| HS Code | 720809 |
| Product Name | Polypropylene Homopolymer PP HP500N |
| Polymer Type | Polypropylene homopolymer |
| Processing Method | Injection molding |
| Form | Pellets |
| Density | 0.90 g/cm³ (typical) |
| Melt Flow Rate | 8 g/10 min (230°C/2.16 kg) |
| Tensile Modulus | 1500 MPa (typical) |
| Tensile Stress At Yield | 35 MPa (typical) |
| Tensile Strain At Yield | 10% (typical) |
| Elongation At Break | 50% (typical) |
| Charpy Notched Impact Strength 23c | 4 kJ/m² (typical) |
| Heat Deflection Temperature 0 45mpa | 85°C (typical) |
| Vicat Softening Temperature | 155°C (typical) |
| Rockwell Hardness | R95 (typical) |
| Melting Temperature | 160–165°C (typical) |
| Color | Natural |
As an accredited Polypropylene Homopolymer PP HP500N factory, we enforce strict quality protocols—every batch undergoes rigorous testing to ensure consistent efficacy and safety standards.
| Packing | Polypropylene Homopolymer PP HP500N is supplied in 25 kg woven polypropylene bags, palletized for industrial handling and storage. |
| Container Loading (20′ FCL) | 20′ FCL container loaded with non-hazardous Polypropylene Homopolymer PP HP500N in 25 kg bags, palletized and secured for shipment. |
| Shipping | Polypropylene Homopolymer PP500N is a non-hazardous thermoplastic polymer supplied as pellets. It is not regulated for transport and requires no UN number or hazard class. Ship in dry, clean bags or bulk containers, protecting from moisture, contamination, and direct sunlight; store at ambient temperature. |
| Storage | Store Polypropylene Homopolymer PP HP500N in a cool, dry, well-ventilated area away from direct sunlight, heat, flames, and oxidizing agents. Keep containers tightly closed to prevent moisture and dust contamination. Avoid prolonged high-temperature or UV exposure, use appropriate grounding to prevent static buildup, and maintain good housekeeping in accordance with local regulations. |
| Shelf Life | PP HP500N typically has a 24-month shelf life when stored dry, cool, and protected from direct sunlight in unopened packaging. |
Thin-wall food-contact packaging molded from polypropylene homopolymer HP500N operates inside a narrow processing window where the melt front at the end of flow must remain above the grade’s crystallization onset, typically 123–128 °C when measured by differential scanning calorimetry at 10 K/min. When a 230–245 °C melt is delivered into 0.45–0.70 mm sidewalls, the nominal melt mass-flow rate of 12 g/10 min under ISO 1133-1:2022 at 230 °C and 2.16 kg provides sufficient flow length for rectangular containers in the 500–750 mL range on 180–400 tonne high-speed injection machines equipped with L/D 22:1 barrier screws. Additive handling is process-critical: a phosphate ester nucleating masterbatch at 0.10–0.30 wt% shortens cooling time by 8–12% on 0.50 mm walls, but let-down above 0.35 wt% risks visible specks when hot-runner gate temperatures exceed 250 °C. White masterbatch with 60% titanium dioxide is introduced at 2–4 wt%, while calcium stearate acid scavenger is maintained at 0.05–0.12 wt% to neutralize residual catalyst acidity and suppress organoleptic transfer. Compliance for European food contact requires overall migration below 10 mg/dm² under EU Regulation (EU) No 10/2011, with specific migration limits verified in simulants A/B/C/D1/D2; US submissions are aligned to FDA 21 CFR 177.1520 sub-paragraph (c) for olefin polymers, and China-bound containers require additive positive-list review under GB 9685-2016. Finished-pack oxygen barrier is not supplied by the PP wall; when barrier validation is required, it is performed on the closed package under ASTM F1307-20 or ISO 15105-2 using the lidding film as the primary barrier layer.
Post-filling shrinkage anisotropy dominates the production failure surface. With mold circulation set at 15–25 °C and cavity filling speeds of 200–300 mm/s, solidification occurs within 4–8 s, but differential shrinkage between gate and rim produces warpage if holding pressure is released before gate freeze. Standard settings use 35–50 MPa holding pressure for 0.4–0.8 s after fill, followed by decompression of 2–4 mm to control hot-runner stringing. On toggle-clamp production cells, screw cushion below 2.5 mm creates shot-to-shot melt-flow variation and short shots, while cushion above 5.0 mm extends recovery time and stalls the cycle; this imbalance is a recurring bottleneck on 24-cavity stack tools. Pigment dispersion is qualified by microtome film inspection under transmitted light at 100×; agglomerates above 15 µm are rejected because they produce pinholes in walls thinner than 0.50 mm. Terminal products in this segment include dairy cups, delicatessen containers, non-metalized microwave trays, and single-serve sauce containers, all configured so that polypropylene’s non-barrier character is offset by short shelf-life or external barrier lidding.
