The authors acknowledge the support of the LUT RESOURCE (Resource efficient production processes and value chains) research platform coordinated by LUT University and the by the Life IP on waste&#8212;Towards a circular economy in Finland (LIFE-IP CIRCWASTE-FINLAND) project (LIFE 15 IPE FI 004). Funding for the project was received from the EU Life Integrated program, companies, and cities.

1. Identification and pre-treatment
<ol>
	<li>Identify polymers in plastic with the portable near-infrared (NIR) spectroscopy tool in the spectral range of 1600&#8211;2400 nm. Contact the polymer with spectroscopy tool and determine the polymer by the measured reflectance.
	<ol>
		<li>According to the identification curve of spectroscopy, analyze the identification results from the screen in the laboratory.</li>
	</ol>
	</li>
	<li>Based on the identification result, sort materials between the polymers and measure their respective weights. 
	NOTE: The material was sorted and weighted according to the measured identification results. Selected polymers for further processing were ABS, PE, and PP with the amounts, 27.1, 14.2, and 44.7 kg, respectively.</li>
	<li>Perform size reduction for the selected plastic materials in laboratory conditions with a crusher apparatus. Place collected and identified materials into the apparatus that crushed materials with the mechanical force of hammer impacts.
	<ol>
		<li>Crush plastic materials using a single-shaft shredding system with a crusher/shredder apparatus equipped with a sieve size varying from 10 to 20 mm.</li>
		<li>Subject the plastic fragments to a low-speed crusher, equipped with a 5 mm sieve. Ensure that the material is homogenous.</li>
	</ol>
	</li>
	<li>Measure the material amounts for composites. Show a recipe as an example and present these materials in the relative amounts of plastic, wood, coupling agent, and lubricant (64, 30, 3, and 3 wt%, respectively). 
	NOTE: Three different composites were studied in this study. The recycled plastic polymers from the CDW were ABS, PP, and PE. The filler of the composite material was wood flour, which was prepared from a dried spruce species (Picea abies) size reduced using crushing equipment and sieved for a homogeneous size (20 mm mesh). Commercial additives of coupling agent and lubricant were used. The compositions and name of the prepared materials are shown in Table 1.</li>
</ol>
<table border="1" fo:keep-together.within-page="1" fo:keep-with-next.within-page="always">
	<tbody>
		<tr>
			<td>Material</td>
			<td>Polymer 
			/ amount</td>
			<td>Wood</td>
			<td>CA</td>
			<td>Lubr</td>
		</tr>
		<tr>
			<td>CDW-ABS</td>
			<td>ABS / 30</td>
			<td>64</td>
			<td>3</td>
			<td>3</td>
		</tr>
		<tr>
			<td>CDW-PP</td>
			<td>PP / 30</td>
			<td>64</td>
			<td>3</td>
			<td>3</td>
		</tr>
		<tr>
			<td>CDW-PE</td>
			<td>PE / 30</td>
			<td>64</td>
			<td>3</td>
			<td>3</td>
		</tr>
	</tbody>
</table>
Table 1: The composition of the studied materials. The name of the sample consists of the included matrix component, recycled acrylonitrile butadiene styrene (ABS), polypropylene (PP), and polyethylene (PE) from the construction and demolition waste (CDW). The amounts of wood, coupling agent (CA) and lubricant (Lubr.) were the same in all samples.
2. Processing of WPC materials with extrusion technology after size reduction treatment
<ol>
	<li>Transfer the identified and pre-treated materials into closer the next (agglomeration) processing step. 
	CAUTION: The plastic material of ABS includes a styrene component. The International Agency for Research on Cancer considers that styrene is &#8220;possibly carcinogenic to humans&#8221;. Therefore, the agglomeration step in action was not included in the filming but its process is outlined in this work. Additionally, only PP or PE polymer was used in the extrusion production during filming.</li>
	<li>Perform agglomeration of the material.
	<ol>
		<li>Mix all components of the process (polymer, wood, coupling agent, and lubricant) in an apparatus that consists of a turbomixer and a cooler. Agglomerate the materials in the turbomixer until the temperature of the materials reached 200 &#176;C. Due to the combined effect of temperature and friction, the granules materials were formed after the treatment process of agglomeration.</li>
		<li>Cool the materials after turbomixer treatment for 4-7 minutes in a cooler apparatus.</li>
	</ol>
	</li>
	<li>Evacuate material from the process and collect up agglomerated material.</li>
	<li>Transfer the agglomeration&#8211;treated materials to the next process step (extrusion).
	<ol>
		<li>Click the control panel of the extrusion machine and check for the correct parameters. The average barrel and tool temperatures varied between 167 and 181 &#176;C, and 183 and 207 &#176;C, respectively. The melt temperature varied between 164 and 177 &#176;C, and the die pressures were between 3.7 and 5.9 MPa. Adjust parameters because recycled materials are heterogeneous, and the process requires professional control.</li>
		<li>Compound the components using a conical counter-rotating twin-screw extruder with 15 kg/h material output. The parameters of the materials are presented in Table 2. After the extrusion process, the profile material of the composite was generated.</li>
	</ol>
	</li>
</ol>
<table border="1" fo:keep-together.within-page="1" fo:keep-with-next.within-page="always">
	<tbody>
		<tr>
			<td>Material</td>
			<td>Barrel T &#176;C</td>
			<td>Tool T &#176;C</td>
			<td>Melt T &#176;C</td>
			<td>Melt 
			Pressure (bar)</td>
			<td>Feeding 
			rate (kg/h)</td>
			<td>Avg.Screw 
			speed (rpm)</td>
		</tr>
		<tr>
