Ci a ion: Ku acina, R.; Szabo á, Z.;
Bu anská, E.; Kosá , L.; Ran uch, P.;
Blino á, L.; Mˇeˇ ínská, D.; Gogola, P.;
Ju ina, F. S udy in o he Fi e and
Explosion Cha ac e is ics o Polyme
Powde s Used in Enginee ing
P oduc ion Technologies. Polyme s
2023,15, 4203. h ps://doi.o g/
10.3390/polym15214203
Academic Edi o : Dan
C is ian Vodna
Recei ed: 26 Sep embe 2023
Re ised: 19 Oc obe 2023
Accep ed: 20 Oc obe 2023
Published: 24 Oc obe 2023
Copy igh : © 2023 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
S udy in o he Fi e and Explosion Cha ac e is ics o Polyme
Powde s Used in Enginee ing P oduc ion Technologies
Richa d Ku acina 1,* , Zuzana Szabo á1,* , E a Bu anská1, LászlóKosá 1, Pe e Ran uch 1, Lenka Blino á1,
Dagma Mˇeˇ ínská2, Pe e Gogola 3and F an išek Ju ina 4
1Ins i u e o In eg al Sa e y in T na a, Facul y o Ma e ials Science and Technology, Slo ak Uni e si y o
Technology in B a isla a, Ul. Jána Bo u 2781/25, SK-917 24 T na a, Slo akia; [email p o ec ed] (E.B.);
[email p o ec ed] (L.K.); pe e [email p o ec ed] (P.R.); [email p o ec ed] (L.B.)
2Depa men o P oduc ion Enginee ing, Facul y o Technology, Tomas Ba a Uni e si y in Zlín,
Va eˇcko a 5669, CZ-760 01 Zlín, Czech Republic; [email p o ec ed]
3
Ins i u e o Ma e ials in T na a, Facul y o Ma e ials Science and Technology, Slo ak Uni e si y o Technology
in B a isla a, Ul. Jána Bo u 2781/25, SK-917 24 T na a, Slo akia; pe e [email p o ec ed]
4Ins i u e o P oduc ion Technologies in T na a, Facul y o Ma e ials Science and Technology,
Slo ak Uni e si y o Technology in B a isla a, Ul. Jána Bo u 2781/25, SK-917 24 T na a, Slo akia;
[email p o ec ed]
*Co espondence: [email p o ec ed] (R.K.); [email p o ec ed] (Z.S.)
Abs ac :
Polyme s and hei p ocessing by enginee ing p oduc ion echnologies (injec ion, molding
o addi i e manu ac u ing) a e inc easingly being used. Polyme s used in enginee ing p oduc ion
echnologies a e cons an ly being de eloped and hei p ope ies a e being imp o ed. G anulome y,
X- ay, FTIR and TGA we e used o cha ac e ize polyme samples. De e mina ion o he i e pa ame e s
o powde samples o polyamide (PA) 12, polyp opylene, and ul a-high molecula weigh (UHMW)
polye hylene is he subjec o he cu en a icle. An explosi e a mosphe e can be c ea ed by he
powde o m o hese polyme ma e ials, and in oduc ion o p e en i e sa egua ds o ensu e sa e y
is equi ed o hei use. Al hough he i e pa ame e s o hese basic ypes o polyme s a e a ailable
in da abases (e.g., GESTIS-Dus Ex), ou esul s showed ha one o he samples used (polyp opylene)
was no lammable and hus is sa e o use in e ms o explosi eness. Two samples we e lammable
and explosi e. The lowe explosi e limi was 30 g
·
m
−3
(PA12) and 60 g
·
m
−3
(UHMW polye hylene).
The maximum explosion p essu e o he samples was 6.47 (UHMW polye hylene) and 6.76 ba (PA12).
The explosion cons an , K
s
, o he samples was 116.6 ba
·
m
·
s
−1
(PA12) and 97.1 ba
·
m
·
s
−1
(UHMW
polye hylene). The e o e, when using polyme s in p oduc ion echnologies, i is necessa y o know
hei i e pa ame e s, and o design e ec i e explosion p e en ion (e.g., en ila ion, explosi e-p oo
ma e ial, e c.) measu es o lammable and explosi e polyme s.
Keywo ds: polyamide; polyp opylene; UHMW polye hylene; dus explosion; haza d
1. In oduc ion
Owing o hei enhanced design lexibili y and cos -e ec i e manu ac u ing solu ions,
u iliza ion o polyme ma e ials in enginee ing p oduc ion echnologies, such as injec ion
molding and addi i e manu ac u ing, has b ough abou signi ican ad ancemen s ac oss
di e se indus ies [1–3].
Howe e , conce ns ha e been aised ega ding he po en ial i e and explosion haza ds
associa ed wi h he inc easing use o polyme powde s in hese p ocesses.
