Ci a ion: Missio, A.L.; Delucis, R.A.;
O oni, C.G.; de Cadema o i, P.H.G.;
Coldebella, R.; A ambu u, A.B.;
Ma os, B.D.; Rod igues, M.B.B.;
Lunkes, N.; Ga o, D.A.; e al.
The mally Resis an ,
Sel -Ex inguishing The moplas ic
Composi es Enabled by
Tannin-Based Ca bonaceous
Pa icula e. Polyme s 2022,14, 3743.
h ps://doi.o g/10.3390/
polym14183743
Academic Edi o s: Luigi So en ino
and Ma kus Gahlei ne
Recei ed: 6 May 2022
Accep ed: 2 Sep embe 2022
Published: 7 Sep embe 2022
Publishe ’s No e: MDPI s ays neu al
wi h ega d o ju isdic ional claims in
published maps and ins i u ional a il-
ia ions.
Copy igh : © 2022 by he au ho s.
Licensee MDPI, Basel, Swi ze land.
This a icle is an open access a icle
dis ibu ed unde he e ms and
condi ions o he C ea i e Commons
A ibu ion (CC BY) license (h ps://
c ea i ecommons.o g/licenses/by/
4.0/).
polyme s
A icle
The mally Resis an , Sel -Ex inguishing The moplas ic
Composi es Enabled by Tannin-Based Ca bonaceous Pa icula e
And éL. Missio 1,2,*,† , Ra ael A. Delucis 1,2,†, Caio Gomide O oni 3, Ped o H. G. de Cadema o i 4,
Rod igo Coldebella 5, A hu B. A ambu u 1, B uno D. Ma os 6,†, Ma lon B. B. Rod igues 7,
Naya a Lunkes 1,8, Da ci A. Ga o 1,2 and Jalel Labidi 9,*
1G adua e P og am in Ma e ials Science and Enginee ing (PPGCEM), Technology De elopmen Cen e ,
Fede al Uni e si y o Pelo as (UFPel), Pelo as 96010-610, RS, B azil
2G adua e P og am in En i onmen al Sciences (PPGCAmb), Enginee ing Cen e , Fede al Uni e si y o
Pelo as (UFPel), Pelo as 96010-610, RS, B azil
3Depa men o Ma e ials Enginee ing (DEMa), Fede al Uni e si y o São Ca los (UFSCa ),
São Ca los 13565-905, SP, B azil
4G adua e P og am in Fo es y Enginee ing (PPGEF), Fede al Uni e si y o Pa aná,
Cu i iba 80210-170, PR, B azil
5Fo es P oduc s Labo a o y (PPGEF), Cen e o Ru al Sciences, Fede al Uni e si y o San a Ma ia (UFSM),
San a Ma ia 97105-900, RS, B azil
6Depa men o Biop oduc s and Biosys ems, School o Chemical Enginee ing, Aal o Uni e si y,
FI-00076 Espoo, Finland
7Ma e ials Enginee ing Cou se, Technological De elopmen Cen e , Fede al Uni e si y o Pelo as (UFPel),
Pelo as 96010-610, RS, B azil
8A chi ec u e and U banism Unde g adua e Cou se, Ca holic Uni e si y o Pelo as (UCPel),
Pelo as 96015-560, RS, B azil
9
Chemical and En i onmen al Enginee ing Depa men , Uni e si y o he Basque Coun y, Escuela Poli écnica
de San Sebas ián, Plaza Eu opa, 1, 20018 Donos ia-San Sebas ián, Guipuzcoa, Spain
*Co espondence: [email p o ec ed] (A.L.M.); [email p o ec ed] (J.L.)
† These au ho s con ibu ed equally o his wo k.
Abs ac :
Flame- esis an ma e ials a e key componen s in buildings and se e al o he enginee -
ing applica ions. In his s udy, lame e a dancy and he mal s abili y we e con e ed o a highly
lammable echnical he moplas ic—polyp opylene (PP)—upon composi ing wi h a ca bonaceous
annin-based pa icula e (CTP). He ein, we epo on a s aigh o wa d, acile, and g een app oach
o p epa e sel -ex inguishing he moplas ic composi es by he moblending highly ecalci an pa -
icula e. The he mal s abili y and mechanical p ope ies o he composi es a e e he ed o he CTP
con en . We demons a e ha he addi ion o up o 65 w % o CTP imp o ed he iscoelas ic p ope -
ies and hyd ophobici y o he PP, whe eas ha ing ma ginal e ec s on bulk wa e in e ac ions. Mos
impo an ly, composi ing wi h CTP ema kably imp o ed he he mal s abili y o he composi es,
especially o e 300 ◦C, which is an impo an h eshold associa ed wi h he combus ion o ola iles.
PP-CTP composi es demons a ed g ea capaci y o limi and s op i e p opaga ion. The e o e, we
o e an inno a i e ou e owa ds he mally esis an and sel -ex inguishing PP composi es, which is
enabled by sus ainable annin-based lame e a dan s capable o u he b oadening he echnical
ange o commodi y polyole ins o high empe a u e scena ios.
