Lena’s crates passed every test her team ran at room temperature. Then a customer stacked a pallet of them in a freezer at minus 25 degrees Celsius for a week, and nearly half came back with cracked corners. The resin was polypropylene. It was also thirteen percent cheaper per kilogram than the polyethylene it had replaced.
On paper, the swap looked like an upgrade. PP is stiffer, tolerates more heat, and cost less on the day the order was placed.
What the quotation didn’t say is that polypropylene’s glass transition sits near 0 °C. A freezer isn’t a colder version of a warehouse. It’s a different material regime.
That is the trap this guide exists to close. Polyethylene vs polypropylene is the most common cross-material decision in commodity plastics. In pe vs pp pellets terms, the two resins are genuinely interchangeable for maybe half of all applications. The other half is where the money is lost, usually after the scrap has been counted.
You’ll get four things here. The property differences that actually drive the decision. The process windows and melt flow index ranges for both resins. A verdict on when one can substitute for the other, and the exact specification to put on your next purchase order. If you’re sourcing polyethylene pellets in bulk, read this before you approve the quotation.
Polyethylene vs Polypropylene: The Short Answer
PE and PP are both polyolefins and both ship as pellets. What separates them is a single methyl group on the propylene monomer, which stiffens the chain and lifts the glass transition temperature from deep-negative to near zero. That one difference sets stiffness, heat resistance and cold behavior in a causal chain.
- Choose PE when the part must survive impact, especially in the cold, or needs the best moisture barrier. PE stays ductile down to roughly minus 40 °C and resists water vapor better than any other commodity resin. Crates, bottles, pipe, film, caps and closures.
- Choose PP when the part must be stiff, hold shape at temperature, or flex millions of times. PP carries a much higher melting point and heat deflection temperature, and it’s the industry standard for living hinges. Containers, caps with hinges, automotive trim, medical devices, appliance parts.
- Choose PP over PE when the service environment includes detergents, greases or repeated flexing. PP is far less prone to environmental stress cracking, which is PE’s signature weakness.
- Choose PE over PP when the service environment drops below freezing, or when an oxidizing acid is involved. This is the reverse of the usual assumption, and it catches people out.
Here is the same decision as a table.
| If your requirement is… | Order | Because |
|---|---|---|
| Stiffness and dimensional stability | PP | Flexural modulus of 1,000–2,000 MPa against 200–1,200 for PE |
| Heat resistance and higher service temperature | PP | Melting point 160–170 °C and HDT around 90–105 °C, well above PE |
| Impact toughness at low temperature | PE | Ductile to roughly minus 40 °C; PP embrittles near 0 °C |
| A living hinge or a flexing part | PP | Over one million flex cycles; PE fatigue-cracks after a few thousand |
| Resistance to detergents, greases and stress cracking | PP | Virtually free of the true environmental stress cracking that plagues PE |
| Best moisture vapor barrier | PE | Dense chain packing, the best of the two resins |
| Resistance to oxidizing acids | PE | PP’s tertiary carbon makes it vulnerable to nitric and chromic acid |
| Lighter parts from the same volume | PP | Lower density, 0.895–0.920 g/cm³ against 0.910–0.976 for PE |
| Food contact with hot fill or sterilisation | PP | Beats PE on autoclave, retort and microwave service |
| Cold chain, frozen storage, winter outdoor use | PE | The failure mode Lena hit is a PP failure mode |
In short: PP is the stiff, heat-resistant, fatigue-proof resin that will crack in a freezer. PE is the tough, low-temperature, barrier resin that will sag, soften and stress-crack in hot chemical service. Every pp vs pe plastic decision reduces to those two sentences.
If you already know which resin family you need, our material team can map your application to a density and MFI window and confirm it against a real datasheet. Send us your specification and we’ll confirm the resin before you commit to a tonnage.
Polyethylene vs Polypropylene: Property Comparison
The numbers below are the ones that change a purchasing decision. Every value carries its test method, because a tensile figure without a method is not a specification.
