Contact Angle Properties of Bioacrylic Palm Oil Based
Polyol for Polyurethane CoatingERNIE Suzana Ali1,2,a, NURUL Najwa Mohd Nordin 1,b, FARAH Wahida
Harun2,3,c, SYAZANA Ahmad Zubir 4,d and NORAZWANI Mohd Zain2,5,e
1Applied Physics Programme, Faculty of Science and Technology, Universiti Sains Islam Malaysia,
71800 Nilai, Negeri Sembilan, Malaysia

2Frontier Materials Research Group (FMRG), Faculty of Science and Technology, Universiti SainsIslam Malaysia, 71800 Nilai, Negeri Sembilan, Malaysia
3Industrial Chemical Technology, Faculty of Science and Technology, Universiti Sains IslamMalaysia, 71800 Nilai, Negeri Sembilan, Malaysia
4Biomaterials Niche Area, School of Materials and Mineral Resources Engineering, EngineeringCampus,Universiti Sains Malaysia, 14300 Nibong Tebal, Pulau Pinang, Malaysia.
5Fabrication & Joining Sect, Universiti Kuala Lumpur Kampus Cawangan Malaysia France Institute.
aernie@usim.edu.my, bnajwanordin453@gmail.com, cfarahw@usim.edu.my,dsyazanazubir@usm.my, enorazwani@unikl.edu.my

Keywords: Palm oil, Polyurethane, Coating, Biobased, Synthesis.

Abstract. Bio-acrylic palm oil based polyol was synthesized and characterized for polyurethane (PU)coating. In this project, acrylation of palm oil based polyol was done by using different amount of
2-hydroxyethyl methacrylate (HEMA) along with styrene mole ratio at 1:0.5:2, 1:1:2 and 1:1.5:2. The
result shows that the increasing amount of HEMA content has increased the hydroxyl value. The
characterization of bio-acrylic palm oil based polyol carried out by IR spectroscopic analysis andhydroxyl value. Coated surfaces were then characterized for the drying and gelling time, contact
angle test and FTIR analysis were also reported. As the NCO/OH ratio of the coatings increased, there
were progressive increased in mechanical and anticorrosive properties for all the coatings. Overall,this study showed that the material holds promise to be used as an effective surface
coating compound by designing the formulation based on the desired performance.
Introduction
Polyurethanes is a polymeric material that is very easy to set up for a variety of applications. The
application of polyurethane is extremely varied and diverse; polyurethane can be produced as foams,
elastomers, plastics, adhesives and surface coatings for materials [1,2]. However, the increasing costof petrochemical crude materials and diminishing stores of petroleum assets cause the expanding of
the intrigued in the applications of biodegradable and renewable polymeric materials. Thus,
renewable feedstock from vegetable oils for polyurethane industries get to be exceedingly alluring forboth financial and natural reasons. Vegetable oils (VO) are non-toxic, non-depletable, domesticallyabundant, non-volatile and biodegradable resource. Other than that, petroleum-based also is
non-biodegradable and lack of petroleum resources. The use of palm oil and its products, which isrenewable and biodegradable, making palm oil as an alternative raw material for the production ofpolyurethane polyol based on palm oil [3,4]. Furthermore, there is an increased awareness of social
responsibility toward the environment to meet the demand for renewable resources andenvironmentally friendly products [5].
Polyurethane coating on surface will provide a thin film, high gloss finish with exceptional
weathering performance characteristics [6,7]. This coating is used in virtually all industrial
markets to provide a smooth durable finish that has superior resistance to corrosion, abrasion, andchemical exposure. Polyurethanes are normally used to topcoat high build polymer and metal
surfaces. The utmost attention is driven towards the design and development of new polyurethanes

