fi s ly, ha nessing was e and byp oduc s om his sou ce
In oduc ion
Con en ional plas ics ha e eme ged as a signi ican h ea o
he delica e balance o ou ecosys ems in oday’s en i on-
men al landscape [1]. The ubiqui ous use o adi ional plas-
ics in a ious indus ies has led o widesp ead pollu ion,
ad e sely impac ing land and aqua ic en i onmen s alike.
Ma ía Alonso-González
[email p o ec ed]
1 Depa amen o de Ingenie ía Química, Escuela Poli écnica
Supe io , Uni e sidad de Se illa, Se illa 41011, Spain
2 Depa amen o de Ingenie ía Química, Facul ad de Química,
Uni e sidad de Se illa, Se illa 41012, Spain
3 Depa men o Chemical Enginee ing Ma e ials
En i onmen , Uni e si y o Rome La Sapienza and UdR
INSTM, Via Eudossiana 18, Rome 00184, I aly
Abs ac
Con en ional plas ics pose en i onmen al h ea s due o hei non-biodeg adable na u e and hei eliabili y on ossil
esou ces, leading o he explo a ion o sus ainable al e na i es. In his sense, biodeg adable bioplas ics de i ed om
enewable esou ces o e a p omising solu ion o mi iga e ecological impac s. This s udy ocuses on he combina ion
o ex usion and injec ion molding o he de elopmen o ice b an-based bioplas ics. Being a by-p oduc om he ice
indus y ich in s a ches and p o eins, ice b an is an abundan and non-expensi e esou ce ha con ibu es o an enhanced
was e managemen and ep esen s a s ep o wa d in in eg a ing he p inciples o a ci cula economy. This s udy del es
in o he op imiza ion o p ocessing condi ions h ough a Design o Expe imen app oach. Fo his pu pose, he numbe
o ex usion s eps, cylinde and mold empe a u es, and injec ion p essu e we e in es iga ed. The esul s showed ha wo
ex usion s eps led o a signi ican inc ease o app oxima ely 22.8% in Young’s modulus and 37.5% in ensile s eng h
compa ed o a single ex usion cycle. This enhancemen was a ibu ed o he acili a ion o s a ch gela iniza ion and
biopolyme -plas icize in e ac ions (achie ing he moplas ic s a ch and p o ein plas iciza ion). Simila ly, manipula ion o
injec ion empe a u es and p essu e had no able e ec s on ensile p ope ies, highligh ing he complex in e play be ween
p ocessing pa ame e s. In pa icula , when using cylinde and mold empe a u es o 110 °C and 180 °C, espec i ely,
along wi h 800 ba , i was possible o achie e a u he enhancemen in ensile p ope ies, wi h an inc ease o 97.1% in
Young’s modulus and o e 100% in ensile s eng h. O e all, his esea ch unde sco es he impo ance o unde s anding
he ela ionship be ween p ocessing condi ions and biopolyme in e ac ions o bioplas ic p oduc ion.
Keywo ds Rice b an · Ci cula Economy · Bioplas ics · Ex usion · Injec ion Molding · Design o Expe imen
Accep ed: 1 Augus 2024 / Published online: 3 Augus 2024
© The Au ho (s) 2024
Op imiza ion o P ocessing Condi ions o Rice B an-based Bioplas ics
Th ough Ex usion and Injec ion Molding
Ma íaAlonso-González1,2,3· ManuelFelix1· Albe oRome o2· ClaudiaSe gi3· I eneBa asso3· Fab izioSa asini3
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Jou nal o Polyme s and he En i onmen (2025) 33:512–527
no only educes eliance on non- enewable esou ces bu
also ackles he issue o ag icul u al was e managemen by
ans o ming hem in o aluable aw ma e ials wi h speci ic
applica ions [5]. Fu he mo e, hei e ec i e biodeg ada-
ion in speci ic en i onmen s, such as compos ing, p o ides
an addi ional solu ion o he long- e m plas ic was e accu-
mula ion p oblem. In his ega d, bioplas ics de i ed om
ag icul u al was e no only ep esen a mo e sus ainable
al e na i e bu also cons i u e a c ucial s ep owa ds build-
ing a mo e en i onmen ally espec ul u u e [6].
The selec ion o ice b an as a p ima y aw ma e ial o
bioplas ic p oduc ion is suppo ed by i s nume ous ad an-
ages based on i s chemical composi ion and a ailabili y.
Rice b an is an abundan byp oduc o ice milling p o-
cesses, mo e han 60 million me ic ons we e p oduced in
2017 [7], p o iding a sus ainable sou ce ha simul aneously
add esses he issue o ag icul u al was e disposal [8] and i is
aligned wi h he p inciples o ci cula economy, u ning an
o he wise unde u ilized byp oduc in o a aluable esou ce
o sus ainable ma e ials [9]. In his sense, ice b an p es-
en s a no ewo hy eposi o y o p o eins and s a ches, bo h
o which se e as biopolyme s wi h immense po en ial o
bioplas ic de elopmen [10, 11]. Th ough app op ia e p o-
cessing echniques, such as he momechanical ea men s,
hese p o eins and s a ches can be e ec i ely ans o med
in o e sa ile bioplas ic ma e ials [12, 13].
