PVC Resin HS-1000F(SG-5)

Commercial suspension-polymerised poly(vinyl chloride) resin designated HS-1000F (SG-5) is supplied as a white powder for rigid compounding and extrusion processes. The resin occupies the intermediate molecular-mass range within the GB/T 5761-2006 classification, with a typical K-value of 66–68 and an average degree of polymerisation near 1000–1100. This molecular architecture balances melt viscosity, fusion efficiency, and tensile requirements in rigid PVC-U profiles, pressure pipes, and injection-moulded fittings. In contrast to SG-3 resins with higher K-values and to SG-7/SG-8 resins with lower K-values, HS-1000F (SG-5) is selected when extrusion melt strength must be maintained without sacrificing the angular flowability required for medium-shear processing. The grade is not a copolymer, emulsion resin, or mass-polymerised material; it is a suspension homopolymer with a defined grain porosity that controls plasticizer absorption and dry-blend behaviour.

What Is the Specification Envelope of HS-1000F (SG-5) When Tested Under GB/T 5761-2006?

Contract specifications for HS-1000F (SG-5) generally fall within the following envelope. The K-value determined on the cyclohexanone-soluble fraction is reported as 66–68 under ISO 1628-2:2020, which corresponds to the SG-5 band under GB/T 5761-2006. Apparent bulk density under ISO 60:1977 is commonly specified as 0.48–0.54 g/cm³, while the residue on a 250 µm sieve is maintained below 2% to prevent dry-blend inhomogeneity in high-speed mixers. Volatile matter, determined by heating at 110 °C for 2 h, is limited to ≤0.30%. Plasticizer absorption of the resin, measured with dioctyl phthalate under GB/T 3400-2002 or equivalent producer methods, typically lies between 20–26 g/100 g, reflecting intermediate grain porosity. Residual vinyl chloride monomer is controlled to ≤1 µg/g in food-contact and potable-water grades, which is required when compliance with GB 4806.6-2016 or EU Regulation 10/2011 is declared. Whiteness index is routinely specified at ≥80 on the Hunter scale, though published producer datasheets for HS-1000F may show values in the 82–86 range.

Where contract requirements deviate from these values, the limiting variables are usually plasticizer absorption and sieve residue rather than K-value alone. A batch with plasticizer absorption at the upper limit of 26 g/100 g can produce earlier gelation in rigid dry blends because the porous grain structure absorbs liquid stabilizer and lubricant more rapidly, shifting torque rise toward the feed zone of a twin-screw extruder. Conversely, a batch near 20 g/100 g may require higher processing temperatures to achieve the same degree of fusion, particularly in formulations with low tin-stabilizer levels.

In rigid pipe and profile operations, HS-1000F (SG-5) is typically preblended in a vertical high-speed mixer operated at 900–1200 rpm. The dry blend is discharged at 110–125 °C and cooled to 40–45 °C before storage. This thermal history permits the outer grain layers to absorb liquid stabilizers and lubricants without premature fusion. Production-scale observations on counter-rotating twin-screw extruders with L/D 25:1 and 35 mm screw diameter show that blend bulk density below 0.46 g/cm³ can cause feed fluctuation and output variation of 3–5%. In contrast, blends above 0.56 g/cm³ may compact in the feed throat and increase motor load by 8–12% depending on screw geometry and barrel temperature profile. These boundaries define the practical operating window for the resin on standard rigid PVC extrusion lines.

Fusion Kinetics in Counter-Rotating Twin-Screw Extrusion

Fusion behaviour of HS-1000F (SG-5) is assessed through torque rheometry using a mixer head equipped with roller rotors at 190 °C and 35 rpm. Under these conditions, the time to fusion peak for a lead-stabilized rigid pipe formulation is commonly observed between 90–150 s, with a peak torque of 18–25 N·m. These values depend on grain porosity, filler type, stabilizer chemistry, and lubricant balance. When calcium carbonate filler content is increased from 10 phr to 30 phr, the fusion peak shifts later by 15–30 s because the non-melting filler particles disrupt the breakdown of PVC primary particles. For HS-1000F (SG-5) specifically, the intermediate K-value provides sufficient molecular entanglement to maintain a stable melt film on the barrel wall, but it does not generate the high torque peaks associated with SG-3 resins.

On a twin-screw extruder, the recommended barrel temperature profile for rigid pipe production is typically 170 °C in zone 1, 180 °C in zone 2, 190 °C in zone 3, and 195 °C at the die head. Screw oil temperature is controlled at 150–170 °C to prevent overheating in the screw core. At melt temperatures above 205 °C, the rate of dehydrochlorination accelerates sharply, leading to yellowing, surface roughness, and reduced impact strength. Published data for this specific configuration is limited, but industrial practice indicates that a melt temperature of 195–200 °C is the upper safe range for continuous runs exceeding 12 h with HS-1000F (SG-5) and an appropriate Ca/Zn stabilizer system. The resin should not be processed in formulations using high-zinc stabilizer packs without co-stabilizers, because zinc-induced degradation can generate black specks at temperatures as low as 190 °C.

Moisture absorption by the resin is normally low, but storage at relative humidity above 60% can introduce free moisture that appears as surface defects during extrusion. Pre-drying at 80 °C for 2–3 h is recommended when the resin has been stored in unlined bags or exposed to condensation. The resin is incompatible with strong amine-based additives that can accelerate dehydrochlorination at processing temperatures. It is also not recommended for plastisol processing because suspension-polymerised resins do not disperse in liquid plasticizer in the manner required for paste-grade PVC produced by emulsion or micro-suspension polymerisation. This limitation separates HS-1000F (SG-5) from paste resins and from mass-polymerised suspension grades with different grain morphology.

