What Determines Quality During Polycarbonate Sheet Production?

If a customer opens a pallet of the sheets and finds that they have some defects such as non-uniform thickness, turbidity of the surface or weak edges, most likely the problems resulted from some stages of the manufacturing process. The stages include type of resin, efficiency of extrusion line, quality of UV layer application, testing and packaging. The quality of polycarbonate sheets is dependent on these stages.In order to place an order, a buyer should make sure that the manufacturer performs these stages properly.This article provides information about how each stage influences the quality of sheets, how the buyer should assess samples and documents regarding these stages and the checklist.

Why Quality Matters Before You Order

Checking polycarbonate sheets is usually done after they are installed, and not right away after their delivery.Greenhouse roofs, carports, or sign boards may all appear in good condition upon arrival, but issues such as yellowing, splitting, or bending may only show up after a few years, after the installation is completed.In addition to paying the cost of the sheets, additional expenses will be incurred from the cost of dismantling, replacement, and even the delay of the entire project itself.

Where Problems Usually Start

Most quality problems can be attributed to a limited number of reasons, which correspond to particular stages of production of polycarbonate sheets:

• Mixed or low-grade resin: affects clarity, impact strength and batch consistency (see Raw Material).
• Uneven thickness: leads to weak spots and poor fit in frames (see Manufacturing Process).
• A missing or weak UV layer: causes yellowing and brittleness outdoors (see UV Protection).
• Rough handling during transport: brings scratches, moisture and damaged edges (see Testing and Packaging).

As you can see, the following sections will be structured according to the factory process from the raw materials to the loading dock.

Why a Lower Price Can Cost More

The comparison of two quotations is meaningful only if both the sheets have equal thickness, resin grades, and UV properties. If any one of the sheets is thinner than the quoted specifications, it will reduce cost but decrease its strength and lifespan. Knowledge on the basic principle of polycarbonate sheet fabrication makes this comparison process very simple, and there is a checklist provided at the end of this article that can be used in talking with all suppliers.

Raw Material: Virgin Polycarbonate Resin

Resin determines the limit of the performance of the sheet. There is no way for even the best run extrusion line to fix this problem. Pure virgin polycarbonate resin is more predictable than the recycled one in terms of clarity and impact resistance.

What Resin Affects

The effect of resin lies in its ability to affect four aspects that consumers look out for: clarity of the sheet, resistance to impact, yellowing under exposure to UV light, and batch-to-batch consistency. With larger surface areas, such as in glazing applications in greenhouses, inconsistencies from one batch to another are easily observable.

How to Check

• Ask which resin brand and grade is used, and whether only virgin material goes into the order.
• Request batch records or resin supplier documents.
• Place sheets from different batches side by side in daylight and compare color and clarity.
• Look for specks, streaks or cloudy spots on the surface and edges.
• Ask for RoHS and REACH compliance documents if your market requires them.

At GWX, production uses virgin resin from well-known suppliers, for example BAYER and SABIC, and incoming material goes through inspection method.

Manufacturing Process: Thickness and Structure

In the process of extrusion, the resin that is melted is pressed through a die into a flat sheet. In order for the thickness to remain even, temperature, line speed and cooling should be kept constant during the entire process. Even small deviations may result in uneven thickness, waves, bubbles or internal stress, which is the reason why two factories that use the same resin may produce sheets of varying quality.

Thickness Tolerance and Flatness

Thickness influences the strength and weight of the sheet and determines its ability to fit inside an aluminum profile or a frame. Large variations in the tolerance of the thickness may produce weak areas that bend or break under pressure and sheets that will not fit into a frame properly.

To test the thickness of the sheet, it needs to be measured in at least five places (using a caliper or micrometer - both edges, the middle point and two intermediate points). Afterwards, the sheet needs to be placed on a flat surface to determine whether it bends.

Twin-Wall and Multiwall Structure

The internal structure of the twin wall polycarbonate sheets is equally important as their external thickness. The thickness of the walls, as well as the ribs and their uniformity are crucial in defining stiffness and insulation.

Make a cut through one corner and inspect the cross-section. The ribs must be uniformly spaced and undamaged while the walls must have a uniform appearance along the length of the sheet. Weighting a sheet and comparing it to the claimed weight per square meter is a good additional test.

