Points of attention when using plastics
Over the years, plastics have often been initially developed as a solution for a specific situation. Often as an alternative to more traditional materials. More durable, lighter in weight, better chemically resistant, more wear-resistant, cheaper, etc. Such a material subsequently also turns out to be a solution for many other applications and the market for the material in question is growing.
In addition to very favorable properties, every material also has disadvantageous properties. In other words; Where a characteristic is beneficial in a specific situation, that same characteristic can be disadvantageous in another situation. On this page we highlight a number of features that we think are good for you as a customer and/or user to be aware of.
Lakwijk Kunststoffen BV is a wholesaler of semi-finished products. We are the link between manufacturer and the market. Semi-finished product has the appearances; plate, rod and tube. Plates, rods and tubes are produced larger than the dimensions indicated on paper. The plate is slightly thicker, wider and longer. The staff is therefore slightly thicker and longer. The tube is slightly thicker on the outside and the hole is slightly smaller. The manufacturer does this to guarantee that the dimensions can be extracted from the material during processing. Manufacturers use a plus tolerance and speak of “clean sizes”.
PVC, PE and PP pipes are manufactured in accordance with the DIN standard and the external and internal dimensions are of the correct size for a matching fitting. In other cases, when a plate, rod or tube must be exactly sized, the material must be machined. You can do this yourself, but you can also give Lakwijk Kunststoffen BV that assignment.
If Lakwijk Kunststoffen BV processes according to specified dimensions or drawings, this is done with the utmost precision. Our skilled colleagues and our machinery are of the highest level.
However, the same dimensional accuracy cannot be required from the material in the application as is usual in metal. This has nothing to do with the quality of the processing or the material, but with the intrinsic properties of plastic. Plastic is much more sensitive to temperature differences than metal. Expansion and contraction are proportionately greater. We take the temperature input into account when processing, but if the temperature during transport or in the final application deviates significantly from the room temperature in our workshop, you will lose some of the accuracy. We are talking about one to several tenths of a millimeter.
Stress relaxation also plays a role and with certain materials moisture absorption can also play a role. In most cases this is not a problem because the flexibility of plastic provides a degree of forgiveness. However, it is important to take this into account. Within the most regular plastics, POM and above that PETP (Ertalyte) are the most dimensionally stable. In addition, there are a number of so-called “high performance” plastics such as PEEK and PEI that are even more dimensionally stable.
Customers usually have to install Lakwijk products in an application. A product can be locked or clamped, a product can be mechanically attached, a product can be welded and it is sometimes decided to glue a product. Bonding is very easy with a number of plastics. However, there are also plastics that cannot be glued, or cannot be glued well.
Your contact person will ask you if you want to start gluing, but it is also good that you are aware of this during a development process. Ask in time whether a material can be glued or which mounting technique we recommend.
There are situations in which plastics are used outdoors. That is almost never a problem. Many plastics are UV resistant and do not or hardly discolour or degrade.
However, there are also plastics, for example certain crystal clear plastics, that are not UV resistant. Fortunately, this discoloration occurs very slowly and evenly, but eventually the sun has an effect on the material, causing it to age faster than desired. This manifests itself in crazing, hairline cracks and brittleness. However, these materials are often also available with a UV-resistant top layer. Even in that situation, your Lakwijk contact person will proactively ask the question, but it is wise that you also consider that this is a point of attention.
Certain plastics are suitable for applications in which they come into contact with food. When these materials come into contact with food, no substances (plasticizers) migrate from the plastic to the food and therefore these materials do not pose a threat to public health. This does not mean that these materials can be used indiscriminately in food applications. To comply with European legislation, specific standards must be met to obtain the European “Food Grade” label, and this concerns more than just the physical properties of the material.
A material is Food Grade if the material has been proven to be safe, but is also traceable in the chain to the raw material in the event of unexpected calamities. In addition, a product must be accompanied by a certificate indicating that everything was carried out safely during handling and processing (packaging, coolants, air, cleaning agents, etc.). Every plate, every rod, every tube therefore has a unique code and every delivery is accompanied by unique documents. Without that “identity” and documents, the material is safe, but does not meet the Food Grade standard. Sometimes customers do not yet have sufficient knowledge or there are still misunderstandings on this point.
Lakwijk is a specialist in the field of processing and delivery within the Food Grade provisions, and can provide you with excellent guidance in this regard.
Specific plastics are used because of their chemical resistance. Within the regular materials, consider PVC, PP and PE. These materials are also resistant to caustic cleaning agents that are necessary in certain applications.
However, there are also plastics that are not very chemically resistant. In practice, this most often leads to problems in crystal-clear plastics. If acrylic and polycarbonate are cleaned with agents that are more aggressive than simple soapy water (or preferably just warm water), dull spots or hairline cracks can occur and the panel can even become brittle.
Solid core plate and other thermosetting plastics are very stiff, and there are more plastic materials that have been specifically developed with stiffness in mind, usually using a channel structure. In general, however, plastic is less stiff compared to glass, wood or metal. The flexibility of plastic is desirable in many situations, but of course also has disadvantages.
Acrylic mirror is a very safe and affordable alternative to glass, but if it is used for a larger surface, the plate remains less tight and (especially in the mirror version) you will get unwanted distortion. If a larger plastic sheet is used horizontally and is not supported at sufficient points, the sheet will sag. A thicker and therefore stiffer plate is not always a solution because the weight of the plate leads to more sagging. It is important to take the limited stiffness of plastics into account when determining the design and dimensions of the application.
Glass, metal and wood are sensitive to scratches. Plastics are also sensitive to scratches.
The virtually unbreakable polycarbonate is very strong, but nevertheless very sensitive to scratches. A user of this material sometimes makes a mistake about this. Polycarbonate is also available in a version with a scratch-resistant top layer. This top layer makes the record more resistant to scratches, but does not make it scratch-free.
The plastics that are usually used in visual applications where their appearance and aesthetics are important, are supplied with a protective film. Industrial plastics for which this does not apply or to a lesser extent, and whose surface still needs to be processed in most cases, do not have a protective film from the factory. It may therefore be slightly scratched as a result of sliding in the production process or during transport. That is almost never a problem, but it is an aspect to take into account for the customer, and also for us in material advice.
Curious about what we can do for you or would you like advice?
We are happy to assist you!