Composite material from waste poly (ethylene terephthalate) reinforced with glass fiber and waste window glass filler

ABSTRACT This research is manufactured composite materials from waste poly (ethylene terephthalate) reinforced with glass fiber and filled with waste window glass powder for tile application. The composite samples were prepared by the melt-mixing method followed by compression molding. The mechanical, thermal, and physical properties are investigated. To do this Charpy impact and Rockwell hardness testing machines, DSC, and Thermogravimetric analysis instruments were used. For this, it was prepared eleven samples by varying the glass fiber weight percentage from 0 to 10, matrix weight percentage from 70 to 85, and glass powder filler weight percentage from 5 to 20. The maximum impact strength (5.11 J/cm2) is recorded at 10% weight of glass fiber, 85% weight of PET matrix, and 5% weight of window glass filler. The maximum Rockwell hardness (184.2HR) and the minimum water absorption (0.048%) are also recorded at 0 weight % of glass fiber, 80 weight % of poly(ethylene terephthalate), PET, matrix, and 20 weight% of window glass filler. It can be concluded that the impact strength increased with increased weight % of glass fiber and decreased with increased window glass filler. The Rockwell hardness increased, and the water absorption decreased with increased weight % of window glass filler. GRAPHICAL ABSTRACT


Introduction
Plastic is a valuable material for many functions because of its unique, cheap, versatile, lightweight, and resistant.It can also provide environmental benefits: it plays a critical role in maintaining food quality, and safety and reducing food waste (1).After primary use and post-consumer plastic materials are discarded (2,3) and those are non-biodegradability and most developing countries are experiencing a shortage of post-consumer disposal waste sites, posing a major environmental pollution concern (3)(4)(5)(6).The trade-offs between plastics and substitutes are therefore complex and could create negative impacts on the environment.
According to National Geography (7) report, the world's population is increasingly using plasticwrapped products and discarding these plastics after use.According to United Nations Development Programme (UNDP) report, India generates 15 million tonnes of plastic waste every year but only one-fourth is recycled due to lack of a functioning solid waste management system (8).
As Trevor M. Letcher reported, globally, only 9% of all the plastic ever made has been recycled with 12% having been burnt and the remainder ending up in soils, oceans, and landfill (6) while 22% is mismanaged (9,10).Mass production of plastics and poor control of plastic products at end of life has led to annual increases in plastic entering the marine environment.Their durability and density allow the plastic to be transported over large distances and to persist for long periods in the marine environment (1,(11)(12)(13)(14).
As a result, the surrounding environment has been heavily polluted.If the environment is polluted, it will cause serious health problems.Plastic pollution has become one of the most pressing environmental issues as the rapidly increasing production of plastic products overwhelms the world's capacity to cope (12).Thermochemical conversion of plastic waste to fuels (15,16).Traditional treatments for post-consumed plastics were recycled, landfilled, or incinerated.However, landfill of post-consumed plastics has potential problems because of limited land resource and the high durability of plastics (17,18).
Of the most common solid wastes are plastic material especially PET is used as a water bottle and broken glass.These PET bottle materials are disposed of in the environment after the consumer consumes the product and glass products are also discarded as solid waste material if there is some cracking or broken down of the product.
There are a lot of manufacturing companies that produce plastic-and glass-packed products.After the primary uses of the product, the packing plastics and glasses are discarded everywhere randomly in the environment.Those discarded solid waste materials are not appropriately managed and controlled, which results in environmental pollution.
As a result, it poses risks to human safety and has an impact on climate, socioeconomic situations, the health of humans, animals, and many different ecosystems.As the volume of solid waste increases, so does the impact.Due to the nonbiodegradability of plastics and glasses, environmental pollution becomes a particularly serious issue in many developing countries, where there is a lack of post-consumer waste disposal facilities.Regenerating and exploiting waste as a resource and lowering environmental contamination are therefore of growing concern.This work applies the manufacturing of composites made systematically from solid waste materials like plastic and glass to the production of building materials.Utilizing used PET bottles, we create composites that can substitute ceramic-based floor tile materials.