Closure molding for condiment and beverage concentrates differs from thin-wall packaging because the critical failure surface is not flow length but retention of elastomer-free hinge integrity after repeated open/close cycles. In 28 mm and 38 mm two-piece closures with tamper-evident bands, HP500N is typically let down with a low-volatility antioxidant package at 0.10–0.25 wt%, hydrotalcite acid scavenger at 0.03–0.08 wt%, erucamide or oleamide slip additive at 700–1,200 ppm, and color masterbatch at 1–3 wt%. Slip loadings below 900 ppm tend to raise removal torque after 14-day storage by 0.18–0.35 N·m on a 2.5 mm thread run-out, while loadings above 1,500 ppm generate surface bloom that interferes with hot-foil date coding. Melt temperature is held at 230–250 °C, and mold circulation is set at 13–20 °C to freeze the tamper band and keep cycle time within 8–14 s on 16–48 cavity cold-runner or valve-gated hot-runner systems. A holding pressure of 30–45 MPa for 0.6–1.2 s packs the closure knurl; premature pressure release creates sink marks opposite thread cores and raises scrap above 4% on high-cavitation tools. On hydraulic presses, worn check rings produce shot-to-shot fill variance that increases cap flatness variation beyond 0.3 mm; cushion repeatability above 0.4 mm triggers ring replacement. Compliance for this use is anchored to EU Regulation (EC) No 1935/2004 and EU Regulation (EU) No 10/2011 for specific migration, while US-manufactured closures are tested under FDA 21 CFR 177.1520. End products include push-pull drink closures, ketchup and mustard flip-top caps, and mineral water caps with bonded EPE liners, with thread-root wall thickness maintained above 0.75 mm.
For non-implantable diagnostic cassettes and laboratory disposables, the primary compliance target is ISO 10993-5:2009 for in vitro cytotoxicity together with biological evaluation planning under ISO 10993-1:2018. HP500N is processed in clean-room injection molding at ISO 14644-1 Class 8 or better, using all-electric presses of 100–250 tonnes clamp force, melt temperature 220–245 °C, mold surface 15–30 °C, and injection speed 60–150 mm/s. A radiation stabilization masterbatch at 0.10–0.30 wt% is combined with a non-amide nucleating package at 0.05–0.15 wt% and 1–2 wt% white masterbatch selected to satisfy USP <661.1> packaging physicochemical testing and USP <88> Class VI biological reactivity for specified protocols. The operational boundary is dose-dependent: after gamma irradiation at 50 kGy, notched Izod values under ISO 180/A can decline by 20–40% without a dedicated radiation-grade stabilizer, so devices requiring repeated terminal sterilization must be validated at the upper expected dose. Hot-runner tools for diagnostic trays use polished channels and shut-off nozzles; a leaking valve gate raises melt residence time above 250 °C and produces gel flecks that fail ASTM D2561-17 visual inspection. End products include lateral-flow assay cassettes, PCR plate frames, microcentrifuge tube racks, and pipette tip inserts, with wall thickness between 0.8–2.0 mm and inter-well pitch Cpk above 1.33 for multi-well formats.
In small-appliance housing conversion, the limiting processing parameter is often not melt temperature but steel-to-cavity heat transfer consistency across multi-cavity tools. HP500N processed at 230–250 °C melt and 25–50 °C mold requires 50–70 MPa hold pressure to suppress sink marks around bosses where wall thickness transitions from 2.0 mm to 3.5 mm rib roots. Heat stabilization uses a phenolic/phosphate antioxidant package at 0.20–0.50 wt%; antistatic concentrate at 0.5–2.0 wt% reduces dust retention on vacuum cleaner housings. When glow-wire requirements under IEC 60695-2-12 at 650 °C or 750 °C apply, an intumescent ammonium polyphosphate masterbatch is let down at 20–30 wt%, but this raises flexural modulus and lowers melt flow rate by roughly 30–50%, requiring revalidation of screw design and hot-runner balance. On 300–800 tonne toggle presses, the bottleneck emerges when shot weight exceeds 55–60% of barrel capacity because screw recovery time extends beyond cooling time and the cycle becomes recovery-limited. The grade’s HDT 0.45 MPa under ISO 75-2/B of approximately 90–100 °C restricts design to parts that do not sustain continuous surface temperatures above 80 °C. Compliance includes IEC 60335-1 for household appliance safety, UL 746B for polymeric thermal endurance, and RoHS Directive 2011/65/EU for restricted substances. Terminal articles include vacuum cleaner wheel housings, blender base shrouds, internal brackets for hygiene appliances, and backplates for appliance control panels.