Among he many p ocessing echniques, ex usion and
injec ion molding play key oles. Ex usion is a widely
employed me hod ha allows he e icien and con inuous
p oduc ion o bioplas ics, making i e sa ile o a ange o
applica ions [14, 15]. On he o he hand, injec ion mold-
ing is pa icula ly ad an ageous o p oducing in ica e
and cus omized bioplas ic p oduc s [16, 17]. Bo h ex u-
sion and injec ion molding echniques o e scalabili y and
ep oducibili y, making hem in eg al o he indus ial-scale
manu ac u ing o bioplas ics. By ha nessing hese ech-
niques, he mechanical p ope ies and geome ical p ecision
o bioplas ics can be op imized, pa ing he way o hei
widesp ead adop ion as eco- iendly al e na i es in di e se
applica ions. Howe e , cu en bioplas ics o en ace signi -
ican limi a ions, including na ow p ocessing windows and
poo mechanical p ope ies, such as lowe ensile s eng h
and duc ili y compa ed o con en ional plas ics. Addi ion-
ally, hey exhibi lowe ba ie p ope ies, which can a ec
hei e ec i eness in p o ec ing agains mois u e and gases.
Fu he mo e, al hough egula ions could bene i hem, he
highe p oduc ion cos s and limi ed scalabili y o bioplas-
ics p esen challenges o widesp ead adop ion and com-
pe i i eness in he ma ke [18]. Fo hese easons, in-dep h
esea ch is equi ed o o e come po en ial disad an ages.
P e ious in es iga ions we e ocused on he op imiza-
ion o he ice b an and plas icize s o be employed [19–22]
and he in luence o some injec ion molding pa ame e s has
been al eady add essed [23, 24]. This s udy aims o op i-
mize he p ocessing condi ions o he de elopmen o ice
b an-based bioplas ics by combining ex usion and injec-
ion molding. P ocessing pa ame e s such as he numbe
o ex usion cycles, he empe a u e o he cylinde , he
empe a u e o he mold and he injec ion p essu e we e
e alua ed and in es iga ed h ough a Design o Expe i-
men (DoE) app oach o es ablish a ela ionship be ween
he p ocessing condi ions and he inal p ope ies and o
ailo hose ega ding speci ic applica ions. To his end, a
comp ehensi e cha ac e iza ion encompassing mechani-
cal, he mal and chemical and mic os uc u al analysis was
conduc ed on he sys ems, using mechanical p ope ies as
he main pa ame e s o sys em op imiza ion. The no el y
o his s udy lies in he use o a whole by-p oduc om he
ag o- ood indus y, speci ically ice b an, ins ead o isola ed
p o eins o s a ches. By employing only a de a ing ea -
men , his esea ch add esses he complexi y a ising om
he in e ac ions be ween he a ious phases p esen in ice
b an. The e o e, an in es iga ion in o op imizing p ocess-
ing condi ions ia ex usion and injec ion molding, using
a design o expe imen s app oach, is c ucial o unde s and
how his complex ma e ial beha es.
Expe imen al
Ma e ials
Rice b an (RB) om indica ice, p o ided by He ba Ricemi-
lls (San José de la Rinconada, Se ille, Spain), was used as
he aw ma e ial o his s udy. The composi ion o he ice
b an, as de e mined by A.O.A.C. me hods [22], was ound
o be 16 w % mois u e, 13 w % ashes, 2 w % lipids, 17 w %
p o eins, 28 w % ibe (comp ising cellulose and hemicel-
lulose), and 24 w % s a ch. I is impo an o no e ha he
ice b an unde wen a s eaming he mal ea men , a p ocess
also ca ied ou by He ba Ricemills. Glyce ol (Gly), used
as he plas icize , was sou ced om Sigma-Ald ich (USA).
Dis illed wa e (W) was used as needed in he expe imen al
p ocedu es.
De a ed Rice B an (DRB)
Upon ini ial ecep ion, he lipid con en in he ice b an
exceeded 20 w %. Howe e , o achie e a educed lipid
con en o less han 2 w %, a de a ing p ocedu e was
implemen ed using he same me hodology de ailed in p io
s udies [22]. B ie ly, ice b an (< 500 μm) was mixed wi h
hexane in a p opo ion o 1:10 w/ . The esul ing suspen-
sion unde wen magne ic s i ing a 25 ºC o 24 h, ollowed
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Jou nal o Polyme s and he En i onmen (2025) 33:512–527
by cen i uga ion a 5,000 pm o 10 min. The solid ac-
ion was hen sepa a ed om he supe na an , con aining he
hexane phase and he ex ac ed lipids. The sepa a ed solid
ac ion was subsequen ly d ied in a ume hood. This de a -
ing p ocess was epea ed wice. A e de a ing, he ice
b an was g ound and sie ed o a size smalle han 200 μm
(70 mesh) o he balanced p ope ies o his ac ion [20],
esul ing in he de elopmen o he DRB sys em.
