Polystyrene and Polyvinyl Chloride Blends Study

Abstract

This study investigates the morphological and thermal properties of polystyrene and polyvinyl chloride blends (PS/PVC). The PS and PVC are mixed using a solution casting method with cyclohexanone at various weight ratios (100/0, 80/20, 50/50, 20/80, and 0/100). The mixture formation is confirmed through Fourier Transform Infrared (FT-IR), Thermal Gravimetric Analysis (TGA), and Differential Scanning Calorimetry (DSC). The FT-IR results reveal no molecular reactions in the PS/PVC blends. TGA is employed to assess the thermal stability, revealing two glass transition temperatures for each mixture.

DSC results support the immiscibility of the blend. The distribution of phases in the virgin and blends is examined through Scanning Electron Microscopy (SEM).

Keywords

• PS/PVC blends
• TGA
• Immiscible
• Polymer blends
• Morphology

Introduction

Thermoplastic materials, commonly referred to as plastics, are widely used worldwide due to their mechanical strength, durability, processability, and chemical resistance. Among these, polystyrene (PS) and polyvinyl chloride (PVC) stand out as versatile plastics. PS offers high modulus and tensile strength but is prone to brittleness.

Get quality help now

Doctor Jennifer

Verified writer

Proficient in: Chemistry

5 (893)

“ Thank you so much for accepting my assignment the night before it was due. I look forward to working with you moving forward ”

+84 relevant experts are online

Hire writer

PVC, on the other hand, is flexible, chemically resistant, and economically valuable.

Polymer blending is a valuable approach for creating materials with unique properties that combine the strengths of individual polymers. This study focuses on PS/PVC blends, investigating their properties through FTIR spectroscopy, SEM, and DSC. Additionally, the thermal stability of these blends is assessed via TGA.

Importance of Polymer Blending

Polymer blending holds significance in both technical and academic domains due to its potential to enhance material properties through compositional variations. Understanding the behavior of polymer matrices is essential for various applications.

Materials and Methods

Materials

The materials used include:

• Polystyrene (PS) with a molar mass of 104.15 g/mol and a solubility parameter of 15.6-21.1 MPa.
• Polyvinyl chloride (PVC) in powder form with a porous structure, K value of 67-72, and a degree of polymerization ranging from 1250 to 1450.
• Cyclohexanone as the solvent.

Preparation of PS/PVC Blend

PS/PVC blends are prepared by dissolving PS and PVC in cyclohexanone at room temperature, followed by stirring for 2 hours at 25°C. The resulting solutions are cast onto glass plates, and cyclohexanone is allowed to evaporate slowly under ambient conditions. Blends are prepared at different weight concentrations: 100/0, 80/20, 50/50, 20/80, and 0/100.

Characterization

Scanning Electron Microscopy (SEM)

The morphology of the composites is analyzed using a Quanta FEG 250 SEM microscope operating at 5-10 kV. A thin gold coating (10-200 µm) is applied to the films to improve SEM micrographs.

Infrared Spectroscopic Analysis (FT-IR)

Infrared spectroscopic measurements are conducted using a FT-IR instrument (JASCO FT/IR-4100) in the spectral range of 4000-400 cm^-1.

Thermal Analysis

Thermal analysis is performed using a SDTQ 600 thermal analysis calorimeter from TA Instruments, capable of simultaneously conducting thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC) under an inert atmosphere (nitrogen) within a temperature range of 50-700°C with a heating rate of 10°C/min.

Results and Discussion

Scanning Electron Microscopy

The SEM micrographs reveal distinct phases in the PS/PVC blend, with small spherical particles of minority PVC phase dispersed within the PS matrix. As the PVC content increases, these particles tend to merge. Large globular particles indicate the distribution of PS in the PVC matrix.

FT-IR Spectroscopic Analysis

The FT-IR spectra in the range of 400-4000 cm^-1 for PS/PVC blends show specific vibrational bands related to CHCl and CH₂ in PVC, as well as aromatic C-H stretching vibrations in PS. The absence of significant changes in PVC's frequency zone upon adding PS suggests limited interaction between the components, confirming immiscibility.

Thermal Analysis

TGA results indicate that the initial decomposition temperature (Td) varies with blend composition. PS/PVC (80:20) has a higher Td (225°C) compared to PS/PVC (50:50) (141°C). An increase in PS content improves thermal stability. Additionally, an increase in PVC content enhances weight loss at high temperatures (700°C). DTG curves reveal two distinct decomposition temperature peaks for PS/PVC blends.

Differential Scanning Calorimetry Analysis (DSC)

The DSC analysis reveals that PS and PVC in the blend have independent glass transition temperatures (Tg). PS exhibits a Tg of 100.2°C, while PVC has a Tg of 76.7°C. The presence of two Tg values in the PS/PVC blend confirms immiscibility between the two polymers.

Conclusions

In this study, PS/PVC blends were prepared using solvent casting, and their properties were characterized through SEM, FT-IR, TGA, and DSC. The results indicate negligible intermolecular interactions, confirming immiscibility. Polymer blending enhances thermal stability, particularly with increased PS content. SEM observations support good morphology in the samples. These findings contribute to a deeper understanding of PS/PVC blend properties and their potential applications.