Keywo ds:
bioeconomy; annin oams; enginee ing componen s; building ma e ials; lame- esis an
ma e ials; polyp opylene
1. In oduc ion
Plas ics play a c ucial ole in many b anches o enginee ing, spanning om cons uc-
ion o ex iles. Polyole ins, including polyp opylene (PP), a e commodi y plas ics ha
ind a ple ho a o gene al pu pose uses owing o hei easy p ocessing and ecyclabili y,
Polyme s 2022,14, 3743. h ps://doi.o g/10.3390/polym14183743 h ps://www.mdpi.com/jou nal/polyme s
Polyme s 2022,14, 3743 2 o 13
high chemical esis ance, and low cos [
1
,
2
]; howe e , hei hyd oca bon na u e and el-
a i ely low mel ing poin (ca. 130–170
◦
C o PP, depending mainly on ac ici y) make
hem unsui able o applica ions in ol ing mode a e o high empe a u es, such as in he
au omo i e, ae ospace, and building segmen s [
3
–
5
]. Addi ionally, he ole inic s uc u e
o PP dissol es in o highly ola ile a oma ic hyd oca bons (e.g., oluene and benzene)
unde he mal s esses (sligh ly abo e 100
◦
C) and can easily igni e by ei he hea o lame,
eleasing poisonous gases upon bu ning. The e o e, se e al a emp s o ende ing PP o i s
composi es (e.g., ibe - ein o ced PP) lame e a dan o e en sel -ex inguishing ha e been
made o e he las yea s [6–12].
Flame e a dancy in PP and o he lammable ma e ials is o en achie ed wi h he
in oduc ion o addi i es, which can ei he ac as ecalci an componen s ha bu n a a
slow a e and a e less likely o igni e o by quenching chain eac ions du ing combus ion. In
he pas , ew subs ances based on chlo ine and b omine we e used o imp o e bo h he mal
and combus ion esis ance in PP [
5
,
13
]. Mo e ecen ly, ew halogen- ee lame- e a dan
sys ems, which a e di ided in o addi i es o eac i e subs ances [
5
], ha e been p o en
o be highly e icien . The la e includes compounds based on me al hyd oxides, me al
bo a es, and in umescen lame e a dan s [
4
,
13
–
15
]. As no ed, he compounds used so
a a e hea ily dependen on highly ene gy demanding mining o syn hesis. Al hough
syn he ic lame e a dan s p o ide high he mal and/o combus ion esis ance, hei non-
enewable na u e in pa allel o hei o en poo in e ace wi h mos polyme ma ices [
16
]
has incen i ized he sea ch o bio-based componen s ha can ul il lame e a dancy and
o he equi emen s while adding sus ainabili y o such ma e ials.
Na u al polyphenolics, such as lignins and annins, ha e been demons a ed o im-
p o e he he mal s abili y o PP composi es [
17
]. Thei ecalci an , a oma ic na u e and
hei abili y o cha unde he mal s ess ha e been key o hei u iliza ion as he mally
s able ille s [
18
]. Flame e a dancy, howe e , has no been achie ed using only na u al
polyphenolics. Fo such endea o s, na u al polyphenolics ha e been modi ied wi h mo e
adi ional, ino ganic compounds ia sup amolecula [
19
] o co alen [
20
] in e ac ions
o be la e inco po a ed in o PP ma ices. In his con ex , we he ein demons a e he use
o ca bonaceous pa icula e composed o annin- u u yl alcohol copolyme s (CTP) o
p oduce and he mally esis an , sel -ex inguishing PP composi es. The combina ion o
annins, especially hei condensed s uc u es, wi h u u yl alcohol, ano he bio-based
compound, has been widely in es iga ed ecen ly o he o ma ion o insula ing and
lame- e a dan oams by hei c oss-linking eac ion wi h aldehydes [
21
,
22
]. Such oams,
howe e , a e highly b i le, hus limi ing applica ions whe e lexibili y and/o duc ili y a e
equi ed [
23
–
26
]. The e o e, we composi ed a CTP made up o annin and u u yl alcohol
as a bio-based lame e a dan wi h PP as ma ix o each balanced i e sa e y as well as
he mal and mechanical p ope ies, hus ully ha nessing he ad an ages o each indi idual
componen while making mo e sus ainable lame- e a dan ma e ials.
2. Ma e ials and Me hods
2.1. Raw Ma e ials
Condensed annins we e ex ac ed om black wa le ba k (Acacia mea nsii) and sup-
plied by TANAC
®
(Mon eneg o, B azil). Acco ding o he supplie , his annin ex ac is
composed o condensed annins (70–80 w %), hyd ocolloid gums (20–30 w %), as well
as mino amoun s o suga s and small molecules. I s pa icle size mean was de e mined
by scanning elec on mic oscopy (SEM) o be 0.66
µ
m. Nea PP (H103) was supplied by
B askem (T iun o, B azil). Acco ding o he supplie , his polyme ma ix has he ollowing
cha ac e is ics: 40 g
·
min
−1
mel low a e a 230
◦
C/2.16 kg (ASTM D1238), 0.905 g
·
cm
−3
densi y (ASTM D792), 1200 MPa bending modulus (ASTM D790), 34 MPa ensile s eng h
(ASTM D638), 101 Rockwell ha dness (ASTM D785), 20 J/m No ched Izod s eng h (ASTM
D256), and 156
◦
C Vica so ening poin (ASTM D1525). The ollowing chemicals we e
acqui ed om Sigma Ald ich, Gua ulhos, B azil, and used wi hou p e ious pu i ica ion:
Polyme s 2022,14, 3743 3 o 13
u u yl alcohol (CAS numbe 98-00-0), o maldehyde (CAS numbe 50-00-0), die hyl e he
(CAS numbe 60-29-7), and oluene-4-sul onic acid (CAS numbe 6192-52-5).
