molecules
A icle
Tes s on Ma e ial Compa ibili y o Phase Change
Ma e ials and Selec ed Plas ics
Milan Os ý* , Syl a Ban o áand Ka el S uhala
Facul y o Ci il Enginee ing, B no Uni e si y o Technology; 602 00 B no, Czech Republic;
[email p o ec ed].cz (S.B.); [email p o ec ed].cz (K.S.)
*Co espondence: os y[email p o ec ed].cz; Tel.: +420-541-147-499
Recei ed: 28 Feb ua y 2019; Accep ed: 8 Ap il 2019; Published: 10 Ap il 2019


Abs ac :
P ac ical applica ions o Phase Change Ma e ials (PCMs) o en equi e hei encapsula ion
in o he ma e ials, such as me als o plas ics. This aises he issue o compa ibili y be ween PCMs
and encapsula ing ma e ials, which has s ill no been su icien ly add essed. The s udy p esen ed
he e ollows exis ing esea ch and p o ides expe imen al e alua ion o he sui abili y o selec ed
PCMs o p oposed in eg a ion in building s uc u es. Two o ganic PCMs, wo ino ganic PCMs
and h ee ep esen a i e plas ics (polyp opylene (PP-H), high densi y polye hylene (PE-HD) and
poly inylchlo ide (PVC-U)) we e selec ed o compa ibili y es s. E alua ion o he esul s is based on
he mass a ia ions o he plas ic samples du ing he es pe iod. Plas ic samples we e imme sed in
PCMs and subjec ed o pe iodic hea ing and cooling ( o 16 weeks) in a small en i onmen al chambe
simula ing eal ope a ional condi ions. The esul s show ha he o ganic PCMs ha e a g ea e abili y
o pene a e he PE-HD and PP-H compa ed wi h he ino ganic PCMs. The pene a ion o all PCMs
was mos no able du ing he i s ou weeks o he expe imen . La e i slowed down signi ican ly.
O e all, he mass changes in PE-HD and PP-H samples did no exceed 6.9% when imme sed in
o ganic PCMs and 1.8% in ino ganic PCMs. PVC-U samples exhibi ed almos negligible (less han
0.1%) mass a ia ion in all cases.
Keywo ds: encapsula ion; phase change ma e ials; PCMs; hea s o age; buildings
1. In oduc ion
The mal ene gy s o age sys ems can sol e he ime misma ch be ween ene gy gene a ion and
ene gy demand and di e ence in p ice be ween peak and o -peak daily hou s. Such issues a e ypical
o applica ions o enewable ene gy sou ces, o example, passi e sola gains [
1
]. The applica ions o
enewable ene gy sou ces a e essen ial o he design and e ec i e ope a ion o passi e houses [
2
].
Mo eo e , he mal ene gy s o age can be employed o anspo o hea i he hea sou ce and hea
consume , (e.g., a building) a e no di ec ly connec ed. The app oach i s men ioned o u ilizing
enewable ene gy is ep esen ed by ac i e sys ems in eg a ed in building se ices. Wa e is commonly
u ilized as a medium o he mal ene gy s o age and anspo in such sys ems due o i s high s o age
densi y; especially when he enewable ene gy o o -peak elec ici y is conside ed. These ac i e
sys ems equi e u ili y ooms equipped wi h sensible hea s o age uni s. The second app oach is based
on di ec u iliza ion o passi e sola ene gy gains o hea ing ( o educe ope a ing cos s). The s o age
capaci y o building s uc u es is a key issue in his case.
La en Hea S o age (LHS) echnology ep esen s an ad anced app oach o hea s o age ha can be
employed when he amoun o hea s o age medium is limi ed. Highe hea s o age densi y is caused
by abso p ion o elease o la en hea du ing mel ing o solidi ica ion o s o age medium. Mo eo e ,
a sensible hea s o age p ocess in a solid o liquid s a e is ce ainly u ilized oo. Phase Change Ma e ials
(PCMs) o building applica ions can be selec ed om h ee g oups [3]:
Molecules 2019,24, 1398; doi:10.3390/molecules24071398 www.mdpi.com/jou nal/molecules
Molecules 2019,24, 1398 2 o 11
•O ganic PCMs ep esen ed by pa a ins and non-pa a ins
•Ino ganic PCMs desc ibes as sal hyd a es o me allics
•
Eu ec ics cha ac e ized as a mix u e o wo o mo e componen s, o example, o ganic-o ganic,
o ganic-ino ganic and ino ganic-ino ganic eu ec ics
Due o he change in phase he LHS media mus be encapsula ed and sealed p io o applica ion in
buildings. This could be done in se e al di e en ways. PCMs can be ully enclosed wi hin a capsule o
con aine (encapsula ed). The size o he capsules a ies. The e a e “mac o capsules” la ge han 1 mm,
“mic o capsules” be ween 1
µ
m and 1 mm and “nano capsules” smalle han 1
µ
m [
4
]. The shape o he
capsules a ies as well. Mos no ably he ma co encapsula ion u ilizes wide ange o capsule shapes:
sphe es, ubes, pouches o la con aine s [
5
]. Di ec imp egna ion o po ous building ma e ial wi h
PCM is also possible. The las op ion is applica ion o shape s abilized PCMs consis ing o PCM and
suppo ing ma e ial, ypically high-densi y polye hylene and s y ene-bu adiene-s y ene [
6
]. The ype
o encapsula ion is in luenced by he pu pose o ins alla ion in building s uc u es o building echnical
sys ems. Ma e ial o encapsula ion and me hods o encapsula ion i sel mus mee he equi emen s
on [7]:
•S eng h and lexibili y
•Co osion esis ance
•The mal s abili y in desi ed empe a u e ange o use
•P o ec ion o he en i onmen om ha m ul in e ac ion wi h PCMs
•Su icien su ace o hea ans e
•S uc u al s abili y and easy handling
•A ailabili y
•Non oxici y
The main issue connec ed wi h he applica ion o LHS in buildings is he incompa ibili y o PCMs
and he s o age ma e ial (capsules). This issue is c ucial o es ima es o he du abili y and se ice li e
o LHS componen s and sys ems. Un o una ely, he numbe o published s udies dealing wi h he
issue is a he small. Exis ing s udies could be di ided based on ma e ial o he capsules, commonly
me als and plas ics.
