3D-Printable ABS Blends with Improved Scratch Resistance and

Article Cite This: Ind. Eng. Chem. Res. XXXX, XXX, XXX−XXX

pubs.acs.org/IECR

3D-Printable ABS Blends with Improved Scratch Resistance and Balanced Mechanical Performance Siyuan Chen,† Jiabao Lu,‡ and Jiachun Feng*,† †

State Key Laboratory of Molecular Engineering of Polymers, Department of Macromolecular Science, Fudan University, Handan Road 220, Shanghai 200433, China ‡ SAIC Volkswagen Automotive Co., Ltd., Yutian Road 7, Shanghai 201805, China ABSTRACT: Acrylonitrile−butadiene−styrene (ABS) is one of the most important materials utilized by fused deposition modeling (FDM) 3D printing. In this work, we prepared a series of 3D-printable ABSbased materials with improved scratch resistance and balanced mechanical performance via a simple blending strategy. The scratch resistant performance, mechanical strength, melt flow rate, hardness, transmittance, and surface gloss of ABS were improved simultaneously by adding 30 mass portion of poly(methyl methacrylate) (PMMA). Further addition of a small amount of methacrylate−butadiene−styrene (MBS), a kind of core−shell rubber modifier with high toughening efficiency, improved the toughness of ABS/PMMA effectively and hardly influenced the scratch resistance and optical properties of ABS/PMMA. This ABS/PMMA/MBS blend has the potential for large-scaled fabrication and can be developed as a new category of thermoplastic polymer material specially used for FDM 3D printing.

1. INTRODUCTION Additive manufacturing, also known as three-dimensional (3D) printing, has recently gained much attention from academic and industrial communities, considered as a supplement for traditional manufacturing and a potential to change the way we develop, produce, market, and distribute all sorts of products.1−6 3D printing allows the production of customized parts from metals, ceramics, and polymers without the need for molds or machining typical for conventional formative and subtractive fabrication, gaining popularity in a broad range of scientific disciplines for device fabrication, tissue engineering, microfluidics, and chemical reactionware.7−10 According to the technical differences, 3D printing can be classified as vat photopolymerization,11 powder bed fusion process,12,13 materials and binder jetting,14−16 sheet lamination and laminated object manufacturing,17,18 and fused deposition modeling (FDM).19−21 FDM 3D printing is the computer-controlled layer by layer deposition of molten and semimolten polymers, pastes, polymer solutions, and dispersions through a movable nozzle or orifice serving as the extrusion print head. FDM is a widely used 3D printing technology for its inherent advantages: relatively low total cost, relatively low requirement for technique, high compatibility with multiple printing materials, and excellent system reliability.22 In a typical FDM system, monofilament made of plastic material with a specific diameter (usually 1.75 or 3.00 mm) is extruded through a heated nozzle, and the extruded melt can then be spread in a controlled X-Y-Z movement onto the previous layer of the part being built. Subsequently, the deposited material cools, solidifies, and bonds with the neighboring material, and the printed object is obtained. FDM © XXXX American Chemical Society

technology has made tremendous progress after nearly 30 years of development, and the materials suitable for FDM 3D printing have attracted more and more concerns gradually. Among the large variety of materials applied in FDM, acrylonitrile−butadiene−styrene (ABS) is the most representative one.23−25 ABS is one of five most highly consumed polymers in the world, composed of particulate rubber, usually polybutadiene or butadiene copolymer grafted with styrene and acrylonitrile copolymer (SAN), as well as thermoplastic SAN matrix.26−29 Grafted rubber particles have excellent compatibility with SAN matrix and disperse well in SAN matrix, exhibiting a complicated sea−island biphase structure. The SAN matrix plays a decisive role to the high level of strength and rigidity, good chemical resistance, and surface gloss, while the rubber particles provide excellent toughness.30 Moreover, ABS has relatively low glass transition temperature and excellent processing property, indicating that ABS is easy to be processed as monofilament and further be printed at a moderate temperature. Additionally, ABS is a kind of noncrystalline polymer,31 which means that the shrinkage ratio during the cooling process is small enough to fabricate parts with high accuracy and dimensional stability. All of the above-mentioned characteristics make ABS an excellent candidate material for FDM 3D printing. Up to now, abundant categories of 3D printable ABS have been developed and put into market. For instance, Stratasys Received: Revised: Accepted: Published: A

