Preparation and Characterization of Polymer Blend and Nano Composite Materials Based on PMMA Used for Bone Tissue Regeneration

Acrylic bone cement, PMMA, tensile strength, Young’s modulus. As the elderly population increases, the need for bone loss treatments is increasing. Vital substances used in such treatments are required to continue for a longer period and work more effectively. The particularly important biological material is poly methyl methacrylate (PMMA) bone cement, which is widely used in damaged bone replacement surgery. So, this study focused on the role of added some nanoparticles consist of zirconia (ZrO2), and magnesia (MgO) on the binary polymeric blend (Acrylic bone cement: 15% PMMA) for a bone scaffold. Where, ZrO2 and MgO nanoparticle was added with selected weight percentages (0, 0.5, 1, 1.5 and 2 wt.%), which were added to the polymer blend matrix. Some mechanical properties were studied including the tensile strength and young modulus for all the prepared samples. The chemical bonding of nanoparticles and synthetic binary polymeric blend composites was evaluated by Fourier Transform Infrared (FTIR) spectroscopy. Tensile strength and young modulus of binary polymeric blend reinforced with 1.5 wt.% ZrO2, and 1 wt.% MgO, significantly increased. The surface morphology of the fracture surface of tensile specimens was examined by Scanning electron microscope (SEM). The SEM images confirmed that the homogenous distribution of nanoparticles (ZrO2, and MgO) within the polymeric blend matrix. How to cite this article: S. A. Kadhum Alsaedi, S. I. Salih, and F. A. Hashim, “Preparation and characterization of polymer blend and nano composite materials based on PMMA used for bone tissue regeneration,” Engineering and Technology Journal, Vol. 38, Part A, No. 04, pp. 501-509, 2020. DOI: https://doi.org/10.30684/etj.v38i4A.383 Engineering and Technology Journal Vol. 38, Part A, (2020), No. 04, Pages 501-509


Introduction
Bones play a key role in our bodies, allowing daily tasks to be performed. They are also important for storing minerals and producing red blood cells. If bones fail to repair due to significant injury or disease, replacement surgery may be conducted to replace the bone tumor with a bone repair (i.e., Bone, as a functionally smart tissue, is capable of healing and remodeling in the case of limited bone defects) [1,2]. In the manufacturing of scaffolds, both natural and synthetic biomaterials are used. Systems for bone tissue engineering include bone regeneration following tissue loss owing to degenerative surgical procedures. In the condition of disease with degeneration risk, the therapy requires the surgical removal of the tumor bone tissue and the bone defect can be filled with bone graft material in the second phase [3]. Polymethyl methacrylate (PMMA) is a non-adhesive acrylic polymer, widely used as bone cement for implants in orthopedics. Chanley introduced orthopedic use of PMMA cement in the early 1960s and this was the first cement to be used in spine applications. PMMA has been extensively studied as bone cement for over 40 years and widely suitable are many injectable PMMA cement formulations engineered for vertebral body applications. Because of its desirable features, PMMA bone cement occupied an uncomfortable room for several centuries, such as appropriate strength to provide mechanical stability, moldable to fill complicated flaws, low cost and authorized by Food and Drug Administration (FDA) [4,5]. A polymer mixture is a component of a material category where two or more polymers are combined to form a fresh material with distinct physical characteristics. They combine the characteristics of the alloy subsystems in a beneficial way. In some instances the properties of the polymer blends are superior to those of their components. Polymer blending is a technological way to provide materials with a complete set of desired special properties at the lowest price, such as a combination of toughness and strength, and solvent resistance. One of the most common methods for developing new polymeric materials is blending polymer [6]. In tissue engineering, biopolymer composites are of excellent importance for medical applications because they provide a favorable environment for cell growth and differentiation [7]. Recently, due to its excellent biocompatibility, Nano ZrO 2 has received great attention. ZrO 2 classification as a filler was based on this filler's characteristics, which can enhance the mechanical characteristics of acrylic resins. ZrO 2 has a range of useful characteristics, including great toughness and mechanical strength, resistance to abrasion and corrosion, and biocompatibility. Nano ZrO 2 has good mechanical characteristics that enable it to resist the propagation of cracks, and it is known to have the greatest oxide hardness [8]. Magnesia (MgO) is also another bioactive material and an appropriate additive to PMMA since the adhesion of osteoblasts to cement involving magnesium oxide was significantly greater than the adhesion to PMMA alone (P<0.001) without significant changes in mechanical strength [9]. A review by Karageorgiou and Kapalan [10] revealed different types of bone with their required mechanical properties. Cortical (mid-femoral), depending on the direction and type of load, has a strength ranging from 33-193 MPa with elasticity modulus from 3 to 17 GPa, while trabecular (Proximal femoral) has 6. The main objective of this study was to improve the mechanical properties of the polymeric blend that's reinforced with nanoparticle (ZrO 2 , and MgO) according to the standards of bone tissue engineering.