Me als a e good hea conduc o s. The e o e, hei applica ion o PCM encapsula ion is a he
a ac i e. Fo example, Khan e al. [
8
] e alua ed he compa ibili y o (comme cially a ailable)
sal -hyd a e-based PCMs and me al con aine s. They concluded ha only s ainless s eel was compa ible
wi h (mos o ) he es ed PCMs. Simila ly, Ushak e al. [
9
] desc ibed he co osi e e ec o sal
hyd a es (PCMs) on h ee ypes o me al (po en ial con aine ma e ials). The e alua ion was based
on he mass loss in ime. Coppe was he mos a ec ed me al in he e alua ion, while s ainless s eel
was he leas a ec ed. Simila es s e alua ing co osion a es h ough mass loss o he me al (and
plas ic) samples in ime we e p e iously published by Fe e e al. [
10
] o Mone o e al. [
11
]. In ac ,
he issue o co osion is so ob ious ha K ishna e al. p oposed an e alua ion me hodology based on
Ame ican Socie y o Tes ing and Ma e ials (ASTM G1) s anda ds [
12
]. Mo e complex compa ibili y
e alua ion was p esen ed by Sa i e Kaygusuz [
13
]. They e alua ed he compa ibili y o s ea ic,
palmi ic, my is ic and alu ic acids (PCMs) and s ainless s eel, ca bon s eel, aluminium and coppe
(po en ial capsule ma e ials). Thei esea ch is no able especially o applica ion o se e al analy ical
me hods, such as g a ime ic analysis (mass loss in mg cm
−2
), co osion a e (mg day
−1
), mic oscopic
and me allog aphic in es iga ion. B owne e al. [
14
] u ilized g a ime ic analysis and co osion a e o
e alua ion o compa ibili y o se e al me als and one plas ic (po en ial capsule ma e ials) wi h h ee
a y acids, sal hyd a e and Mic onal PCM. They ecommended s ainless s eel as he bes ma e ial o
he encapsula ion o he es ed PCMs. Mo eo e hey concluded ha aluminium, coppe and b ass a e
sui able o applica ion wi h a y acids i some co osion is accep able.
Molecules 2019,24, 1398 3 o 11
Plas ics ep esen a ela i ely low cos ma e ials o encapsula ion compa ed wi h me als and
me al alloys. Plas ics a e widely used in he cons uc ion sec o , o example, polyp opylene and
polye hylene a e common ma e ials in building se ices (e.g., pipes). This seemingly suppo s hei
applica ion o PCM capsules. Un o una ely, plas ics ha e poo he mal conduc i i y and hus he
capsule walls ha e o be as hin as possible.
Gene ally, he e alua ion o compa ibili y be ween plas ics and PCMs (o chemical solu ions
in gene al) is seldom analysed in li e a u e. Resul s in exis ing pape s a e commonly based on he
mass a ia ion [
15
] o on he olume change [
16
] o he plas ics a e exposu e ime. Polyp opylene,
high densi y polye hylene, polye hylene e eph hala e and polys y ene as ep esen a i es o g oup
o plas ics we e es ed as in combina ion wi h selec ed PCM o p oposed cold s o age by
O óe al. [
17
]. Thei compa ibili y e alua ion was based on moni o ing o mass changes du ing
12 weeks. An in e es ing s udy on compa ibili y o plas ic con aine s and PCMs was published by
Láza o e al. [
18
]. They e e sed he common p ocedu e o imme sing plas ics in o PCMs. Ins ead hey
illed PCMs in o bo les made o di e en plas ics. They u ilized g a ime ic analysis o e alua ion o
in e ac ions be ween PCMs and he es ed plas ics.
The esul s o compa ibili y es s a e clea . Selec ion o p ope PCM-capsule pai s is c ucial o
long- e m applica ions in buildings. The consequences o undesi able in e ac ion be ween PCMs and
hei capsules we e summed, o example, by Vasu e al. [19]:
•Con amina ion o luids and pe o a ion in essels and pipes;
•
Reduc ion o con aine wall hickness leads o loss o mechanical s eng h and s uc u al ailu e
o b eakdown;
•Mechanical damage o majo componen s and added complexi y o equipmen ;
•Loss o echnically impo an su ace p ope ies o componen ;
•Reduced alue o goods due o de e io a ion o appea ance.
