Elsevier

Polymer Testing

Volume 79, October 2019, 106023
Polymer Testing

Mechanical properties and antibacterial performance of PMMA toughened with acrylic rubber containing 2-hydroxypropyl-3-piperazinyl-quinoline carboxylic acid methacrylate (HPQM) and HPQM absorbed on TiO2 particles

https://doi.org/10.1016/j.polymertesting.2019.106023Get rights and content

Highlights

  • The mechanical properties and antibacterial performance of AR/PMMA blends increase with increasing HPQM content.

  • ARHPQM on TiO2/PMMA blends showed synergistically antibacterial performance for the co-antibacterial agent of HPQM/TiO2.

  • HPQM absorbing on TiO2 particles was an effective co-antibacterial agent for all AR/PMMA blends.

Abstract

Materials behaviors and antibacterial performances of Acrylic rubber (AR)/Poly (methyl methacrylate) (PMMA) blends doped with 2-Hydroxypropyl-3-piperazinyl-quinoline carboxylic acid methacrylate (HPQM) and HPQM absorbed on titanium dioxide (HPQM on TiO2) particles were examined. The results revealed that mechanical properties and antibacterial performance of AR/PMMA blends tended to increase with increasing HPQM content, especially at 50 wt% of AR content; however, the antibacterial activity of AR doped with HPQM (ARHPQM) blended with PMMA was retarded by the crosslink structure in the AR phase. Our results suggest that the loading of AR at 50 wt% was found to be preferable, with a recommended content of HPQM of 1.5 pph to be added to this blend system. The mechanical properties of TiO2 doped with HPQM before doping on AR (ARHPQM on TiO2)/PMMA blends were significantly higher than those of the AR/PMMA and AR doped with TiO2 (ARTiO2)/PMMA blends with 30–50 wt% of AR content. ARHPQM on TiO2/PMMA blends showed synergistically antibacterial performance of HPQM and TiO2. It could be concluded that HPQM absorbing on TiO2 particles was an effective co-antibacterial agent for all AR/PMMA blend whereas HPQM alone was recommended for AR/PMMA blends at 50 wt% of AR.

Introduction

Poly(methyl methacrylate) (PMMA) is an amorphous polymer with a glass transition temperature (Tg) of about 120 °C [1]. It is widely used due to low cost, high biocompatibility, easy handling, and processing [2]. However, PMMA still has insufficient surface hardness, low strength and is brittle due to amorphous behavior. It is easily broken during application. Therefore, PMMA is usually incorporated with other fillers, such as, rubber, metal, or ceramic to improve its impact strength and fracture toughness. An et al. [3] studied the effect of acrylic rubber (AR) contents on PMMA toughness and reported that the impact strength, tensile toughness, and elongation at break of PMMA increased gradually with increasing AR concentration, whereas tensile modulus and tensile strength decreased.

PMMA is mostly used for specific applications, such as dentistry, sensors, optics, and conductivity polymers [4]. In particular, dentistry appliances made from PMMA, such as artificial teeth, retainers, dental implants, and orthodontic appliances are usually applied in oral cavities [[5], [6], [7], [8]]. Bacterial cells in the oral cavity can adhere and accumulate on their surfaces [9], which is considered the main cause of poor hygiene. Many studies [[10], [11], [12], [13], [14]] focus on the use of inorganic compounds, such as titanium, silica, silver, copper, selenium, gold, zirconia, and alumina to improve the antibacterial performance of the polymer. Work by Alrahlah et al. [15] observed antibacterial behavior of titanium dioxide in PMMA and found that the bacteria cells decreased with increasing titanium dioxide content. Moreover, Verdier et al. [16] studied the effect of the specific experiment condition on the antibacterial performance of the acrylic resin. It was found that the number of bacterial colonies exposed to TiO2 decreased because of the physical contact between bacteria cells and TiO2 particles. Besides the use of inorganic compounds as the antibacterial agents, organic compounds are also considered to be used as the antibacterial agents. Organic antibacterial agents can be produced from plant extraction or fungal metabolites, such as, C. sempervirens, wort, tree tea oil, green tea, and 2-Hydroxypropyl-3-piperazinyl-quinoline carboxylic acid methacrylate (HPQM) [[17], [18], [19]].

