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Zhejiang Shenghui New Materials Co., Ltd

Processors that incorporate Zhejiang Shenghui New Materials Co., Ltd. chlorinated polyethylene impact modifier into rigid PVC profiles often qualify the material through an incoming powder inspection that includes bulk density, volatile content, chlorine content, and residual crystallinity. The bulk density of a commercial 35 wt% chlorine CPE powder is typically 0.45–0.55 g/cm³; deviations outside this band alter gravimetric screw feeder output and shift local concentration in the dry blend. The powder is introduced into a high-intensity hot/cold mixing line where PVC resin, stabilizer, stearic acid, paraffin wax, titanium dioxide, and calcium carbonate are first heated to 85–90 °C. CPE is added after the PVC has absorbed the liquid stabilizer but before the lubricant system is fully melted, because early addition can encapsulate calcium carbonate and delay fusion, while late addition produces local impact-modifier-rich domains. The hot mixer is discharged at 112–118 °C; if the premix is cooled below 105 °C before complete absorption, the residual volatiles exceed 0.2 wt% and cause silver streaks in the extruded profile. On a conical twin-screw extruder with screw diameter 65/132 mm and L/D 27, compound containing 6–10 phr CPE is processed at barrel temperatures of 170–195 °C from feed to metering, with adapter temperature 190–200 °C and die zones 195–205 °C. Melt pressure at the breaker plate is maintained between 14 and 20 MPa, screw torque between 60 and 78%, and specific mechanical energy input between 0.12 and 0.18 kWh/kg. The calibration deck vacuum is held at −0.075 to −0.090 MPa; insufficient vacuum fails to remove moisture and decomposition gases, while excessive vacuum collapses thin internal walls in multi-chamber profiles. The thermal history constraint is severe: stock temperature at the die entrance above 208 °C for more than 90 s initiates autocatalytic dehydrochlorination, reduces notched Charpy by 20–40%, and shifts colour below the typical L* 78–82 range. Qualification of window profiles requires profile impact resistance evaluation according to EN 12608-1, tensile properties according to ISO 527-2, notched Charpy impact at 23 °C and −10 °C according to ISO 179-1, and Vicat softening temperature according to ISO 306 method B50. Published line data for this specific supplier’s resin in high-speed profile extrusion is limited; the equipment and test envelope described here derives from standard PVC-U processing references and comparable 35 wt% chlorine CPE systems. Before a new lot is charged into a production campaign, residual crystallinity is typically screened by differential scanning calorimetry at a heating rate of 10 K/min because crystallite content in the 2–10% range controls dispersion rate and low-temperature impact efficiency. A lot exhibiting residual crystallinity above 10% may require a higher plasticizer-free mixing temperature to break up crystalline domains, but the stabilizer system must then be adjusted to compensate for the extended shear exposure. Sieve residue on a 45 µm screen is held below 1.0 wt%; oversized particles that survive dry blending create visible fisheyes in dark brown profiles and can obstruct fine screen packs used in coextrusion. Moisture content is controlled to 0.3 wt% maximum by drying at 100 °C for 2 h. When calcium carbonate is present at more than 8 phr, as is common in foam-board or low-cost profile production, the mixing sequence must be altered so that the filler is added before the CPE, otherwise the impact modifier binds to the calcium stearate and produces dry blend segregation. The compound is then aged in an insulated silo for 4–8 h at 40–50 °C to equilibrate moisture and allow lubricant migration; direct extrusion of freshly mixed compound can shift fusion time and cause die lip deposit within the first 30 min of the run.

What Restricts CPE Loading in Pressure Pipe Compounds?

