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Abstract

In this work, the thermal stability of wood flour (WF) was modified using a boric acid treatment. To further understand the impacts of incorporating various proportions of titanium dioxide (TiO₂) nanoparticles loaded on polycarbonate (PC)/wood flour. The rheological, mechanical, thermal, electrical, and interfacial properties were studied. Various properties of the resultant PC/WF/TiO₂ nanocomposites were then characterized. The viscosity of the nanocomposite was shown to decrease with shear rate and temperature. XRD investigation indicated that, by introducing TiO₂ nanoparticles into PC/WF, the amorphous phase decreased, and the degree of crystallinity increased, as compared to bare PC/WF, from 65.78 to 42.29. In addition, the TGA profile showed that the nanocomposites have a higher resistance to thermal degradation than PC/WF alone. It was observed that the char residue resulting from the TGA of PC/WF/10%wt TiO₂ increased to 5.69% compared to pure PC/WF (1.32%). It was found that an appropriate amount of TiO₂ in PC/WF caused a significant increase in tensile strength, elongation at break, and on impact strength. These were attributed to an increase in the interface of the dispersed phase. The incorporation of nanoparticles enhanced the thermal conductivity of the nanocomposites, which was found to be higher when a TiO₂ content of ∼3 wt% was used. The electrical conductivity of the PC/WF/TiO₂ nanocomposite (<3 wt%) hindered the movement of free-moving ions, therefore reducing the nanocomposite’s electrical conductivity. However, at > 3 wt% of TiO₂, due to the aggregation of nanoparticles, TiO₂ nanoclusters formed in the PC/WF composite. Therefore, the additional space so created for the movement of conduction ions at the interface may have resulted in increased ion mobility. This could be the one of explanations for the increased electrical conductivity associated with higher wt% of TiO₂. Results showed that treating the PC/WF/TiO₂ nanocomposites with boric acid decreased both the rate of heat release and the total heat release.

Keywords

Nanocomposites reinforcement agent rheological behavior mechanical properties thermal conductivity electrical conductivity

Introduction

As an engineering plastic, polycarbonate is a durable, versatile building material used in a lot of construction projects. It can be used both indoors and outdoors in residential, commercial, and industrial applications such as in skylights, windows, partitions, and domes. There are many reasons engineers, architects, and designers like building with polycarbonate panels. Some of these reasons are that they are lightweight and sturdy, come with high-optical clarity, high-impact and high-heat resistant, and extremely flame resistant.¹ PC is also insensitive to moisture and durable to various weather conditions.² Consumer electronics, automobiles, medical apparatus and instruments, structures, packaging, and other areas have all made extensive use of this material.³ Many additives have been combined into PC-based materials to expand its application domains and overcome its limitations, such as has poor abrasion properties, scratch resistance, high cost, and hard coating. Manufacturers and researchers are interested in wood-polymer composites (WPCs) made of biomass fibers and polymers because of their advanced, environmentally friendly attributes, biodegradability, and antiseptic properties.⁴ They have been widely employed in the automotive, transportation, construction, and decorative industries.⁵ Wood flour (WF), is used to prepare the organic fillers to form wood-plastic composites. Furthermore, wood flour a kind of biomass material that is environment-friendly, and low density with low cost, making it an excellent choice as a filler, improving toughness and energy recovery, causing lower pollutant emissions, and lowering non-renewable sources usage.⁶ Ahlem et al.⁷ investigated the addition of TiO₂ nanoparticle to polypropylene and its effect on the material’s thermal, rheological, and crystallinity levels. It was discovered that TiO₂’s influence is strongest at low frequencies, and because of shear thinning, the relative effect decreases as frequency increases. The polymer chains' entangled state precludes shear flow at lower frequencies, which results in high viscosity. The mean interparticulate distance is high at 2.5wt% TiO₂, which causes a slightly increase in viscosity due to a minimal hydrodynamic disruption. The complex viscosity significantly reduces with the nanoparticle concentration when 5wt% TiO₂ is added to polypropylene. The complex viscosity decreases at greater TiO₂ contents (>5Wt%). Since TiO₂ nanoparticles agglomerate at larger concentrations, this decline is probably caused by it. The surface that the nanocharge has with the polymer matrix is reduced as a result of this agglomeration. Zhang et al.³ showed that the wood flour dispersed in the polycarbonate matrix as micro or nanoparticles. The introduce of treated wood flour with boric acid increased the thermal stability of the resulting composites. The flexural and tensile modulus linearly increased with the increase of wood flour content by 147.2% from 3.6 GPa for pure PC to 8.9 GPa for the WPCC40 and 27.7% while the tensile modulus increased by 129.6%, respectively. This increase can be ascribed to the stiffness of the wood flour. Meanwhile, the addition of wood flour would reduce the cost of PC composites. However, both biomass fibers and polymers are inherently ignitable, which means that WPCs carry a considerable fire risk. Hence, it is important to decrease the flammability of WPCs to expand their commercial utilization. Generally, flame-retardants and non-combustible particles are added to WPCs to improve their flame retardancy.⁸ Titanium dioxide is a critical inorganic filler/reinforcement agent material used in polymer composite materials. It sees widespread use in a variety of applications, such as optoelectronic and photocatalytic activities, electrochromic applications, hydrogen storage, and gas sensors.^9,10 Inorganic reinforcing agents such as titanium dioxide are added to thermoplastics to improve their mechanical characteristics such as yield stress and modulus of elasticity. On the other hand, increasing the proportion of reinforcing agent content might result in a substantial loss of impact strength and elongation at break. According to Zhenhua,¹¹ composites made of poly(methyl)methacrylate (PMMA) and titanium dioxide were created in a variety of concentrations. On the mechanical characteristics and thermal behavior of PMMA composite film, the impacts of fiber content and modification were examined. When used as a binary modifying agent for TiO₂ filler, organosolv lignin and acrylic acid enhanced the strength and ultimate strain of treated PMMA composites relative to untreated ones. Chaisaenrith and Pavasupree conducted a thorough investigation of the impact of titanium dioxide (TiO₂) on the flame retardant char-forming effect of ammonium polyphosphate in polypropylene. An intumescent nitrogen-containing resin was also used. Titanium dioxide improved the fire resistance by making the material stronger, forming more char with a higher expansion and an increased porosity.¹² The results of using nano-titanium dioxide to manufacture paint and flame-retardant coatings revealed the product’s excellent antipollution properties and flame resistance.¹³ The impact of fillers like mica and fly ash, at various concentrations, on the mechanical, thermal, electrical, rheological, and morphological characteristics of polyester thermoplastic elastomer were investigated by Sreekanth et al.¹⁴ The goal of this work is to find an optimal reinforcement agent content (TiO₂) with good dispersion that can be added to the PC/WF composite while considering various issues such as rheological, mechanical, thermal, and electrical properties. To modify TiO₂ nanoparticles, a silane coupling agent (3-aminopropyltriethoxysiane, APTES) was to improve the TiO₂ dispersion and interfacial adhesion between the TiO₂ and PC/WF composite. As a result, the viscosity of the nanocomposites increased. This finding an agreement with reported literature.¹⁵ Figure 1 displays several factors that may affect the mechanical, rheological, electrical, and thermal properties of nanocomposites and organic/inorganic fillers to be valuable material in electronics, automobiles, medical apparatus and packaging for hydrocarbon liquid such as oil which used in lubricating.