Figu e 1illus a es he au ho s’ own expe ience wi h he necessi y o PCM-capsule compa ibili y
es s. I shows ino ganic PCM encapsula ed in a bubble oil. This p oduc can be used as hea
s o age laye si ua ed abo e suspended ceiling in o ice buildings. The laye o plas ics is e y hin.
Se ious leakage o PCMs encapsula ed in bubbles was obse ed a e ew yea s o use. The same
p oblem was de ec ed in case o plas ic ubes and aluminium con aine panels jus a e h ee yea s o
ope a ion. I illus a es he necessi y o in es iga ion o compa ibili y be ween PCMs and su ounding
ma e ial. The e is no e idence whe he ino ganic PCMs des oyed he plas ic laye by undesi able
in e ac ion be ween PCM and plas ic en elope only. Bad join s be ween bubbles and damage by pe iodic
changes in olume could be also he eason o he leakage. All aspec s should be aken in o accoun
du ing he design o any s o age componen o sys em. Bu ma e ial compa ibili y seems o be he mos
impo an c i e ion o assessmen o he sui abili y o he p oposed PCM–capsule (plas ic) pai s.
The esea ch desc ibed in his pape ocuses on h ee kinds o plas ics wi h wide use in building
p ac ice. Me als and me al alloys we e excluded because he p ocedu e o e alua ion o hei
compa ibili y wi h PCMs is di e en .
Molecules 2019,24, 1398 4 o 11
Molecules 2019, 24, x FOR PEER REVIEW 3 o 11
applica ion o PCM capsules. Un o una ely, plas ics ha e poo he mal conduc i i y and hus he
capsule walls ha e o be as hin as possible.
Gene ally, he e alua ion o compa ibili y be ween plas ics and PCMs (o chemical solu ions in
gene al) is seldom analysed in li e a u e. Resul s in exis ing pape s a e commonly based on he mass
a ia ion [15] o on he olume change [16] o he plas ics a e exposu e ime. Polyp opylene, high
densi y polye hylene, polye hylene e eph hala e and polys y ene as ep esen a i es o g oup o
plas ics we e es ed as in combina ion wi h selec ed PCM o p oposed cold s o age by O ó e al.
[17]. Thei compa ibili y e alua ion was based on moni o ing o mass changes du ing 12 weeks. An
in e es ing s udy on compa ibili y o plas ic con aine s and PCMs was published by Láza o e al.
[18]. They e e sed he common p ocedu e o imme sing plas ics in o PCMs. Ins ead hey illed
PCMs in o bo les made o di e en plas ics. They u ilized g a ime ic analysis o e alua ion o
in e ac ions be ween PCMs and he es ed plas ics.
The esul s o compa ibili y es s a e clea . Selec ion o p ope PCM-capsule pai s is c ucial o
long- e m applica ions in buildings. The consequences o undesi able in e ac ion be ween PCMs
and hei capsules we e summed, o example, by Vasu e al. [19]:
• Con amina ion o luids and pe o a ion in essels and pipes;
• Reduc ion o con aine wall hickness leads o loss o mechanical s eng h and
s uc u al ailu e o b eakdown;
• Mechanical damage o majo componen s and added complexi y o equipmen ;
• Loss o echnically impo an su ace p ope ies o componen ;
• Reduced alue o goods due o de e io a ion o appea ance.
Figu e 1 illus a es he au ho s’ own expe ience wi h he necessi y o PCM-capsule
compa ibili y es s. I shows ino ganic PCM encapsula ed in a bubble oil. This p oduc can be used
as hea s o age laye si ua ed abo e suspended ceiling in o ice buildings. The laye o plas ics is
e y hin. Se ious leakage o PCMs encapsula ed in bubbles was obse ed a e ew yea s o use. The
same p oblem was de ec ed in case o plas ic ubes and aluminium con aine panels jus a e h ee
yea s o ope a ion. I illus a es he necessi y o in es iga ion o compa ibili y be ween PCMs and
su ounding ma e ial. The e is no e idence whe he ino ganic PCMs des oyed he plas ic laye by
undesi able in e ac ion be ween PCM and plas ic en elope only. Bad join s be ween bubbles and
damage by pe iodic changes in olume could be also he eason o he leakage. All aspec s should
be aken in o accoun du ing he design o any s o age componen o sys em. Bu ma e ial
compa ibili y seems o be he mos impo an c i e ion o assessmen o he sui abili y o he
p oposed PCM–capsule (plas ic) pai s.
The esea ch desc ibed in his pape ocuses on h ee kinds o plas ics wi h wide use in building
p ac ice. Me als and me al alloys we e excluded because he p ocedu e o e alua ion o hei
compa ibili y wi h PCMs is di e en .
(a) (b)
Figu e 1. Phase change ma e ials (PCMs) encapsula ed in bubble oil: (a) View o liquid PCMs on he
su ace; (b) Emp y and de o med bubbles wi h isible solid PCMs on he su ace.
Figu e 1.
Phase change ma e ials (PCMs) encapsula ed in bubble oil: (
a
) View o liquid PCMs on he
su ace; (b) Emp y and de o med bubbles wi h isible solid PCMs on he su ace.
