{"id":1059,"date":"2026-07-11T14:22:37","date_gmt":"2026-07-11T06:22:37","guid":{"rendered":"https:\/\/bastone-petrochem.com\/?p=1059"},"modified":"2026-10-15T11:46:10","modified_gmt":"2026-10-15T03:46:10","slug":"polyethylene-vs-polypropylene","status":"publish","type":"post","link":"https:\/\/bastone-petrochem.com\/ru\/polyethylene-vs-polypropylene\/","title":{"rendered":"\u041f\u043e\u043b\u0438\u044d\u0442\u0438\u043b\u0435\u043d \u043f\u0440\u043e\u0442\u0438\u0432 \u041f\u043e\u043b\u0438\u043f\u0440\u043e\u043f\u0438\u043b\u0435\u043d\u0430: \u0420\u0443\u043a\u043e\u0432\u043e\u0434\u0441\u0442\u0432\u043e \u043f\u043e \u0443\u0440\u043e\u0432\u043d\u044f\u043c \u043c\u0430\u0440\u043e\u043a \u0434\u043b\u044f \u043f\u0435\u0440\u0435\u0440\u0430\u0431\u043e\u0442\u0447\u0438\u043a\u0430"},"content":{"rendered":"

Both polyethylene and polypropylene land in your warehouse as off-white pellets with a density near 0.91 and a single MFI on the COA. The pellets tell you almost nothing about which one belongs in your part.
2. A converter choosing between the two isn\u2019t really picking a material family. The choice is decided by the part\u2019s single most demanding requirement \u2014 service temperature, low-temperature impact, stiffness, clarity, or chemical contact. Each requirement points to a specific sub-grade and MFI band, not just \u201cPE\u201d or \u201cPP.\u201d
3. How Polyethylene and Polypropylene Differ on the Spec Sheet
4. Polypropylene runs stiffer and hotter; polyethylene runs tougher and colder. PP holds a melt point of 165-175 \u00b0C against PE\u2019s 105-130 \u00b0C, carries a higher flexural modulus, and resists solvents and stress cracking better. PE answers back with impact toughness that survives to roughly -80 \u00b0C, where PP homopolymer turns brittle near 0 \u00b0C.
5. That family-level verdict is accurate, and it resolves nothing for a real part. The spread inside each family is wide enough to swallow the difference between them.
6. Property (ASTM)
7. Polypropylene
8. Polyethylene
9. Density, D792
10. Melt point
11. 165-175 \u00b0C
12. 105-130 \u00b0C
13. Flexural modulus, D790
14. 13,000-25,000 psi (90-170 MPa)
15. 29,000-174,000 psi (200-1,200 MPa), LDPE\u2192HDPE
16. Notched Izod, D256
17. 21-747 J\/m (homo\u2192impact)
18. LDPE no-break, HDPE 1.3 ft-lb\/in
19. Brittleness onset
20. ~0 \u00b0C (homopolymer)
21. to ~-80 \u00b0C (HDPE)
22. ESCR
23. excellent
24. poor (LDPE) to excellent (HDPE)
25. Read the impact row before anything else. PP\u2019s notched Izod runs from a brittle 21 J\/m homopolymer to a 747 J\/m impact copolymer \u2014 a 35-fold internal range that overlaps deep into PE territory.
26. The family name is a starting point. The sub-grade is the answer.
27. How the PP and PE Sub-Grades Differ
28. Each family fans out across a property range that the family label hides, and the sub-grade choice often decides the part more than the PE-versus-PP line does. Three PP grades and three PE grades carry the real decision variables.
29. On the PP side, the divider is ethylene comonomer content:
30. \u2014 maximum stiffness and the highest melt point, but a glass transition near 0 \u00b0C makes it brittle in the cold. This is monofilament, woven-bag tape, and rigid injection work. A homopolymer monofilament grade like PetroChina T30S sits here.
31. \u2014 trades some stiffness for clarity, heat-sealability, and a lower melt point. This is the PP-R hot-and-cold water pipe grade; PetroChina Dushanzi T4401 is the typical reference, with Sinopec equivalents in a similar MFI band.
32. \u2014 the rubber phase keeps it tough at low temperature. Freezer parts, automotive, and cold-service injection live here.
33. On the PE side, the divider is density and chain branching:
34. LDPE (0.910-0.940)
35. \u2014 heavily branched, soft, flexible, poor stress-crack resistance. Film, bags, liners.
36. LLDPE (0.915-0.940)
37. \u2014 a linear backbone with short branches delivers better tear and puncture resistance plus good ESCR at the same density. Stretch and agricultural film. A grade like LL0209AA outperforms LDPE on puncture despite the overlapping density.
38. HDPE (0.941-0.970)
39. \u2014 tightly packed, stiffest PE, excellent stress-crack resistance. Its flexural modulus of 174,000 psi is roughly six times LDPE\u2019s 29,000 psi and rivals PP. Pressure pipe (PE100, such as TUB121N3000) and blow molding.
40. The within-family numbers prove the point. HDPE is six times stiffer than LDPE, and impact copolymer PP carries up to ten times the notched impact of homopolymer. Treating LLDPE and LDPE as interchangeable because both are low-density is the single most common selection error here, and it costs film converters real puncture failures.
41. Choosing Polyethylene or Polypropylene by the Part\u2019s Governing Requirement
42. Start with the part\u2019s single most demanding requirement and let it pick the sub-grade. One requirement governs; the rest are constraints you check afterward.
43. Service temperature
44. \u2014 for hot-fill, steam, or hot-water duty, PP wins outright: homopolymer for the highest heat-deflection temperature, or random copolymer for PP-R pipe. PE\u2019s maximum operating temperature tops out near 71 \u00b0C (LDPE) to 82 \u00b0C (HDPE), so it\u2019s off the table for anything hot.
45. Low-temperature impact
46. Stiffness and rigidity
47. \u2014 HDPE or PP homopolymer, both far above LDPE\u2019s 29,000 psi flexural modulus. If the part also has to take cold impact, that conflict is exactly why impact copolymer exists.
48. \u2014 random copolymer PP is the clearest option in this set. HDPE reads translucent-to-milky, so it loses on any see-through part.
49. Chemical contact
50. \u2014 PP carries broad solvent resistance and very high stress-crack resistance; industry estimates put its ESCR roughly 20-100\u00d7 that of HDPE. That suits PP to aggressive solvent and acid contact, while HDPE earns pipe duty only because PE100 grades are bimodal-engineered specifically to raise ESCR.
51. The processing method then sets the MFI band \u2014 high MFI to fill thin-wall injection and blow molds, low MFI for pipe and extrusion. One trap on the COA: a PP MFI is measured at 230 \u00b0C\/2.16 kg and a PE MFI at 190 \u00b0C\/2.16 kg, so the two numbers are not directly comparable across families.
52. Read the test condition, not just the number. MFI alone also won\u2019t tell you whether a grade draws clean \u2014 you need the molecular-weight distribution behind it. Once the family and sub-grade are set, the PP grade-pick narrows further across
53. homopolymer, random, and impact options
54. Telling PE from PP at Incoming Inspection.<\/p>\n\n\n\n