Figure 1.

The factors that impact the mechanical, rheological, electrical, and thermal properties of nanocomposites materials.

Experimental

Materials

Commercial polycarbonate with a melt index at 300°C of 19.6 g/10 min, a polydispersity of 2.16 weight, a glass transition temperature of about 144.5°C, a density of 1.20 gm/cm³, and with an average molecular weight, M_w, of about 57,404, was supplied by BASF, Germany. Commercial wood flour, 120 mesh sieves (125 μm) purchased from Ontario Sawdust Supplies was used as a filler. The moisture content of the WF was estimated by ASTM D4442 to be 5–6 wt. Commercial titanium dioxide, as supplied by Sigma Aldrich and with a particle size of 60.41 μm, was used as nanoparticle. 3-aminopropyltriethoxysiane (APTES) was purchased from Sigma Aldrich.

Wood flour modification

Wood flour was immersed in a 5 wt% boric acid solution for 4 h. The solid-to-liquid ratio was 1:4. The treated WF was then filtered and oven-dried for 24 h at 110°C to release the last of the moisture content. The control group was treated with deionized water before being oven-dried for 24 h at 110°C.

Surface modification nanoparticles of TiO₂

PC, WF, and TiO₂ particles were dried in a vacuum oven at 80°C for 12 h to decrease the amount of absorbed moisture on their surfaces. To ensure thorough dispersion, 4 g of TiO₂ nanoparticles were ultrasonically dispersed for 25 min in a mixed solution of 100 mL anhydrous ethanol and 40 mL deionized water. 0.4 g of hydrolysis-treated APTES was added to each sample. The pH of the solutions was gradually elevated to 5 and 10 using ultrasonic treatment at 50°C for 2 h. The dispersed particles were then separated from the solvent using a centrifuge (10 min at 10,000 rpm), followed by washing with ethanol and water alternately for at least two cycles to remove excess silanes. To re-disperse the centrifuged particles in fresh solvent, they were put in ultrasonic bath for more than 15 min to make sure a visually well dispersed suspension was regained before centrifuging again. The modified TiO₂ nanoparticles were dried in a vacuum oven at 80°C for 12 h. 2 g of modified TiO₂ nanoparticles were added to the PC/WF particles and dispersed with a stirring at speed of 300 rpm for 3 h in mild anhydrous ethanol. Modified PC/WF/TiO₂ particles were generated after drying the mixes for 12 h at 80°C. The modification of APTES on the TiO₂ nanoparticle surface is depicted in Figure 2.

Figure 2.

Chemical grafting of coupling agent (APTES) onto TiO₂ nanoparticles surface.

Preparation of specimens

To prepare the PC/WF-TiO₂ nanocomposites, the PC pellets were first oven-dried by heating at 60°C for a day to eliminate its moisture content before extrusion. The amount of PC/WF was estimated using the requisite ratio of PC/WF to TiO₂. Next, in a multistage stretching extrusion with a single screw extruder, diameter was 25 mm and length-to-diameter ratio of 30. Temperature profiles from the feed zone to the die zone were set at 200, 210, and 210°C, with the screw rotating at 30 rpm. The pellets were generated from the extrudates and were 1.5–2 mm in diameter. The extruded sheets were quenched in water before being cut and placed in a 115 mm mold to prepare the samples for all measurements. To make a 3–4 mm thick sheet, the cut sheet was hot pressed between hydraulic presses at 200°C. To allow the mix to melt and spread out between the plates, a pressure of 20 kg/cm² was applied for 5 min. The mold sheet was removed and quenched in room temperature water after the pressure was increased to 200 kg/cm² for an additional 5 min. Table 1 summarizes the details of PC/WF/TiO₂ nanocomposites.

Table 1.

Identification of abbreviations for PC/WF/TiO₂ nanocomposites.

Composites	PC/WF (wt%)	Nanoparticle (wt%)
PC/WF/TiO₂	80/20	—
PC/WF/2wt% TiO₂	80/20	2
PC/WF/3wt% TiO₂	80/20	3
PC/WF/4wt% TiO₂	80/20	4
PC/WF/5wt% TiO₂	80/20	5
PC/WF/10wt% TiO₂	80/20	10

Rheological measurement

Torque measurement

A Brookfield DV-III Ultra Programmable Rheometer was used for the rheological experiment, which measures the fluid parameters of torque, shear stress, and viscosity at the given shear rates required for polymer melts at three temperatures (230, 250, and 270°C), and five rotational speeds (100, 120, 140, and 180 rpm). PC/WF/TiO₂ and six compositions of their nanocompsites in the ratios of 80/20, 80/20/2, 80/20/3, 80/20/4, 80/20/5, and 80/20/10 were measured. Polymer granules of various compositions were weighed to fill the chamber to 70% capacity. The weighted granules were premixed by tumbling and dried in an oven for 2 days at 80°C. The temperature and rotating speed of the rheometer were programmed using the rheometer’s microcontroller.

