KUNLUN PP S1003 is a polypropylene homopolymer resin supplied under the PetroChina Kunlun brand for general-purpose extrusion and injection moulding. The grade has a nominal melt mass-flow rate of 2.5 g/10 min to 3.5 g/10 min at 230 °C under a 2.16 kg load when tested according to ISO 1133-1:2022 or GB/T 3682.1-2018. Density at 23 °C is normally 0.900 g/cm³ to 0.910 g/cm³ under ISO 1183-1. As a single-monomer homopolymer, the resin contains no deliberate ethylene or butene comonomer; this distinguishes it from random copolymers, which display lower stiffness but higher low-temperature ductility, and from impact copolymers, which contain discrete elastomeric phases. Certificate-of-analysis values for melt flow rate, ash content, isotactic index, and tensile properties are lot-specific and override nominal grade descriptions.

The grade is frequently processed on woven tape and raffia lines without predrying because polypropylene homopolymer is not hygroscopic under humidity below 60 %. Single-screw extruders with screw diameters from 60 mm to 120 mm and length-to-diameter ratios of 28:1 to 36:1 are standard in this segment. Barrel zones are typically set from 210 °C at the feed throat to 250 °C at the die head. The quench bath is maintained between 30 °C and 45 °C to stabilise the mesomorphic or α-crystalline structure before orientation. Orientation ovens are operated from 130 °C to 145 °C, with machine-direction draw ratios between 1:5 and 1:8 to develop tensile strength in the tape. Processing outside this window typically manifests as fibrillation, irregular film edges, or reduced tenacity on circular looms.

Melt Rheology, Screw Torque, and Extrusion Melt Pressure

Because the nominal melt flow rate is near 3.0 g/10 min, the melt exhibits higher shear viscosity than high-flow spunbond grades having MFR of 25 g/10 min to 40 g/10 min. The higher viscosity is deliberate: it supplies the melt strength required for hot stretching and reduces draw resonance. On a 90 mm single-screw extruder with L/D 30:1, typical clean-screen die pressure for homopolymer PP tape lines is in the 8 MPa to 15 MPa range; a blocked screen pack or undersized melt pump can raise head pressure above 25 MPa, increasing back-pressure and polymer residence time. Melt temperature must be kept below 260 °C for continuous operation because thermo-oxidative chain scission accelerates rapidly above this threshold, producing MFR drift, yellowing, and reduced tape tenacity. Capillary rheometry under ISO 11443 is the appropriate method to obtain viscosity data for new die geometries or screen-pack arrangements. Published data for this specific grade in capillary rheometry is limited; however, the processing behaviour is consistent with homopolymer polypropylene of equivalent MFR.

Melt filtration is commonly performed with screen packs of 60 mesh to 100 mesh. Finer filtration increases head pressure and shear heating but reduces particulate defects in thin tapes. The screw should be inspected for wear in the feed and metering zones because polymer melt leakage across worn flights widens residence time distribution and creates gel formation. Moisture analysis under ISO 15512 or Karl Fischer titration should be used when condensation is suspected on stored pellets. The resin’s low moisture uptake does not remove the need for inspection of regrind, which may carry soap residue from washing lines or calcium carbonate from filler masterbatch. These contaminants reduce melt-pressure stability and can cause screen-pack blockage during long runs.

In oriented tape production, the melt is quenched into a cast film before heated draw. Differential scanning calorimetry under ISO 11357-3 may show a shift in crystalline melting behaviour as draw ratio increases. Low draw ratios below 1:4 yield lower tensile strength and higher elongation at break; draw ratios above 1:9 promote fibrillation and thickness variability. On high-speed lines, draw resonance must be controlled by adjusting die gap and melt temperature rather than by changing only draw ratio. The grade’s higher melt viscosity relative to random copolymer makes it easier to stabilise a uniform web at line speeds above 200 m/min, but it also narrows the temperature window before orientation.

Does the Homopolymer Backbone Trigger Low-Temperature Impact Loss?

Impact behaviour is the main operational boundary. Without ethylene comonomer, KUNLUN PP S1003 retains high flexural modulus but exhibits a sharper ductile-to-brittle transition than random copolymers. Notched Charpy impact strength at 23 °C under ISO 179-1/1eA is typically reported between 2.0 kJ/m² and 4.5 kJ/m² for injection-moulded specimens. At 0 °C, the same test frequently falls below 1.5 kJ/m². At -20 °C, fracture is predominantly brittle, which rules out unmodified use in freezer containers or cold-chain packaging. Flexural modulus, in contrast, is usually reported from 1,350 MPa to 1,550 MPa under ISO 178. This combination of high modulus and limited low-temperature impact explains why the grade is selected for oriented tape, rigid household articles, and general-purpose injection moulding rather than for sub-zero service. If low-temperature toughness is required, an impact copolymer or elastomer-modified compound should be selected; if clarity and moderate toughness suffice, a random copolymer with ethylene content up to 4 wt% can be used.