			<td>CDW-ABS</td>
			<td>181 &#177; 11.9</td>
			<td>189 &#177; 14.7</td>
			<td>177</td>
			<td>50</td>
			<td>15</td>
			<td>14</td>
		</tr>
		<tr>
			<td>CDW-PP</td>
			<td>170 &#177; 10.4</td>
			<td>207 &#177; 8.62</td>
			<td>164</td>
			<td>37</td>
			<td>15</td>
			<td>15</td>
		</tr>
		<tr>
			<td>CDW-PE</td>
			<td>167 &#177; 8.51</td>
			<td>183 &#177; 10.1</td>
			<td>164</td>
			<td>59</td>
			<td>15</td>
			<td>13</td>
		</tr>
	</tbody>
</table>
Table 2: Processing parameters of the composite materials. (Values after the &#8216;&#177;&#8217;-mark indicate standard deviations. Avg. = average)
3. Sampling of produced materials and analyzes of properties
<ol>
	<li>Prepare samples for mechanical property tests in the laboratory.
	<ol>
		<li>Cut samples from extruded profiles with a machine (i.e., a sliding table saw). Three different size specimens are needed for tests: flexural, tensile, and impact strength.</li>
		<li>Determine the size of test samples according to the applicable standards, based on the recommendation of EN 1553416. According to the standard, test a minimum of five specimens but the number of measurements may be more than five if greater precision of the mean value is required.</li>
	</ol>
	</li>
	<li>Saw test samples from the extruded materials for the flexural property test, according to the standard EN 31017.
	<ol>
		<li>Use a sliding table saw with the following dimensions for the sample: 800 mm x 50 mm x 20 mm (length, width, thickness).</li>
		<li>Manufacture 20 samples for the analysis of flexural properties (strength and modulus).</li>
	</ol>
	</li>
	<li>Saw test samples from the extruded materials for the tensile property test, according to the standard EN ISO 527 218. Use the sliding table saw to cut the material into the following dimensions: 150 mm x 20 mm x 4 mm (length, width, thickness).
	<ol>
		<li>Set the material preforms for machining of a dumb-bell shape via computer numerical control (CNC). The width of the sample at its narrow portion was 10 mm, and the cross-sectional surface area of the sample was 4 mm x 10 mm, where the tensile stress was addressed. The length of the narrow portion was 60 mm, ending in a rounded corner with a radius of 60 mm.</li>
		<li>Make 20 samples for the analysis of tensile properties (strength and modulus).</li>
	</ol>
	</li>
	<li>Saw test samples from the extruded materials for the impact strength test, according to the standard EN ISO 179-119.
	<ol>
		<li>Use the sliding table saw to cut the samples into the following dimensions: 80 mm x 10 mm x 4 mm (length, width, thickness). Make 20 samples for the analysis of impact strength property.</li>
	</ol>
	</li>
	<li>Move the test material into the 23 &#176;C and 50% relative humidity condition chamber, according to standard EN ISO 29120, until a constant mass is reached. Ensure that samples are conditioned before the testing of material properties.</li>
	<li>Perform the tests (flexural, tensile, and impact). Determine the mechanical features of specimens by flexural and tensile strength tests with a testing machine in accordance with the EN 31017 and EN ISO 527-218 standards, respectively.
	<ol>
		<li>Perform flexural strength and modulus test for each of 20 samples, using the testing apparatus. Set flexural test sample at the support of two points and apply a load to the center of sample by clicking Test start in the computer program that controls the testing apparatus, with a pre-load of 15 N and test speed of 10 mm/min. The test stops automatically after recording the result. Remove test sample from the support tools and set a new sample on the tools.
		<ol>
			<li>Repeat procedure until 20 samples were tested and results from the program were registered. The computer program calculates average results from the test. 
			NOTE: The protocol can be paused here while test tools will be changed for the testing apparatus.</li>
		</ol>
		</li>
		<li>Perform tensile strength and modulus test for 20 machined (dumb-bell-shaped) samples. Set the tensile test sample between the test tools and attach pneumatic clamps, which will keep the sample in the tools during the test. Start the test from the computer control panel, with a pre-load of 10 N and test speed of 2 mm/min, and attach an extension meter tool immediately after the test start. 
		NOTE: The extension meter tool measures the tensile modulus from the sample. Each test stopped automatically after its result was recorded.
		<ol>
			<li>Remove the test sample from the tool after each test and set a new sample on the tools. Repeat procedure for all samples. The computer program calculates average result values.</li>
		</ol>
		</li>
		<li>Perform an impact strength test with an impact tester, according to standard EN ISO 179-119. Set the 10 mm x 4 mm size of (width, thickness) sample between the support, reset the force and release the impact hammer of 5 kpcm. 
		NOTE: The impact strength test sample ruptures due to the impact of hammer and the amount of absorbed energy is visible in the tester indicator.
		<ol>
			<li>Record the result and repeat the for the 20 samples, after which the average value of impact strength is calculated. The recorded results were in &#8220;kpcm&#8221; unit, which was changed into joule (J), and the results were presented as a kilojoule per square meter. 
			NOTE: The span between sample support (distance between the lines of the contact the of sample) in the impact strength test was 62 mm or, alternatively, 20x its thickness.</li>
		</ol>
		</li>
	</ol>
	</li>
	<li>Analyze the results from the mechanical tests, which are presented in Figure 1, Figure 2 and Figure 3.</li>
</ol>

