Scratch Hardness Properties of Waste Palm Cooking Oil based
Polycaprolactone Urethane Coatings
Norazwani Muhammad Zain1,a, W. A. Ashraf1,b and Ernie Suzana Ali2,c1

Fabrication and Joining, Universiti Kuala Lumpur Malaysia France Institutes, 43650 Bandar BaruBangi, Selangor, Malaysia.

2

Faculty of Science & Technology, Islamic Science University of Malaysia, 71800 Bandar Baru Nilai,Negeri Sembilan, Malaysia.
anorazwani@unikl.edu.my (corresponding author), bamirulashraf102@gmail.com,
cernie@usim.edu.myKeywords: Waste palm cooking oil, polycaprolactone polyol, polyurethane, coatings.

Abstract. Polyurethane has been widely used in various coating industries due to its good weathering
resistance, promising appearance, excellent elasticity and good mechanical properties. The present
work reports the development of polycaprolactone urethane coatings based on waste palm cooking oil(WPCO). WPCO was recycled to synthesis polycaprolactone (PCL) polyol using two-steps methods;
transesterification and ring opening polymerization with various ratios of ε-CL to WPCO basedpolyesteramide. The WPCO based PCL polyols were reacted with isophorone diisocyanate (IPDI) to
produce polycaprolactone urethane coatings. FTIR analyses were employed to confirm the formationof polyols and the scratch resistance properties of coatings were characterized by scratch hardness
testing. The results revealed that the scratch resistance of polycaprolactone urethane coatings
increased by increasing the ε-CL composition in the formulation.
Introduction
Polyurethane (PU) coating industry having a unique combination of performance and application
properties. The major concern of restriction of commercial exploitation of PU are largely related tothe cost of raw material is too high. Various countermeasures have been made to cut down the cost ofPU production, such as the use of bio-materials resources for the synthesis of polyol. Recycling ofwaste materials is also one of the most important issues in the research and development for reducing
the production cost and protection of global environment.
Waste palm cooking oil (WPCO) is waste materials from food industry resulted from degradation
reaction during frying due to presence of heat, air and water.The degradation reaction reduced thequality of oil and caused adverse effect to human if it is consumed as food. Uncontrolled dumping of
WPCO to the drainage system without proper treatment can lead to severe environmental problems.
WPCO has potential as raw material for PU production due to its physical and chemical properties.
Waste cooking oils have been exploited especially in bio-fuel and polymer productions [1, 2].
Moreover, waste cooking oil is considered as biodegradable and renewable resource that wouldreduce the environmental pollution and disposal problem.
The application of organic and hybrid clear coats has increasingly gained reputation for protection
purposes aesthatic value added in several manufacturing domains [3]. Topcoats is an outermost layerof coating with variable thicknesses. A wide variety of substrates can be used such as electronics andbiomedical devices, automotive body parts and components, and sporting goods. During the daily
usage, many of the aforesaid basic products are subject to a broad range of loading conditions,
including impacts, rubs and scratches of diverse magnitudes. These issues further complicate theextrapolation of the coatings response to external loads and, therefore, a proper strategies to prevent
damage is crucial. In this respect, many of the investigations reported in the literature regard thedefinition of relatively novel polyurethane-based formulations [4-6]. 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.
For the development on innovative PU coatings whilst respecting the environment, in the present
study, the PCL polyol was prepared by ring opening polymerization of ε-caprolactone initiated byWPCO based polyesteramide. The effect of different ratios of ε-CL to WPCO based polyesteramide(PEA) on scratch hardness properties of PU coatings was investigated.
Materials and Methods
Materials. ε-caprolactone (high purity), 2-(dimethyamino)-ethanol (DMEA), 1,8-diazabicyclo
5.4.0 undec-7-ene (DBU), isophorone diisocyanate (IPDI) and diethylene glycol (DEG) werepurchased from Terra Scientific (M) Sdn. Bhd. Waste palm cooking oil (WPCO) was collected fromrestaurants in Klang valley, Malaysia.
Synthesis of Waste Palm Cooking Oil (WPCO) based Polyol. There are two-steps involved in
the synthesis of WPCO based polyol. First step, WPCO based polyol was synthesized by usingtransesterification process by mixing a polyhydric solution with WPCO and 1,8-diazabicyclo 5.4.0
undec-7-ene (DBU) as a catalyst. The transesterification was performed in a chemical reactor at atemperature of 90°C for about 1 hour under vacuum and inert condition. In the second step, thesynthesis was continued by using the ring opening polymerization by adding the ɛ-caprolactone (CL)into the mixture and it was continuously stirred and maintained at the same temperature for another 2hours. Nine types of polyol, labeled as PCL10, PCL20, PCL30, PCL40, PCL50, PCL60, PCL70,PCL80, PCL90 were prepared with different ratios of CL to WPCO based polyesteramide varied from
90:10, 80:20, 70:30, 60:40, 50:50, 40:60, 30:70, 20:80 and 10:90, respectively.
Preparation of Polycaprolactone Urethane Coatings. For the preparation of polycaprolactone
urethane coating, PCL polyol based on WPCO was reacted with isophorone diisocyanate (IPDI) withisocyanate to polyol (NCO:OH) ratio is 1:1. AA 6061 was used as a substrate to test the performanceof the coating produced. The PU coating was applied on the metal surface by using nylon brush andthe samples were left at room temperature for complete curing (72 hours) before testing theirperformance properties.
Characterization. WPCO based polyol samples were analyzed using Fourier Transform Infrared(FTIR) Spectroscopy to confirm the formation of polyol. A scratch hardness test was carried out for
all PU coated substrates according to ASTM D3363. A coated substrate was placed on a firmhorizontal surface. The pencil was held firmly against the film at a 45° angle and pushed away fromthe operator in a 6.5 mm (1⁄4 in.) stroke. The process was started with the hardest pencil andcontinued down the scale of hardness until the pencil that will not cut into or gouge the film. The scale
used in the scratch hardness test is shown in Fig. 1.

