AIP Conference Proceedings 2137, 040003 (2019); https://doi.org/10.1063/1.5121001 2137, 040003

© 2019 Author(s).

Effect of printing temperature onmechanical properties of copper metalpolylactide acidCite as: AIP Conference Proceedings 2137, 040003 (2019); https://doi.org/10.1063/1.5121001Published Online: 07 August 2019

Mohd Fara Zureel Ikhqwan bin Mohd Arpan, and Lim Joon Hoong

Effect of Printing Temperature on Mechanical Properties of Copper Metal Polylactide Acid

Mohd Fara Zureel Ikhqwan bin Mohd Arpan 1, a) and Lim Joon Hoong1, b)

1School of Engineering, Faculty of Built Environment, Engineering, Technology & Design, Taylor’s University, Subang Jaya, Selangor, Malaysia.

a)mohdfarazureelikhqwanmohdarpan@sd.taylors.edu.my

b)Corresponding author: JoonHoong.Lim@taylors.edu.my

Abstract. The effect of printing temperature on the mechanical properties of metal Polylactide Acid (PLA) through 3D printing have been investigated. Metal PLA was a composite formed from the amalgamation of metal powder and PLA. The study was focused on using copper metal PLA with 15 percent copper metal powder which can be obtained commercially. The objective of this study is to investigate the differences between mechanical properties of model printed with metal PLA and pure PLA under different printing temperatures. The printing temperature ranges from 180 to 230 with an increment of 5 . The sample of metal PLA were shaped into cuboid using 3D print. The elemental analysis of 3D printed metal PLA was carried out using scanning electron microscope equipped with energy dispersive X-ray spectroscopy (SEM-EDX). The SEM-EDX showed the elemental composition and cross-sectional surface topography of the metal PLA. The quality of the filament depends on the amalgamation between copper metal powder and PLA. The mechanical properties of tensile strength was characterized through tensile test according to ASTM D3039 type 5 standard for polymer composite at a 50 percent infill density. The results obtained will be compared with pure PLA. Through the tensile test, the 3D printed metal PLA has a higher tensile strength and modulus of rigidity compared to pure PLA. The increase in printing temperature has increases the tensile strength of the printed samples. Finally, the printing temperature for optimum tensile strength was at a temperature of 215oC. The addition of the copper in the filament also causes the PLA become conductive.

INTRODUCTION

3D printing technology revolutionized the manufacturing industry by its innovative and disruptive approach towards the fabrication of a product. The technology’s development can be traced back to the 1980s where the accessibility to the masses are limited [1,2]. Nowadays, it is popular due to the decrease in cost of the machines and the materials. In addition, the flexibility and customization it offers attracts businesses to invest in the technology. Manufacturers, innovation companies and commerce companies realize the market available through 3D printing technology and has started to pay attention to the technological advances in the future [3]. Currently, the technology is also being utilized in large-scale applications such as buildings and houses [4]. Newly built industries such as the spare-parts manufacturing, have been boosted by the popularization of 3D printing technology [1,5].

Metal filled filaments are made from metal powder mixed into PLA and forming Metal PLA. This makes metal

filled filaments denser and heavier when compared with other filaments. As a result, the 3D printed objects feel heftier on hand and has a metallic finish. There are various kinds of metal powder that can be added to produce these metals filled filaments such as Copper, Bronze, Brass and Stainless Steel. Depending on the manufacturer, the percentage amount of metal added in each filament can vary. These values may also change according to the thickness of the filament due to the higher is the metal powder percentage to base material (PLA), the more fragile is the metal filament spool [6].

Proceedings of the International Engineering Research Conference - 12th EURECA 2019AIP Conf. Proc. 2137, 040003-1–040003-7; https://doi.org/10.1063/1.5121001

Published by AIP Publishing. 978-0-7354-1880-6/$30.00

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Different from full metal 3D printing processes, the use of Metal PLA can be done at home at a hundredth of the cost. Large established printing companies were paving the way for the 3D printing industry to grow with their high-fidelity full metal printers. The printers at work can reach up to a temperature of 1400 degrees Celsius with also comes with a large cost. There are still untested theories regarding the effects of printing parameters such as printing temperature and extrusion mass flow rate on the mechanical properties of Metal PLA. Due to the addition of the metal in the filament, the printing temperature of the filament has also change. The change in temperature is hypothesized to be affected by the metal to PLA ratio of the compound and the optimum settings of printing Metal PLA can be determined [3,4].

