Elsevier

Materials & Design

Volume 102, 15 July 2016, Pages 276-283
Materials & Design

Mechanical and thermal properties of ABS/montmorillonite nanocomposites for fused deposition modeling 3D printing

https://doi.org/10.1016/j.matdes.2016.04.045Get rights and content

Highlights

  • ABS filaments were reinforced by Organo-Montmorillonite(OMMT) nano plates, forming 3D printed nanocomposites

  • The mechanical properties of the 3D printed samples increased with the increase of the OMMT loading in ABS matrix.

  • The thermal and dimension stability of the 3D printed samples increased with the increase of the OMMT loading.

  • Addition of OMMT increased the mechanical properties of FDM 3D printed samples more than those of injection moulding samples.

Abstract

Acrylonitrile butadiene styrene (ABS) nanocomposites with organic modified montmorillonite (OMMT) were prepared by melt intercalation. ABS nanocomposite filaments for fused deposition modeling (FDM) 3D printing were produced by a single screw extruder and printed by a commercial FDM 3D printer. The 3D printed samples were evaluated by tensile, flexural, thermal expansion and dynamic mechanical tests. The structure of nanocomposites were analyzed by TEM and low angle XRD. Results showed that the addition of 5 wt% OMMT improved the tensile strength of 3D printed ABS samples by 43% while the tensile strength of injection moulding ABS samples were improved by 28.9%. It was found that the addition of OMMT significantly increased the tensile modulus, flexural strength, flexural modulus and dynamic mechanical storage modulus, and decreased the linear thermal expansion ratio and the weight loss of TGA. These novel ABS nanocomposites with better mechanical and thermal properties can be promising materials used in FDM 3D printing.

Introduction

Three-dimensional (3D) printing is one of the most versatile and revolutionary additive manufacturing (AM) techniques to create 3D objects with unique structure and diverse properties [1]. Presently, various techniques such as fused deposition modeling (FDM) [2], stereolithography apparatus (SLA) [3], continuous liquid interface production (CLIP) [4], digital light processing (DLP) [5] and selective laser sintering (SLS) [6] have been developed to form stereoscopic objects with complex architecture. In the late 1980s, S. Scott Crump developed FDM 3D printer and it was commercialized by Stratasys in 1990 [7]. Now, FDM has become the most widely used 3D printing method due to its simple-to-use, low-cost and environment-friendly features and is increasingly used in product development, prototyping and manufacturing processes in a variety of industries, including household appliances, automobile, toys, architecture, medical appliances, aircraft and aerospace.

However, the followings limit the application of FDM 3D printing: the mechanical strength of the FDM printed products are usually worse compared with injection moulding due to their weakness points between the layers [8], and also, the thermoplastic materials tend to shrink during the cooling process, resulting in warp of the printed products [9]. To date, the FDM 3D printing has been studied in the fields of building equipments, materials [10], preparation techniques [11] and numerical simulation [12] and attracted more and more interests.

Usually, thermoplastic materials like ABS [13], [14], nylon [7], [15], polylactic acid (PLA) [16] and their blends [17] are used for FDM 3D printer. To enhance the mechanical properties of 3D printed thermoplastics, fiber-reinforced composites were used. However, addition of fibers often result in that the composites are susceptible to fracture during extrusion. Special additives may be necessary in the extrusion to help produce continuous and homogeneous filaments [18].

In recent years, the emergence of nanocomposites has attracted great interest amongst researchers. By using small volume fractions of nano-additives, mechanical properties [19], [20], heat distortion temperature [21], [22] and thermal stability [23], [24] of a polymer matrix can be improved. Thereinto, polymer/layered silicate (PLS) nanocomposites showed significant improvement in the properties of polymer matrix. Numerous studies reported the PLS nanocomposites exhibited better mechanical property, including dynamic mechanical [25], tensile [26], and flexural properties [21] than that of polymer matrix. Wang et al. [27] studied the thermal properties of ABS/montmorillonite nanocomposite. They observed that the intercalated-exfoliated structure was obtained and the thermal stability of ABS was improved by only 5 wt% of organ-montmorillonite. Lately, Yeh et al. [28] studied the tensile strength of ABS/organoclay nanocomposites, and found that the tensile strength can be improved 15% by adding 3 wt% of organoclay only.

Nowadays, various nanoreinforcements have been used in 3D printed materials, including nanocrystalline cellulose (NCC) [29], SiO2 [30], [31] and layered silicate [32], [33]. However, most of them were SLA 3D printed materials. FDM 3D printed nanocomposites have not been fully studied. In this work, FDM 3D printed nanocomposites were prepared. ABS nanocomposite samples were printed by a commercial FDM 3D printer. The mechanical properties of 3D printed nanocomposites samples were evaluated and compared to those of injection moulding samples. The thermal properties of ABS nanocomposites were also studied. It was found that the polymer nanocomposites could be promising high performance FDM 3D printed materials.

Section snippets

Materials

The pristine montmorillonite was purchased from Nanocor, trade name as PGW, its CEC is 145 ± 10%meq/100 g. Organic modifier, benzyldimethylhexadecylammonium chloride (HDBAC) was bought from Aladdin Industrial Inc., China. The chemical structure of HDBAC is shown in Fig. 1. ABS pellets, trade name as PA-705, was supplied by Qimei Stock Company, China.

Modification of pristine clay

According to Pinnavaia's [34], [35] method, 10 g of pristine clay was dispersed into 500 mL of distilled water at 60 °C and suspension was obtained.

Clay dispersion and morphology

Low angle X-ray diffraction (XRD) was used to determine the microstructure of the clay and its nanocomposites. The XRD patterns of pristine montmorillonite, OMMT and its nanocomposites are shown in Fig. 5. For pristine montmorillonite, a diffraction peak around 8.1° was observed, indicating a d-spacing of 1.27 nm. As for OMMT, an obvious diffraction peak at 4.4° was observed, corresponding to a d-spacing of 2.3 nm. This observation indicated that the pristine montmorillonite was modified by

Conclusions

A novel ABS/OMMT filaments used for FDM 3D printer were prepared by melt extrusion. First, pristine clay were organic modified by benzyldimethylhexadecylammonium chloride. The low angle XRD the TEM results showed that intercalated structure of ABS/OMMT structure were obtained. Second, different amount of OMMT were mixed with ABS pellets by a twin screw extruder and corresponding filament was prepared by single screw extruder. The tensile strength of ABS/OMMT nanocomposites prepared by FDM 3D

Acknowledgment

This research was financially supported by the National Natural Science Foundation of China (Grant No.: U1205114), the Natural Science Foundation of Fujian Province (Grant No.: 2014J01217 and 2015H0047), and the “Strategic Priority Research Program” of the Chinese Academy of Sciences (Grant No.: XDA09020301).

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