Data interpretation for torque and viscosity

The equations from (1)–(9) were obtained from the study by Laguna et al.¹⁶ which was used to investigate torque data in terms of fundamental units. The torque M was plotted as a function of speed (rpm) Ω at constant temperature on a log-log scale, such that

M = C_{o} Ω^{b}

(1)

η_{a} = K {\dot{γ}}^{n - 1}

(2)

where C_o is a constant that varies with machine geometry and temperature and b is a constant of the polymer melt. Because the log M vs. log plots in all cases were straight lines, b is equivalent to the slope of the corresponding straight lines. According to the method used, b can be regarded as an index indicating the degree of non-Newtonian behavior of any fluid that obeys the well-known power law, given by:

τ = K {\dot{γ}}^{n}

(3)

τ = K_{1} M

(4)

\dot{γ} = K_{2} Ω

(5)

K_{1} = \frac{1}{2 π R_{m}^{2} L}

(6)

K_{2} = \frac{2}{n R_{m}^{2 / n} (R_{i}^{- 2 / n} - R_{o}^{- 2 / n})}

(7)where τ and

\dot{γ}

are the shear stress and shear rate, respectively. The chamber constant was calculated using the calibration results reported by Roger et al. For the Brookfield Engineering Laboratories, the effective instrument dimensions were the inner and outer cylinder radii, R_i = 2 cm, and R_o = 2.5 cm, respectively, and the cylinder length, L = 5 cm. Thus, based on torque and speed data, the following correlations were used to calculate shear stress, shear rate, and viscosity of the polymer nanocomposites: The apparent viscosity (

η_{a})

can be computed by dividing the shear stress by the shear rate, or by using the following formula:

η_{a} = \frac{n R_{m}^{2 (1 / n - 1)}}{4 π L} (\frac{1}{R_{i}^{2 / n}} - \frac{1}{R_{o}^{2 / n}}) \frac{M}{Ω}

(8)

M and Ω are given in Dyne cm and s⁻¹ in expressions equation (4), (5), and (8), respectively. As a result, τ is given in Dyne/cm², $\dot{γ}$ is given in s⁻¹ and η_a is given in centipoises (cP). The activation energy of flow at constant shear rate of all PC/WF/TiO₂ nanocomposite compositions was determined using the Arrhenius equation for non-Newtonian behavior of fluid:

η_{a} = A_{i} \exp (E_{i} / R T)

(9)where A_i is the Arrhenius constant, and E_i is the activation energy of flow at constant shear rate

R is the gas constant, and T is temperature.

Characterization of nanocomposites

X-ray diffraction (XRD)

A Bruker D8 Advance with Cu-K_α radiation (λ = 0.15418 nm) was used to record the XRD of synthesized nanoparticles and their PC/WF/TiO₂ nanocomposites. The applied current was 30 mA, and the accelerating voltage was 40 kV. In the step scanning mode, the XRD patterns were scan size of 0.02°/step at a rate of 147.4 s/step.

Thermal property analysis

Thermogravimetric analysis (TGA) was performed to demonstrate effect of TiO₂ nanoparticles on thermal stability of a pure PC/WF. TGA provides measurable information about the weight-loss process. TGA was performed on a TGA Q-50, TA instruments. Approximately 10 mg of the samples were heated from ambient to 800°C at a heating rate of 20 °C/min in a nitrogen atmosphere introduced at a flow rate of 80 mL/min.

Mechanical properties measurement

Impact strength tests

The impact strength is measured according to GB1043-79 standard test. The machine used is CHARPY XCJ-40-. The following relationship was used to calculate the impact strength:¹⁷

G_{c} = U_{c} / A

(10)where G_c is the impact strength (kJ/m²), U_c is the fracture energy (kJ) determined by the Charpy impact test instrument, and A is the specimen’s cross-sectional area (m²).

Hardness tests

Shore A hardness was determined using a ZWICK hardness machine, which is available at the National Company for Chemical and Plastic Industries. Tester type 7901 was used, and the test was performed in accordance with DIN 53505, ASTM (D1706-61), and ISO DR 988.

Tensile strength tests

Tensile properties were determined on a dumbbell-shaped die-cut sample using an Instron tensile tester machine (model 1445) in accordance with ASTM standards (D638).¹⁸ Specimens were cut and their thickness measured using a micrometer with a resolution of 0.025 mm (0.001 inch).

Thermal conductivity measurement

The thermal conductivity of the PC/WF/TiO₂ nanocomposite was measured using Lee’s disk technique, with the nanocomposites placed between two brass plates (plate a, plate b). The experiment’s heat source was a constant voltage and current of (6 V and 0.25 A), respectively. The following are the thermal conductivity equations (11)–(13)¹⁹:

H = I . V

(11)

H = π r^{2} e (T_{A} + T_{B}) + 2 π r e (d_{A} T_{A} + d_{s} \frac{1}{2} (T_{A} + T_{B}) + d_{B} T_{B} + d_{C} T_{C}

(12)where H is the average time to apply energy to heat the coil, and T_A, T_B, and T_C are the temperatures of disks A, B, and C, respectively. Moreover, d_A, d_B, and d_C are disk A, B, and C’s thicknesses, respectively, d_S is the thickness of Sample S, r is the disk diameter, I is the current flow, V is the supply voltage, and e is the amount of thermal energy that flows over the disks’ cross section per second.

K (\frac{T_{B} - T_{A}}{d_{s}}) = e (T_{A} + \frac{2}{r} (d_{A} + \frac{d_{s}}{4}) T_{A} + \frac{1}{2 r} d_{s} T_{B})

(13)where K is the thermal conductivity.

Electrical Measurement

Discharging a high voltage through a PC/WF composite linked with TiO₂ was used to evaluate its electrical characteristics. At ambient conditions, DC electrical conductivity was measured using the usual four-probe technique. Four similarly spaced probes are placed on the material in this procedure. A current source produces an increasing current, I_o. A voltmeter may be used to detect the voltage drop ΔV across the two inner probes when I_o flows through the two outer probes. The electrical resistivity, R_e, may then be calculated as the gradient of a voltage versus current plot. The specimens were 10 mm in diameter and 1 mm in thickness. The following equation may be used to calculate the resistance of a given sample²⁰:

R_{e} = \frac{Δ V}{I_{o}}

(14)

Cone calorimeter

Cone calorimeter (CONE) tests were conducted in accordance with ASTME 1354-2009 standard. The specimen was covered with aluminum foil and positioned horizontally with an external heat flux of 50 kW.m-2. The specimen’s measurements were 100 × 100 × 3 mm^-3.