Bioplas ics P epa a ion
D y-blend P epa a ion
The samples we e p oduced h ough a wo-s ep p oce-
du e, beginning wi h he o mula ion o a d y-blend by
combining DRB, Gly, and W. This p elimina y d y-blend
app oach, achie ed h ough di e en d ying s eps along
wi h he addi ion o he plas icize s, acili a es subsequen
ex usion, esul ing in a inal ma e ial wi h minimal exuda-
ion phenomenon, ha is, mig a ion o he plas icize o e
ime. This a ou able ou come is p ima ily a ibu ed o he
compa ibili y o p o ein and polysaccha ide chains and he
polyols used as plas icize s (Gly in his case), as epo ed by
Chi ac e al. [25].
To his end, he DRB unde wen o e nigh d ying a
70 ºC in an o en AG-Sys em om F a elli Galli (I aly) o
elimina e ee wa e (app oxima ely 9 w %, depending on
ambien condi ions). Subsequen ly, he d ied powde was
subjec ed o mechanical s i ing a 100 pm using an A go
Lab AM20-D s i e (I aly), inco po a ing Gly g adually
un il a uni o m mix u e was achie ed. The blend was hen
d ied a 110 ºC in he o en o 1 h, acili a ing he ola-
iliza ion o bound wa e h ough di usion exchange wi h
Gly molecules in e ac ing wi h p o ein and s a ch mac o-
molecules. A e cooling, wa e was added o he d y-blend
ollowing he same p ocedu e, slowly in oducing i in o he
mix u e unde mechanical s i ing. This esul ed in a o mu-
la ion comp ising 60 w % DRB, 30 w % Gly, and 10 w %
W, ensu ing an op imal mois u e con en (d y-blends).
Ex usion
The d y-blends we e in oduced in o he hoppe o a pa allel
co- o a ing win-sc ew ex ude (The mo Scien i ic P ocess
11, The mo Fishe Scien i ic, Wal ham, MA, USA), wi h
11 mm ully segmen ed sc ews and a L/D a io o 40. This
ex ude was equipped wi h 8 hea ing zones and a s anda d
sc ew con igu a ion wi h con eying elemen s (helix pi ch
o 1 L/D) in e spaced among h ee mixing sec ions ob ain-
ing al e na ing elemen s wi h 0º and 90º (leng h ¼ L/D).
The sc ew speed (15 pm) and empe a u e p o ile we e se
based on p e iously op imized condi ions ( esul s no pub-
lished ye ), main aining a cons an eeding a e. The em-
pe a u e p o ile was ailo ed o an ex ude wi h 8 hea ing
zones, wi h empe a u es se a 90–100–110–120–120–110–
105–100 °C, om hoppe o die. The ex usion p ocess was
conduc ed once and wice o e alua e he po en ial bene i s
o a second un, p o iding an ex ended esidence ime o
biopolyme plas i ica ion.
Injec ion Molding
Following ex usion, he pelle s unde wen injec ion
molding (Haake MiniJe II P o, The mo Fishe Scien i ic,
Wal ham, MA, USA) unde a ying p ocessing condi ions,
including adjus men s o he cylinde empe a u e (Tc),
mold empe a u e (Tm) and applied p essu e (P), whe e all
he specimens emained in he mold o 200 s. By hese
means, ensile dogbone specimens we e ob ained. In o de
o op imize he injec ion molding phase and o maximize
he mechanical p ope ies o he esul ing bioplas ics, he
a o emen ioned pa ame e s we e selec ed, exploi ing he
DoE echnique and changing hem on wo le els, low (–)
and high (+), o ob ain a 23 ull ac o ial design. Figu e
S1 shows an image o he inal bioplas ics, while Table 1
de ails he low and high le els o he h ee pa ame e s ha
we e used in he ull ac o ial design as well as he designa-
ion o he di e en ob ained sys ems. In his way, 110 ºC
and 140 ºC we e chosen as low and high le els o he em-
pe a u e o he cylinde a e obse ing ha inc easing he
empe a u e o he cylinde om 50 ºC o 110 ºC esul ed
in imp o ed mechanical p ope ies. This imp o emen is
likely asc ibed o he o e s epping o he bioplas ic glass
ansi ion empe a u e, a c i ical poin a which he ma e ial
unde goes a ansi ion om a igid o a mo e lexible s a e.