with outstanding damage, scratch and wear resistance, the aesthetic apparel and functional
performance of in-service topcoats are often compromised in short time [8,9,10]. In this study, thebioacrylic polyol was prepared using different amount of HEMA along with styrene. The effects ofdifferent amount of HEMA to palm oil polyol on curing and contact angle of PU coatings wereinvestigated.
Materials and Methodology
Materials. 2-hydroxyethyl methacrylate (HEMA), palm oil polyol, dibenzoyl peroxide, isophorone
diisocyanate (IPDI) and diethylene glycol (DEG), dibutyltin dilaurate (DBTL) and pre-treatedaluminium 6016 (Al 6016) were purchased from Terra Scientific (M) Sdn. Bhd.
Synthesis of bioacrylic palm oil. Acrylation of palm oil based polyol was done by blending of palm
oil polyol with various amount of HEMA added with styrene at a mole ratio of 1:0.5:2, 1:1:2 and1:1.5:2. The mole ratio of palm oil polyol and styrene were fixed at 1 and 2 mol, respectively, moleratio of HEMA was varied at 0.5, 1 and 1.5 mol. Palm oil based polyol, HEMA and styrene weremixed in a 250 ml three-neck flask equipped with filter funnel, thermometer and nitrogen gas inlet.
Temperature was set at 60ºC with a continuous stirring and purified monomers dissolved in dibenzoyl
peroxide initiator (0.5 per cent by wt. of monomer) were added slowly and continuously stirred for 2hours at 60ºC. The mixture was then cooled to room temperature, sealed in a glass bottle and kept atroom temperature.
Preparation of bioacrylic palm oil urethane coating. For the preparation of polyurethane coating,bioacrylic palm oil was reacted with isophorone diisocyanate (IPDI) as a hardener. IPDI andbio-acrylic polyol were mixed at different (NCO:OH) molar ratio of 1:1, 2:1 and 3:1 to obtain various
coating formulations. Dibutyltin dilaurate (DBTL) as a catalyst was added drop wise in a mixture ofNCO:OH. The mixture was thoroughly mixed using a spatula and then were applied using 38 mmnylon brush on the pre-treated aluminium 6016 (Al 6016). Coated Al 6016 panel was cured at room
temperature for 72 hours.
Characterization. The acrylated polyols were examined using Fourier transform infrared
spectroscopy (FTIR) and hydroxyl value. A coated surfaces were then characterized for the dryingand gelling time, contact angle test and FTIR analysis.
Results and Discussions
Bio-acrylic Palm oil based polyol. Figure 1 shows FTIR spectrum of palm oil polyol. Figure 2, 3and 4 showi the FTIR spectrum of acrylated palm oil based polyol with different ratios. FTIR analysis
reveals characteristic bands found in an acrylic polyol. Based on Figure 2 to 4, the wavenumber
ranging between 3000 cm$% and 3500 cm$% for acrylic polyol samples A, B, and C, can be assigned tothe presence of hydroxyl groups. The stretching vibration of OH band indicates the presence ofhydroxyl groups of polyols in the structure. Furthermore, FTIR spectrum shows that acrylic polyol Cwith a ratio of 1:1.5:2 in Figure 4 has a higher of –CH stretching vibration starting from peak 2537 to3383 cm$% compared to the polyol A and polyol B. This shows that the acrylation of polyols
completely occur in the acrylic polyol C. This happened due to the higher content of HEMA
monomer present in acrylic polyol C which is 1.5 ratio used to enhance the acrylation occurs.
The hydroxyl value was obtained by calculating the constant value normality of NaOH as shownin Table 1. Based on the results obtained, it can be summarized that the hydroxyl value of acrylic
polyol C (1:1.5:2) gives the highest hydroxyl value which is 351 with functionality obtained is 10. It
indicates that the highest content of HEMA as monomer in polyol sample gives impact to thehydroxyl value and functionality obtained.
This could be due to the solubility of HEMA in water and easy to react with styrene monomer andpalm oil polyol as well as absorbents for bodily fluids and lubricious coatings. It is also used as anacrylic modified polyurethane coatings and widely used for the preparation of styrene-butadiene
rubber thermosetting acrylic emulsion paint modifier.

Fig. 1. FTIR analysis of palm oil polyolFig. 3. FTIR analysis of acrylic polyol B (1:1:2)

Fig. 2. FTIR analysis of acrylic polyol A (1:0.5:2)

Fig. 4. FTIR analysis of acrylic polyol C (1:1.5:2)

Table 1. Specification of acrylic polyol (OH - hydroxyl value)
Acrylic polyol
OH Value
Functionality, f(x)A (1:0.5:2)

157

4

B (1:1:2)

234

7

C (1:1.5:2)