I. Materials used
Acrylic bone cement for bone scaffold, as resin material manufactured by (the company of Re-Acromed) which was supply from UAE. Acrylic bone cement comprises two parts, one is powder and the other is a liquid. The powder is composed of (PMMA), and the liquid composition is (methyl methacrylate, dimethylparatoluidine, and ethylene glycoldi methacrylate). Self-Curing Polymethyl methacrylate (PMMA) is another type of acrylic resin manufactured by (ORT-365) was supply from Ankara. It comprises two parts, one of them is a transparent viscous liquid and the other is a paste. The transparent viscous liquid is composed of (MMA) and a paste is composed of (DIBENZOYL). Tables 1 and Table 2 show the technical information of acrylic bone cement and PMMA respectively, according to the product company.  Two types of nanoparticles as reinforcement materials have been used. These nanoparticles are the zirconium oxide (ZrO 2 ), which was obtained from Honwu Nanometer material company in china with purity (99.9%) has a white color, with an average diameter (50.65 nm). It is a type of yttria (Y 2 O 3 ) stabilized zirconia and MgO powder, which was obtained from Beijing DK Nanotechnology Company in China with purity (99.9%) has a white color, with an average diameter (68.83 nm).

II. Preparation of polymer blends and composite samples
To prepare polymer, blends were down by hand lay-up molding by using two different types of PMMA material. Acrylic bone cement specimens were prepared by (5 wt.) of powders with (3.5 wt.) of the liquid part of methyl methacrylate monomer. According to the manufacturer instructions of the second material (PMMA), the mixing ratio of acrylic resin and hardener is (100/2). So on, the control group was prepared by the weighed amount of acrylic bone cement as a basic substance and blended with PMMA at 15% weight percentage, and were mixed manually until the mixture gets in homogenous form. To get the final standardized samples, the blend was poured into the mold. Then, the mixture was left in the mold at room temperature for 48 hours to solidify. After that, the casting sample is placed inside an oven at 50 ºC for 3 hours. Finally, to complete polymerization, it was left for 72 hours at room temperature.

III. Prepared composites
The weights of the reinforcement components depend on the appropriate selection ratio of the weight fractions of the strengthening materials (Zirconia, and magnesia) as the nanoparticle's powders were calculated by utilizing electronic sensitive balance, depending on the matrix material's total weight (binary polymeric blend) which is contained on (Acrylic bone cement: 15% PMMA). The reinforcement materials (Zirconia, or magnesia) were mixed in individual form with a binary polymer blend material according to the selection ratio of reinforcement materials followed by heat treatment at 55 °C for 3 hours to accomplish polymerization and to remove any residual stress resulting from de-molding of the samples into the cavity of the metal mold.

I. Fourier transform infrared radiation (FTIR) spectroscopy test
According to the international standard (ASTM E1252-98) [13], the Fourier Transform Infrared Radiation (FTIR) spectroscopy test was carried out by test instrument, manufactured by (Bruker Company in Germany), kind (TENSOR-27). It is equipped with a room temperature DTGS detector, mid-Infrared spectrum was used within a range of (4000 to 400) cm -1 and a KBr beam splitter.