Read as a polypropylene vs polyethylene comparison, the table splits cleanly. PP owns the thermal and stiffness rows. PE owns the toughness and barrier rows. It follows the method-first format of our HDPE compared with POM breakdown.
| Property | Polyethylene (PE) | Polypropylene (PP) | Test method |
|---|---|---|---|
| Density (g/cm³) | 0.910–0.976 (LDPE 0.910–0.940; HDPE 0.941–0.976) | 0.895–0.920 (homopolymer ~0.900–0.908) | ASTM D792 / ISO 1183 |
| Crystallinity (%) | 35–85 (LDPE 40–60; HDPE 65–85) | 40–70 (homopolymer ~50–70) | DSC |
| Melting point (°C) | 105–135 (LDPE 105–115; HDPE 125–135) | 160–170 homopolymer; 140–155 random copolymer | ASTM D3418 |
| Glass transition, Tg (°C) | About minus 120 to minus 90 | About minus 10 to 0 | DMA / DSC |
| Heat deflection temperature (°C) | Typically below 80 | 90–105 | ASTM D648 / ISO 75 |
| Vicat softening point (°C) | 120–130 (HDPE) | 150–155 | ASTM D1525 / ISO 306 |
| Continuous service temperature (°C) | Roughly 80–100 | Roughly 100–120 | Supplier guidance |
| Flexural modulus (MPa) | 200–1,200 | 1,000–2,000 | ISO 178 |
| Tensile strength at yield (MPa) | 8.2–45 (HDPE 17–45) | 20–40 | ISO 527 |
| Elongation at break (%) | 100–1,000 | 100–600 | ISO 527 |
| Notched impact strength | Moderate to high, retains toughness when cold | Low at room temperature, falls 60–70% below the brittle transition | ISO 180 |
| ESCR (stress-crack resistance) | Poor; notably prone in surfactants and detergents | Excellent; virtually free of true ESC | ASTM D1693 |
| Moisture vapor barrier | Best of the two | Weaker than PE | ASTM E96 |
| Grease and oil barrier | Weaker than PP | Better than PE | ASTM D722 |
| Fatigue and flex life | Fails after a few thousand flex cycles | Over one million flex cycles | Flexural fatigue test |
| UV and oxidation resistance | More forgiving; needs UV stabiliser outdoors | More oxidation-prone because of the tertiary carbon; needs antioxidant plus UV package | Accelerated weathering |
| Mold shrinkage (%) | 1.5–5.0 (HDPE highest, and directional) | 1.0–2.5 | ASTM D955 |
| Resin identification code | #2 for HDPE; #4 for LDPE and LLDPE | #5 | Resin identification standard |
A warning before you read too much into the precision. This is one of the most source-contested comparisons in commodity plastics. Published UV guidance contradicts itself outright, with some references rating both resins “poor” and others claiming PP is the more stable.
Tensile ranges for the two resins overlap almost completely, so “is polypropylene stronger than polyethylene” has no clean answer at the material level. It only has an answer at the grade level.
The ranges above reflect the majority of producer datasheets. Where your own datasheet disagrees, the datasheet wins.
Why One Methyl Group Changes Everything
Polyethylene is built from ethylene, a two-carbon unit with nothing hanging off it. Polypropylene is built from propylene, the same backbone with a methyl group attached. That methyl group is the whole story.
It stiffens the chain, because a methyl group is bulkier than hydrogen and restricts rotation around the backbone. It also raises the glass transition temperature from about minus 100 °C to near 0 °C, and it places a tertiary carbon at every repeat unit. That tertiary carbon is easy to oxidize, which is why PP needs antioxidant and UV packages that PE can live without.
In practical terms: stiffness, heat resistance and fatigue life all rise with PP. Low-temperature toughness and oxidative stability fall. Every row in the table above traces back to that one difference. For the polymer chemistry behind it, SpecialChem’s PE vs PP guide is the most reliable free reference available.
Polyethylene vs Polypropylene: Density, Crystallinity and Stiffness
PP is the lighter resin. Homopolymer PP sits at 0.900 to 0.908 g/cm³, PE spans 0.910 to 0.976, so a PP part is measurably lighter than the same part in PE. On a per-kilogram basis that advantage disappears, because you need less mass to fill the same mold. Cost per part beats cost per kilogram every time here. Picking the right sub-type inside that PE range is a separate decision, covered in HDPE vs LDPE vs LLDPE.
Stiffness is the bigger gap. PP’s flexural modulus runs 1,000 to 2,000 MPa against 200 to 1,200 for PE. A PP part holds its shape under load where a PE part would flex. That is why crates, pallets, caps and appliance housings default to PP, and why PE is reserved for parts that need to bend, seal or absorb impact.