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Circwaste-project receives financial support from EU for the production of its material. The views reflected within the content are entirely the project&#8217;s own and the EU commission is not responsible for any use of them.

The mechanical properties of WPC play an important role in deciding the suitability of these products in various applications. WPC consists of three main ingredients: plastic, wood, and additives. The mechanical properties of fiber-based composites depend on the length of the used fiber, where &#8220;critical fiber length&#8221; is the term used to indicate sufficient reinforcement25. In addition to the properties of ingredients, the quality of raw materials is the important factor for the performance of WPC. In this study, in particular, where recycled raw materials were used, a lot of attention was placed on the raw materials. This study used materials sourced from CDW which can vary between construction sites, and this variability is a critical factor in the comparison of different studies. Therefore, material must be studied according to the standardized tests that ensure uniform product quality.
In a flexural test, the WPC material experiences compressive stress at the load-bearing side and correspondingly, tensile stress at the opposite end. The test method is based on the standard of wood-based panels (EN 310), illustrating the flexural properties of an extruded profile in actual use. The flexural test will cause compression (on the upper surface) and tensile (on the underside) stress for the material, therefore it is important that the extruded (hollow) profile is symmetrical. Another test for flexural property (for example, the standard EN ISO 17827), where the dimensions of the sample were smaller, will not yield the real valued for the extrusion profile used but will analyze the property of the material without the effect of a hollow profile. It is important to use a standardized distance between the support spans because this has an influence on the results. The flexural strength depends linearly on the support span, in which an increased support span leads to a proportional decrease of the load28.
Generally, tensile modulus increases with the increasing content PP polymer within wood fiber25. Therefore, we can assume that the composition of materials, including additives such as a coupling agent, were not optimal for this material. The highest variation between the thicknesses of tensile test samples was 0.94 mm; this variation indicates the fastening of samples is a critical step. The testing machine included pneumatic fasteners that cause superfluous force with the various thicknesses of samples. Therefore, the force measurement must be reset at the start of the tensile test in order that the pneumatic fasteners will not distort the results. Alternatively, this troubleshooting could be eliminated by manufacturing homogenous test samples during the sampling phase.
The impact strength test illustrates a different mechanical feature of the material because it measures a momentary strain, while most of the other tests measure the long-term strain of the material. The increasing content of wood fiber decreased the impact strength25. The dimensions of the samples must be measured in all tests, and there may be variations between researchers in the use of measuring devices (e.g., compression force in the use of a caliper or micrometer). Therefore, it is important that the same person measures the dimensions of samples in every test, thereby excluding human errors in the measurements. Another option as a modification technique is to use a device that includes a moment for compression. In addition, the test atmosphere may have an influence on the studied properties. In this study, all studied tests were performed under the same conditions, so the effect of atmosphere was similar, and had a coincident effect for every test. As a future application, the tests could be performed in a room where atmosphere is set to be stable.
Because WPC consists of at least two materials, such as wood and polymer, it can complicate the selection of a standard. For example, there may be suitable standards for wood materials, as well as for polymer materials, that will cause limitations in the selection of an appropriate standard for study. The standard organization has published standards (EN 15534-1:2014+A1:2017) in which test methods for composites made from cellulose-based materials and thermoplastics were characterized. The standard allows researchers who follow the European Standard to act in a universal way in their studies. A complication may arise if a significant portion of researchers follows another standard (e.g., ASTM International), which will cause problems in the comparisons of results. A future development may be a single standard organization whose standards would be valid globally.
The standards of WPCs include detailed instructions for the measuring of properties but the interpretation of these may vary between researchers. Benchmarking between research organizations could unify operation methods but may not be allowed because the research organizations are often restricted institutions dealing with confidential information. Therefore, this kind of visually described work ensures test practices are universal for a wider number of people, thereby restricting the possibilities for misunderstanding.

Global waste generation has grown significantly throughout history and is predicted to increase by tens of percentages in the future unless action is taken1. In particular, high-income countries have generated more than one-third of the world&#8217;s waste although they account for only 16% of the global population1. The construction sector is a significant producer of this waste due to rapid urbanization and population growth. According to estimates, approximately one-third of global solid waste is formed by construction and demolition projects; however, exact values from different areas are missing2. In the European Union (EU), the amount of construction and demolition waste (CDW) is approximately 25%&#8211;30% of total waste generation3, and includes valuable and significant secondary raw materials, like plastic. Without organized collection and management, plastic may contaminate and adversely influence ecosystems. In 2016, 242 million tons of plastic waste were generated in the world1. The share of plastic recycled in Europe was only 31.1%4.
Resource scarcity has created a need to change practices toward a circular economy, in which the aims are to use waste as a source of secondary resources and recover waste for reuse. Economic growth and minimized environmental impacts will be created by the circular economy, which is a popular concept in Europe. The European Commission adopted a European Union Action Plan for a circular economy, which set goals and indicators for contributions5.
Tighter environmental regulations and laws are contributing to the construction sector putting more effort into waste management and material recycling issues. For example, the European Union (EU) has set targets for material recovery. From the year 2020 onwards, the material recovery rate of non-hazardous CDW should be 70%6. The composition of CDW may vary widely across geographical locations but some common characteristics can be identified, including, for example, plastic that is a potential and valuable raw material for wood-polymer composites. The reutilization of plastic is a concrete step towards a circular economy in which virgin plastic polymers are substituted by recycled polymer.
Composite materials are a multi-phase system, consisting of a matrix material and reinforcing phase. Wood-polymer composite (WPC) typically contains polymers as the matrix, wood materials as reinforcement, and additives for improving adhesion, such as coupling agents and lubricants. WPC can be known as an environmentally friendly material because the raw material can be sourced from renewable materials, such as polylactic acid (PLA) and wood. According to the latest innovation7, the additives of WPC can be based on renewable sources. Additionally, the source of the raw material can be recycled (non-virgin) materials, which is an ecologically and technically superior alternative8. For example, researchers have studied extruded WPC that contains CDW, and found that the properties of CDW&#8211;based composites were at an acceptable level9. Utilization of recycled raw materials as a component for WPC is also acceptable from the environmental aspect, as proved by several assessments. Overall, it has been demonstrated that utilizing CDW in WPC production can decrease the environmental influences of CDW management10. In addition, it has been found that using recycled polypropylene (PP) plastic in WPC has the potential to reduce global warming11.
The amount of available recycled polymers will increase in the future. Global plastic production has increased approximately 9% as per year, on average, and it is expected that this increment will continue in the future12. The most general plastic polymer types are, inter alia, polypropylene (PP) and polyethylene (PE). The shares of total demand for PE and PP were 29.8% and 19.3%, respectively, in Europe in 20174. The global plastic recycling market is expected to grow at an annual growth rate of 5.6% during the period 2018&#8211;202613. One of the main applications in which plastics is used is building and construction. For example, almost 20% of the total demand for European plastic was associated with building and construction applications4. From an economic perspective, the use of recycled polymers in WPC manufacturing is an interesting alternative, leading to the production of materials with low cost. Previous research has shown that physical effects have a stronger influence on extruded materials made from secondary plastic compared to the corresponding virgin material, but properties depend on the plastic source14. However, the use of recycled plastic decreases the strength of WPC due to lower compatibility15. Variation between the structures of plastic polymers causes concerns for re-use and recycling, which contribute to the importance of plastic sorting based on the polymer.
This study intends to assess the utilization of plastic material from CDW as a raw material for WPC. The polymer fractions assessed in the study are acrylonitrile butadiene styrene (ABS), polypropylene (PP), and polyethylene (PE). These are known as universal plastic fractions within CDW. The polymer fractions are treated with general manufacturing processes, such as agglomeration and extrusion, and are tested with universal mechanical property tests. The primary objective of the study is to discover how the properties of WPC would alter if recycled polymers were used as a raw material in matrix instead of primary virgin polymers.
Based on the (local) waste management center (Etel&#228;-Karjalan J&#228;tehuolto Oy), it was shown how plastic-rich CDW is stored. It was demonstrated that a great amount plastic material is included and some examples of CDW plastic polymers were shown. Researchers collected the most suitable polymers for further processing, such as ABS, PP, and PE. The desired polymers (PE, PP, ABS) were identified using portable near infrared (NIR) spectroscopy. WPC product examples were presented in which where collected plastic materials could be utilized as a raw material. The definition of the composite and its advantages were explained.