The ole o his ansi ion in enhancing mechanical p ope -
ies has been es ablished in p e ious wo ks, p o iding sup-
po ing e idence o ou obse ed empe a u e-dependen
e ec s. Fo he empe a u e o he mold, 150 ºC and 180 ºC
we e selec ed as low and high le els, based on a p e ious
s udy ha demons a ed he bene icial e ec o inc easing
he empe a u e o he mold on he mechanical p ope ies
Table 1 Designa ion o he di e en p ocessed biopolyme s
Sys em Ex usion Injec ion molding
S eps Tc (ºC) Tm (ºC) P (ba )
E1 150 150 500
E2 250 150 500
E2I1 2110 (–) 150 (–) 500 (–)
E2I2 2110 (–) 150 (–) 800 (+)
E2I3 2140 (+)150 (–) 500 (–)
E2I4 2140 (+)150 (–) 800 (+)
E2I5 2110 (–) 180 (+)500 (–)
E2I6 2110 (–) 180 (+) 800 (+)
E2I7 2140 (+) 180 (+)500 (–)
E2I8 2140 (+) 180 (+) 800 (+)
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Jou nal o Polyme s and he En i onmen (2025) 33:512–527
es s we e conduc ed using a DSC 214 Polyma ins umen
(Ne zsch, Selb, Ge many) in a ni ogen a mosphe e (40 mL/
min), employing a hea ing/cooling a e o 10 ºC/min. The
calo ime ic es s in ol ed hea ing/cooling amps anging
om − 40 ºC o 300 ºC. Key empe a u es, such as he glass
ansi ion empe a u e (Tg) and mel ing empe a u e (T′m)
we e ob ained om he DSC cu es.
To assess he he mal s abili y o he samples, he mo-
g a ime ic analysis (TGA) was pe o med. The specimens
we e placed in alumina c ucibles and subjec ed o hea -
ing om 25 ºC o 800 ºC a a hea ing a e o 10 ºC/min
in an ine ni ogen a mosphe e (40 mL/min). All expe i-
men s we e conduc ed using a TG209 F1 Lib a ins umen
(Ne zsch, Selb, Ge many).
Fou ie T ans o m In a ed Spec oscopy (FTIR)
The FTIR analysis was conduc ed on he aw ma e ial,
namely, he un ea ed DRB, and on one o he samples
p ocessed a 150 °C and ano he a 180 °C as Tm (sys ems
E2I1 and E2I5, espec i ely). The equipmen used was an
In enio X spec ome e (B uke ) o ob ain abso bance spec-
a be ween 4000 and 750 cm−1.
Scanning Elec on Mic oscopy (SEM)
Mic og aphs o he bioplas ics ac u e su ace we e aken
by SEM o assess he mic os uc u e o he di e en speci-
mens and he ailu e mechanism. To his end, a ield-emis-
sion scanning elec on mic oscope (FE-SEM) MIRA 3 by
Tescan (B no, Czech Republic) was used. The samples we e
coa ed wi h a hin laye o gold by spu e ing o p e en
cha ging and hey we e hen obse ed a 10 kV accele a ion
ol age.
S a is ical Analyses
S a is ical analysis was used o disclose he ela ionship
be ween he injec ion molding pa ame e s selec ed and he
esul ing mechanical p ope ies and i was di ided in wo
di e en s eps. A i s , in e en ial s a is ic was used o de e -
mine whe he he injec ion molding pa ame e s selec ed as
independen a iables, i.e., Tc, Tm and P, ha e an ac ual
e ec on he dependen a iable, i.e., ensile modulus, en-
sile s eng h and elonga ion a b eak, by mee ing he c i e ia
o s a is ical signi icance. The analysis was pe o med by
applying he F- es (ANOVA) and selec ing a p- alue < 0.05
as a s a is ically signi ican limi . This means ha a p- alue
lowe han 0.05 con i ms ha he pa ame e unde con-
side a ion had an ac ual e ec on he dependen a iable.
The analysis was pe o med wi h he R-s udio pla o m,
o ice b an-based bioplas ics [23]. Ne e heless, he em-
pe a u e was no inc eased beyond 180 ºC because u he
inc emen s led o samples ha we e comple ely bu n , eas-
ily b eaking upon demolding, as can be seen in Figu e S2.
Finally, 500 ba and 800 ba we e selec ed as low and high
le els o injec ion p essu e o es ablish a compa ison wi h
p e ious s udies and add ess he sui abili y o bioplas ics
o ma ion d i en by high injec ion p essu e [26].
Rega ding he ex usion p ocedu e, designa ion o he
sys ems is based on E1 o 1 s ep and E2 o 2 s eps. Since
E2 was selec ed based on he mechanical p ope ies o he
esul ing samples (injec ed a Tc = 50 ºC, Tm = 150 ºC
and P = 500 ba ), he es o he sys ems whe e he injec-
ion molding condi ions we e changed a e designa ed as
E2I1-E2I8.
Cha ac e iza ions
Tensile Tes s
Tensile es s we e ca ied ou on he samples using a Zwick/
Roell Z010 uni e sal es ing machine. Measu emen s we e
pe o med a oom empe a u e based on he ISO 527-2
s anda d [27] using a s ain a e o 1 mm/min, a load cell
o 1 kN, a g ip- o-g ip sepa a ion o 53 mm and an ex en-
some e wi h a 30 mm gauge leng h. S ess-s ain cu es
we e ob ained, which we e used o calcula e he alues o
Young’s modulus (E), ensile s eng h (σmax) and s ain a
b eak (εmax) o he di e en sys ems de eloped. A leas
h ee specimens we e es ed o each sys em.
