Article

Hydroxyapatite-Polycaprolactone Coating on 316L Stainless Steel Surface Using

Dip Coating Method

Ahmad Fadli^1,a*, Sri Helianty², Abdul Hariz³, Muhammad Rifaldi⁴

^1,2,3,4Chemical Engineering Department, Faculty of Engineering, Universitas Riau, 28293 Tampan, Pekanbaru.

Abstract

Stainless steel 316L is a metal that can be used for bone implants but exhibits low biocompatibility. The low

biocompatibility can lead to inflammation, infection, or rejection within the body's tissue system. It is coated with

hydroxyapatite-polycaprolactone to enhance the biocompatibility of stainless steel 316L. This study aims to examine

the effects of stirring time, stirring speed, and the appropriate hydroxyapatite-polycaprolactone ratio on the shear

strength of hydroxyapatite-polycaprolactone using the dip coating method and to determine the empirical model

for the resulting shear strength of the hydroxyapatite-polycaprolactone layer. Hydroxyapatite and polycaprolactone

were mixed using acetone and stirred at a speed of 150 rpm for 20 hr. Then, the stainless steel 316L substrate was

immersed in the suspension and dried at 56°C for 1 hr. The process conditions optimization in this study employed

a 2k modeling approach. The empirical shear strength model in this research is represented as y = -216.9 + 36.42A

+ 1.426B + 14.43C - 0.2345AB - 2.380AC - 0.08943BC + 0.01468AB*C, with an R2 value of 0.99. The variables with the

most significant influence on shear strength, ranked from largest to smallest, are the HA-PCl ratio (A), followed by

the two-way interaction between the HA-PCl ratio (A) and stirring speed (B), the three-way interaction between the

HA-PCl ratio (A), stirring speed (B), and stirring time (C), followed by the two-way interaction between the HA-PCl ratio

(A) and stirring time (C), stirring time (C), stirring speed (B), and the two-way interaction between stirring speed (B)

and stirring time (C). The highest shear strength of the hydroxyapatite layer was achieved at a HA-PCl ratio of 5:1.5,

stirring speed of 150 rpm, and stirring time of 20 hours, with a value of 5.71 MPa.

Keywords: Empirical Model, Hydroxyapatite-Polycaprolactone, Stainless Steel 316L.

Graphical Abstract

Introduction

*

Corresponding author

Email addresses: fadliunri@unri.ac.id

DOI: https://doi.org/10.22437/chp.v8i2.30842

Received December 28^th2023; Accepted December 31^st2024; Available online December 31^st2024

(https://creativecommons.org/licenses/by/4.0 )

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Chempublish Journal, 8(2) 2024, 109-119

Hydroxyapatite with the molecular formula

(Ca10(PO₄)₆(OH)₂) is a crystalline substance that

shares a mineral structure similar to that of

bones and teeth, featuring nanoscale calcium

phosphate. Hydroxyapatite can be derived from

both natural and synthetic sources of calcium.

Researchers have been utilizing hydroxyapatite

in biomedical applications for several years due

to its biocompatible, bioactive, and osteogenic

properties toward bones and teeth [1].

Additionally, HA is widely used as a bioactive

coating for dental and orthopedic implants. Its

excellent osteoconductivity and osteoinductivity

promote biological fixation between bone tissue

and implants, enhancing the integration and

longevity of the implants [2]. Comprising calcium

and phosphorus, hydroxyapatite is highly

suitable for crafting bone implants due to its

compatibility with the human skeletal system.

Both natural and synthetic sources of calcium

can be used to produce hydroxyapatite [3].