Results and discussion

Shear stress versus shear rate plots

A log-log plot of τ versus $\dot{γ}$ for pure PC/WF doped with TiO₂ and their nanocomposites at three temperatures (230, 250, and 270°C) is shown in Figure 3(a)–(c). As measured shear stress forces do not increase linearly and decay at high shear rates, this is a characteristic of shear thinning polymer solutions, where high shear rates induce polymer chain alignment, lowering the solution’s resistance to flow. This means that the power law governs the shear stress-shear rate connection, equation (2). The shear stresses of the TiO₂-containing nanocomposites were obviously greater than those of the PC/WF-free TiO₂ at a fixed shear rate, and this parameter can be shown to increase with increasing TiO₂ content. This suggests that TiO₂ increases shear stress, and that this increase is proportional to the weight fraction. Similar findings have been made in other linked systems.^21,22 At greater shear rates, the flow curves of the nanocomposites start to converge. Variations in TiO₂ loading may have a lesser influence on flow curves at higher shear rates than at lower shear rates. At high shear rates, the reinforcing agent-composite phase contact force is overcome, permitting polymer flow and TiO₂ nanoparticle movement. The reinforcing agent particles may also help to reduce polymer chain entanglement, allowing for better flow.²³ At lower temperatures, the difference between the flow curves was higher, and all of the curves were well separated; however, separation diminishes with increasing temperature and shear rate. This trend may imply that the convergence of the curves at higher shear rates and temperatures is attributable to a decrease in chain entanglement and increased orientation of the PC/WF chains generated by the TiO₂ nanoparticles. Furthermore, the gap between the curves was more prominent at lower shear rates. In the presence of TiO₂ nanoparticles, this tendency may be linked to the relative dominance of extensional flow over shear flow. Extensional flow prevails at low shear rates, generally less than 1000 s⁻¹, whereas shear flow dominates at higher shear rates.²⁴ The presence of TiO₂ nanoparticles produces heterogeneity and discontinuity in the PC/WF, impeding flow. The power law index (n) versus titanium dioxide reinforcing agent contents (2, 3, 4, 5, and 10 wt %) at three distinct temperatures of 230, 250, and 270°C is shown in Figure 4. The gradient of log-log plot of τ versus $\dot{γ}$ for TiO₂-doped PC/WF nanocomposites may be used to derive the power law exponent (n) in each example. The values of n were all less than one, showing that all composite compositions display pseudoplastic behavior. At all temperatures investigated, n reduces as the proportion of reinforcing agent increases, demonstrating that the TiO₂ nanoparticles improve the shear thinning capabilities of PC/WF. This might be the case because the TiO₂ nanoparticles limit pure PC/WF chain entanglement, allowing molecules to be more readily orientated in the flow direction. The increased ‘n’ values increase in temperature for nanocomposite compositions are indicative of decreased resistance to flow of the polymer filled with WF because of the increased thermal motion of the polymer chains. The polymer melts tend more towards Newtonian behavior. These findings corroborate those of Wolcott et al.²⁵

Figure 3.

Log-Log plots of shear stress versus shear rate for PC/WF/TiO₂ nanocomposites at (a) 230°C, (b) 250°C, and (c) 270°C.

Figure 4.

The power law index versus percentage weight of TiO₂ (2, 3, 4, and 10 wt%) at various temperatures (230, 250, and 270°C).

Apparent viscosity

Equation (7) was used to calculate the apparent viscosities of the mixes. The apparent viscosity rose quickly with increasing amounts of reinforcing agent, especially at low shear rate. This phenomenon can be described in terms of TiO₂ nanoparticle interactions, which tend to attract the TiO₂ nanoparticle into unfavorable to flow orientations, resulting in increased viscosity. At low shear rates, the composite viscosity appears to be driven primarily by the strength of the bonding in the network structure, which appears to be temperature independent. These findings are consistent with those reported by Parvaiz.²⁶ All synthetic nanocomposites reveal a shear thinning nature that increases proportionally with polymer concentration, a characteristic reflected by the decayed increase in measured shear stress forces with increasing shear rates,²⁷ as shown in Figure 5(a)–(c). The apparent viscosity of the PC/WF/TiO₂ nanocomposites was found to be higher than that of PC/WF with increasing the content of TiO₂ in the mix. Thus, when shear rate increases, molten state may be gradually sheared away, resulting in a decrease in intermolecular interactions and, as a result, a decrease in apparent viscosity.²⁸ The influence of temperature on nanocomposite viscosity at high shear rates may be shown as follows: when particle contacts are larger, alignment is greater, and viscosity is lower. These results are in good agreement with those reported by Abbas et al.^29,30 As the temperature rises, the viscosity drops because viscous stresses prevail.

Figure 5.

Log-Log plots of apparent viscosity (η_a) vs. shear rate for PC/WF/TiO₂ nanocomposites at (a) 230°C, (b) 250°C, and (c) 270°C.

Activation energy

The activation energy (EA) was calculated from log η_a versus inverse temperature gradients at five shear rates (

\dot{γ}, (s^{- 1})

), as shown in Table 2. The EA initially decreased slowly until 2wt% TiO₂ had been added, and then, as the TiO₂ loading increased further, the activation energy of the PC/WF doped with TiO₂ nanocomposites increased up to 3wt% and then decreased at 4, 5, and 10 wt% TiO₂. This means that the activation energies of the nanocomposites are affected by the TiO₂ dispersion in the PC/WF composite. The activation energy is proportional to the energy barrier that prevents the PC (polymer) and WF as filler from moving from one location to another. The interaction strength between TiO₂ and the PC/WF composite is primarily determined by the properties of their interface. As a result, the observed increase in the activation energy of the nanocomposites indicates not only an increase in the dispersion of the PC/WF and TiO₂, but also an improvement in interfacial adhesion. This is consistent with the findings reported in the literature.³¹ Consequently, the activation energy increased to a high of 8.465 kJ mol⁻¹ when the nanocomposite’s TiO₂ concentration was 3wt%, after which it declined to a minimum of 3.506 kJ mol⁻¹ with the PC/WF/TiO₂ system having 10wt% TiO₂. This result shows that the addition of a small quantity of TiO₂ nanoparticles to this polymer improved the thermal stability of PC/WF, especially when the percentage of TiO₂ in the composite reaches 3wt%. Due to the reduced energy needed for bond scission and unzipping of PC/WF/TiO₂ nanocomposites, the EA value decreased as the nanoparticle loading of the composites increase.³²

Table 2.

Activation energy of flow at constant shear rates of 210–490 s⁻¹ for various compositions of PC/WF/TiO₂ nanocomposites, as determined by the Arrhenius equation.

