Sinopec PP Homopolymer Y24 is a high-fluidity polypropylene homopolymer supplied by Sinopec under the designation PPH-Y24. The grade is identified as an injection moulding resin with a nominal melt mass-flow rate of 24 g/10 min determined by ISO 1133-1:2022 at 230 °C under a 2.16 kg load. The product belongs to the homopolymer subclass of isotactic polypropylene and is intended for thin-walled rigid articles, caps, closures, housewares, and non-food packaging. It is not intended for film blowing, fibre spinning, extrusion blow moulding, or sub-zero impact service. The principal differentiation from lower-flow Sinopec homopolymers such as PPH-T03 is the reduction in molecular weight required to raise melt mass-flow rate from below 5 g/10 min to 24 g/10 min. This shift reduces tensile elongation at break and notched impact resistance while improving mould filling and cycle time.

What Melt Rheology and Solid-State Property Benchmarks Are Reported for PPH-Y24?

Under ISO 1133-1:2022, the nominal MFR of 24 g/10 min places PPH-Y24 in the high-flow injection moulding segment. The melt viscosity at 230 °C and shear rates relevant to thin-wall filling, typically 10²–10⁴ s⁻¹, is lower than that of PPH-T03 and film grades, but shear-thinning is less pronounced than in impact copolymers because the homopolymer has no ethylene-propylene rubber phase. The density at 23 °C is reported as 0.900–0.910 g/cm³ under ISO 1183-1:2019, a range associated with nucleated homopolymer formulations and directly relevant to cooling-time and specific pressure calculations.

The tabulated values are representative ranges drawn from publicly available technical summaries for high-flow PP homopolymer injection grades and are not a certificate of analysis. Lot-specific release testing according to the indicated methods should govern acceptance because additive packages, nucleating agents, and vis-breaking technology can shift individual values. Differential scanning calorimetry under ISO 11357-3 typically shows a melting peak between 160 °C and 168 °C; the crystallization temperature may be raised by nucleating agents to 122–130 °C, which contributes to faster solidification and reduced cycle time in thin-wall tools.

Oxidative induction time measured under ISO 11357-6 in oxygen at 200 °C is often below 30 min for unstabilised high-flow homopolymers. Commercial stabilisation packages extend this value, but the user should not infer long-term thermal ageing resistance from a single OIT result. Additive compatibility must be verified when introducing colour masterbatch or processing aids, because acidic residues from certain masterbatches can consume the acid scavenger and accelerate thermo-oxidative degradation during extended residence at melt temperature above 250 °C.

Thin-Wall Injection Moulding Conditions and Thermal Degradation Boundaries

Processing of PPH-Y24 on hydraulic or electric injection moulding machines with screw L/D ratios of 20:1 to 24:1 is conducted with feed-zone temperatures of 160–190 °C, compression-zone temperatures of 200–230 °C, and metering-zone temperatures of 210–250 °C. Mould temperatures are normally maintained between 20 °C and 50 °C to balance crystallisation rate and cycle time. Lower mould temperature increases cooling rate but reduces crystallinity and can increase skin-core morphology differences, affecting post-mould shrinkage. Injection pressures of 80–120 MPa are commonly reported on general-purpose screws, while thin-wall parts below 0.8 mm may require higher peak pressures. Back pressure is limited to 0.5–1.0 MPa, and screw speeds are typically kept at 80–150 rpm. Screw speeds above 200 rpm can generate shear heating of 10–20 °C above the barrel set point, shifting the effective MFR and causing flash or short-shot instability.

A critical threshold risk occurs in multi-cavity hot-runner tools when wall thickness drops below 0.6 mm. The high MFR reduces pressure loss, but the processing window at the gate can be as narrow as ±5 °C, separating short shots from sinks and flash. Cavity-pressure transfer, using sensors with a response time of 1 ms or faster, is preferred over timer-based switchover because solidification of a 0.6 mm wall occurs before full gate freeze. Published data for this specific configuration is limited; process capability trials on the production tool are required before locking the process window.

Although virgin PPH-Y24 is hydrophobic and does not require drying for hydrolysis control, regrind and silo condensation can introduce surface moisture. When ambient relative humidity exceeds 80 % or regrind content exceeds 30 wt%, drying for 2 h at 80 °C in a desiccant dryer is recommended to prevent splay and surface defects. Melt temperature above 260 °C accelerates oxidative chain scission. In hot-runner systems that exceed this threshold at gate tips, residence time should be limited to 5 min or less. Retained PPH-Y24 in hot runners during shutdown may degrade and produce black specks; purging with a low-MFR polypropylene or a commercial purging compound reduces this failure mode.

For high-speed packaging lines, PPH-Y24 is processed into containers with wall thicknesses from 0.4 mm to 2.0 mm. The flexural modulus of 1300–1600 MPa under ISO 178 provides stacking stiffness for dairy tubs and reusable containers. Top-load resistance is not a resin property but a structural result of wall thickness, ribbing, and crystallinity; it is measured on the finished article by ASTM D642 or equivalent top-load testing. Published data for a specific container design is limited, and the value cannot be extrapolated from resin mechanical data alone. Closures and caps benefit from the high flow in gasket-free designs, but continuous load-bearing at temperatures above 60 °C approaches the Vicat softening region and may cause creep-induced loss of seal force. For hot-fill packaging above 90 °C, a homopolymer grade is not recommended without thermal stabilisation, high-temperature migration testing, and creep testing per ISO 899-1.

