Thiamine hydrochloride (vitamin B₁) as modifier agent for TiO₂ nanoparticles and the optical, mechanical, and thermal properties of poly(vinyl chloride) composite films

Abstract

In the present investigation, TiO₂ nanoparticles (NPs) were used for improving the thermal, mechanical and optical properties of poly(vinyl chloride) (PVC) matrix. To prevent the aggregation of TiO₂ NPs, surface modification of TiO₂ NPs was performed using vitamin B₁ as a natural organic molecule with environmentally friendly and inexpensive properties. PVC nanocomposite (NC) films were prepared with different contents of TiO₂ NPs via ultrasonic irradiation as a fast method and then the NCs were investigated using various techniques. Transmission electron microscopy images of NC films showed that TiO₂ NPs were uniformly placed into the polymer matrix. Thermogravimetric analysis results showed enhancement in thermal stability of all NCs. From mechanical tests it was found that increasing the elongation at break and reducing the Young's modulus lead to increasing toughness of NC films. Water contact angle results indicated that the hydrophobicity of NCs were enhanced with increasing the concentration of TiO₂ NPs.

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1. Introduction

Polymer nanocomposites are often defined as the combination of a polymer matrix and additives that have at least one dimension in the nanometer range. The additives can be one-dimensional (examples include nanotubes), two-dimensional (examples contain clay), or three-dimensional (including spherical particles). Over the past decade, polymer NCs have attracted significant attention in both academia and industry, due to their excellent mechanical properties such as elastic stiffness and strength with only a small amount of the nanoadditives. Other preferable properties of polymer NCs include barrier resistance, flame retardancy, scratch/wear resistance, optical, magnetic and electrical properties.¹ Polymer/inorganic NCs due to the large interfacial areas and the strong interfacial interactions have become a significant branch of materials science, chemistry, physics and biology, among other fields, because they often lead to enhanced properties and even new functions compared with the corresponding compounds.² The homogeneous dispersion of inorganic NPs into the organic matrix leads to enhanced mechanical, thermal, and gas barrier properties of NCs at low inorganic content.³ Therefore, polymer/inorganic NCs provide a promising way to successfully combine the advantages of organic and inorganic materials.⁴

Poly(vinyl chloride) (PVC) is one of the most versatile polymers after polyethylene and polypropylene. In addition, it can easily be modified,⁵ excellent corrosion resistance, good flame retardancy,⁶ chemically stable, biocompatible, and inexpensive.^7,8 One of the major problems that limit the practical use of this polymer is its lower thermal stability and brittle properties.^7–9 PVC is unstable when exposed to high temperatures during its application.⁵ To improve these limitations and achieve desired properties, nano-fillers must be distributed uniformly in polymer matrix.⁹ PVC due to good balance price/performance has been allowed to penetrate many applications such as clothing, furniture,⁹ construction, electronics, automobile industry,¹⁰ pipes, cable insulation and packaging foils.¹¹ PVC has been extensively used for the fabrication of biomedical devices and employed in applications including urinary catheters, blood storage bags, and blood tubing in extracorporeal circuits.¹²

Utilizing metal nanoparticles (NPs) into polymeric matrices has been studied extensively to improve features and capacities such as mechanical, electrical, thermal and optical properties.¹³ For example, PVC/TiO₂ NCs were prepared by Mallakpour and et al. that found the presence of TiO₂ NPs can improve thermal, mechanical and optical properties of PVC.¹⁴ In another article, PVC/ZrO₂ NCs were prepared that showed more flexibility and thermal stability than pure PVC.¹⁵ Also, they prepared PVC NCs filled with modified SiO₂ NPs which showed more thermal stability and optical absorption than pure PVC.¹⁶

Such inorganic/organic system can be applicable in many fields, in particular in drug delivery, separation and purification of chemicals, development of shape-memory materials and in catalysis.¹⁷

Among the metal NPs, TiO₂ particles have attracted much attention due to their good photostability, nontoxicity, chemical and biological ineffective, antibacterial properties, UV-resistance and low cost.^18,19 TiO₂ NPs have been used for various applications including photocatalysis, catalytic supports, polymeric NCs, solar cells, sensors, transducer, and hydrogen generation etc.^20–22 Due to its compatibility with the environment, more researches are devoted to applications in implantation and drug delivery.²⁰ TiO₂ NPs can be straightly added to organic coating, but due to the high surface area and high polarity, there is a strong tendency to aggregate.²³ Aggregation occurs when particles are combined loosely. The aggregation prevents the obtaining of improved properties and the achieving of various applications by nanostructured materials. The strategies for avoiding aggregation are mainly attributed to particle coating by a capping agent, application of coupling agent and charging the filler surface to separate them via electrostatic revulsions. Also, using optimal parameters in the production process can lead to an efficient separation of aggregates.²⁴