December 7, 2017 February 28, 2018 March 2, 2018 March 2, 2018 DOI: 10.1021/acs.iecr.7b05074 Ind. Eng. Chem. Res. XXXX, XXX, XXX−XXX

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Industrial & Engineering Chemistry Research

2. EXPERIMENTAL SECTION 2.1. Materials. Acrylonitrile−butadiene−styrene (ABS) was supplied by Lanzhou Petrochemical Company (grade 301, China). The weight-average molecular weight of SAN is 1.1 × 105 g mol−1, and the rubber particle size is about 300 nm. Poly(methyl methacrylate) (PMMA) was purchased from Zhenjiang Chi-Mei (grade CM205, China). Methacrylate− butadiene−styrene (MBS) was provided by LG Chemistry (EM500A, Korea). Lubricants (magnesium stearate and dimethicone) were purchased from Aladdin Co. Ltd. Antioxidant 1010 was a commercial product. 2.2. Sample Preparation. Table 1 shows the blend designations and the constituents used for each blend

launched ABSplus with different colors, ABS-M30 with good ruggedness, ABS-ESD7 with static dissipation properties, etc. 3D Systems launched ABS-Armor and ABS-M3X with excellent tensile strength and good thermostable performance, respectively. Polymaker also rolls out ABS-Polylite featured of low odors and less warping. These products and relative investigations greatly expand the functionalities and applications of ABS in the field of FDM 3D printing. In some practical applications like auto parts, conceptual prototypes, fixture, and jig, both good scratch-resistant performance and balanced mechanical properties are urgently needed. However, to the best of our knowledge, there is no special report yet about 3D printable ABS-based materials with good scratch resistance and balanced mechanical performance. Actually, with regards to general plastic, some solutions of modifying scratch resistance have already been proposed. Among reported methods, adding some inorganic filler has a positive effect on the scratch-resistant property of polymers.32−34 Kurkcu and his colleagues found that soft fillers diminish the composites’ scratch hardness consistently with the corresponding decrease of the compressive yield stress, while hard fillers like glass spheres will increase the scratch hardness of ABS.35 However, inorganic fillers usually lead to lower flowability, worse surface gloss, and poor toughness, which have a negative influence on the process of 3D printing as well as properties of printed objects. Facile polymer blending strategies also pave the way for improving the scratch-resistant performance of ABS. By selecting different ingredients or changing content of each ingredient, various properties like processing properties and mechanical characteristics of polymer blends can be tuned freely.36−38 Previous researches indicate that scratch resistance of polymeric materials against scratch groove formation is tightly related to various mechanical properties, especially yield stress.39−42 Motamedi found that scratch groove width of polymer blends is directly related to yield stress. Generally speaking, the higher the yield stress is the lower the scratch width and initial depth will be. In addition, enhanced yield stress usually contributes to better resistance against tensile rupture at stick−slip peaks.43 Among different categories of polymers, poly(methyl methacrylate) (PMMA), which has good hardness and satisfactory processing properties, is widely used to improve scratch resistance of ABS.44,45 Therefore, the ABS/PMMA binary blend has the potential to be developed as a kind of scratch-resistant polymer alloy for 3D printing. However, the application of ABS/PMMA blend is still restricted on account of its inherent brittleness exhibited by PMMA. In this work, we prepared a series of 3D printable ABS-based materials with improved scratch resistance, balanced mechanical strength and toughness, and good surface gloss. The polymer blends consist of ABS, PMMA, and methacrylate−butadiene− styrene (MBS). MBS can improve the toughness of ABS/PMMA blends effectively and hardly decrease the scratch resistance and mechanical strength when the addition amount is low, which may be ascribed to its core−shell structure: the rubbery core provides resistance to impact and the grafted glassy shell provides rigidity and miscibility with the polymer matrix.46,47 The blends are easily extruded as monofilament with targeted diameter via traditional polymer processing apparatuses and suitable for a commercial FDM 3D printer. This kind of ABS/PMMA/MBS blend has the potential for large-scale fabrication in consideration of the facile blending strategy and low cost of the raw materials, and it could be launched into the market as a new category of thermoplastic 3D printing material.