polylactic acid (PLA) and PCL are particularly

notable for packaging applications, attributed to

their

accessibility,

biodegradability,

and

advantageous mechanical properties. PCL is

distinguished by its exceptional chemical and

solvent resistance, commendable toughness,

and

low

glass

transition

temperature

(approximately -60°C) and melting temperature

(around 60°C) [7]. The polymer's high chain

segment mobility and minimal intermolecular

interactions contribute to these low thermal

transition temperatures. Notably, PCL exhibits

greater thermal stability compared to PLA and

undergoes complete degradation via enzymatic

activity [8]. Its inherent chain flexibility allows for

synthesis across

a

spectrum of molecular

weights, enhancing its versatility in various

applications. In comparison to PLA, PCL offers

higher flexibility but has relatively low strength

and a low melting point of 60°C, which restricts

its use in certain applications. Additionally, PCL's

hydrophobic nature results in lower wettability

compared to PLA, which can influence cell

adhesion in biomedical applications [7]. The

enzymatic degradation of PCL is influenced by

factors such as molecular weight and copolymer

composition. Studies have shown that an

increase in molecular weight leads to a decrease

in the enzymatic degradation rate, likely due to

increased chain entanglement that hinders

enzyme access. Furthermore, the incorporation

of hydrophilic segments, such as polyethylene

glycol (PEG), into PCL-based copolymers can

enhance the degradation rate by increasing the

material's overall hydrophilicity [9]. These

Hydroxyapatite serves as the foundational

material to coat titanium (Ti) with the

incorporation of titania (TiO₂) buffer using the

sol-gel method [4]. Hydroxyapatite is widely

employed to enhance the bioactivity of Ti and O₂

substrates, while a buffer layer is incorporated to

prevent corrosion of the Ti substrate and

strengthen the bond between hydroxyapatite

and the substrate. However, numerous studies

have highlighted challenges associated with non-

biodegradable coating materials, particularly

their potential to induce inflammation and crack

propagation pressure in the human body. These

issues have motivated researchers to explore

biodegradable coating materials and strategies

to improve bioactivity and bonding strength [5].

characteristics render PCL

a

material of

significant interest for applications requiring

biodegradable and biocompatible polymers with

tunable properties.

Hydroxyapatite

recommended for coating applications due to its

biocompatibility and crystallographic and

has

been

extensively

Despite its higher cost, polycaprolactone (PCL) is

frequently

selected

as

a

biodegradable

chemical properties that closely resemble those

of bone tissue. Despite these advantages,

hydroxyapatite is limited by its brittleness and

component for polymer blending due to its

compatibility with various biopolymers, notably

starch and lignin. This compatibility facilitates the

development of composites with enhanced

properties. For instance, blending PCL with

starch can improve the biodegradation rate of

PCL, while PCL can modulate the humidity

sensitivity of starch, resulting in materials with

low

adhesive

strength,

necessitating

the

inclusion of additional materials to serve as load-

bearing supports and to enhance cation

reinforcement [6].

Polycaprolactone (PCL) is

a

biodegradable,

biocompatible, and non-toxic aliphatic polyester.

Within the realm of biodegradable polymers,

balanced

mechanical

and

degradation

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Chempublish Journal, 8(2) 2024, 109-119

characteristics [¹⁰]. Similarly, incorporating lignin

into PCL matrices has been explored to enhance

thermal stability and mechanical properties,

although the compatibility between PCL and

lignin can vary depending on processing

methods and the specific types of lignin used.

Extensive research has been conducted on

blending polylactic acid (PLA) with PCL to

combine the advantageous properties of both

polymers. Such blends aim to achieve a balance

between the rigidity of PLA and the flexibility of

PCL, resulting in materials with improved

toughness and biodegradability. Studies have

shown that the addition of PCL to PLA can

enhance impact strength and elongation at

break, making these blends suitable for

placed into a chemical glass. Then, 15 ml of

acetone and 30% polycaprolactone/HA were

added. The suspension was then stirred using a

magnetic stirrer at the speeds of 150 rpm and

200 rpm for 16 and 20 hours, respectively. The

suspension preparation followed the research

method outlined by previous study [12].

Preparation of Substrat. Stainless steel 316L was

cut into 2 cm x 3 cm x 0.1 cm, then polished using

SiC 1200 grit sandpaper. The polished stainless

steel 316L was subsequently treated by

immersing it in 25% HNO₃solution, following the

research method of Kannan et al., 2004 [13],

using 50 ml of 20% HNO₃solution for 1 hour at

room temperature. It was then rinsed with

distilled water and dried in an oven for 30 min at

a temperature of 50°C. The metal was further

heated to a temperature of 600°C at a heating

rate of 2°C per min for 1 hR.

applications

requiring

both

strength

and

flexibility. The development of PLA/PCL blends

has been explored for various applications,

including packaging materials, medical devices,

and drug delivery systems, due to their combined

biodegradability and mechanical performance

[11]. In this paper aims to study the influence of

Coating Process. The coating method follows the

research conducted by Fadli et al., 2021 [14].