Indoor housewares and storage systems made from HP500N exploit the grade’s high stiffness and fast setting rather than its impact strength. For stackable chairs, hangers, and modular shelving, the standard let-down is color masterbatch at 1–4 wt%, antistatic concentrate at 0.5–2.0 wt%, and an acid scavenger at 0.03–0.10 wt%. Large-part production is performed on 500–1,500 tonne injection molding machines with melt temperature 220–240 °C, mold temperature 20–40 °C, injection speed 80–150 mm/s, and hold pressure 45–70 MPa; wall thicknesses generally sit between 2.0 mm and 4.0 mm, and cooling occupies 60–70% of the 25–45 s cycle. When the same furniture is used outdoors, ultraviolet exposure becomes the controlling variable. A hindered amine light stabilizer masterbatch at 0.30–0.80 wt% is added for UV resistance, and carbon black at 1–2 wt% provides the most consistent long-term surface retention; however, gloss loss and chalking still occur after prolonged outdoor weathering and must be accepted or tested under ISO 4892-2 accelerated weathering. Cold-impact retention is the second limitation: neat HP500N shows notched Izod values near 2.5 kJ/m² under ISO 180/A, and garden furniture exposed to -20 °C requires modification with an EPR/EOC impact modifier masterbatch at 10–15 wt%, which reduces flexural modulus by 20–30% and lowers HDT. Compliance for furniture placed on the EU market includes REACH Regulation (EC) No 1907/2006, RoHS Directive 2011/65/EU where electro-mechanical components are integrated, and EN 581-1:2017 for outdoor seating mechanical safety. End products include indoor storage boxes, stackable chairs, wardrobe hangers, garden loungers, and low-height modular tables, all with rib-heavy geometries rather than thin-wall packaging profiles.
Returnable logistics crates molded from HP500N expose the grade to repeated sanitization, ultraviolet exposure, and mechanical abuse that do not occur in single-use food packaging. The formulation is adjusted for long-use service: carbon black masterbatch at 1–2 wt% is combined with a hindered phenolic/phosphate antioxidant package at 0.15–0.30 wt% and an acid scavenger at 0.03–0.10 wt%; for cold-room handling below 0 °C, an EPDM/EOC impact modifier masterbatch at 10–15 wt% is let down to reduce brittle failure. Molding uses 800–2,500 tonne accumulator-equipped injection presses with melt temperature 240–260 °C, mold temperature 20–40 °C, injection speed 100–180 mm/s, and hold pressure 55–75 MPa; rib and base thickness from 4.0 mm to 8.0 mm extends cycle time to 30–70 s. Mid-run mold temperature drift from 20 °C to 28 °C expands flow-direction dimensions by 0.3–0.6% and alters stackability, so mold thermolators must hold setpoint within ±1 °C. Repeated wash cycles at 60–85 °C with alkaline detergents are acceptable only for short contact times; continuous immersion above 80 °C can soften ribs and accelerate stress relaxation. Compliance for food-contact crates includes EU Regulation (EU) No 10/2011 and FDA 21 CFR 177.1520 where the crate directly contacts unpackaged food; industrial crates fall under REACH Regulation (EC) No 1907/2006 and RoHS Directive 2011/65/EU. End products include collapsible bulk containers, reusable pallets, bread crates, dairy transport trays, and automotive dunnage, all designed for returnable-loop logistics rather than disposal after a single trip.