The research objectives of this study were to investigate the effects of different printing temperature to the

mechanical properties of copper metal PLA. Due to the addition of copper metal powder in the filament, the operating temperature of the filament is changed. Past researches had shown that addition of a metal powder decreases the optimum printing temperature of metal PLA. However, the concentration of metal powder added was 50% higher compared this study. Therefore, in this study the effect of printing temperature on the mechanical properties for copper PLA were investigated. In addition, the tensile strength between 3D printed copper PLA and pure PLA were compared.

RESEARCH METHODOLOGY

ASTM D3039 type 5 will be used as a reference in preparing the test samples for the mechanical properties testing [7]. The samples will be created at 50 percent infill density using a 3D printer with a nozzle size of 1.0 mm and a printing speed 45 mm/s. A larger nozzle diameter than the standard diameter of 0.4 mm was used so that there were no clogging issues due to the large copper metal powder in the metal PLA filament. The print speed was set to half of the default printing speed of 90 mm/s due to the metal PLA filament unable to complete a layer with an acceptable infill and surface quality. Infill density was reduced to 50 percent as printing time of the samples can be reduced. Average of 5 samples were printed for each printing temperature. For the energy dispersive X-ray spectroscopy (EDX) characterization, a sample of the copper metal PLA and pure PLA were printed in the shape of a cuboid with dimensions of 22 x 10 x 10 mm. The samples will be coated with a layer of silver for SEM-EDX analysis. The elemental composition of the samples will be analyzed through EDX. For SEM, the samples are taken from 4 different locations on the metal PLA filament spool.

Energy Dispersive X-Ray Analysis (EDX) also known as EDS or EDAX, was a technique that utilizes X-ray

radiation to identify the composition of elements in various materials. By knowing the composition of a material, research and troubleshooting can be advanced. This study reflects on the previous studies by using a filament with reduced amounts of metal powder. The commercially available copper PLA was stated to have a composition of 20 percent copper. The actual amount of copper metal infused was confirmed through the EDX analysis [8]. Scanning Electron Microscopy (SEM) analysis used to provide high-resolution imaging that analyze various materials for surface fractures and flaws. The high-resolution imaging was produced by a focused electron beam emitted by the microscope onto the sample to reveal the surface topography. This analysis was used to evaluate the quality of the amalgamation between the copper metal and PLA in the Metal PLA filament. It was suspected that the amalgamation of the materials in the filament leads to the mechanical strength of printed structures [9]. Electrical conductivity of the 3D print copper PLA were carried out using Ossila T2001A3 4-point probe. There were two steps in the experimental setup preparation of the sample and probe arrangement. The four probe was arranged linearly in a straight with equal distance from each probe. Pure PLA is nonconductive at room temperature but starts to conduct electricity above 70 degrees Celsius where the insulator component starts to fail [10].

RESULTS AND DISCUSSION

SEM analysis was done to a sample from the Metal PLA to determine how well the copper blends with the PLA and determine the surface topography. It was necessary for the Copper powder and PLA to mix evenly in the filament, as uneven distribution of Copper will lead to structural weakness of printed models. Figure 1 shows the high-resolution images obtained after the SEM analysis. The analysis was repeated with different sample obtained from different parts of the filament. This was to ensure that the surface topography and the amalgamation was identical throughout the filament spool.

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(a) (b)

(c) (d)

FIGURE 1. High-resolution images produce thorough SEM analysis.

The SEM analysis reveals that most of the samples obtained from copper PLA filament spool were well blended

as shown in Figure 1. However, some samples also show copper agglomerates that will potentially cause difficulty in printing. These agglomerates affect the diameter of nozzle to print using copper PLA. High concentration of Copper agglomerates on one section of the filament will also result to lower structural strength of the 3D printed models. Since only one out of four images from the samples showed the existence of agglomerates, the quality copper PLA filament spool were considered good. The EDX analysis was done to differentiate between Copper and PLA. The two boxes; red and green that placed on the high-resolution images as shown in Figure 2 was the EDX analysis areas.