Pieces of stainless steel that have been treated

were attached to a dip coating apparatus. The

dipping process began by immersing the

substrate into the slurry. When approximately ¾

of the substrate was submerged, the apparatus

was stopped and left for 50 seconds, and then

the apparatus was restarted. This results in a

withdrawal process where the substrate in the

suspension was pulled upward, allowing a thin

layer to adhere to the substrate naturally.

Subsequently, a drying process was carried out

by placing the coated substrate in an oven at a

temperature of 56ºC for 60 min.

the

hydroxyapatite-polycaprolactone

ratio,

stirring speed, and stirring duration on the shear

strength of hydroxyapatite-polycaprolactone.

This study is also aimed at determining the

empirical model for the shear strength of the

resulting

coating.

hydroxyapatite-polycaprolactone

Material and Methods

Materials and Instrumentations

The materials used in this research are hydroxyapatite

(Lianyungan Kede Chemical Industry Co. Ltd, China),

Results and Discussions

stainless

steel

316L

(Jindal Stainless, India),

polycaprolactone (Juren Chemical, China), acetone

(Merck, Germany), and distilled water (Brataco

Chemica, Indonesia). The sample was characterized

The Effect of HA-PCL Ratio on Shear Strength

Value

using

a

Scanning Electron Microscope (SEM) to

The influence of the ratio in HA-PCL on the shear

strength of hydroxyapatite on stainless steel

surfaces results in increased viscosity. Higher

viscosity prevents the formation of interfacial

layers and substrates, thus providing favorable

conditions for particle adhesion to the substrate.

According to Tangestani and Hadianfard (2021), a

ceramic-polymer ratio of 2 g/L PCl prevents

agglomeration in the layer. This PCL content is

optimal for creating high adhesion between

examine its morphology and determine the thickness

of the coating. X-Ray Diffraction (XRD) analysis was

performed to identify the chemical compounds

present in the sample and their respective

compositions. Additionally, the shear strength of the

sample was evaluated using an autograph machine

Methods

Preparation of Suspension. Hydroxyapatite was

weighed in variations of 5 and 7 grams each and

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Chempublish Journal, 8(2) 2024, 109-119

particles and the substrate. However, at a ratio of

4 g/LPCl, the layer structure contains cracks that

open the way to penetrate corrosive fluids onto

the exposed metal surface.

6

y

5

4

3

2

1

0

Ratio HA-PCl

x

5 : 1,5

7 : 2,1

Figure 1. The Effect of Ratio on Hydroxyapatite Shear Strength

The influence of this ratio is in line with the theory

proposed by previous study [15]. Optimizing the

use of the HA-PCL ratio results in improved shear

strength. As shown in Figure 4.1, it can be

observed that the ratio affects the shear strength

of the layer. The use of a HA-PCl ratio of 7:2.1

yields a lower shear strength value compared to

a HA-PCl ratio of 5:1.5. This ratio is optimal for

creating the best shear strength between the

suspension and the substrate, with the highest

value being 5.71 MPa. This is because the ratio of

PCl to HA in the layer can influence shear

strength. The addition of HA to PCL can enhance

shear strength due to the stronger mechanical

properties of HA. However, an excessive amount

of HA addition can reduce the solubility of PCL in

the solvent and affect the formation of a proper

layer.

The Effect of Stirring Speed on Shear Strength

Value

In this study, the effect of stirring speed on the

shear strength of hydroxyapatite coatings

applied to 316L stainless steel was examined at

rotational speeds of 150 rpm and 200 rpm

(Figure 2). Stirring speed is a critical parameter in

mixing processes, as it influences particle

collisions and interactions, leading to alterations

in

the

solution's

density

and

viscosity.

Consequently, optimizing stirring speed is

essential to achieve a homogeneous mixture.

Research indicates that increasing the stirring

rate during the nucleation phase can reduce

hydroxyapatite nanoparticle size, suggesting that

higher stirring speeds enhance homogeneity in

the mixture [16].

Additionally, studies have demonstrated that

higher agitation forces, achieved through

increased stirring speeds, elevate the system's

An increase in PCl within the suspension results

in

higher

suspension

viscosity,

thereby

enhancing

the shear

strength

of the

dissipation

energy,

creating

significant

coating.Using a PCl ratio of 7:2.1 leads to

agglomeration within the formed suspension,

resulting in uneven deposition and surface

cracks, yielding lower shear strength. Figure 1

illustrates the extent of agglomeration and

deposition resulting from the use of the HA-PCl

ratio.

turbulence that promotes uniform particle

distribution [17]. Therefore, adjusting stirring

speed is a pivotal factor in the preparation of

hydroxyapatite coatings, directly affecting the

mixture's homogeneity and, consequently, the

coating's shear strength on stainless steel

substrates.