2. Resul s
In e ac ion be ween samples o h ee plas ics and ou PCMs is exp essed by change in mass o
he samples imme sed in each PCM. The expe imen al p ocedu e and e alua ion me hodology a e
desc ibed in Sec ion 4. Table 1shows he mon hly mass changes o all es ed plas ic-PCM combina ions.
Signi ican mass change in polyp opylene (PP-H) and poly inylchlo ide (PVC-U) samples imme sed
in o ganic and ino ganic PCMs is isible on he i s sign. PVC-U samples we e almos ine o PCMs
in all cases and measu ed changes we e negligible compa ed o he o he plas ics es ed.
Table 1. Pe cen age change in mass o es ed plas ics depending on used PCMs h ough ime.
Ma e ial (Plas ics) Time Pe cen age Change in Mass ∆m [%]
Linpa 17 Linpa 1820 SP25 SP22
PP-H
4 weeks 5.7175 5.0474 0.4968 0.8547
8 weeks 6.9493 6.4214 0.4414 1.5721
12 weeks 6.6993 5.9488 0.5609 1.3682
16 weeks 6.9399 6.7153 0.6326 1.7722
PE-HD
4 weeks 5.2100 5.8225 0.3294 0.8979
8 weeks 5.8614 6.2467 1.0484 0.8704
12 weeks 5.5740 6.4250 0.3588 1.2533
16 weeks 5.8169 6.5783 0.6281 1.1381
PVC-U
4 weeks −0.0285 0.0201 0.0107 −0.0199
8 weeks −0.0137 0.0244 0.0333 −0.0106
12 weeks −0.0310 0.0624 −0.0141 −0.0312
16 weeks −0.0256 0.0000 −0.0031 −0.0172
I should be no ed ha no isual changes we e obse ed on he su ace o he samples a e
es ing. Only esidual amoun s o PCMs we e de ec ed on he su ace a e emo al om beake s.
This indica es ha e en long- e m exposu e in PCMs does no a ec he shape o he es ed samples.
S ill, all samples we e cleaned and d ied be o e weighing.
The ollowing sub-sec ions desc ibe he esul s o he expe imen di ided based on he ype o
PCM: o ganic (Sec ion 2.1) and ino ganic (Sec ion 2.2). The cou se o PCMs’ pene a ion in o he ma ix
o he es ed plas ics is exp essed by sepa a e cha s in Figu es 2–5. O e all compa ison o he esul s
is p o ided in Sec ion 2.3 and Figu e 6.
Molecules 2019,24, 1398 5 o 11
2.1. O ganic PCM esul s
The cu es in Figu e 2demons a e as pene a ion o o ganic PCM Linpa 17 in o high densi y
polye hylene (PE-HD) and PP-H du ing he i s ou weeks. Con a y o his beha io , he mass
change o PVC-U is negligible. Simila beha io was obse ed (see Figu e 3) in he second o ganic
PCM, Linpa 1820. The mass change du ing he emaining pa o he expe imen s was almos he
same in bo h PCMs. This means ha he es ed plas ic samples we e almos ully sa u a ed by he
PCMs du ing he i s ou weeks o he expe imen . In he end he maximum mass changes did no
exceed 7% in bo h PCMs.
Molecules 2019, 24, x FOR PEER REVIEW 5 o 11
Figu e 2. Dependence o mass change o es ed plas ics on du a ion o he expe imen o Linpa 17.
Figu e 3. Dependence o mass change o es ed plas ics on du a ion o he expe imen o Linpa
1820.
2.2. Ino ganic PCM Resul s
The pene a ion o ino ganic PCMs in o he ma ix o he es ed plas ics is demons a ed in
Figu es 4 and 5. PVC does no exhibi any signi ican mass changes again. The mass change in
PE-HD and PP-H is lowe compa ed o o ganic PCMs. The maximum mass change o 1.8% was
achie ed wi h PP-H imme sed in Rubi he m SP22.
Figu es 4 and 5 show simila beha io o he samples in he i s weeks o expe imen s as
Figu es 2 and 3: apid pene a ion o PCM. Howe e , con a y o o ganic PCMs, a small mass
g ow h was eco ded e en du ing he es o he expe imen .
Figu e 2. Dependence o mass change o es ed plas ics on du a ion o he expe imen o Linpa 17.
Molecules 2019, 24, x FOR PEER REVIEW 5 o 11
Figu e 2. Dependence o mass change o es ed plas ics on du a ion o he expe imen o Linpa 17.
Figu e 3. Dependence o mass change o es ed plas ics on du a ion o he expe imen o Linpa
1820.
2.2. Ino ganic PCM Resul s
The pene a ion o ino ganic PCMs in o he ma ix o he es ed plas ics is demons a ed in
Figu es 4 and 5. PVC does no exhibi any signi ican mass changes again. The mass change in
PE-HD and PP-H is lowe compa ed o o ganic PCMs. The maximum mass change o 1.8% was
achie ed wi h PP-H imme sed in Rubi he m SP22.
Figu es 4 and 5 show simila beha io o he samples in he i s weeks o expe imen s as
Figu es 2 and 3: apid pene a ion o PCM. Howe e , con a y o o ganic PCMs, a small mass
g ow h was eco ded e en du ing he es o he expe imen .
Figu e 3.