Dynamic Mechanical The mal Analysis (DMTA)
DMTA es s we e pe o med on a DMA850 heome e
(TA ins umen s, USA) wi h ec angula p obes measu ing
10 mm × 8 mm × 1.5 mm using he ilm clamp in ension
mode. Fi s ly, he linea iscoelas ic ange was de e mined
by s ain sweep es s a a cons an equency o 1 Hz wi hin a
de o ma ion ange om 0.01–1%. F om his es , he c i ical
de o ma ion was de e mined, and a sui able de o ma ion was
selec ed wi hin he linea iscoelas ic ange (LVR) o ca y
ou he ollowing es s. F equency sweep es s be ween 0.5
Hz and 20 Hz a oom empe a u e and empe a u e amps
be ween − 10 ºC and 160 ºC a a cons an equency o 1 Hz
we e ca ied ou . F om hese es s, he alues o he s o age
modulus (E′), he loss modulus (E″) and he an δ = E″/E′
we e ob ained as a unc ion o equency and empe a u e.
The mal Cha ac e iza ion
Di e en ial Scanning Calo ime y (DSC) was employed
o examine he he mal cha ac e is ics o he sys ems. The
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Jou nal o Polyme s and he En i onmen (2025) 33:512–527
an inc ease o 22.8% in s i ness and 37.5% in s eng h was
obse ed. Fo his eason, wo ex usion s eps we e selec ed
o he es o he es s used o op imize he injec ion molding
condi ions. The longe p ocessing ime unde empe a u e,
shea o ces and he p esence o plas icize s could imp o e
s a ch gela iniza ion and he c ea ion o mo e biopolyme -
plas icize in e ac ions [28, 29] wi h bo h he s a ch and
p o ein ac ions, esul ing in a ma e ial mo e sui able o be
manu ac u ed by he mo-mechanical me hods.
On he o he hand, he e ec s o inc easing he cylinde ’s
empe a u e we e es ed while keeping he o he wo pa am-
e e s, Tm and P, cons an . In his way, he Tc was inc eased
om 50 ºC (E2) o 110 ºC (E2I1) and o 140 ºC (E2I3) o
Tm = 150 ºC and P = 500 ba . In his case, he inc easing
Tc om 50 ºC esul ed in enhancemen s in bo h σmax and
εmax, imp o ing om 1.1 o 1.6 MPa and om 4.0 o 6.9%,
espec i ely when using Tc = 110 ºC, he Young’s modulus
emaining a 70 MPa. The bene icial e ec was no obse ed
when u he inc easing he Tc o 140 ºC, e ealing simila
alues o σmax (1.8 MPa) and εmax (7.0%). As E dec eased
o 42 MPa, no u he inc eases o he Tc we e p oposed.
Simila endencies we e obse ed when inc easing he Tc
o bo h Tm = 150 and 180 ºC and P = 800 ba (compa ing
E2I2 o E2I4 and E2I6 o E2I8), wi h highe εmax bu lowe
E and σmax. A highe empe a u es he e is mo e mobili y o
he biopolyme chains because he glass ansi ion has ully
de eloped so i is easie o hem o low and comple ely ill
he mold ca i y, leading o mo e compac bioplas ics wi h
enhanced mechanical p ope ies [30]. Indeed, he empe a-
u e inc ease is bene icial only o some ex en because oo
high empe a u es will accele a e c osslinking be o e illing
he mold ca i y and e en plas icize e apo a ion dec eases
he p ocessabili y o he ma e ial. Fo hese easons, inc eas-
ing he empe a u e o he cylinde om 110 ºC o 140 ºC
does no lead o clea imp o emen s when balancing he 3
pa ame e s unde s udy. The only imp o emen wi h Tc =
140 ºC is obse ed when using Tm = 180 ºC and P = 500 ba
(E2I5 o E2I7) whe e he high empe a u e combined wi h
he lowe P led o plas icize e apo a ion, esul ing in s i e
bioplas ics wi h highe load capaci y bu educed lexibili y.
When s udying he e ec o P, i is possible o obse e
ha when he cylinde is se a 140 ºC, c osslinking begins
o ake place wi hin he ma e ial be o e en e ing he mold
and he p ocessabili y dec eases, making i mo e di icul
o uni o mly ill he mold ca i y ega dless o he applied P.
The e o e, no signi ican ad an ages a e obse ed be ween
he sys ems p ocessed a 500 ba (E2I3 and E2I7) and hose
p ocessed a 800 ba (E2I4 and E2I8). On he o he hand,
when Tc = 110 ºC, a bene icial e ec o P can be obse ed
bu only o high mold empe a u es, i.e., 180 ºC. Wi h good
p ocessabili y, he aw ma e ial will low easily om he cyl-
inde o he mold, whe e P will be a de e mining ac o when
applying a linea model (lm), which also accoun ed o he
in e ac ions o injec ion molding pa ame e s.