<table><tbody><tr><td>Agglomeration</td><td>Plasmec</td><td>TRL100/FV/W</td><td>apparatus of turbomixer</td></tr><tr><td>Agglomeration</td><td>Plasmec</td><td>RFV 200</td><td>apparatus of cooler</td></tr><tr><td>CNC router</td><td>Recontech</td><td>F2 - 1325 C</td><td>CNC machine</td></tr><tr><td>Condition chamber</td><td>Memmert</td><td>HPP260</td><td>constant climate chamber</td></tr><tr><td>Coupling agent</td><td>DuPont</td><td>Fusabond E226</td><td>commercial coupling agent additive</td></tr><tr><td>Crusher 1 (crusher/shredder )</td><td>Untha</td><td>Untha LR 630</td><td>10-20 mm sieve</td></tr><tr><td>Crusher 2 (low-speed crusher)</td><td>Shini</td><td>Shini SG-1635N-CE</td><td>5 mm sieve, granulator</td></tr><tr><td>Extruder</td><td>Weber</td><td>Weber CE 7.2</td><td>conical counter-rotating twin-screw</td></tr><tr><td>Lubricant</td><td>Struktol</td><td>TPW 113</td><td>commercial lubricant additive</td></tr><tr><td>NIR spectroscopy</td><td>Thermo Fisher Scientific</td><td>Thermo Scientific microPHAZIR PC</td><td></td></tr><tr><td>Recycled material ABS from CDW</td><td></td><td></td><td></td></tr><tr><td>Recycled material PE from CDW</td><td></td><td></td><td></td></tr><tr><td>Recycled material PP from CDW</td><td></td><td></td><td></td></tr><tr><td>Sliding table saw</td><td>Altendorf</td><td>F-90</td><td>circular saw/sliding table saw</td></tr><tr><td>Testing apparatus</td><td>Zwick</td><td>5102</td><td>impact tester</td></tr><tr><td>Testing machine</td><td>Zwick Roell</td><td>Z020</td><td>allround-line materials testing machine</td></tr><tr><td>Wood flour (Spruce) material</td><td></td><td></td><td></td></tr><tr><td>WPC example material</td><td>UPM Profi</td><td></td><td>Decking board</td></tr></tbody></table>

the effect of construction and demolition waste plastic fractions on wood-polymer composite properties

Construction and demolition waste (CDW), including valuable materials such as plastics, have a remarkable influence on the waste sector. In order for plastic materials to be re-utilized, they must be identified and separated according to their polymer composition. In this study, the identification of these materials was performed using near-infrared spectroscopy (NIR), which identified material based on their physical-chemical properties. Advantages of the NIR method are a low environmental impact and rapid measurement (within a few seconds) in the spectral range of 1600-2400 nm without special sample preparation. Limitations include its inability to analyze dark materials. The identified polymers were utilized as a component for wood-polymer composite (WPC) that consists of a polymer matrix, low cost fillers, and additives. The components were first compounded with an agglomeration apparatus, followed by production by extrusion. In the agglomeration process, the aim was to compound all materials to produce uniformly distributed and granulated materials as pellets. During the agglomeration process, the polymer (matrix) was melted and fillers and other additives were then mixed into the melted polymer, being ready for the extrusion process. In the extrusion method, heat and shear forces were applied to a material within the barrel of a conical counter-rotating twin-screw type extruder, which reduces the risk of burning the materials and lower shear mixing. The heated and sheared mixture was then conveyed through a die to give the product the desired shape. The above-described protocol proved the potential for re-utilization of CDW materials. Functional properties must be verified according to the standardized tests, such as flexural, tensile, and impact strength tests for the material.

