Sasol CUV448 is an injection-moulding grade of heterophasic polypropylene impact copolymer supplied in pellet form. The grade designation encodes the copolymer architecture and a nominal melt mass-flow rate of 44 g/10 min measured at 230 °C under a 2.16 kg load according to ISO 1133-1:2022. The heterophasic structure consists of a continuous isotactic polypropylene matrix and a dispersed ethylene-propylene rubber phase, which increases notched impact strength relative to polypropylene homopolymer grades while retaining a useful balance of stiffness and chemical resistance. The product is formulated with a UV-stabiliser package intended to retard photo-oxidative chain scission, gloss reduction, and surface micro-cracking in natural and light-coloured mouldings. CUV448 is not designed for film extrusion, blow moulding, or pipe extrusion, because its high melt mass-flow rate reduces melt strength and drawability; those processes require grades with lower nominal MFR and higher molecular weight. It is specified for injection-moulded components such as crates, pallets, automotive interior trim, outdoor furniture, battery boxes, and appliance housings where resistance to handling abuse and outdoor weathering is required. Nominal density is close to 0.905 g/cm³ when measured to ISO 1183-1:2019, and the material exhibits mould shrinkage typically between 0.8% and 1.5% depending on wall thickness, packing pressure, and gate location.

What Separates CUV448 from Non-UV-Stabilised and Homopolymer Polypropylene Grades?

The distinction between CUV448 and a conventional polypropylene homopolymer is primarily impact resistance. Homopolymer PP of similar MFR often shows notched Charpy impact values below 3 kJ/m² at 23 °C, whereas CUV448 contains an ethylene-propylene rubber phase that raises the corresponding value to approximately 7.5 kJ/m² under ISO 179-1/1eA:2010. At sub-zero temperatures, the same rubber phase maintains a measurable fraction of room-temperature ductility. In exchange, homopolymer PP offers higher flexural modulus, typically above 1500 MPa, and higher heat deflection temperature than CUV448. When compared with a non-UV-stabilised impact copolymer of equivalent MFR, short-term tensile properties may be indistinguishable; the difference appears during accelerated weathering. Non-UV-stabilised impact copolymers subjected to xenon-arc exposure according to ISO 4892-2:2013 generally develop increased carbonyl index and surface crazing earlier than CUV448, although the numerical acceleration factor depends on irradiance, black panel temperature, and moisture cycle. The UV-stabiliser package in CUV448 is intended for outdoor service in light-coloured part designs, but it does not eliminate the need for appropriate pigment selection. Rutile titanium dioxide and carbon black are effective UV absorbers; organic red and yellow pigments can reduce weatherability unless used within supplier-recommended formulations. CUV448 also differs from random copolymers that are used for contact clarity: the impact copolymer is translucent-to-opaque and should not be specified where optical clarity or contact transparency is the primary requirement. Compared with thermoplastic olefinic elastomers, CUV448 has lower rubber content, higher modulus, and better dimensional stability but lower ultimate elongation and less impact at extreme low temperatures.

Injection Moulding Parameters Across Hydraulic and Electric Machines

On a production injection moulding line using a 350 t hydraulic press and a 20:1 L/D general-purpose screw, CUV448 is run with a nozzle melt temperature of 230 °C to 250 °C. Because the MFR is high, the material fills thin sections at lower injection pressure than a 12 g/10 min impact copolymer; however, the low melt viscosity also produces shorter gate freeze-off time. This requires fill-to-pack switch to occur before the gate freezes and packing pressure to be maintained long enough to prevent sink marks. Mould surface temperature should be adjusted within the supplier-recommended range of 20 °C to 50 °C. Lower mould temperatures reduce cycle time but increase cooling stresses and may reduce weld-line strength; higher mould temperatures improve surface smoothness and knit-line ductility but increase cycle time and part ejection complexity. Back pressure is typically maintained at 0.3 MPa to 0.7 MPa to ensure shot-weight consistency without degrading the stabiliser package through excessive shear heating. Screw rotation speed is machine-specific, but excessive shear heat should be avoided above 250 °C melt temperature. Hopper drying at 80 °C for 2 h is only required when condensation is present on cold pellet surfaces; polypropylene is not hygroscopic, but surface moisture can produce splay, especially in hot-runner systems.

