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Arab Journal of Nuclear Science and Applications, 47(1), (1-13) 2014

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Coating Characteristics of UV Curable Epoxy Acrylate Oligomer Modified

with Acrylated Sunflower Oil

Issa M. Mousaa, Sayeda M. Ibrahim, and H. Radi

Department of Radiation Chemistry, National Center for Radiation Research and Technology,

P.O.BOX 29, Naser City, Cairo, Egypt.

Received: 4/4/2013 Accepted: 5/8/2013

ABSTRACT

In this study epoxy acrylate oligomer (EA) was toughened by epoxidized

sunflower oil acrylate (EPOSA) and cured under UV irradiation in the presence of

p-methoxy acetophenone as photointiator. EPOSA was prepared via acrylation

process. Acid value, FTIR, oxirane oxygen content and viscosity were carried out to

confirm the occurrence the acrylation process. Different formulations of EA and

EPOSA were prepared and different characterizations such as FTIR,

thermogravimetric analysis (TGA), gel fraction and swelling properties were made

for cured coating films. The mechanical and chemical tests such as pencil hardness,

adhesion, bending, gloss, steam and stain resistance were measured for cured

surface. FTIR studies indicated that the density of acrylate functionality and degree

of curing decreased with increasing the concentration of EPOSA. The elasticity,

gloss and chemical resistance properties were improved by increasing the

concentration of EPOSA.

Key Words: UV Irradiation / Epoxy Acrylate Oligomer / Epoxidized Sunflower Oil Acrylate /

Photoinititor / Adhesion / Pencil hardness.

INTRODUCTION

UV curing process, which converts a reactive monomer into a solid through photo-

polymerization and/or crosslinking reactions induced by UV radiation at room temperature (1), has

attractive advantages such as rapid curing rate, solvent free, low energy requirement, and excellent

properties of products (2). The UV-curable coatings consist of oligomer, monomer and photoinitiator,

so the coating film properties, such as hardness, abrasive resistance, flexibility and weatherability,

mainly depend on the oligomer structure and its concentration in the formulation. During last decades,

a great deal of attentions have been paid to UV curing applications in preparing protective coatings (3),

nanoimprint lithography (4),dental restoratives and adhesives (5), encapsulants and packaging of organic

light-emitting devices in electronic industry (6).

Epoxy acrylate resin is the classic resin for UV curing coatings because of its good integrated

performance such as outstanding adhesion, non-yellowing, hardness, mechanical properties and

chemical resistance (7,8), and thus wide applications. Epoxy resins are widely used in several

applications: adhesives, coatings, castings, electric laminates, encapsulation of semiconductor devices,

matrix material for composites, structural components (9-14) and cryogenic engineering (15-17). However,

due to their high cross-link density they are inherently brittle, which limits their applicability. Many

efforts have been made to modify epoxy acrylate resins or their formulations for improving the

toughness of cured films. To increase their toughness, different modifiers have been added like rubber,

flexible components into epoxy networks in an appropriate ratio (18-20). Aliphatic urethane acrylate or

polyester acrylates are low viscosity oligomers that provide soft and flexible coating with low

shrinkage, high toughness and excellent weatherability (21). Epoxy acrylate (EA) oligomer has high

viscosity at ambient temperature and diluted by the addition of low viscous multifunctional reactive

monomers (22). However, these reactive diluents showed higher volatile content compared to oligomers


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and create shrinkage and brittleness in the coating at higher content of reactive diluents, resulting in

reducing adhesion and deterioration of gloss and aesthetic look of the coating (23-25). On the other hand,

epoxidized vegetable oils show excellent promise as inexpensive, renewable materials for industrial

applications (26). Epoxidized sunflower oil acrylate (EPOSA) has a low viscosity oligomer with low

volatile content and unique coating properties can be used to reduce the viscosity of EA resin as well

as to regulate or even improve certain properties of EA coating by optimized combination of both the

oligomers. In this study the EPOSA was prepared via acrylation process by reacting epoxidized

sunflower oil and acrylic acid. The prepared EPOSA was added in different concentrations in EA

formulations and cured under different times of UV radiation.