The CTP de i ed om igid annin oams was p oduced acco dingly wi h Tondi
and Pizzi [
23
]. A. mea nsii annin ex ac , dis illed wa e , u u yl alcohol (97 w %), and
o maldehyde (32 w %) we e mixed unde mechanical s i ing o 2 min and added by
die hyl e he (99.5 w %) and oluene-4-sul onic acid (65 w %), ollowed by mechanical
s i ing o 30 s be o e he homogeneous mix u e was hen pou ed in o an open con aine
o he oam o ise. The oams we e allowed o es a oom empe a u e (abou 20
◦
C) o
a leas 24 h o e apo a e un eac ed ola iles and hen kni e-milled in o CTP.
2.2. P epa a ion o he PP-CTP Composi es
PP and CTP we e mixed a ou PP con en s anging om 35 o 65 w % on a high-speed
he mo-kine ic mixe (model MH-100, Gua ulhos, B azil) se a 120
◦
C ( he empe a u e
was u he isen by iscous dissipa ion upon shea ing) and hen comp ession molded on
an elec ically hea ed hyd aulic p ess (Ma coni, model MA 098/AR15, Pi acicaba, B azil) a
900 MPa and 175
◦
C o 10 min. The molded pa s (140
×
140
×
3.5 mm
3
) we e p oduced
in iplica es and equilib a ed a 20
◦
C and 65% ela i e humidi y in an en i onmen al
chambe un il eaching cons an mass.
2.3. Fou ie -T ans o med In a ed (FTIR) Spec oscopy
The chemical ea u es o he samples we e in es iga ed by FTIR. KB pelle s we e
p epa ed wi h milled samples and hen analyzed in di ec ansmi ance mode on an
in a ed spec ome e (Shimadzu P es ige-21, Kyo o, Japan). A o al o 45 scans we e
eco ded a a esolu ion o 2 cm
−1
in he 400–4500 cm
−1
wa enumbe ange. The spec a
we e no malized (0, 1) o enable in ensi y compa isons.
2.4. Densi y and Bulk Wa e In e ac ions
Appa en densi y (ASTM D792), wa e abso p ion, and hickness swelling a 2 and
24 h
(ASTM D570) we e de e mined o all composi es ollowing hei espec i e s anda dized
p ocedu es. Wa e leaching was de e mined in iplica e: 1 g o a milled sample (60 mesh)
was imme sed in dis illed wa e o 24 h and hen o en d ied a 60
◦
C un il eaching
cons an mass. Quan i a i e da a we e s a is ically analyzed using analysis o a iance
p io o Tukey es s, as sui able, bo h a a signi icance le el o 5%.
2.5. Scanning Elec on Mic oscopy
The bu n sec ion o he PP-CTP composi e was gold-spu e ed and imaged on a
scanning elec on mic oscope (Phenom P oX Desk op SEM, Gua ulhos, B azil) using a
5 kV ol age.
2.6. Su ace We abili y
Wa e con ac angle was measu ed h ough he sessile d op me hod on a goniome e
(K uss, model DSA25B, Hambu g, Ge many). Dis illed wa e d ops (11
µ
L in olume) we e
cas on he su ace o i e samples (20
×
20 mm
2
) pe ea men and he con ac angle was
measu ed e e y 10 s o 60 s.
2.7. The mog a ime y
The mass loss p o ile o e empe a u e was e idenced by he mog a ime ic (TG)
and de i a i e TG (DTG) cu es eco ded om 30 o 600
◦
C a a cons an hea ing a e o
15 ◦C·min−1, wi hin an a gon low a e o 50 mL·min−1.
2.8. Di e en ial Scanning Calo ime y (DSC)
Di e en ial scanning calo ime y (DSC) was pe o med using a TA Q20 calo ime e
(New Cas le, DE, USA) in he 100–200
◦
C ange in o de o e alua e empe a u es o c ys-
alliza ion (Tc) and mel ing (Tm) o CTP-PP composi es. The samples we e hea ed, cooled
Polyme s 2022,14, 3743 4 o 13
down, and hen hea ed again, always a a a e o 10
◦
C
·
min
−1
in he amp mode. C ys-
allini y (%) was calcula ed based on he a ea unde cu e, acco ding o Ma os e al. [27].