Different organic or inorganic materials can be used as modifiers to surface modification of NPs.¹⁶ Particularly, organic compounds (e.g. natural organic matter NOM) modify the surface characteristics of NPs by changing surface charge and aggregation behavior.²⁵

Thiamin is a suitable modifying agent which can be employed for modification of the TiO₂ NPs. Thiamin also known as vitamin B₁ or aneurin was first isolated in 1926 from rice bran. Thiamin is one of the water-soluble vitamins, which is composed of pyrimidine and thiazole rings joined by a methylene bridge. Its degradation happens in alkaline solution and upon exposure to heat and light.^26,27 Thiamin was investigated as a ligand for modifying of NPs due to its environmental friendly, safe and cheap properties. Newly, this vitamin was proposed as a special ligand for the coating of NPs in order to target the blood–brain barrier and breast cancer cells.²⁸

Vitamin B₁ (VB₁) is biosafe and naturally synthesized molecule which have functional groups such as hydroxyl (OH) and amine (NH₂). As a result, several interactions can occur between the PVC matrix and coated TiO₂ NPs.

In this study, surface modification of TiO₂ NPs was performed using VB₁, for the first time. Then PVC NC films embedded with different amounts of modified TiO₂ NPs, were produced using ultrasonic irradiation process as a green and fast method. The produced materials were identified using Fourier transfer infrared (FT-IR), X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), thermogravimetric analysis (TGA), ultraviolet-visible (UV-Vis) spectroscopy, tensile testing and water contact angle measurements.

2. Experimental

2.1 Materials

Nanosized TiO₂ powder was supplied by Neutrino Co (Iran) with average particle sizes of <50 nm. Emulsion grade PVC (MW: 78 000 g mol⁻¹) and THF (MW: 72.11 g mol⁻¹) were obtained respectively from LG Chem (Korea) and JEONG Wang (Korea). VB₁ (MW: 300.81 g mol⁻¹) was purchased from the Alfa Aesar (Germany).

2.2 Instrumental analysis

FT-IR spectra of the samples were recorded at wavenumber range 400–4000 cm⁻¹ with Jasco-680 (Japan) spectrometer at 4 cm⁻¹ resolution by using pressed KBr pellets. TGA data were performed on a STA503 appliance (TA instrument) in an argon atmosphere at a rate of 20 °C min⁻¹. UV-Vis analysis was accomplished to investigate the optical properties of the NC films on UV-Vis-NIR spectrophotometer (JASCO, V-570), with solid film sample in the spectral range between 200 and 800 nm. Philips X’PERT MPD (Germany) diffractometer was employed to measurement the XRD patterns of the samples with a copper (Cu) target at 40 kV and 35 mA and Cu Kα incident beam (k1.51418 Å) in the range 5–100 at a rate of 0.05° min⁻¹. TEM images were obtained using Philips CM 120 (Netherlands) operated at 100 kV. The morphology of modified NPs powder and NC films was evaluated by FE-SEM (HITACHI S 4160, Japan). The reactions were carried out by TOPSONIC ultrasonic liquid processors (Iran, Tehran) with the frequency of 20 kHz and power of 400 W. Tensile testing was performed using a Testometric Universal Testing Machine M350/500 (UK) with the speed of 5 mm min⁻¹. Water contact angle measurements were performed by the sessile drop method. The image of the drop was captured using a digital camera microscope (U-VISION MV500, China).

2.3 Surface modification of TiO₂ NPs

In the first step, 0.20 g of TiO₂ NPs was dispersed in 8 ml of deionized (DI) water by ultrasonication for 15 min. Then 0.02 g of VB₁ was dissolved in 8 ml of DI water and was ultrasonicated for 15 min to achieve a homogenous solution. In the second step the VB₁ solution was added to the TiO₂ suspension and ultrasonicated for 30 min to grafting onto the NPs surface (Scheme 1).

Scheme 1 Surface modification of TiO₂ NPs with VB₁.