Common lammable dus acciden s a e causing indus ial p ocess manage s o ocus
on lammable powde p ope ies and sa e designs. Unde es ima ing isks du ing sa e y
analyses is o en due o a lack o unde s anding and insu icien analysis o cha ac e is ic
explosion pa ame e s. The absence o expe imen al da a poses a isk o unde es ima ing
p ocess haza d and o e es ima ing sa e y measu es [4–6].
Polyme s 2023,15, 4203. h ps://doi.o g/10.3390/polym15214203 h ps://www.mdpi.com/jou nal/polyme s
Polyme s 2023,15, 4203 2 o 19
The de elopmen and use o modi ied polyme s is inc easingly common in indus y.
Polyme s used in enginee ing p oduc ion echnologies a e composed o he majo i y
o componen s (polye hylene, polyp opylene, polyamides, polys y ene, e c.) which a e
modi ied wi h addi i es. These addi i es can signi ican ly change he mechanical and
physical p ope ies o polyme s (e.g., s eng h, mel ing poin , e c.) as well as hei i e
p ope ies. The polyme can ei he ha e highe i e pa ame e s o become non-explosi e.
An inc ease in i e pa ame e s can be caused by addi ion o dyes o lammable o ganic
ille s, o example. A dec ease in i e pa ame e s can be caused by ino ganic ille s (e.g.,
sal s, oxides, e c.), an ioxidan s (e.g., phenol based a oma ic amines) o i e e a dan s (me al
hyd oxides, halogen and phospho ous-based compounds, e c.). Di e en ypes o addi i es
in polyme s ha e been discussed by a ious au ho s [
7
–
9
]. The e is li le in o ma ion in
scien i ic a icles dealing wi h he measu emen and e alua ion o he explosion pa ame e s
o polyme s [
10
]. The in luence o addi i es on he i e pa ame e s o he polyme mus
always be e i ied by labo a o y measu emen s.
P e en ing explosion haza ds in ol es knowing he cha ac e is ics o dus pa ame e s,
such as he minimum igni ion ene gy (MIE), he maximum a e o p essu e ise (explosion
cons an —K
s
), he dus minimum oxygen concen a ion (MOC), he maximum p essu e
(P
max
), he minimum igni ion empe a u e o he dus laye (MITL), he minimum igni ion
empe a u e o he dus cloud (MITC) o he limi ing oxygen concen a ion (LOC) [
6
,
11
,
12
].
The explosion pa ame e s in his s udy a e measu ed acco ding o he EN 14034
s anda d in a sphe ical explosion chambe [
13
]. Du ing he measu emen , p essu e changes
a e eco ded a a a e o a leas 1000/s. Igni ion o he dispe sed cloud o he sample is
ensu ed by an igni e wi h an ene gy o 2
×
5 kJ. The igni ion empe a u e o dispe sed dus
om a ho su ace is de e mined in a G-G u nace acco ding o EN ISO/IEC 80079-20-2 [
14
].
The igni ion o he dus a e i s dispe sion in he hea ed ube is isually obse ed. The
au ho s also deal wi h de e mining and assessing he i e pa ame e s o di e en ypes o
samples unde di e en condi ions [15,16].
The aim o he esea ch was o in es iga e and analyze he i e and explosion cha ac e -
is ics o a ious polyme powde s commonly used in enginee ing p oduc ion echnologies.
Thanks o conduc ion o comp ehensi e expe imen al s udies, his pape p o ides aluable
insigh in o he beha io o polyme powde s unde di e en condi ions and concen a ions,
while shedding ligh on po en ial isks and sa e y implica ions in indus ial se ings.
Unde s anding he explosion cha ac e is ics is i al o p e en ing dus explosions.
Measu ing he explosion se e i y and igni ion sensi i i y pa ame e s o polyme dus is
o u mos impo ance o en e p ises in o de o p e en and mi iga e po en ial polyme
dus explosions.
2. Ma e ials and Me hods
Th ee samples o polyme s used in p oduc ion echnologies we e es ed—PA12
(polyamide), UMHW PE (polye hylene) and PP (polyp opylene). The samples we e no
ea ed be o e he measu emen . The cha ac e iza ion o hei p ope ies (g anulome y,
LSM, SEM, X- ay and FTIR) is p esen ed in he ollowing sec ions o he p esen ed a icle.
2.1. Polyamide (PA) 12
The s udy in es iga ed polyamide 12 by VESTOSINT
®
X7004 ( ade name), a poly-
me polyamide 12 powde u ilized o injec ion-molded pa s and high-quali y sin e ed
coa ings. Acco ding o he Ma e ial Sa e y Da a Shee (MSDS), he mel ing poin o PA12 is
180 ◦C [17,18].
The mog a ime ic analysis [
19
] demons a ed ha he mel ing poin o PA12 is
185 ◦C, wi h he decomposi ion o i s chains commencing a a empe a u e o 325 ◦C.