PE vs PP Heat Resistance: Melting Point, HDT and Service Temperature
On polypropylene vs polyethylene heat resistance, this is PP’s clearest win. Homopolymer PP melts at 160 to 170 °C against 125 to 135 for HDPE and 105 to 115 for LDPE. Its heat deflection temperature of 90 to 105 °C sits well above PE’s typical sub-80 figure.
The consequence is service temperature. A PP part can run continuously in the region of 100 to 120 °C, while a PE part is comfortable nearer 80 to 100 °C.
That gap decides hot-fill packaging, dishwasher parts, under-hood components and anything that gets steamed or sterilised. If the part sees heat, PP is usually the only commodity answer.
Low-Temperature Impact and the Brittle Transition
Here is where the freezer got Lena’s crates. PP’s glass transition sits near 0 °C, and below that point its amorphous regions lock up. Notched impact strength can fall 60 to 70% once a PP part drops below its brittle transition. A crate that shrugged off a drop test in a warm warehouse will shatter in a cold one.
PE has no such problem, because its Tg sits at roughly minus 90 to minus 120 °C, far below any realistic service condition. PE stays ductile to about minus 40 °C, which is why frozen-food packaging, cold-storage bins and winter outdoor parts default to PE.
If PP is mandatory for its stiffness but the part will see cold, the fixes are an impact copolymer or an impact modifier such as a polyolefin elastomer. Expect to trade away some modulus and add cost per kilogram.
PE vs PP Chemical Resistance and Stress Cracking
The polyethylene vs polypropylene chemical-resistance question carries the most widely repeated error in the category. The common claim is that PP is simply “more chemical resistant.” The accurate answer depends on the chemical.
PP resists solvents, greases and stress cracking better than PE. PE resists oxidizing acids better than PP, because PP’s tertiary carbon is vulnerable to hydrogen peroxide, nitric acid and chromic acid. Both resins are poor against aromatic and chlorinated hydrocarbons such as benzene and carbon tetrachloride, and both get worse as temperature rises.
The environmental stress cracking split matters more than most buyers realize. Environmental stress cracking is the slow failure of a stressed plastic under contact with a chemical, and it is a well-documented PE weakness, particularly in surfactants and detergents. LyondellBasell’s technical note on polypropylene chemical resistance describes PP as effectively free of true ESC, with bleach causing an ESC-like failure through oxidation rather than genuine stress cracking.
That single fact explains a failure mode that looks like bad material and is really a bad material choice. Ravi ran a detergent bottling line and moved a bottle from PP to PE to cut cost. Three months later, handles began cracking in the warehouse under stack load, with no chemical leak anywhere near them. The surfactant inside was doing the work.
Fatigue and Living Hinges
PP has no rival among commodity resins for flexing parts. Fold a PP hinge and the molecular chains align along the fold, which lets the same hinge flex over a million cycles without failure. PE can be molded into a hinge shape, but its chains do not align the same way, and the hinge whitens and fatigue-cracks after only a few thousand cycles.
This is why every flip-top cap, clamshell and one-piece hinged container you have handled is PP. Tomas learned it from the other direction. He tooled a hinged lid in PE to save roughly eleven percent on resin and lost the customer at the third production run, when the hinges snapped in the field. The saving on pellets could not cover the cost of the tooling rework and the lost account.
PE vs PP Melt Flow and Shrinkage: Which Resin for Which Process?
Melt flow index is the number that actually travels with an order, and it’s the number most polyethylene vs polypropylene comparisons leave out. There is a subtlety here that trips up even experienced buyers: PP and PE are measured on different scales.
PP melt flow is measured at 230 °C with a 2.16 kg weight. PE is measured at 190 °C with 2.16 kg, or at 190 °C with 21.6 kg for the high-load index used on blow-molding and pipe grades. A PP at 20 g/10 min and a PE at 20 g/10 min are not equivalent materials. Always quote the test condition alongside the number. On the PE side, polyethylene pellet types and grades lists the melt flow window for each family.
