INVISTA PP Homopolymer P4G4T-017A is a pelletized general-purpose polypropylene homopolymer specified for injection moulding and compounding where a defined melt flow, high stiffness, and elevated heat deflection temperature are required. The nominal melt mass-flow rate is 4.0 g/10 min when determined at 230 °C with a 2.16 kg load under ISO 1133-1:2022. Density is 0.905 g/cm³ by ISO 1183-1:2019 method A. Typical mechanical values include tensile stress at yield of 32 MPa and tensile strain at yield of 9% under ISO 527-2:2012 at 50 mm/min, flexural modulus of 1,550 MPa under ISO 178:2019, and notched Charpy impact at 23 °C of 4.0 kJ/m² under ISO 179-1:2010. The product's melt flow range separates it from extrusion grades with MFR below 1.0 g/10 min and from thin-wall injection grades with MFR above 20 g/10 min.

The resin is used in rigid packaging, closures, appliance housings, and non-appearance automotive interior parts. Closure performance depends on creep resistance and dimensional stability; top-load strength of containers may be evaluated by ISO 12048:2000. In appliance housings, the material is specified when heat resistance under load must exceed 90 °C at 0.45 MPa per ISO 75-2:2013. The grade is not intended for transparent film, deep-draw thermoforming, or low-temperature impact service below -20 °C.

What Distinguishes P4G4T-017A from Impact Copolymers and Random Copolymers?

The principal structural distinction is the absence of an ethylene-propylene rubber phase. This gives P4G4T-017A higher flexural modulus and higher tensile yield stress than impact copolymer PP of equivalent 4.0 g/10 min melt flow rate, but sharply lower notched impact at sub-ambient temperature. Under ISO 179-1:2010 type 1eA notched Charpy conditions at -20 °C, representative homopolymer values fall below 2.0 kJ/m², while impact copolymers in the same MFR class typically retain 6.0 kJ/m² to 10.0 kJ/m². For random copolymers containing 2% to 4% ethylene, the homopolymer displays a higher melting temperature by differential scanning calorimetry under ISO 11357-3:2018, typically 162 °C versus 145 °C for the random copolymer, and lower optical clarity. High-flow homopolymers with MFR 25 g/10 min to 50 g/10 min fill thin sections at lower pressure, but exhibit reduced melt strength and lower notched impact; P4G4T-017A is selected when warpage control and creep resistance outweigh cycle-time advantages.

The heat deflection temperature under 0.45 MPa for P4G4T-017A is approximately 95 °C per ISO 75-2:2013. At 1.8 MPa, the heat deflection temperature falls to approximately 55 °C, which limits unfilled homopolymer use in underhood automotive components or hot-fill packaging above 90 °C. The Vicat softening temperature under ISO 306:2022 method A50 is approximately 154 °C. These thermal values distinguish the grade from random copolymers with Vicat softening lower by 15 °C to 20 °C and from high-flow homopolymers with modestly lower HDT due to reduced molecular mass.

Pre-drying of P4G4T-017A is unnecessary when storage humidity remains below 60% RH and resin remains in closed containers for less than 24 h. If surface moisture exceeds 0.05% by weight, dehumidified-air drying at 80 °C for 2 h to 4 h is applied. Drying above 90 °C risks agglomeration in conventional hopper dryers. Melt temperature in extrusion is maintained between 210 °C and 240 °C; exposure above 250 °C for more than 5 min initiates oxidative chain scission, producing a measurable MFR increase and loss of notched impact under ISO 179-1:2010.

On 1000 kN to 1500 kN hydraulic injection molding machines with 25 mm to 35 mm general-purpose screws, a barrel profile of 200 °C rear, 215 °C center, 225 °C front, and 230 °C nozzle is used. Mold coolant temperature is set from 20 °C to 50 °C; higher mold temperatures increase crystallization and reduce post-mold shrinkage but extend cooling time. Injection velocity is adjusted to reach 90% cavity fill before transfer to hold pressure at 40 MPa to 70 MPa hydraulic pressure. Cushion control is maintained at 3 mm to 6 mm because insufficient cushion produces gate under-packing and increases sink mark depth.

Batch-to-batch MFR variation within manufacturing tolerance of ±0.5 g/10 min is observable as hold-pressure shifts. A change from 4.0 g/10 min to 4.5 g/10 min may require reduction of holding pressure by 5% to 8% to avoid flash at vented parting lines. Screw recovery time on a 1200 kN press with a 25 mm screw increases when rear-zone temperature drops below 195 °C; screw speeds above 180 min⁻¹ can exceed drive torque limits. These are production-scale observations in the general 4.0 g/10 min homopolymer class.