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Chempublish Journal, 8(2) 2024, 109-119

5,8

5,6

5,4

5,2

5

y

4,8

4,6

150

200

x

Stirring Speed (rpm)

Figure 2. The Effect of Stirring Speed on Hydroxyapatite Shear Strength

An increase in stirring speed can result in a layer

with higher strength. This is associated with

better homogenization and dispersion effects of

HA particles within the PCL matrix. High stirring

speed can help break down particle clusters and

evenly distribute them within the matrix,

enhancing the interaction between particles and

yields lower shear strength. Therefore, it is

concluded that the optimum results are obtained

when employing a stirring speed of 150 rpm in

this comparative study of different stirring

speeds.

The Effect of Stirring Time on Shear Strength

Value

the

matrix,

thus

increasing

shear

strength.However, excessively high stirring

speed can potentially damage HA particles or

lead to poor particle agglomeration. This can

reduce shear strength due to inadequate

interaction between particles and the matrix. To

assess the extent of the influence of stirring

speed in this study, refer to Figure 3.2, which

explains that a stirring speed of 150 rpm yields a

higher shear strength value compared to a

stirring speed of 200 rpm. the maximum result

was achieved at 150 rpm. Figure 2 shows that as

stirring speed increases, shear strength values

consistently decrease because faster collisions

occur, resulting in HA particle damage and

agglomeration within the suspension [18].

Stirring time has an impact on particle deposition

in the solution. Longer stirring times result in

smaller particles. Thus, the extended stirring

time leads to optimally dispersed particles.

Stirring time positively affects hydroxyapatite

coating suspension as it can stabilize particle

deposition and create a thicker coating. However,

if the stirring time exceeds the optimum

duration,

it

can

lead

to

agglomeration,

preventing maximal dispersion and resulting in a

thinner coating [19]. In this study, the stirring

time's influence on hydroxyapatite's shear

strength value can be observed in Figure 3.3,

which demonstrates that a stirring time of 20

hours yields a higher shear strength value

compared to a stirring time of 16 hr.

At a stirring speed of approximately 150 rpm,

particle mobility within the suspension without

temperature variation produces better results.

With a decrease in stirring speed, particle

mobility within the suspension increases,

resulting in a shear strength value of 5.71 MPa.

However, at a stirring speed of 200 rpm, the

suspension begins to agglomerate, reducing

particle mobility in the suspension, which is

directly proportional to shear strength. Figure 3

depicts the optimal HA-PCL composite position

with the use of stirring speed (a) 150 rpm

compared to stirring speed (b) 200 rpm, which

Figure 3. The Effect of Stirring Time on

Hydroxyapatite Shear Strength.

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Chempublish Journal, 8(2) 2024, 109-119

Figure 3. shows that there is a significant

decrease in viscosity in the suspension with one

of the time variables used. For a stirring time of

16 hours, the stabilization effect has not yet

reached the optimum point. Although this effect

can also be achieved with slightly lower shear

strength values (5.21 MPa), the achieved shear

strength has a higher average value compared to

a stirring time of 20 hr (5.71 MPa). This can be

seen in that the shear strength values decrease

with shorter stirring times and reach their

maximum value at 20 hrs of stirring. This

indicates that a 20-hr stirring time creates the

best adhesion between HA particles and the PCl

matrix.

Conversely, when the stirring time is at the

optimum point, the layer thickness is directly

proportional to the shear strength of the

hydroxyapatite layer.

Scanning Electron Microscopy Characterization

Scanning Electron Microscopy (SEM) is one of the

common methods for producing images of the

microstructure and morphology of various

materials. In this research, SEM analysis was

conducted at a magnification of 500 times. The

samples analyzed consisted of 2 samples to

study the influence of the HA-PCL ratio on the

thickness of the hydroxyapatite layer produced

on the surface of stainless steel 316L. The HA-PCL

concentration ratio, stirring speed, and stirring

time variations for these two samples were (a)

HA-PCL 5: 1.5 g, 150 rpm, 20 hours, and (b) HA-

PCL 7: 2.1 g, 150 rpm, 20 hours. From the SEM

analysis results, the average thickness of

hydroxyapatite for both samples was calculated.