2.4 Preparation of PVC/TiO₂–VB₁ NCs

The preparation of PVC/TiO₂–VB₁ NC films were performed by ultrasonic irradiation technique. PVC (0.10 g) were dissolved in 5 ml THF and stirred for 1 h at 40 °C to achieve a homogenous solution. Modified TiO₂ NPs with different contents (3, 5, and 7 wt%) were added into the PVC solution. Then, the above mixtures were ultrasonicated for 30 min, and the resulting solutions were cast onto a glass Petri dish and kept at room temperature to prepare NC films.

The images of the prepared NC films with different contents of NPs are shown in Fig. 1. As it can be seen, the transparency of NC films decreased with increasing of the NPs contents.

Fig. 1 Visual transparency of (a) pure PVC, (b) PVC/TiO₂–VB₁ NC 3 wt%, (c) PVC/TiO₂–VB₁ NC 5 wt%, and (d) PVC/TiO₂–VB₁ NC 7 wt%.

3. Results and discussion

Surface modification of TiO₂ NPs with an appropriate modifying agent can decrease the aggregation of NPs. In this study, the surface of TiO₂ NPs was treated with VB₁ due to its special properties such as non-volatile, low-cost and non-corrosive using ultrasonication technique. Ultrasonic waves create more energy and cause a better connection of modifier on the surface of TiO₂. As shown in Scheme 1, coupling agent molecule (VB₁) can be adsorbed on the surface of NPs and can react with the OH groups on the surface of NPs. These interactions can prevent agglomeration of the NPs into the polymer. Surface modification with VB₁ leads to better dispersion of modified NPs into the PVC matrix.

3.1 FT-IR analysis

FT-IR is an efficient tool for investigating the structure of polymer composites. Due to the different components of the nanocomposite and the possible interactions between them can be expected to change in FT-IR spectra.²⁹ The FT-IR spectra of bare TiO₂, modified TiO₂ and VB₁ were investigated (Fig. 2). The wide peak in 450–1028 cm⁻¹ for the bare TiO₂ (Fig. 2b) is related to the stretching vibration of Ti–O–Ti, and the peaks at 3450 and 1630 cm⁻¹ can be ascribed to the surface hydroxyl groups of TiO₂ NPs.^30,31 The modified TiO₂ (Fig. 2c) shows new bands at 1350 and 1443 cm⁻¹ that are ascribed to C–H vibrations (–CH₃ of the pyrimidine ring) and C–H (in –CH₃). The band at 1662 cm⁻¹ is attributed to bending vibration of NH (NH₂).²⁷ The intensity of OH stretching in the modified TiO₂ is found to decrease, indicating an interaction of the hydroxyl group absorbed on TiO₂ surface with VB₁.

Fig. 2 The FT-IR spectra of (a) VB₁, (b) bare TiO₂, and (c) modified TiO₂.

The spectra of pure PVC and NCs (3, 5, and 7 wt%) shown in Fig. 3. As is clear from the FT-IR spectrum of the pure PVC (Fig. 3a), the peaks at 616 and 692 cm⁻¹ are ascribed to the stretching vibration of the C–Cl group. The peaks at 1097, 2911 and 2971 cm⁻¹ are related to the C–C, CH and CH₂ stretching vibrations.^32,33 PVC/TiO₂–VB₁ NCs (Fig. 3b–d), in addition to specific peaks of TiO₂ NPs at 450–800 cm⁻¹, show the characteristic absorption bands at 1532, 1550 and 1629 cm⁻¹ which are related to the stretching vibrations of the C=C and the C=N of the pyrimidine ring respectively.

Fig. 3 The FT-IR spectra of: (a) pure PVC, (b) PVC/TiO₂–VB₁ NC 3 wt%, (c) PVC/TiO₂–VB₁ NC 5 wt%, (d) PVC/TiO₂–VB₁ NC 7 wt%.

