INVISTA PP Homopolymer P4C6B-134A is a pelletized, controlled-rheology polypropylene homopolymer in which the propylene repeat units are arranged with a predominantly isotactic steric configuration. The grade is supplied by INVISTA for melt extrusion and injection moulding operations requiring a balance of melt strength, stiffness, and short-cycle solidification. The absence of a dispersed ethylene-propylene rubber phase separates the material from heterophasic impact copolymers; the absence of deliberate ethylene comonomer insertion separates it from random polypropylene copolymers. Published grade-specific numerical data for P4C6B-134A is limited in secondary sources. The processing and property ranges below are therefore drawn from the controlled-rheology homopolymer class, and all batch-critical values should be confirmed against the supplier’s certificate of analysis. The resin is not classified as a medical-grade or food-contact-compliant material unless INVISTA issues a specific regulatory letter for the lot.

Delivered pellet dimensions for polypropylene homopolymer grades of this class are typically 3.0 mm to 4.5 mm in diameter and 3.0 mm to 5.0 mm in length; bulk density ranges from 0.54 g/cm³ to 0.60 g/cm³. The resin is stabilized against thermo-oxidative degradation during melt processing and against light-induced degradation for general indoor and selected outdoor applications. Pellet geometry and stabilizer loading influence screw feeding, melting rate, and volatiles. Use of a hopper magnet and an upstream pressure-relief vent is standard practice for shredder or regrind lines handling this polymer.

What melt rheology governs P4C6B-134A during single-screw extrusion?

Melt flow classification is determined in accordance with ISO 1133-1:2022 using a 2.16 kg load at 230 °C. Controlled-rheology homopolymer grades designed for extrusion typically exhibit a medium melt flow rate; the exact nominal value and tolerance must be read from the supplier’s certificate of analysis. The resin’s pseudoplastic response under extrusion shear rates of 100 s⁻¹ to 1,000 s⁻¹ reduces apparent viscosity at the die, while the lower strain rate extensional component governs melt strength in the draw-down zone. For a general-purpose homopolymer, the melt temperature profile from rear zone to die is normally set between 190 °C and 245 °C, with the feed throat maintained below 50 °C to prevent pellet bridging.

Screws with L/D ratios of 24:1 to 30:1 and compression ratios of 2.8:1 to 3.5:1 are standard for controlled-rheology polypropylene. Screen packs of 40/60/100 mesh are common when film or fibre contamination control is required. Melt temperatures above 250 °C should be minimized because thermal-oxidative chain scission increases melt flow rate and can reduce melt strength during draw-down. The addition of a gear pump after the breaker plate stabilizes die pressure to within ±0.2 MPa and is recommended for continuous filament spinning where denier variation is a critical process parameter.

On reciprocating-screw injection moulding machines with clamp forces above 80 t, P4C6B-134A is processed using a barrel temperature profile of 200 °C to 260 °C, a nozzle temperature of 220 °C to 240 °C, and a mould surface temperature of 20 °C to 40 °C. Injection velocity should be set to fill the cavity within 1.0 s to 2.5 s where wall thickness permits; hold pressures between 50% and 70% of peak fill pressure reduce sink marks without overpacking gates. Screw back pressure of 0.5 MPa to 1.5 MPa helps maintain shot-to-shot melt density, while rotational recovery speeds of 40 rpm to 100 rpm minimize shear heating. Pre-drying is not required for unopened ambient storage at relative humidity below 60%. If storage has exposed pellets to condensation, a 2 h to 4 h drying step at 80 °C in a desiccant hopper dryer with a dew point of −20 °C or lower is recommended. These processing limits are not grade-specific publications; they represent the standard window for controlled-rheology polypropylene homopolymers.

Barrel residence time should not exceed 10 min at melt temperatures above 240 °C to limit thermo-oxidative degradation. At screw speeds above 120 rpm, viscous dissipation can increase melt temperature by 10 °C to 25 °C, depending on screw geometry and back pressure. Moulders using hot-runner systems should avoid dead spots and reduce melt residence time by balancing manifold channels; an unbalanced hot runner can create a melt temperature distribution wider than ±5 °C, which may produce warpage or gloss differences in flat parts. Thin-wall parts with nominal wall thickness below 1.0 mm create a processing window conflict. Faster injection speeds reduce freeze-off but raise melt temperature through shear heating, narrowing the crystallization window and increasing post-mould shrinkage. A mould temperature of 20 °C can quench the skin before the core is packed, producing differential orientation and warpage; raising the mould temperature to 40 °C improves pack but increases cycle time. For P4C6B-134A, the appropriate response is to increase injection velocity to 200 mm/s to 400 mm/s at the gate while keeping melt temperature below 250 °C. Published data for this specific configuration is limited.