Dependence o mass change o es ed plas ics on du a ion o he expe imen o Linpa 1820.

Molecules 2019,24, 1398 6 o 11
2.2. Ino ganic PCM Resul s
The pene a ion o ino ganic PCMs in o he ma ix o he es ed plas ics is demons a ed in
Figu es 4and 5. PVC does no exhibi any signi ican mass changes again. The mass change in PE-HD
and PP-H is lowe compa ed o o ganic PCMs. The maximum mass change o 1.8% was achie ed wi h
PP-H imme sed in Rubi he m SP22.
Figu es 4and 5show simila beha io o he samples in he i s weeks o expe imen s as
Figu es 2and 3
: apid pene a ion o PCM. Howe e , con a y o o ganic PCMs, a small mass g ow h
was eco ded e en du ing he es o he expe imen .
Molecules 2019, 24, x FOR PEER REVIEW 6 o 11
Figu e 4. Dependence o mass change o es ed plas ics on du a ion o he expe imen o SP25.
Figu e 5. Dependence o mass change o es ed plas ics on du a ion o he expe imen o SP22.
2.3. O e all Resul s
Figu e 6 shows he compa ison o mass changes o PP-H in all PCMs. The eason is ha his
plas ic achie ed he highes mass inc ease du ing he expe imen . The e o e, he igu e well
illus a es he di e ence in mass change due o he imme sion o o ganic and ino ganic PCM. I
should be no ed ha all he alues could ha e been a ec ed by e o s in weighing. Polygonal
unc ions calcula ed o measu ed da a we e used o be e demons a ion o mass change ends
du ing he expe imen s in he igu es.
Figu e 4. Dependence o mass change o es ed plas ics on du a ion o he expe imen o SP25.
Molecules 2019, 24, x FOR PEER REVIEW 6 o 11
Figu e 4. Dependence o mass change o es ed plas ics on du a ion o he expe imen o SP25.
Figu e 5. Dependence o mass change o es ed plas ics on du a ion o he expe imen o SP22.
2.3. O e all Resul s
Figu e 6 shows he compa ison o mass changes o PP-H in all PCMs. The eason is ha his
plas ic achie ed he highes mass inc ease du ing he expe imen . The e o e, he igu e well
illus a es he di e ence in mass change due o he imme sion o o ganic and ino ganic PCM. I
should be no ed ha all he alues could ha e been a ec ed by e o s in weighing. Polygonal
unc ions calcula ed o measu ed da a we e used o be e demons a ion o mass change ends
du ing he expe imen s in he igu es.
Figu e 5. Dependence o mass change o es ed plas ics on du a ion o he expe imen o SP22.
Molecules 2019,24, 1398 7 o 11
2.3. O e all Resul s
Figu e 6shows he compa ison o mass changes o PP-H in all PCMs. The eason is ha his
plas ic achie ed he highes mass inc ease du ing he expe imen . The e o e, he igu e well illus a es
he di e ence in mass change due o he imme sion o o ganic and ino ganic PCM. I should be no ed
ha all he alues could ha e been a ec ed by e o s in weighing. Polygonal unc ions calcula ed o
measu ed da a we e used o be e demons a ion o mass change ends du ing he expe imen s in
he igu es.
Molecules 2019, 24, x FOR PEER REVIEW 7 o 11
Figu e 6. Compa ison o he dependence o mass change o polyp opylene (PP-H) caused by
pa icula PCMs.
3. Discussion
The esul s p esen ed in he p e ious sec ion demons a e di e ences in po en ial compa ibili y
o PP-H, PE-HD and PVC-U wi h ou o ganic and ino ganic PCMs. They show ha
sal -hyd a e-based PCMs ha e a smalle abili y o pene a e he ma ix o he es ed plas ic samples.
Mo eo e , PVC-U was almos wi hou mass change du ing imme sion in all PCMs. Li e a u e
p o ides se e al s udies o compa ison o he PP-H and PE-HD esul s. Sadly, no compa able
s udies dealing wi h PVC-U we e iden i ied by he au ho s.
The eco ded cou se o mass changes o PP-H and PE-HD con i m esul s om expe imen s
wi h pa a in RT20, RT25 and RT27 desc ibed by Cas ellón e al. in [20]. They obse ed he same
end o a he as ini ial sa u a ion ollowed by minimal mass changes la e o PP, PE-LD and
PE-HD. Simila ly o he esea ch p esen ed, Cas ellón e al. also measu ed lowe mass changes o he
speci ied plas ics wi h sal -hyd a e-based PCMs. Di e ences in esul s could be ela ed o
imp o emen s in es p ocedu e (when compa ed wi h [20]) applied in he pape p esen ed. These
include no con ac be ween samples and comple e imme sion o he samples by PCMs due o hei
ancho ing in special oam.
Ano he wo k dealing wi h he same issue is [17]. I shows signi ican ly lowe ma e ial
sa u a ion o PP, HDPE, PET and PS compa ed o he s udy p esen ed. Howe e , he esul s a e
a he incompa able due o he use o di e en ino ganic PCMs. Also, he accu acy o he esul s in
[17] is likely lowe as only one sample was e alua ed each week and s eady-s a e su ounding
condi ions we e applied. The du a ion o he expe imen in [17] was lowe han s anda d
ecommenda ions oo.