TiO₂ wt% in PC/WF	EA (KJ mol⁻¹) at constant shear rate (s⁻¹)					Total EA kJ mol⁻¹
TiO₂ wt% in PC/WF	210 (s⁻¹)	317.5 (s⁻¹)	367.5 (s⁻¹)	419.5 (s⁻¹)	490 (s⁻¹)	Total EA kJ mol⁻¹
-	1.478	1.567	1.589	1.685	1.608	7.927
2	1.471	1.508	1.578	1.592	1.500	7.649
3	1.612	1.616	1.610	1.734	1.893	8.465
4	1.434	1.399	1.585	1.496	1.719	7.633
5	1.229	1.283	1.209	1.454	1.626	6.801
10	0.541	0.603	0.610	0.794	0.958	3.506

XRD characterization

As shown in Figure 6, bare PC exhibits a broad diffused diffraction peak at around 2θ = 17.8°, demonstrating that PC is an amorphous polymeric material with amorphous phases or microcrystals. This could be because the polymer-shaped crystals are frequently microcrystalline structures with small crystallite sizes.³³ In addition to the above aforementioned, the aggregation of chain portions as a result of microphase separation in PC.³⁴ Wood flour had no effect on the crystalline behavior of the PC/WF (Figure 6). After incorporating WF in the PC framework, a broad diffraction peak at 2θ = 17.8° was observed, demonstrating that the PC in the nanocomposites was amorphous. This finding is completely consistent with that of Shuang et al.³⁵ The crystalline peaks attributed to TiO₂ nanoparticles incorporated into PC filled with WF became increasingly apparent when TiO₂ loadings, as a reinforcing agent in the pure PC/WF, were increased. This demonstrates that TiO₂ nanoparticles successfully fill in the PC/WF/TiO₂ nanocomposite and retain the original crystal structures in the nanocomposites.³⁶ The rutile phase of TiO₂ was assigned the appearance of these prominent diffraction peaks centered at 2θ values of 27.7°, 36.7°, 41.2°, 54.4°, and 69.3°, according to TiO₂ standard card JCPDS No:21-1276.³⁷ The degree of crystallinity of PC/WF increases as the TiO₂ nanoparticle loading increases. Heterogeneous crystallization is responsible for the increase in crystallinity. TiO₂ nanoparticles function as nucleating agents for PC/WF during crystallization. Furthermore, increasing the TiO₂ content increased the degree of crystallinity of the nanocomposites. This TiO₂ concentration-dependent increase in crystallinity in nanocomposites was attributed to faster nucleation effects. PC/WF/TiO₂ nanocomposites containing 2.0 and 3.0 weight fractions of TiO₂ demonstrated the best crystallinity; nevertheless, the crystallinity of the nanocomposites deteriorated as TiO₂ concentration increased past the above. The occurrence of a decreased degree of crystallinity with increasing TiO₂ content after 3 wt% was related to TiO₂ aggregation, where extremely uniform dispersion of TiO₂ could develop stronger interactions in the PC/WF matrix, inducing rapid nucleation and growth.³⁵ The increase order as follows:

Figure 6.

XRD patterns for PC, WF, TiO₂, and PC/WF/TiO₂ nanocomposites with various TiO₂ content.

PC/WF/2%wt TiO₂ > PC/WF/3%wt TiO₂ > PC/WF/4%wt TiO₂ > PC/WF/5%wt TiO₂ > PC/WF/10%wt TiO₂ > PC/WF (65.78, 63.21, 59.39, 57.56, 50.68, and 42.29). A shift to lower angles of the characteristic diffraction peak in the TiO₂ doped PC/WF nanocomposites and suggests an increase in interlayer spacing of the TiO₂, which is resulting in as intercalation.³⁸

Thermal property analysis

Thermogravimetric analysis (TGA) study was carried out to examine TiO₂’s impact on flame retardancy. By triggering the changes in mass of a sample of material over time as a function of temperature and time, thermogravimetric analysis was used to study the thermal degradation process of polymers. Interfacial interaction plays a crucial role in the degradation of polymeric nanocomposites, i.e., an excellent interfacial interaction allows particles to act as restriction sites for the mobility of a polymer chain, makes the scission of a polymer chain harder at lower temperature, and therefore shifts the degradation temperature of the material to higher temperature. Nevertheless, better interfacial interaction between additives and polymer chain introduced by the deeper penetration of smaller particles in the polymer matrix will also restrict the mobility of the polymer chain. ‘‘Deeper penetration’’ means that a further interaction between nano-scale particles and polymer chain segments occurs, beyond the simple interaction between nano-particles and polymer chains. Figure 7(a) depicts the TGA curves for PC/WF and PC/WF/TiO₂ nanocomposites (2%, 3%, 4%, 5%, and 10 wt%). As can be observed, the samples degrade in two stages. In addition to the evolution of H₂O and CO₂ over the entire mass loss range, alcohols, ethers, and carbonates are predominantly found at the first stage of PC thermal degradation, and the carbonates produced undergo rearrangements and eventually char during the second stage.³⁹ Some easily degradable wood elements, on the other hand, such as hemicellulose and extractives, deteriorated throughout the melting process.³ Table 3, thermal data obtained from TGA thermograms of the PC/WF and PC/WF/TiO₂. TGA curves showed that nanocomposite have higher resistance to thermal degradation compared to PC/WF and it reveals to increase as the TiO₂ loading increases. Moreover, variations in the DTG temperature as a function of TiO₂ nanoparticle content are represented in Figure 7(b). The PC/WF composite starts to decompose at 460.15°C, with the process complete at 659.77°C, which is lower than the PC/WF/TiO₂ nanocomposites (Figure 7(b)). T_onset and T_endset for the nanocomposites were both shifted to higher temperatures as compared to the PC/WF, which had a smaller char residue (1.32%). The higher adhesion force at the PP/WF/TiO₂ interface may be responsible for the rise in onset and endset temperatures. Particles with high interfacial interactions can impede the mobility of polymer chains, making polymer chain scission harder at lower temperatures. As a result, the nanocomposite’s degradation temperature shifts to a higher temperature.⁴⁰ With the addition of TiO₂ nanoparticles, the temperature at which maximum degradation rate occurs is raised as compared to PC/WF. For reinforced nanocomposites, residue amounts to 1.85%, 2.35%, 3.12%, 3.98%, and 5.69% for TiO₂ loadings of 2, 3, 4, 5, and 10 wt%, respectively. This demonstrates that the samples treated with a flame retardant (TiO₂) created noticeably more solid residues, the char’s surface was more compact. Heat is successfully kept from penetrating the substrates. This observation is consistent with the literature.⁴¹

Figure 7.

Thermal analysis of pure PC/WF with and without TiO₂ (a) TGA and (b) DTG.

Table 3.

Thermal data determined from DTG thermograms of pure PC/WF and PC/WF/TiO2 nanocomposite.

