Abstract
Many engineering designs focus on the production of durable, ergonomic, and economical new materials. In today’s world where natural resources are rapidly decreasing, recycling waste materials is of great importance. As a result of the bending test, the sample’s return to its original dimensions shows the plastic feature of the material. It was observed that the tensile strength can be increased if the speed of the injection machine is well adjusted in the production of tensile strength testing samples. There was an increase in the screw tensile strength of the samples and the joint hardness strength. Thermogravimetric analysis (TGA) showed that the reference samples were completely crumbled around 480 °C, and it was observed that only quartz remained from the input materials. Differential scanning calorimetry (DSC) showed that the peak point in the reference sample was at the heat flow rate of 29 m/W, while it was 18 to 19 m/W in the doped groups. Melting temperature was observed in the range of 125 to 135 °C in all groups. The mechanical properties of the quartz-substituted samples increased compared to the reference sample. It was observed that the quartz and wood powder contained in the mixture worked in harmony.
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Wood and Quartz Substituted Composite Material Characteristics
Korkmaz Yıldırım a,* and Yüksel Furkan Yıldırım b
Many engineering designs focus on the production of durable, ergonomic, and economical new materials. In today’s world where natural resources are rapidly decreasing, recycling waste materials is of great importance. As a result of the bending test, the sample’s return to its original dimensions shows the plastic feature of the material. It was observed that the tensile strength can be increased if the speed of the injection machine is well adjusted in the production of tensile strength testing samples. There was an increase in the screw tensile strength of the samples and the joint hardness strength. Thermogravimetric analysis (TGA) showed that the reference samples were completely crumbled around 480 °C, and it was observed that only quartz remained from the input materials. Differential scanning calorimetry (DSC) showed that the peak point in the reference sample was at the heat flow rate of 29 m/W, while it was 18 to 19 m/W in the doped groups. Melting temperature was observed in the range of 125 to 135 °C in all groups. The mechanical properties of the quartz-substituted samples increased compared to the reference sample. It was observed that the quartz and wood powder contained in the mixture worked in harmony.
Keywords: Quartz; Wood powder; Composite material; Bending; Injection
Contact information: a: University of Aydın Adnan Menderes, Aydın Vocational School, Efeler, Aydın, Turkey; b: University of Beykent, Beykent Vocational School, Beylikdüzü, İstanbul, Turkey;
*Corresponding author: korkmazy54@gmail.com
INTRODUCTION
Plastic composite products obtained from thermoplastic materials by various production methods in recent years have been used in many fields, such as the automotive industry, electronic home appliances, computer systems, white goods production, space technologies, and even artistic equipment. These materials can be formed easily; they are of low density compared to metals and their superior surface quality and resistance to corrosion have important effects on the tendency of interests towards plastic.
In a world where limited natural resources are gradually decreasing, it is important to recycle waste materials into production. Loss and waste material arise due to the unique working and production systems of each sector. Today, with the decrease of natural resources, it is of great significance to regain waste materials by using recycling systems.
A composite material contains phases that are separated from each other by their form and chemical composition and are basically insoluble in each other, such that there is a mixture or combination of two or more micro or macro components (Erol 2007). The composite material often consists of only two phases. The first phase, called the matrix, usually wraps the other phase and helps to increase the strength by providing continuity. Carbon fiber-reinforced composite materials, glass fiber-reinforced composite materials, car tires, plastics, ceramics, and concrete can be given as examples of composite materials. Concrete is an example of a large-particle composite known as both a matrix and ceramic.
Many engineering designs appear because of the necessity of production of new materials. Strength, ease of use, lightness, and being economical are the main objectives of the new material. The purpose of the formation of nanocomposite materials is to enable the production of new materials that work on the nano-sized molecule-based materials. When the molecular structure it contains is considered, composite materials are divided into three classes: polymeric, ceramic, and metallic. Calcium carbonate is the most commonly used filling material with polyester resin systems. In nature, it is found in the form of chalk, limestone, marble, and travertine and may contain small amounts of other minerals (Feldman 1987). In terms of weight, it is the most important filling material added to ground calcium carbonate plastics. Its finely ground variety is also used especially in polyvinyl chloride (PVC). Calcium carbonate helps both to reduce costs and to increase physical and mechanical properties (Feldman 1987).
It is thought that there are three main ways to reduce costs by adding fillers to plastics: (1) using two different materials together, (2) strengthening with fiber materials, and (3) using polymers such as polyethylene and polypropylene with minerals such as calcium carbonate (marble powder).
The cheapest and most used strategy is to create new compounds with minerals. For example, although the increase in polymer usage has slowed down in the USA, the use of minerals in the polymer industry is increasing. In Western Europe, the use of minerals in the polymer sector also rose from 278,000 tons in 1972 to 650,000 tons in 1985, whereas the average annual polymer use increased 7% (DPT 1996).