In ou p e ious s udy, he polyme powde PA12 Sin e i u ilized in lase sin e ing
was ound o be known o exhibi ing explosi e cha ac e is ics. The highes explosion
o e p essu e eco ded o he sample was 6.78 ba a a concen a ion o 750 g·m−3[20].
Polyme s 2023,15, 4203 3 o 19
Ano he s udy ocused on he incendia y powde PA12 wi h a bimodal pa icle size
dis ibu ion (10
µ
m and 55
µ
m). I was e ealed ha he minimum igni ion ene gy o PA12
is below 40 mJ o concen a ions app oaching 1000 g·m−3[11].
In he ield o lase sin e ing, semi-c ys alline he moplas ics, pa icula ly polyamides
(PA12 and PA11), a e he mos commonly u ilized polyme s. These polyamides accoun
o o e 95% o he a ailable powde used in he polyme addi i e manu ac u ing ma ke
wi hin he indus y [21,22].
2.2. Polyp opylene (PP)
Fo he measu emen s, na u al polyp opylene om Bo ealis (Vienna, Aus ia) known
as Bo Plus SE523MO was u ilized. This pa icula g ade o polyp opylene is in ended
o o a ional molding applica ions and has been specially designed o imp o e impac
pe o mance, pa icula ly in low- empe a u e condi ions [23,24].
Polyp opylene (PP), a ype o polyme , is widely u ilized in a ious indus ies, includ-
ing anspo a ion, u ni u e, au omo i e, insula ion, elec onics, elec ic casings, in e io
deco a ions, and a chi ec u al ma e ials [25,26].
Na u al polyp opylene is an o ganic subs ance ha is lammable. The in luence o he
addi i e ammonium polyphospha e on lammabili y and explosi eness was discussed by
he au ho s in [
26
]. The he mal decomposi ion empe a u e o PP in he ai a mosphe e was
ound o be 250
◦
C. The pa icle size dis ibu ion was obse ed o each
d(10) = 8.64 µm
,
d(50) = 29.2
µ
m, and d(90) = 128
µ
m. The maximum alues o P
max
and K
s
we e measu ed
a 8 ba and 257 ba
·
m
·
s
−1
, espec i ely. P
max
and K
s
exhibi ed an ini ial inc ease wi h he
ise in dus concen a ion, ollowed by a dec ease. Fu he mo e, he minimum explosible
concen a ion (MEC) o PP powde s was de e mined o be 25 g
·
m
−3
[
26
]. The mel ing
poin o PP was in he ange o 150–166 ◦C, lash poin >300 ◦C [27,28].
2.3. Ul a-High Molecula Weigh Polye hylene (UHMW-PE)
Fo he expe imen , a powde o ul a-high molecula weigh polye hylene (UHMW-
PE), known as GUR
®
2024-PE-UHMW and p oduced by Celanese (I ing, TX, USA) was
used. This ma e ial demons a es a signi ican ly highe molecula weigh compa ed o
s anda d PE and exhibi s a densi y o 930 kg/m
3
. UHMW-PE is known o i s high wea
esis ance, high oughness, high impac s eng h and low ic ion coe icien , as well as
du abili y, biocompa ibili y and chemical ine ness and excellen mechanical cha ac e is ics,
e en in c yogenic condi ions. I s MFR (mel low a e) empe a u e is 190
◦
C, and i can be
p ocessed h ough comp ession molding and ilm ex usion echniques [29].
The mel ing poin o UHMW-PE was ound o be a ound 136
◦
C, and he decom-
posi ion o i s chains begins a a empe a u e o 429
◦
C, as shown by he mog a ime ic
analysis [30].
Typically, he UHMW-PE powde , as i is a e polyme iza ion, unde goes p ocess-
ing h ough am ex usion o comp ession molding echniques a ele a ed empe a u es
(200–240 ◦C) and high p essu es (8–10 MPa) [31]. These p ocesses a e in ica e, cos ly and
ime-consuming, o en equi ing se e al hou s o comple e. In 2007, a new app oach o
UHMW-PE p ocessing was in oduced, known as impac compac ion [
32
]. This me hod in-
ol es applying a se ies o blows om an impac o o he powde enclosed in a me al mold,
esul ing in cyclic impac compac ion. This echnology allows o he apid p oduc ion o
small, la -shaped pa s in jus a ew minu es.
2.4. G anulome y, Topog aphy (LSM, SEM), X- ay, FTIR and TGA o he Samples
These echniques a e commonly used in ma e ials science and esea ch o analyze he
p ope ies, composi ion and beha io o a ious ma e ials. They p o ide aluable insigh
in o he s uc u e and cha ac e is ics o ma e ials a di e en le els o de ail.
