Feb 26, 2010 - (butadiene + naphthenic oil), Poly (butadiene acrylonitrile), which were determined from FTIR result, might have resulted in such swelling effect.
The Third International Conference on Structure, Processing and Properties of Materials, SPPM2010 24-26 February 2010, Dhaka, Bangladesh, SPPM2010 E17
Characterization of uPVC Pipes M.M. Billah, A.A. Sharif, T. Rahman, R. Qadir, U. K. Sultana and Q. Ahsan Department of Materials and Metallurgical Engineering, Bangladesh University of Engineering and Technology, Dhaka-1000, Bangladesh Abstract Fillers are used in uPVC pipes to increase the initial strength. But it decreases the long-term strength as their concentration increases. Determination of filler content is essential for characterization and improvement of uPVC pipes. In this study relative amount of filler content in uPVC pipe was determined using thermogravimetric analysis (TGA). Effect of filler content on the mechanical properties of uPVC pipes were also studied. In order to assess the quality of uPVC pipe FTIR, DSC, TGA etc. tests were also performed. It was clearly observed that the improvement in mechanical strength and other physical properties of uPVC pipes are obtained by the controlled addition of filler. Keywords: Filler, characterization, thermogravimetric analysis, tensile properties
1. INTRODUCTION Unplasticized Poly Vinyl Chloride, commonly known as uPVC, is a polymer of Vinyl Chloride. It has a linear structure. uPVC is widely used throughout the world for making plumbing pipes. The constituents of uPVC pipes include filler materials, stabilizers, plasticizers, impact modifiers, lubricants, processing aids etc. Among these constituents, filler content varies over a wide range in commercial production as well as the quality of the product. Excess filler content decreases the long-term strength of the product. So, controlled addition of filler content is essential to assure the quality of the product. The amounts of moisture, volatile materials, unexpected organic constituents are determinant factors of product quality and service performance. Excess moisture and volatile material content often lead to pipe failure by blistering and delamination. Unexpected organic compounds may have malicious effect on mechanical properties. This work involved determination of relative amount of filler content in uPVC. Presence of moisture and volatile materials was investigated. Different mechanical properties i.e. tensile properties, impact properties were determined. Effects of filler content, presence of moisture and volatile materials on mechanical properties were investigated. Service performances i.e. water absorption and extent of swelling were also observed.
2. EXPERIMENTAL PROCEDURE Uniform mechanical properties particularly strength is dependent on uniform diameter and thickness of the pipes. Thickness variation was measured using digital slide calipers. Apart from this, length and periphery were also determined. For acetone test, samples of 100 mm were taken. Acetone for laboratory use was taken in a beaker, and the samples were immersed to 25 mm in the acetone. They were kept there for 2 hours before taking out and observing whether there was any delamination, disintegration or swelling. Samples of known weight were taken for water absorption, hot water and steam test. For water absorption test, the samples were kept in water for 96 hours. Samples were weighed at the end of that period to find out whether any water was absorbed or not. Swelling effect was also observed in regular intervals. For hot water test the samples were kept in the hot water of 90°C for 100 minutes. Similarly weighing was done after the test period together with swelling observation .For steam test, steam was produced in steam chamber and the samples were exposed to steam for 45 minutes. After the exposure, surface condition was observed and weight gain was determined.
Fourier Transformed Infrared Spectroscopy (FTIR) was done with powdered samples. FTIR results were analyzed to find out the constituents with their amount as percentage of the total weight. Powdered samples were also used for Differential Scanning Calorimetry (DSC) and Thermo Gravimetric Analysis (TGA). DSC was carried out to determine the presence of moisture and other volatile materials. Melting point and any decomposition were also determined by observing exothermic and endothermic peaks. Relative amount of filler content was determined from TGA result. Tensile properties were measured by carrying out the tensile test of specific geometry with Universal Testing Machine (UTM). In Hydrostatic test, for every pipe sample an assembly was made into which hydrostatic pressure was applied and pressure was measured from the gauge in 5 seconds intervals up to failure. Impact energy was applied to all the samples by means of a metallic mandrel. For Drop Impact test the size of the mandrel were varied depending on the diameter of the pipes. The results gave an idea about the relative impact strength of the samples. Finally Heat Reversion test was done to find out the presence of moisture and volatile materials.
3. RESULTS AND DISCUSSION Thickness was observed which varied along the length and periphery over several millimeter range (Figure 1).
Figure 1. Wall thickness variation of uPVC pipes
In water absorption test, acetone test, hot water test and steam test few samples were observed to gain weight and swelling was observed in acetone test (Figure 2). Presence of Aromatic hydrocarbon resin, Poly (butadiene + naphthenic oil), Poly (butadiene acrylonitrile), which were determined from FTIR result, might have resulted in such swelling effect. FTIR result showed the constituents to vary over a wide range of percentages (Table 1). Main constituent (Poly Vinyl chloride) was found to vary over a wide range of percentage (22.50-51.32). Unexpected elements were also found to be present. These variations also caused variations in different physical and mechanical properties.