As previously mentioned, the use of minerals, one of the most common ways to reduce costs, naturally has brought some problems. There is a difference in surface tension between polymers that are organic materials and minerals that are inorganic. For this reason, minerals are coated to obtain better physical values. Today, over 100 known types of surface coatings are made. The surface coating commonly used in CaCO3 is made with stearic acid (DPT 1996). Nanocomposites are materials formed by the dispersion of nanometer (10-9 micron)-sized particles in a matrix (Bağcı 2006). In addition to polymer-based matrices, metal and ceramic-derived materials are also used as matrices in composite materials. Although other matrices are used, 90% of composite materials are produced with polymer-based matrices (Bağcı 2006). Because the usage areas of polymers has increased by diversifying, it has become important to develop polymers that provide the mechanical, thermal, and electrical properties required by their use or to bring the existing polymers to the desired properties with additives, and studies in this direction have increased (Tavman and Turgut 2006; Swoboda et al. 2008). Due to the nanometric dimensions of the filling particles, nanocomposites have high area/volume ratios and even at low clay densities, significant increases in physical and mechanical properties can be seen because the interaction area between phases is large (Yılmaz Bayhan 2006).
The combination of melt blending, extrusion, and compression molding methods is generally preferred by many researchers. The prerequisite for obtaining the desired polymer matrix nanocomposite sample is the regular distribution of the particles in the matrix (Tavman and Turgut 2006). Polymers’ ease of processing, mechanical behavior, flexible structure, and low density are important advantages (Şahmetlioğlu et al. 2007).
In Toyota research laboratories, for the first time, clay-polymer nanocomposites combined with polymerization have shown far superior mechanical and thermal properties than organic and mineral materials (İsçi 2007). As a result of many studies, polymeric nanocomposites have started to be used in automobiles today. Such materials are 10 times lighter and 10 times stronger than traditional talc filling composites in materials with low filler content. This important feature makes these materials suitable for automotive manufacturing (Yılmaz Bayhan 2006).
Polymer composite materials are engineering products formed by connecting many monomers to each other. This new material, which is formed when the fibers of woody and annual plants and flour (powders) of woody products are combined with polymer thermoplastics, is called a wood-plastic composite. Wood fiber or dust ratio should be more than 50%. The properties of wood-plastics are constituted by the used wood/fiber structure, molecular weight of thermoplastic polymer, additives, and adaptive substances (Mengeloğlu 2006).
In wood-plastic composites, the contents can include dust of wood materials or by-products such as compacted medium-density fiberboard (MDF) or chipboard. Wood powders, such as wood flour, increase the hardness of the composite material while decreasing its durability (Jeong 2005). Thermoplastic resins (low density and high-density polyethylene and polypropylene) and wood powders are used in the production of wood-plastic composite materials.
In the production of composite materials, cheapness, low density, high strength, low abrasion, and being degradable in nature provide motivations to use lignocellulose-based fibers (Chen 2009). The first wood-plastic composite was produced in 1907 by mixing wood flour and phenolics and was produced and used for commercial use as a gear lever in vehicles in 1916. The market share, which was 2% in 1997, increased to 18% by 2005, and a significant increase was observed in wood-plastic composite production. There are now manufacturers of these products in many parts of the world (Balma 1999; Mengeloğlu 2006; Rowel 2006).
In this study, test samples were produced using a molding method by extruding high-density polyethylene, wood powder (flour), and quartz mineral in certain amounts as thermoplastic materials with 100 bar pressure and 45 s injection loading, and the produced quartz-substituted wood-plastic composite material test samples were mechanically and thermally studied with experiments. The usability of quartz as a raw material was also investigated because the waste materials must be recycled in our world where the original raw materials are being consumed rapidly.
EXPERIMENTAL
Materials
Mineral aggregate quartz
Quartz as a filling material is preferred because it gives rigidity and high strength to the polymer concrete it is used in; this is due to its high hardness. The chemical and physical technical properties of the quartz aggregate used in the study are shown in Table 1.
Petilen YY I668 (high-density polyethylene) (HDPE)
The PETILEN YY I668 is a product produced in accordance with the injection molding technique, with high density and narrow molecular weight distribution as per ASTM D618-96 (1998). It is an ideal material for the production of rigid and flexible products in injection molding applications.
The injection molding method was used. Recommended processing conditions were in the range of 200 to 260 °C, and the technical features of the product used are given in Table 1.
Table 1. Technical Specifications of Thermoplastic Material and Quartz Mineral
Wood powder
Within the scope of the study, machine residual dust belonging to the remaining wood and wood products were used as waste material in the furniture sector. Mixing ratios of the powders were not fixed; sawdust and dust from pine, beech, poplar, MDF, chipboard, wood scraps, and some edge bands were collected. After this waste material was dried in the oven, it was ground and sieved through a sieve with a thickness of 200-mesh and a powder material was produced in the form of flour (Horta et al. 2017). When the values of the substances in this mixture were analyzed, the abundance of cellulose material were seen. The properties of the prepared wood powder (flour) are given in Table 2.
