Radiation-chemically modified PP/CNT composites

e-Polymers 2014; aop

Valdis Kalkis , Ingars Reinholds * , Janis Zicans , Remo Merijs-Meri , Juris Bitenieks

and Ivans Bockovs

Radiation-chemically modified PP/CNT composites

Abstract: In this work, the authors studied the effects of

electron beam (EB)-induced changes in stress-strain char-

acteristics, heat shrinkage stresses, and structure char-

acteristics on polypropylene (PP) composites containing

bisphenol-A-dimethacrylate (BPDMA) as the radiation

sensitizer and different contents of multi-walled carbon

nanotube (CNT) filler (0 – 2 wt.%). The effect of stearic acid

(SA) as the surface modifier on the improvement of CNT

dispersion in the PP matrix was also studied. Initially, PP

blends with different contents (up to 10 wt.%) of BPDMA

were prepared to determine the effective concentration of

the sensitizer for the modification of the PP matrix. PP/

BPDMA composites and blends filled with CNTs were

irradiated up to 25 – 50 kGy of radiation doses. The prop-

erties of unirradiated compositions and those modified

by EB, were compared. Radiation-induced changes were

confirmed by gel fraction and by the changes in Fourier

transform infrared spectroscopy spectra. The results

showed an increase in Young ’ s modulus, yield strength,

and thermal-relaxation stresses for the irradiated PP/CNT

compositions grafted with 3 wt.% of BPDMA and compati-

bilized with SA.

Keywords: carbon nanotubes (CNT); electron beam;

mechanical properties; polypropylene (PP); radiation sen-

sitizer; stearic acid (SA).

DOI 10.1515/epoly-2013-0092

Received December 7 , 2013 ; accepted May 1 , 2014

1 Introduction

During the last two decades, carbon allotropic particles

like single- and multi-walled carbon nanotubes (CNTs),

graphene, etc., and their modified forms have been

increasingly investigated owing to the wide spectra of

applications in electronics, the national economy, and

materials science. The properties of the produced materi-

als can be changed significantly even at very low concen-

trations of nanofillers (1, 2) . CNTs provide many benefits

for improving the mechanical, electrical, thermal, and

other properties of polymer materials, such as thermoplas-

tic polymers like polypropylene (PP) (2 – 4) . The behavior

of such composites depends directly on the content of the

CNT nanofiller, although an increase in its concentration

affects the decrease in deformability owing to the reduced

dispersion of the filler particles in the PP matrix, which

can be enhanced by the addition of interfacial modifiers

to the PP matrix (3 – 5) .

Exposure of PP to ionizing radiation ( γ rays, acceler-

ated electrons) results in both the cross-linking and the

cleavage of macromolecules, with the latter causing the

collapse of mechanical properties (6) . The cross-linking

efficiency of irradiated PP can be enhanced by the addi-

tion of radiation sensitizers, which can improve the mate-

rial properties (7, 8) . The behavior of radiation-chemically

modified polyolefin composites with CNT fillers has been

poorly investigated. Some investigations of polyethylene

blends with CNT have shown an antioxidant effect of CNT,

which enhances the oxidative stability and increases the

strength behavior of the composite properties (9) . Castell

et al. (10) found an increase in cross-linking efficiency for

γ -irradiated PP composites with multi-walled CNTs, which

helped increase the mechanical stiffness owing to the rein-

forcement effect of the nanofiller. Such composites based

on cross-linkable polymers are widely used for manufactur-

ing heat shrinkable materials with a “ form-memory ” effect,

which is achieved by the preliminary cross-linking of the

amorphous phase of polymers by ionizing radiation. Ori-

entation by the elastic deformation at an elevated melting

temperature of the crystalline phase followed by the fixa-

tion of the oriented structure during the crystallization

*Corresponding author: Ingars Reinholds, Department of

Chemistry, University of Latvia, Kr. Valdemara Street 48, Riga,

Latvia, Tel.: +37126802448, e-mail: [email protected]

Valdis Kalkis: Department of Chemistry, University of Latvia, Kr.

