Rising energy costs have increased public awareness and interest in energy efficient solutions in all
areas of life. When manufacturers of motorhomes and caravans build the walls, floors and ceilings of their
vehicles, they need to choose a product that can withstand both a wide variety of loads and weathering
conditions over several years vehicle’s lifetime and be sustainable and energy-efficient as well.
The selection and quality of the materials used are critical for the overall performance and longevity
of the vehicle; as the core material within the composite panels plays an important role and has significant impact
on:
- insulation performance
- damp and moisture resistance
- overall assembly strength
- Cost/Energy efficiency.
Opting for XPS as the core layer material for composite panels means opting for long-lasting effective thermal insulation, because it is impervious to moisture and has low thermal conductivity.
But what many do not know is that even between XPS products there are performance differences. How is
this possible? The answer is actually very easy: Imagine you’d like to replicate a recipe of a yummy lemon cake you have eaten at your best friends’ house. You ask for the recipe, you get it, and after you have baked your cake following quantity and all steps, you think that somehow your cake does not have the same taste. Well, we are assuming that your cake will taste better… but nevertheless, it will not be the
same. Sometimes, even small differences can have a big impact on the results. In our case, to produce XPS the main differences can be summarized
as such:
- Manufacturing technology: The process used to manufacture XPS foam can vary between different
manufacturers, affecting the final properties of the foam. Factors such as extrusion equipment, temperature, pressure, and processing time can all affect the properties of the final product. Same way as for a cake: The oven, the oven temperature & cooking mode, some technologies can allow more homogeneous foam structures. - Raw materials: The raw materials used to produce XPS foam can vary between different manufacturers as well. While the basic chemical composition of the foam is the same, differences in the quality, or composition of the raw materials, in particular when significant amount of recycled material is used, will definitely affect the final properties of the foam – such as long-term mechanical performances & moisture uptake, VOC (volatile organic compounds) emissions.
- Density & cells shapes: XPS foam can be produced in a wide range of densities and cells’ structures. Long terms fatigue resistance, in other words longevity of the vehicle’s body, is directly correlated to density. More mass = stronger providing it is evenly distributed in the cells’ walls. Cells’ shape and dimensions are reflecting the distribution of the solid parts in the cells’ walls. While density is quite easy to keep under control by manufacturers; consistently run to run producing appropriate closed cell structures is a very difficult art to master requiring strong manufacturing experiences and appropriate equipment to produce and measure.
- Additives: XPS foam can be modified with additives to improve performances such as reaction to fire or/and thermal performances (Infra-Red blockers). Different manufacturers may use different additives or different amounts of additives.
- Porosity: We talk here about XPS foam’s cell walls porosity, EPS bead structures and voids between the beads. Indeed, even if measured as closed cells, due to too thin walls, some foams could show very significant permeability to some gas: in particular moisture / vapor.
Yes, the vapor diffusion resistance of XPS (extruded polystyrene) thermal insulation can vary between different.
producers. Vapor diffusion is a measure of how easily moisture can pass through a material. The laws of physics is stating that as soon as we have a gradient of temperature between 2 sides of a panel, a vapor pressure difference is created inducing a vapor flow which will go from warm to cold side. In the case of XPS insulation, a high vapor diffusion resistance is desirable because it helps to significantly reduce moisture entering into the vehicle Sandwich panel. Opening the door to moisture is a certitude to shorten lifetime and comfort of the vehicle’s body by altering irreversibly mechanical structure and thermal performances.
Therefore, it’s important to consider a range of factors when selecting core materials to ensure that they will perform as expected in a given application during the lifetime of the vehicle.