HPQM is an organic antibacterial agent. It has been used as a water-based solution, consisting of 10 ± 1 wt% of HPQM; 2 ± 1 wt% of sodium hydroxide; <1 wt% of polyoxyethylene nonyl phenyl ether and 87 ± 1 wt% of deionized water [20]. The studies of Taptim and Sombatsompop [21] and Jai-eau et al. [22] reported that HPQM inhibits the growth of both Gram-positive and Gram-negative bacteria. HPQM molecules can penetrate into the bacteria cells, causing the inhibition of DNA synthesis and releasing their dissociated proton inside the cells [23], resulting in cell death. Work by Eksirinimitr et al. [24] demonstrated the effects of simulated conditions, including water and detergent washing, and UV radiation exposure, on the antibacterial performance of polypropylene and polystyrene incorporated with HPQM. Their results found that HPQM molecules inhibit bacteria cell growth by the interaction with water molecules, according to the concentration gradient theory.

Based on the literature review, the antibacterial mechanisms of TiO2 particles and HPQM molecules are different. TiO2 particles inhibit the bacterial cell growth by the reactive oxygen species (ROS) generated via photocatalytic process, while HPQM molecules directly destroy the bacterial cells. Therefore, it was thought that incorporations of TiO2 particles and HPQM in polymers could synergistically improve the antibacterial performance and this has become the significance of this present work. The main aims of this work were to synthesize HPQM absorbed on TiO2 and to investigate the mechanical properties and HPQM-absorbed TiO2 particle which were incorporated into the AR and PMMA matrix before and after ultraviolet (UV) exposure for 24 h. In addition, the antibacterial performance of these blends against Escherichia coli and Staphylococcus aureus was qualitatively and quantitatively determined by disk diffusion assay and Japan Industrial Standard (JIS) Z2801 specifications, respectively.

Section snippets

Chemicals and materials

Acrylic rubber (AR) grade AR 71 and poly (methyl methacrylate) (PMMA) grade MD 001 were supplied from Zeon Chemicals (Thailand) Co., Ltd. and Mitsubishi Rayon Co., Ltd., respectively. The rutile titanium dioxide (TiO2) particles act as a carrier and an antibacterial agent with an average primary particle size of 11.2 μm was acquired from Chanjao Longevity Co., Ltd. A 2-hydroxypropyl-3-piperazinyl-quinoline carboxylic acid methacrylate (HPQM) grade BA 101 as an antibacterial agent (Fig. 1) was

Tensile properties

The results of tensile modulus, tensile strength, and elongation at break of AR/PMMA and ARHPQM/PMMA blends as a function of HPQM content are given in Fig. 4. Fig. 4a and b demonstrate the tensile modulus and tensile strength of the blends, respectively. Considering the blends without HPQM, it was found that the tensile modulus and tensile strength decreased with increasing AR content. This was associated with the influence of flexibility of AR phase, this being described in our previous study [

Conclusions

  • Tensile properties of AR/PMMA blends generally decreased with increasing AR content. Meanwhile, the impact strength of AR/PMMA blends increased with increasing AR content. Moreover, the increasing AR content enhanced the antibacterial performance of AR/PMMA blends.

  • The increasing of HPQM content increased tensile properties and impact strength, particularly for ARHPQM/PMMA blend with high AR content (50 wt%). HPQM solution could form a crosslinking structure in the AR phase which enhanced the

Conflicts of interest

The authors declare no conflict of interest.

Acknowledgments

The authors would like to thank the Office of the Higher Education Commission (OHEC) under the National Research University (NRU) Program and the Thailand Research Fund (TRF) under the Royal Golden Jubilee Ph.D. Program (PHD/0151/2557). The authors are grateful to the College of Industrial Technology, King Mongkut's University of Technology North Bangkok, for supplying laboratory facilities.

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