The goal of this study is to find the effect of time and temperature on the thermal degradation of recycled polyvinyl chloride (PVC) resin. The isothermal rate of reaction
Polyvinyl chloride (PVC) is one of the most commonly used thermoplastic materials with respect to the worldwide polymer consumption. At present, demand for PVC exceeds 35 million tons annually, and it is rated second only after polyethylene in consumption by volume. Currently, PVC is applied in a variety of products including packaging, medical devices, food, and also long-life applications such as pipes, window frames, cable insulation, floors coverings, and roofing sheets [
Previously, studies conducted on the thermal stability of the polyvinyl chloride showed that the stability of PVC resin mixed with organic tin and hydrotalcite was better than that of the PVC resin mixed with organic Tin alone [
Moreover, activation energy for the degradation of series of solution-cast blends of polyvinyl chloride/epoxidised liquid natural rubber (ELNR) was studied and the results were 73, 41, 73, and 77.25 KJ/mol for 100/0, 70/30, 50/50, and 30/70 PVC/ELNR-20, respectively, where activation energy of 30/70 PVC/LNR was 35 kJ/mol [
Also, other techniques of PVC degradation like photocatalysis [
The goal of this study is to know how the PVC resin is affected by different temperatures (100–140°C) and at different periods of time (10, 20, 30, 40, and 50 min). So we know how the PVC resin bears the temperature from 100 to 140°C with and without problems of it being damaged in the recycling process. To know the mechanism of the degradation reaction, the order of reaction, the rate of reaction constant, and the activation energy were calculated at different temperatures (100–140°C) and at different periods of time (10, 20, 30, 40, and 50 min).
Recycled polyvinyl chloride (PVC) was supplied from Hose Jeihoon Plast Company in Iran.
The following is the procedure to degrade the recycled polyvinyl chloride with temperatures and times.
It was weighted of empty crucible (ceramic crucible) and crucible with recycled PVC, where the state of the recycled PVC samples was a sheet with the dimensions: 1 cm in length, 1 cm in width, and 0.2 cm in thickness. Therefore, the initial weight can be determined by the following law:
After that the crucible with recycled PVC samples was put in the furnace under atmospheric air to the required heating time and temperature. When degradation was completed, the recycled PVC sample was removed from the furnace and cooled to estimate the weight loss of the recycled PVC.
The above procedure was repeated for every degrading sample of recycled PVC in each temperature and time.
The kinetics of thermal degradation of PVC resin was studied at various temperatures (100–140°C) and during various times (10–50 min). The reaction rate of recycled PVC was experimentally determined using the relation [
The rate of reaction (g/min) of PVC resin at different times (min) and at different temperatures (100–140°C).
Time (min) | Rate of reaction (g/min) | ||||
---|---|---|---|---|---|
At curing |
At curing |
At curing |
At curing |
At curing |
|
10 | 0.01784 | 0.02522 | 0.05377 | 0.0617 | 0.0803 |
20 | 0.028795 | 0.03975 | 0.04404 | 0.049285 | 0.05095 |
30 | 0.02371 | 0.029233 | 0.035667 | 0.038073 | 0.0401 |
40 | 0.0275 | 0.029175 | 0.032135 | 0.0366 | 0.040153 |
50 | 0.031422 | 0.03282 | 0.035626 | 0.0395 | 0.043858 |
To calculate the order of reaction
Plotting
The
The rate of the reaction equations at different temperatures (100–140°C) was obtained from Figure
The order of reaction of thermal degradation of recycled PVC resin was between 0.2421th and −0.539th, as shown in (
Plotting according to the equation of 1st, 2nd, and zero order reaction.
It is also known that zero order reaction means that the thermal degradation does not depend on initial amount of polymer [
Rate of reaction constant ln(
Temperature (°C) |
|
Reaction rate constant, ln( |
---|---|---|
100 | 0.00268 | −3.5738 |
110 | 0.00261 | −3.4506 |
120 | 0.002544 | −3.2183 |
130 | 0.00248 | −3.0603 |
140 | 0.00242 | −2.8772 |
The
The activation energy of recycled PVC resin degradation was obtained from the slope of straight line in Figure
To calculate the average enthalpy change
The transition state equation [
When rearranging (
From taking the
The slope of the straight line of (
ln(
|
ln( |
||||
---|---|---|---|---|---|
Time = 10 min | Time = 20 min | Time = 30 min | Time = 40 min | Time = 50 min | |
0.00268 | −9.94825 | −9.46949 | −9.6638 | −9.51551 | −9.38219 |
0.00261 | −9.62852 | −9.17355 | −9.48085 | −9.48285 | −9.36512 |
0.002544 | −8.89706 | −9.09667 | −9.30756 | −9.41183 | −9.3087 |
0.00248 | −8.78497 | −9.00963 | −9.26774 | −9.3072 | −9.23095 |
0.00242 | −8.54597 | −9.0009 | −9.24037 | −9.23906 | −9.15079 |
As we show from Figure
Therefore, from (
The study of recycled PVC degradation kinetics revealed that the rate of reaction increased with increasing temperatures. Additionally, the rate constant
The author declares that there is no conflict of interests.