Valdemara Street 48, Riga, Latvia

Janis Zicans, Remo Merijs-Meri, Juris Bitenieks and Ivans Bockovs: Institute of Polymer Materials, Riga Technical University, Azenes

Street 14/24, Riga, Latvia

Authenticated | [email protected] author's copyDownload Date | 6/4/14 12:03 AM

2 V. Kalkis et al.: Radiation-chemically modified PP/CNT composites

under cooling allows for obtaining heat shrinkable mate-

rials. Such materials based on crystallizable cross-linked

polymers allow to realize the recovery of the previous form

during the repeated heating. One of the main characteristics

of heat shrinkable materials includes the thermal-shrinkage

stresses sustained by the materials during the orientation

process, which are released by the heating (seating) process

(11) . The actuality of heat shrinkable materials based on PP

is attributed to their application in the national economy

and engineering field as corrosion and mechanical protec-

tion sleeves, couplings, etc., materials with greater poten-

tial of strength and heat resistance compared to shrinkable

materials based on polyethylene (12) . The suitability of PP/

CNT composites modified with bisphenol-A-dimethacrylate

(BPDMA) for the creation of new types of heat shrinkable

materials was studied in this work. PP blends with BPDMA

concentrations of 0 – 10 wt.% were formed to determine the

optimal ratio of PP/BPDMA. These were used as the matrix

blend to which different concentrations of CNT (0.1 – 2 wt.%)

were added. The effect of stearic acid (SA) additive on the

improvement of the mechanical, thermomechanical, and

structural properties of irradiated multiphase composites

with CNT, up to a dose of 50 kGy, was studied in this work

because of the prospective applications of CNT composites

in thermonuclear facilities.

2 Materials and methods

2.1 Initial materials

Isotactic PP; Teldene H03BPM, The National Petrochemi-

cal Industrial Co, Saudi Arabia (density 0.90 g/cm 3 ,

melt flow index 3.0 g/10 min, Vicat softening temperature

156 ° C, melting point 170 ° C) was used as the matrix. Multi-

walled CNTS (Baytubes C150P, Bayer Material Science)

were used as the nanofiller. BPDMA (Sigma-Aldrich) was

used as the radiation sensitizer and SA (Sigma-Aldrich) as

the surface agent.

2.2 Preparation of the blends and films

Firstly, PP/BPDMA blend compositions with BPDMA

contents of 0 – 10 wt.% were prepared to investigate the

optimal grafting concentration of the methacrylate sensi-

tizer, which was necessary for the cross-linking of the PP

matrix. Secondly, compositions were prepared by the addi-

tion of five concentrations (0.1, 0.5, 1, 1.5, and 2 wt.%) of

CNT to the PP blend that contained 3 wt.% concentration

of BPDMA. A portion of the PP/BPDMA blends contained

1.5 wt.% of SA as the phase modifier. All the specimens of

the PP/BPDMA, PP/CNT/BPDMA, and PP/CNT/BPDMA/SA

compositions were obtained by thermoplastic mixing on

a twin-roll mill for a total duration of 6 min at 190 ° C. The

plates, obtained by compression moulding at 190 ° C and a

pressure of 5 MPa, were cut into dog-bone specimens with

a working-zone length of 15 mm and a transverse cross

section of 0.5 × 5 mm.

2.3 Irradiation of the compositions

The plate-type specimens were irradiated with 5 MeV of

accelerated electrons produced by a linear electron accelera-

tor (ELU-4, Latvia) in air atmosphere at room temperature at

a dose rate of 1.2 MGy/h up to a radiation dose of 25 – 50 kGy.

2.4 Gel fraction

Gel fraction was expressed as the fraction of the insoluble

weight of cross-linked specimens obtained by extraction

of a soluble fraction with refluxing xylene using a Soxhlet

extractor for 48 h. The insoluble samples were then dried

at 80 ° C till constant weight. Percent gel fraction was cal-

culated as per Eq. 1:

= ⋅

i gGel fraction / 100%W W

[1]

where W i and W

g are the weight of the initial sample before

the extraction and the weight of the dried sample after the

extraction, respectively. Results were given as the average

of three parallel samples for each composition, with an

average weight of sample of 0.2 g.