EXPERIMENTAL

Materials:

EBECRYL 604 (Epoxy acrylate oligomer (EA) consisting of 80% of bisphenol A epoxy

diacrylate diluted with 20% of 1,6-hexanediol diacrylate) was obtained from Cytec Surface

Specialeties (Drogenbos, Belgium). Epoxidized sunflower oil having oxirane oxygen content 6 % was

supplied by Paint and Chemical Industry (PACHIN), Egypt. Hydroquinone, triethylamine and acrylic

acid were obtained from Merck, Germany. p-methoxy acetophenone was supplied by Ciba Chemicals,

Switzerland and used as a photoinitiator to initiate photochemical reaction during UV radiation

process. The plywood, tin metal plate and glass samples were obtained from the local market. All

chemicals were used as received without further purification

Synthesis of epoxidized sunflower oil acrylate (EPOSA) (27):

The acrylation of epoxidized sunflower oil was carried out by placing a mixture containing 0.2

mol. epoxidized sunflower oil, 0.5% hydroquinone as inhibitor and 1.0% triethylamine (based on the

weight of reactants) as a catalyst in a round bottom three-neck flask (500 ml). The flask is equipped

with a mechanical stirrer, a reflux condenser and a separating funnel. While stirring the mixture, 0.8

mol. acrylic acid was introduced to the mixture through the separating funnel. After the addition of

acrylic acid, the mixture was then heated up to 110oC. The progress of acrylation reaction was

followed by measuring the acid value of the mixture. The product was washed with 1% NaH2PO4 and

1% NaCl to remove excess acrylic acid.

Determination of acid value:

The acid value was determined according to ASTM D 1639-90 as follows:

Acid Value = (N x V x 56.1) / W

Where N, is the normality of KOH, V, is the volume of KOH and W, is the weight of the sample.

Determination of oxirane oxygen content:

The oxirane oxygen content was measured by HBr in acetic acid using crystal violet as indicator (28). The oxirane oxygen content (%) was determined according to the following equation:

Oxirane oxygen content (%) = [(L x N x 1.6) / W] x100

Where L, is the volume of HBr solution, N, is the normality of HBr solution and W, is the weight of

the sample.

UV curing of formulations:

Epoxy acrylate oligomer (EA) and acrylated sunflower oil (EPOSA) were mixed at different

ratios with continuous stirring to get homogeneous mixtures to be used as formulations for coating.

Different coating formulation samples (S0-S5) were prepared by mixing 10, 20, 30, 40, 50 phr of

EPOSA with constant EA oligomer ratio of 100 phr and constant concentration of photoinitiator of


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5%, respectively. These formulations were surface coated on glass, tin metal and wood substrates by

using film applicator with thickness of ~100 μm. The coated samples were irradiated using a standard

UV lamp Type EMITA VP-60 (made in Poland), 180W mercury, 220V, 50 Hz and monochromatic

filter (λ =320 nm) was used to provide the required irradiation wavelength. In this study, the UV

irradiation was carried out, in which the sample was placed at a constant distance (10 cm) from the

lamp for various time intervals at a dose rate of 23.7 KJ/m2.

Fourier Transform infrared spectroscopy (FT-IR):

IR spectra of cured films were measured by ATI Mattson, Genesis series, England. FTIR spectra

were recorded in the range from 400 to 4000 cm−1 with a resolution of 4 cm−1 and averaged over 25

scans.

Gel fraction and swelling measurements:

The cured films (2 cm × 2 cm) were extracted with acetone for 10 h, and dried at 30oC for 72 h

till a constant weight was obtained. The gel fraction was calculated according to the following

equation:

Gel fraction (%) = (W1/Wo) x 100

Where Wo is the initial mass of the film before washing and W1 is the final mass of the films.

The swelling ratio was determined by immersing dry weight of cured films with different

EPOSA concentrations (W1) in acetone for 48h at room temperature. The samples were removed and

blotted on filter paper to remove the excess acetone on the surface and weighed (W2). The swilling

ratio was calculated according to following equation. Swelling ratio = (W2 –W1) / W2

Thermogravimetric analysis (TGA):

The TGA thermograms were performed on a Shimadzu–50 instrument (Kyoto, Japan) at a

heating rate of 10ºC/min under nitrogen flow (20 ml/min) starting from room temperature up to 500ºC.

The primary TGA thermograms were used to determine the kinetic parameters of the thermal

decomposition reaction.

Viscosity measurements:

The viscosity was measured by using Programmable Rheometer DV III RV. The viscosity rang

is from 5 Cp to 8,000 Cp depending upon the viscometer and SC4 spindle utilized. In the present work,

the viscosity of formulations was measured at room temperature and at 50oC.

