PP Filament for 3D Printing: Settings and Adhesion

What is PP filament and why is it so difficult to FDM

Polypropylene (PP) is a semi-crystalline polymer with low surface energy, strong shrinkage on cooling and poor adhesion to most surfaces. These properties make it one of the most difficult FDM materials, but also one of the most useful for functional parts.

When going from a molten state to a solid state, the material shrinks in volume by 1.5–2.2% (PLA shrinks below 0.5%). The result: warping in polypropylene, peeling and delamination.

The second obstacle is surface energy. PP doesn't "stick" to glass, PEI, or BuildTak — standard 3D printing surfaces are often useless. With the right PP settings and preparation, however, this material yields parts that other filaments struggle to achieve.

For context of where PP stands among other materials, see the guide to 3D printing materials.

When polypropylene is the right choice

PP is optimal for parts exposed to chemicals, repeated bending (live hinges), contact with moisture and applications where low weight is important. Where PLA and ABS lose properties, polypropylene often remains stable in everyday use.

Chemical resistance of polypropylene is its main advantage — it is inert to many acids, bases and solvents at room temperature.

Living hinges are another unique territory: PP withstands hundreds of thousands of bending cycles without breaking. Design a thin section (0.3–0.5 mm) and you get a functional hinge.

With a density of about 0.9 g/cm³, PP is lighter than water — suitable for lightweight parts with cyclic loading.

Limitations and Risks

PP has lower temperature resistance (HDT often around 60–70 °C), UV sensitivity with prolonged exposure and poor interlayer strength with wrong settings. It is not a good choice for parts used continuously at elevated temperature or in direct sunlight without stabilizers.

Above ~60 °C PP can deform plastically — for hotter environments ABS or PETG are often more suitable. Without UV stabilizers, polypropylene can become brittle in the sun (check the TDS of the particular filament).

Because of the rapid crystallization, the layers may bond more weakly than with amorphous materials—the part orientation in the slicer directly affects strength.

PP vs. PETG and ABS — a brief comparison

PP wins in chemical resistance, fatigue and live hinges. ABS is better at higher temperature. PETG offers a balance between ease of printing and mechanical properties, but is generally not as chemically resistant as PP.

For standard prototypes, PP rarely makes sense — PETG is more predictable. But for functional parts with contact with chemicals or the need for live hinges, PP is often without a real alternative.

PP settings: starting ranges

Nozzle temperature 220–250 °C, bed 80–100 °C, speed 20–40 mm/s, cooling 0–20%, layer thickness 0.15–0.25 mm. Each brand of PP filament has a different composition — the values are a starting point and require a short calibration.

Temperature and speed

Most PP filaments extrude well between 230 and 245 °C. Set the bed to 85–100 °C — below 80 °C warping increases dramatically.

Speed: 25–35 mm/s for perimeters, 20–30 mm/s for the first layer. Higher speed can increase thermal stress and warping.

Cooling and additional parameters

Fan: 0% for the first 3–5 layers, then max 10–20%. Rapid cooling enhances uneven shrinkage.

• Flow: start with 1.00; increase to 1.02–1.05 on gaps
• Retraction: 1–3 mm (Bowden), 0.5–1.5 mm (Direct Drive) — PP can string
• Nozzle: brass 0.4mm for pure PP; hardened steel for PP+GF

Adhesion of polypropylene to the bed

 The most reliable method is PP packing tape (polypropylene tape) stuck smoothly on the bed. PP sticks best to PP — that's the key principle. Specialized adhesives help, but standard surfaces such as PEI often do not provide stable adhesion for larger parts.

PP tape and adhesives

Standard clear packaging tape is often made of polypropylene. Stick it bubble-free to a glass build plate—the PP filament sticks to it significantly better than most other surfaces. The tape is consumable and is usually replaced regularly.

For further improvement, Dimafix adhesive stick can provide an even adhesive layer. More on the different types of 3D printing adhesives can be found in the complete guide to adhesives.

Brim and geometric tricks

Brim of a minimum of 10–15 mm is almost mandatory (20 mm for larger models). Add a small radius to sharp corners at the base with a radius of 1–2 mm—they concentrate thermal stresses and are often the first points of lift.

Print environment

A closed chamber or an enclosed, draft-free environment significantly reduces warping in polypropylene. A stable ambient temperature of 30–45 °C helps crystallization to proceed more evenly and reduces accumulated stresses, which is felt most strongly in large flat parts.

An open printer with air conditioning or an open window often leads to failure. Even a slight airflow from one side creates asymmetric cooling and one-sided lift.

Use a purpose-built enclosure and follow the printer and enclosure manufacturers' temperature and fire-safety guidance. Avoid flammable makeshift enclosures around hot components.

Filament drying (PP) and storage

PP absorbs relatively little moisture compared to nylon, but even a small amount of moisture can cause bubbles and a poorer surface. Drying at 50–60 °C for 4–6 hours is good practice before first use or after prolonged storage in ambient air.

If you hear "popping" sounds during extrusion or see tiny bubbles, the filament has probably absorbed moisture.

It is useful for long-term storage filament drying box with desiccants. For active drying before or during printing Creality Space Pi allows filament to be fed directly from the box.

Post-processing of PP prints

Polypropylene is difficult to glue, paint and sand with conventional methods. Machining works well, but bonding requires PP-specific adhesives or thermal "welding" with hot air. Plan assemblies with mechanical fasteners whenever possible.

• Sanding: PP is soft — work with 400+ grit and wet sand
• Bonding: CA adhesives often do not work; use PP-specific or thermal welding
• Painting: without flame activation or PP primer the paint can be peeled off
• Mechanical processing: cuts and drills easily, but beware of overheating at high rpm

Diagnosis: problem → cause → solution

Most problems with PP come from three main reasons—poor bed adhesion, rapid cooling, and insufficient extrusion temperature. If you isolate them systematically (one change at a time) it usually solves over 90% of the defects in typical FDM configurations.

Conclusion: 5 steps to successful PP printing

Success with PP comes from proper first layer surface, stable draft free environment, slow printing with minimal cooling and drying/storage discipline. If you test settings on a small model and scale incrementally, PP becomes a predictable material for functional parts.

1. Prepare the bed with PP tape or specialist adhesive — the remaining settings cannot compensate for an unsuitable surface.
2. Use a suitable enclosure or otherwise eliminate drafts while following the printer manufacturer's safety guidance.
3. Print slowly (25–35 mm/s) with minimal cooling and a brim of at least 15 mm.
4. Dry the filament before first use and store in a dry environment between sessions.
5. Test on a small model (20x20mm cube) before large projects — different PP filaments vary in composition.

If you are looking for suitable materials for experiments and functional parts, browse the filament category.