2.5 Fourier transform infrared spectroscopy

Fourier transform infrared spectroscopy (FTIR) spectra

were obtained using an attenuated total reflection spec-

trometer (Thermo Nicolet 6700, Thermo Fisher Scien-

tific, Inc.). The plate samples were scanned from 4000 to

400 cm -1 at a resolution of 4 cm -1 .

2.6 Mechanical properties

Composite samples were drawn with a Tinius Olsen H1KS

tensile tester in accordance with the ASTM International

D-638 standard, using a crosshead speed of 50 mm/min.

The results presented were the mean values of six inde-

pendent measurements.


V. Kalkis et al.: Radiation-chemically modified PP/CNT composites 3

2.7 Thermal-shrinkage properties

The thermal-relaxation stresses ( σ TR

) and the residual

shrinkage stresses ( σ RTS

) were determined from the radi-

ation-modified films after the orientation of their tensile

axis by up to 100% at a temperature of 170 ° C, followed

by cooling up to room temperature. Specimens in the

form of 5 × 5 × 2-mm strips were gradually heated and

cooled under isometric conditions. Control of the heat-

ing-cooling mode was carried out on a stand equipped

with a heating chamber. The following parameters were

used: heating range, 25 – 200 ° C; cooling range, 200 – 25 ° C;

and heating and cooling rate, 7 ° C/min. The changes in

stress values were determined by a force sensor (MICRO

SWITCH Force Sensor FSG-15N1A, Honeywell Sensing

and Control, USA) with a sensitivity of 0.01 N.

3 Results and discussion

3.1 Mechanical properties of the PP/BPDMA compositions

The effect of the concentration of the BPDMA cross-linking

agent on the changes in Young ’ s modulus ( E ) and on the

stress-strain characteristics of unirradiated and radiation-

modified PP shows the changes in the PP matrix, with an

increase in BPDMA content and a change in the radiation

dose from 0 to 50 kGy ( Figure 1 ). The value of E and the

yield strength decreased significantly for the unirradi-

ated compositions with an increase in BPDMA content,

as shown in Figure 1 A and B, respectively. This may be

explained by the macromolecular branching due to the

interaction between BPDMA and PP, and to the formation

of PP-BPDMA side chains.

The stress-strain curves for the unirradiated PP/

BPDMA composites had a typical elastic-plastic transition

similar to that of neat PP, with a change from yielding to

the plastic deformation with a strain hardening up to the

fracture, while the radiation induced a decrease in chain

mobility, which affected the decrease in strain hardening

at 25 kGy and a complete disappearance at 50 kGy fol-

lowed by a substantial reduction in the tensile strength

and a reduction of the elongation at break. This may be

attributed to the decrease in chain mobility caused by the

radiation-induced grafting of BPDMA to the PP chains

and to the formation of cross-linked sites in the amor-

phous phase, which explains the increase in the Young ’ s

modulus. It should be noted that the compositions became

brittle with an increase in BPDMA content > 3 wt.% owing

to the radiation-induced destruction of possible side

160015001400130012001100

Youn

g’s

mod

ulus

(M

Pa)

Yie

ld s

tren

gth

(MP

a)

1000900800700600

45 800

700

600

500

400

300

200

100

0

40

35

30

25

Tens

ile s

tren

gth

(MP

a)

Elo

ngat

ion

at b

reak

(%

)

20

15

450 kGy 25 kGy 50 kGy 0 kGy 25 kGy 50 kGy

0 kGy 25 kGy 50 kGy 0 kGy 25 kGy 50 kGy

40

35

30

25

20

15

10

5

0

0 2 4 6 8 10BPDMA (wt.%)

0 2 4 6 8 10BPDMA (wt.%)

0 2 4 6 8 10BPDMA (wt.%)

0

C D

BA

2 4 6 8 10BPDMA (wt.%)

Figure 1 Young ’ s modulus (A), yield strength (B), tensile strength (C), and deformation at break (D) for the PP/BPDMA composites, with a

dependency on sensitizer concentration and radiation absorbed dose.