The second s ep o he analysis en ailed he implemen-
a ion o he esponse su ace echnique h ough he so -
wa e Ma lab® e sion 2020a o iden i y he manu ac u ing
pa ame e s ha maximize he mechanical p ope ies o he
bioplas ic. Conside ing ha he ull ac o ial design was se
only on wo le els, i.e., an uppe and a lowe one, a linea
app oxima ion unc ion was used o desc ibe he esponse
su ace. Based upon he esul s ob ained om in e en ial
s a is ics also, some o he in e ac ions o he injec ion
molding pa ame e s we e conside ed in he app oxima ion
unc ions leading o he Eq. (1):
Y(T
c
,T
m
,P)=a+b×T
c
+c×T
m
+d×P+e×T
c
×P+ ×Tm×P+g×Tc×Tm×P
(1)
whe e Y is he mechanical p ope y unde conside a ion, Tc
he cylinde empe a u e, Tm he molding empe a u e and P
he injec ion p essu e.
Resul s and Discussion
Tensile Tes s and S a is ical Analysis
Tensile p ope ies o he di e en s udied sys ems a e ga h-
e ed in Table 2. A i s , he e ec o ex usion s ep numbe
was in es iga ed (E1 and E2 sys ems o one pass o wo
passes h ough he ex ude , espec i ely) and i was ound
ha he longe esidence ime gi en by he second ex usion
esul ed in imp o ed Young’s modulus and ensile s eng h
wi hou any de imen al e ec upon elonga ion a b eak. In
his way, unde he same injec ion molding condi ions, he
samples submi ed o wo ex usion s eps e ealed a e age
alues o E and σmax o 70 MPa and 1.1 MPa compa ed o
he 57 MPa and 0.8 MPa exhibi ed by he sys em submi ed
o only a single ex usion s ep, wi h an almos cons an elon-
ga ion a b eak (4.0% o E2 and 3.9% o E1). The e o e,
Table 2 Mechanical p ope ies (Young’s modulus (E), ensile s eng h
(σmax) and s ain a b eak (εmax)) o he di e en biopolyme s
Sys em E (MPa) σmax (MPa) εmax (%)
E1 57 ± 4 0.8 ± 0.1 3.9 ± 0.6
E2 70 ± 4 1.1 ± 0.1 4.0 ± 0.2
E2I1 70 ± 4 1.6 ± 0.1 6.9 ± 0.6
E2I2 65 ± 2 1.5 ± 0.1 6.0 ± 0.3
E2I3 42 ± 6 1.8 ± 0.3 7.0 ± 2.0
E2I4 30 ± 7 1.6 ± 0.1 7.2 ± 0.9
E2I5 56 ± 5 1.2 ± 0.1 6.8 ± 0.8
E2I6 138 ± 18 2.5 ± 0.2 5.7 ± 0.6
E2I7 95 ± 8 1.9 ± 0.1 6.1 ± 0.3
E2I8 67 ± 1 1.9 ± 0.1 6.6 ± 0.5
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Jou nal o Polyme s and he En i onmen (2025) 33:512–527
op imiza ion o he injec ion molding p ocess depends on
a complex balancing o phenomena and mechanisms. Fo
example, bioplas ic low is helped by empe a u es highe
han glass ansi ion, bu i is also hinde ed by excessi ely
high empe a u es, p omo ing c osslinking and os e ing
plas icize emo al be o e injec ion. O he wise, oid con-
en mus be minimized and educed by be e mold illing
bu hinde ed by plas icize e apo a ion, i.e., phenomena ha
mus be balanced as a unc ion o he applied empe a u es.
In e es ingly, nei he he p ocessing pa ame e s selec ed
no hei in e ac ions ha e any e ec on he elonga ion a
b eak. This can be likely asc ibed o he ashes inside he
eeds ock whose chemical composi ion and mo phology
a e no a ec ed by any o he injec ion molding pa ame e s
and ac ing as s ess in ensi ie s always de e mine a b i le
esponse o he bioplas ic.
Based on he esul s ob ained, he su ace esponse analy-
sis was used o op imize he manu ac u ing pa ame e s o
maximize bo h ensile modulus and s eng h by applying a
linea unc ion ha accoun ed o he e na y in e ac ion o
he h ee pa ame e s and he bina y in e ac ion o P wi h
he mold is se a 180 ºC (E2I5 and E2I6). A hese em-
pe a u es, plas icize s e apo a e apidly, bu aided by high
P, he ma e ial con inues o low and dis ibu e h oughou
he ca i y, elimina ing possible de ec s in he inal piece and
leading o highe E and σmax. Al hough his phenomenon
can occu a 150 ºC (E2I1 and E2I2), his lowe empe a-
u e leads o a lowe numbe o biopolyme ic in e ac ions
and less plas icize e apo a ion. Thus, ega dless o he P,
he e will be a lowe deg ee o compac ion du ing injec ion.
Addi ionally, in bo h cases, he εmax dec eases as a conse-
quence o he plas icize losses.