When Long Flow Paths and Thin-Wall Sections Are Required

Rheological limits for this melt flow class become critical in thin-wall tooling. Rotational shear rheometry at 230 °C under nitrogen shows zero-shear viscosity in the range 1.5 kPa·s to 2.5 kPa·s for the 4.0 g/10 min homopolymer class. The shear-thinning transition occurs at shear rates near 100 s⁻¹ to 300 s⁻¹. At capillary shear rates above 10,000 s⁻¹, viscosity falls below 50 Pa·s under ISO 11443:2021. These values support injection molding simulation but do not replace lot-specific capillary data for P4G4T-017A.

For flow-length-to-thickness ratios above 200:1, the 4.0 g/10 min MFR may require cavity pressure at gate above 80 MPa to prevent short shots. Hot-runner systems should use valve gates or open-pipe nozzles with temperature control of ±2 °C; gates below 0.8 mm diameter promote premature freeze-off below 140 °C. Published data for P4G4T-017A-specific spiral-flow length is limited, so mold-filling simulation requires capillary viscosity data generated on the production lot.

Mold shrinkage in flow direction is observed at 1.2% to 1.6% and transverse shrinkage at 1.3% to 1.8% on 60 mm × 60 mm × 2 mm plaques under ISO 294-4:2018. Differential shrinkage in thick bosses leads to sink marks unless gate seal time is maintained at 6 s to 10 s and packing pressure exceeds 50 MPa. Warpage in long caps and flat appliance panels is minimized by uniform mold temperature and avoiding localized hot spots above 40 °C.

Compounding P4G4T-017A with Talc or Glass Reinforcement

Compounding of P4G4T-017A with 10% to 40% talc, calcium carbonate, or short glass fiber is performed on co-rotating twin-screw extruders with 32:1 to 44:1 L/D and side-feed capability. The base resin melt temperature is maintained at 220 °C to 240 °C. Mineral filler increases flexural modulus from 1,550 MPa for neat resin to 3,000 MPa to 4,500 MPa at 30% talc loading under ISO 178:2019, but notched impact decreases and weld-line strength falls. Nucleation with 0.15% to 0.25% sorbitol-based clarifier raises crystallization onset from approximately 118 °C to 126 °C at 10 K/min cooling by ISO 11357-7:2022, improving cycle time but reducing impact in unfilled parts.

General-purpose screws with 20:1 to 24:1 L/D and compression ratio 2.5:1 to 3:1 provide adequate mixing without excessive shear heating. Back pressure of 5 MPa to 10 MPa is used for natural resin; back pressure above 15 MPa may increase melt temperature by more than 5 °C and shift MFR beyond the specified upper limit. Screw decompression should be minimized to avoid air entrapment and splay on visible surfaces.

Regrind of unfilled P4G4T-017A can be reused in injection molding at levels up to 20% by weight without significant changes in flexural modulus when regrind particle size is below 6 mm and melt temperature is kept below 240 °C. Repeated regrind cycles above 3 generate MFR drift and darkened pellets. Users should validate notched impact retention after each regrind cycle under ISO 179-1:2010.

Regulatory Compliance Matrices and Test Obligations

For food-contact use, the polypropylene homopolymer falls under FDA 21 CFR 177.1520 (c), which provides specifications for olefin polymers. Final article compliance is use-condition specific. Under EU No 10/2011, overall migration is limited to 10 mg/dm² for food-contact articles; specific migration limits for additives such as antioxidants and nucleating agents must be checked against the supplier's formulation disclosure. Grade-specific compliance declarations for P4G4T-017A should be obtained from the INVISTA certificate of analysis or regulatory affairs documentation.

Final article testing under IEC 62321-5:2013 for lead and IEC 62321-4:2013 for mercury is required when color concentrates or recycled polypropylene are introduced. P4G4T-017A is not a halogenated polymer, but brominated flame retardant contamination from external regrind can produce false RoHS noncompliance. The operational boundary for this resin excludes steam sterilization above 121 °C; repeated autoclave cycles accelerate thermo-oxidative embrittlement and reduce notched Charpy impact by more than 50% after 20 cycles in unfilled homopolymer.

The grade is incompatible with strong oxidizing acids, aromatic hydrocarbons, and some chlorinated solvents at elevated temperature; environmental stress cracking resistance should be evaluated under ISO 22088-3:2008 for aggressive chemical containment. Ultraviolet exposure requires stabilization; unstabilized polypropylene undergoes surface chalking and loss of tensile elongation under ISO 4892-2:2013 xenon-arc weathering within 200 h to 500 h. Published data for P4G4T-017A-specific UV performance is limited; weathering grades require an added hindered amine light stabilizer package.