Fig. 1: Scratch Hardness Scale
Results and Discussion
FTIR Analyses. The spectra of WPCO, ε-CL and derivative PCL polyols with different ratios ofε-CL: WPCO based polyesteramide are revealed in Fig.2. FTIR spectrum for a sample of WPCO andε-CL are used as a reference to observe any changes in the formation of the essential peaks for theproduction of polyol i.e. hydroxyl (OH) and carbonyl (C = O) peak. The stretching peak at frequency
1736 cm-1 the spectrum of ε-CL specifies the presence of C = O group in the cyclic lactone. WPCOsamples also showed the presence of C=O group in its structure. The C=O peak was also observed at
1727 cm-1 for WPCO based polyesteramide (PEA) and all the PCL polyols samples (PCL10, PCL50and PCL90) including the samples which are not revealed (PCL20, PCL30, PCL40, PCL60, PCL70

and PCL80). The shifted of carbonyl band designates the formation of a linear ester linkage and ring
opening polymerization of lactone had occurred [7]. The presence of broad peak around the frequency
3500-3200 cm-1 indicates the formation of free hydroxyl (OH) group in the PCL polyols. This also
supported the phenomena that the C=C bond had reacted and converted to C-OH bonding or forming
oligomer with other compounds. The presence of free OH group is essential in the polyol production
because this functional group will react with isocyanate to form polyurethane structures.
Furthermore, band at 2930 cm-1 and 2857 cm-1 are synchronous reflections of asymmetric
methylene (CH2). The band observed at 730 cm-1 is due to the rocking CH2 (n>3) vibration indicatesthe presence of a long linear chain aliphatic structure [8]. Another change was in the appearance of thepeak of C-N stretch for tertiary amide from WPCO based polyesteramide at around 1631 cm-1
according to the addition of WPCO based as starting material.

Fig.2: FTIR spectraScratch Hardness Behaviour of Polyurethane Coatings. Fig. 3 shows scratch resistancebehavior of the PU coatings. It is clearly seen that the scratch resistance of PU coating showedsignificance dependences on ε-CL composition. As the ε-CL composition increases in the PCL
polyols the scratch resistance of PU coatings was also increased. The surface of PU10 – PU40
samples were displayed too softs due to their scratch hardness fell in B scale. PU50 and PU60 showintermediate values of hardness scale (HB and H). The samples scratched at lower scale of hardness
due to the lower amount of entanglements in the polymer. Meanwhile, PU90 sample that composed of
90% of ε-CL shows the highest scratch resistance (4H). This might be due to the formation ofphase-separated hard domains acting as physical cross-links, thus hindering the crystallization
process [9]. While the increased hardness might be explained by the increasing the degree of PCL
phase crystallinity of these samples, this should also lead to increased resistance to scratch. This
argument agreed by Flores et al. [10] and Batista et al. [11] which increasing the degree ofcrystallinity increases hardness and density of a material. The dissolved hard segments likely
decrease the deformability of the soft phase as well. The dependences of hardness properties on thepolyols composition are shown in Fig.4.

Fig.3: Scratch behavior of PU coatings with various types of PCL polyols

Fig.4: Dependences of hardness behavior on ε-CL composition

Conclusion
In conclusion, WPCO has great potential in replacing petroleum and vegetable oils as starting raw
material for polyurethane coatings. FTIR established the WPCO-based PCL polyols have beensuccessfully synthesized using transesterification followed by ring opening polymerization. A seriesof WPCO based polycaprolactone urethane coatings was successfully. These PU coatings displayed
significant dependences of scratch resistance on ε-CL composition. The higher the ratio ε-CL toWPCO based polyesteramide increases the scratch resistance and hardness of PU coating.

Acknowledgement
The authors would like to dedicate our deepest gratitude to International Polyurethane Technology
Foundation, Japan for the financial support. Authors also thank Universiti Kuala Lumpur, Islamic
Science University of Malaysia (USIM) and Malaysia Nuclear Agency for the technical supports andfacilities.
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