FIGURE 2. SEM-EDX analysis to differentiate the Copper and PLA

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The differences in composition between copper and PLA in the printed sample printed was identify through EDX. The analysis was used to identify the elements of the sample but not the molecular structure. The trace of silver, Ag was due the coating for the analysis. Based on Figure 3, EDX traces of Copper metal was identify in copper PLA whereas the pure PLA only shows the normal composition of PLA in the area of orange box shown in Figure 2. The EDX trace of copper was identify in Figure 3(a) where the EDX analysis was done within the green box area as shown in Figure 2.

(a) (b)

FIGURE 3. EDX spectrum graph of (a) copper PLA and (b) pure PLA. The conductivity test was done using the 4-point probes method to test the electrical conductivity of the compound.

The test was carried out with ab average 5 printed samples for each printing temperature from the range of 180oC -230oC. PLA was known to be a non-conductive material that was also a good thermal insulator. This means efficiently trap heat which was not ideal in products such as mobile phones that had a processor that needs to dissipate heat generated. As shown in Table 1, the metal PLA shows it was electrically conductive therefore also, thermally conductive due to the addition of copper metal. The result also shows that as the printing temperature increased, the electrical conductivity increased. At higher temperatures, the particles had high energy to overcome the bonds with neighbors and move from lattice sites [8]. Copper particles was much larger than PLA therefore, the copper would move to a vacant site and complete the amalgamation. This results in the increased in electrical and thermal conductivity as the printing temperature of the sample increased.

TABLE 1. 4-point probe electrical conductivity test of copper metal PLA sample at different printing

temperatures. Temperature ( ) Electrical Conductivity (S/cm)

1 2 3 4 5 Average 180 1.1047 1.1025 1.1002 1.1046 1.1069 1.1037 185 1.1342 1.1320 1.1297 1.1342 1.1365 1.1333 190 1.1659 1.1635 1.1612 1.1658 1.1682 1.1649 195 1.1914 1.1890 1.1866 1.1913 1.1937 1.1904 200 1.2128 1.2104 1.2079 1.2128 1.2152 1.2118 205 1.2250 1.2226 1.2201 1.2250 1.2275 1.2240 210 1.2454 1.2429 1.2404 1.2454 1.2479 1.2444 215 1.2679 1.2653 1.2628 1.2678 1.2704 1.2668 220 1.2832 1.2806 1.2780 1.2831 1.2857 1.2821 225 1.2862 1.2836 1.2811 1.2862 1.2888 1.2851 230 1.2872 1.2847 1.2821 1.2872 1.2898 1.2862

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Tensile sample was prepared using ASTM D3039 Type 5 tensile standard test method for polymer matrix composites. Table 2 shows the results of the tensile test conducted. Instron tensile machine was set at speed of 5 mm/min under 50kN load. The test was then repeated using pure PLA at the same range of temperatures. The tensile test result of pure PLA samples were shown in Table 3.

TABLE 2. Tensile strength result of samples from copper metal PLA printed at different temperatures. Printing Temperature ( ) Tensile test (MPa)

1 2 3 4 5 Average 180 22.43 22.34 22.43 22.39 22.47 22.41 185 22.89 22.89 22.94 22.84 22.80 22.87 190 23.55 23.50 23.46 23.55 23.60 23.53 195 24.21 24.21 24.26 24.16 24.11 24.19 200 26.11 26.16 26.01 26.11 26.06 26.09 205 26.98 26.93 26.87 26.98 27.03 26.96 210 27.88 27.88 27.94 27.82 27.77 27.86 215 27.94 27.94 28.00 27.88 27.83 27.92 220 28.12 28.12 28.18 28.06 28.01 28.10 225 28.22 28.11 28.21 28.27 28.15 28.19 230 28.21 28.28 28.16 28.22 28.10 28.19

