What is Polyurethane Pultrusion?
Think of pultrusion as the opposite of extrusion, where material is forced through a die. In the pultrusion process, reinforcing fibers are pulled from a series of creels through a die and thoroughly mixed with a polyurethane resin. Engineers from Bayer MaterialScience were instrumental in creating the injection box technology used in this closed reactive process, as well as formulating a new resin for the process - Baydur® PUL 2500.
Once the reinforcing fibers are impregnated with resin, the material is passed through a heated steel die where the resin matrix is shaped and cured. The profile is continually pulled until it exits the die, where it is cooled then cut to the desired length.
What are the advantages of polyurethane pultrusion?
In the polyurethane pultrusion process, more reinforced fibers can be added, making the end product dramatically stronger. It allows for a more economical manufacturing process as well, because rovings can be used instead of costly mats, and high line speeds can be achieved. With pultruded polyurethane, there is excellent resin-to-fiber bonding and improved impact and transverse properties. And because parts made from pultruded polyurethane are stronger and lighter in weight, they can be made larger, with thinner walls.
In addition, pultruded parts are less brittle and can be assembled in a conventional manner, without cracking or splintering. Furthermore, the polyurethane pultrusion process is environmentally friendly, with no styrene. Additonally, polyurethane pultrusion offers:
Where can polyurethane pultrusion be applied?
- lighter and more economical profiles due to strength advantages
- higher specific strength and stiffness
- superior fabrication and fastening results
|Because of its significant strength, pultruded polyurethane can be used in a variety of industries, ranging from aerospace to consumer products. This exciting new material offers longer product life, greater impact resistance and greater structural strength than traditional materials, so it’s the ideal choice for everything from lineal applications like window frames to loadbearing structural shapes, like I-beams. There’s no doubt that polyurethane pultrusion technology is the wave of the future.|
|Polyurethane Pultrusion - Typical Physical and Menchanical Properties|
|Property (units)||Test Method ASTM (other)||Baydur PUL - 2500 English units||Baydur PUL - 2500 Metric units|
|Flexural Strength (k psi)||D 790||>180||>1200|
|Flexural Modulus (k psi)||D 790 ||6,900||48|
|Flexural Strain (%)||D 790||3.0||3.0|
|Charpy Impact (kJ/m2)||(ISO 179)||>189||>189|
|Un-notched Beam Impact (ft-lb/in)||D 4812||>76.8||2900|
|Short Beam Shear (k psi)||D 2344||>9||>62|
|HDT (¡C @ 264 psi)||D 648||240||240|
To make polyurethane pultrusion possible, researchers at Bayer MaterialScience LLC, Nautilus Composites LLC and the University of Mississippi School of Engineering identified two significant barriers for pultruding polyurethane resins into composite parts:
The researchers developed processing technologies and methods that allow high-speed production of high-quality polyurethane pultrusions. Mechanical property testing of the composite specimens produced indicate the degree to which the properties of the neat resin are translated into useful composite properties.
SUPERIOR STRENGTH AND LOW CONDUCTIVITY MAKE POLYURETHANE PULTRUSION TECHNOLOGY IDEAL FOR WINDOW FRAMES
A Canadian manufacturer is bringing a breath of fresh air to the window frame manufacturing industry — and opening the door to a variety of new applications in other industries as well. The company is using polyurethane pultrusion technology to manufacture window lineals that are vastly superior to their aluminum, wood and vinyl counterparts.
According to the company, conventional pultrusion technology has been around for decades. It began to develop fiberglass pultrusion capabilities in 1989, and started manufacturing with polyester resin in 1992. Now, the company is pioneering the production of window frames using an innovative polyurethane pultrusion process. By pultruding polyurethane resin, Inline can now produce larger, stronger parts, with thinner walls.
To accommodate the new process, Bayer MaterialScience developed Baydur® PUL 2500 — the ideal resin for use in pultruded polyurethane applications.
The polyurethane pultrusion process offers a wide range of benefits compared with other materials. Unlike extrusion, the polyurethane pultrusion process allows for a higher concentration of fiberglass, making the end product substantially stronger. When window frame components are made from fiberglass-reinforced pultruded polyurethane, they become eight times stronger than PVC frames. Moreover, they are less brittle, so they won’t crack or splinter, resulting in superior fastening. Another advantage is pultruded polyurethane frames are 40 times less conductive than aluminum, making them much better insulators.
Frames made from pultruded polyurethane have excellent expansion and contraction properties and can withstand even the most severe weather condition, from arctic blasts to desert heat and seaside moisture, without corroding. They are aesthetically pleasing, giving the end user the choice of either a painted or attractive wood-grain finish. Furthermore, the polyurethane pultrusion process is environmentally friendly, since it consumes less energy during production and contains no styrene.
The manufacturer now has the capability to produce lighter profiles that are strong enough to be used in large frames, even curtain walls. And the profiles are cost-effective and environmentally friendly.
- the fast gel times of the raw materials when mixed
- the tendency of the chemistry to produce internal voids in the material during gel and cure