SJ-30/28 Plastic Co-Extrusion Single Screw Laboratory Extruder — Build and Verify Multilayer Structures on a Lab Scale

Multilayer Products Start with Proven Co-Extrusion on a Lab Scale

Multilayer plastic products — a co-extruded pipe with a protective cap layer, a sheet with a functional skin, a profile with a colored surface over a recycled core — are the most demanding products in extrusion. They fail in ways single-layer products never do: poor layer adhesion, uneven thickness distribution, incompatible melt temperatures, and interfacial flow instability. And the worst place to discover those problems is on a production-scale line, where one bad trial consumes tonnes of material and days of production time.

That is the gap the Chenxing SJ-30/28 Plastic Co-Extrusion Single Screw Laboratory Extruder Machine is engineered to close. It is a laboratory-scale co-extrusion extruder built for thermoplastics such as PVC, PE, PS, PA, POM, and PMMA — supporting co-extrusion experiments, product development, and multilayer structure sampling. Before a multilayer structure is committed to a production die, it is verified here: layer materials are tested for compatibility, melt flow is balanced, and the structure is proven at a material cost measured in kilograms.

The machine is built on the same core structures as the Chenxing laboratory extruder family — a 38CrMoALA nitrided screw, a heated head flange joint, and a variable frequency transmission system — with one defining difference: the screw, barrel, and drive are specified for co-extrusion duty, with L/D and compression ratio customized to the raw material. According to different raw materials, the screw design has a different aspect ratio and compression ratio, and the barrel adopts a different structure. The appropriate barrel, screw, and drive mechanism are selected together to meet the needs of high-quality product processing.

SJ-30/28 Plastic Co-Extrusion Laboratory Extruder — Key Specifications

The SJ-30/28 is the co-extrusion specialist of the Chenxing laboratory range. Its verified parameters:

Parameters not listed above — heating power, co-extrusion layer count, center height, machine dimensions, weight, inverter brand, and temperature control accuracy — are customized to the co-extrusion project and are available on request from the Chenxing engineering team.

The Chenxing Laboratory Co-Extrusion Series — Selection Table

The SJ-30/28 belongs to a laboratory extruder series that spans compact single-layer work to higher-capacity co-extrusion duty:

The SJ-30/28 at the center of this range is the natural co-extrusion platform: large enough to carry a realistic multilayer melt through the die, small enough to keep every trial economical. For higher-capacity co-extrusion research, the SJ-35 compact configuration and the SJ-45 extend the range on request.

How the Co-Extrusion Laboratory Extruder Works

The SJ-30/28 is a complete co-extrusion single screw system in three core structures — the same engineering architecture as the Chenxing laboratory range, configured for multilayer duty.

Structure 1 — The Screw 

The screw is the key component for the transportation and plasticization of plastics. As it rotates, the plastic is pushed forward to achieve compaction, melting, and mixing. The thread is composed of different functional sections, each contributing to conveying, compaction, mixing, and plasticization — the combination delivers a better melt and higher output.

For a co-extrusion laboratory machine, the screw carries an additional responsibility: it must deliver a melt whose rheology matches the co-extrusion partner material in the die. This is why the SJ-30/28 screw design changes with the raw material. According to different raw materials, the screw has different aspect ratio and compression ratio (L/D), and the barrel adopts a different structure — a high-viscosity, temperature-sensitive material such as PVC requires a different screw geometry from a low-viscosity polyolefin such as PE or PS. The screw is manufactured from high-quality nitrided steel (38CrMoALA), finished by nitriding and fine grinding, giving high corrosion resistance, high wear resistance, and a long service life across repeated material changes.

Structure 2 — The Head Flange Joint 

The head flange joint connects the die head to the barrel. It is heated by a heating ring, preventing the molten plastic from cooling while it transitions from the barrel into the die. In co-extrusion, the temperature of every melt stream at the die is a process variable: the heated joint keeps the primary melt at its set temperature, so the layer interface in the die sees a consistent thermal picture — the basis of stable layer bonding and uniform thickness distribution.