Mechanical property envelope across unfilled homopolymer grades

The table below compares unfilled polypropylene homopolymer with random copolymer and impact copolymer families on the same test protocols. The ranges are drawn from published property maps for reactor-grade polypropylenes, not from a grade-specific datasheet for P4C6B-134A; they are comparative boundaries rather than product specifications.

Because P4C6B-134A is a homopolymer, its mechanical response should fall toward the higher stiffness and lower impact end of the homopolymer envelope, but precise data must be generated according to the listed standards on conditioned specimens. Tensile property testing should follow ISO 527-2:2012, with a 1B or 1A specimen, or ASTM D638-22; conditioning at 23 °C and 50% relative humidity for 40 h is standard. Mechanical tests for this product family require specimen preparation that preserves the shear and thermal history of the intended process. A comparison of values obtained on injection-moulded plaques and extruded sheet is valid only if the same conditioning protocol is used; ISO 291:2008 specifies standard atmosphere conditions of 23 °C and 50% relative humidity for temperate regions. For polypropylene homopolymer, conditioning times shorter than 40 h can underestimate equilibrium moisture content effects. A tensile test speed of 50 mm/min is common for thick specimens, while 5 mm/min is used for modulus determination under ISO 527-2:2012. Creep and stress relaxation data should be generated using ISO 899-1:2017 for design of load-bearing parts.

Continuous filament and slit-tape extrusion of P4C6B-134A differs from injection moulding in the draw-down and orientation step rather than in the melt delivery section. The quenched precursor is drawn in a hot air oven or hot roll system at 120 °C to 160 °C using draw ratios of 3:1 to 7:1, and the drawn strand is annealed on rolls at 80 °C to 120 °C to control post-process shrinkage. Because homopolymer contains no ethylene comonomer to disrupt crystal packing, higher crystallinity contributes to higher tenacity at a given draw ratio; the same characteristic raises the glass transition operating limit and reduces low-temperature ductility when compared with random copolymers. Water bath temperature for monofilament quenching is typically 20 °C to 40 °C. The absence of a dispersed elastomeric phase also lowers haze but produces a harder, more brittle break surface.

Melt filtration before the die is more critical for fibre than for thick-wall injection moulding. A 60 mesh screen pack or equivalent filtration is needed to remove agglomerated stabilizer particles, while a 250 mesh screen can be used in high-tenacity filament to reduce break frequency. The exact filtration level depends on the supplier’s gel specification and the downstream spinneret capillary diameter, typically 0.3 mm to 0.8 mm for BCF and 1.0 mm to 2.0 mm for slit tape. Sheet extrusion uses a flat die with lip gaps between 0.5 mm and 2.5 mm and a polished chill roll temperature of 20 °C to 60 °C. Because homopolymer crystallizes rapidly, the sheet’s gloss and haze are controlled by the first chill roll; a higher chill roll temperature produces more surface crystallinity and lower gloss, while a lower temperature freezes a smoother amorphous skin. Thermoforming requires sheet surface temperatures of 150 °C to 170 °C for homopolymer, which is narrower than for random copolymers that soften over a wider range. Melt strength in the sheet is affected by die lip land length and exit draw ratio; excessive draw tension reduces sag resistance.

When low-temperature ductility becomes a critical design constraint

Propylene homopolymer P4C6B-134A should not be selected for parts subjected to impact loading below −10 °C because the ductile-to-brittle transition of unfilled homopolymer sits above that of heterophasic impact copolymers. Notched Izod values measured at 23 °C are insufficient to predict freezer service; ISO 180:2019 testing at −20 °C or ISO 179-1:2020 Charpy impact at −20 °C should be performed on the actual moulding. For applications that require lower stiffness loss at low temperature, an impact copolymer with an ethylene-propylene rubber phase offers better crack propagation resistance but lower flexural modulus and a wider processing window. Paint adhesion and corona discharge surface energy also differ because the homopolymer has lower extractable rubber content.