Table 1. Constituents of ABS/PMMA Binary Blends and ABS/PMMA/MBS Ternary Blendsa content (mass portion) designation

ABS

PMMA

MBS

100ABS 90ABS/10PMMA 80ABS/20PMMA 70ABS/30PMMA 70ABS/30PMMA/2MBS 70ABS/30PMMA/4MBS 70ABS/30PMMA/6MBS

100 90 80 70 70 70 70

0 10 20 30 30 30 30

0 0 0 0 2 4 6

a

Contents of antioxidant 1010, magnesium stearate, and dimethicone in each sample were 0.25%, 0.4%, and 0.05% (mass percentage, wt %), respectively.

investigated in our study. In order to eliminate the effect of absorbed moisture on the processing and material performance, ABS pellets, PMMA pellets, and MBS powder were first dried in the oven at the temperature of 80 °C for 3 h. Subsequently, ABS, PMMA, and MBS as well as other polymer processing aids with different feeding ratios were well mixed and extruded using a twin-screw extruder (HAAKE Polylab OS, Thermo Fisher, Waltham, MA). The speed of main screws was 45 rpm, and the feeding speed was 15%. Pressure on main screws was about 10 bar. Temperatures of zones 1−10 were 190, 200, 210, 210, 220, 220, 210, 210, 200, and 200 °C, respectively. Then the compound was pelletized using a granulator, dried again at the above-mentioned conditions, homogenized through mixing, and finally re-extruded into 1.75 ± 0.02 mm monofilament via a single-screw extruder. With regards to the single-screw extruder, temperatures of zones 1−3 were 200, 230, and 220 °C, respectively, the die temperature was 220 °C, and the speed of the main screw was 15 rpm. A portion of the monofilament was cut up again and molded as different specimens with specified size for various measurement, and the rest of monofilament was 3D printed directly into different specimens. 2.3. 3D Printing. Monofilament of different blends was used to print different structures by a FDM 3D printer (Maxform, Shenzhen Clopx. Co. Ltd., China). A workflow that illustrates the process of fabricating a 3D structure based on a commercial FDM 3D printer is shown in Scheme 1. First of all, digital models were predesigned in a computer with the software SketchUP (Trimble Navigation, America) and then exported as standard triangle language (STL) file types. The STL files were modified with the printer software Maxform (Clopx, China) and exported as gcode file types. Then the gcode files were imported into the FDM 3D printer. Under a FDM system, monofilament made of B

DOI: 10.1021/acs.iecr.7b05074 Ind. Eng. Chem. Res. XXXX, XXX, XXX−XXX

Article

Industrial & Engineering Chemistry Research Scheme 1. Illustration of the Process of Fabricating a 3D Structure Based on a Commercial FDM 3D Printer

SANS universal testing machine at 2 mm/min according to GB/ T 9341-2008. All the specimens were kept in the room at 25 °C for 48 h; then they were subjected to various mechanical tests immediately. The average values of all the mechanical properties were obtained from five specimens. The transmittance of samples with different constituents was characterized using a Lambda 750 UV−vis spectrophotometer (Massachusetts, America). The measurement wavelength was from 400 to 800 nm, located in the visible regions. Specimens for transmittance test were rectangular sheets with the uniform size of 5.0 × 3.5 × 0.5 mm. 60° specular gloss of different samples was obtained by using a BYK Gardner Micro-TRI Glossmeter (Bavaria, Germany).

