PVC sheets are a common material used in the construction, signage, and industrial manufacturing industries. But, the market is full of suppliers of widely varying quality. The impact of the wrong choice can be production delays, lost materials and lost client relationships. The first thing is to know what the most common procurement pitfalls are so you can implement a solid sourcing process.
The Trap of Inconsistent Thickness and Dimensional Tolerances
The one thing that is often forgotten about PVC sheets is thickness consistency. When purchasing, many buyers believe that the 3mm thickness means 3mm throughout. Actually, a cheaply produced sheet will be of good quality in some places and bad in others. This is far more than a minor nuisance.
Printing and sign makers need a consistent thickness or else they will face catastrophic results. The thicker the sheet, the more it can damage printer heads. In most cases, the different distance between the printhead and the substrate leads to misdrops of ink particles. This creates a blurry background, color wash and uneven ink coverage. Two-sided printing is made even worse if the first side is printed and the sheet is not flat when it is printed again, causing the resulting side to be misaligned and thereby wasting the whole job.
How to prevent: Order from manufacturers that are ISO certified, and have more stringent tolerances. When ordering in bulk, test the thickness at several different points throughout the sheet for accuracy, and order samples first. Sellers will give you the dimensional tolerance data from the beginning if they are reputable.
Hidden Costs of Inconsistent Raw Materials and Impurities
A PVC sheet may look like one thing but be quite another. Many of the small scale workshops save money by re-using material, or “re-grind,” in their manufacturing process. This reduces the price per unit but also comes with a raft of unnoticed issues.
Printed and cut sheets may have impurities not visible in the raw materials. This manifests in the form of uneven density, bubbles or black specks. In addition, an inconsistent raw material blend causes varying panel structure. Lower cost panels are often thinner, thus less rigid and less solid. This renders them more susceptible to breakage, load-induced surface scratching and warping under load.
How to prevent: Ask the supplier for raw material testing reports and view the cross section of the sheet when assessing the supplier. A cross section of virgin material is smooth and dense, whereas recycled material may be rough, loose or have black spots. Seek manufacturers who are using virgin PVC resin and can offer ISO 9001 quality assurance documents.
The Invisible Problem of UV Degradation and Aging
A new PVC sheet may look amazing, but it is actually its long-term performance that matters. Very important but often overlooked is the use of UV stabilizers. These additives are necessary for the polymer chemical bonds not to be broken when exposed to sunlight, thus compromising the mechanical properties, and resulting in color change (yellowing) and increased brittleness.
This is a typical case of "you get what you pay for. Products that are not UV-stabilized are typically more affordable, but at the expense of durability. This is a difference that may not be visible to the buyers when viewing a new sample; however it is manifested as degradation will occur over a period of months or years of use.
How to prevent: If a product is going be exposed to sunlight or UV light, be sure to request documentation that shows UV stabilizers were used. Call for test reports of accelerated weathering exposure, including ISO 4892-2. This data will give a number-based indication of the sheet's performance over time.
Dimension Instability and Out-of-Square Edges
A square, level panel is a non-negotiable to fabricate a precise panel. One of the errors made is to think the edges of a PVC sheet are square, or that the sheet will stay flat under varying conditions.
Non-square sheets are a pain to print for signage and large format printing. With two sided prints, even a slight out-of-square edge can cause problems with prints being mis-registered. In addition, if the sheet is out of flatness, it can damage the print head due to the wavy or uneven surface on the vacuum table of the printer. Printing can have a sheet straighten out on the platen, but the waves are likely to come back up as soon as the vacuum is lifted. The storage is also a factor, as the sheets may warp over time when not supported.
How to prevent: When precision is necessary, it is not advisable to assume the sheet is square; see if it is square or re-cut the edges or use a router table to square the sheet before processing. For large or high-precision jobs, specify precisely-squared sheets from your distributor. Make sure to store properly and level to avoid warping during installation prior to installation.
JIAYING (PLUSWIN) has accumulated 19 years of experience in industry and 10 years of export experience to all parts of the world. High performance PVC foam boards, laminated boards and WPC foam boards, eco-friendly, waterproof, mold resistant. We help to prevent those problems for our B2B customers by keeping to ISO manufacturing requirements and using virgin materials. Talk to us about your PVC sheet sourcing needs.