Structure 3 — The Transmission System 

The transmission system rotates the screw evenly with the necessary torque under the selected process conditions, completing the plasticization and transportation of the plastic. Because different plastic products require different screw speeds, the machine uses a variable frequency motor that directly drives the gearbox through a coupling, with a governor providing speed regulation. The screw speed is smoothly, steplessly regulated within the speed range, and the speed is read directly on the tachometer of the control panel — and can also be read directly on the governor.

Stepless speed control is essential for co-extrusion development. The layer thickness ratio between melt streams is set by the relative output of each screw; the operator uses the stepless regulation to balance the streams, hold the ratio, and reproduce it in the next trial.

The Co-Extrusion Logic on the SJ-30/28

In a co-extrusion laboratory configuration, two or more melt streams — each produced by a screw matched to its material — are brought together in a co-extrusion die, where they flow as parallel layers and emerge as a single multilayer structure. The L/D and compression ratio of each screw are matched to its material's melt behavior; the die geometry distributes the streams into the target layer structure; and the relative screw speeds set the layer thickness ratio. The result is a representative multilayer sample — a capping layer over a core, a functional skin over a substrate, a colored layer over a natural layer — that can be inspected, tested, and iterated before production scale-up. The exact layer count and die configuration are project-specific and available on request.

Key Advantages of the SJ-30/28 Co-Extrusion Lab Extruder

1. True Co-Extrusion Capability on a Laboratory Scale — Multilayer Structures Before the Production Die

• Feature: A co-extrusion laboratory extruder configuration in which the screw, barrel, and drive are specified for multilayer melt processing, at a 5 kg/h laboratory scale.

• Advantage: Layer materials, thickness ratios, and interfacial behavior are verified with kilogram quantities of material instead of production-scale batches.

• Benefit: Multilayer product development becomes fast and economical — the structure is proven, and the production line runs only validated recipes.

2. Material-Matched Screw Design — L/D and Compression Ratio Customized per Raw Material

• Feature: According to the raw material, the screw design has different aspect ratio and compression ratio (L/D), and the barrel adopts a different structure; the appropriate barrel, screw, and drive are selected together.

• Advantage: Each melt stream is plasticized by a geometry matched to its material's viscosity and thermal sensitivity — PVC, PE, PS, PA, POM, and PMMA each get the screw they need.

• Benefit: Consistent melt quality for every layer material, fewer interfacial defects, and representative results that transfer to production.

3. 38CrMoALA Nitrided Screw — Reliable Across Material Changes

• Feature: The screw is made of high-quality nitrided steel 38CrMoALA, finished by nitriding and fine grinding, with functional thread sections for conveying, compaction, mixing, and plasticization.

• Advantage: High corrosion and wear resistance keep the screw geometry stable across repeated changes between PVC, PE, PS, PA, POM, and PMMA compounds.

• Benefit: Repeatable trial results over a long service life — the laboratory co-extruder keeps producing trustworthy multilayer samples.

4. Variable Frequency Stepless Speed Regulation — Balance the Layer Streams Precisely

• Feature: A variable frequency motor directly drives the gearbox through a coupling, with a governor providing stepless speed regulation; screw speed is read on the control panel tachometer or the governor.

• Advantage: Each screw's output can be set and held at any point in the speed range, so the layer thickness ratio between streams is controllable and reproducible.

• Benefit: The co-extrusion process window is fully explorable — thickness ratios, process stability, and material limits are mapped on the bench, not on the production line.

5. Heated Head Flange Joint — Stable Melt Temperature to the Die

• Feature: The head flange joint between head and barrel is heated by a heating ring.

• Advantage: The molten plastic is prevented from cooling at the critical barrel-to-die transition, keeping the melt stream at its set temperature.

• Benefit: Stable layer interfaces and consistent multilayer quality — the thermal discipline that co-extrusion demands.

6. A Clear Scale-Up Path — From 5 kg/h Lab to Production Co-Extrusion Lines

• Feature: The SJ-30/28 is the laboratory member of a single screw family extending through SJ-35 (15 kg/h) and SJ-45 (25 kg/h), with production-scale lines in the Chenxing extrusion range.