UV Protection for Outdoor Use

Polycarbonate sheets deteriorate due to the impact of sunlight when untreated, becoming brittle and yellow. UV-protected polycarbonate sheet is generally preferred for use in outdoor conditions.

Co-Extruded Layer or Coating

The UV layer in co-extrusion is integrated into the sheet when it is being produced, meaning it becomes a part of the surface. The coating layer is added later on and therefore wears off quicker.

Inquire about the type of process that is used, the side/s where the UV layer is present, and the thickness of the UV layer.

Which Side Faces the Sun

One installation error is when the sheet is mounted with the UV face towards the interior side. Most films have markings for their exterior surface. Verify this information with the sample and pass it on to your installers because an improperly mounted film will provide no benefit.

Ask What the Warranty Covers

The validity of long-term warranties is questionable if there are no clear conditions in place. It would be good to request, in writing, what constitutes a failure (e.g., yellowing, reduction of light transmission, etc.), duration of coverage, and what will be provided upon acceptance of the warranty claim. Weathering testing results can back up the warranty.

Testing and Packaging

Testing is where claims turn into evidence. Packaging is where good sheets can still be damaged, so the two belong together.

Test Reports and Certificates

The usual test methods include light transmittance (usually performed to ASTM D1003 standard), impact strength, fire rating (e.g., UL 94), sheet thickness and weathering ability. The quality management system certification, such as ISO 9001:2015 and IATF 16949 standards, indicates that the manufacturer has established a documented quality system. GWX is certified according to both and its sheets were tested by SGS and a state test facility for polymers and building materials.

Typical requests from customers are for the documentation, including batch certificates and RoHS and REACH documents as well. The GWX sheets comply with RoHS and UL/CE standard and the raw materials are supplied by producers with official environmental certification, complying with REACH and RoHS requirements. Full sets of documentation are available for selected markets. Additionally, GWX performs three inspections throughout the manufacturing process, including raw material inspection, production line check, and sheets after finishing prior to shipment.

Reading a Test Report in Three Steps

• Step 1: Verify the date, report number, and batch/product number.
• Step 2: Make sure that the thickness, color, and sheet type match the order.
• Step 3: Confirm the name of the laboratory, test procedure used, and test parameters.

A test report that does not match your product, or that is several years old, may not reflect current production.

Packaging and Shipping

Scratches, dust, and even moisture can form during transport. The best practices include film coverage of both sides, corner protection, sealing of the edges in twin-wall panels, and the way of stacking, which does not press against the sheet surface.

Request pictures of the packaged goods prior to shipping. Upon delivery, make sure the film is intact, edges are sealed, no moisture penetrated into the channels, and no scratches appeared.

Quick Checklist for Choosing a Supplier

In the case that you are dealing with different manufacturers of polycarbonate sheets, ensure that you ask the same questions from all of them. Provide the same information regarding the thickness, size, color, and application to each manufacturer of polycarbonate sheets for easier comparison of prices. You can also buy a small sample prior to buying a whole container.

Conclusion

At every stage, there is always something left that the buyer can authenticate. GWX can provide you with some samples along with their testing reports and certificates for comparisons. Since the establishment of GWX in 2011, the company has the capability to produce 30,000 tons per annum and customize in terms of size and color, export logistics and after-sales service available 24/7. For quotation, please send us an email.

FAQ

1. Can I get samples before placing a bulk order?
Yes, samples are a good way to check thickness, UV marking and surface quality first.

2. Can sheets be made in custom sizes and colors?
Yes. Share your dimensions, thickness, color and application so we can confirm what is possible.

3. What applications are GWX polycarbonate sheets used for?
GWX sheets are used in building curtain walls, agricultural greenhouses, municipal facilities, photovoltaic support projects and advertising signs. Dimensional accuracy follows China’s national standard GB/T 14846, which helps the sheets fit well in frames and profiles. If your project follows a different standard, such as ASTM or EN, let us know and we can discuss your requirements.

4. What types of polycarbonate products can I source from GWX?
GWX makes hollow (twin-wall and multiwall), solid and corrugated sheets, along with polycarbonate film, embossed sheets, diffusion sheets, flame-retardant (VO) solid sheets, anti-scratch and anti-static sheets, anti-riot shields and profiles. These serve construction, signage and display, medical and consumer products, industrial packaging and OEM projects. Tell us your application and we can suggest a suitable type.