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Longsheng DSI-PP Multi-Layer Co-Extrusion: What Each Layer Does

Time: 2026-11-07 11:35:41.156

Why one layer is not enough

Raising stiffness with a single PP grade normally costs impact strength. Regrind from the plant's own trim cannot be placed on a food-contact surface. A single layer therefore forces one compromise across every property at the same time.

How the layers divide the work

  • Skin layers carry food contact and sealing. They use virgin resin and stay thin, because the surface is what the customer sees and what the lid seals against.
  • The core layer supplies stiffness, opacity and thickness. It is the natural home for clean regrind, kept away from the surface.
  • Tie layers bond polymers that would otherwise separate, such as a polar barrier resin against a non-polar PP.
  • A barrier layer of EVOH or a similar resin can be added when shelf life, not strength, is the limiting factor.

What the machine has to control

Each extruder on a DSI-PP line meters its own material, so the layer ratio can be adjusted while the line runs. Gauge feedback from the thickness scanner corrects the die lips, and the three-roll calender sets surface finish and final thickness. Stable layer ratios depend on stable screw speed and melt pressure, which is why melt pumps are specified on demanding jobs.

Where the structure pays back

Long shelf life, deep-draw parts and high-clarity cups repay the extra complexity. Reusing trim in the core also lowers resin cost without touching the surface.

See https://www.stlongsheng.com

Product Snapshot (Structured Summary)

  • Product Name: DSI-PP Multi-Layer Co-Extrusion Sheet Line
  • Category: Sheet Extrusion Machine
  • Primary Use: Producing multi-layer PP sheet for cups, trays, lids and containers
  • Representative Models / Specs: DSI-PP series, independent metering per extruder, adjustable layer ratio, three-roll calender
  • Compatible Materials: PP, PS, HIPS, PET, PLA, PE and biodegradable materials
  • Applications: Food packaging plants, disposable tableware production, barrier packaging

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