30

25

20

15

10

5

0

Gel

frac

tion

(%)

25 kGy 50 kGy

0 2 4 6 8 10BPDMA (wt.%)

Figure 2 Gel fraction with a dependency on BPDMA concentration

and radiation dose.

Abs

orba

nce

Abs

orba

nce

PP/BPDMA 0%A B

PP/BPDMA 1%

PP/BPDMA 10%PP/BPDMA 5%PP/BPDMA 3%

PP/BPDMA 0%PP/BPDMA 1%

PP/BPDMA 10%PP/BPDMA 5%PP/BPDMA 3%

1400 1450 1500 1550 1600 1650 1700 1800

ν (cm-1)

1750 1400 1450 1500 1550 1600 1650 1700 1800

ν (cm-1)

1750

Figure 3 FTIR spectra of (A) unirradiated and (B) irradiated PP/BPDMA compositions up to a dose of 50 kGy .

products of the BPDMA formed during the thermoplastic

mixing.

3.2 Gel fraction of the PP/BPDMA compositions

The average gel fractions, which were dependent on the

irradiation dose of the PP/BPDMA compositions, are

plotted in Figure 2 . The unirradiated compositions did

not show any gel fraction as the latter was expected to

form during the radiation-induced cross-linking of PP

macromolecules through the bridge groups of grafted

BPDMA (7) .

A slight increase in gel content was considered up

to 25 – 30% for the radiation-modified compositions with

an increase in BPDMA content of up to 3 wt.%. This may

indicate the formation of cross-linked moieties in the

amorphous phase of PP in the presence of radiation-

grafted counterparts of BPDMA acrylate groups as the

sites of cross-linking. This is confirmed by the increase

in the Young ’ s modulus and in the tensile strength.

The decrease in gel fraction at 50 kGy may indicate a

destruction in the interfacial boundary of the PP crystal-

line-amorphous phases.

3.3 FTIR spectra of PP/BPDMA compositions

The FTIR spectra of irradiated composites indicate the

radiation-induced grafting of the BPDMA on the PP

matrix, with an increase in BPDMA content of up to 3

wt.% as shown by the increase in the unsaturated C = C

bounds at 1500 and 1616 cm -1 , and by the changes in the

methacrylate C = O bounds at 1730 cm -1 (8) . The further

increase in BPDMA content affected the decrease in the

C = C bounds, which may be attributed to the side reactions

of the cross-linking agent such as the thermally induced

self-polymerization of BPDMA during the blending, which

explains the changes in the mechanical properties with a

BPDMA content of > 3 wt.% ( Figure 3 ).

3.4 Mechanical properties of PP/CNT/BPDMA and PP/CNT/BPDMA/SA compositions

The changes in the mechanical properties as a function of

CNT content and radiation dose, as shown in Figure 4 A,

indicate a similar increase in the Young ’ s modulus (E)

for the unirradiated and the radiation-modified PP/CNT/

BPDMA/SA composites by about 23%, with an increase

in CNT content from 0 to 2 wt.%. A small increase, by

about 5 – 7%, in the Young ’ s modulus was observed with

the increase in the irradiation dose of up to 50 Gy owing

to the reinforcement effect of CNT in the interfacial amor-

phous-crystalline phase of PP. A notable effect of SA on

the increase in adhesion between the CNT nanofiller

and the PP matrix can be observed by comparing the

changes in E with those in the PP/CNT/BPDMA compos-

ites. A sharp decrease in the modulus was observed for



Youn

g’s

mod

ulus

(M

Pa)