A converter choosing between the two isn\u2019t really picking a material family. The choice is decided by the part\u2019s single most demanding requirement \u2014 service temperature, low-temperature impact, stiffness, clarity, or chemical contact. Each requirement points to a specific sub-grade and MFI band, not just \u201cPE\u201d or \u201cPP.\u201d
How Polyethylene and Polypropylene Differ on the Spec Sheet
Polypropylene runs stiffer and hotter; polyethylene runs tougher and colder. PP holds a melt point of 165-175 \u00b0C against PE\u2019s 105-130 \u00b0C, carries a higher flexural modulus, and resists solvents and stress cracking better. PE answers back with impact toughness that survives to roughly -80 \u00b0C, where PP homopolymer turns brittle near 0 \u00b0C.
That family-level verdict is accurate, and it resolves nothing for a real part. The spread inside each family is wide enough to swallow the difference between them.
Property (ASTM)
Polypropylene
Polyethylene
Density, D792
Melt point
165-175 \u00b0C
105-130 \u00b0C
Flexural modulus, D790
13,000-25,000 psi (90-170 MPa)
29,000-174,000 psi (200-1,200 MPa), LDPE\u2192HDPE
Notched Izod, D256
21-747 J\/m (homo\u2192impact)
LDPE no-break, HDPE 1.3 ft-lb\/in
Brittleness onset
~0 \u00b0C (homopolymer)
to ~-80 \u00b0C (HDPE)
ESCR
excellent
poor (LDPE) to excellent (HDPE)
Read the impact row before anything else. PP\u2019s notched Izod runs from a brittle 21 J\/m homopolymer to a 747 J\/m impact copolymer \u2014 a 35-fold internal range that overlaps deep into PE territory.
The family name is a starting point. The sub-grade is the answer.
How the PP and PE Sub-Grades Differ
Each family fans out across a property range that the family label hides, and the sub-grade choice often decides the part more than the PE-versus-PP line does. Three PP grades and three PE grades carry the real decision variables.
On the PP side, the divider is ethylene comonomer content:\u201d<\/p>\n\n\n\n

How Polyethylene and Polypropylene Differ on the Spec Sheet<\/h2>\n\n\n\n

Polypropylene runs stiffer and hotter; polyethylene runs tougher and colder. PP holds a melt point of 165-175 \u00b0C against PE\u2019s 105-130 \u00b0C, carries a higher flexural modulus, and resists solvents and stress cracking better. PE answers back with impact toughness that survives to roughly -80 \u00b0C, where PP homopolymer turns brittle near 0 \u00b0C.<\/p>\n\n\n\n

That family-level verdict is accurate, and it resolves nothing for a real part. The spread inside each family is wide enough to swallow the difference between them.<\/p>\n\n\n\n

Property (ASTM)<\/th>Polypropylene<\/th>Polyethylene<\/th><\/tr><\/thead>
Density, D792<\/td>0.89-0.91<\/td>0.91-0.97<\/td><\/tr>
Melt point<\/td>165-175 \u00b0C<\/td>105-130 \u00b0C<\/td><\/tr>
Flexural modulus, D790<\/td>13,000-25,000 psi (90-170 MPa)<\/td>29,000-174,000 psi (200-1,200 MPa), LDPE\u2192HDPE<\/td><\/tr>
Notched Izod, D256<\/td>21-747 J\/m (homo\u2192impact)<\/td>LDPE no-break, HDPE 1.3 ft-lb\/in<\/td><\/tr>
Brittleness onset<\/td>~0 \u00b0C (homopolymer)<\/td>to ~-80 \u00b0C (HDPE)<\/td><\/tr>
ESCR<\/td>excellent<\/td>poor (LDPE) to excellent (HDPE)<\/td><\/tr><\/tbody><\/table><\/figure>\n\n\n\n

Read the impact row before anything else. PP\u2019s notched Izod runs from a brittle 21 J\/m homopolymer to a 747 J\/m impact copolymer \u2014 a 35-fold internal range that overlaps deep into PE territory.<\/p>\n\n\n\n

The family name is a starting point. The sub-grade is the answer.<\/p>\n\n\n\n

How the PP and PE Sub-Grades Differ<\/h2>\n\n\n\n

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On the PP side, the divider is ethylene comonomer content:<\/p>\n\n\n\n