Efficacy of phthalate plasticizers in p-PVC varies with change in the surrounding, causing failure of PVC components used in various applications. ATR-FTIR, evaluating the presence of carbonyl groups, is used for the structural analysis of p-PVC components before and after heat treatment of samples.
Introduction
PVC is the polymer primarily used to make pipes for plumbing, drainage, and electrical conduits. It is resilient, cheap, and simple to install. Even when still serviceable, PVC pipes degrade over time due to exposure to aggressive environmental factors, such as UV radiation, high temperatures, and chemical exposures. Its degradation may cause degradative effects in terms of a deteriorated chemical structure, mechanical properties, and performance of the PVC. FTIR Spectroscopy is one of the practical tools for ascertaining chemical changes in PVC pipes. FTIR provides detailed spectroscopy on material molecular structures and, thus, contributes toward quantification of degradation. It offers the opportunity to estimate the service life remaining in PVC pipes and ensure their reliability in different applications.
Scope
FTIR-based quantification of degradation in PVC pipes gives the chemical changes that occur in the polymer due to natural environmental stressors. The level of degradation can be estimated by the intensity of specific peaks or absorption bands found on the FTIR spectrum. Degradation in PVC usually results from forming new functional groups, such as carbonyl groups, and the breaking of original molecular bonds. FTIR thus offers a non-destructive technique of identifying and quantifying those changes with valuable information on the material’s performance. Hence, it is especially well-suited for examining the effects of UV, thermal aging, oxidative degradation, or chemical exposure, making it a very appropriate tool for tracing PVC pipe longevity and integrity.
Procedure:
- Sample Preparation: A PVC pipe sample is segmented into small pieces or thin films. Size and shape standardization of PVC samples are prepared to ensure accuracy in the FTIR analysis. Samples should be free from contaminants that can react with them during analysis. If such pipes need to be accelerated-aged, they would be exposed to UV radiation, heat, chemicals, etc., to simulate long-term environmental exposure.
- FTIR Analysis: FTIR spectrometers utilize infrared light passed through the sample and the polymer’s absorption of specific wavelengths. These absorption bands correspond to molecular vibrations, thus providing information on the material’s chemical composition. With PVC, one must look for peaks associated with C-H, C-Cl, and C=O vibrations. Shifts in these peaks or the emergence of new peaks indicate degradation. For example, oxidative degradation may result in the production of a carbonyl group.
- Quantitative Degradation: The change in absorbance of particular FTIR peaks may be measured to quantify the degree of PVC degradation. Oxidation degradation is indicated if a peak near 1700 cm⁻¹ related to carbonyl groups. The ratio of the carbonyl peak to another peak, like that of C-H stretching or C-Cl stretching, relates to estimating the degree of degradation. The level of degradation of aged samples can then be evaluated by comparing the FTIR spectra with those of virgin PVC samples.
Sample
The sample used in the FTIR-based quantification of PVC pipe degradation consists of PVC pipe sections exposed to UV radiation and thermal aging for a specified period. Small pieces of the aged pipes are prepared for FTIR analysis to assess the chemical changes due to degradation.
Result
FTIR analysis of the aged sample reveals a significant increase in the carbonyl absorption peak around 1700 cm⁻¹, indicating oxidative degradation. In addition, a decrease in the intensity of the C-Cl stretch proves a breakdown in the polymer’s chemical structure due to aging.
Applications of FTIR-Based Quantification of Degradation in PVC Pipes
The Applications of FTIR-Based Quantification of Degradation in PVC Pipes are as follows.
| Aspect | Description |
| Quality Control | FTIR helps assess the chemical integrity of PVC pipes during production, ensuring consistent quality of the final product. |
| Durability | It is a test to evaluate the long-term resistance properties of PVC pipes to UV, thermal, and mechanical stresses. |
| Material Selection | It helps select the proper PVC formulations by quantifying the degradation patterns in any given environment. |
| Failure Analysis and Forensic Studies | It helps to investigate pipe failures by identifying chemical changes due to aging or degradation. |
Conclusion
FTIR is an effective and non-destructive means of quantifying PVC pipe degradation. Changes in the FTIR spectrum can reveal the extent of chemical modification caused by environmental stressors such as UV radiation, heat, and chemicals. Such information could provide critical insights into the lifetime and performance of PVC pipes in real applications. The quantification of degradation through FTIR helps manufacturers and engineers ensure the reliability of PVC pipes and, consequently, make proper decisions regarding material selection, maintenance, and replacement in this industry.