351

10

Bio-acrylic Palm oil based Coating. Coating properties of polyurethanes are characterized by its
drying and gel time. The results shows that the acrylic polyol B shows lowest drying time, followedby acrylic polyol A and acrylic polyol C. Coated samples were compared on the basis of rise inhydroxyl content and NCO:OH ratio 1:1, 2:1 and 3:1. For the polyurethane coating, the sample also
has been characterized using drying and gelling time. The coating was cured by chemical reactions of–NCO group of IPDI isocyanate with –OH group of polyols.
The gelling time indicates the maximum length of time during which the system remains in fluid
condition. The gel time for the formulation was found to be around one day to completely dry withaddition of dibutyltin dilaurate (DBTDL) catalyst. The present of DBTDL catalyst helps to increase
the drying and gelling time and the sample can dry faster on the aluminum substrate. Other than that,the addition of the DBTDL catalyst and preferring the isocyanate-polyol reaction provides to acquire
greater hardness of the formed polyurethane coating. Besides, various polyol samples 1:0.5:2, 1:1:2
and 1:1.5:2 with different ratios of NCO to OH; 1:1, 2:1 and 3:1 shows the results condition obtained
is different for each ratio. The condition obtained was either sticky or wet. All samples took around24 hours to completely dry.

Furthermore, the verification hydroxyl content of polyols rising the cross-linking and the hardnessof polyurethane shown by the hardness of the sample that increased with increase in hydroxyl valueof acrylic polyols. Therefore, the acrylic polyols with high hydroxyl value have a tendency easy forharden than others. In further investigation of polyurethane coating, a contact angle test wasperformed to determine high or low of water’s ability contact angle on different surfaces. Hence, theangle of the contact surface was taken immediately after the sample touch on the surfaces of glass andTeflon as shown in Table 3.
Table 3. Contact angle, θ of PU coating from two different surfaces
Types of surface
Acrylic polyol
Ratio of PU coating
Contact angle, θGlass
A
1:1
45°
2:130°
3:1
24°
B
1:130°
2:130°
3:1
40°
C
1:121°

Teflon

AB

C

2:1
3:1
1:1
2:1

30°
22°
90°
50°

3:1

90°

1:1

90°

2:1

90°

3:1

90°

1:190°

2:1
3:1

90°
90°

Based on the observation, the experimental results obtained is mostly the same for all the samplesof polyurethane coating. The angle of the sample on the glass surface is small which is less than 90ºi.e. in the range of 20-50º. This shows that the liquid spread over the glass surface as glass surface isknown as hydrophilic surface. For the Teflon surface, the angle of the sample obtained is larger whichis equal or bigger than 90º. The angle obtained is 50º and 90º. The liquid form looks as a bead on thesurface. This type of surface is called as hydrophobic surface. The angle obtained is due to the type ofcharacteristic surface of material and physical properties of sample whether in liquid or solid form.
FTIR results shows the reaction between isocyanate of IPDI and hydroxyl group (-OH) of acrylic
polyol during the formation of polyurethane. It is revealed that the ratio acrylic polyols C (1:1) of
polyurethane shows a hydroxyl of polyol band at 3287 cm$% and no peak of NCO of isocyanate group
found during the curing process. For polyurethane coating of ratio acrylic polyol C (2:1), it shows theband of hydroxyl polyols present at 3302 cm$% and 2947 cm$% and stretching vibration of NCO presentat 2268 cm$% . The –CH group and NCO of isocyanate group of acrylic polyol C (3:1) present at
2947 cm$% and 2253 cm$% . It is believed that the polyurethane coatings manufactured by utilizing
acrylic polyols and IPDI had occurred between NCO and OH group get cross-linked properly to form
urethane linkage. Hence, based on the circle exist on the blue line from the spectra above shows thatthe isocyanates completely react and there is an excess of –OH and this show that acrylic polyol C(1:1) of polyurethane is sensible for a specific end use specification in polyurethane coatings.
Conclusions
The acrylation of palm oil based polyol was successfully done by mixing palm oil polyol, styrene andHEMA using a various ratio of HEMA monomer content. The hydroxyl value of acrylic polyol C ofratio 1:1.5:2 showed the highest which is 351 with functionality obtained is 10. Based on the FTIR

test also has shown that the present of OH group of polyols mostly abundant found in acrylic polyol Cwith ratio 1:1.5:2 that have the highest HEMA monomer content 1.5. Furthermore, the curing time of
the coating has decreased when dibutylin dilaurate (DBTDL) was used as catalyst which helps thecoating completely dry in a short time. Then, the large angle from contact angle test obtained showsthat good performance and confirmation of acrylation palm oil based polyol can be applied in surface
coating application.
Acknowledgements
The authors would like to dedicate our deepest gratitude to Universiti Sains Islam Malaysia (USIM)
Short Grant Scheme, grant no PPP/USG-0216/FST/30/17916 for the financial support. Authors also
thank Islamic Science University of Malaysia (USIM) and Universiti Kebangsaan Malaysia for thetechnical supports and facilities.
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