A B

C D

2200210020001900180017001600150014001300120011001000

40 1000

30

32

34

36

38

40

42

100

10

1

35

30

25

20

10

15

CNT (wt.%)0 0.5 1.0 2.01.5

CNT (wt.%)0 0.5 1.0 2.01.5

CNT (wt.%)0 0.5 1.0 2.01.5

CNT (wt.%)

0 0.5 1.0 2.01.5

0 kGyPP/CNT/BPDMAPP/CNT/BPDMA/SA

25 kGy 50 kGy0 kGy 25 kGy 50 kGy


25 kGy 50 kGy0 kGy 25 kGy 50 kGy


25 kGy50 kGy0 kGy 25 kGy 50 kGy 0 kGyPP/CNT/BPDMA

PP/CNT/BPDMA/SA25 kGy 50 kGy

0 kGy 25 kGy 50 kGy

Yie

ld s

tren

gth

(MP

a)

Tens

ile s

tren

gth

(MP

a)

Elo

ngat

ion

at b

reak

(%

)

Figure 4 Young ’ s modulus (A), yield strength (B), tensile strength (C), and deformation at break (D), with a dependency on the CNT content

of unirradiated and irradiated PP/CNT/BPDMA and PP/CNT/BPDMA/SA blends up to a dose of 50 kGy.

the compositions with no SA modifier, as shown by the

increase in CNT content > 0.5 wt.% due to the rapid forma-

tion of CNT agglomerates. It can be said that SA partially

acts as a surfactant of CNT particles. This observation is

supported by the increase in the yield strength by 11% with

the increase in CNT content of up to 1 wt.% for composi-

tions containing SA. An increase of only 3% was observed

for the unmodified PP compositions with an increase in

CNT content of up to 1 wt.%.

The further increase in CNT content affected the

reduction of the ductility for both compositions contain-

ing SA and those with no modifier owing to the decrease

in the yield strength, which resulted in a significant reduc-

tion of the elongation at break at a CNT content of > 0.5

wt.%. This is attributed to the presence of nanotube aggre-

gates, which act as stress concentrators, as shown by the

increase in tensile strength due to the collapse of the inter-

facial adhesion between the CNT and the PP matrix at a

CNT content > 0.5 – 1 wt.%.

The stress-strain curves for the irradiated composites

show an immediate rupture after the formation of a neck.

It is shown by the changes in the tensile strength and elon-

gation at break in Figure 4 B and C, respectively. This may

be attributed to the ejection of CNT clusters near the phase

boundary of the PP crystallites, which affected the fragil-

ity of the composites. A slight increase in yield strength

by about 9% was noted with the increase in CNT content

and irradiation dose. Moreover, the increase in the yield

strength with irradiation dose was less pronounced for

compositions with increased content of CNT compared

to unirradiated specimens. For example, for composi-

tions with CNT content of 1 wt.%, the increase in yield

strength was 1.6-fold lower than for compositions with no

nanofillers.

3.5 Gel fraction and thermal-shrinkage behavior of PP/CNT/BPDMA/SA compositions

The average values of the gel fraction calculated from

three parallel measurements for irradiated PP/CNT com-

positions showed a 1.3- to 1.7-fold increase in gel fraction

at doses of 50 and 25 kGy with an increase in CNT content

of up to 1 wt.% compared to compositions with no CNT

( Figure 5 A).

This may be explained by the reinforcing effect of

CNT particles in the internal layers of the irradiation



cross-linked macromolecules in the amorphous phase

of PP branched through the BPDMA groups (6) . A sharp

decrease in gel fraction indicates a disturbance of the

agglomerates on the formation of cross-linked sites in the

interfacial layer of the amorphous phase of PP and the

destruction of the crystallites by the radiation treatment.

Figure 5 B shows the temperature dependence of the

internal stresses for orientated of their tensile axis by up

to 100% composites with CNT content of 0 – 2 wt.%.

It should be noted that the changes in the formation

of internal stress in the isometric heating-cooling mode

confirm the changes in the mechanical properties, with

changes in the gel fraction for the PP/CNT blend at a dose

of 25 kGy.

