JEC COMPOSITES MAGAZINE - Issue #45 - November/December 2008 - 33

Thermoplastics For automotive interior trim applications, Azdel, Inc. offers a portfolio of products named SuperLite®. These materials are typically sold in large sheet form, in weights ranging from 600 to 2,000 grams per square metre, and generally come with functional cover materials that provide adhesion, barrier, ease of handling, and enhanced acoustic performance. The materials consist of a network of randomly-oriented fibres coated with, and held together by, thermoplastic resin. A distinguishing attribute of materials with these structures is that they “loft” or expand in the thickness direction when heated. This expansion is due to the softening of the thermoplastic resin which allows the fibres (previously bent or constrained as a result of the formation process) to return to a straightened orientation (Fig. 1). with increasing part thickness. This is to be expected for a material with a fixed areal density (basis weight) as increasing the thickness simply means incorporating more air in the structure, thereby increasing porosity. The engineering properties, being normalized by the increasing cross sectional area, will naturally decrease as the thickness is increased. When considering the absolute load-carrying capacity of the material (stiffness or peak load), however, the trend is quite different and exhibits an optimum thickness for maximum load-carrying capacity. This optimum can be explained by the presence of two competing mechanisms: the initial increase is due to a structural effect of increased part thickness and the subsequent reduction is due to localized weaknesses or instabilities with increased porosity. By selecting the basis weight of the material and choosing the moulded thickness, a part designer may tailor the stiffness, strength, and acoustic performance of the part without changing materials. Second-generation product portfolio In order to extend the value proposition of SuperLite®, Azdel has introduced a second generation of products offering improved acoustics, improved mechanical performance, weight reduction, reduced part costs, reduced environmental impact, and improved functionality. These materials include the SuperLite XLT® portfolio, VolcaLite® portfolio, and a portfolio of surfacing materials for improved functionality. The SuperLite XLT® products exhibit more than twice the lofting capability as the original SuperLite® portfolio. By leveraging this enhanced performance to increase moulded part thickness, customers are able to produce parts with both increased sound absorption, and increased strength and stiffness. Depending on the design objectives, this performance can then be leveraged for increased part performance, reduced weight and cost, or a combination of both (Table 1). Table 1: Comparison of SuperLite® and SuperLite XLT® performance, including different scenarios for SuperLite XLT® basis weight selection. SuperLite® XLT® Example 1 XLT® Example 2 XLT® Example 3 Basis weight (g/m2) Free loft (mm) Moulded thickness (mm) Peak load (N) Fig. 2: Typical SuperLite® performance as a function of thickness. 1,000 6.0 2.8 23 2.8 1,000 11.0 4.5 30 5.0 900 10.5 4.5 26 4.4 800 10 4.5 20 3.4 Stiffness (N/cm) The lofting capability enables part manufacturers to produce high-quality aesthetic parts, produce variable-thickness parts, and also “design in” part performance by variable tuning of thickness. The typical thickness dependence of material performance is shown in Fig. 2. Engineering properties – such as flexural strength or flexural modulus – show the decreasing performance Emerging requirements for end-of-life disposal have created increased costs for the use of fibreglass-containing parts in some regions of the world. These costs are related to the use of incineration furnaces for material disposal. Because of the proximity of furnace operating temperatures and fibreglass melting temperatures, the fibreglass tends to coat the furnace No45 November-December 2008 / jec composites magazine

JEC COMPOSITES MAGAZINE - Issue #45 - November/December 2008

Table of Contents for the Digital Edition of JEC COMPOSITES MAGAZINE - Issue #45 - November/December 2008