PP vs. HDPE
HDPE Material
Polyethylene is a kind of thermoplastic polymers, which means that it turns into liquid by reaching its melting point and turns into solid by reaching its freezing point. Polyethylene is a chemical synthesis of ethylene, usually made up of a mixture of crude oil and natural gas. Polyethylene is widely used in the production of all kinds of plastic accessories used in the kitchen and food industries. LDPE is used in the manufacture of light plastic containers as well as plastic bags. LDPE is used in the manufacture of taps and liquid containers and all kinds of plastic kitchen appliances. MDPE is commonly used in the production of plastic pipes and plumbing fittings.
Advantages of polyethylene
• Galvanic corrosion resistance
• Resistance to decay, abrasion and impact
• Proper flexibility
• Collapsibility
• Light Weight
• Excellent resistance to earthquakes and landslides
• Highly connectible, leak-proof, and flexible
• High resistance to ultraviolet rays of the sun
• Having very good hydraulic characteristics
• Low maintenance cost
Polypropylene - PP - Types and specifications
polypropylene is a polymer with a variety of applications and is used to make fibers, films, household appliances and even car bumpers.
Advantages of polypropylene:
• Lighter polymer with low density
• High melting point
• The final application temperatures are around 212 F
• Good chemical resistance against hydrocarbons, alcohols and non-oxidizing reagents. • Good fatigue strength.
Disadvantages and limitations of polypropylene:
• Destroys through UV.
• Flammable, but its commercial types are available.
• It is attacked by chlorinated solvents and aromatics.
• It is difficult to link.
• Several metals accelerate oxidative degradation.
Types of Polypropylene Applications:
• Packaging: Flexible packaging films, packaging films that are oriented bi-axially.
• Fabric: directed single-strand stitched, special ribbon for textiles, carpet weavers, isolated medical fabrics and woven carpet back covers.
• Personal and medical care: health precautions, household goods and medical trays, colanders, kitchen sieves and hollow dishes.
• Consumable goods: caps, upper caps, sprays, rigid and semi-rigid packaging, toys, electrical hardware, home appliances and their constituent parts, outfit and outdoors appliances in open air and luggage.
Comparison of plastics in the pipe industry
In the world, four major types of plastics are currently being used in the cold and hot drinking water piping industry. EN12202 (ISO 15874 and EN 12108) have introduced the names of these plastics as follows:
|
PP-H ٬ PP-B ٬ PP-R |
Triple polypropylene types |
|
CPVC |
chlorinated soft PVC |
|
PB |
Polybutylene |
|
Pex |
(PEX) lattice polyethylene |
Table 22 - Plastics introduced in EN12202, EN12108 standards
In the following tables presented, the physical and resistance features of these plastics have been studied and compared
It should be noted that the comparison of the lifetime of these plastics in the pipe industry was first carried out by Aria Kavan Qeshm Company and its standard reference is also stipulated. Of course, in some cases it refers to the DIN standard, and some also refer to the ISO standard, which in most cases are similar to each other and comparison of the results of their experiments is possible.
In addition, on the following pages, two comparisons conducted by Harington and Main Industries have been shown that they do not mention all the four major types of plastics in the water plumbing industry; it seems that the properties of the main polymer are intended and the properties of pipes made from polymer have not been investigated.