Polyme s 2023,15, 4203 4 o 19
2.4.1. G anulome y
The pa icle size dis ibu ion o he polyamide 12, polyp opylene, and UHMWpolye hy-
lene samples was de e mined using sie e analysis. This analysis p ocedu e ollowed he EN
933-1 S anda d [
33
]. Sie e analysis was ca ied ou using a Re sch AS 200 sie ing machine
(Re sch GmbH, Haan, Ge many) o 15 min wi h an ampli ude o 2 mm/G. The esul s o he
sie e analysis, including he median alues, a e p esen ed in Table 1. Figu es 1and 2show
he pa icle shapes o he polyamide 12, polyp opylene, and UHMW
polye hylene powde s.
Table 1.
P opo ion o pa icle sizes in he samples o polyamide 12, polyp opylene and
UHMW polye hylene.
Sie e Size
(µm)
Sample
Polyamide 12 UMHW Polye hylene Polyp opylene
% w/w Cumula i e
%% w/w Cumula i e
%% w/w Cumula i e
%
500 0.08 100 32.64 100 0 100
355 0.14 99.92 29.34 67.36 1.61 100
250 0.58 99.78 21.18 38.02 8.11 98.39
180 12.11 99.2 7.42 16.84 14.86 90.28
125 43.62 87.09 6.04 9.42 19.98 75.42
90 35.12 43.47 1.47 3.38 24.09 55.44
63 7.23 8.35 1.29 1.91 17.81 31.35
45 0.91 1.12 0.53 0.62 11.62 13.54
<45 0.21 0.21 0.09 0.09 1.92 1.92
median 95 µm 293 µm 84 µm
Polyme s 2023, 15, x FOR PEER REVIEW 5 o 22
(a) (b)
(c)
Figu e 1. Con ocal LSM (lase scanning mic oscope) images o pa icles o (a) polyamide 12, (b)
polyp opylene, and (c) UHMW polye hylene.
Figu e 1.
Con ocal LSM (lase scanning mic oscope) images o pa icles o (
a
) polyamide
12, (b) polyp opylene, and (c) UHMW polye hylene.
Polyme s 2023,15, 4203 5 o 19
Polyme s 2023, 15, x FOR PEER REVIEW 6 o 22
(a) (b)
(c)
Figu e 2. SEM (scanning elec on mic oscope) images o ac u e su aces o (a) polyamide 12, (b)
polyp opylene, and (c) UHMW polye hylene.
2.4.2. Topog aphy
The su ace cha ac e is ics o powde pa icles we e eco ded using a ZEISS LSM700
(Ca l Zeiss AG, Obe kochen, Ge many) scanning con ocal mic oscope. A 405 nm ligh
sou ce was employed, and when combined wi h an Epi-plan-Apoch oma 100×/0.95 ob-
jec i e, i allowed o achie ing esolu ion s ep sizes o 110 nm along he X and Y axes and
60 nm along he Z axis, as depic ed in Figu es 1 and 2.
2.4.3. X- ay
Figu e 3 shows he XRD pa e ns eco ded o each polyme powde in es iga ed.
The X- ay diff ac ion measu emen s we e pe o med using a PANaly ical Empy ean di -
ac ome e (Mal e n Panaly ical L d., Mal e n, UK) wi h a Ni- il e ed Cu–Kα adia ion.
XRD pa e ns we e eco ded in he ange o 10–110° 2The a.
Figu e 3a shows he XRD pa e n o he in es iga ed polyamide 12 powde . The ob-
ained XRD pa e n con i ms he p esence o he c ys alline γ phase (peaks a 11.2° and
21.5° 2The a); howe e , basically no peaks o he α phase could be iden i ied [34] (PDF 00-
057-1433) [35–39].
The p esence o c ys alline polyp opylene can be con i med o Sample 2, based on
Figu e 3b. All peaks can be ela ed o he iso ac ic α o m o polyp opylene, based on he
JCPDS ICCDD da abase PDF 00-061-1416. This is in line wi h mul iple publica ions [40–
43]. Fo polyp opylene, a β o m is also epo ed o o m unde ce ain condi ions [44,45].
Howe e , his was no ound in ou in es iga ed sample.
The XRD pa e n o he UHMW polye hylene is shown in Figu e 3c. A e y good
o e lap wi h mul iple publica ions in es iga ing UHMW polye hylene was ound
[31,46,47]. In e es ingly, he diff ac ion pa e n o UHMW polye hylene ma ches he one
o HD-PE [41], JCPDS ICCDD da abase PDF 00-060-0986).
Figu e 2.
SEM (scanning elec on mic oscope) images o ac u e su aces o (
a
) polyamide 12,
(b) polyp opylene, and (c) UHMW polye hylene.