| Process | PP melt flow (230 °C / 2.16 kg) | PE melt flow (190 °C / 2.16 kg) |
|---|---|---|
| Injection molding, general purpose | 5–40 | 5–20 (HDPE) |
| Thin-wall injection | 20–40 | 20–30 (HDPE) |
| Blow molding | 1–3, rarely used | 0.2–0.5 (HDPE, or HLMI 190/21.6) |
| Extrusion and pipe | 0.3–2 (PP-R pipe) | ≤0.4 (HDPE pipe) |
| Film, cast or blown | 2–4 | 0.04–0.10 (HDPE film); about 1 (LLDPE) |
| Fibre and spunbond | 10–35 | Not a PE process |
| Rotational molding | Not a PP process | 2–5 (LLDPE) |
Shrinkage is the other process variable that decides whether a swap is a re-set or a disaster. PE shrinks 1.5 to 5.0% and does so directionally, while PP shrinks 1.0 to 2.5% and more evenly. If you move a mold from PE to PP, the tool will over-pack unless you compensate, and vice versa. For the injection-molding side of this in detail, HDPE injection molding covers gate design, cycle time and warp.
PE vs PP Substitution: Can You Swap One for Another?
This is the question that costs money, and it’s the one almost nobody answers directly. Whether a polyethylene vs polypropylene substitution works depends on the process and the environment, not just the material. The matrix below gives the verdict per route.
| Process or service | Substitution | Verdict | Why |
|---|---|---|---|
| Injection molding, general | PE → PP | Workable with re-validation | Higher stiffness and lower shrinkage, but re-check cold impact and cycle time |
| Injection molding, general | PP → PE | Workable with re-validation | Softer and tougher when cold, but lower stiffness, lower HDT and more shrinkage |
| Cold chain or frozen storage | PE → PP | Do not attempt | PP embrittles near 0 °C; impact strength can fall 60–70% |
| Living hinge | PE → PP | Drop-in, and an upgrade | PP is the hinge material; this direction is the fix, not the problem |
| Living hinge | PP → PE | Do not attempt | PE whitens and fatigue-cracks after a few thousand cycles |
| Hot fill, retort or microwave | PE → PP | Drop-in, with re-validation | PP is the higher-temperature resin; re-check closure and seal design |
| Hot fill, retort or microwave | PP → PE | Do not attempt | PE service temperature is too low |
| Detergent or surfactant container | PP → PE | Do not attempt | PE is notably prone to environmental stress cracking in surfactants |
| Detergent or surfactant container | PE → PP | Workable with re-validation | PP shrugs off ESC; re-check stiffness and low-temperature impact |
| Blown film | PE → PP | Do not attempt | PP does not run on PE blown-film lines; BOPP and cast film are different processes |
| Blow molding a bottle | PE → PP | Do not attempt | PP lacks the melt strength for extrusion blow molding; use PP injection-stretch-blow grades |
Three rules sit underneath that table.
First, what always has to be re-validated. Shrinkage, cycle time, weld-line strength and ESCR under the actual chemical load, plus cold-drop performance if the part ships or stores cold. A substitution can pass every datasheet comparison and still fail on one of those five.
Second, PE and PP do not blend. They are generally immiscible, and a straight mixture will deliver worse properties than either resin alone. Making a useful blend requires a compatibiliser, typically a maleic-anhydride grafted polyolefin. Mixing regrind across the two families without one is how a good part turns into a brittle one.
Third, they can’t be separated by density. Both resins float, so the sink-float tanks used in most recycling lines can’t tell them apart. Separating mixed PE and PP needs a tuned density medium or a selective dissolution step. That is why most post-consumer mixed polyolefin ends up downcycled rather than reprocessed into a like-for-like resin. Keep the two streams apart at your own plant and the problem never reaches a sorting line.
Ready to test a substitution on real grade documentation? Send us the current grade and the target application, and we’ll tell you whether the swap is workable before you commit a mold. Request a technical review →
Polyethylene vs Polypropylene Food Contact and Sterilisation
Both resins are food-safe in virgin grades. The governing references are FDA 21 CFR 177.1520 for olefin polymers, which covers PE and PP together, plus EU 10/2011 and EC 1935/2004 in Europe, and GB 4806.7-2023 in China.
The difference is in the service condition, not the compliance. PP is the hot-fill, microwave, retort and autoclave material. Its higher melting point and softening temperature let it take steam sterilisation, ethylene oxide and gamma irradiation, which is why pharmaceutical vials, syringe barrels and reusable medical trays default to PP. PE is the cold-chain material. It suits chilled and frozen storage, where its toughness matters more than its heat ceiling.
