REPOL PP Homopolymer H070SG is an unfilled polypropylene homopolymer supplied in pellet form for injection moulding. The grade is identified by a nominal melt flow rate of 7 g/10 min when determined at 230°C under 2.16 kg load in accordance with ISO 1133-1:2022 or ASTM D1238-23a. Density of the unfilled resin is typically 0.90 g/cm³ under ISO 1183-1:2019. Because H070SG is a homopolymer, the molecular structure contains only propylene repeat units; the absence of ethylene co-monomer differentiates it from random copolymers and contributes to higher crystalline fraction, higher stiffness, and lower optical transparency.

Use is concentrated in injection moulding of rigid packaging, closures, housewares, appliance components, and moderate-wall containers. The numerical field in the REPOL designation denotes the nominal MFR, while the grade identity distinguishes H070SG from random copolymer and impact copolymer platforms by phase structure. The homopolymer matrix of H070SG contains no dispersed ethylene-propylene rubber phase, so notched Izod impact strength remains lower than that of impact copolymer grades, but flexural modulus and surface hardness are higher.

What Does a 7 g/10 min Melt Flow Rate Mean for Mould-Filling Pressure and Cycle Time?

The melt flow rate governs the injection pressure required to fill complex cavities. In general-purpose injection moulding machines with screw L/D ratios of 20:1 to 24:1, barrel temperature profiles for H070SG are typically set between 200°C and 250°C, with the feed zone held at 180–200°C, the compression zone at 210–230°C, and the nozzle at 220–240°C. Mould surface temperatures of 20°C to 60°C are sufficient to achieve acceptable surface gloss and dimensional stability. Injection pressure commonly falls in the range of 70–120 MPa for parts with wall thicknesses of 1.5–3.0 mm, while clamp force demand is estimated at 0.5–0.8 tonnes per square centimetre of projected area. These values are processing references for medium-flow polypropylene homopolymers, not absolute machine settings.

Residence time at melt temperature should not exceed 10 min to avoid oxidative chain scission. Screw rotation speed is typically limited to 80–120 rpm on general-purpose screws to prevent excessive shear heating. A desiccant dryer is not mandatory when incoming pellet moisture content is below 0.1% by mass; if exposure to relative humidity greater than 60% has occurred, drying at 80°C for 2–4 h is recommended before processing. Mould shrinkage of H070SG evaluated under ISO 294-4:2018 remains in the range of 1.2–1.6%; tool design should account for anisotropy because flow-direction shrinkage is usually lower than cross-flow shrinkage.

On a production-scale 150-tonne hydraulic injection moulding machine running a 24-cavity closure mould with a valve-gated hot runner, melt cushion is held at 3–6 mm. Cushion loss below 2 mm has been associated with short shots and inconsistent holding pressure in medium-flow PP homopolymers because the screw bottom position cannot compensate for melt compressibility. When hot runner manifold temperatures are maintained at 220–240°C, gate freeze time is controlled primarily by the holding pressure profile rather than by the machine nozzle setting. Published data for this specific configuration is limited; the processing settings above are initial guidance and must be confirmed by in-mould pressure studies.

Oxidative degradation becomes detectable above 280°C by an increase in melt flow rate and a drop in melt strength. If the measured MFR of purged material increases by more than 15% relative to virgin pellets, barrel temperature should be reduced. Nitrogen blanketing of the hopper is not mandatory for short runs but reduces yellowing in long residence-time processing. Lot-to-lot MFR variability for this grade is normally controlled within ±0.5 g/10 min; converters should compare the certificate of analysis against tool-specific pressure requirements when changing lots.

Typical values for H070SG lot-release testing are shown in Table 1. The values are engineering references taken from standardised laboratory specimens and may differ from finished-part performance due to orientation, weld lines, and processing history.

The peak melting temperature of H070SG when measured by differential scanning calorimetry under ISO 11357-3:2018 at a heating rate of 10°C/min is typically 160–165°C. The crystallisation temperature is typically 110–120°C at a cooling rate of 10°C/min. These thermal transitions determine cooling time and ejection temperature; moulders often eject parts when the part surface temperature falls below the heat deflection temperature under load. Surface hardness of H070SG typically falls around R100 under ISO 2039-2:2018 or ASTM D785-23; this supports scratch resistance in caps and dispensing closures but does not eliminate the need for surface texture or coating in high-abrasion applications.