Sample name	T_onset (^oC)	T_endset (^oC)	T_max (^oC)	Char residue (%)
PC/WF	460.15	659.77	497.36	1.32
PC/WF/2wt% TiO₂	475.37	698.68	565.03	1.85
PC/WF/3wt% TiO₂	548.12	691.92	566.72	2.35
PC/WF/4wt% TiO₂	532.89	718.98	576.87	3.12
PC/WF/5wt% TiO₂	561.65	747.74	583.64	3.98
PC/WF/10wt% TiO₂	570.11	784.96	593.79	5.69

T_onset: Degradation temperature.

T_endset: End of decomposition.

T_max: Maximum degradation rate obtained from a derivative mass loss curve.

Char residue: Mass residue left from the samples.

Mechanical properties

A functional composite must have a certain mechanical strength across a wide range of applications. The impact strength, tensile strength, and elongation at break of the PC/WF/TiO₂ nanocomposites initially increased and then decreased with increasing TiO₂ fraction. The nanocomposites generally performed well when the TiO₂ content was set at 3 wt%, as this optimal amount of TiO₂ had a toughening effect on the PC/WF and optimal interfacial compatibility between the TiO₂ nanoparticle and the matrix, as shown in Figure 8. The TiO₂ content was found to affect the change in impact strengths of the PC/WF composites. It can also be seen that the TiO₂ fraction and its state of dispersion had a significant impact on the toughness of the materials. A smaller amount of TiO₂ filling improved the hybrid materials' impact strength, but as its fractional weight increases the impact strength decreases significantly, as shown in Figure 8(a). This phenomenon can be explained by changes in TiO₂ dispersion; finer dispersion reduces impact strength to a lesser extent.⁴² Figure 8(b) also shows the utilization of PC/WF doped with TiO₂ nanoparticles. With increasing TiO₂ content rather than 3wt%, the harnesses of PC/WF/TiO₂ nanocomposites decreased as shown in Figure 8(b). This decrease indicates that as TiO₂ loading increases, the nanocomposite become brittle due to the stress concentration effect of TiO₂. Hardness decreases with increasing TiO₂ content due to the formation of cracks around the TiO₂ nanoparticles and the potential formation of particle agglomerates and voids, resulting in local matrix detachment from the particles.⁴³ As shown in Figure 8(c), the tensile strength of PC/WF composites increase with increasing TiO₂ content. This is due to mechanical anchorage between the TiO₂ and the PC/WF. As a result, interfacial adhesion is critical in increasing the tensile strength of composites. The greater the composite’s interfacial adhesion, the greater the stress that can be transferred to inorganic particles from the matrix, resulting in higher tensile strength.⁴⁴ Tensile strength is reduced when the nanoparticle level exceeds 4% by weight, at which point larger agglomerates of nanoparticles can be formed as displayed in Figure 8(c). The decreased tensile characteristics of nanoparticle-reinforced PC/WF could be attributed to the decreasing surface area of the higher particle loading (larger agglomerates) through a less efficient stress transfer mechanism.^45,46 Figure 8(d) also shows that the elongation required to break the nanocomposites has a strong relationship with the interfacial properties of the PC/WF. The elongation to break the coupled PC/WF-treated, particle-reinforced nanocomposites increased dramatically when compared to the neat matrix. A reduction in elongation to break nanocomposites with more than 3wt% TiO₂ is to be expected due to the development of cracks around the TiO₂ nanoparticles and the possible formation of particle agglomerates and voids, resulting in local matrix detachment from the particles.⁴³

Figure 8.

Mechanical variations of: (a) impact strength, (b) hardness (Shore A), (c) tensile strength, and (d) elongation at the break of the pure PC/WF as a function of the TiO₂ content in wt%.

Based on the associated mechanical properties PC/WF/TiO₂ nanocomposites, a TiO₂ concentration of 3wt% was found to be optimal in PC/WF composites resulting in limited the polymer chains thereby strengthen the interface between TiO₂ and PC/WF. This is confirmed by activation energy results (refer Table 2).

Regression analysis of impact strength and hardness reveals multiple R and R square values of 0.99 and 0.99, respectively, while the standard error and significant F obtained are 0.0085 and 0.029, respectively, demonstrating the remarkably good co-relationship up to 3wt% of TiO₂ nanoparticle reinforcement as listed in Table 4. Beyond 3wt% TiO₂, multiple R and R square values are obtained to be 0.79 and 0.63, respectively, whereas the standard error and significant F obtained are 3.54 and 0.64, respectively, showing poor co-relation between them as given in Table 4. The large standard error and significant F could have occurred due to fact that the composite and nanoparticle material might not have mixed homogeneously and air voids could have produced during processing preparation of specimens using extruder.⁴⁷ which shows the weak co-relationship between them.⁴⁸ Similarly, impact strength and tensile strength display good co-relationship up to 3wt% TiO₂ nanoparticle reinforcement. Multiple R and R square values are found to be 0.99 and 0.99, respectively, while the standard error and significant F obtained are 0.11 and 0.63, respectively, which shows an incredibly good co-relationship as shown in Table 5. The regression analysis beyond 3wt% TiO₂ nanoparticle reinforcement, multiple R and R square values are obtained to be 0.78 and 0.63, respectively, while the standard error and significant F obtained are 2.78 and 0.42, respectively, which shows the weak co-relationship⁴⁹ between them as shown in Table 5. Based on above, the same tendency of regression analysis of impact strength and elongation at break at low and high TiO₂ nanoparticle as shown in Table 6.

Table 4.

Regression analysis of impact strength and hardness.

Regression statistics
Filler reinforcement: >3 wt%		Filler reinforcement: <3 wt%
Multiple R	0.999995908	Multiple R	0.791897955
R square	0.999991816	R square	0.627102371
Adjusted R square	0.999975449	Adjusted R square	0.254204743
Standard error	0.008462128	Standard error	2.776067541
Significance F	0.002860721	Significance F	0.418186291

Table 5.

Regression analysis of impact strength and tensile strength.

Regression statistics
Filler reinforcement: >3 wt%		Filler reinforcement: <3 wt%
Multiple R	0.999340627	Multiple R	0.769061006
R square	0.998681689	R square	0.591454832
Adjusted R square	0.996045066	Adjusted R square	−0.225635505
Standard error	0.107402155	Standard error	3.544398951
Significance F	0.036308555	Significance F	0.639175382

Table 6.

Regression analysis of impact strength and elongation at break.