2.4.2. Topog aphy
The su ace cha ac e is ics o powde pa icles we e eco ded using a ZEISS LSM700
(Ca l Zeiss AG, Obe kochen, Ge many) scanning con ocal mic oscope. A 405 nm ligh
sou ce was employed, and when combined wi h an Epi-plan-Apoch oma 100
×
/0.95
objec i e, i allowed o achie ing esolu ion s ep sizes o 110 nm along he X and Y axes
and 60 nm along he Z axis, as depic ed in Figu es 1and 2.
2.4.3. X- ay
Figu e 3shows he XRD pa e ns eco ded o each polyme powde in es iga ed. The
X- ay di ac ion measu emen s we e pe o med using a PANaly ical Empy ean di ac-
ome e (Mal e n Panaly ical L d., Mal e n, UK) wi h a Ni- il e ed Cu–K
α
adia ion. XRD
pa e ns we e eco ded in he ange o 10–110◦2The a.
Figu e 3a shows he XRD pa e n o he in es iga ed polyamide 12 powde . The
ob ained XRD pa e n con i ms he p esence o he c ys alline
γ
phase (peaks a 11.2
◦
and
21.5
◦
2The a); howe e , basically no peaks o he
α
phase could be iden i ied [
34
] (PDF
00-057-1433) [35–39].
The p esence o c ys alline polyp opylene can be con i med o Sample 2, based on
Figu e 3b. All peaks can be ela ed o he iso ac ic
α
o m o polyp opylene, based on he
JCPDS ICCDD da abase PDF 00-061-1416. This is in line wi h mul iple publica ions [
40
–
43
].
Fo polyp opylene, a
β
o m is also epo ed o o m unde ce ain condi ions [
44
,
45
].
Howe e , his was no ound in ou in es iga ed sample.

Polyme s 2023,15, 4203 6 o 19
Polyme s 2023, 15, x FOR PEER REVIEW 7 o 22
(a)
(b)
Figu e 3. Con .
Polyme s 2023,15, 4203 7 o 19
Polyme s 2023, 15, x FOR PEER REVIEW 8 o 22
(c)
Figu e 3. X- ays o (a) polyamide 12, (b) polyp opylene, and (c) UHMW polye hylene.
2.4.4. FTIR
The ATR-FTIR spec a we e ob ained using a Va ian FT-IR Spec ome e 660 om
Agilen Technologies, Inc., loca ed in San a Cla a, CA, USA. The specimens we e di ec ly
placed on a diamond c ys al o he ATR accesso y known as GladiATR, manu ac u ed by
PIKE Technology Inc. in Madison, WI, USA. The esul ing spec a unde wen co ec ion
o accoun o ai abso bance in he backg ound. These spec a we e eco ded u ilizing a
Va ian Resolu ions P o ins umen and in ol ed measu emen s wi hin he 4000–400 cm−1
ange. Each spec um was acqui ed 256 imes a a esolu ion se ing o 4, as illus a ed in
Figu e 4.
Figu e 3. X- ays o (a) polyamide 12, (b) polyp opylene, and (c) UHMW polye hylene.
The XRD pa e n o he UHMW polye hylene is shown in Figu e 3c. A e y good
o e lap wi h mul iple publica ions in es iga ing UHMW polye hylene was ound [
31
,
46
,
47
].
In e es ingly, he di ac ion pa e n o UHMW polye hylene ma ches he one o HD-PE [
41
],
JCPDS ICCDD da abase PDF 00-060-0986.
2.4.4. FTIR
The ATR-FTIR spec a we e ob ained using a Va ian FT-IR Spec ome e 660 om
Agilen Technologies, Inc., loca ed in San a Cla a, CA, USA. The specimens we e di ec ly
placed on a diamond c ys al o he ATR accesso y known as GladiATR, manu ac u ed by
PIKE Technology Inc. in Madison, WI, USA. The esul ing spec a unde wen co ec ion
o accoun o ai abso bance in he backg ound. These spec a we e eco ded u ilizing a
Va ian Resolu ions P o ins umen and in ol ed measu emen s wi hin he 4000–400 cm
−1
ange. Each spec um was acqui ed 256 imes a a esolu ion se ing o 4, as illus a ed in
Figu e 4.
Figu e 4c demons a es he in a ed spec um o UHMW polye hylene wi h abso p ion
bands which co espond o he ollowing chemical s uc u e—2911 cm
−1
(CH
2
asymme ic
s e ching ib a ions), 2845 cm
−1
(CH
2
symme ic s e ching ib a ions), 1460 cm
−1
(CH
2
bending ib a ions) and 716 cm−1(C–CH2 ocking ib a ions) [48,49].