In pressure pipe compounding, chlorinated polyethylene addition is constrained by the competing requirements of ductile failure resistance and long-term hydrostatic pressure retention. Zhejiang Shenghui New Materials Co., Ltd. CPE grades used in PVC-U pipe are often incorporated at 2–6 phr; below 2 phr, notched Charpy at 0 °C can fall below 4 kJ/m², raising brittle fracture probability in DN 110–DN 400 pipes installed in poorly bedded trenches. Above 6 phr, the reduction in long-range stiffness lowers the 50-year hydrostatic strength extrapolated by ISO 9080, because creep rate increases under sustained hoop stress. In parallel counter-rotating twin-screw pipe extrusion with screw diameter 80–130 mm and L/D 26–36, increasing CPE from 3 phr to 7 phr is often accompanied by a barrel torque increase of 4–8% and a slight melt pressure rise at the screen pack, but the more significant constraint is the drop in Vicat softening temperature and socket dimensional stability. Insertion of 8 phr CPE lowers the compound Vicat B50 into the 74–76 °C range; depending on pipe wall thickness and service classification, this approaches the minimum acceptance value used in ISO 1452-2 for water supply piping. Published data for a comparable 35 wt% chlorine CPE in rigid PVC show a non-linear impact response: the notched Charpy gain per phr is strongest between 2 and 6 phr, then levels off while modulus and Vicat decline almost linearly. The processing window is also narrowed by the filler response. CPE particles reduce fusion time, but when calcium carbonate is present above 8 phr, the pre-fusion torque peak may broaden and shift to lower temperature, producing an apparently homogeneous dry blend that is actually under-fused at the wall. The following table compiles the reported property response envelope for comparable CPE-modified rigid PVC compounds used in pipe and profile screening. It is not a single-lot certificate.
CPE Addition Notched Charpy at 23 °C Tensile Yield Stress Flexural Modulus Vicat B50
0 phr 6–10 kJ/m² 50–55 MPa 2900–3200 MPa 80–84 °C
4 phr 15–25 kJ/m² 46–50 MPa 2600–2800 MPa 79–82 °C
8 phr 30–45 kJ/m² 40–44 MPa 2200–2400 MPa 75–78 °C
12 phr 50–70 kJ/m² 34–38 MPa 1800–2100 MPa 70–74 °C
Because pipe pressure ratings depend on measured wall thickness, density, and hydrostatic design stress according to ISO 1452-2, the compounder must verify that CPE addition does not reduce pipe stiffness below the ring stiffness demanded by ISO 9969 for buried installations. At a CPE loading above 6 phr, ring stiffness in a 110 mm outer-diameter pipe with 3.2 mm wall thickness can drop by 5–10%, which is significant when the pipe is specified for SN8 or SN16 service. In pressure pipe, gelation must also be assessed by methylene chloride immersion according to ISO 9852 or an equivalent production-control method; CPE-rich domains that are not fully fused appear as swollen regions and may initiate premature crack growth under sustained internal pressure. A specific incompatibility is the combination of high CPE content with high levels of external lubricant, because the softened lubricant layer can delay inter-particle fusion in the metering zone and leave a sandwich structure in pipe walls thicker than 10 mm. Compounding the same CPE-modified dry blend for injection moulded PVC-U fittings requires a different set of thermal and shear controls because the material path from nozzle to cavity is shorter but local shear rates are higher than in profile extrusion. A moulding machine with clamp force between 1200 and 3000 kN is usually selected for 50–160 mm diameter fittings; barrel zones are set from 165 °C at the feed throat to 190 °C at the nozzle, and screw backpressure is held at 0.6–1.2 MPa to maintain a homogeneous melt with minimal frictional heat. The presence of CPE at 4–8 phr increases melt strength but also increases the tendency for gate blush at the transition from sprue to cavity when injection speed exceeds 80 cm³/s; the remedy is to enlarge the gate land and reduce fill time, but cycles longer than 60 s risk thermal degradation in the barrel. Holding pressure is maintained at 60–70% of injection peak pressure, and mould temperature is controlled at 30–50 °C to prevent sink marks and to preserve notch resistance in the finished fitting. Qualification of fittings is performed under ISO 1452-3 for water supply joints and ISO 580 for dimensions; hydrostatic resistance is confirmed at 20 °C for 1 h and at 60 °C for 1000 h according to the applicable system standard. A specific operational boundary is that CPE addition should not exceed 6 phr when the fitting contains brass inserts, because the higher thermal expansion differential and reduced modulus can cause insert loosening after thermal cycling between −5 and 60 °C.