2.9. Dynamic Mechanical Analysis and Tensile Tes s
Mechanical beha io o he PP-CTP composi es was s udied on a dynamic mechanical
analyze (TA ins umen s, model Q-800, New Cas le, DE, USA). P isma ic (
35 ×17 ×37 mm3
)
specimens we e e alua ed using a dual can ile e se up a a equency o 1 Hz and
a s a ic load o 5 N. Samples we e hea ed om 30 o 120
◦
C a 5
◦
C
·
min
−1
. Tensile
p ope ies o he PP-CTP composi es we e e alua ed h ough mechanical es s using an
EMIC
DL23-300 uni e sal
machine (São Josédos Pinhais, B azil). The samples and es
pa ame e s we e adjus ed as indica ed by ASTM D638. The samples had dimensions o
85
×
15
×
3 mm
3
(leng h, wid h and hickness) and 5 eplica es we e used pe ea men .
The es speed was 5 mm·min−1.
2.10. Flame Re a dancy
Flammabili y es s we e pe o med o in es iga e he po en ial o CTP o ac as a lame
e a dan in PP-based composi es. P isma ic (15
×
3
×
100 mm
3
) specimens we e exposed
o a e ical lame om a Bunsen bu ne o 10 s, and hen classi ied acco ding o hei
isual aspec in o o ally bu ned (a) and sel -ex inguishing (b). The inal weigh loss was
also measu ed. This es was inspi ed in an app op ia ed s anda d p ocedu e. Pine wood
sawdus - and pine needle- illed PP composi es (50 w % PP), p epa ed ollowing he same
condi ions desc ibed ea lie , we e used as a compa ison. Un illed nea PP specimens we e
also es ed o compa ison pu poses.
2.11. S a is ical Analyses
Da a no mali y was con i med by Shapi o-Wilk es s. A e wa ds, all he da a we e
subjec ed o ANOVA es s ollowed by Fishe es s. The la e es s we e pe o med o
compa e he means. All s a is ical es s we e conduc ed a a 0.05 signi icance le el.
3. Resul s and Discussion
3.1. Chemical Fea u es o he Composi es
The FTIR spec a (Figu e 1) o he composi es display he ypical spec oscopic signa-
u es o hei componen s. Nea PP has a p ominen band a he 2850–2950 cm
−1
ange,
which ep esen s CH, CH
2
, and CH
3
g oups [
27
]. The b oad peak a 3440 cm
−1
is asc ibed
o he s e ching ib a ion o he O–H g oups associa ed wi h abso bed mois u e [
28
], which
is mo e in ense o he CTP when compa ed o ei he nea PP o i s composi es. The e
is a posi i e co ela ion be ween he band cen e ed a 3440 cm
−1
and he CTP con en
in he composi es, hus in e ing a g adual dec ease in hyd ophilici y associa ed wi h a
p og essi e inc ease in PP ac ion in he composi e, which is expec ed because o he
hyd oca bon, nonpola na u e o PP.
The IR spec um o CTP had peaks a 1006, 1509, and 1630 cm
−1
. The peak a
1006 cm−1
is a ibu ed o C–O ib a ions o (i) –C–O–C– e he b idges in complex oxygen-
con aining cyclic molecules and/o (ii) =C–O–C= b ea hing in u an moie ies [
28
]. Tha
band a 1509 cm
−1
can be associa ed wi h in-plane C–H bending ib a ions in a oma ic
molecules om he e oa oma ic compounds [
28
]. This band can also be ela ed o C=C
s e ching ib a ions in u an ings belong o he u u yl alcohol [
29
,
30
]. The band a
1630 cm−1
is ypically a ibu ed o C=C s e ching in benzene ing. As no ed, he e we e
no new clea IR peaks in he composi e spec a ha would indica e he o ma ion o new
chemical iden i ies. The e o e, he PP-CTP in e acial in e ac ions a e d i en p ima ily by
physical means, i.e., Van de Waals con ac o ces including London dispe sion. Hyd opho-
bic in e ac ions and hyd ogen bonding may also be a play.
Polyme s 2022,14, 3743 5 o 13
Polyme s 2022, 14, x FOR PEER REVIEW 5 o 13
in he composi es, hus in e ing a g adual dec ease in hyd ophilici y associa ed wi h a
p og essi e inc ease in PP ac ion in he composi e, which is expec ed because o he hy-
d oca bon, nonpola na u e o PP.
Figu e 1. In a ed spec a o he PP−CTP composi es and hei single phases anging om (a) 4000
o 2400 cm
−1
and om (b) 1800 o 800 cm
−1
.
The IR spec um o CTP had peaks a 1006, 1509, and 1630 cm
−1
. The peak a 1006 cm
−1
is a ibu ed o C–O ib a ions o (i) –C–O–C– e he b idges in complex oxygen-con aining
cyclic molecules and/o (ii) =C–O–C= b ea hing in u an moie ies [28]. Tha band a 1509
cm
−1
can be associa ed wi h in-plane C–H bending ib a ions in a oma ic molecules om
he e oa oma ic compounds [28]. This band can also be ela ed o C=C s e ching ib a-
ions in u an ings belong o he u u yl alcohol [29,30]. The band a 1630 cm
−1
is ypically
a ibu ed o C=C s e ching in benzene ing. As no ed, he e we e no new clea IR peaks
in he composi e spec a ha would indica e he o ma ion o new chemical iden i ies.
