PP homopolymer vs copolymer is the first decision in almost every polypropylene part. Homopolymer is made from propylene alone and is the stiffest, most heat-resistant and cheapest type. Copolymers add ethylene, either scattered along the chain (random copolymer) or as a separate rubber phase (impact or block copolymer), to gain clarity or toughness. As a formulation development partner, SYCHEM TECH supplies all three types and the additives that tune them.
Short answer: choose homopolymer (PPH) for stiffness, heat resistance and lowest cost: raffia, BOPP film, fiber and rigid houseware. Choose random copolymer (PPR) for clarity and for hot and cold water pipe. Choose impact or block copolymer (PPB, PPIC) when the part must survive drops and cold: automotive parts, battery cases, crates and pails.
The three types of polypropylene
All polypropylene starts as chains of propylene. In homopolymer every unit is propylene, so the chains pack into a highly regular, 60–70% crystalline structure. That gives the highest stiffness and heat resistance, but the material is brittle below about 0 °C.
In random copolymer about 1–6% ethylene is built into the chain at random. The ethylene units break up the crystals, which lowers stiffness and melting point but makes the material clearer and more flexible, with good long-term pressure resistance for pipe.
Impact copolymer, often called block copolymer, is made in two reactor stages: a homopolymer matrix, then an ethylene-propylene rubber that forms small particles inside it. The rubber absorbs impact, so the part stays tough down to about −30 °C, while the matrix keeps most of the stiffness and heat resistance.
PP homopolymer vs copolymer comparison table
| Property | Homopolymer (PPH) | Random copolymer (PPR) | Impact / block copolymer (PPB, PPIC) |
|---|---|---|---|
| Comonomer | None | About 1–6% ethylene, random | Ethylene blocks or an ethylene-propylene rubber phase |
| Crystallinity | 60–70% | 30–50% | 45–60% |
| Tensile strength | 30–40 MPa | 20–30 MPa | 20–35 MPa |
| Stiffness (flexural modulus) | Highest | Lowest | Medium |
| Notched Izod at 23 °C | 2–5 kJ/m² | 3–6 kJ/m² | 6–15 kJ/m² (PPB) up to 20–60 kJ/m² (PPIC) |
| Low-temperature impact | Poor | Fair | Good to excellent |
| Clarity | Translucent | Clear; the most transparent PP | Opaque |
| HDT at 0.45 MPa | 105–115 °C | 85–95 °C | 90–105 °C |
| Melting point | About 160–166 °C | Lower than PPH | Close to PPH (the matrix is homopolymer) |
| Relative price | Lowest | Higher | Higher |
Values are from our PP resin page and are typical ranges, not specifications. Melt flow rate, nucleation and additives move every property, so ask for the TDS of the exact grade.
Which PP type for which application
| Application | Usual type | Example grades |
|---|---|---|
| Woven sacks, raffia, FIBC | PPH | SABIC PP 500P, Moplen® HP550J |
| BOPP film | PPH | Pro-fax® SR256M, SABIC PP 525P |
| Spunbond nonwovens | PPH, high MFR | ExxonMobil PP3155E5, Achieve™ Adv. PP6936G2 |
| Houseware, caps and closures | PPH | Moplen® HP500N, SABIC PP 575P |
| Transparent food containers, syringes | PPR | Moplen® RP340R, Borealis RC413MO |
| Hot and cold water pipe | PPR (pipe grade) | Moplen® RP348R, Borealis BC918CF |
| Industrial pipe, sheet, large containers | Block copolymer | Moplen® EP340M |
| Battery cases, paint cans, crates | Impact copolymer | Borealis BA101E, Moplen® EP540P |
| Automotive bumpers and interior | Impact copolymer | Borealis BA110E, Hifax® TYC 1010 |
All example grades are listed with their melt flow rate and density on our PP resin page, along with comparable grades from Chinese producers.
When homopolymer is the better choice
- Stiff, heat-resistant parts such as houseware, rigid containers, caps and closures
- Raffia, woven sacks and strapping, where tape strength matters
- BOPP and cast film and capacitor film
- Fiber and nonwovens, from spunbond hygiene fabric to meltblown
- Parts that run hot, up to an HDT of about 105–115 °C at 0.45 MPa
- Lowest material cost where cold impact is not required
When random copolymer is the better choice
- Transparent parts: food containers, cups, syringes and medical packaging
- Hot and cold water pipe and fittings, using dedicated pipe grades
- Flexible film and sheet that need clarity and a lower sealing temperature
- Thin-wall packaging that needs both clarity and good flow
When impact or block copolymer is the better choice
- Automotive bumpers, instrument panels and interior trim
- Battery cases, paint cans, crates and pallets that are dropped or stacked
- Parts used outdoors or in the cold, where homopolymer would crack
- Large injection-molded containers and industrial pipe
- Washing machine drums and appliance parts that need impact and stress-crack resistance
Modifying PP: additives that shift the balance
- Nucleating and clarifying agents raise stiffness and shorten cycle time in homopolymer, and make random copolymer much clearer. See what a nucleating agent is and our nucleating agents.
- POE for extra toughness. Adding POE to homopolymer or impact copolymer raises cold impact further, as in TPO bumper compounds; see POE vs EPDM.
- Glass fiber and talc. Filled and reinforced PP needs a PP-g-MAH compatibilizer; see our guide to compatibilizers for PP.
- Flame retardancy. PP is processed above the temperature where ATH breaks down, so mineral-filled flame-retardant PP uses MDH; see MDH vs ATH.
- Stabilization. All PP types need an antioxidant package for processing and heat ageing, and HALS for outdoor parts.
PP homopolymer vs copolymer cost
Homopolymer is the lowest-priced polypropylene because it is made in a single reactor from propylene alone. Random and impact copolymers cost more for the ethylene and, for impact grades, the second reactor stage. Sometimes a homopolymer plus a few percent POE matches an impact copolymer at lower cost; sometimes the impact copolymer is cheaper than compounding. Compare the cost of a part that passes your stiffness, impact and heat tests.
Frequently asked questions
Is copolymer PP stronger than homopolymer?
It depends on what “strong” means. Homopolymer is stiffer and has higher tensile strength. Impact copolymer is much tougher, especially in the cold, so it is less likely to crack when dropped.
How can I tell homopolymer from copolymer on a datasheet?
Look at notched Izod impact and flexural modulus: homopolymer has the highest modulus and the lowest impact. Random copolymer has a lower melting point than homopolymer and is described as clear. Impact copolymer has much higher notched impact, often with a low-temperature value.
Which PP is best for food contact?
All three types are used for food packaging. Food-contact suitability depends on the grade, so check the producer’s food-contact declaration for the exact grade; we can email it with the TDS.
Can I blend homopolymer and copolymer?
Yes. Blending is common to fine-tune stiffness and impact. Keep the melt flow rates close, and test the blend for impact and shrinkage.
What is the difference between block and impact copolymer?
They are closely related, and many suppliers use the names interchangeably. Both have a homopolymer matrix with an ethylene-rich phase. Grades sold as impact copolymer usually carry more rubber and reach the highest notched impact.
Get a PP grade recommendation
Still weighing PP homopolymer vs copolymer? Tell us the part, process, stiffness and impact targets, service temperature and any clarity or food-contact needs. We will suggest a grade type and grade, email you the TDS and arrange samples. Contact our technical team or write to info@sychemtech.com.
Related products: our PP resin grades and PE resin, nucleating agents, POE elastomers for impact modification, and antioxidants.
