Pultrusion Process

The pultrusion process
The pultrusion process, very similar to extrusion, is the only continuous process for the production of composite profiles. In pultrusion, reinforcing materials (glass, Kevlar or carbon fibres) in the form of continuous rovings, mats and other types of fabrics, are pulled through a resin matrix bath or other impregnation device, then carefully guided through a pre-shaping station followed by a heated, high precision, die in which the resin matrix sets at high temperature to form the final product. Finally, the hardened profile is continuously pulled past a saw, activated to cut it into pre-determined lengths.

Pultruded composites
A pultruded composite is generally made up of reinforcing materials (glass, Kevlar, carbon fibres) held together by a rigid resin matrix (polyester, vinylester, epoxy thermosetting resin). Often, surface veils are incorporated to improve weathering and corrosion resistance.
The sketch below shows a typical section of a pultruded profile for general use.

Section of a pultruded composite

For special applications, the reinforcement can be of different types and nature (fabrics, woven rovings; carbon or aramid). Although most profiles utilise a thermosetting polyester resin matrix for specific applications, other types of resin may be used, such as acrylics, vinylester or epoxy.
It is not possible to indicate physical or mechanical data applicable to all pultruded profiles because the characteristics may vary greatly due to several factors: 

  • Type, quantity and orientation of the reinforcement; 
  • Type of resin, nature and content of fillers; 
  • Geometry of the section.

The table below shows average values for the main characteristics of profiles made with isophthalic polyester resin reinforced with glass fibres, for two types of reinforcement composition:

Reinforcement made entirely of glass rovings in the profile axis direction
Reinforcement arranged as shown in the sketch above

For comparison we also indicate values for steel and aluminium.

Glass reinforcement content by weight (%)  75   65   
Density (g/cm³)
Tensile strength
In the axis direction:
Maximum load (MPa)>600350/400 370/500200/400
Elastic modulus (Gpa)>4025 / 3021070
Maximum deformation (%)1.5-2.0  
In the transverse direction
Maximum load (MPa)30/ 5050 – 100 370/500200/400
Elastic modulus (Gpa)8 – 1021070
Maximum deformation (%)1.5-2.0  
Flexural strength
In the axis direction:
Maximum load (MPa)>600350-400 330/500200/400
Elastic modulus (Gpa)>4015 – 2021070
In the transverse direction
Maximum load (MPa)100-200 330/500200/400
Elastic modulus (Gpa)9 – 1221070
Compression strength
In the axis direction:
Maximum load (MPa)>300>200 
In the transverse direction
Maximum load (MPa)20-3070 – 90 

Other typical properties

Dielectric strength (Kv x mm)5 – 10
Thermal expansion coefficient (m/m/ºC)5 – 20 E-6
Thermal conductivity (W/m/ºC) 0.25 – 0.35 

Note: For structural applications it is important to consult our technical department.