The e ec o Tm, as happened wi h Tc and P, will be
explained in e ms o he o he wo pa ame e s ha will
ha e a di ec in luence. Thus, inc easing he mold empe a-
u e om 150 °C o 180 °C a a lowe P (500 ba ) does
no show a clea bene i in he mechanical p ope ies o
bioplas ics due o he highe plas icize losses. Fo Tc =
110 °C, he e a e no imp o emen s in E o εmax, while σmax
dec eases (E2I1 and E2I5). Fo Tc = 140 °C, al hough he e
is a ce ain imp o emen in E, σmax emains unchanged,
and εmax dec eases (E2I3 and E2I7). On he o he hand, he
use o highe P (800 ba ) p o ides a much clea e end.
An imp o emen in he s i ness and load-bea ing capaci y
o he specimens (E and σmax) is obse ed, accompanied by
a loss o duc ili y (εmax). This ep esen s a be e comp o-
mise o p ope ies, especially well-balanced when using Tc
= 110 °C (E2I2 and E2I6), esul ing in a sys em wi h he
bes alues o E and σmax, wi h a sligh ly lowe εmax s ill
close o hose o he o he sys ems. This is achie ed h ough
a combina ion o an app op ia e empe a u e in he cylinde ,
su icien ly high o p ope low bu no oo high o ini ia e
c osslinking, as well as a high Tm and P o allow p ope
mold illing wi h good compac ion and empe a u e-induced
he mo o ming [30].
All hese conclusions we e u he co obo a ed by in e -
en ial s a is ics, whose esul s a e summa ized in Tables 3, 4
and 5. Bo h Tm and P display s ong s a is ical signi icance
on bo h ensile s i ness and s eng h, as well as hei in e -
ac ion. This is cohe en wi h he di e en deg ees o hea -
induced p o ein and s a ch c osslinking achie ed by he
bioplas ics depending on he mold empe a u e and on i s
abili y o ill he mold as a unc ion o he applied P. On he
con a y, Tc p o ed o be de e minan only o ensile modu-
lus, while i s in e ac ion wi h P is undamen al o bo h s i -
ness and s eng h. Indeed, he capabili y o he bioplas ic o
low in o he mold does no depend only on he applied P,
bu also on i s iscosi y, which is s ic ly co ela ed o he
cylinde empe a u e, hus explaining he s ong impo ance
o he in e ac ion o hese wo pa ame e s.
Finally, he e na y in e ac ion be ween he h ee p o-
cessing pa ame e s displays a high s a is ical signi icance
o bo h ensile s i ness and s eng h, hus p o ing ha he
Table 3 S a is ical signi icance o he e ec s o he injec ion molding
pa ame e s and hei in e ac ions on bioplas ic Young’s modulus
Pa ame e F alue P (> F)
Tc12.12 0.003
Tm65.36 4.83·10−07
P 5.51 0.032
Tc × Tm1.31 0.268
Tc × P 39.71 1.05·10−05
Tm× P 16.58 8.87·10−04
Tc × Tm× P 15.24 0.001
Table 4 S a is ical signi icance o he e ec s o he injec ion molding
pa ame e s and hei in e ac ions on bioplas ic ensile s eng h
Pa ame e F alue P (> F)
Tc1.90 0.186
Tm13.10 0.002
P 14.86 0.001
Tc × Tm0.36 0.557
Tc × P 28.78 6.32·10−05
Tm× P 38.41 1.28·10−05
Tc × Tm× P 17.79 6.52·10−04
Table 5 S a is ical signi icance o he e ec s o he injec ion molding
pa ame e s and hei in e ac ions on bioplas ic elonga ion a b eak
Pa ame e F alue P (> F)
Tc2.33 0.15
Tm2.79 0.11
P 1.69 0.21
Tc × Tm1.42 0.25
Tc × P 1.46 0.24
Tm× P 0.33 0.57
Tc × Tm× P 0.45 0.50
1 3
517
Jou nal o Polyme s and he En i onmen (2025) 33:512–527
imp o ing ma e ial lowabili y; a he same ime, he highe
he cylinde empe a u e, he highe he p og essi e c oss-
linking o he bioplas ics, which ac s in he opposi e di ec-
ion in e ms o iscosi y. In ligh o his, a highe injec ion P
ensu es a be e lowabili y o he ma e ial al eady a lowe
Tc, hus allowing he p e en ion o bioplas ic c osslinking in
he cylinde , while a lowe P, he highe iscosi y de i ing
om he highe p oximi y o he glass ansi ion empe a-
u e makes he highe Tc a p e e ed choice. In his way, he
highes P and he lowes cylinde empe a u e a e he bes
choices among he wo a o emen ioned con igu a ions.
Dynamic Mechanical The mal Analysis (DMA)
Figu e 3 depic s he equency sweep es s conduc ed on
he E1 and E2 sys ems ( esul ing om changing he num-
be o passes h ough he ex ude ). I is wo h men ioning
ha he es o he sys ems displayed simila alues o he
bo h Tm and Tc. The esul s ob ained a e shown in Figs. 1
and 2 o ensile modulus and s eng h, espec i ely. The
main ou come is ha a P o 800 ba , a cylinde empe a u e
o 110 °C and a mold empe a u e o 180 °C allow o he
maximum ensile s i ness and s eng h, bu some u he
conclusions can be d awn.
