Polycomp CE24/2 NATURAL PP Copolymer is a natural-color heterophasic polypropylene impact copolymer supplied in pellet form. The product designation is manufacturer-specific; under ISO 1043-1, the polymer family is PP, and “copolymer” indicates an ethylene-modified reactor composition rather than a homopolymer. The grade is intended for injection molding and extrusion processes where low-temperature notched impact resistance, moderate flexural stiffness, and stable melt processing are primary acceptance criteria. Because the natural formulation contains no carbon black or organic pigments, the converter can introduce color masterbatch at the feed throat to produce finished-color parts without maintaining multiple pre-colored lot inventories. The material’s morphology consists of a continuous polypropylene matrix and a dispersed ethylene-propylene rubber phase. This structure is responsible for the grade’s divergence from PP homopolymer: lower tensile yield stress, lower flexural modulus, higher elongation at break, and improved notched impact response at sub-zero temperatures. Lot-specific values for Polycomp CE24/2 NATURAL must be confirmed from the manufacturer’s certificate of analysis, because reactor lot variation and additive adjustments can shift melt flow and mechanical data by measurable percentages.

The grade is often screened for automotive interior trim, battery box housings, appliance panels, reusable crates, and industrial packaging. In those applications, the part specification commonly includes notched impact strength according to ISO 180/A after conditioning at −20 °C, a minimum flexural modulus under ISO 178, and dimensional stability derived from mold shrinkage measurements. The product is not intended for transparent components, unpainted high-gloss appearance parts, or continuous structural service above 80 °C. Grade designations containing numeric digits may be associated with nominal melt mass-flow rate, but the manufacturer’s lot certificate remains the controlling source of the melt flow value measured under ISO 1133-1:2022 at 230 °C with a 2.16 kg piston load.

How does the ethylene-propylene rubber phase alter the property balance in CE24/2 NATURAL?

In the heterophasic impact copolymer architecture, immiscible ethylene-propylene rubber domains are dispersed in the polypropylene matrix. Under an applied impact load, those domains cavitate and promote matrix shear yielding, which absorbs energy rather than allowing brittle crack propagation. The resulting property envelope differs from that of a high-crystallinity PP homopolymer. Tensile yield stress, tested under ISO 527-2, is lower than that of a homopolymer of comparable melt flow. Flexural modulus, measured under ISO 178, is also reduced, while notched Izod impact strength, evaluated under ISO 180/A, increases markedly at −20 °C. This balance supports snap-fit geometries and thin-wall housings that must survive cold-temperature assembly. Density for polypropylene impact copolymers in this class typically falls between 0.890 and 0.910 g/cm³ when measured by ISO 1183-1. The natural unpigmented product is translucent to milky white because the rubber phase scatters light; it is not suitable for transparent or optical components.

Relative to random copolymer PP, the impact copolymer sacrifices clarity but gains sub-zero toughness. Random copolymer grades are preferred when contact clarity, gloss, and seal initiation control the application; they are not an equivalent replacement for CE24/2 NATURAL in parts specified for notched impact resistance at −20 °C. Published data for the specific ethylene content, rubber particle size distribution, and additive package of CE24/2 NATURAL is limited. The following comparative matrix is for material-class screening and must not replace the manufacturer’s lot certificate for final tool design or safety factors.

The class-level differences explain why a converter may move a part from PP homopolymer to CE24/2 NATURAL when cold-temperature brittle failure occurs at gate vestiges or weld lines. Weld-line impact strength in heterophasic PP copolymers can be lower than bulk impact values, so gate locations should move weld lines away from high-stress snap-fit features. Mold-flow simulation should use lot-specific melt viscosity data rather than generic PP impact copolymer curves.

When low-temperature impact resistance is specified for injection-molded components

When a part specification requires notched Izod impact after conditioning at −20 °C, tool design and processing parameters should be matched to the shear and cooling behavior of the heterophasic copolymer. On general-purpose injection molding machines, a nozzle melt temperature of 220 °C–250 °C is typical. The barrel profile from feed to nozzle is commonly set in increments from 180 °C to 230 °C, with the metering zone maintained near the lower end to limit premature melting and feed bridging. Mold temperature is controlled between 20 °C and 60 °C; the upper end of the range improves weld-line integrity and rubber phase orientation but extends cooling time. A mold temperature below 20 °C can create a quenched surface layer that reduces strain-to-failure at the gate.