II. Mechanical tests
The tension test was performed according to ASTM D638 [14,15]. The sample length used is (165 mm) and (7 mm thickness). A universal testing machine (UTM) performed the tensile test with a load capability of 50 KN and a cross-head velocity of (5 mm/min). Through tensile, evaluation and comparison of modulus of elasticity (Young's modulus) and ultimate strength were made for materials with different fillers weight fractions.  The infrared spectra of (control sample) binary polymer blend (Acrylic bone cement: 15 % PMMA), and polymer blend composites reinforced with different ratios of ZrO 2 nanoparticles are shown in Figure 2. All the features of polymer blend vibration bands of (control sample), shown in Figure 1, are presented in infrared spectra of ((Acrylic bone cement: 15 % PMMA): X % ZrO 2 ) composites specimens ( Figure 2 In infrared spectra for ((Acrylic bone cement: 15% PMMA): X% ZrO 2 ) composites specimens no new peaks or peak shifts were observed. This is due to having to find a physical bond and absent any cross-linking in these specimens. There is a clear decrease in peak intensity for all the characteristic peaks at 0.5 wt. % ZrO 2 and then increase again with further increase in ZrO 2 content in PMMA composites specimens.   . When further addition of the nanoparticles (ZrO 2 , and MgO) increases, seems to reduce the interfacial adhesion between the components, and a non-homogenous distribution led to composites with lower elastic modulus. Regarding, the Nano hybrid composites, the addition of the filler of (2 wt.% ZrO 2 ), and (<1.5 wt.% MgO) caused a reduction in tensile strength. This reduction was due to the presence of particlematrix interfacial defects and the presence of Vander Waals forces causes the dispersion process to be ineffective. Furthermore, the existence of agglomerated fillers that form loosely connected clusters that affect the crack propagation mode decreases the tensile strength [21]. The size, amount and dispersion of the reinforcement phase and interfacial bonding between the components of composite influence the mechanical and physical properties directly. They have influence on the microstructure morphology of composites as well. Thus, in an attempt to correlate the mechanical characteristics of polymer blending samples with their microstructural morphologies, the scanning of electron microscopy (SEM) micrograph analyses were conducted on the fracture surfaces (at magnification 1000X). The fracture surface morphology for binary polymer mixing (control sample) and for polymer Nano composite of ((Acrylic bone cement: 15% PMMA):1.5 % ZrO 2 ), and ((Acrylic bone cement: 15% PMMA): 1 % MgO), were characterized. Homogenous morphologies were observed, all microstructural morphologies showed up as co-continuous structures, making it more difficult to distinguish between individual polymers in the composites of these polymeric blends. These fracture surface morphologies, shown in Figures 8 a, b, and c, show stronger interfacial adherence between composite specimen components with additional nano-sized reinforcing materials (1.5% ZrO 2 and 1% MgO) to binary polymeric blend respectively. However, the fracture surface of polymeric composites was rough and uneven with ductile dimples pattern. Also, the morphology of fracture surface exhibited lamellar steps with relatively homogenous size and distribution, characteristics of ductile fracture [22]. Besides, there was no wide agglomeration of these nanoparticles showing the uniform distribution of particles. It was also observed that the microscopic structure of the fracture surface morphology for most of the nanoparticles are embedded inside the matrix material as an integral part of the base material structure, indicating good compatibility between the matrix material and leads to the formation of strong physical bonding (strong interfacial regions) between the nanoparticles and polymeric blending matrix [3,23]. It was also observed that the microscopic structure of the fracture surface morphology for most of the nanoparticles are embedded inside the matrix material as an integral part of the base material structure, indicating good compatibility between the matrix material, and lead to the formation of strong physical bonding (strong interfacial regions) between the nanoparticles and polymeric blending matrix [3,23].

Conclusions
The following comments could be taken from this study : The addition of ZrO 2 nanoparticles to polymer blend (Acrylic bone cement: 15% PMMA) gave better mechanical properties (tensile strength and young modulus) as compared with other reinforcement nanoparticle materials (MgO) used in this study. Also, when the nanoparticles added to a certain limit (1.5 wt.% ZrO 2 ), and (1 wt.% MgO) enhanced the tensile strength and Young modulus of polymeric blend Nano composites samples. Finally, when the nanoparticle added more than this a certain limit in composite led to a reduction in the mechanical properties, but they retained in these properties better than they are in the polymer blend as a base material. So, these samples may be from the promising materials to achieve the properties required for bone scaffold applications.