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Polypropylene homopolymer PP HP500N is classified as a general-purpose injection moulding grade under ISO 1873-1 with a nominal melt mass-flow rate of 12 g/10 min when determined at 230 °C under a 2.16 kg piston load in accordance with ISO 1133-1:2022. The resin is supplied as free-flowing pellets with a nominal density of 0.90 g/cm³ measured by ISO 1183-1:2019. Published datasheets position the grade for injection moulding of thin-wall packaging, caps and closures, housewares, appliances, and technical components in which the design requires a combination of stiffness, surface hardness, and short cycle time. The polypropylene homopolymer architecture lacks ethylene comonomer; consequently the crystalline phase fraction is higher than in random copolymer polypropylene, producing a flexural modulus near 1550 MPa under ISO 178:2019 and a heat deflection temperature near 95 °C under ISO 75-2:2013 method B. Compared with heterophasic impact copolymer grades, HP500N has no dispersed elastomer phase and therefore exhibits lower multi-axial impact resistance at sub-zero temperatures but higher tensile yield stress and lower tendency to cavitate under short-term static load. These distinctions are material-selection inputs rather than product deficiencies; the grade is intended for applications where stiffness and dimensional stability outweigh low-temperature ductility.
Representative property values are provided below. Lot-to-lot variation should be verified against the certificate of analysis; published data for flame-retardant, glass-reinforced, or elastomer-modified versions of HP500N are limited because the standard grade is unfilled and unreinforced.
| Property | Typical value | Test standard | Test condition |
|---|---|---|---|
| Melt mass-flow rate | 12 g/10 min | ISO 1133-1:2022 | 230 °C, 2.16 kg |
| Density | 0.90 g/cm³ | ISO 1183-1:2019 | 23 °C |
| Tensile yield stress | 34 MPa | ISO 527-2:2012 | 50 mm/min, type 1A |
| Tensile strain at yield | 9% | ISO 527-2:2012 | 50 mm/min, type 1A |
| Flexural modulus | 1550 MPa | ISO 178:2019 | 2 mm/min |
| Notched Izod impact, 23 °C | 2.5 kJ/m² | ISO 180/A | Notch A |
| Notched Izod impact, -20 °C | 1.2 kJ/m² | ISO 180/A | Notch A |
| Heat deflection temperature | 95 °C | ISO 75-2:2013, method B | 0.45 MPa |
| Heat deflection temperature | 55 °C | ISO 75-2:2013, method A | 1.8 MPa |
| Vicat softening temperature | 153 °C | ISO 306:2022, method A50 | 10 N, 50 °C/h |
| Mould shrinkage, 24 h after demoulding | 1.1–1.4% | ISO 294-4:2018 | 60 mm × 60 mm × 2 mm plaque |
| Water absorption, 24 h immersion | 0.01–0.02% | ISO 62:2008 | 23 °C |
These values are characteristic of a medium-flow polypropylene homopolymer. The melt viscosity decreases with increasing shear rate, exhibiting pseudoplastic behaviour typical of linear isotactic polypropylene at 230 °C. The crystalline melting temperature of the homopolymer is approximately 160 °C to 165 °C by differential scanning calorimetry under ISO 11357-3:2018, and the crystallisation temperature is approximately 120 °C to 125 °C.
Processing of PP HP500N is performed on reciprocating-screw injection moulding machines with a general-purpose polyolefin screw having an L/D ratio of at least 20:1 and a compression ratio between 2.2:1 and 3.0:1. The melt temperature measured at the nozzle is maintained between 220 °C and 250 °C; lower values reduce melt homogeneity in thin-wall sections, while higher values accelerate thermo-oxidative chain scission. Barrel temperature settings are typically distributed from 180 °C in the feed zone to 240 °C at the metering zone, with nozzle set at 240 °C to 250 °C. Mould temperatures of 20 °C to 50 °C are specified; a 30 °C mould surface provides a practical balance between cycle time and crystallisation. Higher mould temperatures increase crystallinity and mould shrinkage but reduce post-mould dimensional drift; lower mould temperatures reduce cycle time but raise residual orientation and may increase warpage in asymmetric parts.
Injection pressure at the material inlet depends on flow length-to-wall thickness ratio and gate geometry; production-scale settings commonly fall between 70 MPa and 120 MPa. Holding pressure is set at 50% to 70% of peak injection pressure and is maintained until gate freeze; premature transfer to holding pressure causes sink marks, while late transfer creates flash and overpacking. Back pressure of 0.5 MPa to 2.0 MPa is applied to stabilise shot weight without excessive screw heating. Screw surface speed is limited to 0.25 m/s; for a 30 mm screw diameter this corresponds to approximately 160 rpm, but smaller diameters require proportionally higher rotational speed to maintain the same surface speed. Hot-runner manifold temperatures are kept at 250 °C maximum and melt residence time is limited to 15 min during colour change or line stoppages because polypropylene undergoes free-radical chain scission under shear and heat.