To investigate the effect of CDW plastic polymer on the mechanical properties of WPC, three different polymer types as a matrix were studied. Table 1 presents the composition of materials and Table 2 reports the manufacturing processes. The material of CDW-PP requires a higher treatment temperature for tools but, correspondingly, melt pressure was lower compared to the other materials (CDW-ABS and CDW-PE).
Figure 1 presents the flexural strength of material (an average from 20 measurements) as bar charts, including standard deviations as an error bar. The highest flexural strength values were achieved with material containing a recycled ABS polymer in a matrix. Almost congruent high-strength quality was achieved in the material in which recycled PE polymer was used in a matrix. The lowest flexural strengths were achieved with material containing a recycled PP polymer in a matrix. Figure 1 also presents similar results for the flexural modulus of materials, which was measured simultaneously with the strength property. However, even though recycled ABS and PE polymers have congruent results as in the strength tests, the flexural modulus results were different. The recycled PE materials have a significantly lower modulus value compared to the value of recycled ABS polymer.
<img alt="Figure 1" class="xfigimg" src="/files/ftp_upload/61064/61064fig01.jpg" /> 
Figure 1: The flexural properties of the studied materials. 
The flexural strength is presented in the solid color filled bars (red, green, and blue) and the flexural modulus is presented using the same colors in pattern-filled bars. The standard deviations are described as error bars. <a href="https://www.jove.com/files/ftp_upload/61064/61064fig01large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
Figure 2 shows the tensile strength and modulus (an average from 20 measurements) as bar charts, including standard deviations as an error bar. The materials, in which recycled ABS and PE were used, have almost congruent tensile strength results but the standard deviation was higher for the material in which recycled ABS was used. The weakest tensile strength was achieved material containing a recycled PP polymer in a matrix. The results of tensile modulus were congruent with the results of flexural modulus, in which the best modulus was achieved with the recycled ABS polymer.
<img alt="Figure 2" class="xfigimg" src="/files/ftp_upload/61064/61064fig02.jpg" /> 
Figure 2: The tensile properties of the studied materials. 
The tensile strength is presented in the solid color filled bars (red, green, and blue) and the tensile modulus is presented using the same colors in pattern-filled bars. The standard deviations are described as error bars. <a href="https://www.jove.com/files/ftp_upload/61064/61064fig02large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
Figure 3 displays the impact strength properties of materials (an average from 20 measurements) as bar charts, including standard deviations as an error bar. The impact strengths of recycled ABS and PP polymers were almost at the same level, but greater impact strength was achieved with the recycled PE polymer, which had the best impact strength property in this study.
<img alt="Figure 3" class="xfigimg" src="/files/ftp_upload/61064/61064fig03.jpg" /> 
Figure 3: The impact strength properties of the studied materials. 
The impact strength is presented in the solid color filled bars and the standard deviations are described as error bars. <a href="https://www.jove.com/files/ftp_upload/61064/61064fig03large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
ABS polymer consists of three monomers, which might increase the favorable behavior within the WPC. For example, the acrylonitrile component contributes strength, butadiene components contribute impact resistance, and styrene components contributes rigidity. PE-based WPC accounts for the largest market share, for examples in North America, and it is easy to nail, screw, and saw. However, PE is manufactured in various polymeric forms, such as high-density polyethylene (HDPE) and low-density polyethylene (LDPE), which have different features. The PP-based WPC had the weakest properties in this study, consistent with the fact that its market share is relatively small. Although it has several superior properties compared to polyethylene, such as being lighter and stronger, it is also more brittle than polyethylene21.
Overall, recycling of composites is the ecologically preferable pathway8, and recycled waste plastic is a suitable raw material for composites, in which performance can be improved using compatibilizers22. The reason for varied mechanical properties might be due to the composition of materials and, in particular, the coupling agent may have a significant effect. The mechanical properties of recycled polymers in WPC were improved with compatibilizers but the effects depend strongly on the agent used and its amount in the structure, causing a large variation between the used agents23. A previous study indicated that the highest performance of PP based WPC was achieved with amounts of compatibilizers at three percentage levels24, which is congruent with the amount used in this study. Thus, the coupling agent used might be more problematic than the level of agent. However, it is generally accepted that the mechanical performance of WPCs is improved when coupling agents are used under optimized conditions25.
Each polymer has individual features in material, demonstrating that separation of polymers increases the value of WPC with the correct additives. In future, novel eco-friendly alternative coupling agents for recycled polymer composites might be used to meet demand, such as the starch gum shown in a new study of Rocha and Rosa26. Additionally, the re-utilization of plastic must make economic sense, and thus also require future action.

Watch this Scientific Journal Video about The Effect of Construction and Demolition Waste Plastic Fractions on Wood-Polymer Composite Properties at JoVE.com

The Effect of Construction and Demolition Waste Plastic Fractions on Wood-Polymer Composite Properties

Secondary material streams have been shown to include potential raw materials for production. Presented here is a protocol in which CDW-plastic waste as a raw material is identified, followed by various processing steps (agglomeration, extrusion). As a result, a composite material was produced, and mechanical properties were analyzed.

Construction and demolition waste (CDW), including valuable materials such as plastics, have a remarkable influence on the waste sector. In order for ...

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Unit 1

Wood

SCIENTISTS IN ACTION

6.9K Views.  LUT University. Secondary material streams have been shown to include potential raw materials for production. Presented here is a protocol in which CDW-plastic waste as a raw material is identified, followed by various processing steps (agglomeration, extrusion). As a result, a composite material was produced, and mechanical properties were analyzed.