Materials and equipment
The following raw materials were used E-glass chopped strand mat fiber (GF), waste (Recycle) PET bottle and waste glasses (filler), stove and casserole (cooker), soap and water, sheet metal (mold), weight balance, jaw crusher, disk miller, sieve analyser, and basin of water are used to wash the PET bottle and glass wastes.
The following testing device JBS-500B model Charpy impact testing machine: used to test the impact strength or the toughness of the material, Rockwell hardness testing machine: used to test the hardness properties of the composite, PerkinElmer for DSC and Thermogravimetric analysis (TGA): used to test the heat flow and weight loss, respectively.

Methods
The waste PET bottles and glasses were collected, washed to remove any impurities, and dried them to ensure no moisture remains.Figures 1 and 2 shown shredded and grounded into small sizes for easier melting and mixing.
The collected discarded glass was cleaned to remove any impurities and then dried at room temperature to make sure no moisture remained before being ground into small pieces.They were then reduced in size using a jaw crusher and a disk miller (to finer).The particle size of window glass was between 0.75 and 1.0 mm sieve analysis (see Figure 2 (a-i))).This was done for easier mixing with the melted PET matrix.
The E-glass fibers (GF) were bought in the form of a non-woven mat.It was separated manually into individual fibers of 4 cm in length as shown in Figure 3.This was done for easy mixing with the melted PET.The most suitable processing size for melt mixing which gives effective.Then melted the PET (matrix), the fibers and fillers were added at the required proportion and stirred until a homogeneous mixture was achieved.The mixture was then poured into the square mold of 20 × 20× 3 cm and pressed to ensure it spread throughout the mold.Three factors namely glass fiber, PET matrix, and waste window glass weight percentage variation was considered and their effect on the performance of the composite was examined.As shown in Table 1, the ratio of the three components was varied  until the optimum result was obtained and for this design of expert software package was used.

Prepared composite sample
This research is continued from the first part of this research work so that the raw materials and method are the same (20).Which means randomly oriented glass fiber-recycled PET with waste window glass filler composite with varying fiber, matrix, and filler weight proportion were manufactured by the melt-mixing process (a combination of compounding and pressing techniques).The parameters used were a mixing time of 8 min, rotor speed of 60 rpm, and mixing temperature of 265°C based on an early work (21).To prevent PET from adhering to the mold, a releasing agent was used to unsoiled the surface.First melt the recycle PET matrix and then add the prepared chopped glass fiber and filler.After they are uniformly mixed, pouring it into the prepared mold.Finally, the mold was closed, and the samples were cooled down to room temperature under 12.5 MPa pressure for 30 min and demolded the sample as shown in Figure 4.

Thermal analysis
Thermal analysis is a series of techniques that provide physical property measurement as a function of temperature, time, and other variables.Mainly, TGA measures the weight change of composite sample over temperature range and DSC measure the heat flow of composite sample over the given temperature range.The thermal behavior of PET bottles and recycled PET was measured with both DSC and TGA.DSC samples were heated at a rate of 40 °C/min from 30 to 445°C under a nitrogen atmosphere.The test was carried out under an air atmosphere at a flow of 20 ml/min.TGA was performed at a temperature range from 30°C to 1200°C, with a heating rate of 30°C/min.This was done to check the effect of recycling on the properties of PET and used to investigate the response of recycling PET polymers on heating.
2.4.2.Mechanical test 2.4.2.1.Impact strength test.Charpy impact tests on unnotched specimens were performed using a pendulum impact testing machine (JBS-500B model).The samples were prepared according to the ASTM D256 test standard (22) with dimensions 55 × 12 × 10 mm as shown in Table 2. Five specimens were tested and an average value was reported.As shown in Figure 5(a) Rockwell hardness testing, (b) the gauge position before minor load, and (c) the gauge position after minor load.The specimen is prepared by fulfilling the requirement prescribed by the ASTM E384 standards (23).Since the order of the numbers is reversed on the dial gauge, a shallow impression on a hard material will result in a high number while a deep impression on a soft material will result in a low number.In this paper B scale (1/16 in.ball indenter and 100 kg load) with the normal tester was used.