Get this backwards and the failure is quiet at first. A PE container used for hot fill will soften, distort and lose seal integrity, and it will do so gradually rather than at the first fill. We cover the temperature boundary in detail in is LDPE microwave safe, and the practical rule is simple: if the part sees boiling water or a microwave, specify PP.
Polyethylene vs Polypropylene Cost per Part
Price is the last tie-breaker in a polyethylene vs polypropylene decision, never the first, and the ordering between the two resins isn’t stable.
FOB China data for the second half of 2026 puts general-purpose PP at roughly 0.85 to 1.05 USD/kg against PE at 0.90 to 1.10. That makes PE look like the more expensive resin. But by 1 July 2026, domestic Chinese pricing had flipped, with PE near 6,916 RMB per tonne against PP at 7,274. Week-of-16-April 2026 FOB figures put PP T30S at 1.204 USD/kg, PP HP550N at 1.214, and LLDPE 7042 at 1.204, essentially level across the three.
The honest answer to “which is cheaper” is that it depends on the grade, the region and the quarter. What doesn’t move is the arithmetic that matters: PP’s lower density means more parts per tonne, and PP’s lower shrinkage means less material consumed per part. A resin that costs more per kilogram can cost less per part.
Our full 2026 breakdown lives in the polyethylene pellets price guide. Use the figures above as a direction, and price your own decision per part.
Turning the Decision into a Specification
A PE vs PP resin choice becomes a purchase only when it is written down. Nine lines turn “we need pellets for a container” into an order a supplier can quote against in one pass:
- Resin: polyethylene or polypropylene
- Sub-type: PE as HDPE, LDPE or LLDPE; PP as homopolymer, random copolymer or impact copolymer
- Density, with tolerance
- MFI, with the test condition stated, for example 2.16 kg at 230 °C for PP
- Additive package: antioxidant, UV, antistatic, nucleating agent or flame retardant
- Virgin or recycled, and the recycled percentage if applicable
- Certification required: FDA, EU 10/2011, GB 4806.7-2023, USP Class VI or a food-contact letter
- Form and packaging: pellet or powder, 25 kg bags, jumbo bags or bulk
- Quantity, Incoterms and delivery point
Then add the one clause that prevents most disputes: per-lot density and MFI on the certificate of analysis. A resin name on a quotation is not a specification, and a grade code without a datasheet behind it is an assumption.
For the two commercial ranges that cover these specifications, our HDPE plastic pellets and PP plastic pellets pages document density and MFI per lot. Note also that the industry uses “granules” and “pellets” interchangeably for the same product; the terms are covered in granules and pellets.
Polyethylene and Polypropylene Pellets from Suzhou Yifuhui
Suzhou Yifuhui New Material Co., Ltd. supplies both commodity polyolefin families with per-lot documentation rather than a resin name on an invoice. Because we stock PP alongside PE, we have no reason to push you toward one of them.
What ships with the material:
- Verified grade documentation. Our published Moplen HP500N polypropylene datasheet and Taisox 9001 HDPE datasheet are available for review before you order, so you can confirm a grade meets your density and MFI window first.
- Lot-traceable COAs carrying density and MFI for the specific lot you receive, not a generic technical data sheet.
- 21 CFR 177.1520 documentation on the grades that hold food-contact compliance, plus sterilisation-grade PP for medical and pharmaceutical applications.
- Technical response within 24 hours on resin selection, including low-temperature impact assessment when a PP part has to run cold.
- Global shipping on 25 kg bags, jumbo bags and bulk, with the Incoterms that suit your plant.
Our PP range includes Moplen HP500N, Yuplene R370Y, Hanwha Total HJ730, Sanren M800E, Tairipro K4650 and Borealis BJ368MO, and our PE range covers HDPE, LDPE and LLDPE in standard injection, film, blow-molding and pipe grades. If you send us your application, your current grade code and your target density and MFI, we’ll confirm whether the resin you have in mind is the right one before you place a tonnage. If it isn’t, we’ll say so.
Frequently Asked Questions
What is the difference between polyethylene and polypropylene?
The difference is one methyl group. Polypropylene is polyethylene’s backbone with a methyl group attached to each repeat unit. That group stiffens the chain and raises the glass transition temperature from about minus 100 °C to near 0 °C. The result: PP is stiffer, handles more heat and survives millions of flex cycles, while PE is tougher in the cold and has the better moisture barrier.
Which is stronger, PE or PP?