The e o e, he PP-CTP in e acial in e ac ions a e d i en p ima ily by physical means, i.e.,
Van de Waals con ac o ces including London dispe sion. Hyd ophobic in e ac ions and
hyd ogen bonding may also be a play.
3.2. Densi y and Wa e In e ac ions
The addi ion o he CTP in o he PP ma ix inc eased he appa en densi y o he
composi es in a quasi-linea ashion (Figu e 2). By g a ime y, we ha e es ima ed he den-
si y o he CTP o be ca. 1.5 g·cm
−3
, which is much highe han he alues ob ained o
classic annin- igid oams— anging om 0.05 o 0.18 g·cm
−3
[24,31]. The densi y o he
composi es did no ollow he ule o mix u es as a esul o he o ma ion o mic o oids
du ing he composi e p ocessing. These mic o oids can be asc ibed o he weak in e acial
adhesion al eady expec ed o he s udied phases. Simila inc eases in densi y we e e-
po ed o PP-based composi es illed wi h o he bio-based ma e ials, such as wood pa -
icles [17] and s a ch [32]. An inc ease in he densi y is majo ly a ibu ed o he densi y o
he ille , e en when chemical ea men s a e applied o he ille o small amoun s o
addi i es a e inco po a ed in o he ma ix [32].
Figu e 1.
In a ed spec a o he PP
−
CTP composi es and hei single phases anging om
(a) 4000 o 2400 cm−1and om (b) 1800 o 800 cm−1.
3.2. Densi y and Wa e In e ac ions
The addi ion o he CTP in o he PP ma ix inc eased he appa en densi y o he
composi es in a quasi-linea ashion (Figu e 2). By g a ime y, we ha e es ima ed he
densi y o he CTP o be ca. 1.5 g
·
cm
−3
, which is much highe han he alues ob ained o
classic annin- igid oams— anging om 0.05 o 0.18 g
·
cm
−3
[
24
,
31
]. The densi y o he
composi es did no ollow he ule o mix u es as a esul o he o ma ion o mic o oids
du ing he composi e p ocessing. These mic o oids can be asc ibed o he weak in e acial
adhesion al eady expec ed o he s udied phases. Simila inc eases in densi y we e
epo ed o PP-based composi es illed wi h o he bio-based ma e ials, such as wood
pa icles [
17
] and s a ch [
32
]. An inc ease in he densi y is majo ly a ibu ed o he densi y
o he ille , e en when chemical ea men s a e applied o he ille o small amoun s o
addi i es a e inco po a ed in o he ma ix [32].
Wa e leaching is usually associa ed wi h wa e esis ance in PP-based composi es [
15
]
and i is c ucial o he implemen a ion o his composi e in se e al applica ions in ol ing
liquid media, a leas po en ially [
14
]. The e is a posi i e ela ionship be ween CTP con en
and wa e leaching (Figu e 2a). The mul iphase (no ully compac ed) cha ac e o he
composi e, as well as he p esence o mic o oids a he componen s in e ace (Figu e 2b),
allow a pa ial wa e low in and ou o he ma e ial in some condi ions (e.g., ull imme sion).
Gi en he he e ogeneous na u e o CTP, solubiliza ion o some en i ies may be inducing
he leaching o ela i ely bigge pa icles. Howe e , e en a such ha sh condi ions, only ca.
10 w %
o he ma e ial is los a e 24 h. This indi ec ly con i ms he physically d i en PP-
CTP in e ac ion, co obo a ing FTIR. Ne e heless, mos o he adi ional lame e a dan s
(bo h addi i es and in umescen lame e a dan s) a e easily leached in wa e i no s ong
in e ac ions wi h he ma ix a e in place, as hese a e based on amines, phospha es, and
sodium sal s, among o he s [5,14].
Polyme s 2022,14, 3743 6 o 13
Polyme s 2022, 14, x FOR PEER REVIEW 6 o 13
Figu e 2. Wa e -composi e ela ionships. (a) Densi y and wa e leaching o he PP-CTP composi es
comp ising CTP a 35 (PP
65
CTP
35
) o 65 w % (PP
35
CTP
65
). (b) Scanning elec on mic oscopy o he
PP
55
CTP
45
composi e, displaying he p esence o mic o oids ac oss i s s uc u e. (c) Wa e abso p-
ion and (d) hickness swelling (TS) a e 2 and 24 h. (e) Wa e con ac angle kine ics o he PP-CTP
composi es. Values ha ing he same le e (a) a e no signi ican ly di e en (Fishe LSD es ).