• Advantage: Co-extrusion data developed on the laboratory machine — screw geometry, temperature, speed, layer balance — transfers to the same single screw principle at production scale.

• Benefit: The processor validates the multilayer structure once and scales with confidence, whether to a production co-extrusion line or to the Chenxing EPC platform.

Materials and Applications for Laboratory Co-Extrusion

Design Materials

The SJ-30/28 is designed to extrude thermoplastics such as PVC, PE, PS, PA, POM, and PMMA. Each family brings a different melt behavior to the co-extrusion die:

• PVC — high viscosity, temperature-sensitive; requires a screw with controlled shear and a barrel structure that avoids degradation.

• PE — low viscosity, easy flow; the workhorse layer material for pipes and packaging structures.

• PS — rigid, transparent; common as a structural or optical layer.

• PA — hygroscopic, high melting point; requires pre-drying and a screw matched to its crystalline melt behavior.

• POM — engineering polymer with a narrow processing window; demands precise temperature and shear control.

• PMMA — transparent, optical-grade; used for glossy and light-guiding layers.

For hygroscopic materials such as PA, pre-drying is required before extrusion — the machine works with the Chenxing drying range (see the supporting equipment section below).

Co-Extrusion Application Directions

The SJ-30/28 serves laboratory co-extrusion processing for the development of multilayer composite structures across pipe, sheet, and profile products:

• Protective and functional layers — a capping layer over a recycled or lower-cost core, a UV-resistant skin over a standard substrate, a barrier layer in a multilayer pipe.

• Dual-color and decorative structures — a colored surface layer co-extruded over a natural or contrasting core, for profiles and sheets.

• Material-combination structures — two or more thermoplastics combined in one product, using each material where it contributes most.

The specific layer count, layer materials, and die configuration for each project are arranged on request.

Laboratory Co-Extrusion vs. Other Chenxing Equipment — How the Range Fits

The SJ-30/28 is the multilayer development partner of the production range: the PVC shelf label strip extrusion line and the PETG pipe production line both exploit co-extrusion at production scale, and every such line starts its layer structure in a laboratory — the SJ-30/28 is the machine that validates it there.

Supporting Equipment Around the Laboratory Co-Extrusion Line

The SJ-30/28 integrates with Chenxing's material preparation and handling range. For hygroscopic layer materials such as PA, the 750A dehumidifying dryer supplies production-scale low-dew-point air, while the 201A/J conveying integrated crystal dehumidification dryer and the 530A crystal dryer cover compact and crystalline-polymer duties; the STG-U hopper drier plastic resin dryer is the lightweight option for general resin drying. Material transfer into the hoppers uses the VLF powder suction machine, the VLF-L continuous powder suction machine, or the FSP crushing material suction machine, with the screw feeder automatic feeding machine for controlled dosing of each layer material. Blends and dry colors are prepared in a high-speed mixer industrial mixer; magnetic protection at the feed points comes from a CJ magnetic frame hopper magnet. Trial output can be granulated with a plastic pelletizer or a PVC hot-cutting pelletizing line, and scrap regrind is handled by the plastic crusher and the agglomerator / film densifier. For a complete turnkey development-to-production facility, the 990A Advanced Material Processing EPC Project designs the entire material path around your process.

Frequently Asked Questions

What is the SJ-30/28 co-extrusion laboratory extruder used for?

The SJ-30/28 is a laboratory-scale co-extrusion single screw extruder used for co-extrusion experiments, product development, and multilayer composite structure sampling. It extrudes thermoplastics such as PVC, PE, PS, PA, POM, and PMMA, and serves as the validation platform before a multilayer structure — protective layers, functional skins, dual-color structures — is committed to a production-scale co-extrusion line.

Which materials can the co-extrusion lab extruder process?

The machine is designed for thermoplastics such as PVC, PE, PS, PA, POM, and PMMA. The screw design has different aspect ratio and compression ratio (L/D) according to the raw material, and the barrel adopts a different structure, so each material family gets a matched processing geometry. For hygroscopic materials such as PA, pre-drying is required before extrusion.