The tensile yield stress and flexural modulus of H070SG place the material among rigid polypropylene homopolymers. Because notched Izod impact strength at 23°C is approximately 3 kJ/m² under ISO 180:2023, components requiring ductile failure at freezer temperatures or high-speed puncture should not be produced from this grade. The sharp drop in impact resistance below 0°C is a known limitation of the homopolymer phase structure; applications requiring sub-ambient toughness are better served by impact copolymer grades with a dispersed elastomeric phase.

When H070SG Is Compared with Random and Impact Copolymer Grades

The selection of H070SG over a random copolymer or impact copolymer involves a trade-off among stiffness, transparency, impact resistance, and processing. Table 2 summarises the property contrasts typically observed between medium-flow homopolymer, random copolymer, and impact copolymer grades. The table is based on general polypropylene family data published in technical literature; specific lot data for H070SG should be obtained from the supplier certificate of analysis.

Random copolymers containing 2–4 wt% ethylene reduce crystallinity and melting point, producing lower haze in injection-moulded articles. H070SG, by contrast, retains a higher crystalline fraction and therefore higher Vicat softening temperature and flexural modulus. The absence of an ethylene-propylene rubber phase in H070SG avoids the low-temperature impact plateau seen in impact copolymers. This makes H070SG unsuitable for freezer-to-microwave applications where impact copolymer grades are preferred. In applications such as rigid housewares and moderate-wall containers that do not experience sub-ambient impact, the homopolymer grade provides higher dimensional stability and surface hardness.

Chemical resistance of H070SG follows general isotactic polypropylene behaviour. It resists polar solvents, acids, alkalis, and aqueous salt solutions at ambient temperature, but non-polar solvents such as xylene, toluene, and n-hexane cause swelling. Stress-cracking resistance under constant strain in detergent solutions is lower than that of impact copolymers; converters evaluating closure applications with high environmental stress-cracking resistance should run comparative tests under ASTM D1693-21 or ISO 22088-2:2016.

Compared with high-flow homopolymers having MFR above 25 g/10 min, H070SG offers higher impact strength and better melt strength. The lower MFR reduces molecular orientation but also increases cycle time due to higher viscosity; this is a deliberate trade-off for parts where mechanical stiffness is more important than filling speed. On hot runner moulds, sequential valve gating should be used when flow length exceeds 150 mm to reduce pressure drop and minimise hesitation. Melt pressure at the nozzle should not exceed 150 MPa for extended periods because excessive shear can cause molecular weight reduction in PP homopolymers. For cold runner systems, full-round runners with diameters between 3 mm and 6 mm provide adequate flow and facilitate ejection.

Regulatory status for REPOL PP Homopolymer H070SG must be confirmed by the supplier for the intended application. Polypropylene homopolymers can be evaluated under FDA 21 CFR 177.1520 and European Plastics Regulation (EU) No 10/2011 for food-contact articles, provided the finished article meets overall migration and specific migration limits. Compliance with REACH and RoHS Directive 2011/65/EU is commonly addressed in the supplier safety data sheet; converters should verify that colour concentrates, processing aids, and regrind do not introduce restricted substances. The grade is not inherently UV-stabilised; outdoor applications require addition of hindered amine light stabilisers and/or UV absorbers because polypropylene undergoes photo-oxidative chain scission. Avoid prolonged contact with strong oxidising acids, chlorinated solvents, and aromatic hydrocarbons because polypropylene swells or degrades in such environments.

Processing limitations for H070SG arise from its medium flow length. For parts with wall thickness below 0.8 mm, high-flow grades with MFR above 25 g/10 min are usually required to prevent excessive injection pressure and moulded-in stress. For large flat panels with long flow paths, flow-length-to-wall-thickness ratios above 200:1 may exceed the practical filling capability of this grade at the recommended melt temperature range. Weld-line strength in homopolymer PP is lower than that of impact copolymer grades; weld-line locations in load-bearing designs should be moved to low-stress areas or the part should be redesigned to reduce knit-line formation.