Figu e 4b illus a es he spec um o PP. Abso p ion bands loca ed a speci ic wa enum-
be s co espond o he ollowing unc ional g oups—2948 cm
−1
(CH
3
asymme ic s e ching
ib a ions), 2915 cm
−1
(CH
2
asymme ic s e ching ib a ions), 2870 cm
−1
(CH
3
symme ic
s e ching ib a ions), 2837 cm
−1
(CH
2
symme ic s e ching ib a ions), 1451 cm
−1
(CH
3
symme ic bending ib a ions), 1374 cm
−1
(CH
3
umb ella mode), 1164 cm
−1
(C–H wagging
ib a ions, CH
3
ocking ib a ions), 995 cm
−1
(CH
3
ocking ib a ions, C–C s e ching
ib a ions), 970 cm
−1
(CH
3
ocking ib a ions, C–C s e ching ib a ions), 838 cm
−1
(C–H
ocking ib a ions) and 811 cm−1(C–C s e ching ib a ions) [50,51].
The spec um o polyamide 12 (Figu e 4c) shows he peaks a he indica ed wa enum-
be s which co espond o he ollowing unc ional g oups—3280 cm
−1
(N–H s e ching
ib a ions), 3083 cm
−1
(o e one o N–H bend), 2914 cm
−1
(CH
2
asymme ic s e ching
ib a ions), 2846 cm
−1
(CH
2
symme ic s e ching ib a ions), 1633 cm
−1
(Amide I, C=O
s e ching ib a ions), 1542 cm
−1
(Amide II, N–H in plane bending ib a ions), 1460 cm
−1
Polyme s 2023,15, 4203 8 o 19
+ 1435 cm
−1
+ 1364 cm
−1
(C–H bending ib a ions), 1263 cm
−1
(Amide III, C–N s e ch)
and 718 cm−1(N–H ou -o -plane bending ib a ions) [52–54].
Polyme s 2023, 15, x FOR PEER REVIEW 9 o 22
(a)
(b)
Figu e 4. Con .
Polyme s 2023,15, 4203 9 o 19
Polyme s 2023, 15, x FOR PEER REVIEW 10 o 22
(c)
Figu e 4. In a ed spec a o (a) polyamide 12, (b) polyp opylene, and (c) UHMW polye hylene.
Figu e 4c demons a es he in a ed spec um o UHMW polye hylene wi h abso p-
ion bands which co espond o he ollowing chemical s uc u e—2911 cm−1 (CH2 asym-
me ic s e ching ib a ions), 2845 cm−1 (CH2 symme ic s e ching ib a ions), 1460 cm−1
(CH2 bending ib a ions) and 716 cm−1 (C–CH2 ocking ib a ions) [48,49].
Figu e 4b illus a es he spec um o PP. Abso p ion bands loca ed a speci ic wa e-
numbe s co espond o he ollowing unc ional g oups—2948 cm−1 (CH3 asymme ic
s e ching ib a ions), 2915 cm−1 (CH2 asymme ic s e ching ib a ions), 2870 cm−1 (CH3
symme ic s e ching ib a ions), 2837 cm−1 (CH2 symme ic s e ching ib a ions), 1451
cm−1 (CH3 symme ic bending ib a ions), 1374 cm−1 (CH3 umb ella mode), 1164 cm−1 (C–
H wagging ib a ions, CH3 ocking ib a ions), 995 cm−1 (CH3 ocking ib a ions, C–C
s e ching ib a ions), 970 cm−1 (CH3 ocking ib a ions, C–C s e ching ib a ions), 838
cm−1 (C–H ocking ib a ions) and 811 cm−1 (C–C s e ching ib a ions) [50,51].
The spec um o polyamide 12 (Figu e 4c) shows he peaks a he indica ed wa e-
numbe s which co espond o he ollowing unc ional g oups—3280 cm−1 (N–H s e ch-
ing ib a ions), 3083 cm−1 (o e one o N–H bend), 2914 cm−1 (CH2 asymme ic s e ching
ib a ions), 2846 cm−1 (CH2 symme ic s e ching ib a ions), 1633 cm−1 (Amide I, C=O
s e ching ib a ions), 1542 cm−1 (Amide II, N–H in plane bending ib a ions), 1460 cm−1
+ 1435 cm−1 + 1364 cm−1 (C–H bending ib a ions), 1263 cm−1 (Amide III, C–N s e ch) and
718 cm−1 (N–H ou -o -plane bending ib a ions) [52–54].
2.5. MIT o Dispe sed Dus
The measu emen o minimum igni ion empe a u e (MIT) o dispe sed dus was
ca ied ou using s anda dized equipmen known as he Godbe –G eenwald u nace, as
depic ed in Figu e 5. This u nace is speci ically designed o de e mine he MIT o dis-
pe sed dus pa icles. In his es , small quan i ies o dus a e di ec ed e ically down-
wa d h ough a hea ed u nace, and any igni ion is de ec ed h ough isual inspec ion.