Wa e leaching is usually associa ed wi h wa e esis ance in PP-based composi es
[15] and i is c ucial o he implemen a ion o his composi e in se e al applica ions in-
ol ing liquid media, a leas po en ially [14]. The e is a posi i e ela ionship be ween
CTP con en and wa e leaching (Figu e 2a). The mul iphase (no ully compac ed) cha -
ac e o he composi e, as well as he p esence o mic o oids a he componen s in e ace
(Figu e 2b), allow a pa ial wa e low in and ou o he ma e ial in some condi ions (e.g.,
ull imme sion). Gi en he he e ogeneous na u e o CTP, solubiliza ion o some en i ies
may be inducing he leaching o ela i ely bigge pa icles. Howe e , e en a such ha sh
condi ions, only ca. 10 w % o he ma e ial is los a e 24 h. This indi ec ly con i ms he
physically d i en PP-CTP in e ac ion, co obo a ing FTIR. Ne e heless, mos o he a-
di ional lame e a dan s (bo h addi i es and in umescen lame e a dan s) a e easily
Figu e 2.
Wa e -composi e ela ionships. (
a
) Densi y and wa e leaching o he PP-CTP composi es
comp ising CTP a 35 (PP
65
CTP
35
) o 65 w % (PP
35
CTP
65
). (
b
) Scanning elec on mic oscopy o he
PP
55
CTP
45
composi e, displaying he p esence o mic o oids ac oss i s s uc u e. (
c
) Wa e abso p ion
and (
d
) hickness swelling (TS) a e 2 and 24 h. (
e
) Wa e con ac angle kine ics o he PP-CTP
composi es. Values ha ing he same le e (a) a e no signi ican ly di e en (Fishe LSD es ).
Nea PP does no abso b wa e . Conside ing he hyd ophilic cha ac e o CTP, one
may expec an inc ease in he wa e abso p ion and hickness swelling o he PP composi es
compa ed o nea PP (Figu e 2c,d). This s onge in e ac ion wi h wa e ag ees wi h mos
o he PP-based composi es, and i is e he ed o he highe pola i y o chemical g oups
belonging o he ille , i.e., g oups able o H-bond wi h wa e such as hyd oxyls [
17
,
32
].
Al hough highe wa e abso p ion is ound in all he composi es when compa ed o nea
PP, i is ema kable ha he alues we e below 5% in all condi ions, especially when
no co alen bonds a e o med be ween he composi e componen s. The o e all inc ease
in wa e abso p ion and hickness swelling, al hough no signi ican , p obably esul ed
om he appea ance o mic o oids a he PP/ ille in e ace (Figu e 2b). Fu he mo e, he
SEM images seem o indica e an o e all good dis ibu ion o he ille pa icles inside he
polyme ma ix.
Polyme s 2022,14, 3743 7 o 13
As a as su ace we ing, he addi ion o CTP esul ed in composi es wi h ema kably
highe wa e con ac angle when compa ed o nea PP (Figu e 2e), eaching a di e ence
o 50
◦
in he bes pe o me s. One can no e ha bulk and su ace wa e ela ionship e-
ma kably di e om each o he in ou ma e ials. Kaymakci and Ay ilmis [
33
] inco po a ed
a iable wood lou con en s ( anging om 30 o 60 w %) in o a PP ma ix and epo ed
ha he inc eases in wood lou con en yielded inc eased su ace we abili ies, which we e
a ibu ed o inc eases in su ace oughness as smoo h su aces may acili a e d op sp ead-
ing while ai pocke s may p e en i . P ocessing empe a u e and iscosi y also s ongly
in luence he inal su ace we abili y o ypical bio-based PP composi es [
34
]. The con ac
angle kine ics also indi ec ly indica es ha he CTP we e homogeneously dis ibu ed inside
he PP-based ma ix as all composi es p esen ed simila su ace ene gies. This subs an ial
inc ease in he su ace hyd ophobici y o PP-CTP composi es can also be assigned o he
nonpola na u e o some o he annin moie ies ha a e associa ed o a oma ic g oups.
Whe eas mo e hyd ophilic subs a es may imp o e bonding s eng h and adhesion, a mo e
hyd ophobic su ace is key o ou doo applica ions as a highe wa e con ac angle usually
indica es be e esis ance agains biologic deg ada ion (e.g., by insec s and ungi) [17].
3.3. The mal, Mechanical and The mo-Mechanical P ope ies o he Composi es
All composi es p esen ed simila he mal decomposi ion p o iles (Figu e 3), which
a e no simple supe imposi ion o he he mog ams o hei single phases, especially un il
400
◦
C. This beha io is di e en om wha was epo ed in mos s udies on bio- illed
PP composi es, which a i med ha he he mal s abili y ollowed closely he ule o
mix u es [
1
,
8
,
17
]. Chemical in e ac ions be ween ille and ma ix do no exis o a e in
oo low in ensi y ha could no be obse ed by FTIR. The e o e, he ema kable di e ence
be ween he he mal beha io o he annin- u an based powde ou side and inside he
PP ma ix can be a ibu ed o he accessible su ace a ea and hea exchange kine ics.
The pa icula e ma e ial exchanges hea wi h he en i onmen in a as e way han hei
bulkie coun e pa s. This has been s udied in he case o glass ansi ion empe a u e o
mic opa icles when compa ed o hei nanoscaled analogues [35,36].