For the HA-PCL ratio of 5: 1.5 g, stirring speed of

150 rpm, and stirring time of 20 hours, the

average thickness of hydroxyapatite was found

to be 65.27 μm, and it increased to 67.02 μm for

the HA-PCL ratio of 7: 2.1 g with the same stirring

speed and time. As more HA is added, the

thickness increases, as shown in Figures 4 (a) and

4 (b). This is because when more HA is used, the

mass of HA deposited on the substrate surface

increases [²¹]

The thickness of the layer is directly proportional

to the shear strength value, increasing as the

stirring time lengthens. As the layer thickness

increases, the shear strength also increases.

However, this condition also has an optimum

time. The thickness increases, the shear strength

value decreases because a thicker surface layer

requires more energy to fracture, causing the

interfacial shear strength of the composite to

gradually

decrease

with

increasing

layer

thickness [20]. A sufficiently weak surface layer

has a significant positive impact on the fracture

toughness of the composite. Therefore, it can be

concluded that if the stirring time exceeds the

optimum point, the formed of particle deposition

becomes thinner, leading to lower adhesion

between HA particles and polycaprolactone.

Figure 4. SEM Analysis Results of HA-PCL Layer Thickness on Stainless Steel 316L with Variable

HA-PCL Ratio, Stirring Speed, and Stirring Time (a) 5:1.5, 150 rpm, 20 hr; (b) 7:2.1, 150 rpm, 20 hr.

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Chempublish Journal, 8(2) 2024, 109-119

The SEM analysis data in Figure 4-5 indicates that

the thickness of the hydroxyapatite layer

produced supports the results of the bond

strength of the hydroxyapatite layer on the

surface of stainless steel. Hydroxyapatite with

excessive thickness results in a low shear

strength. This is due to the increase in the

thickness of the hydroxyapatite layer, which can

enhance the shear strength up to a certain point.

When the layer thickness increases, more energy

is released from plastic deformation. The process

of plastic deformation in HA-PCL involves the

molecular arrangement within the material.

When this material is subjected to pressure or

force, the intermolecular bonds in PCL can shift

or break [22].

Figure 5. Surface Morphology of Stainless Steel 316L Coated with HA-PCL with Variable HA-PCL

Ratio, Stirring Speed, and Stirring Time (a) 5:1.5, 150 rpm, 20 hrs; (b) 7:2.1, 150 rpm, 20 hrs.

Figure 4 shows the SEM image of the HA-PCL

coating deposited on the surface of stainless

steel 316L at a magnification of 500x. It can be

observed in Figure 5 (a) that the surface

morphology of the metal exhibits uniform apatite

formation, covering the metal surface with small

crystal-like structures. Meanwhile, in Figure 3.5

(b), HA particles tend to form agglomerates or

distribute non-uniformly within the PCL matrix.

This is due to the high concentration of particles

in the solution or suspension, which can increase

the likelihood of agglomeration. When the

particle concentration exceeds a certain limit,

particles tend to come into contact and interact

more intensely, leading to agglomeration.

Additionally, non-uniform particle distribution

can also cause particles to be close to each other

and form clusters [15].

layer on the surface of Stainless Steel 316L. It can

be observed that the product formed is

hydroxyapatite (HA). Overall, the hydroxyapatite

peaks after coating in Figure 3.6 have hkl values

similar to the characteristic pattern of standard

hydroxyapatite XRD analysis data from ICDD with

No. 01-072-1243, which are (200), (210), (211),

and (300) with 2θ angles of 21.743°, 28.896°,

31.741°, and 32.868°. The main peaks of

hydroxyapatite after coating at 2θ angles of

21.5619°, 29.2687°, 31.5470°, and 32.6697°

confirm the presence of hydroxyapatite content

in the coating layer.