Under dynamic mechanical analysis, unfilled homopolymer typically shows a storage modulus drop near 0 °C associated with the glass transition, whereas impact copolymers retain a secondary loss process from the dispersed rubber phase at lower temperatures. This distinction is visible in ISO 6721-1:2019 dynamic mechanical spectra and correlates with tensile impact failures in automotive interior and appliance parts. Weld-line strength in unfilled homopolymer is also limited by the absence of a dispersed elastomeric phase and by the rapid crystallization of the melt front. The weld-line tensile strength of a homopolymer may fall to 60% to 80% of the bulk strength when two flow fronts meet at 23 °C mould temperature; higher melt temperature and slower cooling improve entanglement but reduce orientation. Measured by ISO 527-2:2012, the retained tensile strength at the weld line should be verified for ribbed components. Compared with an impact copolymer, the homopolymer’s weld-line strength is more sensitive to contamination and fill speed because the crack initiation zone lacks rubbery energy dissipation. Converters should not substitute P4C6B-134A in existing impact-copolymer tools without revalidating gate freeze, shrinkage, and impact performance.

Which regulatory frameworks apply to polypropylene homopolymer food-contact use?

Polypropylene homopolymer may be formulated to meet FDA 21 CFR 177.1520 and EU Regulation (EU) No 10/2011 when the supplier’s formulation and migration testing support a compliance letter. A specific grade is not automatically compliant solely because the base polymer is polypropylene. The antioxidant and acid scavenger package used in P4C6B-134A must be disclosed by INVISTA before a converter may rely on the listed monomer and additive conditions of the regulations. RoHS Directive 2011/65/EU and REACH Regulation (EC) No 1907/2006 apply to finished articles placed on the European market; statements of conformity require supplier declaration of substance of very high concern content. UL 94 HB classification is commonly reported for unfilled polypropylene at a thickness of 3.0 mm, but the grade-specific certificate must be obtained.

Incoming resin lots should be sampled before silo transfer to confirm melt flow rate, moisture, and bulk density. A 0.5 kg sample is adequate for melt flow and moisture checks, while 5 kg is recommended for pellet size distribution and additive dispersion analysis. Loss-on-drying at 105 °C for 10 min should give moisture below 0.10%. If the material is received in bulk railcars, cross-contamination with other thermoplastics must be controlled by dedicated transfer lines; 10 ppm contamination from nylon or PET can create visible gels in cast film and fibre applications.

In comparison with high-viscosity extrusion grades, P4C6B-134A is expected to flow more readily in thin-wall tools but may sacrifice melt strength in deep-draw thermoforming. Compared with nucleated clarified random copolymers, the homopolymer has higher crystallinity and lower contact clarity; it is not suited for transparent packaging unless a clarifying agent is separately compounded. In fibre spinning, its controlled rheology supports consistent denier control and reduced orientation variability when screen pack cleanliness and melt pump stability are maintained. Compared to nucleated homopolymer grades of the same melt flow, a non-nucleated homopolymer may exhibit slower crystallization and larger spherulite size; nucleating agents such as sorbitol or phosphate salts raise crystallization temperature by 5 °C to 15 °C and reduce haze. The P4C6B-134A designation does not specify whether a nucleating package is present; the supplier’s technical datasheet should confirm crystallization kinetic modifiers. Grade differentiation within controlled-rheology homopolymer families is most often defined by melt flow rate target and nucleating package. A lower-melt-flow grade has higher molecular weight and better melt strength for sheet and thermoforming but requires higher melt temperatures. A higher-melt-flow grade fills thin-wall moulds at lower injection pressures but may show reduced tensile strength and lower notched impact. P4C6B-134A must therefore be selected by measured melt flow rate, not by the chemical description “homopolymer” alone. Lot-to-lot variation in melt flow rate should be monitored on an ISO 1133-1:2022 plastometer; a control window of ±1.0 g/10 min around the supplier target is usual for extrusion-oriented controlled-rheology grades, while injection-oriented grades may tolerate wider variation. Any claim regarding specific tensile strength, elongation at break, or shrinkage must be tied to ASTM D638-22, ISO 527-2:2012, or ASTM D2259-21 test data generated on the converter’s own equipment.