The es ma e ial is in oduced in o he u nace using an ai blas o dispe sion. I is
wo h no ing ha since he majo i y o he sample comp ises wo ac ions (>32 µm, >45
µm), he esul ing MIT alue is p ima ily in luenced by hese wo ac ions. O he ac-
ions, due o hei lowe pe cen age in he sample, ha e a negligible impac on he MIT
alue o he dispe sed dus when i is in con ac wi h a ho su ace.
The amoun o dus used o es ing is 0.15 g, which co esponds o he concen a ion
associa ed wi h he highes Pmax alue. The dus is dispe sed unde ai p essu es o 20 kPa
and 50 kPa. Igni ion is ecognized i a bu s o lame is obse ed below he end o he
Figu e 4. In a ed spec a o (a) polyamide 12, (b) polyp opylene, and (c) UHMW polye hylene.
2.5. MIT o Dispe sed Dus
The measu emen o minimum igni ion empe a u e (MIT) o dispe sed dus was
ca ied ou using s anda dized equipmen known as he Godbe –G eenwald u nace, as
depic ed in Figu e 5. This u nace is speci ically designed o de e mine he MIT o dispe sed
dus pa icles. In his es , small quan i ies o dus a e di ec ed e ically downwa d h ough
a hea ed u nace, and any igni ion is de ec ed h ough isual inspec ion.
Polyme s 2023, 15, x FOR PEER REVIEW 11 o 22
u nace ube. Fo each combina ion o empe a u e and p essu e, i e measu emen s we e
conduc ed, and he measu emen s we e conside ed posi i e (“YES”) i a leas one es
yielded igni ion.
The MIT alue o he dispe sed dus is de e mined as he lowes u nace empe a-
u e a which igni ion occu ed, wi h a 20 K sub ac ion, acco ding o he de ined p oce-
du e [14]. Due o he cha ac e is ics o he dus as indica ed in he Ma e ial Sa e y Da a
Shee (MSDS), speci ically i s mel ing poin o 180 °C, MIT es ing o se led dus was no
pe o med.
Figu e 5. C oss-sec ion o Godbe –G eenwald u nace [55].
2.6. Explosion Pa ame e s
The explosion pa ame e s o he samples we e de e mined using he KV 150M2 ex-
plosion chambe (OZM Resea ch, H ochů Týnec, Czech Republic) (Figu es 6 and 7).
Comp essed ai om a p essu ized essel (6.5 L a 10 ba ) was used o dispe se he dus .
The chambe has a olume o 365 L.
To pe o m he es , he sample was placed on a dispe se pla e and dispe sed using
a s eam o comp essed ai . Subsequen ly, he sample was igni ed using a py o echnic
igni e wi h an ene gy o 2 × 5 kJ. The igni e was cen ally loca ed wi hin he explosion
chambe in acco dance wi h EN 14034 S anda d [13]. The e was a 350 ms delay be ween
opening he dispe sing al e and ac i a ing he igni e .
P essu e changes wi hin he chambe du ing he dus cloud explosion we e eco ded
using p essu e ansduce s. These measu emen s we e eco ded a a a e o 50,000/s. P es-
su e changes we e eco ded a a ious dus concen a ions. Each concen a ion was es ed
h ee imes, and he highes alue ob ained du ing hese measu emen s was eco ded.
Figu e 5. C oss-sec ion o Godbe –G eenwald u nace [55].
Polyme s 2023,15, 4203 16 o 19
Fo he UHMW polye hylene sample, he highes alues we e eco ded a a concen a-
ion o 500 g
·
m
−3
. The explosion p essu e alue P
max
was 6.47 ba and he a e o p essu e
ise was 135.9 ba
·
s
−1
(K
s
= 97.1 ba
·
m
·
s
−1
). The lowe explosi e limi o he sample was
60 g
·
m
−3
. The same ime esponse o he igni ion sou ce was obse ed o bo h lammable
polyme samples.
No explosion was obse ed in he polyp opylene sample a any o he measu ed
concen a ions. Despi e he ac ha polyp opylene is a lammable subs ance, he addi i es
con ained in his polyme make i non- lammable. In p ac ice, ino ganic subs ances (ox-
ides, ca bona es, phospha es, gene ally a ious sal s, e c.) o special o ganic subs ances
(an ioxidan s) can be used as addi i es.
The esul s (Tables 5and 6) o he measu emen s in acco dance wi h he EN ISO/IEC
80079 S anda d [
14
] show ha he MIT o dispe sed dus o polyamide 12 is 350
◦
C and
he MIT o he UHMW polye hylene sample is 320
◦
C. Polyp opylene did no igni e when
measu ing he MIT dispe sed dus . The use o polyp opylene ma e ial is sa e in he en i e
empe a u e ange (up o 450
◦
C). Polyamide 12 and UHMW polye hylene polyme s can
be sa ely used a empe a u es up o 300 ◦C.