The expe imen wi h plas ic bo les p esen ed in [18] also con i ms he di e ences in mass
a ia ion o plas ics in con ac wi h o ganic and ino ganic PCMs. Howe e , i desc ibes de o ma ion
o plas ic samples, which was no obse ed du ing he wo k p esen ed.
4. Ma e ials and Me hods
The expe imen desc ibed e i ies he compa ibili y o selec ed plas ics and PCMs. The aim o
he expe imen is selec ion o he mos sui able ma e ial pai s o u u e de elopmen o PCM
applica ions. The expe imen applies g a ime ic analysis o quan i y he a e o in il a ion o PCMs
in o he plas ic samples. The expe imen al p ocedu e is p esen ed in Figu e 7. I was selec ed based
Figu e 6.
Compa ison o he dependence o mass change o polyp opylene (PP-H) caused by
pa icula PCMs.
3. Discussion
The esul s p esen ed in he p e ious sec ion demons a e di e ences in po en ial compa ibili y o
PP-H, PE-HD and PVC-U wi h ou o ganic and ino ganic PCMs. They show ha sal -hyd a e-based
PCMs ha e a smalle abili y o pene a e he ma ix o he es ed plas ic samples. Mo eo e , PVC-U
was almos wi hou mass change du ing imme sion in all PCMs. Li e a u e p o ides se e al s udies
o compa ison o he PP-H and PE-HD esul s. Sadly, no compa able s udies dealing wi h PVC-U
we e iden i ied by he au ho s.
The eco ded cou se o mass changes o PP-H and PE-HD con i m esul s om expe imen s wi h
pa a in RT20, RT25 and RT27 desc ibed by Cas ellón e al. in [
20
]. They obse ed he same end
o a he as ini ial sa u a ion ollowed by minimal mass changes la e o PP, PE-LD and PE-HD.
Simila ly o he esea ch p esen ed, Cas ellón e al. also measu ed lowe mass changes o he speci ied
plas ics wi h sal -hyd a e-based PCMs. Di e ences in esul s could be ela ed o imp o emen s in es
p ocedu e (when compa ed wi h [
20
]) applied in he pape p esen ed. These include no con ac be ween
samples and comple e imme sion o he samples by PCMs due o hei ancho ing in special oam.
Ano he wo k dealing wi h he same issue is [
17
]. I shows signi ican ly lowe ma e ial sa u a ion
o PP, HDPE, PET and PS compa ed o he s udy p esen ed. Howe e , he esul s a e a he
incompa able due o he use o di e en ino ganic PCMs. Also, he accu acy o he esul s in [
17
] is
likely lowe as only one sample was e alua ed each week and s eady-s a e su ounding condi ions
we e applied. The du a ion o he expe imen in [17] was lowe han s anda d ecommenda ions oo.
Molecules 2019,24, 1398 8 o 11
The expe imen wi h plas ic bo les p esen ed in [
18
] also con i ms he di e ences in mass
a ia ion o plas ics in con ac wi h o ganic and ino ganic PCMs. Howe e , i desc ibes de o ma ion o
plas ic samples, which was no obse ed du ing he wo k p esen ed.
4. Ma e ials and Me hods
The expe imen desc ibed e i ies he compa ibili y o selec ed plas ics and PCMs. The aim o he
expe imen is selec ion o he mos sui able ma e ial pai s o u u e de elopmen o PCM applica ions.
The expe imen applies g a ime ic analysis o quan i y he a e o in il a ion o PCMs in o he plas ic
samples. The expe imen al p ocedu e is p esen ed in Figu e 7. I was selec ed based on li e a u e
e iew. Kass e al. [
21
] e alua ed 18 plas ics in con ac wi h nea bio-oil using a simila modi ied
p ocedu e. O he wo ks u ilizing a simila app oach include o example [14,15].
Molecules 2019, 24, x FOR PEER REVIEW 8 o 11
on li e a u e e iew. Kass e al. [21] e alua ed 18 plas ics in con ac wi h nea bio-oil using a simila
modi ied p ocedu e. O he wo ks u ilizing a simila app oach include o example [14, 15].
Figu e 7. Indi idual s eps o he expe imen al p ocedu e.
Fou PCMs we e selec ed o es ing as ep esen a i es o LHS media applicable o imp o ing
o hea s o age capaci y o buildings: sal -hyd a e-based Rubi he m SP22 and Rubi he m SP25 and
pa a in-based Linpa 17 and Linpa 1820. All o hem a e commonly a ailable on he global ma ke .
Table 2 shows pa ame e s o hese PCMs ob ained wi h Di e en Scanning Calo ime e (DSC)
measu emen . The amoun o la en hea a ies be ween 122 and 152 J·g−1 and he peak empe a u e
be ween 22 and 28 °C.
Table 2. Pa ame e s o selec ed PCMs (measu ed du ing mel ing).