different constituents with the diameter of 1.75 mm was fed into the printer via a pinch roller. The nozzle diameter of the FDM printer was 0.40 mm, and the nozzle temperature was set at 230 °C. The temperature of the platform is another important parameter in a FDM system, which was set at 100 °C to ensure the excellent adhesive attraction between printed objects and the platform as well as the good dimensional stability of the printed objects. The printing speed was maintained at 3.0 m/min for all the layers. The layer height was set as 0.2 mm. The specimens were printed layer by layer. The first layer was printed with a deposition orientation of 45°, and the second layer was printed with an orientation of 135°. Then, the third layer, fourth layer, and subsequent layers were printed with deposition orientations of 45° and 135°, alternately, until the height of specimens reaches the specified value. To obtain good mechanical properties, the infill density was set as 100%. 2.4. Measurement Procedures. Melt mass-flow rate (MFR) of different samples was measured by a XRZ-400-1 melt indexer (Changchun, China) according to the standard of GB/T 3682-2000. The experimental temperature was set as 220 °C, and the load was kept at 10 kg. Scratch tests were carried out via a Erichsen motor-driven crosscutting tool (Berlin, Germany) according to the Volkswagen’s standard of PV3952. The specimens, with a size of 80 × 80 × 6 mm, were conditioned for a minimum of 48 h in a standard climate (temperature is 23 °C, the relative humidity is 50%) according to DIN 50 014-23/50-2. Then a scratching tool was used to scratch a crosscut grid of at least 40 × 40 mm with a constant contact force of 10 N. The scratching speed is 1000 mm/min. Subsequently, the scratch morphology of various samples was observed and analyzed with the help of a polarization optical microscope (POM, DM2500P, Leica, Germany). The scratch width of various samples was counted based on an average of ten scratches. Rockwell hardness was measured with a 200HSR-45 Rockwell hardness tester (Shanghai, China) according to GB/T 3398.12008. The initial testing force and main testing force were 98.07 and 588.4 N, respectively. Specimens for mechanical tests were prepared by two methods: (1) fabricated by hot press at 220 °C and (2) fabricated by 3D printing. These two series of specimens were tested under the same condition. The notched Charpy impact strength of different specimens was measured using a JJ-20 impact tester (Changchun, China) according to the standard of GB/T 1043-2008. Tensile tests of dumbbell-shaped specimens were performed with a SANS universal testing machine (Shenzhen, China) at 5 mm/min according to GB/T 1040-92. The flexural properties of the samples were obtained with the

3. RESULTS AND DISCUSSION 3.1. MFR of Different Samples. The MFR value of polymer materials is a significant characteristic, considered as one of the Table 2. MFR Values of Samples with Different Constituents designation

MFR (g 10 min−1)


13.6 13.9 15.9 16.4 16.1 15.5 14.7

criteria to judge whether the material is suitable for the FDM system. In a typical FDM process, monofilament on the spool is fed into the nozzle with the help of feeding pressure generated from the driver gear and the grooved bearing; then the monofilament will be heated to molten state above glass transition temperature or melting temperature. Provided that the MFR value is low, the extruding process will be hindered severely which means that the nozzle would be blocked and interrupt the printing process. On the contrary, an excessively high MFR value also has disadvantages in the printing process; for instance, the extruded material is less likely to support itself which will do harm to dimensional accuracy. Based on our investigations on different categories of commercial ABS used for FDM 3D printing, ABS with MFR values ranging from 10 to 30 g 10 min−1 can be printed successfully using our FDM 3D printer. As shown in Table 2, the MFR value of pure ABS is 13.6 g 10 min−1. As the content of PMMA increases from 10 to 30 mass portion, the MFR value of ABS/PMMA binary blend increases from 13.9 to 16.4 g 10 min−1, indicating that PMMA can promote the fluidity of ABS in this study. When the toughness C


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Figure 1. Polarized optical micrographs of different samples under bright field with magnification of 50×.