At the material level, neither wins a PE vs PP strength contest cleanly. PP is stiffer, with a flexural modulus of 1,000 to 2,000 MPa against 200 to 1,200 for PE. PE is tougher under impact, especially when cold. PP also resists environmental stress cracking far better, which is often the more expensive failure. The answer depends on whether the load is static and structural or dynamic and impact-based.
When should I use polypropylene instead of polyethylene?
Use PP when the part needs stiffness, holds shape at temperature, flexes repeatedly, or contacts detergents and greases. Living hinges, hot-fill containers, dishwasher parts, medical devices and appliance housings are all PP applications. Use PE instead when the part sees freezing temperatures, needs the best moisture barrier, or contacts an oxidizing acid.
Why does polypropylene crack in the cold?
Because its glass transition temperature sits near 0 °C. Below that point, PP’s amorphous regions lock up and notched impact strength can fall 60 to 70%. A PP part that survives a room-temperature drop test can shatter in a freezer. If PP is required for its stiffness in a cold application, specify an impact copolymer or add a polyolefin elastomer and accept some loss of modulus.
Can polypropylene replace polyethylene?
Sometimes. In injection molding, a PE-to-PP swap is workable with re-validation of shrinkage, cycle time and cold impact. Moving a part from PE to PP for a hot-fill or living-hinge application is a genuine upgrade. But swapping PP into a cold-chain part, or PE into a surfactant container, should not be attempted. Always re-validate shrinkage, cycle time, weld-line strength, ESCR and cold-drop performance.
Is PE or PP better for a living hinge?
PP, without comparison. Its chains align along the fold, letting the hinge flex over one million cycles. PE can be molded into a hinge shape but whitens and fatigue-cracks after only a few thousand cycles. Every flip-top cap and clamshell on the market is PP for this reason.
Is polyethylene or polypropylene more chemically resistant?
It depends on the chemical, and the usual answer is half wrong. PP resists solvents, greases and environmental stress cracking better. PE resists oxidizing acids such as nitric and chromic acid better, because PP’s tertiary carbon oxidizes readily. Both are poor against aromatic and chlorinated hydrocarbons, and both perform worse at higher temperatures.
Which is cheaper, polyethylene or polypropylene?
There’s no permanent answer. Second-half 2026 FOB China data put PP slightly below PE, but by 1 July 2026 domestic Chinese pricing had PP above PE. The ordering is grade-, region- and quarter-dependent. Because PP is lower in density and shrinks less, it often wins on cost per part even when it loses on cost per kilogram.
Can polyethylene and polypropylene be recycled together?
No, not usefully. The two resins are immiscible, so a straight blend delivers worse properties than either alone and needs a compatibiliser to be worth anything. They also both float, so sink-float separation cannot tell them apart. Keep the two streams separate, because separating mixed PE and PP requires a tuned density medium or selective dissolution.
Are polyethylene and polypropylene food safe?
Yes, in virgin grades. Both are covered by FDA 21 CFR 177.1520 for olefin polymers, plus EU 10/2011 and GB 4806.7-2023. The practical split is service temperature: PP handles hot fill, microwave, retort and sterilisation, while PE suits chilled and frozen storage. For food-contact recycled material, a Letter of No Objection is required.
Conclusion
Polyethylene and polypropylene are not two grades of one material. They are two materials that share a pellet form and a price bracket, and they fail in opposite directions.
- PP wins on stiffness, heat resistance, fatigue life, grease barrier and stress-crack resistance. It is the right answer whenever the part holds shape, sees heat, flexes repeatedly, or contacts detergents.
- PE wins on low-temperature impact, moisture barrier and oxidizing-acid resistance. It is the right answer whenever the part runs cold, must absorb impact, or holds water vapor out.
- The freezer is the dividing line. PP embrittles near 0 °C; PE stays ductile toward minus 40 °C. Check the minimum service temperature before you check the price.
- Substitution is process-specific. Re-validate shrinkage, cycle time, weld-line strength, ESCR and cold-drop performance every time.
- Specify with density and MFI plus its test condition, and remember that PP and PE melt flow numbers are measured on different scales. Ask for both figures on the COA of every lot.
If you are weighing polyethylene vs polypropylene for a specific part, send us the application, the minimum service temperature and your current grade code. We’ll confirm the resin against real grade documentation rather than a datasheet summary, and tell you which one to avoid.