Type P oduc
Name Manu ac u e La en Hea
[J∙g−1]
Onse Tempe a u e
[°C]
Peak Tempe a u e
[°C]
ino ganic SP22 Rubi he m 145 14 25
ino ganic SP25 Rubi he m 122 18 28
o ganic Linpa 17 Sasol 152 21 22
o ganic Linpa 1820 Sasol 141 24 27
Th ee plas ics we e selec ed as po en ial ma e ials o PCM capsules and es ed: PP-H
(polyp opylene), PE-HD (high densi y polye hylene) and PVC-U (poly inylchlo ide). Main
pa ame e s o selec ed plas ics a e p esen ed in Table 3. Gene ally, hese plas ics we e selec ed based
on hei a ailabili y on he ma ke , low cos s and he ac ha hey a e commonly u ilized in he
packaging indus y. PP-H ep esen s he g oup o polyole ins and is classi ied as semi c ys alline
he moplas ic polyme . I is lammable ma e ial wi h low he mal conduc i i y cu en ly used, o
example, in sewe age o d inking wa e supply sys ems. PE-HD is a he moplas ic polyme as well.
I s applica ions in he building indus y include ainwa e pipes o s o age anks, and so on. PVC-U
ep esen s inyl g oup o polyme s. I is a ha dened a ian o common PVC. PVC is widely used in
he building indus y. I s applica ions include wa e p oo ing shee s, window ames o loo ing.
Table 3. Pa ame e s o selec ed plas ics.
Ma e ial The mal Conduc i i y
[W/(m∙K)]
Modulus o Elas ici y
[MPa]
Densi y
[g/cm3]
Mel ing Poin
[°C]
PP-H 0.22 1350 0.92 90
PVC-U 0.20 3000 1.43 80
PE-HD 0.43 1000 0.95 75
The g a ime ic me hod de ined in in e na ional s anda d ISO 175:2000 [22] was u ilized o se
he ini ial condi ions and subsequen ly pe o m he expe imen . Conside ed condi ions o he
expe imen include:
16 weeks imme sion (long- e m es ) o plas ic samples in beake s wi h PCMs (see Figu e 8b).
Repe i i e ou -s age empe a u e cycles in an en i onmen al chambe du ing imme sion.
samples
cu ing
samples
weigh ing
imme sion
in PCMs
he mal
cycling
emo al
om
PCMs
isual
check
samples
weigh ing
Figu e 7. Indi idual s eps o he expe imen al p ocedu e.
Fou PCMs we e selec ed o es ing as ep esen a i es o LHS media applicable o imp o ing
o hea s o age capaci y o buildings: sal -hyd a e-based Rubi he m SP22 and Rubi he m SP25
and pa a in-based Linpa 17 and Linpa 1820. All o hem a e commonly a ailable on he global
ma ke . Table 2shows pa ame e s o hese PCMs ob ained wi h Di e en Scanning Calo ime e (DSC)
measu emen . The amoun o la en hea a ies be ween 122 and 152 J
·
g
−1
and he peak empe a u e
be ween 22 and 28 ◦C.
Table 2. Pa ame e s o selec ed PCMs (measu ed du ing mel ing).
Type P oduc Name Manu ac u e La en Hea [J·g−1]Onse Tempe a u e [◦C] Peak Tempe a u e [◦C]
ino ganic SP22 Rubi he m 145 14 25
ino ganic SP25 Rubi he m 122 18 28
o ganic Linpa 17 Sasol 152 21 22
o ganic Linpa 1820 Sasol 141 24 27
Th ee plas ics we e selec ed as po en ial ma e ials o PCM capsules and es ed:
PP-H (polyp opylene), PE-HD (high densi y polye hylene) and PVC-U (poly inylchlo ide).
Main pa ame e s o selec ed plas ics a e p esen ed in Table 3. Gene ally, hese plas ics we e selec ed
based on hei a ailabili y on he ma ke , low cos s and he ac ha hey a e commonly u ilized in
he packaging indus y. PP-H ep esen s he g oup o polyole ins and is classi ied as semi c ys alline
he moplas ic polyme . I is lammable ma e ial wi h low he mal conduc i i y cu en ly used, o
example, in sewe age o d inking wa e supply sys ems. PE-HD is a he moplas ic polyme as
well. I s applica ions in he building indus y include ainwa e pipes o s o age anks, and so on.
PVC-U ep esen s inyl g oup o polyme s. I is a ha dened a ian o common PVC. PVC is widely
used in he building indus y. I s applica ions include wa e p oo ing shee s, window ames o loo ing.
Molecules 2019,24, 1398 9 o 11
Table 3. Pa ame e s o selec ed plas ics.
Ma e ial The mal Conduc i i y
[W/(m·K)]
Modulus o Elas ici y
[MPa] Densi y [g/cm3]Mel ing Poin [◦C]
PP-H 0.22 1350 0.92 90
PVC-U 0.20 3000 1.43 80
PE-HD 0.43 1000 0.95 75
The g a ime ic me hod de ined in in e na ional s anda d ISO 175:2000 [
22
] was u ilized o
se he ini ial condi ions and subsequen ly pe o m he expe imen . Conside ed condi ions o he
expe imen include:
16 weeks imme sion (long- e m es ) o plas ic samples in beake s wi h PCMs (see Figu e 8b).
Repe i i e ou -s age empe a u e cycles in an en i onmen al chambe du ing imme sion.
Indi idual ou -hou s ages we e: inc easing he empe a u e o a maximum o 40
◦
C; main aining
he empe a u e a his le el; dec easing he empe a u e o 15
◦
C and main aining he empe a u e a
his le el oo. This empe a u e in e al was applied due o he need o comple e solidi ica ion o
mel ing o PCMs in he beake s: he empe a u es we e se app ox. 10
◦
C bellow and 10
◦
C abo e peak
empe a u es o he es ed PCMs.