Comparison of the life and resistance of the plastic pipes against temperature according to global standards
|
Temperature per centigrade continuously throughout the day and night |
|
Standard |
Name of pipe polymer |
20 |
40 |
50 |
60 |
70 |
80 |
90 |
95 |
|
ISO 12230 |
PB |
Mpa 13/6
50 years |
Mpa 11/5
50 years |
Mpa 10/3
50 years |
Mpa 9
50 years |
Mpa 7/6
50 years |
Mpa 6/1
50 years |
Mpa 4/7
25 years |
Mpa 4
15 years |
DIN 16892
DIN16893 |
PEX |
Mpa 9/5
50 years |
Mpa 7/8
50 years |
Mpa 7
50 years |
Mpa 6
50 years |
Mpa 5/4
50 years |
Mpa 4/6
25 years |
Mpa 4/2
15 years |
Mpa 4
10 years |
|
DIN 8080 |
CPVC |
Mpa 26
50 years |
Mpa 18
50 years |
Mpa 14
50 years |
Mpa 11
50 years |
Mpa 8/5
50 years |
Mpa 6/5
5 years |
Mpa 4/8
4 years |
Mpa 4/2
1 years |
|
ISO 3213 |
PP-R |
Mpa 9/7
50 years |
Mpa 6/9
50 years |
Mpa 5/8
50 years |
Mpa 4/8
50 years |
Mpa 3/2
50 years |
Mpa 2/4
25 years |
Mpa 1/8
15 years |
Mpa 1/6
10 years |
|
ISO 3213 |
PP-B |
Mpa 8/7
50 years |
Mpa 5/8
50 years |
Mpa 3/8
50 years |
Mpa 2/6
50 years |
Mpa 1/8
50 years |
Mpa 1/5
25 years |
Mpa 1/2
15 years |
Mpa 1/2
10 years |
|
ISO 3213 |
PP-H |
Mpa 10
50 years |
Mpa 7
50 years |
Mpa 5/8
50 years |
Mpa 4/7
50 years |
Mpa 3
50 years |
Mpa 2/3
25 years |
Mpa 1/8
15 years |
Mpa 1/6
10 years |
|
ISO/TR9080 |
PE |
Mpa 6/2
50 years |
Mpa 3/5
25 years |
- |
Mpa 1/8
10 years |
- |
Mpa 1/3
1 years |
(0) |
(0) |
|
DIN 8075 |
HDPE |
Mpa 8/2
50 years |
Mpa 3/5
50 years |
Mpa 3/2
12 years |
Mpa 2/3
10 years |
Mpa 2/8
5 years |
Mpa 2/2
2 years |
Mpa 1/7
5 years |
(0) |
(0) |
DIN 8062
ISO 4422 |
PVC
UPVC |
Mpa 6
50 years |
Mpa 2/5
50 years |
Mpa 2/5
30 years |
Mpa 1/5
30 years |
(0) |
(0) |
(0) |
(0) |
Table 23 - Comparative assessment of life span of some polymers based on related standards
Physical and functional disadvantages of some plastics compared to AK pipes
1. PB is expensive and turns into hose by decrease in the thickness and will be crushed against the pressure of soil and materials.
2. PEX is expensive and its joints are non-weldable (PEX thermoand cannot be recycled nor welded).
3. CPVC has a life span of 15 years at 70 ° C for and only 5 years at 80 ° C.
4. PE and HDPE have a life span of 10 years at 60 ° C.
5. PVC tolerates a maximum temperature of 60 ° C with less than 1/5 atmospheres with a maximum thickness of 4.3 mm and a diameter of 20 mm that cannot be produced. The PVC is practically not produced at nominal pressures greater than 10 atmospheres, but it is also referred to as its 16 and 25 atmosphere types in the aforementioned standard.
6. PP-B is weaker than PP-R and PP-H in terms of resistance to heat. (It is more resistant to impact and lower temperatures.)
7. Most pipes in the country and in the world, which are manufactured with thin-walled pipes with polymer stuff, are bonded to each other by compressive, screw thread or adhesive, so these connections are much weaker than PP welded joints. It should be noted that all the above polymers, except for PP, have non-welded joints due to reasons such as expensiveness or impossibility of producing high thickness, and O-rings or washers are used in them; the lifetime of O-ring and washer is significantly lower than the original polymer. They are particularly damaged in the hot water system and produce leakage.
Table 24 - Comparison of properties of some plastics adopted from Harington
Physical and functional advantages of PP compared with other plastics according to Harington
1. PP is the lightest. (Here, PP is a type one homopolymer polypropylene)
2. PP has less water absorption than PVC and CPVC.
3. PP has a tensile strength modulus more than PE, HDPE and PEX.
4. PP has an elasticity greater than PE and HDPE.
5. PP has a flexural strength equal to HDPE and more than PEX.
6. PP has an isodized impact resistance of 30 ° more than PVC and less than the rest.
7. PP has a higher compressive resistance than HDPE and PEX.
8- This table can be extracted from the Internet by naming Harington.
Table 25. Comparison of the properties of some polymers based on Main Industries Institute information
Comparison of properties of some polymers based on Main Industries Institute information
1. The specific gravity of PP is less than the rest.
2. Tensile strength of PP is higher than HDPE and PB.
3. The modulus of elasticity of PP is higher than HDPE and PB.
4. PVC and CPVC are sensitive to impact and PP are somewhat sensitive but HDPE and PB are resistant to impact and are not sensitive.