The nea PP was mo e he mally s able han he single CTP up o ~400
◦
C, which is
he ange whe e he nea PP s a s i s he mal decomposi ion. PP comple ely deg ades a e
450
◦
C ollowing a se ies o andom chain scissions and chain ans e eac ions, eleasing
pen ane and hep ane, un il comple e decomposi ion [
4
,
7
,
37
]. On he o he hand, he CTP is
a mul i-b anched igid copolyme composed by a oma ic moie ies om hei annin- u an
ne wo ks ha can ea ange hemsel es in o mo e compac ed ca bonized s uc u es du ing
he mal s esses [24,38,39].
The CTP inco po a ed in he PP ma ix shi ed he maximum decomposi ion peak,
which is asc ibed o PP, o ca. 470
◦
C, as well as inc eased i s esidual con en o abo e
20 w %
. In buildings, whene e he e is any isk o human li e, his can help o ex end he
escape ime du ing a con lag a ion. This beha io occu ed o o he PP-based composi es
and i is asc ibed o he o ma ion o cha du ing he ille decomposi ion [
37
]. A high
esidue yield is also ela ed o high lame esis ance [
37
]. S ill compa ed o he nea PP, he
PP-CTP composi es had simila he mal s abili ies un il 300
◦
C, a which poin hey became
mo e he mally esis an . This is also an impo an inding because his empe a u e le el
is easily exceeded du ing a con lag a ion. The Tm and Tc esul s de e mined wi h basis
on he DSC cu es indica ed ha , in ela ion o he nea PP, small inc eases o 4–5
◦
C we e
ound o all CTP-based composi es. These inc eases we e obse ed as a unc ion o he
CTP con en . The e o e, he CTP pa icles p obably ac ed as nuclea ing agen s o he
c ys alliza ion o PP [
27
]. This impac ed he PP dispe sion and p omo ed a he e ogeneous
nuclea ion [
40
]. The Tm esul s kep s able o all composi es. As obse ed in Table 1,
he
∆
H and Xc dec eased wi h addi ion o he CTP pa icles. This dec ease is ela ed o
he o ma ion o a ansc ys alline egion, in which es ic ions in he la e al di ec ion o
g ow h o sphe uli es a e obse ed, esul ing in a columna laye [
41
]. Simila esul s we e
epo ed in p e ious s udies on pa icula e illed PP composi es [27,40].
Polyme s 2022,14, 3743 8 o 13
Polyme s 2022, 14, x FOR PEER REVIEW 8 o 13
Figu e 3. (a) The mog a ime ic (TG) and (b) de i a i e TG (DTG) cu es, and DSC cu es o (c)
i s and (d) second hea ings o he PP-CTP composi es and hei single phases.
The nea PP was mo e he mally s able han he single CTP up o ~400 °C, which is
he ange whe e he nea PP s a s i s he mal decomposi ion. PP comple ely deg ades
a e 450 °C ollowing a se ies o andom chain scissions and chain ans e eac ions, e-
leasing pen ane and hep ane, un il comple e decomposi ion [4,7,37]. On he o he hand,
he CTP is a mul i-b anched igid copolyme composed by a oma ic moie ies om hei
annin- u an ne wo ks ha can ea ange hemsel es in o mo e compac ed ca bonized
s uc u es du ing he mal s esses [24,38,39].
The CTP inco po a ed in he PP ma ix shi ed he maximum decomposi ion peak,
which is asc ibed o PP, o ca. 470 °C, as well as inc eased i s esidual con en o abo e 20
w %. In buildings, whene e he e is any isk o human li e, his can help o ex end he
escape ime du ing a con lag a ion. This beha io occu ed o o he PP-based composi es
and i is asc ibed o he o ma ion o cha du ing he ille decomposi ion [37]. A high
esidue yield is also ela ed o high lame esis ance [37]. S ill compa ed o he nea PP,
he PP-CTP composi es had simila he mal s abili ies un il 300 °C, a which poin hey
became mo e he mally esis an . This is also an impo an inding because his empe a-
u e le el is easily exceeded du ing a con lag a ion. The Tm and Tc esul s de e mined
wi h basis on he DSC cu es indica ed ha , in ela ion o he nea PP, small inc eases o
4–5 °C we e ound o all CTP-based composi es. These inc eases we e obse ed as a unc-
ion o he CTP con en . The e o e, he CTP pa icles p obably ac ed as nuclea ing agen s
o he c ys alliza ion o PP [27]. This impac ed he PP dispe sion and p omo ed a he e o-
geneous nuclea ion [40]. The Tm esul s kep s able o all composi es. As obse ed in
Table 1, he ΔH and Xc dec eased wi h addi ion o he CTP pa icles. This dec ease is
ela ed o he o ma ion o a ansc ys alline egion, in which es ic ions in he la e al
di ec ion o g ow h o sphe uli es a e obse ed, esul ing in a columna laye [41]. Simila
esul s we e epo ed in p e ious s udies on pa icula e illed PP composi es [27,40].
Figu e 3.
(
a
) The mog a ime ic (TG) and (
b
) de i a i e TG (DTG) cu es, and DSC cu es o
(c) i s and (d) second hea ings o he PP-CTP composi es and hei single phases.
Table 1.
C ys alliza ion (Tc) and mel ing (Tm) empe a u es, hea o usion (
∆
H ) and deg ee o
c ys allini y (Xc) o he CTP-PP composi es.