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Table 3. Tensile strength result of sample from pure PLA printed at different temperatures. Printing Temperature ( ) Tensile test (MPa)

1 2 3 4 5 Average 180 23.12 23.01 23.04 22.95 23.12 23.04 185 23.50 23.74 23.64 23.50 23.63 23.60 190 23.80 23.96 23.89 23.92 23.60 23.83 195 23.94 23.85 23.81 23.91 23.87 23.87 200 23.97 24.13 24.03 24.07 24.01 24.04 205 24.12 24.22 24.45 24.27 24.13 24.23 210 24.77 24.73 24.93 24.72 24.87 24.80 215 25.44 25.45 25.02 25.43 25.80 25.42 220 26.10 26.11 26.17 26.07 26.02 26.09 225 26.25 26.15 26.28 26.29 26.12 26.21 230 26.27 26.29 26.14 26.25 26.13 26.21

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FIGURE 4. Tensile Strength of metal PLA and pure PLA under different printing temperatures

0

5

10

15

20

25

30

170 180 190 200 210 220 230 240

Tens

ile S

treng

th (M

Pa)

Printing Temperature ( )

Copper metal PLA Pure PLA

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Based on Figure 4, the tensile strength of Copper metal PLA was higher than pure PLA especially at printing temperature 220 to 230 . This was predicted before that the atoms have high energy at higher printing temperatures promoting the movement of copper to a vacant lattice site. When atoms obtain enough activation energy, they can break the inter-atomic bonds between neighboring atoms. The metal PLA benefits from the movement of large copper particles into vacant lattice sites as it reduces the porosity of the material therefore increasing mechanical strength. At lower printing temperatures around 180 to 195 , the metal PLA had a weaker tensile strength compared to pure PLA. The addition of metal powder in metal PLA had affected its performance due to increase void spaces and clusters of copper particulate. Based on the standard deviation of the results of copper metal PLA and pure PLA, the significance of the printing temperature parameter on these materials can be found. The copper metal PLA had a higher standard deviation which means the printing temperature affects the mechanical strength of the material more than pure PLA.

Previous research on metal PLA had mentions that the metal powder in composite gives 3D printed structures a

weaker mechanical strength than pure PLA. The material used in that research consists of 36 percent Copper and Brass metal powder which was more than double of the copper metal PLA used in this study. The metal PLA with higher concentration of metal powder shows a tensile strength of only half of pure PLA. Reducing the concentration of metal powder in the filament will increase the tensile strength of the 3D printed model as seen in this study. The tensile results show that the maximum tensile strength the metal PLA and pure PLA can achieve is 28.10 MPa and 26.22 MPa respectively. However, at minimum printing temperature, the tensile strength of metal PLA and pure PLA is 22.41 MPa and 23.05 MPa respectively. This shows that printing temperature is an important factor to be considered when operating with metal PLA. At minimum printing temperature, the tensile strength of metal PLA is lower than pure PLA. This is due to the movement of copper atoms towards the vacant lattice site which at low temperatures, the atoms do not have enough activation energy to break the bonds.

CONCLUSION

In conclusion, the objectives of the study was achieved, where the effect of printing temperature towards the mechanical strength of copper metal PLA. The copper metal PLA was also compared with pure PLA in terms of mechanical strength and electrical conductivity. The optimum printing temperature was also determined by observing the increase in tensile strength as printing temperature increases. The increase in tensile strength became minimal as the printing temperature increase. Since there were minimal difference between performances of metal PLA at 215 to 230 , the optimum printing temperature of metal PLA was concluded to be at 215 . Taking from an economic perspective, the cost of metal PLA was higher than normal PLA but in return offers, structural heftiness, reduced material shrinkage and higher tensile strength provided that it was printed at its optimum printing temperature of 215 . Increasing the printing temperature higher may give additional tensile strength, but also increase the overall printing cost. As 3D printer operates the whole duration of the printing time, higher printing temperature can cause the power used to increase.

ACKNOWLEDGMENTS

The author gratefully acknowledge the financial support provided by Taylor’s University via the Taylor’s Research Grant Scheme (TRGS/ERFS/1/2018/SOE/027) for this study.

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