Table 2. Technical Specifications for Wood Powder (Flour)
Methods
Preparation of test samples
High-density polyethylene material from thermoplastics, 200-mesh fine wood powder (flour), which is industrial waste, and quartz mineral with a fineness of less than 0.100 µ (micrometers), were prepared by the method of displacement at certain rates. Denomination and mixing ratios of the experimental groups prepared for quartz, wood, and polyethylene-added composite materials are given in Table 3.
Table 3. Mixing Ratios of Experimental Sample Groups
The materials prepared separately with each recipe of thermoplastic, wood, and quartz materials were mixed in the mixer (KMİX200; Küçükoğlu Machine, Izmir, Turkey).
All of the materials were brought together by blending them in the extruder machine (Fig. 1) (25/36D Extruder; Sarem Machine, Izmir, Turkey)
Fig. 1. Combining materials in the extruder machine
The extrusion process has played a major role in the development of the polymer processing industry. The most striking feature of the extrusion process is a cylindrical barrel and a screw rotating inside and this process is the most important polymer processing technique today. Approximately 60% of the polymers are processed by this method and become the final product (Bodur 2010). The samples that were brought together in the extruder machine were granulated in the crushing machine (Fig. 2) (SG-21EB; Hastek Machine, Aydin, Turkey).
The material, which became granular for the injection machine, was kept in the oven at a certain temperature and reduced in moisture content. To form test samples, for mechanical and thermal testing with the ready material, 100 bar pressure and 45 s injection loading were applied in the injection machine and the test samples were produced by molding method (Fig. 3). Four groups of material production happened under the same conditions.
Fig. 2. Breaking the material in the crushing machine
Fig. 3. Production of test samples with molding method
Experimental process
Quartz, 200-mesh fine wood flour (powder), and thermoplastic product (high-density polyethylene) were prepared by the replacement method in certain mixtures, and with the prepared material, the extruder and test bars used in the tests after the injection processes were produced (Figs. 4 and 5). Bending, tensile strength, screw pulling, and Janka hardness tests were applied to the test samples in accordance with the standards and the results and graphics of the tests are interpreted below according to ASTM D790 (2007), ASTM D638-99 (2007), ASTM D1037 (2012), and TS EN 323 (1999).
In addition, thermogravimetric analysis (TGA) (Pyris 6 Thermogravimetric Analyzer; Perkin Elmer, Mugla, Turkey), differential scanning calorimetry (DSC) (DSC 8500 is a double-furnace DSC; PerkinElmer, Mugla, Turkey), and scanning electron microscopy (SEM) (Model; Jeol Jsm-7600f SEM; JEOL LTD., Muğla, Turkey) analyses were performed on the composite elements produced as thermal tests.
Fig. 4. Experimental process application images bending test and tensile strength test
Fig. 5. Experimental process application images screw pull resistance test and Janka hardness resistance test
RESULTS AND DISCUSSION
Bending Test
It was observed that the bending resistance of the reference sample was 25.4 N/mm2. In the sample PEWQ-1, there was an increase of 19.8% in the bending resistance compared to the reference sample. In the sample PEWQ-2, the bending resistance increased 3.6% compared to the PEWQ-1 group when the wood dust was less and the quartz mineral was high. In the sample PEWQ-3, the increase at the level of 3% continued in the maximum force and bending resistance compared to the group PEWQ-2 when the wood dust was low and the quartz mineral was high.
Tensile Strength Test
It was observed that the tensile strength of the reference sample was at the level of 19,700 N/mm2. In the sample PEWQ-1, there was a decrease in the tensile strength compared to the reference sample, and accordingly, the tensile strength decreased at the level of 29.3%. In the sample PEWQ-2, there was a decrease in the tensile strength and accordingly an increase of 3.41% compared to the group PEWQ-1. In the sample PEWQ-3, there was a slight increase in the tensile strength compared to the sample PEWQ-2 and accordingly the tensile strength increased 1.12%.
Screw Pull Resistance Test
It was observed that the threading strength obtained by the reference sample was at the level of 109.8 N/mm2. In the sample PEWQ-1, there was a decrease in the threading strength compared to the reference sample, and accordingly, the threading strength was at the level of 103.0 N/mm2. In the sample PEWQ-2, there was an increase in the threading strength and accordingly, the threading strength increased 2.8% compared to the group PEWQ-1. In the sample PEWQ-3, there was an increase of 0.5% in the threading resistance compared to the sample PEWQ-2 and accordingly threading strength increased proportionally with the increase of quartz.
Janka Hardness Resistance Test
It was observed that the Janka hardness value taken by the reference sample was at the level of 3