Water absorption test
Water absorption tests were carried out following the recommendations specified in ASTM D570 (24)(25)(26)(27).Samples of each composite grade were oven-dried before weighing by ASTM D570.The weight recorded was reported as the initial weight of the composites.The samples were then placed in water maintained at room temperature (25°C) and at a time interval of 24 h, the samples were removed from the water, dried, and weighed.The amount of water absorbed by the composites (in percentage) was calculated using Equation (1).
where W is percent water absorption, W o and W t are the oven-dried weight, and the weight of the specimen after time t, respectively.

Data analysis
To determine the relationship between independent variables (fiber loading, polymer loading, and filler loading) and the response variables (tensile properties, compression, flexural, impact strength, hardness, and water absorbency), the Design-Expert statistical software package was used.In this research study, a mixture optimal was used because it's a more appropriate model for response variables.

Results and discussion
3.1.Thermal analysis

PET bottle and recycled PET TGA results
Thermogravimetric analysis is a technique in which the mass of a substance is monitored as a function of temperature or time as the sample specimen is subjected to a controlled temperature program in the air atmosphere.TGA can be used to evaluate the thermal stability of a material and to characterize the constitute of the material.The descending TGA thermal curve indicates a weight loss occurred.These instruments can quantify the loss of water, solvent, plasticizer, decarboxylation, pyrolysis, oxidation, decomposition, weight % filler, amount of metallic catalytic residue remaining on carbon nanotubes, and weight % ash.The specimens (composite) were heated from ambient to 1200°C under air at heating rates of 30°C/min.Figure 6 shows the two-stage TGA results of different manufactured composites.The sample codes GF, M, and F represent glass fiber, PET matrix, and filler, respectively and the subscript number indicates the weight percentage of each component.As shown in Figure 6 the composite has no mass changes over the entire range of temperature (from starting to 400°C).However, in this temperature range, volatile components such as moisture, solvents, and monomers have been removed (28,29).The decomposition (degradation) of manufactured composite materials from waste PET bottles reinforced with glass fibers and waste glass filler starts to occur at 408°C and 425°C . Thermal stability decreases as the concentration of particles and glass are increasing.The weight % of window glass filler is decreased, the thermal expansion of the PET matrix is increased due to this the maximum rate of decomposition temperature shows the regime when the maximum component in composite material is decomposing.The depolymerization of macromolecular chains caused a reduction in molecular weight in the recycled PET and contributed to the degradation of its mechanical properties (30).Between 400°C and 1000°C, the sample decomposes almost completely, i.e. it undergoes almost 100% degradation.A quantitative content determination is, therefore, a simple matter because the filler(fiber glass) does not decompose under the experimental conditions used, but remains behind as a residue while the plastic undergoes complete degradation (31).With the TGA, the thermal degradation of the composite can be predicted.Therefore, we can conclude that the waste PET bottles reinforced with glass fibers and waste glass filler composite can be used up to 400°C temperature conditions from a degradations point of view.But the mechanical properties decreased when the temperature increased from low to the melting temperature of PET.To be sure, the creep test or deformation at high-temperature test can help to decide the working conditions of the composite.

PET bottle and recycled PET DSC results
Figure 7 shows that recycled PET has a melting temperature (TM) of 255°C while for bottle PET the melting point is typically in the range of 240-255°C.The glass transition temperature (Tg) estimates the maximum operating temperature of the composite which is about 65°C.The glass transition temperature (Tg) estimates the maximum operating temperature of the composite.

Mechanical properties of manufactured composites
Characterization of the Manufactured Composites.From the experiments, it was found that the manufactured composite contains the following mechanical and water absorption properties as shown in Table 3.The results of the mechanical test were in maximum force.