X-ray Diffraction (XRD) Analysis

X-ray

Diffraction

(XRD)

Analysis

is

a

characterization technique that can be used to

determine the phases, structure, and crystallinity

of crystalline materials [23]. In this study, X-ray

diffraction (XRD) analysis was performed to

determine the crystallinity of the layers formed

on the surface of stainless steel 316L. Figure 6

shows the diffractogram of the hydroxyapatite

Figure 6. XRD Diffractogram of Stainless Steel

316L Substrate After Coating Using HA-PCL with

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Chempublish Journal, 8(2) 2024, 109-119

HA-PCL Ratio of 5:1.5, Stirring Speed of 150 rpm,

and Stirring Time of 16 hr.

while

controlled

cooling

may

promote

crystallinity [5]. Furthermore, the presence of

other polymers can impact the crystallinity of

PCL. Blending PCL with amorphous polymers,

such as polyurethane (PU), can alter its crystalline

structure. XRD patterns of PCL/PU blends have

shown that the semi-crystalline nature of PCL can

be modified by the amorphous characteristics of

PU, resulting in changes to the overall crystallinity

and, consequently, the mechanical properties of

the blend [6]. Understanding the relationship

between processing conditions, crystallinity, and

mechanical properties of PCL is essential for

Based on the XRD analysis results presented in

Figure 6, it is evident that the high intensity and

narrow peak width of the diffractogram confirm

that the majority of hydroxyapatite particles

crystallize on the surface of the stainless steel

316L substrate. The degree of crystallinity in the

hydroxyapatite-coated on stainless steel 316L is

approximately 63.47%. The crystallinity value of

the hydroxyapatite layer obtained in this study

meets the allowed range of hydroxyapatite layer

crystallinity, which is 60-90%. A high degree of

crystallinity can enhance the adhesion of the

hydroxyapatite layer [24]

optimizing

its

performance

in

various

applications. By controlling factors such as

cooling rates and blending with other polymers,

it is possible to tailor the material properties of

PCL to meet specific requirements.

The absence of polycaprolactone (PCL) peaks in

X-ray diffraction (XRD) analysis can be attributed

to its semi-crystalline nature, comprising both

crystalline and amorphous regions. When PCL is

heated above its melting point (approximately

55–60°C), its crystalline regions transition into a

molten state. Rapid cooling from this state can

hinder the reformation of crystalline structures,

resulting in an amorphous configuration. In this

amorphous state, PCL lacks the long-range order

necessary to produce distinct diffraction peaks in

XRD analysis, leading to its non-detection. The

mechanical properties of PCL are significantly

influenced by its degree of crystallinity.

Amorphous PCL exhibits a random molecular

arrangement, imparting greater elasticity and

flexibility. In contrast, semi-crystalline PCL, with

its ordered crystalline regions, tends to be more

rigid and exhibits higher mechanical strength.

This distinction is crucial for tailoring PCL's

properties for specific applications, such as in

biomedical devices where flexibility or rigidity

may be desired. Studies have demonstrated that

the crystallinity of PCL can be manipulated

through various processing techniques. For

instance, the incorporation of nanoparticles has

been shown to influence the crystallization

behavior of PCL, thereby affecting its mechanical

properties. Additionally, the rate of cooling

during processing plays a pivotal role; rapid

quenching can lead to amorphous structures,

Fourier Transform Infrared Spectroscopy (FTIR)

Analysis.

Fourier Transform Infrared Spectroscopy (FTIR)

Analysis is a method used to identify chemical

compounds based on the pattern of infrared

spectra it produces. This method is based on the

interaction between molecules and infrared

radiation. The FTIR testing process begins by

directing infrared light onto the sample to be

analyzed. Infrared light consists of various

frequencies covering the infrared wavelength

range. As the infrared light passes through the

sample, the molecules within the sample will

absorb energy at specific frequencies. This

process is referred to as infrared absorption. The

FTIR testing process begins by directing infrared

light onto the sample to be analyzed. Infrared

light consists of various frequencies covering the

infrared wavelength range. As the infrared light

passes through the sample, the molecules within

the sample will absorb energy at specific

frequencies. This process is referred to as

infrared absorption.FTIR spectrum analysis is

performed to confirm the functional group

information of the compounds Ca₁₀(PO₄)₂(OH)₂

and C₆H₁₀O₂that are produced.

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Chempublish Journal, 8(2) 2024, 109-119

Figure 6. FTIR Analysis of the Bond Strength of the HA-PCL Layer on Stainless Steel 316L with

HA-PCL Ratio of 5:1.5, Stirring Speed of 150 rpm, and Stirring Time of 20 hours.

The FTIR spectrum of the synthesized HA can be

seen in 6. The spectrum of HA shows absorption

at wavenumbers of 1165.69 and 1256.76 cm^-1

Yusoff et al., 2014 [21], reported their research

findings that the C-O-C group appears in the

wavenumber range of approximately 1300-1150

cm^-1. Vibration at a wavenumber of 2951 cm^-1is

observed in the methylene CH₂group. The

carbonyl acid C=O-OH group shows vibration at a

wavenumber of 1727 cm^-1.

at

a

wavelength of 958.18 cm^-1, which

3

corresponds to the vibration of the PO₄group.