64 plas ic sample se s (16 se s pe one PCM; see Figu e 8a). Each sample se consis ed o h ee
indi idual plas ic pla es (100
×
10
×
1.5 mm) o minimize he impac o possible de ec i e samples on
he esul s.
Sample se s we e g adually emo ed om he PCMs in se en day pe iods o measu emen s.
Molecules 2019, 24, x FOR PEER REVIEW 9 o 11
Indi idual ou -hou s ages we e: inc easing he empe a u e o a maximum o 40 °C;
main aining he empe a u e a his le el; dec easing he empe a u e o 15 °C and main aining he
empe a u e a his le el oo. This empe a u e in e al was applied due o he need o comple e
solidi ica ion o mel ing o PCMs in he beake s: he empe a u es we e se app ox. 10 °C bellow and
10 °C abo e peak empe a u es o he es ed PCMs.
64 plas ic sample se s (16 se s pe one PCM; see Figu e 8a). Each sample se consis ed o h ee
indi idual plas ic pla es (100 × 10 × 1.5 mm) o minimize he impac o possible de ec i e samples on
he esul s.
Sample se s we e g adually emo ed om he PCMs in se en day pe iods o measu emen s.
(a) (b)
Figu e 8. Plas ic samples in he es beake s: (a) Samples be o e imme sion in PCM and he mal
cycling; (b) Samples imme sed in PCMs placed in small en i onmen al chambe du ing es ing.
Figu e 8a shows he beake s wi h all he plas ic samples (wi hou PCMs) p io o es ing. The
samples we e cleaned, isually inspec ed ( o impu i ies, damage, e c.) and ma ked be o ehand. The
igu e also shows mu ual sepa a ion o indi idual samples in he beake s. This ensu ed e en
exposu e o he whole su ace o he samples o he PCM—a pa ame e ha was no ully add essed
in he e iewed wo ks, such as [12]. Figu e 8b shows he s a o he 16-week es ing in he
en i onmen al chambe . Beake s wi h colo less o ganic PCMs a e on op and beake s wi h blue and
whi e ino ganic PCMs a e a he bo om o he chambe .
The e alua ion p ocedu e desc ibed in [22] is based on moni o ing o he mass changes in he
es ed plas ic samples. The e o e, he sample se s we e g adually emo ed om he beake s wi h
PCM o pe o m measu emen s o hei mass (a e h oughou wa e cleaning and isual check). I
should be highligh ed ha he measu emen s we e pe o med immedia ely a e he emo al om
he beake s and cleaning o a oid deg ada ion and all-o o he PCM (e.g., e apo a ion) on he
samples. The pe cen age change in mass was calcula ed o e e y sample using Equa ion (1).
Analy ical Balance 220g × 0.1mg was used o samples weigh ing. The measu ed mass o each
sample was ounded o 0.1 mg (based on he accu acy o he balance). Then he median alue o
each sample se was calcula ed and he sample co esponding wi h his alue was included in
subsequen in e p e a ion (see Sec ion 3). The median me hod was u ilized o sepa a e any ex eme
esul s caused by de ec i e samples.
∆m = [(m
2
− m
1
)/m
1
] × 100 (1)
whe e Δm is he pe cen age change in mass in %, m
2
is weigh o he sample (in g) a e emo al
om PCMs and m
1
is ini ial weigh o he sample (in mg) be o e imme sion in PCM
5. Conclusions
The pape p esen s e idence o in e ac ion be ween PCMs and plas ics po en ially usable o
he PCM encasemen . The expe imen e alua ing compa ibili y o h ee plas ics wi h wo o ganic
Figu e 8.
Plas ic samples in he es beake s: (
a
) Samples be o e imme sion in PCM and he mal cycling;
(b) Samples imme sed in PCMs placed in small en i onmen al chambe du ing es ing.
Figu e 8a shows he beake s wi h all he plas ic samples (wi hou PCMs) p io o es ing.
The samples we e cleaned, isually inspec ed ( o impu i ies, damage, e c.) and ma ked be o ehand.
The igu e also shows mu ual sepa a ion o indi idual samples in he beake s. This ensu ed e en
exposu e o he whole su ace o he samples o he PCM—a pa ame e ha was no ully add essed in
he e iewed wo ks, such as [
12
]. Figu e 8b shows he s a o he 16-week es ing in he en i onmen al
chambe . Beake s wi h colo less o ganic PCMs a e on op and beake s wi h blue and whi e ino ganic
PCMs a e a he bo om o he chambe .
The e alua ion p ocedu e desc ibed in [
22
] is based on moni o ing o he mass changes in he
es ed plas ic samples. The e o e, he sample se s we e g adually emo ed om he beake s wi h
PCM o pe o m measu emen s o hei mass (a e h oughou wa e cleaning and isual check).
I should be highligh ed ha he measu emen s we e pe o med immedia ely a e he emo al
om he beake s and cleaning o a oid deg ada ion and all-o o he PCM (e.g., e apo a ion) on
he samples. The pe cen age change in mass was calcula ed o e e y sample using Equa ion (1).