Anticorrosive Coating Resin Solubility and Film Formation Parameters

Zhejiang Shenghui New Materials Co., Ltd. high-chlorine chlorinated polyethylene and chlorinated polypropylene resins are evaluated in anticorrosive coatings by solution viscosity, solvent release, and intercoat adhesion on blasted carbon steel. The resin is usually solvated in a xylene/butyl acetate mixture at 20–25 wt% solids; solution viscosity measured by ISO 2884-1 at 23 °C ranges from 150 to 300 s on a Ford cup No. 4, depending on resin chlorine content and molecular weight. Film build of 40–60 µm dry film thickness is applied in two passes by air spray; forced drying at 60 °C for 30 min removes most retained solvent, but residual xylene above 0.5% in the dried film causes blistering under salt spray. The anticorrosive performance is evaluated with ISO 9227 neutral salt spray for 500–1000 h and the coating is rated for rust and blistering according to ISO 4628-2 and ISO 4628-3; adhesion on steel surfaces prepared to Sa 2½ according to ISO 8501-1 is tested by ASTM D3359 cross-cut procedure. Chlorinated polypropylene in the same product class functions as a primer or midcoat adhesion promoter for polypropylene films and thermoplastic olefin substrates; its solvent-borne film has a surface energy after corona treatment of 38–42 mN/m and is applied at 3–8 µm dry film thickness. The principal incompatibility occurs with long-oil alkyds and zinc-rich fillers where free zinc ions accelerate dehydrochlorination of the chlorinated resin and cause gelation within 48–96 h at 40 °C; these formulations are avoided unless sufficient epoxide scavenger is present. Compliance touchpoints include REACH Article 33 declarations for residual chlorinated paraffins below 0.1 wt% and RoHS Directive 2011/65/EU for total lead below 0.1 wt%. When a solvent-borne anticorrosive primer is applied to a cold substrate below 5 °C, the evaporation rate of the xylene slows enough to cause intercoat trapping and loss of topcoat adhesion after 24 h of ambient cure. In high-humidity conditions above 70% relative humidity, the chlorinated resin film absorbs water at the air interface and may blush; film hardness measured by ASTM D3363 pencil methods can then drop by 1–2 pencil grades. Atmospheric exposure testing is commonly supplemented by electrochemical impedance spectroscopy at 0.01 Hz to monitor barrier resistance; a sound 60 µm film maintained above 10⁶ ohm·cm² after 1000 h of ISO 9227 exposure is generally considered effective barrier protection. The maximum practical service temperature for chlorinated polyethylene coating resins in dry environments is typically below 80 °C; at temperatures above 100 °C, dehydrochlorination can discolour the film and reduce adhesion. When chlorinated polypropylene is used in gravure printing inks on biaxially oriented polypropylene film, the ink must be applied within 48 h of corona discharge because surface energy decays from 42 mN/m to below 34 mN/m and ink wetting becomes non-uniform.

When Chlorinated Polyethylene Elastomer Is Compounded for Oil-Resistant Cable Jacketing

Formulation of Zhejiang Shenghui New Materials Co., Ltd. CPE elastomer in cable jackets is conducted in an internal mixer with intermeshing rotors, a fill factor of 0.70–0.80, and ram pressure between 0.5 and 0.8 MPa. The polymer, stearic acid, magnesium oxide, carbon black, plasticizer, and filler are charged first; the peroxide curing agent is withheld until a second mixing stage at 95–105 °C to avoid scorch. Dicumyl peroxide addition at 3–5 phr and triallyl isocyanurate at 1.5–2.5 phr gives a cure time tc90 of 8–14 min at 165 °C on an oscillating disc rheometer according to ISO 6502. The unvulcanized compound has a Mooney viscosity ML 1+4 at 100 °C of 65–85, which provides adequate collapse resistance in thin-wall extrusion but requires barrel temperatures below 90 °C when using a cold-feed extruder with an L/D of 20–24. Extrusion head temperature is set at 105–120 °C, and the premix is dried to 0.2 wt% moisture maximum before use because water reacts with the peroxide and causes porosity. Vulcanized jackets are tested for tensile strength and elongation according to IEC 60811-501 or ASTM D412, heat ageing at 121 °C for 168 h according to IEC 60811-401, mineral oil resistance according to ISO 1817, and flammability by limiting oxygen index according to ISO 4589-2. A critical processing boundary is the crosslinking temperature window: below 160 °C the cure is incomplete and the jacket retains low hot-set modulus; above 190 °C the chlorinated polyethylene can liberate hydrogen chloride and produce voids at the insulation interface. The compound is incompatible with amine-based antiozonants, which can accelerate dehydrochlorination; mineral fillers with free moisture above 0.3 wt% also reduce the crosslink density by consuming radical cure species. Systematic compliance verification for these CPE-based compounds across profile, coating, and cable applications is summarized in the following matrix.
Property or Compliance Dimension Standard or Regulation Typical Acceptance Boundary
Chlorine content of CPE ISO 1159 or coulometry 35 ± 1 wt% for impact-modifier grade; 62–65 wt% for coating grade
Volatile content ISO 1269 ≤ 0.3% after 100 °C/2 h
Notched Charpy impact ISO 179-1 ≥ 20 kJ/m² at 23 °C for profile compound; ≥ 4 kJ/m² at 0 °C for pipe compound
Vicat softening temperature ISO 306 B50 ≥ 75 °C for profile; pipe system minimum per ISO 1452-2
Flammability of cable jacket ISO 4589-2 Limiting oxygen index ≥ 26%
REACH SVHC declaration EC 1907/2006, Article 33 Substances of very high concern < 0.1 wt%
RoHS total lead Directive 2011/65/EU ≤ 0.1 wt%
Fred Wang

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