3.2 X-ray diffraction

Fig. 4 shows the XRD patterns of bare TiO₂ NPs, modified TiO₂ NPs, pure PVC and related NCs with different modified TiO₂ percentages. X-ray analysis of bare TiO₂ NPs showed seven diffraction peaks at 101, 004, 200, 105, 211, and 204 that are ascribed to the anatase phase, and also at 110, 220, and 301 are related to the rutile phase of TiO₂ NPs (Fig. 4a).^34,35 All the peaks of bare TiO₂ NPs were observed in modified TiO₂ NPs that indicating its crystallinity was not affected by the modification. The broad peak in the XRD curve of pure PVC indicated that the PVC is completely amorphous in nature (Fig. 4c).^7,36 The XRD of the NCs (Fig. 4d–f) show a monoclinic diffraction line which is related to the crystal plane (101) also the wide noncrystalline peak of the PVC. Therefore, it can be concluded that the morphology of TiO₂ was not altered during the sonication process.¹⁵ The obtained data from XRD analysis exhibit that the intensity of the peaks corresponds to the TiO₂ NPs content. With increasing the TiO₂ NPs content, the intensity of the peaks increased.

Fig. 4 XRD patterns of (a) pure TiO₂, (b) modified TiO₂, (c) pure PVC, (d) PVC/TiO₂–VB₁ NC 3 wt%, (e) PVC/TiO₂–VB₁ NC 5 wt% and (f) PVC/TiO₂–VB₁ NC 7 wt%.

3.3 Morphological observations

FE-SEM is an effective tool is used for studying the morphology of NCs. The morphology of the products was investigated using the FE-SEM analysis (Fig. 5). As shown in Fig. 5a and b modified TiO₂ NPs are in nanoscale with spherical-like morphology. The NPs are nearly same in diameter. The uniform morphology can be observed from FE-SEM images of NCs in 1 μm and 500 nm magnifications (Fig. 5c–h). These photographs indicated good dispersion of modified TiO₂ NPs throughout the PVC matrix.

Fig. 5 FE-SEM images of (a and b) TiO₂–VB₁, (c and d) PVC/TiO₂–VB₁ NC 3 wt%, (e and f) PVC/TiO₂–VB₁ NC 5 wt%, and (g and h) PVC/TiO₂–VB₁ NC 7 wt%.

The modified TiO₂ NPs and NCs were analyzed by TEM characterization. Fig. 6 and 7 show the TEM images and histograms of the modified TiO₂ NPs and PVC/TiO₂–VB₁ NC 7 wt% at different magnifications respectively. This is clear that modified TiO₂ NPs showed various shapes like spherical and cubical with diameters of 28–31 nm in the average size (Fig. 6). It can be seen from NCs images, which the TiO₂ particles are in the nano range and uniformly placed into the polymer matrix with the hydrogen bonds (Fig. 7).

Fig. 6 TEM micrographs of TiO₂–VB₁ and their histograms.

Fig. 7 TEM images of PVC/TiO₂–VB₁ NC 7 wt% along with their histograms.

3.4 Thermal analysis

The thermal stability of the polymer NCs is an important issue for use in practical applications. The thermograms of the TiO₂ NPs before and after modification are shown in Fig. 8. The bare TiO₂ showed a little weight loss of 3.5% within the whole temperature ranging 0–700 °C, which was ascribed to evaporation of the water absorbed by NPs.³⁷ It can be seen that the first degradation for modified TiO₂ occurred at 200–300 °C, also the other weight loss appeared within a narrow temperature range of 400–500 °C. Both these weight loss ascribed to the decomposition of VB₁ that grafted on the TiO₂ NPs.³⁷

Fig. 8 TGA plots of (a) pure TiO₂ and (b) TiO₂–VB₁.

Weight loss versus temperature for the pure PVC and related NCs shows in Fig. 9. The TGA thermograms of the pure PVC and PVC/TiO₂–VB₁ NCs undergo two step degradation processes. PVC has a highly tendency to degrade when exposed to heat, shear or radiation (such as UV-light) during melt-processing and practical applications. The degradation begins with a dehydrochlorination reaction and then is accelerated by the released hydrogen chloride (HCl).³⁸ The low stability of pure PVC can be attributed to the presence of structural defects such as head-to-head units, tertiary chlorines at branched carbons and chlorine atoms adjacent to internal double bonds. Heating PVC leads to its degradation and the emission of HCl and the formation of a polyene structure, which happened in the temperature range of 230–350 °C. The polyenes undergo secondary reactions such as scission and crosslinking, leading to the formation of aromatic compounds at the temperature range of 440–570 °C.^39,40 As it can be seen, the incorporation of NPs into the PVC matrix increased the thermal stability of all NCs.