To begin wi h, he bes mechanical pe o mance is
achie ed nea ly always o he highes alue o mold em-
pe a u e, i.e., 180 °C, ega dless o P and Tc and his can
be likely asc ibed o he highe c osslinking deg ee induced
in he bioplas ic [31]. Ano he impo an ou come is ela ed
o he in e ac ion o wo pa ame e s, namely, he injec ion
P and he cylinde empe a u e. When wo king wi h highe
P, he bes esul s a e achie ed wi h he lowes cylinde
empe a u e, while a highe Tc is necessa y when wo king
wi h lowe P. This can likely be asc ibed o wo compe ing
phenomena. The highe he cylinde empe a u e, he a -
he he bioplas ic om i s glass ansi ion empe a u e, hus
Fig. 1 Su aces esponse o ensile modulus
1 3
518
Jou nal o Polyme s and he En i onmen (2025) 33:512–527
The iscoelas ic moduli as a unc ion o empe a u e o
he sys ems ob ained o di e en injec ion molding condi-
ions a e p esen ed in Fig. 4A. In his igu e, only he sys-
ems whe e he injec ion condi ions (Tc, Tm and P) we e
modi ied a e ep esen ed, as he iscoelas ic moduli o he
E1 and E2 sys ems ollowed he same end as he es o
he sys ems. Thus, hei beha io wi h empe a u e is ep e-
sen ed by hese sys ems, while he change induced by using
wo ex usion s eps ins ead o one is ha discussed in Fig. 3,
wi h he E2 sys em exhibi ing sligh ly highe E′ and E″ han
he E1 sys em.
Once again, i is possible o obse e ha E′ is abo e E″
o all he s udied samples, ega dless o he empe a u e,
implying ha he bioplas ics ha e a p edominan ly elas ic
cha ac e (Fig. 4A). In his s udy, all sys ems exhibi simi-
la beha io , wi h hei moduli emaining closely aligned
and e en o e laid h oughou he en i e empe a u e ange,
equency ange s udied, indica ing no disce nible di e -
ences in iscoelas ic moduli (E′ and E″) o he di e en
injec ion condi ions e alua ed. The e o e, E1 and E2 sys-
ems a e chosen as ep esen a i es o elucida e he e ec o
a second ex usion s ep on he bioplas ics de eloped.
Fi s ly, all sys ems exhibi a p edominan elas ic cha -
ac e , wi h highe s o age (E′) han loss modulus (E″), a
ypical beha io o polyme ic ma e ials [32]. Fu he mo e,
bo h iscoelas ic moduli inc ease wi h inc easing equency,
showing a ce ain dependency on his pa ame e . Al hough
he ensile p ope ies o he bioplas ics we e no ably al e ed
by he second ex usion s ep, he e is only a small enhance-
men o he heological p ope ies. This is e iden om he
sligh ly highe iscoelas ic moduli o he E2 sys em com-
pa ed o he E1 one. Such enhancemen could be a ibu ed
o he longe esidence ime in he ex ude du ing he sec-
ond s ep, acili a ing s a ch gela iniza ion and p omo ing
inc eased p o ein chain in e ac ions [28, 29].
Fig. 2 Su aces esponse o ensile s eng h
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519
Jou nal o Polyme s and he En i onmen (2025) 33:512–527
he mose ing po en ial (i.e., he e is no eco e y o he is-
coelas ic alues a ele a ed empe a u es), indica ing, on he
one hand, ha i is no possible o achie e u he enhance-
men in heological p ope ies wi h highe injec ion mold-
ing empe a u es and, on he o he hand, ha he bioplas ics
de eloped beha e as he mose s [34]. The abili y o hese
ma e ials o main ain hei iscoelas ic moduli a ele a ed
empe a u es, coupled wi h hei high E′ and E″ alues, sug-
ges s po en ial sui abili y o subs i u ing con en ional poly-
me s in speci ic applica ions [35].
suppo ing he s a emen ha signi ican di e ences among
samples canno be iden i ied.
In e ms o he e olu ion o he iscoelas ic moduli wi h
empe a u e, i is no iceable ha he iscoelas ic moduli
dec ease in all cases as he empe a u e ises om − 10 ºC
o app oxima ely 100–120 ºC due o inc eased polyme
chain mobili y p omo ed by ce ain s uc u al elaxa ion
[33]. Subsequen ly, o u he empe a u e inc ease, he
iscoelas ic moduli emain s able up o 160 ºC, eaching a
pla eau. In his sense, none o he sys ems exhibi ed u he
Fig. 4 (A) Viscoelas ic moduli and (B) loss angen a ia ions du ing he empe a u e amp es s be ween − 10 and 160 ºC a 1 Hz o he E2I1, E2I2,
E2I3, E2I4, E2I5, E2I6, E2I7 and E2I8 sys ems
Fig. 3 F equency sweep es s pe -
o med be ween 0.5 and 20 Hz a
oom empe a u e o he E1 and
E2 sys ems
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