When Excessive Residence Time or Low Mould Temperature Creates Boundary Conditions

Operating CUV448 outside the recommended melt-temperature/residence-time envelope produces observable defects. If the melt remains in the barrel at 250 °C for longer than 5 min, visible yellowing can begin as the UV-stabiliser system is consumed; in severe cases the additive package forms low-molecular-weight oxidation products that migrate to the surface and reduce paint adhesion or plate-out on the mould surface. Mould temperatures below 20 °C increase the risk of flow marks, weld-line cracking, and delamination at the interface between the PP matrix and the ethylene-propylene rubber phase. At high injection speeds and low mould temperature, residual stress at the gate may reduce notched impact strength relative to specimens moulded under standard conditions; no single reduction factor applies across all geometries. These are process-induced limitations, not material formulation failures. If the mould is run below 20 °C, the packing-pressure profile should be extended and weld-line geometry revised to place knit lines in low-stress regions. Avoid prolonged barrel residence time by reducing barrel heat when cycle interruptions exceed 10 min, and purge with a general-purpose PP homopolymer before restart. Blending CUV448 with un-stabilised recycled PP reduces UV performance non-linearly; the resulting weathering profile depends on the weight fraction and origin of the recycled fraction and cannot be extrapolated from the virgin stabiliser concentration. For applications requiring food-contact status, the finished article must be tested under the relevant migration framework, such as EU Regulation 10/2011 and FDA 21 CFR 177.1520, because the base grade certificate alone does not establish compliance for a specific moulded item.

Rheological Inputs for Mould Filling Simulation and Shrinkage Prediction

Simulation of CUV448 requires viscosity data measured over the shear-rate range expected in the runner and cavity. Capillary rheometry at 230 °C and 250 °C shows pseudoplastic behaviour: apparent viscosity decreases as shear rate increases from 100 s⁻¹ to 10,000 s⁻¹. The exact Cross-WLF coefficients are supplied under non-disclosure by Sasol for use in Autodesk Moldflow, Moldex3D, and SIGMASOFT; the datasheet MFR alone is not sufficient to predict pressure drop in thin-wall geometries because it is measured at low shear stress. For shrinkage prediction, mould shrinkage measured on 60 mm × 60 mm × 2 mm plaques per ISO 294-4:2018 is the relevant input for injection moulding simulation. Shrinkage of impact copolymers is anisotropic and is influenced by packing pressure, gate freeze-off time, and fibre orientation if fillers are added; CUV448 is an unfilled grade, but weld lines and thickness variations still generate differential shrinkage. Mouldmakers should apply a graduated shrinkage allowance rather than a single linear value when moulding parts with wall thickness transitions from 1.5 mm to 3.0 mm.

One production risk observed in hot-runner multi-cavity tools is unbalanced filling caused by the low melt viscosity of CUV448. If the manifold temperature is kept above 250 °C or the valve gate needle delay is excessive, the melt may flow preferentially through the geometrically shortest gate and cause higher cavity-to-cavity weight variation. This is managed by setting manifold and nozzle zones below 250 °C and by performing gate-weight studies with no packing phase. Processors should not use the same hot-runner temperature profile developed for a 12 g/10 min grade without rebalancing, because the lower-viscosity 44 g/10 min grade responds more strongly to manifold thermal gradients. Regrind incorporation is generally accepted for non-appearance parts up to 20% by weight when the regrind is generated from the same UV-stabilised grade and is not degraded. For appearance parts, lower levels may be required to avoid gloss variation. Regrind that has already consumed part of the stabiliser package during first processing reduces long-term weatherability approximately in proportion to the regrind addition level, so outdoor-exposure requirements should determine the maximum allowable regrind fraction.

Outdoor furniture and crate applications typically require a combination of impact strength and weathering resistance. For such parts, CUV448 is selected because its nominal MFR of 44 g/10 min allows short cycle times and long flow lengths in multi-cavity tools, while the impact-copolymer structure resists damage during stacking and drop loading. Drop-weight performance at room temperature is commonly evaluated by ISO 6603-2:2000 with a 20 mm diameter striker; supplier data for impact-copolymer grades in the same MFR class indicate that puncture energy depends strongly on plaque thickness and test speed, and users should request CUV448-specific values from the supplier rather than applying generic PP data. Automotive interior trim parts such as door panels and pillar covers benefit from the material’s UV-stabilised surface retention, but paintability and low-emission performance must be confirmed for the specific formulation because internal air quality tests under VDA 278:2011 or VDA 270:2018 are not guaranteed by the base polymer alone. Appliance housings use CUV448 when long-term handling, UV exposure near windows, and occasional contact with household cleaners require a balance of impact strength and cost. Chemical resistance to alkalis and acids is similar to polypropylene homopolymer, but aggressive organic solvents can swell the rubber phase; immersion testing under ISO 175:2010 should be performed if cleaning agents contain terpenes or aromatic hydrocarbons.