Performance tests of cured surfaces:

The different surfaces coated with cured formulations were tested for different end performance

properties according to the standard test methods. Film adhesion (ASTM D 3359-97), gloss at 60o

angle (ASTM: D 523-99), pencil hardness (ASTM D 3363-00), Bending test (ASTM D 522-93a),

alkali resistance (ASTM D 1647-89), acid resistance (ASTM B 287-74), stain/chemical resistance

conducted for seven different staining agents (EN 438-2: 1991) and steam resistance (EN 438-2:

1991).

RESULTS AND DISCUSSION

Synthesis of epoxidized sunflower oil acrylate:

In the acrylation of epoxidized sunflower oil (EPOS) process (29), the epoxy group of EPOS will

react with acrylic acid to produce epoxidized sunflower oil acrylate (EPOSA) as shown in Fig. (1). the

acrylated epoxidized sunflower oil molecules still contain double bond and hydroxyl groups. Thus, the

acrylated oil can be polymerized via double bonds. This means that, adhesion and wetting with

pigments of fillers will be improved due to the presence of the hydroxyl groups. The blends of EPOS


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and triethylamine were heated to 80oC with moderate continuous stirring. When the temperature in the

reaction flask was steady at 80oC, the calculated amount of acrylic acid was introduced to the oil blend

at a very slow rate. After complete addition of acrylic acid, the temperature was raised to 110oC and

then maintained until the acid value of the EPOSA reached 10 mg KOH/gm resin.

The produced EPOSA was characterized chemically by measuring oxirane oxygen content, acid

value, viscosity and IR spectroscopy. Table (1) shows the progress of acrylation process according to

the determined acid value. It is clear that the initial acid value of the starting mixture sample after

adding acrylic acid is 110 mg KOH/gm resin. After acrylation process, the acid value of EPOSA was

10 mg KOH/gm resin after 45h. Therefore, the acid values of epoxidized acrylated sunflower oil

decreased by a value of about 100 mg KOH /gm resin due to the acrylation of sunflower oil and free

acrylic acid content was reduced in the mixture resulting in a subsequent increase of acrylate groups in

the backbone of triglyceride molecules. The analytical data of EPOS, EPOSA and washed EPOSA are

given in Table (2). It can be seen that the oxirane oxygen content of EPOSA and washed EPOSA are

0.12 % compared with 6% for the starting material of EPOS. This means that almost all oxirane

oxygen has participated in the reaction to yield EPOSA. It can be also seen that the viscosity was

greatly increased after acrylation. This may be attributed to the increase in molecular weigh, high

branching and/or hydrogen bonding.

CH2

CH

CH2

O-C-CH2 -CH CH

O

O-C-CH2 -CH CH

OO-C-CH2 -CH CH

O O

O

O

+ CH2=CH-COOH

CH2

CH

CH2

O-C-CH2 -CH

CH

O-C-CH2 -CH CH

O-C-CH2 -CH

CH

O

O

O

HO

OH

O

C-CH=CH2

O

OH

C-CH=CH2

O

O C-CH=CH2

O

Epoxidized sunflower oil (EPOS) Acrylic acid

Epoxidixed sunflower oil acrylate (EPOSA)

Triethyl amine as catalyst

O

Fig. (1): Acrylation reactions of epoxidized sunflower oil (EPOS).


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Table (1): Acid value of EPOSA at different time intervals.

Time (h) Acid value

(mg KOH/gm resin)

Before reaction 110

5 100

10 85

15 72

20 55

25 32

30 25

35 15

40 10

45 10

After washing 1.5

Table (2): Analytical data of EPOS, EPOSA and washed EPOSA

Properties EPOS EPOSA EPOSA (washed)

Oxirane oxygen content (% per mole) 6 0.12 0.12

Acid value (mg KOH/gm resin) 1 1 0 1.5

Viscosity (cps at 50oC) 115 7200 7200

Also, the acrylation reaction was detected by the IR-spectra for EPOS and acrylated sunflower

oil (EPOSA) as shown in Fig. (2). The EPOS molecule can be characterized by the presence epoxy

group at 823 cm-1 and a weak band of hydroxyl groups at 3477 cm-1. After acrylation process the peak

of the epoxy groups was disappeared and a new band appeared at 1622 cm-1 which may be attributed

to the acrylate group (CH2=CH-COO-), while the other broad band appeared at 3480 cm-1 may be

attributed to (-OH) group (30). This means that almost all the epoxy groups were consumed during the

acrylation process.