Table 1. Ingredient compounds of uPVC
Figure 2. Swelling effect 0
Several endotherms in DSC around 100 C indicated presence of water and volatile compounds. Their presence was also revealed in Heat Reversion test in which blistering (Figure 3) and delamination (Figure 4) were observed.
Figure 3. Blistering effect
Figure 4. delamination
Residue percentage in TGA was found to increase with the increase in dehydrochlorination temperature and to decrease with decrease in dehydrochlorination temperature (Figure 5). It is known that dehydrochlorination temperature increases with increased filler content. So, residue percentage in TGA (Table 2) indicated the relative amount of filler content. Tensile properties were found to deteriorate with increasing filler content and so was the impact strength. Deteriorating effect of filler content on tensile strength was clearly visible (figure 6). In Hydrostatic test, maximum permissible pressure was found to decrease with increasing filler content (Figure 7). Pipes with higher filler content were found to fail in impact test and they also collapsed in Heat Reversion test (Table 2). Table 2. Filler contents and related mechanical properties Sample no
%wt residue (filler content)
Dehydrochlorination temp (OC)
Tensile Strength (Mpa)
Drop Impact test
Collapse in heat reversion test
Blistering Effect
1
62
292.02
18.18
failed
Yes
Less
2
44
279.87
26.60
failed
Yes
Less
3
67
298.10
15.86
failed
Yes
Severe
4
64
281.14
26.52
failed
Yes
Severe
5
30
282.91
35.83
Ok(4/42)
No
No
6
47
285.94
19.68
failed
Yes
Severe
7
63
290.50
15.73
failed
Yes
Severe
8
67
298.86
15.16
failed
Yes
Less
9
54
285.94
21.78
failed
Yes
Severe
10
41
282.70
27.36
OK(0/10)
No
No
11
41
281.40
29.71
OK(0/10)
No
No
Figure 5. Relationship between filler content and dehydrochlorination temperature
Figure 6. Relationship between filler content and tensile strength
Figure 7. Relationship between filler content and hydrostatic pressure
TGA curves (Figure 8) show how dehydrochlorination temperature shifts to higher temperature with increasing weight residual i.e. filler content. From DSC curves (Figure 9) several endothermic peaks were found. Endothermic peaks were found in the range of 90-110OC for volatile constituents. In addition to these peaks O some samples showed endothermic peaks at around 60 C. Blistering effect was severe in these samples O which had endothermic peaks at both around 60 C and 100OC. . Table 3. TGA data 2nd Peak Temp 0 ( C) 447.77
Weight loss st 1 Peak, %
Weight loss 2nd Peak, %
1
1 Peak Temp 0 ( C) 292.02
25
38
2 3 4 5 6 7 8 9 10 11
279.87 298.10 281.14 182.91 285.94 290.50 298.86 285.94 282.70 281.40
447.77 439.42 447.19 440.94 450.81 439.42 438.66 449.29 443.97 445.49
35 20 33 45 34 32 20 32 37 37
56 33 36 70 53 37 33 46 59 59
Sample
st
Table 4. DSC data
Sample
1st Peak Temp (0C)
2nd Peak Temp (0C)
3rd Peak Temp (0C)
4th Peak Temp (0C)
Nature of 1st Peak
Nature of 2nd Peak
Nature of 3rd Peak
Nature of 4th Peak
1
‐
91.42
109.55
251.67
‐
endo
endo
exo
2
‐
90.16
108.77
259.35
‐
endo
endo
exo
3
60.98
90.16
107.50
273.73
endo
endo
endo
exo
4
59.29
88.89
107.93
262.74
endo
endo
endo
exo
5
‐
90.98
115.96
261.89
‐
endo
endo
exo
6
61.40
86.78
110.46
266.97
endo
endo
endo
exo
7
33.06
87.80
128.65
258.08
endo
endo
endo
exo
8
‐
76.20
105.39
287.69
‐
endo
endo
exo
9
58.44
90.59
110.46
276.46
endo
endo
endo
exo
10
‐
59.29
109.62
244.55
‐
endo
endo
exo
11
‐
90.45
110.04
264.00
‐
endo
endo
Exo
Figure 8. TGA Curve
Figure 9. DSC Curve
4. CONCLUSION It is clearly observed that the improvement in mechanical strength and other physical properties of uPVC pipes are obtained by the controlled addition of filler. During processing presence of moisture and volatile compounds must be kept as low as possible. To assure the quality, ingredients must be avoided which were unexpectedly found in FTIR results.