| Parameter | Range | Notes |
|---|---|---|
| Barrel feed zone | 180–200 °C | Prevent bridging; maintain pellet flow |
| Barrel compression zone | 210–230 °C | Uniform melting |
| Barrel metering zone | 230–240 °C | Melt temperature control |
| Nozzle temperature | 240–250 °C | Prevent cold slug |
| Melt temperature | 220–250 °C | Measured by nozzle pyrometer |
| Mould temperature | 20–50 °C | 30 °C preferred for cycle time |
| Injection pressure | 70–120 MPa | Geometry dependent |
| Holding pressure | 50–70% of peak | Maintain until gate freeze |
| Back pressure | 0.5–2.0 MPa | Shot weight stability |
| Screw surface speed | ≤ 0.25 m/s | Limit shear heating |
| Pre-drying | Not normally required | If surface moisture: 80 °C, 2–4 h |
Moisture control follows standard polyolefin practice. The pellet surface is non-hygroscopic, but condensation at ambient relative humidity above 60% can introduce surface moisture sufficient to produce splay and weld-line defects. If bags or silos have been exposed to humid air for more than 24 h, desiccant drying at 80 °C for 2 h to 4 h is specified. Drying temperatures above 90 °C should be avoided because pellet sticking in hopper dryers and additive consumption increase. Regrind addition should be limited to 20 wt% unless the end-use specification permits higher levels; high regrind fractions reduce melt viscosity and increase lot-to-lot variability.
Volumetric shrinkage behaviour is governed by semicrystalline solidification. On 60 mm × 60 mm × 2 mm plaques moulded under ISO 294-4:2018, linear mould shrinkage at 24 h after demoulding is typically 1.1% to 1.4%, with transverse shrinkage up to 0.3% higher than flow-direction shrinkage. If the mould has deep ribs or thick bosses, cooling time should be extended to avoid sink marks; for a nominal wall thickness of 2.0 mm, cooling time estimated from thermal diffusivity of polypropylene is approximately 10 s to 15 s at a 30 °C mould temperature, but actual time depends on gate freeze and part geometry. Clamp force demand is approximately 0.4 kN/cm² to 0.7 kN/cm² of projected part area for technical parts when injection pressure is within the stated range. Vent depth for polypropylene homopolymer should be 0.02 mm to 0.03 mm; deeper vents permit flash because of the low melt viscosity at 240 °C.
Rheologically, HP500N exhibits non-Newtonian shear thinning. At processing shear rates between 100 s⁻¹ and 10,000 s⁻¹, viscosity falls below the zero-shear plateau. Published data for the Carreau constants of this specific commercial grade are limited; however, the melt mass-flow rate of 12 g/10 min anchors its position in the medium-flow homopolymer category. The flow activation energy of isotactic polypropylene is approximately 37 kJ/mol; a temperature increase from 220 °C to 250 °C therefore reduces viscosity by roughly 20% but also accelerates oxidation, so temperature adjustment is not a substitute for correct gate dimensions. Injection speed should be set to maintain a melt front velocity of 100 mm/s to 300 mm/s; slower fronts cause premature skin freezing, while faster fronts induce jetting and surface defects in unvented cavities.
In thin-wall food-container and cap applications, the flow length of HP500N at 240 °C permits filling of wall sections down to 0.4 mm when the gate diameter is at least 0.6 mm and the flow-length-to-thickness ratio does not exceed 180:1. Caps with tamper-evident bands benefit from the homopolymer’s higher flexural modulus and lower post-mould creep under tensile stress; however, low-temperature impact is limited and closure designs should avoid sharp notches at hinge points because the notched Izod impact at -20 °C is approximately 1.2 kJ/m² under ISO 180/A. The crystallisation temperature of the homopolymer is approximately 120 °C to 125 °C by differential scanning calorimetry under ISO 11357-3:2018; therefore mould cooling should maintain part surface temperature below this range before ejection to avoid post-eject warpage. Ejection systems should distribute force across at least 3% to 5% of the projected part area to prevent localised stress whitening. If mould release agents are required, dosing concentration should not exceed 0.1% of the dry-blend weight because migration into food-contact surfaces is subject to overall migration limits under EU 10/2011 and FDA 21 CFR 177.1520.