Impact properties
Figure 8 shows the impact strength of manufactured composite products.The maximum (5.11 J/cm 2 ) and minimum (2.9586 J/cm 2 ) Charpy impact strength (CIS) was achieved when the weight percentage of glass fiber, PET matrix, and filler was (10, 85 & 5) and (0, 82 & 18), respectively.The impact strength of the composite increased linearly with fiber composition.An increase in fiber content from 0 to 10 weight percentage increases the impact strength by about 42%.At 10 fiber weight percentage, the impact strength value was about 42% more than that of the 0% glass fiber reinforced PET as the fiber bridge cracks and increases the resistance of its propagation.This might be because a particular composite cross-section contains more fibers to absorb the Charpy impact at a greater fiber weight percentage.However, at higher fiber weight percentages than the optimum percentage (the mixture of fiber, PET matrix, and filler weight percentage is the optimum value to get a good result), the impact strength decreased because the addition of more fibers creates stress  concentration zones where a crack can start with relatively less energy.
In practical interest, a significant part of energy absorption during impact takes place through the fiber pull-out, matrix crack, and fiber breakage (21).By replacing laminate glass in applications needing relatively high-fracture strength and toughness, impact and thermal shock tolerance at high temperatures, glass fiber-reinforced PET matrix composite materials may produce some intriguing products.Glass fiber reinforcement's main goal is to increase toughness while maintaining high-fracture strength.By expanding the crack propagation area and adding weak surfaces, brittle materials can be made more resilient to catastrophic collapse (32,33).  1) The effect of fiber, matrix, and filler loading on impact strength Figures 9 and 10a and b depict the CIS of unnotched samples of glass fiber composites with fiber weight proportion varying from 0% to 10%.The impact strength of the composite increased linearly with fiber composition.An increase in fiber content from 0 to 10 weight percentage increases the impact strength by about 42%.At 10 fiber weight %, the impact strength value was about 42% more than that of the 0% glass fiber reinforced PET as the fiber bridge cracks and increases the resistance of its propagation.This could be due to more fibers being present on a given composite crosssection to absorb the Charpy impact at a higher fiber weight percentage.
However, at a higher percentage of fiber weight percentage above the optimal percentage (to get a good result the mixture of fiber, PET matrix, and filler weight percentage is optimal value), the impact strength decreased because the addition of more fibers creates regions of stress concentrations that require comparatively less energy to initiate a crack as seen in Figure 9.
Piah et al. (34) reported that the energy-absorbing mechanism of composites during fracture includes the utilization of energy required to deboned the fibers and pull them completely out of the matrix due to weak interface strength between the fiber and matrix.In practical interest, a significant part of energy absorption during impact takes place through the fiber pull-out, matrix crack, and fiber breakage (21).
When impact-type loading conditions are applied to polymer-based composite materials, energy is absorbed during the processes of plastic deformation of the matrix material, debonding at the matrix/reinforcement interface, and reinforcing material fracture.The phenomenon that absorbs the least amount of energy for its occurrence becomes prominent (Protruding) and leads to fracture (35).
The process of fiber pull-out accounts for a sizeable portion of the energy absorption during impact in the majority of fiber-filled composites.The work required to debond the fibers from the matrix and the work required to pull the fibers out of the matrix against friction together make up the fracture energy.When the energy was transferred to the composite, the weak surface adhesion between the fiber and matrix caused the crack to begin.Due to inadequate interfacial adhesion between the fiber and matrix, the impact strength drops (21,35,36).
As shown in Figure 10c, the interaction between filler and matrix has no significant effect on CIS.However, when filler particles are incorporated in the matrix, crack length decreases considerably during the process of fracture due to this the impact strength is decreased with increased weight percentage of filler because of the brittle properties of window glass(filler).Also, if the compatibility of the filler particles with the matrix material is not good, the crack increasing at the filler particle location will play an important role and again leads to decreased impact strength of the composite materials.Therefore, the impact of strength is greatly dependent upon the interfacial strength between fiber and matrix material.