Wavenumbers cm-1

1000200030004000

Tra

nsm

itta

nce

(a)

(b)

3480 cm-1

1622 cm-1

823 cm-1

Fig. (2): IR spectra of: (a) epoxidized sunflower oil and (b) epoxidized sunflower oil acrylate.


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Characterization of UV-cured formulations:

FT-IR analysis

The FTIR spectra of cured and uncured EA without EPOSA are shown in Fig. (3). This figure

showed a characteristic peak of unsaturated double bond of acrylate group of uncured EA oligomer

which appeared at 1625 cm-1 and 815 cm-1 . After UV curing of EA, the characteristic peak of acrylate

group was disappeared indicating the occurrence of crosslinking process. The IR spectra of uncured

EA oligomer and different concentrations of EPOSA with EA are shown in Fig. (4). It is clear that the

characteristic peaks of acrylate double bonds at 1625 cm-1 and that at 815 cm-1 are completely

disappeared after UV curing. The percentage conversion of double bonds in the UV cured coating was

found to be more than 99%, which suggest a very high degree of curing of formulations via UV curing

process resulting in formation of high performance coatings. The estimation of the double bond

conversion was made by comparing the reduction in the intensity of the C=C band at 1625 cm-1

relative to the carbonyl group peak at 1720 cm-1, which was assumed to remain constant during the

curing reaction.

1610

Blank (uncured)

500100015002000250030003500

Blank (cured)

Tra

nsim

att

an

ce

1625 cm-1 815 cm-1

Wavenumber cm-1

Fig. (3): The FTIR spectra of cured and uncured epoxy acrylate oligomers


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30 phr

1610 cm-1Blank (uncured)

Wavenumber cm-1500100015002000250030003500

10 phr

20phr

40 phr

50- phr

30phr

Tra

nsi

ma

tta

nce

815 cm-1

1625 cm-1

Fig. (4): FTIR spectra of uncured and cured EA oligomers prepared with different concentrations of

EPOSA.

Gel fraction and swelling measurements:

Gel fraction is a measure of the extent of crosslinking of the UV-cured coatings, which in turn

determines the final properties of the coatings. As shown in Fig. (5), the gel fraction decreases by

increasing the concentrations of EPOSA from 10 phr to 30 phr. At higher ratios than 30 phr of

EPOSA, the gel fraction decreased slightly and finally reached saturation. The EPOSA based on

sunflower oil gave soft and elastic films and contains low density of acrylate double bond compared

with EA oligomer. Thus, the incorporation of EPOSA to EA coatings leads to a low crosslinking

extent reflected from the reduced gel fraction. This behavior would consequently increases the

flexibility of the coatings, leading to an improvement in some physical and mechanical properties such

as bending and impact tests.

The swelling ratio measurements of coating formulations are given in Fig. (5). It is expected that

the swelling ratio is indirectly reflects the extent of crosslinking of the coating. It can be observed that

the swelling ratio of cured films increased with increasing EPOSA concentrations in the coating

composition up to 30 phr. The swelling ratio at higher concentration of EPOSA causes a slight

increase which again supports the gel fraction results. Lower gel fraction reflects lower crosslinking

extent and so low hardness of the coating consequently leads to higher swelling ratio in swelling

medium.


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EPOSA concn. (phr)

0 10 20 30 40 50 60

Gel

fra

ctio

n (

%)

96.0

96.5

97.0

97.5

98.0

98.5

99.0

Sw

ellin

g r

atio

1.08

1.10

1.12

1.14

1.16

1.18

1.20

1.22

Gel fraction (%)

Swelling ratio

Fig. (5): Effect of EPOSA concentrations on gel fraction and swelling ratio of EA coatings.

Thermogravimetric analysis (TGA):

The thermogravimetric analysis (TGA) is the preferred technique for rapid evaluation of the

thermal stability of different materials, and also indicates the decomposition of polymers at various

temperatures. The effect of EPOSA concentration on the thermal stability of the UV cured coatings

was evaluated by TGA. Fig. (6) shows the TGA thermograms of the cured EA coatings for S0

(without EPOSA) and S5 (50 phr EPOSA) and the data collected are shown in Table (3). It can be

seen that the cured EA coating was stable up to ~300oC. The TGA thermogram of UV cured coatings

showed weight loss in two stages; first is major weight loss in the temperature range of 300-500oC,

which is due to the thermal decomposition of organic coating. The second stage of weight loss within

the temperature range 500-600oC, which is referred to the oxidation of the residual formed from the

thermal decomposition of coating. The data in Table (3) shows the temperatures at which different

weight loses (30%, 40%, 60%, and 70%) of the coatings containing different concentrations of

EPOSA occurred. TGA results showed that the increase in EPOSA concentration in EA coating

decreased the thermal stability of EA coating due to the decrease in crosslink density of cured EA

coatings.