the increase of PMMA from 10 to 30 (mass portion), the scratch width decreases from 199 to 143 μm, demonstrating that PMMA is able to improve the scratch resistance property of ABS effectively. Adding a small amount of MBS has negligible influence on the scratch resistance performance of ABS/PMMA/ MBS. With regards to 70ABS/30PMMA/6MBS, the scratch width is 149 μm. The above-mentioned analysis reveals that scratch resistant property of pure ABS is not good enough, which may be attributed to the high content of soft polybutadiene rubber particles, while PMMA has an obvious positive effect on the scratch resistant performance of ABS/PMMA blends. We noticed that a small amount of MBS has negligible negative impact on the scratch resistance properties of ABS/PMMA/ MBS ternary blends, which may be owing to the special structure of MBS. Different from common elastomer toughening agent, MBS is a toughness polymer with core−shell structure. Although the rubber core consisting of polybutadiene or poly(styrene− butadiene) is soft, the shell made up of polystyrene or poly(methyl methacrylate) that is chemically grafted onto the core has a much higher glass transition temperature, which makes the shell of MBS rigid enough to resist scratch. 3.3. Rockwell Hardness of Different Samples. As shown in Figure 3, addition of PMMA enhances the Rockwell hardness of ABS significantly. The Rockwell hardness of pure ABS is 89.7. When the content of PMMA reaches to 30 mass portion, the Rockwell hardness of ABS/PMMA is 100.4, increased by 12%. On the other hand, addition of MBS will slightly decrease the hardness of polymer blends. When 2, 4, and 6 mass portions of MBS were further added into ABS//PMMA blend, the Rockwell hardness decreased to 100.2, 98.4, and 96.1, respectively. The dwindling of hardness is slight, which may be related to the core− shell structure of MBS. 3.4. Mechanical Properties of Samples Prepared by Hot Press. The tensile properties at room temperature of ABS/ PMMA binary blends and ABS/PMMA/MBS ternary blends are presented in Figure 4. With regards to a specific sample, at least five tests were conducted to report the average. From the typical stress−strain tensile curves and corresponding statistical data, the elongation at break value of pure ABS is determined as 35.4%, while the values for ABS/PMMA binary blends containing 10, 20, and 30 mass portion of PMMA are 33.4%, 31.6%, and 30.1%, respectively. With the addition of 2, 4, and 6 mass portions of MBS into 70ABS/30PMMA, the values increase to 32.4%, 36.5%, and 41.2%, respectively. These results demonstrate that PMMA has a negtive effect on the tensile toughness of ABS while the addition of a small portion of MBS is able to compensate for

Figure 2. Scratch width of different samples under a constant contact force of 10 N.

Figure 3. Rockwell hardness of ABS/PMMA binary blends and ABS/ PMMA/MBS ternary blends.

modifier MBS was added into the ABS/PMMA blend, there is a slight declining trend of the MFR value. Thus, it can be seen that all the binary and ternary blends in this study have appropriate molten fluidity, which is a fundamental prerequisite for the FDM printing system. 3.2. Scratch Resistance Performance of Different Samples. The PV3952 standard of Volkswagen Company was followed for scratch resistance test. A series of crisscross grids were obtained under the constant scratch force of 10 N. Samples with different constituents have different scratch behavior, which could be observed and analyzed by POM. Figure 1 exhibits the variation trend directly: The scratch grid of pure ABS is the widest. With the increase of the content of PMMA, the scratch grid becomes thinner gradually. The detailed numerical result of the scratch grid is shown in Figure 2. The scratch width of pure ABS is 225 μm, which is the highest among all the samples. With D


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Figure 4. Typical stress−strain curves (a), values of elongation at break (b), elasticity modulus (c), and tensile strength (d) of different samples prepared by hot press at 220 °C.