Video: The Effect of Construction and Demolition Waste Plastic Fractions on Wood-Polymer Composite Properties

Towards Biomimicking Wood: Fabricated Free-standing Films of Nanocellulose, Lignin, and a Synthetic Polycation

Woody materials are comprised of plant cell walls that contain a layered secondary cell wall composed of structural polymers of polysaccharides and lignin. Layer-by-layer (LbL) assembly process which relies on the assembly of oppositely charged molecules from aqueous solutions was used to build a freestanding composite film of isolated wood polymers of lignin and oxidized nanofibril cellulose (NFC). To facilitate the assembly of these negatively charged polymers, a positively charged polyelectrolyte, poly(diallyldimethylammomium chloride) (PDDA), was used as a linking layer to create this simplified model cell wall. The layered adsorption process was studied quantitatively using quartz crystal microbalance with dissipation monitoring (QCM-D) and ellipsometry. The results showed that layer mass/thickness per adsorbed layer increased as a function of total number of layers. The surface coverage of the adsorbed layers was studied with atomic force microscopy (AFM). Complete coverage of the surface with lignin in all the deposition cycles was found for the system, however, surface coverage by NFC increased with the number of layers. The adsorption process was carried out for 250 cycles (500 bilayers) on a cellulose acetate (CA) substrate. Transparent free-standing LBL assembled nanocomposite films were obtained when the CA substrate was later dissolved in acetone. Scanning electron microscopy (SEM) of the fractured cross-sections showed a lamellar structure, and the thickness per adsorption cycle (PDDA-Lignin-PDDA-NC) was estimated to be 17 nm for two different lignin types used in the study. The data indicates a film with highly controlled architecture where nanocellulose and lignin are spatially deposited on the nanoscale (a polymer-polymer nanocomposites), similar to what is observed in the native cell wall.

The objective of this research was to form synthetic plant cell wall tissue using layer-by-layer assembly of nanocellulose fibrils and isolated lignin assembled from dilute aqueous suspensions.&#160; Surface measurement techniques of quartz crystal microbalance and atomic force microscopy were used to monitor the formation of the polymer-polymer nanocomposite material.

Woody materials are comprised of plant cell walls that contain a layered secondary cell wall composed of structural polymers of polysaccharides and ...

Chemistry

A Testing Platform for Durability Studies of Polymers and Fiber-reinforced Polymer Composites under Concurrent Hygrothermo-mechanical Stimuli

The durability of polymers and fiber-reinforced polymer composites under service condition is a critical aspect to be addressed for their robust designs and condition-based maintenance. These materials are adopted in a wide range of engineering applications, from aircraft and ship structures, to bridges, wind turbine blades, biomaterials and biomedical implants. Polymers are viscoelastic materials, and their response may be highly nonlinear and thus make it challenging to predict and monitor their in-service performance. The laboratory-scale testing platform presented herein assists the investigation of the influence of concurrent mechanical loadings and environmental conditions on these materials. The platform was designed to be low-cost and user-friendly. Its chemically resistant materials make the platform adaptable to studies of chemical degradation due to in-service exposure to fluids. An example of experiment was conducted at RT on closed-cell polyurethane foam samples loaded with a weight corresponding to ~50% of their ultimate static and dry load. Results show that the testing apparatus is appropriate for these studies. Results also highlight the larger vulnerability of the polymer under concurrent loading, based on the higher mid-point displacements and lower residual failure loads. Recommendations are made for additional improvements to the testing apparatus.

The durability of polymers and fiber-reinforced polymer composites in service is a critical aspect for their designs and condition-based maintenance. We present a novel low-cost laboratory testing platform for the investigation of the influence of concurrent mechanical and environmental loadings, and may help design more efficient yet safer composite structures.

The durability of polymers and fiber-reinforced polymer composites under service condition is a critical aspect to be addressed for their robust designs ...

Engineering

Manufacturing Of Robust Natural Fiber Preforms Utilizing Bacterial Cellulose as Binder

A novel method of manufacturing rigid and robust natural fiber preforms is presented here. This method is based on a papermaking process, whereby loose and short sisal fibers are dispersed into a water suspension containing bacterial cellulose. The fiber and nanocellulose suspension is then filtered (using vacuum or gravity) and the wet filter cake pressed to squeeze out any excess water, followed by a drying step. This will result in the hornification of the bacterial cellulose network, holding the loose natural fibers together.
Our method is specially suited for the manufacturing of rigid and robust preforms of hydrophilic fibers. The porous and hydrophilic nature of such fibers results in significant water uptake, drawing in the bacterial cellulose dispersed in the suspension. The bacterial cellulose will then be filtered against the surface of these fibers, forming a bacterial cellulose coating. When the loose fiber-bacterial cellulose suspension is filtered and dried, the adjacent bacterial cellulose forms a network and hornified to hold the otherwise loose fibers together.
The introduction of bacterial cellulose into the preform resulted in a significant increase of the mechanical properties of the fiber preforms. This can be attributed to the high stiffness and strength of the bacterial cellulose network. With this preform, renewable high performance hierarchical composites can also be manufactured by using conventional composite production methods, such as resin film infusion (RFI) or resin transfer molding (RTM). Here, we also describe the manufacturing of renewable hierarchical composites using double bag vacuum assisted resin infusion.

We present a novel method of manufacturing rigid and robust short natural fiber preforms using a papermaking process. Bacterial cellulose acts simultaneously as the binder for the loose fibers and provides rigidity to the fiber preforms. These preforms can be infused with a resin to produce truly green hierarchical composites.

A novel method of manufacturing rigid and robust natural fiber preforms is presented here. This method is based on a papermaking process, whereby loose ...

Bioengineering

Fabrication and Design of Wood-Based High-Performance Composites

Delignified densified wood is a new promising and sustainable material that possesses the potential to replace synthetic materials, such as glass fiber reinforced composites, due to its excellent mechanical properties. Delignified wood, however, is rather fragile in a wet state, which makes handling and shaping challenging. Here we present two fabrication processes, closed-mold densification and vacuum densification, to produce high-performance cellulose composites based on delignified wood, including an assessment of their advantages and limitations. Further, we suggest strategies for how the composites can be re-used or decomposed at the end-of-life cycle. Closed-mold densification has the advantage that no elaborate lab equipment is needed. Simple screw clamps or a press can be used for densification. We recommend this method for small parts with simple geometries and large radii of curvature. Vacuum densification in an open-mold process is suitable for larger objects and complex geometries, including small radii of curvature. Compared to the closed-mold process, the open-mold vacuum approach only needs the manufacture of a single mold cavity.