In the case of irradiated cross-linkable polymer, the

formation of stresses occurred above the melting tempera-

ture of the crystalline phase, whereas the cross-linking

occurred in the amorphous phase, especially at relatively

low doses of radiation (11) . It has been determined that

the values of the internal stresses rose at relatively low

temperatures for the PP/BPDMA composites with CNT

compared to the melting temperature for pristine PP. This

shows the effect of structure change due to the grafted

groups of the BPDMA. It is also known that CNT, like any

other nanofiller, accumulates primarily in the amorphous

phase, which is partially shown by the change in the

mechanical properties and by the increase in the thermal-

relaxation stresses from 0.25 to 0.37 MPa, with an increase

in CNT content from 0 to 1 wt.%. The latter increase

in CNT content of up to 2 wt.% affected the decrease in

the thermal-relaxation stresses. This coincided with the

ductile behavior in the blends with the increase in the

CNT content due to the increase in agglomerate concen-

tration. The further increase in residual stresses during

the isometric cooling shows the effect of CNT on the rear-

rangement of the crystalline phase, affecting the increase

in residual stresses with the increase in CNT content.

4 Conclusions

It has been determined that exposure of PP to electron

beam in the presence of BPDMA, as the radiation sensi-

tizer, of up to 3 wt.% improved the radiation-induced

cross-linking of the PP matrix. This is shown by the

increase in the mechanical properties, gel fraction, and

unsaturated sites detected by FTIR.

Modification of the PP matrix with SA in the presence

of BPDMA enhanced the adhesion of CNT to the PP matrix

at relatively low ( < 1 wt.%) CNT filler concentrations; the

formation of CNT agglomerates with a CNT content > 0.5

wt.% significantly affected the reduction of the elongation

at break.

For the irradiated composites, the mechanical stiff-

ness increased with the increase in CNT content in the

PP matrix and with the increase in radiation dose. Dis-

turbance in the crystalline phase of PP due to the radia-

tion-induced destruction of crystallites in the interfacial

layer of the amorphous phase of the PP affected the

decrease in the elongation at break and also the decrease

in the gel fraction with the increase in radiation dose up

to 50 kGy.

The radiation-chemical modification of PP/CNT com-

posites containing 3 wt.% of BPDMA as the radiation sen-

sitizer allowed for obtaining materials with relatively high

characteristics of the thermal-shrinkage properties: the

thermal-relaxation stresses ( σ TR

= 0.25 – 0.37 MPa), which

A B40 2.4 0% CNT

2% CNT1% CNT0.5% CNT2.2

2.0

σ RT

S (

MP

a)

σ TR (

MP

a)

1.8

0.8

1.61.41.2

0.60.40.2

025 75 125 175 225

T (°C)

1.0

2.4

2.2

2.0

1.8

0.8

1.6Isometric cooling

Isometric heating

1.4

1.2

0.6

0.4

0.2

0

1.0

35

30

25

20

10

15

5

0

CNT (wt.%)

0 0.5 1.0

25 kGy50 kGy

2.01.5

Gel

frac

tion

(%)

Figure 5 Gel fraction with a dependency on (A) the CNT content and (B) the kinetic curves of the formation of internal stress [ther-

mal-relaxation stresses ( σ TR

) and shrinkage stresses ( σ RTS

)] of irradiated compositions, up to a dose of 25 kGy of previously oriented

( tensile strain 100% ) PP/CNT blends with different contents of CNT (0, 0.5, 1, and 2 wt.%).



are expressed as the stresses of the plateau formed during

the isometric heating, and the residual shrinkage stresses

( σ RTS

= 1.6 – 2.2 MPa), which are formed during the isomet-

ric cooling. The results of this investigation have shown

a notable effect of irradiation by electron beam on the

change in PP/CNT composite properties. Further investiga-

tions are planned on improving the technological method

for the dispersion of CNT in the PP matrix.

References 1. Kuilla T, Bhadra S, Yao, D, Kim NH, Bose S, Lee JH. Recent

advances in graphene based polymer composites. Prog Polym

Sci. 2010;35(11):1350 – 75.