Tc (◦C) Tm (◦C) ∆H (J/g) Xc (%)
Nea PP 125 168 82.6 43.5
PP65CTP35 130 164 17.8 14.4
PP55CTP45 129 170 16.4 13.8
PP45CTP55 130 165 12.6 14.7
PP35CTP65 130 166 13.6 15.9
An impo an ea u e o ma e ials aiming a ei he i e p o ec ion o he mal s abili y is
hei mechanical beha io as a unc ion o empe a u e. Va ia ions o s o age (E
0
) and loss
(E
00
) moduli we e obse ed in he empe a u e ange o 30–110
◦
C (Figu e 4a). Compa ed
o he nea PP, he composi es p esen ed bo h highe E
0
and E
00
ac oss his empe a u e
ange, which indica es ha he inco po a ion o he CTP led o ema kable gains in s i ness.
Pa icles inco po a ed in so ma ices can c ea e ancho ing mechanisms among he polyme
chains, hus dec easing hei mobili y and consequen ly s i ening he composi e [
17
,
37
].
This is especially ue when using po ous ein o cemen s as, du ing p ocessing, he PP mel
can low in o he pa icula e po es, hus c ea ing a mechanical in e locking ha does no
need o ely upon any chemical in e ac ions [4,34].
Polyme s 2022,14, 3743 9 o 13
Polyme s 2022, 14, x FOR PEER REVIEW 9 o 13
Table 1. C ys alliza ion (Tc) and mel ing (Tm) empe a u es, hea o usion (ΔH ) and deg ee o
c ys allini y (Xc) o he CTP-PP composi es.
Tc (°C) Tm (°C) ΔH (J/g) Xc (%)
Nea PP 125 168 82.6 43.5
PP
65
CTP
35
130 164 17.8 14.4
PP
55
CTP
45
129 170 16.4 13.8
PP
45
CTP
55
130 165 12.6 14.7
PP
35
CTP
65
130 166 13.6 15.9
An impo an ea u e o ma e ials aiming a ei he i e p o ec ion o he mal s abili y
is hei mechanical beha io as a unc ion o empe a u e. Va ia ions o s o age (E′) and
loss (E″) moduli we e obse ed in he empe a u e ange o 30–110 °C (Figu e 4a). Com-
pa ed o he nea PP, he composi es p esen ed bo h highe E′ and E″ ac oss his empe -
a u e ange, which indica es ha he inco po a ion o he CTP led o ema kable gains in
s i ness. Pa icles inco po a ed in so ma ices can c ea e ancho ing mechanisms among
he polyme chains, hus dec easing hei mobili y and consequen ly s i ening he com-
posi e [17,37]. This is especially ue when using po ous ein o cemen s as, du ing p o-
cessing, he PP mel can low in o he pa icula e po es, hus c ea ing a mechanical in e -
locking ha does no need o ely upon any chemical in e ac ions [4,34].
Figu e 4. (a) S o age (E′) and loss (E″) moduli, (b) Tan δ cu es o nea PP and PP-CTP composi es,
(c) modulus o elas ici y (d) and ensile s eng h (MPa) o he PP-CTP composi es. * and ** de e -
mined by Ma os e al. [27] and Sui e al. [40], espec i ely.
Figu e 4.
(
a
) S o age (E
0
) and loss (E
00
) moduli, (
b
) Tan
δ
cu es o nea PP and PP-CTP
composi es,
(c) modulus
o elas ici y (
d
) and ensile s eng h (MPa) o he PP-CTP composi es.
* and ** de e mined by Ma os e al. [27] and Sui e al. [40], espec i ely.
All samples p esen ed simila dec eases in E
0
when hea ed, which means simila
so ening and elaxa ion p ocesses. The simila ly shaped E
00
kine ics indica es ha he CTP
inse ion did no change he iscoelas ic na u e o he nea PP, which p obably did no
a ec molecula ea angemen mechanisms du ing he loading cycles [
37
]. The elaxa ion
ansi ion peak a ca. 70
◦
C o he nea PP appea ed simila o an in lec ion in he Tan
δ
cu e (Figu e 4b), p obably ep esen ing he
α
- ansi ion o PP c ys alline ac ions [
39
].
Bo h ensile s eng h (F = 3.61; p> 0.05) and ensile modulus (F = 3.12; p> 0.05) o he
s udied composi es we e conside ed s a is ically simila a a con idence le el o 0.95%.
Analog ends we obse ed in p e ious s udies [2,17,27].
3.4. Flame Resis ance o he Composi es
The bu ning es s showed ha he nea PP and bo h posi i e con ols (wood-polyme
composi es) unde wen as combus ions and we e ully deg aded, as shown in Figu e 5
and indica ed in Table 2. Kim e al. [
5
] epo ed ha he moplas ic composi es mos ly ge
en i ely bu n ou a e 10 s o lame con ac in e ical bu ning expe imen s. Acco ding o
Ik am e al. [
7
], lammabili y in nea PP is a ibu ed o i s alipha ic hyd oca bon backbone
ha dissol es in o highly ola ile and lammable a oma ic hyd oca bons (e.g., benzene).
