Polypropylene

Identity and selection boundary

Röchling's Polystone P Homopolymer black pressed (PP-H) lists guideline yield stress above 30 MPa and tensile modulus above 1,500 MPa under DIN EN ISO 527. These are statistical averages under DIN EN 15860. Use an agreed acceptance requirement for the ordered product. Röchling Polystone P data

Polypropylene (PP) is a material family, not a complete part specification. LyondellBasell distinguishes homopolymers, random copolymers and impact copolymers, and warns that exchanging them normally changes performance. Its selection framework considers process, appearance, mechanical function and additives together. Record the producer, full grade, color, filler/modifier, supplied form and manufacturing route before assigning properties. LyondellBasell, Material Selection—Polypropylene

LyondellBasell describes random-copolymer PP as propylene polymerized with small amounts of ethylene or butene, with optical and processing benefits. Its applications include injection molding, blow molding, films, pipe and thermoforming. A copolymer label therefore does not identify a single manufacturing route or geometry. LyondellBasell, random copolymer overview

Compounds require their own documentation: for example, Borealis identifies Daplen EF120AE-9545 as PP containing talc and carbon black. Do not assign unfilled-PP properties to this formulation merely because PP remains the matrix polymer. Borealis, product safety information sheet, §3

A bounded injection-molding example

ExxonMobil's supplier-hosted data sheet identifies PP7032E3 as an impact-copolymer pellet grade for injection molding. Selected typical values are:

These are typical properties, not specifications. The same sheet requests supplier consultation for food-contact compliance and prior written acknowledgement for medical use. Neither an application listing nor the generic PP designation establishes approval. ExxonMobil, PP7032E3, revision 29 May 2026

The cold-impact results cannot be replaced by the room-temperature value. Deflection results belong to their stated test conditions; they are not continuous-service ratings.

Stock material is a separate data set

Röchling's Polystone P (Homopolymer) black pressed, PP-H, lists guideline yield stress above 30 MPa and tensile modulus above 1,500 MPa under DIN EN ISO 527, melting temperature 162–167°C under ISO 11357-3, and expansion of 120–190 × 10⁻⁶/K under DIN 53752. The data are statistical averages under DIN EN 15860, not binding unless contractually agreed. Preserve the inequalities without treating them as guaranteed purchase minima. Röchling, technical data sheet, version 2.0

Calculated illustration: applying that expansion range to a freely expanding 500 mm length and a uniform 30 K temperature rise gives:

ΔL = α × L × ΔT = (120–190) × 10⁻⁶/K × 500 mm × 30 K = 1.8–2.85 mm.

This assumes the coefficient applies to the stock and temperature interval. Mounting design must also resolve frame expansion, restraint, tolerances and local heating. Melting temperature is not a service rating.

Processing, shrinkage and material handling

MFR needs its temperature and load. LyondellBasell explains that processes requiring melt strength tend toward low-MFR grades, while high-speed thin-wall injection molding often uses higher MFR. Impact-phase composition and amount also affect toughness, so MFR alone cannot rank substitute resins. LyondellBasell, Material Selection—Polypropylene, p. 1

For molding, LyondellBasell describes PP as semi-crystalline and explains that shrinkage depends on material structure and heat transfer. Nonuniform filling and cooling can create different shrinkage within one part, even with relatively uniform walls. Use the actual grade, geometry, gating and cooling arrangement to establish dimensions; do not apply one PP shrinkage percentage to every tool. LyondellBasell, Mold Shrinkage

Its injection-molding guide says ordinary polyolefin resin is non-hygroscopic and generally does not require predrying, but cold pellets moved into a warm area can collect surface condensation. It also stresses contamination control and controlled regrind proportions. This guidance does not override the specific instructions for a filled compound or contaminated material. LyondellBasell, A Guide to Polyolefin Injection Molding, p. 8

For repeat production, preserve material lot, approved regrind policy, process settings, inspection conditioning and final dimensional results. A resin substitution or mold revision should explicitly reopen the affected qualification questions.

Joining and service qualification

3M identifies PP as a low-surface-energy plastic that is difficult to bond. Its options include specialty adhesives and surface treatment; it describes adhesives capable of bonding many PP grades without special preparation, rather than claiming compatibility with every grade. Select and test the complete substrate/adhesive/preparation combination, including aging and joint loading. 3M, bonding low-surface-energy plastics

Handling and source dates

Borealis's EF120AE-9545 safety information warns of burns from molten material, decomposition fumes and combustible dust; it calls for adequate ventilation, dust control and prompt pellet-spill cleanup. These are product-specific handling instructions, not a declaration that every PP compound has the same hazard classification. Borealis, §§4, 6–8

The cited ExxonMobil supplier-hosted sheet explicitly shows 29 May 2026. Röchling's PDF states release 18 August 2025, version 2.0, separately from its print date 5 May 2026. Borealis's sheet prints 16 October 2025, edition 2. LyondellBasell's molding guide prints code 5979/0715; no explicit full revision date is stated in the cited technical tips. Do not infer a revision from a search-engine publication date or upload path.

Material selection through production