What is the output capacity of the SJ-30/28 lab co-extruder?

The SJ-30/28 delivers a maximum capacity of 5 kg/h, with a 30 mm screw, a 20–25 L/D ratio customized to the material, and a 3 kW motor. This output class is intentional: large enough to produce representative multilayer samples, small enough to keep co-extrusion trials economical. The series extends to the SJ-35 compact configuration (15 kg/h) and the SJ-45 (25 kg/h) for higher-capacity laboratory work, on request.

Why does the screw design change with different raw materials?

Different thermoplastics have different melt viscosities, thermal sensitivities, and degradation behaviors. A screw geometry that plasticizes PE well may over-shear PVC or under-mix PA. According to different raw materials, the screw design has different aspect ratio and compression ratio (L/D), and the barrel adopts a different structure. The appropriate barrel, screw, and drive mechanism are selected together to meet the needs of high-quality product processing — and in co-extrusion, this matters twice, because each layer material needs its own matched melt stream.

How is screw speed controlled on this lab co-extruder?

The transmission system uses a variable frequency motor that directly drives the gearbox through a coupling, with a governor providing speed regulation. The screw speed is smoothly, steplessly regulated within the speed range, and the current speed is read directly on the tachometer of the control panel — it can also be read directly on the governor. Stepless regulation is essential for co-extrusion: the layer thickness ratio between melt streams is set by the relative screw speeds, which the operator can balance and reproduce trial after trial.

Can the laboratory co-extrusion machine be scaled up to a production line?

Yes. The SJ-30/28 is the laboratory member of the Chenxing single screw family, extending through the SJ-35 (15 kg/h) and SJ-45 (25 kg/h), and the same co-extrusion principle is applied at production scale across the Chenxing extrusion range — for example the PVC shelf label strip extrusion line. For compounding duties, the parallel co-rotating twin screw extruder is the production partner, and for complete turnkey plants the 990A Advanced Material Processing EPC Project engineers the full production system.

Get a Customized Co-Extrusion Laboratory Solution — Request a Quote

Step 1 — Define Your Multilayer Structure: Tell us the structure you want to develop — the layer materials, the product form (pipe, sheet, profile), and the target layer configuration. If you are working with PVC, PE, PS, PA, POM, or PMMA, name the grades; the screw L/D and compression ratio are designed from the material, not from a template.

Step 2 — Choose the Co-Extrusion Configuration: Chenxing specifies the SJ-30/28 around your structure: the screw and barrel matched to each layer material, the co-extrusion die arrangement for your layer count, the take-off and sampling equipment for a 5 kg/h output, and the drying, feeding, and granulation tools around the line. Heating power, temperature control, layer count, and die configuration are provided on request.

Step 3 — Request a Quote from Nicole: Contact Nicole at +8615951187228 or ceo@cxsljx.com with your multilayer development task. We respond within 24 hours with a formal quotation, configuration list, and delivery schedule. Chenxing provides installation guidance, commissioning support, and operator training on material-matched screw selection, temperature profiles, and layer balance control.

Step 4 — Verify the Structure, Then Scale with Confidence: Run your multilayer trials on the SJ-30/28, validate layer adhesion, thickness distribution, and material compatibility — then scale the proven structure to production. Whether the production target is a co-extrusion line such as the PVC shelf label strip extrusion line, a single-layer line such as the PETG pipe production line or the PC LED light cover extrusion line, or a compounding plant with the parallel co-rotating twin screw extruder, the laboratory data travels with the process.

Chenxing's full supporting range — SJ-25/25 laboratory mini single screw extruders, plastic pelletizers, PVC hot-cutting pelletizing lines, agglomerators / film densifiers, high-speed mixers, dryers, and EPC engineering — completes the picture. As a single-source partner, Chenxing Machinery supports your development from first pellet to full production.

Contact Chenxing Machinery Today:

• Contact Person: Nicole

• Phone / WhatsApp: +8615951187228

• Email: ceo@cxsljx.com

• Company: Zhangjiagang Chenxing Machinery Co., Ltd.

• Website: www.chenxingmachinery.com