Delignified densified wood represents a new promising lightweight, high-performance and bio-based material with great potential to partially substitute natural fiber reinforced- or glass fiber reinforced composites in the future. We here present two versatile fabrication routes and demonstrate the possibility to create complex composite parts.

Delignified densified wood is a new promising and sustainable material that possesses the potential to replace synthetic materials, such as glass fiber ...

Twin-Screw Extrusion Process to Produce Renewable Fiberboards

A versatile twin-screw extrusion process to provide an efficient thermo-mechano-chemical pre-treatment on lignocellulosic biomass before using it as source of mechanical reinforcement in fully bio-based fiberboards was developed. Various lignocellulosic crop by-products have already been successfully pre-treated through this process, e.g., cereal straws (especially rice), coriander straw, shives from oleaginous flax straw, and bark of both amaranth and sunflower stems.
The extrusion process results in a marked increase in the average fiber aspect ratio, leading to improved mechanical properties of fiberboards. The twin-screw extruder can also be fitted with a filtration module at the end of the barrel. The continuous extraction of various chemicals (e.g., free sugars, hemicelluloses, volatiles from essential oil fractions, etc.) from the lignocellulosic substrate, and the fiber refining can, therefore, be performed simultaneously.
The extruder can also be used for its mixing ability: a natural binder (e.g., Organosolv lignins, protein-based oilcakes, starch, etc.) can be added to the refined fibers at the end of the screw profile. The obtained premix is ready to be molded through hot pressing, with the natural binder contributing to fiberboard cohesion. Such a combined process in a single extruder pass improves the production time, production cost, and may lead to reduction in plant production size. Because all the operations are performed in a single step, fiber morphology is better preserved, thanks to a reduced residence time of the material inside the extruder, resulting in enhanced material performances. Such one-step extrusion operation may be at the origin of a valuable industrial process intensification.
Compared to commercial wood-based materials, these fully bio-based fiberboards do not emit any formaldehyde, and they could find various applications, e.g., intermediate containers, furniture, domestic flooring, shelving, general construction, etc.

A versatile twin-screw extrusion process to provide an efficient thermo-mechano-chemical pretreatment on lignocellulosic biomass was developed, which leads to an increased average fiber aspect ratio. A natural binder can also be added continuously after fiber refining, leading to bio-based fiberboards with improved mechanical properties after hot pressing of the obtained extruded material.

A versatile twin-screw extrusion process to provide an efficient thermo-mechano-chemical pre-treatment on lignocellulosic biomass before using it as ...

Designed for Molecular Recycling: A Lignin-Derived Semi-aromatic Biobased Polymer

The development of chemically recyclable biopolymers offers opportunities within the pursuit of a circular economy. Chemically recyclable biopolymers make a positive effort to solve the issue of polymer materials in the disposal phase after the use phase. In this paper, the production of biobased semi-aromatic polyesters, which can be extracted entirely from biomass such as lignin, is described and visualized. The polymer poly-S described in this paper has thermal properties similar to certain commonly used plastics, such as PET. We developed a Green Knoevenagel reaction, which can efficiently produce monomers from aromatic aldehydes and malonic acid. This reaction has been proven to be scalable and has a remarkably low calculated E-factor. These polyesters with ligno-phytochemicals as a starting point show an efficient molecular recycling with minimal losses. The polyester poly(dihydrosinapinic acid) (poly-S) is presented as an example of these semi-aromatic polyesters, and the polymerization, depolymerization, and re-polymerization are described.

An example of a closed-loop approach towards a circular materials economy is described here. A whole sustainable cycle is presented where biobased semi-aromatic polyesters are designed by polymerization, depolymerization, and then re-polymerized with only slight changes in their yields or final properties.

The development of chemically recyclable biopolymers offers opportunities within the pursuit of a circular economy. Chemically recyclable biopolymers make ...

Fabrication and Mechanical Property Assessment of Fiber Composite Laminates

Measuring the Mechanical Properties of Glass Fiber Reinforcement Polymer Composite Laminates Obtained by Different Fabrication Processes

The traditional wet hand lay-up process (WL) has been widely applied in the manufacturing of fiber composite laminates. However, due insufficiency in the forming pressure, the mass fraction of fiber is reduced and lots of air bubbles are trapped inside, resulting in low-quality laminates (low stiffness and strength). The wet hand lay-up/vacuum bag (WLVB) process for the fabrication of composite laminates is based on the traditional wet hand lay-up process, using a vacuum bag to remove air bubbles and provide pressure, and then carrying out the heating and curing process. 
Compared with the traditional hand lay-up process, laminates manufactured by the WLVB process show superior mechanical properties, including better strength and stiffness, higher fiber volume fraction, and lower void volume fraction, which are all benefits for composite laminates. This process is completely manual, and it is greatly influenced by the skills of the preparation personnel. Therefore, the products are prone to defects such as voids and uneven thickness, leading to unstable qualities and mechanical properties of the laminate. Hence, it is necessary to finely describe the WLVB process, finely control steps, and quantify material ratios, in order to ensure the mechanical properties of laminates. 
This paper describes the meticulous process of the WLVB process for preparing woven plain patterned glass fiber reinforcement composite laminates (GFRPs). The fiber volume content of laminates was calculated using the formula method, and the calculated results showed that the fiber volume content of WL laminates was 42.04%, while that of WLVB laminates was 57.82%, increasing by 15.78%. The mechanical properties of the laminates were characterized using tensile and impact tests. The experimental results revealed that with the WLVB process, the strength and modulus of the laminates were enhanced by 17.4% and 16.35%, respectively, and the specific absorbed energy was increased by 19.48%.

