Wherever the most demanding technical requirements must be satisfied - in the automotive and machinery industries but also in the household appliance and leisure sectors - designers have often had to rely on metal in the past. But this is where plastics can provide the greatest benefits, since when it comes to mobility resources can be conserved and the environmental impact reduced. Moreover, when designing complex machinery, function integration and ease of processing count: these are the three primary benefits of plastic as a lightweight material.
This is why many components that were previously made of metal have been replaced by plastic components over the past decades. The more demanding the application, the greater is the performance required from the plastic. Disregarding high-temperature materials such as PEEK or polysulfones, the greatest advances have been made with specially formulated polyamide grades, as can be seen from the first volume production of plastic transmission cross beams and engine mounts in 2009. If this class of materials wishes to make even greater inroads in high-load applications in the machinery and automotive industries, additional innovations are necessary.
With this in mind, BASF is entering the market with a new class of high-performance polyamides in the K-year of 2010 and presenting its first long glass-fiber-reinforced (LF) polyamide grade Ultramid Structure LF. This product group which is new in BASF's portfolio, represents a considerable advance in terms of performance with metal substitution as the objective, since where even highly optimized short glass fiber-reinforced products reach their limitations, LF polyamides offer new opportunities.
The self-confident name also shows that these polyamides are part of the new group of specialty polyamides designated Ultramid Structure LF, with the aid of which BASF is taking a large step in the direction of specialty engineering resins with high capability.
LF: Greater performance thanks to the 3-D network
The exceptional feature of components made from long glass-fiber-reinforced plastic is the three-dimensional glass-fiber network that forms during conventional injection molding, imparting the end product with its outstanding physical properties at both low and elevated temperatures. The fiber network forms the skeleton of the component and is retained even after ashing. This structure is the reason why the warpage, creep behavior and energy absorption of this material class already approaches the behavior of metals without losing the classical benefits of plastic.
Production of LF resins employs the pultrusion process to first create plastic strands containing endless glass fibers. In a second step, these strands are cut to a pellet length of 12 millimeters. The customer can process the LF granules on a conventional injection molding machine. With a favorable distribution of fibers in the molded plastic part, a three-dimensional fiber network of primarily three to six millimeters long fibers is formed directly without any significant additional effort. Processors can avoid major investment costs, and still gain access to a new sophisticated material: Compared to classical reinforced polyamides with their only 0.3 millimeters long fibers, entirely new component characteristics are achieved.
Properties and applications
These exceptional component properties come from the enhanced mechanical capabilities brought about by the long glass-fibers: the LF polyamide grades Ultramid Structure are very stiff and strong at elevated temperatures, while at low temperatures they exhibit outstanding impact strength. Impressive creep behavior, the minimal warpage and the far higher energy absorption - and thus crash performance - compared to conventional materials are further benefits.
The automotive industry has several obvious potential applications for the new LF polyamides. Engine mounts and metal inserts in seat structures are some examples. So are crash absorbers which are intended to undergo controlled destruction upon impact in order to absorb as much energy as possible and thus protect the rest of the vehicle. At the same time, other branches of industry need plastic components that can withstand high loads as well, e.g., coffee machines, where replacements for die-cast parts are sought, threaded connectors or components in power drills and bicycles.
Ultramid Structure LF and ULTRASIM
In addition to its solid backwards integration of PA precursors, BASF benefits from two additional aspects regarding its entrée into the LF polyamides market: decades of experience and extensive formulation know-how from its wide range of classical PA 6 and PA 66 grades, as well as the capabilities offered by what has become a universal simulation instrument, namely, ULTRASIM.
Over the past few years, ULTRASIM has proven to be a valuable simulation tool for designing parts mainly in the automotive sector but meantime in other sectors as well. In addition to accurate predictions of component behavior as a function of gating parameters and fiber anisotropy, it is possible with the aid of Mathematical Component Optimization to establish the best possible shape under the given conditions.
As part of its entry into the market with the new polyamides, BASF has also upgraded the capabilities of this computer-based tool to permit simulation of components reinforced with long glass-fibers. The best example is a crash absorber made of Ultramid Structure LF developed in-house: Its controlled failure upon impact is predicted and mapped precisely by ULTRASIM. Experiment and Simulation match closely, so that - as in the case of short glass-fiber-reinforced materials - BASF will offer appropriate methods and be able to assist with component design for the new product group Ultramid Structure: This is a service that is not yet available in the LF-polyamide market in this comprehensive form.
BASF has been operating a pultrusion line on a pilot scale for two years already and is currently investing in an industrial-scale plant. This demonstrates its commitment to long-term involvement in this new field.
The company is starting with a small range of PA 6 and PA 66 grades with LF levels between 40 and 60 percent as well as various types of stabilization. This portfolio will be expanded in the future to meet market requirements. First customers have already received samples.