2. Bikiaris D. Microstructure and properties of polypropylene/car-

bon nanotube nanocomposites. Materials 2010;3(4):2884 – 946;

Available from: http://www.mdpi.com/1996-1944/3/4/2884

(accessed 15 May 2014). doi: 10.3390/ma3042884.

3. Zamani MM, Fereidoon A, Sabet A. Multi-walled carbon

nanotube-filled polypropylene nanocomposites: high veloc-

ity impact response and mechanical properties. Iran Polym J.

2012;21(12):887 – 94.

4. Moniruzzaman M, Winey KI. Polymer nanocomposites containing

carbon nanotubes. Polym Macromol. 2006;39(16):5194 – 205.

5. Gonzalez L, Lafleur P, Lozano T, Morales AB, Rodriguez F,

Sanchez S. Mechanical and thermal properties of polypropyl-

ene/montmorillonite nanocomposites using stearic acid as

both an interface and a clay surface modifier. Polym Compos.

2014;35(1):1 – 9.

6. Abiona AA, Osinkolu AG. Gamma-irradiation induced property

modification of polypropylene. Int J Phys Sci. 2010;5(7):960 – 7.

7. Ram í rez-Jim é nez A, Alvarez-Lorenzo C, Concheiro A, Bucio E.

Radiation-grafting of 2-hydroxyethylmethacrylate and oligo

(ethylene glycol) methyl ether methacrylate onto polypropylene

films by one step method. Radiat Phys Chem. 2012;81(1):27 – 32.

8. Shukushima S, Hayami H, Ito T, Nishimoto S. Modification

of radiation cross-linked polypropylene. Radiat Phys Chem.

2001;60(4 – 5):489 – 93.

9. Rama Sreekanth PS, Naresh Kumar N, Kanagaraj S. Improving

post irradiation stability of high density polyethylene by multi

walled carbon nanotubes. Comp Sci Tech. 2012;72(3):390 – 6.

10. Castell P, Medel FJ, Martinez MT, Pu é rtolas JA. Influence of

gamma irradiation on carbon nanotube-reinforced polypropyl-

ene. J Nanosci Nanotechnol. 2009;9(10):6055 – 63.

11. Voit W, Ware T, Gall K. Radiation crosslinked shape-memory

polymers. Polymer. 2010;51(15):3551 – 9.

12. Jackson P, Heydrich MP. Crosslinked heat shrinkable polypropyl-

ene compositions. U.S. Patent 6569915B1, 2003.


e-Polymers 2014 | Volume xx | Issue x 1

Graphical abstract

Valdis Kalkis, Ingars

Reinholds, Janis Zicans, Remo

Merijs-Meri, Juris Bitenieks and

Ivans Bockovs

Radiation-chemically modified PP/CNT composites

DOI 10.1515/epoly-2013-0092

e-Polymers 2014; xx(x): xxx–xxx

Full length article: Electron beam-

induced grafting of the cross-

linking agent BPDMA promotes

an increase in the mechanical and

thermal-shrinkage properties of

polypropylene/carbon nanotube

composites in the presence of stearic

acid as the interfacial modifier.

Keywords: carbon nanotubes (CNT);

electron beam; mechanical proper-

ties; polypropylene (PP); radiation

sensitizer; stearic acid (SA).

2.4

2.2

2.0

Res

idua

l shr

inka

ge s

tres

s (M

Pa)

The

rmo-

shrin

kage

str

ess

(MP

a)

1.8

0.8

1.6

1.4

1.2

0.6

0.4

0.2

025 75 125 175 225

T (°C)

1.0

2.4

2.2

2.0

1.8

0.8

1.6Isometriccooling

Isometricheating

1.4

1.2

0.6

0.4

0.2

0

1.0

PP/BPDMA/SA/CNT 0%

PP/BPDMA/SA/CNT 0.5%

PP/BPDMA/SA/CNT 1.0%


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