Regression statistics
Filler reinforcement: >3 wt%		Filler reinforcement: <3 wt%
Multiple R	0.998998146	Multiple R	0.880595415
R square	0.997997295	R square	0.775448285
Adjusted R square	0.993991885	Adjusted R square	0.625747141
Standard error	0.132376995	Standard error	2.083586609
Significance F	0.044751592	Significance F	0.10640807

The quantification of the interfacial interaction of PC/WF/TiO₂ nanocomposites

The interfacial adhesion between the TiO₂ nanoparticles and the composite has a significant impact on the mechanical properties of the composites, particularly the tensile strength. Pukanszky et al.⁵⁰ created a model to predict the variation in the yield stress of a composite with the particulate TiO₂ nanoparticle fraction using equations (15)–(17).

σ_{y c} = [(1 - ϑ_{f}) / (1 + 2.5 ϑ_{f})] σ_{y m} \exp (β ϑ_{f})

(15)where σ_yc and σ_ym are the tensile strengths of the PC/WF/TiO₂ and PC/WF, respectively,

ϑ_{f}

is the weight fraction of the TiO₂ nanoparticles, and β is a semiempirical parameter that accounts for the macroscopic interface or interphase characteristics affecting the nanocomposite’s yield stress.⁵¹ The magnitude of the β parameter reflects the interfacial adhesion between the TiO₂ nanoparticles and the composites, with a larger β indicating stronger interfacial adhesion.^51,52 We introduce relative tensile strength (φ) as follows

φ = \frac{σ_{y c}}{σ_{y m}} [(1 + 2.5 ϑ_{f}) / (1 - ϑ_{f})]

(16)

φ = \exp (β ϑ_{f})

(17)i.e.,

parameter β values for various PC/WF/TiO₂ nanocomposites which were obtained from the gradient of the plot of ln(φ) versus $ϑ_{f}$ gives a linear dependence. Figure 9 depicts the linear relationship between composite samples' relative tensile strength and TiO₂ nanoparticle content. When comparing our findings to those of previous studies (β = 5.48),⁵³ it can be seen in Figure 9 that the PC/WF/TiO₂ (β = 6.24) has a larger interfacial interaction. However, PC/WF reinforced with TiO₂ with good dispersivity is beneficial to the formation of the interfacial layer, which is consistent with the WAXD results, and will primarily increase the interfacial interaction and then improve the mechanical properties.^44,51

Figure 9.

Ln(φ) versus weight fraction curves of PC/WF as a function of TiO₂ content in wt%.

The regression analysis of quantity with impact strength, hardness, tensile strength, and elongation at break reveal as a function of wt% TiO₂ nanoparticle reinforcement. The regression results of Multiple R, R square, and standard error are close to unity, while significant F found less than 0.05 as shown in Tables 7–10. These results revealed an incredibly good co-relationship.⁴⁹

Table 7.

Regression analysis of quantity and impact Strength.

Regression statistics
Multiple R	0.959601003
R square	0.920834084
Adjusted R square	0.868056807
Standard error	1.23715037
Significance F	0.022274469

Table 8.

Regression analysis of quantity and hardness (Shore).

Regression statistics
Multiple R	0.924359369
R square	0.854440244
Adjusted R square	0.757400406
Standard error	1.677544421
Significance F	0.022274469

Table 9.

Relationship quantity and tensile strength.

Regression statistics
Multiple R	0.929493448
R square	0.86395807
Adjusted R square	0.773263451
Standard error	1.621771862
Significance F	0.050177518

Table 10.

Relationship quantity and elongation at break.

Regression statistics
Multiple R	0.926109332
R square	0.857678496
Adjusted R square	0.762797493
Standard error	1.658779396
Significance F	0.053691531

Thermal conductivity

Figure 10 depicts thermal conductivities of PC/WF/TiO₂ have been determined at various weight concentrations of TiO₂. The value of thermal conductivity increases monotonically with increasing weight fraction of TiO₂ because the addition of the molecular TiO₂ nanoparticle can remarkably improve the adhesion of two-phase interfaces When a thermally insulating polymer like polycarbonate and wood flour are reinforced with any conductive reinforcing agent (having conductivity higher than that of PC/WF) like TiO₂, the thermal conductivity of the nanocomposite starts enhancing and at higher TiO₂ concentrations, the nanocomposite becomes conductive in nature. Initially, at low TiO₂ concentration, since the number of the conductive particles is insufficient to form a continuous conducting path at less than 3wt%, the conductive domains are insulated from each other by the PC/WF medium and the heat conducting behavior cannot be observed. The TiO₂ nanoparticles are isolated by the PC/WF in the case of low TiO₂ content. As the TiO₂ concentration increases, in reinforced PC/WF composites, TiO₂ nanoparticles gradually get connected and conduction network are formed at more than 3wt% of TiO₂. The precise location of the percolation threshold (at 3wt% of TiO₂) is impacted by various factors including the size, aspect ratio and size/spatial distributions of the conductive particles. Immediately after the percolation threshold, a slight increase in the concentration of conductive TiO₂ nanoparticles is found to greatly increase the bridges in the conducting network leading to substantial improvement in thermal conductivity of the composites Further increase (5–10 wt%) in the concentration of the TiO₂ nanoparticles, however, only causes the volume of the conducting domains to increase without any significant increase in the pathways for heat, leading to a monotonic increase in conductivity. These results are in good agreement with previous reported literatures.^54,55

Figure 10.

Thermal conductivity of PC/WF as a function of TiO₂ content in wt%.

Electrical resistivity

Figure 11 illustrates the electrical resistivity of PC/WF with varying TiO₂ concentrations. The electrical percolation threshold is defined as the weight fraction of the TiO₂ nanoparticle at which the measurements begin to show percolation behavior. The amount of filler in the polymer alters the current flow mechanism. A current flow is not achievable with a very low filler concentration (I) because the gap between two TiO₂ particles is too large to allow for quantum tunneling. The gap narrows as the filler content (II) rises, allowing quantum tunneling to occur. When the filler amount is increased even further (III), the filler particles make direct electrical contact.⁵⁶ The TiO₂ aggregates in the PC/WF with a low TiO₂ weight fraction (e.g., 3 wt%) are relatively more separated as the conductive TiO₂ nanoparticle weight fraction approaches the percolation threshold (3 wt% TiO₂ content). Because the distances between the TiO₂ nanoparticles in the PC/WF are relatively large, little, or only slight changes in electrical resistivity can be observed at lower TiO₂ loadings. Increasing the TiO₂ content causes TiO₂ to become more crowded, resulting in a gradual decrease in electrical resistivity. The electrical resistivity decreases dramatically near the percolation threshold, and the material transitions from being insulating to conductive. This indicates that TiO₂ nanoparticles collide or are close enough to allow electron hopping via tunneling, resulting in continuous conductive paths or networks. Because the conductive network has already been established, additional TiO₂ loading does not significantly reduce volume resistivity once the percolation threshold is reached. A further increase in the volume fraction of TiO₂ powder (>4 wt%) narrows the gap slightly, resulting in only a few more conductive channels. As a result, the decrease in resistivity occurs much more gradually. These findings are consistent with those obtained in Lan.⁵⁷

Figure 11.

