Emerging Polyurethane Composite Technologies

Long Fiber Injection (LFI) Composites and Baydur® STR Long Fiber Technology

Automation Makes SRIM More Economical Process

New technologies developed by RIM processing equipment manufacturers have made RIM more relevant to the composites market. Each of the major polyurethane processing machinery makers offers technologies to inject long glass fibers along with the polyurethane system as a one-step process, rather than the traditional two-step process of inserting performs and/or mats into the mold. In these one-step technologies, a glass chopper is attached to the polyurethane mixhead, which is mounted to a robot. The robot is programmed to move over the open mold cavity while dispensing both the long glass fibers and the polyurethane SRIM formulation in an open-pour method. At the end of the pour, the mold is closed to form the part. These developments are helping to automate the SRIM process, making parts more economical to produce. In fact, it's the fastest-growing area of SRIM composites. One-step SRIM technology can utilize either a foamed or solid SRIM formulation.

Benefits of one-step long-fiber technology include:

Ability to utilize lower cost fiberglass rovings rather than mats
Ability to vary the amount of glass reinforcement in the part
Ability to utilize either a foamed or solid polyurethane formulation
Ability to produce polyurethane SRIM parts with polyurethane in-mold coating, thus eliminating secondary painting operations

See this innovative composite technology in action. Click here to view a Flash video. Or contact Bayer MaterialScience to visit its Pittsburgh, Pa. headquarters and see the Bayer Long Fiber Technology Lab for a live demonstration.

Bayer MaterialScience has combined long fiber technology with its Baydur® STR rigid-polyurethane structural foam RIM system to offer the Baydur Long Fiber Technology to the composites market.

Typical Properties for Baydur® Long Fiber Injection

Property, units	English units	Metric units
Specific Gravity, pcf	70	80
% Glass	30	40
Flex Str., psi	24000	28000
Flex Modulus, psi	840000	990000
Notched Izod, ft-bls/in	12	17
Un-notched Izod, ft-lbs/in	20	27
Notched Charpy, ft-lb/in2	23	30

Un-notched Charpy, ft-lb/in2	27	26Metric units
Tensile Str., psi	15000	18000
Tensile Mod., psi	1000000	1200000
CLTE, in/in/C¡, x10E-6	18	11

Following are examples of how Baydur LFI RIM solutions are at work today.

Interior cab components for a heavy-duty truck manufacturer were the first parts to be made in the United States with the one-step process. In Europe, the process is used to produce numerous components. Examples are dashboards and parcel shelves for automobiles. The roof for the economical SMART car is based on the one-step process. In this application, a sheet of thermoplastic film that becomes the exterior surface of the part and a headliner material that becomes the interior of the part are placed into the mold prior to the SRIM processing. Development efforts are underway to develop Class A polyurethane SRIM parts based on in-mold coating and thermoplastic film technologies.

A newer commercial use of one-step technology and Bayer's composite SRIM polyurethanes is Jeld-Wen's exterior residential door skins. Bayer worked closely with Jeld-Wen, the world's largest manufacturer of windows and doors, to develop a Baytec® polyurethane and Baydur¨ STR polyurethane formulation specifically for this application. Use of Bayer's Baytec and Baydur polyurethane materials gives the doors increased dimensional stability, better impact resistance and strength, along with the excellent aesthetics consumers demand. The skins of the doors are formed using long fiber technology, in which long glass fibers are injected along with polyurethane resin in a one-step process. To complete the door manufacturing process, JELD-WEN laminates the composite door skins to a polystyrene core and wood edge frame.

The outer cabinets for Clearwater Spas' entire 2007 spa line are produced with the Bayer MaterialScience Baydur¨ STR polyurethane RIM system and the Long Fiber Technology (LFT) process by Creative Polyurethanes, a custom polyurethane processing company. The use of polyurethane RIM composites contributes not only to the spa's attractive appearance, but also offers significant production and processing advantages over the previously used synthetic material. The Baydur STR rigid-polyurethane structural foam RIM system produces parts that are strong, lightweight, dimensionally stable and impact, heat and chemical resistant.

Proven commercially in Europe, long fiber technology is now gaining popularity among composite fabricators and their customers in North America. For example, custom molder Romeo RIM produces eight different interior trim panels for the sleeper cab of a Freightliner tractor trailer using Long Fiber Technology in conjunction with Bayer's Baydur polyurethane SRIM system. This process displaced conventional FRP processing for these parts as a result of its lower cost and weight savings.