Fixing sheets in outdoor applications

Outdoors, PVC sheets are affected by large temperature changes. The coefficient of linear thermal expansion a= (mm/m × °C) for change in length under the influence of heat must be considered. For KÖMACEL and KÖMATEX, the coefficient of linear thermal expansion is a = 0.08 mm/m × °C.

PVC sheets from Kömmerling are moisture-resistant. Therefore, any change in length can be predicted with precision because no additional moisture-dependent movement occurs. This is not the case with products from some other manufacturers.

The change in length of KÖMACEL and KÖMATEX depends primarily on the maximum expected surface temperature and the sheet length used. By taking the coeffiecient of thermal expansion (α) and knowing the color of the surface, the difference in length can be computed as follows:
Δ l = 1 × α × Δt (mm)
Δ l = change in length (mm)
l = sheet length (m)
Δ t = temperature differential (K or °C)
α = coefficient of thermal expansion (mm/m x °C)

The basic temperature to be taken for computing this figure is the installation temperature. An increase in temperature results in expansion; a decrease in temperature results in contraction. Sheet contraction is based on the lowest outside temperature according to the climatic zone map.

The change in length can be found by referring to the following diagrams. Note: The darker the color and the higher the surface temperature, the larger the resulting change in length.

Surface temperatures for sheets of various colors

Change in length related to change in temperature, length of sheet and coefficient of expansion

Example 1

Δ l = 1.5 × 0.08 × 60 = 7.2 mm
The change in length for a white sheet of 1.5 m and a difference in temperature of 60°C is 7.2 mm.

Example 2

Δ l = 3.0 × 0.08 × 60 = 14.4 mm
The change in length for a white sheet of 3 m and a difference in temperature of 60°C is 14.4 mm.