The thermal stability was confirmed by plotting the rate of thermal decomposition reaction

(dw/dt) as a function of heating temperature for EA coatings for S0 (without EPOSA) and S5 (50 phr

EPOSA) as shown in Fig. (6). From Table (3) and Fig. (6), it can be seen that the temperatures of the

maximum rate of reaction (Tmax), taken from the TGA thermogram, was shifted to lower temperature

by ~12oC with increasing the EPOSA concentration indicating lower thermal stability at high

concentration of EPOSA.


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100 200 300 400 500 600

we

igh

t re

main

ing

(%

)

0

20

40

60

80

100S0

S5

Temperature (oC)

100 200 300 400 500 600

Rate

of

reacti

on

(m

g/m

in)

0

2

4

6

8

Fig. (6): TGA thermograms and the corresponding rate of thermal decomposition reaction of UV

cured EA coatings for S0 (without EPOSA) and S5 (50 phr of EPOSA).

Table (3): Temperatures at which different weight loss (%) have occurred and temperatures of the

maximum rate of reaction (tmax) of different formulations cured by UV irradiation at 20

min.

Coating

formulations

Decomposition temperatures at different weight loss (%) Tmax

30% 40% 60% 70%

S0 434 461 486 540 460

S1 413 441 476 515 458

S2 411 436 471 496 455

S3 409 433 468 491 453

S4 406 426 463 486 451

S5 401 421 458 478 448


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Surface coating applications:

In this section, the different formulations were coated on glass, tin metal and wood substrates

and the coated substrates were exposed to UV irradiation.

Tacky properties of surfaces:

In order to select the suitable irradiation time to get non-tacky coating, different formulations

were prepared by blending EA and EPOSA in the presence 5% p-methoxy acetophenone as initiator

and exposed to different UV irradiation times (5 to 20 min). The coating formulations and UV curing

behaviors of different formulations are given in Table (4). It can be seen that at irradiation time of 5

and 10 min., all formulations gave tacky surface. On the other hand, the formulations irradiated at 15

and 20 min. gave non-tacky cured films, except the formulation S5 irradiated at 15 min gave tacky

surface. Thus it may be concluded that, irradiation at 20 min is selected as the best irradiation time to

cure all formulations.

Table (4): Adhesion characters of different formulations, prepared by UV-radiation at time intervals.

Coating

formulations

EPOSA

(phr)

Irradiation time (min)

5 10 15 20

S0 0 1 2 3 3

S1 10 1 2 3 3

S2 20 1 2 3 3

S3 30 1 2 3 3

S4 40 1 1 3 3

S5 50 1 1 2 3

The EA oligomer ratio is 100 phr and photoinitiator concentration is 5%.

Rating: 1, tacky; 2, slightly tacky; 3, non tacky

Physico-mechanical and chemical resistance:

The physico-mechanical and chemical resistance of all formulations are shown in Table (5). It

can be seen that the pencil scratch hardness of the EA coating was (2H) at low concentration of

EPOSA. By increasing the concentration up to 50 phr, the scratch hardness of coating was decreased

to give (1H) due to lower crosslink density. Also the pencil gouge hardness of cured surfaces

decreased by increasing the concentration of EPOSA to give (4H) for formulation S5 which contains

50 phr compared to the formulation S0 (6H) which does not contain EPOSA.

The bending and elongation test was carried out by 1 mm diameter rod. The results showed that,

the first three formulations (S0, S1, and S2) does not pass the test while by using high concentrations

of EPOSA for EA formulations (S3, S4 and S5), the films passed the test. This may be explained that

the lower crosslink density was produced at high concentrations of EPOSA and the coating film

becomes more elastic and flexible and passed the bending test.

The adhesion test for EA coatings containing different amount of EPOSA was also investigated

and the results showed that by increasing the concentration of EPOSA, the adhesion slightly increased

from 4B to 5B due to increasing the hydroxyl groups of EPOSA which form hydrogen bonding on the

surfaces.