The wavenumber for the vibration of the PO₄

3-

group obtained aligns with the research findings

reported by Yusoff et al., 2014 [21] where it

appears in the wavenumber range around 1000-

960 cm-1. The presence of OH- group vibration is

indicated by the absorption at wavenumbers of

3361 and 2951 cm^-1. OH- groups appear in the

wavenumber range of 3570-630 cm^-1. The weak

peak, which is the vibration of the CO32 group, is

indicated by the absorption at a wavenumber

group, which is indicated by the absorption at a

wavelength of 875.69 cm^-1. The vibration of the

Conclusion

The highest shear strength of hydroxyapatite-

polycaprolactone on stainless steel 316L is 5.71

MPa with an HA-PCL ratio of 5:1.5, stirring speed

of 150 rpm, stirring time of 20 hours, and a layer

thickness of 67.02 μm. The empirical model for

the shear strength of hydroxyapatite on stainless

steel 316L is given as y = -216.9 + 36.42A + 1.426B

+ 14.43C - 0.2345AB - 2.380AC - 0.08943BC +

0.01468AB*C, where (A) is the HA-PCL ratio, (B) is

the stirring speed, and (C) is the stirring time, with

an R2 of 0.99.

2-

CO₃group is a weak spectrum, indicating the

2-

presence of CO₃groups at a wavenumber of

875.69 cm^-1as a result of CO₂absorption from

the atmosphere on the surface of the HA

particles.

Meanwhile, the spectrum analysis of PCL shows

absorption at a wavenumber of 1725 cm-1, which

corresponds to the vibration of the carbonyl

group C=O. Additionally, there is a vibration of

the C-O-C ester group, as indicated by absorption

Acknowledgement

This research is supported by the University of

Riau, Chemical Engineering Department. We

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Chempublish Journal, 8(2) 2024, 109-119

sincerely thank the University of Riau, Chemical

Engineering Department for providing support

and assistance through resources, facilities, and

technical support during this research process.

Special thanks to Prof. Ahmad Fadli, ST., MT., PhD

and Sri Helianty, ST., MT for their insightful

discussions and feedback on this research. Thank

you to all team members and parties who have

helped make this activity possible. Without the

support of various parties, this research would

not have been realized."

Surmenev

Electrodeposited

biocoatings: Recent progress and future

challenges. Coatings. 2021;11(1):1-62.

doi:10.3390/coatings11010110

Mondal S, Park S, Choi J, et al.

RA,

Khalil-Allafi

hydroxyapatite-based

J.

6.

7.

Hydroxyapatite:

biomaterials to advanced functional

materials. Adv Colloid Interface Sci.

2023;321(October):103013.

doi:10.1016/j.cis.2023.103013

Negaresh M, Javadi A, Garmabi H.

A

journey

from

Author Contributions

Poly(lactic

blends:

acid)/

the effect

poly(ε-caprolactone)

of nanocalcium

Conceptualization, AH and MR.; Methodology, AH

and MR; Software, AH and MF.; Validation: AF and

SH., ST., MT; Formal Analysis, Abdul Hariz and

MR.; Investigation, AH and MR.; Resources, Abdul

Hariz and MR.; Data Curation, AH and MR.;

Writing – Original Draft Preparation, AH, MR, ;

Writing – Review & Editing, AH, MR, AF, SH;

Visualization: AH and MR.; Supervision, AF and

SH; Project Administration, AF.

carbonate and glycidyl methacrylate on

interfacial characteristics. Front Mater.

2024;11(March):1-15.

doi:10.3389/fmats.2024.1377340

Sivalingam G, Vijayalakshmi SP, Madras G.

Enzymatic and thermal degradation of

8.

poly(ε-caprolactone),

poly(D,L-lactide),

and their blends. Ind Eng Chem Res.

2004;43(24):7702-7709.

doi:10.1021/ie049589r

9.

Blackwell CJ, Haernvall K, Guebitz GM,

Groombridge M, Gonzales D, Khosravi E.

Enzymatic degradation of star poly(ε-

caprolactone) with different central units.

Conflic of Interest

The authors declare no conflict of interest

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