Hardness test
Hardness represents the resistance of the material surface to abrasion, scratching, and cutting.The hardness strength of the composite is maximum (184.2RHN) at (0, 82, and 18) weight % of fiber, matrix, and filler, respectively was achieved.On the contrary, minimum hardness strength (118.4RHN) when the weight % of fiber, matrix, and filler is (10, 85 and 5), respectively.The reduction could be associated with (i) fewer hardness properties of fiber than filler and matrix, (ii) fiber to fiber entanglements, and due to these easily pull-out the fiber from the matrix (iii) the minimum weight % of filler is used, and (iv) it may be poor interfacial between them.In general, the more the weight % of filler associated with the stiffer and harder property of the composite and as a result the increments to standing to carry out the Harding effects (32,37).
Figure 11 shows that the weight % of filler and PET matrix is increased and the hardness of composite is increased because the window glass filler and the crystalline PET matrix have been good harder, stiffer, and rigid properties.The hardness decreased with increased fiber weight percentage because the fiber has less stiff and rigid properties.
1) The effect of fiber, matrix, and filler loading on hardness property The hardness strength of the composite is maximum (184.2HR) at (0, 82, and 18) weight % of fiber, matrix, and filler, respectively was achieved.On the contrary, minimum hardness strength (118.4HR) when the weight % of fiber, matrix, and filler is (10, 85 and 5), respectively (see Figure 12).The reduction could be associated with (i) fewer hardness properties of fiber than filler and matrix, (ii) fiber to fiber entanglements, and due to these easily pull-out the fiber from the matrix, (iii) the minimum weight percentage of filler is used, and (iv) it may be poor interfacial between them.In general, the more the weight percentage of filler associated with the stiffer and harder property of the composite and as a result the increments to standing to carry out the Harding effects (38,39).
The weight % of PET matrix and filler is increased and the weight % of the fiber is decreased the hardness strength of the composite is increased (see Figure 13(a,  b)).The hardness strength of the composite products increased linearly with increased proportion of filler and matrix weight % because the filler and matrix materials are harder and stiffer and as a result, it resists the material surface to abrasion, scratching, and cutting.The proportion of fiber content increased from 0 to 10 weight % the hardness strength decreased.This could be due to more fibers being present on a given composite cross-section to pull out from the matrix(composites).The more ductile materials have less hardness strength property (33,38,39).
Figure 13c shows the interaction (interfacial effect) between matrix and filler on hardness strength.Here the hardness strength is linearly increased with increased weight % of filler but decreased the weight % of PET matrix is increased because the filler material is stiffer and harder than PET matrix materials and so the filler can withstand hardness forces (33).

Water absorption properties
After 24hr immersion in water, there was a noticeable effect of fiber content on water absorption test results as shown in Figure 14.Glass fiber is synthetic so that the water absorption is infinitesimal (not significant).However, the fiber proportion increased, the rate of water absorption also increased insignificantly (infinitesimally) because there are no lignocellulosic fibers are added into the composite, meaning that no hydrogen bonds were formed between the water molecules and OH group in the fibers.All lignocellulosic fibers have  high water absorption due to many -OH groups in the lignocellulosic fiber chemical structure.Lignocellulosic fibers are mainly composed of cellulose, hemicellulose, and lignin, which correspond to macromolecules with chemical structures rich in hydroxyl groups (40).The graph shows that there is low water absorbency when the fiber proportion was 0% and the absorbency increased when the proportion increased from 0% to 10% with 61.05%.
The water absorption is increased with increased weight % of fiber and decreased when the weight % of PET and window glass filler increased (see Figure 14).After 24hr immersion in water, there was a noticeable effect of fiber content on water absorption test results as shown in Figures 14 and 15.Glass fiber is synthetic so that the water absorption is infinitesimal (not significant).However, the fiber proportion increased, the rate of water absorption also increased insignificantly (infinitesimally) because there are no lignocellulosic fibers are added into the composite, meaning that no hydrogen bonds were formed between the water molecules and OH group in the fibers.All lignocellulosic fibers have high water absorption due to many -OH groups in the lignocellulosic fiber chemical structure.The graph  shows that there is low water absorbency when the fiber proportion was 0% and the absorbency increased when the proportion increased from 0% to 10% with 61.05%.
As Huner et al. reported, the rate of water absorption increased with the increase in fiber content (40,41).This was due to the formation of less surface interaction between the matrix and fiber when mixed giving higher water absorption (21).The fiber proportion is increased with respect to PET matrix and filler contents the water absorption is increased (see Figure 16 a and  b).When the weight % of filler and PET matrix has increased the water, absorption is not changed (no significant difference) and the opposite is true (see Figure 16c).In this case, the role of filler is to reduce the water sorption, staining.However, the filler was added to the mixture in the form of powder so that it increased the absorption very slightly.
The weight percentage of each component has proportional and properly mixed, it creates a perfect (optimal) interface between them due to this stronger surface interaction which formed fewer voids and micro-cracks between matrix and fibers.Unless it creates less surface interaction between fiber, matrix, and filler.This less surface interaction leads to the formation of voids and micro-cracks, which meant that more water diffuses into the composites.