Author Spotlight: Enhancing Fiber Composite Laminate Quality with the Wet Hand Lay-Up/Vacuum Bag Process 

This paper describes a fabrication process for fiber-reinforced polymer matrix composite laminates obtained using the wet hand lay-up/vacuum bag method.

The traditional wet hand lay-up process (WL) has been widely applied in the manufacturing of fiber composite laminates. However, due insufficiency in the ...

Isolation of Native Soil Microorganisms with Potential for Breaking Down Biodegradable Plastic Mulch Films Used in Agriculture

Fungi native to agricultural soils that colonized commercially available biodegradable mulch (BDM) films were isolated and assessed for potential to degrade plastics. Typically, when formulations of plastics are known and a source of the feedstock is available, powdered plastic can be suspended in agar-based media and degradation determined by visualization of clearing zones. However, this approach poorly mimics in situ degradation of BDMs. First, BDMs are not dispersed as small particles throughout the soil matrix. Secondly, BDMs are not sold commercially as pure polymers, but rather as films containing additives (e.g. fillers, plasticizers and dyes) that may affect microbial growth. The procedures described herein were used for isolates acquired from soil-buried mulch films. Fungal isolates acquired from excavated BDMs were tested individually for growth on pieces of new, disinfested BDMs laid atop defined medium containing no carbon source except agar. Isolates that grew on BDMs were further tested in liquid medium where BDMs were the sole added carbon source. After approximately ten weeks, fungal colonization and BDM degradation were assessed by scanning electron microscopy. Isolates were identified via analysis of ribosomal RNA gene sequences. This report describes methods for fungal isolation, but bacteria also were isolated using these methods by substituting media appropriate for bacteria. Our methodology should prove useful for studies investigating breakdown of intact plastic films or products for which plastic feedstocks are either unknown or not available. However our approach does not provide a quantitative method for comparing rates of BDM degradation.

Plastic films labeled "biodegradable" are commercially available for agricultural use as mulches. Tillage represents an attractive disposal method, but degradation under field conditions is poorly understood. The purpose of this study was to develop methods for isolating native soil fungi and bacteria that colonize plastic mulch films after field burial.

Fungi native to agricultural soils that colonized commercially available biodegradable mulch (BDM) films were isolated and assessed for potential to ...

Biology

Tension Tests of Polymers

Source:&#160;Roberto Leon, Department of Civil and Environmental Engineering, Virginia Tech, Blacksburg, VA
Polymeric materials are widely used in civil structures, with uses ranging from very soft sealants to more rigid pipes in water and wastewater systems. The most basic definition of a polymer is a molecular structure with repeating subunits. The term polymer comes from Greek, where &#34;poly&#34; means many, and &#34;-mer&#34; means basic unit. Monomers, or single mers, are the specific repeating units. With polymers, the structure, including the length of the carbon backbone and the varying flexibility, will dictate the properties of the polymer. Polymers are classified into 3 subcategories: plastics, elastomers, and rigid rod polymers. Plastics are further subdivided into thermosets, which do not soften on heating, and thermoplastics, which do soften when heated and harden on cooling. Additionally, thermoplastics are mostly linear or branched polymers with little to no cross-linking, whereas thermosets exhibit 3D structure and have extensive cross-linking. Elastomers, or rubbers, are long, coiled chains and can be stretched to twice the original length, but will contract back to the original size when released, whereas rigid rod polymers do not stretch and are strong, crystalline structures.
In this laboratory, we will look at several different polymeric materials, including high density polyethylene (HDPE), polyvinyl chlorides (PVC), nylon, and methyl methacrylate (acrylic) in order to understand the breadth and diversity of the stress-strain curves for these materials and how their mechanical properties affect their performance.

Uniaxial Tensile Test Strength for Polymers

Source:&#160;Roberto Leon, Department of Civil and Environmental Engineering, Virginia Tech, Blacksburg, VA
Polymeric materials are widely used in civil ...

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Structural Engineering

Tension Test of Fiber-Reinforced Polymeric Materials

Source:&#160;Roberto Leon, Department of Civil and Environmental Engineering, Virginia Tech, Blacksburg, VA
Fiber-reinforced polymeric materials (FRP) are composite materials that are formed by longitudinal fibers embedded in a polymeric resin, thereby creating a polymer matrix with aligned fibers along one or more directions. In its simplest form, the fibers in FRP materials are aligned in an orderly, parallel fashion, thus imparting orthotropic material characteristics, meaning that the material will behave differently in the two directions. Parallel to the fibers, the material will be very strong and/or stiff, whereas perpendicular to the fibers will be very weak, as the strength can only be attributed to the resin instead of the whole matrix.
An example of this unidirectional configuration is the commercially available FRP reinforcing bars, which mimic the conventional steel bars used in reinforced concrete construction. FRP materials are used both as stand-alone structures such as pedestrian bridges and staircases, and also as materials to strengthen and repair existing structures. The thin, long plates are often epoxied to existing concrete structures to add strength. In this case, the FRP bars act as external reinforcement. The FRP bars and plates are lighter and more corrosion resistant, so they are finding applications in bridge decks and parking garages, where de-icing slats lead to rapid deterioration of conventional bars.
In this laboratory exercise, the tensile behavior of a unidirectional specimen will be studied, with emphasis on its ultimate strength and deformation capacity. The behavior of the specimen is expected to be elastic until failure, which is expected to occur in a sudden and explosive manner. This behavior should be contrasted with those of ductile steels, which exhibit extensive deformation capacity and strain hardening before failure.

Uniaxial Tension Test of Fiber-Reinforced Polymeric Materials

Source:&#160;Roberto Leon, Department of Civil and Environmental Engineering, Virginia Tech, Blacksburg, VA
Fiber-reinforced polymeric materials (FRP) are ...