Fig. 9 TGA plots of (a) pure PVC, (b) PVC/TiO₂–VB₁ NC 3 wt%, (c) PVC/TiO₂–VB₁ NC 5 wt%, and (d) PVC/TiO₂–VB₁ NC 7 wt%.

Table 1 shows (T₅) and (T₁₀) degradations temperature, percentage char yield (CY) at 800 °C, and limiting oxygen index (LOI) of the pure PVC and related NCs. As it is seen, when NPs were incorporated with the PVC matrix, the (T₅) and (T₁₀) degradations of all NCs increase and the NCs need more thermal energy for decomposition. In the case of NCs of 3 and 5 wt%, low concentration of nanoparticles and reducing the intermolecular forces after adding nanoparticles lead to more mobility the chains of PVC, therefore the char yield are reduced in comparison to pure PVC at these NCs. But at NC of 7 wt%, high concentration and uniformly dispersion of NPs and strong adhesion between the NPs and polymer matrix, causing the increasing the char yield compared to pure PVC. The char yield can be used for evaluation of limiting oxygen index (LOI) of a polymer in with Van Krevelen and Hoftyzer equation: LOI = 17.5 + 0.4 CY, where CY is the char yield. LOI is the minimum concentration of oxygen that will support combustion of a polymer. A polymer with high LOI has low flammability, so all NCs can be classified as a self-extinguishing materials.¹³

Table 1 Thermal stability of PVC and related NCs obtained from TGA thermograms

Samples	T5^a	T10^b	Char yield^c (%)	LOI^d
a Temperature at which 5% weight loss was recorded by TGA at a heating rate of 20 °C min^−1 under an argon atmosphere.b Temperature at which 10% weight loss was recorded by TGA at a heating rate of 20 °C min^−1 under an argon atmosphere.c Weight percentage of material left undecomposed after TGA analysis at a temperature of 800 °C under an argon atmosphere.d LOI evaluating char yield at 800 °C.
Pure PVC	240	255	23.3	26.8
PVC/TiO2–VB1 3 wt%	287	325	17.3	24.4
PVC/TiO2–VB1 5 wt%	296	329	20.2	25.6
PVC/TiO2–VB1 7 wt%	314	344	24.3	27.2

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3.5 Mechanical properties

Mechanical tests were performed to investigate the effect of NPs on the tensile properties of the pure PVC. Mechanical properties not only depend on shapes, orientations and distribution of fillers, but also depend on the interfacial adhesion between filler and matrix. Generally, nano-additives can improve the mechanical properties of the matrix materials and mechanical stability of NCs tends to increase with increasing values of them.¹² Fig. 10 shows the tensile stress–strain curves of the pure PVC and its related NCs. The values of various tensile parameters like Young's modulus, stress, strain and the elongation at break, extracted from all these curves, are listed in Table 2. The strain parameter increase with increasing NPs contents compared with the pure PVC and highest increase is related to the NC of 3 wt%. The stress parameter increases with increasing NPs loading; this can be explained by the reason that the incorporation of TiO₂ NPs into the PVC matrix effectively enhanced the interfacial interactions between NPs and matrix via the establishment of hydrogen and covalent bonds between them. As a result, the molecular chain strength of PVC is increased, that can influence the stress of NCs.³¹ As it can be seen, the Young's modulus, expressed in units of MPa, initially decreases at NC of 3 wt%, in the following increases with increasing NPs contents in both 5 and 7 wt%, but still are less than pure PVC. In general, it can be said that the NCs with large elongation and low modulus can show features of tough materials.¹⁴

Fig. 10 Tensile stress–strain curves of (a) pure PVC, (b) PVC/TiO₂–VB₁ NC 3 wt%, (c) PVC/TiO₂–VB₁ NC 5 wt%, and (d) PVC/TiO₂–VB₁ NC 7 wt%.