Conclusion
Plastics (thermoplastics and thermosets) have recently taken the lead as a material for many uses, especially in society where they are frequently employed for packaging solid and liquid goods.Poly (ethylene terephthalate, or PET) is a thermoplastic polymer that is widely used to pack water and make bottles out of it.After initial uses of the product, many developing countries struggled with a lack of postconsumer trash disposal facilities, which led to a very serious issue with environmental pollution.Waste plastics and glasses cause environmental pollution due to their nonbiodegradability.To mitigate this problem, the waste PET bottles can be reused or recycled into other products.Reuse may not be a desirable alternative due to contamination, however recycling into new items is more desirable.Although the process of crushing, melting, reforming, and reshaping discarded glass costs energy, it is still a viable choice.With recycled PET, composite materials can be created.The prevention of environmental pollution and the regeneration of waste products as resources are therefore of increased concern.The conclusion of the study will provide insight into further methods of recycling used PET bottles, which will significantly help to protect the environment and cut down the amount of waste dumped in landfills.In addition to the environmental problems, it can create job possibilities in the collecting and production of composites.Additionally, it may give businesses the chance to diversify their product offerings.
Finally, the findings of this study demonstrated that a useful composite with good qualities could be effectively made using recycled PET as a matrix, waste window glass as a filler, and glass fiber as a reinforcing agent.The impact strength, Rockwell hardness, and water absorption properties of the composite can be inferred from this, as well as the relationship between the mechanical and water absorption qualities and the influence of fiber loading, filler loading, and PET matrix loading.At 10 weight % of glass fiber, 85 weight% of PET matrix, and 5 weight % of window glass filler we get maximum impact strength which is 5.11J/cm 2 , respectively.The maximum Rockwell hardness is 184.2HR and the minimum water absorption which is 0.048% is when the weight % of glass fiber, PET matrix, and window glass filler is 0, 82 and 20, respectively.Based on this we can conclude that the impact strength increased with the increased weight % of glass fiber.The Rockwell hardness increased, and the water absorption decreased with increased weight % of window glass.

Disclosure statement
No potential conflict of interest was reported by the author(s).

Funding
The project was supported by the Ethiopian Institute of Textile and Fashion Technology (EiTEX), Bahir Dar University.

Figure 4 .
Figure 4. Glass fiber-reinforced PET matrix with window glass filler composites.

Figure 7 .
Figure 7. DSC analysis of bottle and recycled PET.

Figure 8 .
Figure 8.The average impact strength of composites.

Figure 9 .
Figure 9.The effect of fiber, matrix, and filler weight % on impact strength.

Figure 10 .
Figure 10.Effect of (a) fiber loading as a function of the matrix (b) fiber loading as a function of filler and (c) matrix loading as a function of filler on impact strength.

Figure 11 .
Figure 11.The average of Rockwell hardness of composites.

Figure 12 .
Figure 12.The effect of fiber, matrix, and filler weight % on hardness property.

Figure 13 .
Figure 13.The effect of (a) fiber loading as a function of matrix (b) fiber loading as a function of filler and (c) matrix loading as a function of filler on hardness propert.

Figure 15 .
Figure 15.The effect of fiber, matrix, and filler weight % on water absorption property.

Figure 16 .
Figure 16.The effect of (a) fiber loading as a function of matrix (b) fiber loading as a function of filler and (c) matrix loading as a function of filler on water absorption property.

Table 1 .
Proportion of the mixtures using mixture optimal design of expert and sample codes.

Table 2 .
Rectangular Shaped Specimen Dimension for impact testing.
deformation, indentation, or scratching.The Rockwell, Brinell, and Viker hardness are the most common testing techniques.For this research, Rockwell hardness testing (BROOKS Hardness Tester MAT10/RAB) is used.

Table 3 .
Test results of the average mechanical property and water absorption.