the toughness loss of ABS/PMMA. The elasticity modulus increases from 738 to 985 MPa when the content of PMMA is up to 30 mass portion. Although the addition of MBS will reduce the modulus gradually, the elasticity modulus of 70ABS/30PMMA/ 6MBS is still slightly higher than that of 70ABS/20PMMA. The tensile strength values of various samples follow the same trendency as elasticity modulus. According to previous works, various mechanical properties such as yield stress are influential to the scratch resistance of polymers against scratch groove formation.39−43 As shown in Figure 4a, the addition of PMMA enhances the yield stress of ABS effectively, which is consistent with the improvement of material’s scratch resistance. By comparing properties of various samples, it can be concluded that the rigidity and tensile strength of ABS can be ehanced obviously with the addtition of 30 mass portion of PMMA, and

Figure 5. Notched Charpy impact strength of pure ABS, ABS/PMMA binary blends and ABS/PMMA/MBS ternary blends prepared by hot press at 220 °C.

Figure 6. Bending modulus (a) and bending strength (b) of pure ABS, ABS/PMMA binary blends, and ABS/PMMA/MBS ternary blends prepared by hot press at 220 °C. E


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Figure 7. Typical stress−strain curves (a), values of elongation at break (b), elasticity modulus (c), tensile strength (d), bending modulus (e), bending strength (f), and impact strength (g) of different samples prepared by 3D printing.

Table 3. Surface Gloss of Samples with Different Constituents (60° Specular) designation

60° specular surface gloss


82.9 87.9 90.5 92.2 92.1 94.1 95.5

further addition of a small amount of MBS (less than 6 mass portion) could improve the tensile toughness effectively at the expense of a small fraction of material rigidity.

Figure 8. Transmittance of pure ABS, ABS/PMMA binary blends, and ABS/PMMA/MBS ternary blends during the wavelength range from 400 to 800 nm. F


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rubber with that of PMMA and SAN in ABS because rubbers usually have relatively low refractive index. With regards to MBS, the copolymers of styrene and methyl methacrylate act as the refractive index enhancer, which is beneficial to match their refractive index. What is more, the particle size of MBS is small enough to avoid turbidity. Therefore, a small amount of MBS will not worsen the transmittance of ABS/PMMA. As shown in Table 3, the surface gloss of pure ABS and 70ABS/30PMMA is 82.9 and 92.2, respectively, demonstrating that PMMA improves the surface gloss of ABS obviously. Further addition of MBS is also able to improve the gloss of ABS/PMMA gradually. When the mass of ABS, PMMA, and MBS is 30, 70, and 6, the surface gloss reaches up to 95.5, which may be ascribed to the compatibilization effect of MBS in ABS/PMMA/MBS blends.