Table 2 Mechanical properties from tensile testing for pure PVC and PVC/TiO₂–VB₁ NCs

Sample	Stress (MPa)	Strain (%)	Young's modulus (MPa)	Elongation at break (mm)
Pure PVC	42	3	1973.4	0.9
PVC/TiO2–VB1 3 wt%	47	9	1267.1	4.3
PVC/TiO2–VB1 5 wt%	55	8	1702.9	3.6
PVC/TiO2–VB1 7 wt%	59	7	1864.6	3.3

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3.6 UV-Vis absorption

UV absorption has been used to characterize the TiO₂ NPs dispersed in polymer matrix. It is known that TiO₂ is an oxide semiconductor and its threshold of absorption is about 385 nm.²³ The absorption onset for modified TiO₂ NPs changed to around 650 nm that was reported as a red shift and can be assigned to the formation of a charge transfer complex between the surface of the TiO₂ NPs and VB₁.⁴¹

The UV-Vis absorption spectra of the pure PVC and related NC films are shown in Fig. 11. The absorbance peaks at λ = 234 and 280 nm are observed for pure PVC assigned to the n–π* and π–π* transition, respectively.^8,42 It is clear that the increase in TiO₂ NPs contents leads to increase absorption intensity in UV wavelength region. Increased light extinction by the addition of TiO₂ NPs into the polymer may be due to both nanofiller ultraviolet absorption and the light scattering.²³

Fig. 11 UV-Vis absorption spectra of (a) pure PVC, (b) PVC/TiO₂–VB₁ NC 3 wt%, (c) PVC/TiO₂–VB₁ NC 5 wt%, and (d) PVC/TiO₂–VB₁ NC 7 wt%.

3.7 Contact angle

The contact angle is a natural characterization of the wetting at a solid/liquid interface, straight determining the balance of forces at the three-phase contact line.⁴³ The concept of the contact angle and its equilibrium was important because it gave a definition to the notion of wettability. When θ ≠ 0°, mean that a liquid is nonspreading; and when θ = 0°, say that the liquid wets the solid completely and spreads loosely over the surface at a rate depending on the liquid viscosity and solid surface roughness. On a homogeneous solid surface, angle θ is independent of the volume of the liquid drop. Specifically, when the tendency of the liquid to spread increases as θ decreases, the contact angle is a useful inverse measure of spreadability or wettability.⁴⁴ The contact angle for pure PVC and the PVC films containing different TiO₂ contents are tabulated in Table 3. By increasing the amount of TiO₂, the contact angle of the NCs was slightly increased and by elapsing time, the contact angle of the films doesn't change. It is well-known that the water contact angle will increase with increasing surface hydrophobicity.³¹ The results indicate that increasing the content of TiO₂ NPs lead to prevent the spreading of the water drop over the film surface resulting in an increasing of the surface hydrophobicity.⁴⁵ Therefore, the water resistance of PVC/TiO₂–VB₁ NC films could be enhanced by adding the desirable amount of TiO₂ NPs.⁴⁶ Fig. 12 shows the images of water droplets on the pure PVC and related NCs.

Table 3 Contact angles of water droplets data for pure PVC and related NCs

Samples	Contact angle
Neat PVC	68 ± 0.79
PVC/TiO2–VB1 3 wt%	77 ± 0.73
PVC/TiO2–VB1 5 wt%	80 ± 0.81
PVC/TiO2–VB1 7 wt%	84 ± 0.83

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Fig. 12 Images of water droplets on (a) pure PVC, (b) PVC/TiO₂–VB₁ NC 3 wt%, (c) PVC/TiO₂–VB₁ NC 5 wt%, and (d) PVC/TiO₂–VB₁ NC 7 wt%.

4. Conclusions

The apparition of new peaks and also shifts in the FTIR spectrum of modified TiO₂ certified the presence of VB₁ on the surface of NPs. XRD patterns of NC films showed that the morphology of the TiO₂ NPs did not alter after incorporation in the PVC matrix and the intensity of the peaks increased with increasing the content of the TiO₂ NPs. It is clear from the TEM images of the PVC NCs that, TiO₂ NPs uniformly embedded into the polymer matrix. A comparison of T₅ and T₁₀ of the NCs with pure PVC showed an increase in thermal stability of PVC/TiO₂–VB₁ NCs. Also, strain and elongation of NC films were increased compared with the pure PVC. The lower hydrophilic properties of TiO₂ NPs caused the enhancement of surface hydrophobicity of PVC NCs in comparison with pure PVC. As a result, we can say that the presence of VB₁ as modifier agent can prevent agglomeration of TiO₂ NPs and impact on thermal, mechanical, and optical properties of PVC.

Acknowledgements

We wish to acknowledge the Research Affairs Division Isfahan University of Technology (IUT), Isfahan, for partial financial support. We are also indebted National Elite Foundation (NEF), Iran Nanotechnology Initiative Council (INIC) and Center of Excellence in Sensors and Green Chemistry Research (IUT) for further financial support.

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