Table 5. Measu ed alues o MIT sample polyamide 12.
Sample Weigh (g) Ai P essu e (kPa) Tempe a u e (◦C) Resul s
0.2 50
450 YES
440 YES
430 YES
420 YES
410 YES
400 YES
390 YES
380 YES
370 NO
0.11 50
370 NO
380 YES
370 NO
Table 6. Measu ed alues o MIT sample UHMW polye hylene.
Sample Weigh (g) Ai P essu e (kPa) Tempe a u e (◦C) Resul s
0.11 50
370 YES
360 YES
350 YES
340 NO
4. Conclusions
The i e pa ame e s o h ee polyme samples used in p oduc ion echnologies we e de-
e mined. Cu en ly, p oduc ion echnologies wo k wi h polyme s mo e and
mo e equen
.
Se e al me hods can be used o cha ac e ize samples and hei chemical composi ion.
The polyme s p esen ed in his scien i ic s udy a e composed o se e al componen s (poly-
me + addi i es) and X- ay, FTIR, and TGA me hods we e used o hei cha ac e iza ion.
Polyme s ha e a high con en o he combus ible majo i y componen (polyme ). They also
con ain a small con en o addi i es ha a ec i e pa ame e s.
They o en use powde y ma e ials ha can be lammable and explosi e. Despi e he
ac ha he basic componen o such ma e ials a e polyme s, a ious modi ica ions and
addi i es can signi ican ly change hei i e p ope ies. Based on he measu emen o i e
pa ame e s, i is hen possible o assess he sa e y o hei use.
The i e pa ame e s o h ee ypes o polyme s we e compa ed in he esea ch desc ibed
in his a icle. The esul s allow us o conclude ha wo o he h ee samples a e lammable
and explosi e.

Polyme s 2023,15, 4203 17 o 19
The LEL alues a e 30 and 60 g
·
m
−3
, he maximum explosion p essu e is mo e
han 6 ba g and he explosion cons an is 100–135 ba
·
m
·
s
−1
. The minimum igni ion
empe a u e o dispe sed dus om a ho su ace is in he ange o 320–350
◦
C. The e o e,
when using hese ma e ials, i is necessa y o apply he p inciples o explosion p o ec ion
o hei sa e use. The polyp opylene sample was e alua ed as non- lammable and non-
explosi e. I con ains addi i es ha make i non- lammable. Polyp opylene use is sa e,
e en when i comes o dispe sion and con ac wi h a ho su ace. I can be concluded ha
he ecommended way o inc easing he i e sa e y le el o polyme s is by use o sui able
addi i es. This can signi ican ly inc ease he i e sa e y o polyme ma e ials.
F om he esul s, i can be concluded ha he polyme s used in addi i e enginee ing
echnologies can be lammable o non- lammable. The non- lammabili y o polyme s is
usually achie ed by addi i es. The use o such polyme s is hen sa e om he poin o iew
o i e isk.
Howe e , he majo i y o polyme s used in indus y ha e a signi ican i e isk. The e-
o e, i is impo an o ocus on hese lammable polyme s. Fi e pa ame e s a e basic da a
necessa y o he design o e ec i e explosion p e en ion measu es (e.g., en ila ion o ex-
plosion en elie ). The speci ic design o explosion p e en ion is always a combina ion o
i e pa ame e s o polyme s and design and layou pa ame e s in he p oduc ion company.
The de elopmen o polyme s in he ield o addi i e enginee ing echnology is s ill
p og essing. New ypes o addi i es a e being de eloped o polyme s. The e o e, in
he u u e i is possible o ocus on de e mining he i e pa ame e s o such new ypes o
polyme s. S udies will ocus on polyme s and hei addi i es, which can inc ease he le el
o sa e y in indus ial ope a ions in he u u e.
Au ho Con ibu ions:
R.K., Z.S. and E.B. concei ed and designed he expe imen s; R.K., Z.S., E.B.,
L.K., P.R., L.B., D.M., P.G. and F.J. pe o med he expe imen s and analyzed he da a; R.K. and Z.S.
managed all he expe imen s and w i ing p ocess as he co esponding au ho s. All au ho s discussed
he esul s and commen ed on he manusc ip . All au ho s ha e ead and ag eed o he published
e sion o he manusc ip .
Funding:
This esea ch was suppo ed by he Cul u al and Educa ional G an Agency o he Minis y
o Educa ion, Science, Resea ch and Spo o he Slo ak Republic unde Con ac No. 020STU-4/2021
and by he Slo ak Resea ch and De elopmen Agency unde Con ac No. APVV-21-0187.
Ins i u ional Re iew Boa d S a emen : No applicable.
Da a A ailabili y S a emen :
The da a p esen ed in his s udy a e a ailable on eques om he
co esponding au ho .
Con lic s o In e es : The au ho s decla e no con lic o in e es .
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