How to produce PVC flexible hose tube by using PVC granules ?

I. Common Types of PVC Flexible Hoses

Hoses are classified by structure, reinforcement, and application:

II. Production Process Using PVC Granules

(Twin-Screw Extrusion is most common)

1.Material Handling: 

. PVC granules are fed from silos into the extruder hopper.

. Critical: Granules must be dry (moisture < 0.3%). Pre-drying at 60-80°C for 1-2 hrs may be needed.

2.Extrusion: 

. Granules enter the extruder barrel with rotating screws.

. Zones are heated progressively (typically 150°C – 190°C).

. PVC melts into a homogeneous, viscous melt through shear heat and conduction.

3.Tooling (Die Head):

. Melt is forced through a die that shapes the hose’s inner diameter (ID).

. For reinforced hoses: Braiding/spiraling occurs immediately after the inner tube extrusion.

4.Reinforcement Application (if applicable):

. Braiding: Yarns (polyester, nylon, aramid) cross-weave over the inner tube.

. Spiraling: Steel/plastic wire is wound onto the tube.

5.Outer Layer Extrusion (Co-Extrusion):

. A second extruder applies the outer layer over the reinforcement.

. Requires precise adhesion control between layers.

6.Cooling & Sizing:

. Hose enters a vacuum sizing tank or water bath to solidify.

. Calibrated sleeves maintain precise outer diameter (OD).

. Cooling must be gradual to prevent stress or distortion.

7.Printing & Marking:

. Hot-stamp printing or ink-jet printers apply branding/specs.

8.Pulling & Coiling:

. Pullers maintain tension at controlled speed.

. Hoses are coiled or cut to length.

9.Post-Processing (Optional):

. End Fitting Attachment: Crimped connectors.

. Sterilization: For medical hoses (e.g., ethylene oxide, gamma).

Key Process Parameters

Screw Design: L/D ratio (20:1 to 30:1), compression ratio (2.5:1 to 3.5:1)

Temperature Profile: Must match granule formulation (plasticizer type, stabilizers)

Melt Pressure: 150-350 bar (monitored to prevent degradation)

Screw Speed: RPM optimized for output vs. mixing quality

Vacuum/Cooling Control: Prevents bubbles, ensures dimensional stability

Critical Quality Control Points

Granule Consistency: Melt flow index (MFI), plasticizer content

Dimensions: ID/OD tolerances (±0.1mm typical)

Physical Properties: Tensile strength, elongation, burst pressure

Surface Quality: Smoothness, absence of gels/sharkskin

Adhesion: Layer bonding (peel tests for multi-layer hoses)

Regulatory Compliance: Certifications (NSF, FDA, REACH)

Common PVC Hose Defects & Causes

Pro Tip: Optimize granule formulation for:

. Processability: Lubricant balance prevents screw slippage.

. Low-Temp Flexibility: Choose plasticizers like DINP/DOTP for cold climates.

. Extraction Resistance: Use polymer-grade plasticizers in chemical hoses.

Need help troubleshooting a specific production issue or formulating granules for a hose type? INPVC technical team can provide deeper technical guidance.