Colour masterbatch addition between 1 wt% and 4 wt% can alter viscosity and nucleation. Certain organic pigments nucleate polypropylene, raising flexural modulus but reducing impact; the effective MFR may shift by 2–6 g/10 min depending on the carrier resin. Laboratory melt index testing under ISO 1133-1:2022 does not capture the shear-thinning behaviour relevant to thin-wall filling, so a lot trial with the production screw and hot-runner is necessary. Batch-to-batch MFR variation within the manufacturer’s tolerance is not the dominant cause of flash or short shots; hot-runner temperature drift and gate geometry often contribute more. In applications with wall thickness below 0.5 mm, an MFR shift of ±4 g/10 min can alter fill time by 10–15 %, requiring cavity-pressure monitoring rather than timer-based transfer.

When PPH-Y24 Replaces PPH-T03, Random Copolymer, or Impact Copolymer Grades

Substitution of PPH-T03, a low-flow homopolymer used in fibre and extrusion, by PPH-Y24 is justified only in injection moulding. The higher MFR reduces melt viscosity and enables longer flow paths at equal pressure, but the lower molecular weight reduces tensile elongation at break and environmental stress-crack resistance. The melt strength of PPH-Y24 is insufficient for biaxially oriented film, extrusion blow moulding, or fibre spinning with high draw ratios, where PPH-T03 or film-grade polypropylenes are preferred. The flow ratio between loads of 21.6 kg and 2.16 kg is typically below 20, indicating a narrower molecular weight distribution than blow-moulding grades.

Random copolymers containing 1–4 wt% ethylene have lower flexural modulus, typically 800–1100 MPa by ISO 178, and better transparency. PPH-Y24 has higher stiffness and lower oxygen and moisture transmission, but higher haze; it is not selected for transparent or contact-clarity parts. When improved impact is required, impact copolymer polypropylenes with notched Charpy values above 10 kJ/m² by ISO 179-1/1eA should replace PPH-Y24. The notched Charpy impact strength of PPH-Y24 at 23 °C is typically 2.0–3.0 kJ/m², and at 0 °C it can fall below 1.5 kJ/m². The grade is therefore unsuitable for freezer containers, appliance housings, automotive interior parts, and luggage that experience impact at low temperatures. The absence of an ethylene-propylene rubber phase provides higher surface hardness and modulus but low energy absorption under puncture, and replacement of an impact copolymer without redesign and instrumented puncture testing under ISO 6603-2 or ASTM D3763 is not supported.

Compared with glass-fibre-reinforced PP, PPH-Y24 has lower modulus and lower heat deflection temperature; its unfilled nature provides better surface finish and lower abrasion on moulds. The grade is not a drop-in replacement for talc-filled or mineral-filled PP in structural parts because creep modulus under load is lower. Designers replacing mineral-filled or glass-filled PP with PPH-Y24 must revalidate stiffness, warpage, and creep using ISO 899-1. Mould shrinkage is typically 1.0–1.5 % in the flow direction and 1.2–1.6 % transverse, measured by ISO 294-4. Actual shrinkage depends on mould temperature, holding pressure, gate geometry, and wall thickness. Lower mould temperature reduces immediate shrinkage but can increase post-mould warpage due to residual stress.

Regulatory Conformance Is Established by Standard Test Conditions, Not Grade Nomenclature

Food-contact compliance of PPH-Y24 is not automatic from the grade number. Control is exercised under FDA 21 CFR 177.1520 for olefin polymers and under EU Regulation (EU) No 10/2011 for plastics intended to contact food. The overall migration limit of 10 mg/dm² applies to food simulants specified in Annex III of the regulation, and the material must be tested in the final article because colour masterbatch, regrind, and processing aids alter the migration profile. Lot-specific certificates of compliance are required, particularly when the application involves fatty foods with simulant D2 or high-temperature conditions above 70 °C.

Under REACH Regulation (EC) No 1907/2006, the base homopolymer is not classified as hazardous. Packaging heavy-metal restrictions under EU Directive 94/62/EC require the sum of lead, cadmium, mercury, and hexavalent chromium not to exceed 100 mg/kg by weight of packaging. The resin should not be exposed to oxidising acids, chlorinated solvents, or strong essential oils at elevated temperatures because aromatic hydrocarbons and halogenated species can cause stress cracking or swell the amorphous phase. Outdoor service requires UV stabilisation; unstabilised homopolymer will chalk and embrittle under weathering, and accelerated weathering per ASTM D4329 or ISO 4892-3 should be used to qualify stabilised formulations.

At the production scale, batch records should track MFR, ash content, and pigment dispersion. A shift in MFR from 24 g/10 min to 30 g/10 min may not be detected by weight checks but can cause flash and short-shot instability in multi-cavity tools. Conversely, MFR below 20 g/10 min increases injection pressure and may cause sink marks. For lot acceptance, ISO 1133-1:2022, ISO 1183-1:2019, and ISO 179-1/1eA are the minimum release tests; tensile yield stress and flexural modulus are tested on a reduced frequency. Converters running thin-wall packaging should require the supplier to report the MFR range in the certificate of analysis rather than a single nominal value.