Woven sack tape produced from S1003 typically exhibits oriented-direction tensile strength between 25 MPa and 35 MPa when measured by ISO 527-3 or ASTM D882, depending on draw ratio and tape thickness. Tapes of 2 mm width and 30 μm thickness are standard substrates for circular loom conversion. Winding tension after orientation must be controlled because excessive tension accelerates stress relaxation and can reduce effective tenacity during weaving. For outdoor sacks or flexible intermediate bulk containers, UV stabiliser masterbatch at 2.0 wt% to 3.5 wt% is incorporated; unmodified homopolymer undergoes chain scission and surface embrittlement under prolonged sunlight. Weathering performance should be verified under ISO 4892-2 or ASTM G154, not inferred from short-term appearance. Carbon black dispersion in masterbatch should be checked by ISO 11420 or equivalent microscopy to prevent agglomerates that initiate splitting.

When S1003 Is Substituted for Random Copolymer in Thin-Wall Injection Moulding

Injection moulding trials using KUNLUN PP S1003 in place of random copolymer must address shrinkage anisotropy and warpage. Mould shrinkage parallel to flow is commonly 1.4 % to 1.8 %, while transverse shrinkage is 1.2 % to 1.6 % under ISO 294-4, depending on packing pressure, gate geometry, and mould temperature. The differential between flow and transverse directions is typically larger in homopolymer than in random copolymer, increasing the risk of warp in flat lids and rectangular containers. Mould temperature is normally held between 30 °C and 60 °C; higher mould temperatures raise crystallinity and increase static modulus but extend cycle time. Melt temperature should be kept within 220 °C to 250 °C. On a 200 t injection moulding machine, thin-wall containers with flow length/wall thickness ratios above 180:1 may require melt temperature near the upper bound of that range; this should not be combined with hot runner residence time above 10 min. Gate dimensions, not resin grade alone, dominate pressure-limited filling in such moulds.

Clamp force should be calculated from cavity pressure and projected area rather than from resin density alone. Homopolymer grades such as S1003 can generate higher cavity pressure than random copolymers at the same melt temperature because of higher viscosity. Packing pressure profiles should be adjusted to minimise overpacking near the gate, which worsens shrinkage anisotropy and part warpage. Hot runner systems with long flow paths require temperature profiling to avoid dead zones where thermo-oxidative degradation can form gels that appear as surface defects in the final part.

Reading the Data Matrix: Homopolymer Versus Random Copolymer

The table below compares nominal literature values for homopolymer S1003 with a typical random copolymer benchmark. Values are representative ranges, not lot guarantees; the certificate of analysis for the specific batch governs.

The high-flow homopolymer grades used in spunbond or meltblown processes have MFR values from 25 g/10 min to 40 g/10 min. KUNLUN PP S1003 is not suitable for those processes because its lower MFR restricts capillary throughput unless melt temperature is raised to levels that risk chain scission. Conversely, in cast film and oriented tape processes, high-flow grades create draw instability and lower tape modulus. The grade therefore occupies a processing band with adequate flow for thick-section and oriented applications but insufficient flow for micro denier fibre spinning. Differences from random copolymer are most pronounced in optical clarity, low-temperature impact, and flexural modulus; copolymers provide better clarity and toughness, while S1003 provides higher stiffness and better melt strength during hot draw.

Regulatory conformity must be assessed on the final article, not on the pellet alone. Because the product is a halogen-free polypropylene homopolymer, RoHS Directive 2011/65/EU and REACH Annex XVII restrictions are typically satisfied from composition, but converters must obtain final-article verification. Food-contact suitability is not automatic; the finished article must be tested under EU 10/2011, GB 4806.7-2016, or FDA 21 CFR 177.1520, with attention to additive migration and overall migration limits. No phthalate plasticisers or brominated flame retardants are intrinsic to the grade.

Storage and handling boundaries are straightforward. At relative humidity below 60 %, no predrying is required. If bags are stored outdoors or condensation is observed, drying should be applied at 70 °C to 80 °C for 1 h to 2 h. Avoid contact with copper-based stabilisers, iron oxide, or strong acids because transition metals and acid residues accelerate thermo-oxidative degradation. Hindered amine light stabilisers and phenolic antioxidants are generally compatible, but additive interactions with catalyst residues are lot-dependent; published data for this specific additive package is limited.