Material substitution decisions between HP500N and random copolymer polypropylene are governed by the required balance of stiffness, optical clarity, and cold-temperature toughness. Random copolymers with ethylene contents of 1.5 wt% to 3.0 wt% disrupt crystallinity and exhibit lower flexural modulus and lower heat deflection temperature; some random copolymers also show improved impact at 5 °C and below. HP500N retains a higher flexural modulus of approximately 1550 MPa under ISO 178:2019 and a higher heat deflection temperature, but its low-temperature notched impact strength is lower. In transparent thin-wall packaging, random copolymer is selected when clarity and low-temperature drop resistance control the design; HP500N is selected for coloured or opaque parts, closures, and appliance housings where stiffness and dimensional stability are more important than optical properties.
Compared with heterophasic impact copolymer grades, the difference is structural: impact copolymers contain a dispersed ethylene-propylene rubber phase that absorbs energy and arrests crack propagation. HP500N has no elastomer phase; hence its multi-axial puncture energy, weld-line elongation, and sub-zero impact resistance are lower. Applications such as automotive battery housings, luggage shells, and freezer containers therefore use heterophasic copolymers. HP500N is preferred when service temperatures remain above 0 °C, when surface hardness and scratch resistance are required, and when the part is stiff rather than impact-limited. The product is not intended for continuous hot-water exposure above 80 °C; long-term creep-rupture data for this configuration are limited, and polypropylene homopolymer under sustained load at elevated temperature may fail by ductile creep rather than yield.
Against high-flow homopolymer grades with melt mass-flow rates above 25 g/10 min, HP500N has a lower MFR, which typically corresponds to higher average molecular weight, higher melt strength, and better tensile yield stress but requires higher injection pressure for thin-wall filling. Against low-flow extrusion grades with melt mass-flow rates below 3 g/10 min, HP500N is less suited to sheet extrusion, blown film, or blow moulding because the molecular weight is lower and the melt strength is insufficient for parison stability. These rheological boundaries define the product’s operational niche as an injection moulding resin.
When HP500N is coloured, the carrier resin of the colour masterbatch should be polypropylene or polypropylene-compatible. Styrenic or polyamide carriers create melt-phase incompatibility, reducing impact strength at weld lines and increasing delamination risk. Masterbatch let-down ratios of 2% to 4% are typical for organic pigments and carbon black; inorganic pigments may require 1% to 2%. Metal stearates used as acid scavengers in masterbatches should be limited to 0.1 wt% to 0.2 wt% because excess calcium stearate can plate out on mould surfaces and reduce long-term heat ageing. Flame-retardant compounds based on ammonium polyphosphate should be evaluated separately because they alter viscosity and may require a vented barrel and corrosion-resistant tooling.
Commercial HP500N grades are supplied with stabilisation packages based on hindered phenolic antioxidants and phosphite processing stabilisers. The base resin is suitable for food-contact applications under FDA 21 CFR 177.1520, which covers olefin polymers used as articles or components of articles intended for contact with food, provided that the finished article meets the extraction limits for the intended condition of use. European food-contact compliance is evaluated under EU 10/2011, including overall migration limits and specific migration limits for any additive introduced through masterbatch or processing aid. REACH 1907/2006 and RoHS 2011/65/EU declarations are available for the unfilled, unpigmented base resin; compliance of coloured compounds must be verified separately because pigments and carrier resins affect the regulatory profile.
The product should not be dry-blended with PVC or PET regrind. At polypropylene melt temperatures of 230 °C to 250 °C, PVC thermally dehydrochlorinates and PET undergoes hydrolytic degradation; the resulting acidic by-products catalyse polypropylene chain scission, reduce melt viscosity, and generate splay, plate-out, and odour. If cross-contamination is suspected, purging with a high-density polyethylene purge compound at 200 °C to 220 °C followed by HP500N is recommended. Silo storage should be closed-loop or moisture-tight, and conveying systems should use dry air when ambient humidity exceeds 60% for more than 24 h.
For outdoor service, the unfilled homopolymer requires stabilisation against ultraviolet radiation; carbon black masterbatch at 2 wt% to 3 wt% or a hindered amine light stabiliser package is required to prevent surface chalking and embrittlement. Without UV stabilisation, exposed parts may retain tensile properties for less than 12 months depending on solar radiation dose. Paint adhesion and printing on HP500N require surface oxidation by corona discharge or flame treatment because the non-polar polypropylene surface has a low surface energy; treatment should raise the surface energy to at least 38 dyn/cm measured by wetting reagents. These post-mould operations are standard for polypropylene homopolymer and are not grade-specific limitations.