Electrical resistivity of PC/WF as functions of TiO₂ content in wt%.

Cone calorimeter analysis

To assess the qualities of materials for combustion, the cone calorimeter, based on the oxygen consumption concept, was frequently utilized. Cone calorimeter experiments were used to examine the flammability properties of PC/WF as functions of TiO₂ content (3 and 10 wt%) nanocomposites with and without boric acid (BA). Figure 12 displays the heat release rate (HRR) and the total heat release rate (THR). Boric acid and wood mix to form a novel chemical structure that modifies the way that wood deteriorates under heat.⁵⁸ Boric acid makes it easier for cellulose and hemicellulose to be thermally decomposed into biochar rather than flammable gas. In other words, a boric acid treatment caused more char to remain after burning wood. The layer of carbon that has developed isolates oxygen and heat, slowed the combustion of the composite and reduced its HRR. However, the char layer resulting from wood flour suppressed the HRR of the polymer resin in composites (Figure 12(a)). Similar trends were observed in THR (Figure 12(b)). In comparison to PC, wood flour releases less heat since it has more oxygen and aromatic chemical groups. These results demonstrate that boric acid may reduce the HRR and THR of wood while burning while increasing the flame retardancy of wood flour, along with those observed in the literature.⁵⁹

Figure 12.

Flame–retardant properties of PC/WF as functions of TiO₂ content (3% and 10% wt%) nanocomposites with and without boric acid (BA). (a) Heat release rate (HRR), (b) total heat release THR.

Conclusion

In this study, the thermal stability of wood flour was first enhanced using boric acid treatment and the treated wood flour was then filled into PC and then reinforcement with TiO₂ to prepare PC/WF/TiO₂ nanocomposites with various rutile TiO₂ contents. Meanwhile, their various properties characterized and discussed. The main conclusions obtained are as follows:

1. The addition of TiO₂ nanoparticle to PC/WF improves the rheology processability. As TiO₂ concentration rises, it is observed that perceived viscosity also rises. As a result of the addition of TiO₂ nanoparticles to the PC/WF composite, the viscosity of composites has increased. Besides, the viscosity of nanocomposites decreases as temperature rises.

2. The energy barrier inhibiting the migration of the polymer chain from one place to another is related to the activation energy. As a result, the observed greater activation energy of the composites at 3wt% of TiO₂ indicates that the interfacial adhesion was also enhanced in addition to the polymer and reinforcement agent’s increased dispersion.

3. XRD investigation showed that by embedding TiO₂ nanoparticles into PC/WF, the amorphous phase decreased, and the degree of crystallinity increased compared to bare PC/WF from 65.78 to 42.29 (PC/WF/TiO₂) nanocomposites. Whereas incredibly uniform TiO₂ dispersion can provide stronger interactions in the PC/WF matrix, causing incredibly rapid nucleation and development.

4. The DTG and TGA curves showed that nanocomposites have a higher resistance to thermal degradation than bare PC/WF. The onset, endset, and T_max temperatures of the PC/WF composite thermal degradation were all enhanced by the TiO₂ concentration, however. Consequently, the TiO₂ concentration in metal hydroxide hybridized WPC could be more efficient in enhancing thermal stability against high temperature degradation. It was found the char residue resulted from TGA of PC/WF/10%wt of TiO₂ increased to 5.69% than bare PC/WF (1.32%).

5. TiO₂ nanoparticle addition to PC/WF was studied to see how its effects on mechanical characteristics. Greater impact properties, elongation at break, and tensile strengths are seen in the TiO₂-doped PC/WF composites. The incorporation of 3wt% of TiO₂ nanoparticles into PC/WF composite exhibited to excellent performance in term mechanical characteristics of this mixture.

6. The thermal conductivity of composites reinforced with TiO₂ is greater than that of PC/WF because of the high interfacial thermal resistance between the reinforcement agent and the composite.

7. The electrical conductivity decreases at lower concentration of TiO₂ (<3 wt%) due to the hindrance of ion mobility. The increased conductivity associated with higher concentrations of TiO₂ indicates the formation of more void space at the interface due to the formation of TiO₂ nanoclusters.

8. The thermal stability of nanocomposite materials is increased by boric acid’s promotion of char formation from wood flour. Results obtained show that boric acid may decrease the HRR and THR of burning wood while enhancing the flame retardancy of wood flour.

Footnotes

Declaration of conflicting interests

The author(s) declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article.

Funding

The author(s) received no financial support for the research, authorship, and/or publication of this article.

Data availability statement

All data generated or analyzed during this study are included in this published article’ in the main manuscript

ORCID iD

Abbas Jawad

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Studying the influence of the addition of nano-titanium dioxide on the rheological,mechanical,thermal,and electrical properties of polycarbonate/wood flour

Abstract

Keywords

Introduction

Experimental

Materials

Wood flour modification

Surface modification nanoparticles of TiO2

Preparation of specimens

Rheological measurement

Torque measurement

Data interpretation for torque and viscosity

Characterization of nanocomposites

X-ray diffraction (XRD)

Thermal property analysis

Mechanical properties measurement

Impact strength tests

Hardness tests

Tensile strength tests

Thermal conductivity measurement

Electrical Measurement

Cone calorimeter

Results and discussion

Shear stress versus shear rate plots

Apparent viscosity

Activation energy

XRD characterization

Thermal property analysis

Mechanical properties

The quantification of the interfacial interaction of PC/WF/TiO2 nanocomposites

Thermal conductivity

Electrical resistivity

Cone calorimeter analysis

Conclusion

Footnotes

Declaration of conflicting interests

Funding

Data availability statement

ORCID iD

Appendix

References

Surface modification nanoparticles of TiO₂

The quantification of the interfacial interaction of PC/WF/TiO₂ nanocomposites