The impact strength of pure ABS, ABS/PMMA, and ABS/ PMMA/MBS at room temperature is shown in Figure 5. With the introduction of PMMA, the impact strength of ABS/PMMA decreases rapidly. The impact strength of pure ABS is 32.9 kJ/m2, while the value of 70ABS/30PMMA decreases to 17.3 kJ/m2. ABS/PMMA/MBS blends containing 2, 4, and 6 mass portions of MBS have the impact strength of approximately 19.7, 21.5, and 22.4 kJ/m2, indicating the high toughening efficiency of MBS. Bending-resistant properties are crucial mechanical parameters for ABS and ABS-based blends in a bulk of applications. Variation of bending modulus and bending strength of pure ABS, ABS/PMMA, and ABS/PMMA/MBS is shown in Figure 6. As expected, addition of PMMA enhances the bending modulus and strength of ABS to a large extent. The addition of a small amount of MBS hardly decreases the rigidity of ABS/PMMA until the mass portion of MBS is up to 6 mass portions. 3.5. Mechanical Properties of Samples Prepared by a FDM 3D Printer. Tensile properties, impact strength, and bending properties of different samples prepared by 3D printing are shown in Figure 7. Elongation at break value of pure ABS is 14.7%. The elongation at break values of ABS/PMMA binary blends containing 10, 20, and 30 mass portions of PMMA are 13.5%, 13.2%, and 13.3%, respectively. When 6 mass portion of MBS was added, elongation at break value increased to 17.4%. The impact strength of pure ABS is 19.2 kJ/m2, and the value of 70ABS/30PMMA is 14.9 kJ/m2. Further addition of 6 mass portion of MBS improved impact strength effectively (18.2 kJ/ m2). PMMA has an obvious enhancement effect on elasticity modulus, tensile strength, bending modulus, and bending strength, while MBS has an opposite effect on those parameters. Therefore, it can be concluded that mechanical properties of samples prepared by 3D printing and hot press nearly have the same trend when different mass portions of PMMA and MBS were added into ABS. After comprehensive consideration, we think that materials consisting of 70ABS/30PMMA/4MBS or 70ABS/30PMMA/6MBS has relatively balanced mechanical properties. These results also make a point: samples prepared by 3D printing has worse mechanical properties than those prepared by hot press, especially for elongation at break, elasticity modulus, and impact strength. In a typical FDM system, specimens were prepared track by track and layer by layer, and such a printing process generates a large amount of voids and gaps inevitably, resulting in worse mechanical performance. 3.6. Optical Properties of Materials with Different Constituents. Optical properties are of great significance to practical utilization of 3D Printed objects. Surface smoothness of specimens has a tremendous impact on optical testing; hence, all the specimens for optical measurement in this work were prepared by hot press instead of 3D printing. It was found that PMMA is able to improve the transmittance and surface gloss of ABS, and a small amount of MBS has a similar effect. Pure ABS prepared by emulsion polymerization and continuous bulk polymerization is commonly milk white or slightly yellow. Notably, as shown in Figure 8, the introduction of PMMA improves the transmittance of ABS to a large extent during the whole range of visible light. Interestingly, the introduction of a small amount of MBS, such as 2 or 4 mass portion, even slightly improves the transmittance of 70ABS/30PMMA during some bands. Previous research revealed that perfect transparency of multiphase blends is usually limited by the presence of haziness or reduced clarity, primarily arising from failure to match the indexes of refraction of the polymer phases and rubber particle sizes.46 It is difficult to match the refractive index of common

4. CONCLUSIONS In this work, a series of scratch-resistant polymer blends with the feasibility of 3D printing were prepared using ABS, PMMA, and MBS. The ABS/PMMA/MBS blends have excellent processing properties and can be extruded as monofilament with 1.75 mm diameter via traditional polymer processing apparatus. Because of the appropriate MFR values, the blends are especially suitable for a FDM 3D printer. PMMA promotes the scratch resistant property effectively, and MBS nearly has no effect on it, confirmed by POM analysis. The variation trend of Rockwell hardness is same as that of scratch resistant property. On one hand, tensile strength, elasticity modulus, bending strength, and bending modulus can be enhanced obviously by PMMA. On another hand, impact strength and elongation at break are improved with the addition of a small amount of MBS. Taken together, ABS/PMMA/MBS has relatively balanced mechanical properties (i.e., rigidity, strength, and toughness). Moreover, ABS/PMMA/MBS ternary blends have satisfactory transmittance and surface gloss, meeting aesthetic demands. Therefore, this ABS/PMMA/MBS blend has the potential for largescaled fabrication and can be developed as a new category of polymer materials specially used for FDM 3D printing.

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AUTHOR INFORMATION

Corresponding Author

*Tel +86 21 65643735; Fax +86 21 6564 0293; e-mail jcfeng@ fudan.edu.cn (J.F.). ORCID

Jiachun Feng: 0000-0002-9410-7508 Author Contributions

J. Feng and S. Chen proposed the idea and developed the methodology. S. Chen and J. Lu contributed to the data acquisition and interpretation. S. Chen wrote the manuscript. All authors reviewed the manuscript. Notes

The authors declare no competing financial interest.

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ACKNOWLEDGMENTS We gratefully acknowledge the financial support from the National Natural Science Foundation of China (No. 51773040 and 21574029). We also greatly thank for the beam time provided by Shanghai Synchrotron Radiation Facility. G


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