Specific injection pressure is typically 60–120 MPa at the transfer point, with holding pressure optimized by short-shot studies and gate freeze-time measurements. Back pressure is maintained between 0.5 and 1.5 MPa for stable metering. Injection speed is set from medium to high, especially for thin-wall parts where the flow path-to-wall thickness ratio exceeds 150:1. High-speed filling without adequate venting can generate diesel effects and burn marks at the end of fill; vents should be sized to a depth of 0.01–0.03 mm for polypropylene copolymers and cleaned periodically to prevent gas deposit accumulation. Hot-runner systems should maintain nozzle-to-manifold temperature uniformity within ±5 °C to avoid inconsistent filling between cavities.

If regrind is used, limit the addition to 20–30% by weight unless process validation demonstrates retention of ISO 180/A impact performance. Regrind feedstock must be free of acetal, PVC, and copper salts, which degrade at PP processing temperatures and can cause vent-blocking residue or accelerated chain scission. Surface moisture from opened bags or bulk storage at relative humidity above 60% can be controlled by pre-drying in a desiccant dryer at 80 °C for 2–4 hours with a dew point of −20 °C or lower. Hopper inlet temperature should not exceed 60 °C to prevent pellet softening and bridging.

Thermal degradation threshold and purge recommendations

Melt temperature excursions above 270 °C or residence times longer than 10 minutes at processing temperature initiate thermo-oxidative chain scission. The practical indications are a decline in notched impact strength, yellowing of natural parts, and a measurable upward drift in melt mass-flow rate when tested under ISO 1133-1:2022. The processing window for CE24/2 NATURAL is not unusually narrow, but barrel heater override and shear heating from high screw speed can create local hot spots even when setpoint temperatures are within range. Screw speed should be selected to maintain a recover time slightly shorter than the cooling time, avoiding excessive shear work. General-purpose polyolefin screws with L/D ratios of 20:1–25:1 and compression ratios of 2.5:1–3.5:1 are adequate for homogenization. A mixing tip is not required for natural color but may be useful when high loadings of color masterbatch are used.

For shutdown, the barrel should be purged with a low-viscosity polyolefin until the melt stream is free of yellowed or blackened residue. If the material has been held at elevated temperature for an extended period, the screw should be pulled and inspected for carbon deposits before restarting a food-contact or light-colored production run. This practice reduces contamination excursions and batch-to-batch surface defects in natural grades. For colorless production, hopper magnets and clean material-handling lines are mandatory to prevent carbonized contamination.

Regulatory status must be verified against the manufacturer’s product stewardship documentation. For food-contact uses, polypropylene homopolymers and copolymers may be evaluated under FDA 21 CFR 177.1520; compliance depends on polymer composition, hexane extractables, and end-use temperature limits, not on the color form. In the European Union, REACH obligations under Regulation (EC) No 1907/2006 require confirmation that the grade is registered and that any intentionally added substances are pre-registered or authorized. The RoHS Directive 2011/65/EU restricts lead, mercury, cadmium, hexavalent chromium, PBB, and PBDE; unpigmented PP copolymer grades are normally outside the restricted substance classes, but batch certificates should still be checked for inadvertent heavy-metal contamination from polymerization catalyst residues.

In service, CE24/2 NATURAL occupies the middle ground between unfilled PP homopolymer and mineral-filled PP compounds. It is selected for automotive interior trim, battery box housings, appliance panels, reusable crates, and industrial containers where cold-temperature drop resistance and snap-fit durability are required. Compared with a 20% talc-filled polypropylene, the unfilled impact copolymer has lower flexural modulus and lower heat deflection temperature under ISO 75-2/B, but it provides higher notched impact strength and easier flow in thin-wall sections. Compared with a high-flow PP homopolymer, it reduces the risk of brittle failure at gate vestiges and weld lines. The product is not intended for sustained pressure service above 80 °C or for load-bearing parts where creep modulus under ISO 899-1 controls the design. Published data for the creep performance of CE24/2 NATURAL at elevated temperature is limited; therefore creep-sensitive applications should be validated with the specific batch and wall section under consideration.

Processors should validate the final part with the exact color masterbatch and regrind ratio specified for production. Shrinkage in polypropylene impact copolymers is anisotropic and depends on flow direction, mold temperature, and holding pressure; cavity dimensions should be cut from measured shrinkage on the production tool, not from generic polypropylene literature values alone.