Gloss of the cured samples was measured at 60o angle of reflectance using a novo gloss meter

and the results are given in Table (5). It can be seen that the gloss of the coating increased slightly

with the increase in the concentration of EPOSA. At higher concentrations of EPOSA, the cured films

have lower crosslinking density than formulations contain low concentrations of EPOSA which may


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be resulted in a decrease the micro distortions such as waviness caused by shrinkage generated on the

coating. The decrease of micro distortions in the coating surface decreased the scattering of the

reflected light in other direction and resulted in high gloss values at 60o angles.

Also, it was found that all cured panels of all formulations containing different amount of

EPOSA in acid (5 % HCl (32%) or alkali (5 gm anhydrous sodium carbonate/100 ml distilled water)

did not show any visible discoloration and any change in hardness measurements.

Table (5): Physico-mechanical and chemical properties of different formulations prepared by UV-

radiation at 20 min.

Formulation

Properties

S0 S1 S2 S3 S4 S5

Pencil hardness* 6H 6H 6H 5H 4H 4H

Scratch hardness 2H 2H 2H 1H 1H 1H

Bending test at

1mm mandrel

Not pass Not pass Not pass pass pass pass

Adhesion** 4B 4B 4B 5B 5B 5B

Gloss at 600 120 120 120 140 155 160

Acid resistance v.g.*** v.g. v.g. v.g. v.g. v.g.

Alkali resistance v.g. v.g. v.g. v.g. v.g. v.g.

Water resistance v.g. v.g. v.g. v.g. v.g. v.g.

*Lead pencils supplied with the unit, softest to hardest, are as follows:

9B, 8B, 7B, 6B, 5B, 4B, 3B, 2B, B, HB, H, 2H, 3H, 4H, 5H, 6H, 7H, 8H, 9H

**The adhesion of the cured films decreases in the following descending order:

5B> 4B> 3B> 2B> B.

*** Very good

Stain and steam resistance:

The coated and uncoated surfaces were tested against seven staining chemicals and the

performance of EA coating containing different concentrations of EPOSA is provided in Table (6). In

this test, drops of the staining agent were pipette out onto the coating surfaces and covered with glass

cup to prevent evaporation. For each test method, after a definite time of contact given in Table (6),

the staining agent was wiped out with tissue paper and cleaned with water and then the coating surface

was examined for discoloration or change in appearance. It was found that all the coating composition

did not show any discoloration or change in appearance and excellent stain resistance against the

staining agents taken for the test.

The cured films were also exposed to steam test for 1h and then the films were examined for any

visible changes on the coating surfaces due to steam. The results are reported in Table (6), indicating

that all the cured films of EA coatings containing different concentrations of EPOSA showed excellent

steam resistance test.


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Table (6): Stain and steam resistance of control and different formulations, cured at 20 min of UV

radiation

S5 S4 S3 S2 S1 S0 Control Time of

contact

Reagent Properties

6 6 6 6 6 6 5 10 min 30 % AcOH

Stain

resistance

6 6 6 6 6 6 3 10 min 25% NaOH

6 6 6 6 6 6 6 10 min 20% H2O2

6 6 6 6 6 6 4 10 min Boric acid

6 6 6 6 6 6 3 16 h ammonia 10%

6 6 6 6 6 6 1 16 h Coffee

(Nescafe)

6 6 6 6 6 6 2 16 h Tea (lepton)

4 4 4 4 4 4 4 2 h - Steam

resistance

The ratings for stain test: 1, dark brown stain; 2, light brown stain; 3, absorbed at surface,

yellow stain; 4, white rim; 5, faint rim; 6, no effect.

The rating for steam resistance test: 1, sample charred with surface damaged, black coloration; 2,

blisters with severe mark with black colour in the core and brown at periphery; 3, moderate brown

stain with no blisters;4, no visible change.

CONCLUSIONS

In this work, EPOSA was prepared via acrylation by introducing acrylic acid into epoxidized

sunflower oil. Epoxy acrylate resin was toughened by adding prepared EPOSA at different

concentrations and cured by UV irradiation at 20 min. The thermal, physico-mechanical and chemical

properties of cured films were investigated. The results showed that, at higher concentration of

EPOSA the hardness and thermal stability of cured films decreased, however, the flexibility and gloss

of cured films was improved. The different formulations were surface coated on different substrates

and the coated substrates were exposed to UV irradiation. The results showed that the adhesion and

chemical resistance were not affecting largely at high concentrations of EPOSA. Also, the formulation

which contains 30 phr of EPOSA gave the best compatibility between EA and EPOSA and good

results were obtained.

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