In injection moulding of small-diameter pipe fittings, HS-1000F (SG-5) is processed at melt temperatures of 190–200 °C with injection pressures between 80–120 MPa. The lower K-value of the resin compared to SG-3 permits faster filling of thin-wall cavities, but the higher melt viscosity compared to SG-7 or SG-8 reduces the incidence of flash and improves pressure retention during packing. Field data from production lines using single-screw injection machines with 45 mm screw diameter indicate that cycle-time reductions of 6–10% can be achieved when switching from SG-3 to HS-1000F (SG-5) in fittings with wall thickness below 3 mm, although this benefit is formulation-dependent and should not be generalised without rheological testing.

When Substitution of SG-3 Becomes Feasible in High-Fill Rigid Pipe Formulations

SG-3 resin, with a typical K-value of 71–72 and average degree of polymerisation near 1300–1350, provides higher tensile strength and improved creep resistance in large-diameter pressure pipes, but it requires higher processing temperatures and increases shear heating. Substitution by HS-1000F (SG-5) becomes technically feasible when the pipe wall thickness is below 10 mm and the filler content does not exceed 30 phr calcium carbonate. At filler loadings above 30 phr, the lower molecular weight of SG-5 may reduce the melt strength needed to support the extrudate during calibration, resulting in sagging or dimensional variability. In such cases, SG-3 or a blend of SG-3 with SG-5 is preferred.

Compared to SG-7 and SG-8, which exhibit K-values of 60–62 and 57–59 respectively, HS-1000F (SG-5) has a broader processing window for rigid pipe extrusion. SG-7 and SG-8 resins fuse more easily and are suitable for complex injection-moulded articles and high-output thin-wall profiles, but they may show lower notched impact strength in thick rigid sections. The selection of HS-1000F (SG-5) is therefore driven by a balance between fusion rate, impact performance, and final product stiffness. Mechanical testing according to ASTM D638-14 for tensile properties and ISO 179-1:2010 for Charpy impact strength is required to confirm that the grade change does not compromise the product specification. Published comparative data for HS-1000F specifically is limited; therefore, each formulation change must be validated on the target production line.

Batch-to-batch variation in HS-1000F (SG-5) can be detected by monitoring plasticizer absorption and dry-blend bulk density before extrusion. A shift of ±1.5 g/100 g in plasticizer absorption has been reported on some production lines to move gelation onset by 3–5 °C in torque rheometry. This effect is amplified in low-lubricant formulations where the resin grain structure controls the distribution of liquid stabilizers. Incoming inspection should therefore include a rapid plasticizer absorption test because K-value alone does not capture porosity differences. If the value falls outside the agreed range, feed rate or barrel temperature adjustments are required before continuous extrusion is attempted.

Assessing Dry-Blend Flowability Through Conical Hopper Discharge

Dry-blend flowability is not an intrinsic resin property but emerges from the interaction between resin grain size distribution, lubricant type, and mixer discharge temperature. In a conical hopper with discharge orifice diameters between 25–40 mm, dry blends based on HS-1000F (SG-5) typically flow without bridging when the blend bulk density exceeds 0.48 g/cm³ and the moisture content remains below 0.20%. Below this bulk density, funnel flow can develop, causing bridging over the extruder feed throat and output variation. The use of external lubricants such as polyethylene wax at 0.1–0.3 phr improves hopper discharge but may delay fusion if over-dosed. In production-scale extrusion of rigid pipe, bridging at the feed throat is a primary failure mode when the dry blend is discharged from the mixer at temperatures above 125 °C and then stored in humid conditions. Cooling to 40–45 °C before storage reduces condensation and maintains consistent flow.

For rigid window profile formulations, HS-1000F (SG-5) is combined with impact modifiers, titanium dioxide, calcium carbonate, and stabilizers. The resin content is typically 55–65 phr of the total formulation, with the balance comprising additives. Under these conditions, the resin contributes to both the gelation behaviour and the final weather resistance of the profile. Outdoor exposure testing according to ISO 105-A02:1993 and colour change measurement according to ASTM D2244-23 are applied to verify that the selected grade does not cause unacceptable yellowing. High residual iron or chloride levels in the resin can accelerate photo-oxidative degradation, so resin purity is monitored through ash content, typically limited to ≤0.10%.

In high-speed extrusion of corrugated pipe, HS-1000F (SG-5) is selected over SG-7 when wall compression strength and ring stiffness must be maintained. The higher K-value of SG-5 increases melt strength and allows the corrugator to form uniform bellows without cracking. At line speeds above 15 m/min, the limiting factor is often the fusion rate rather than output capacity. Torque rheometry data is used to set the screw temperature and screw speed so that the degree of fusion reaches 65–75% before the material enters the corrugator. Below 60% fusion, the formed pipe may show poor impact strength and surface delamination. Above 80% fusion, the melt may become too homogeneous and lose the memory needed for corrugation stability.

Published data for this specific configuration is limited, but the processing boundaries stated here are consistent with industrial practice for intermediate K-value suspension PVC resins. HS-1000F (SG-5) is not suitable for plasticized applications requiring high plasticizer absorption because its grain porosity is lower than that of paste-grade resins. It should also not be used in applications requiring the highest impact resistance in thick sections without adding impact modifiers, because the base resin alone has notched Charpy impact values that may fall below 5 kJ/m² at 23 °C depending on formulation and test specimen preparation. In fibreglass-reinforced or high-temperature environments, alternative materials or higher molecular weight PVC grades are typically considered.