Material Innovations

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New nylons from DSM

DSM says that its new Akulon Ultraflow offers up to a 25% improved flow over standard nylon 6 with comparable glass loadings.

DSM Engineering Plastics has developed Stanyl High Flow and Akulon Ultraflow for its line of nylon products. These new materials enable what DSM claims are improved processing features for cost-reduction possibilities.

A new generation of nylon, Stanyl High Flow 46HF5040 is a reinforced flame-retardant 4/6 nylon. It combines the strength and toughness levels of DSM's standard nylon flame-retardant materials with enhanced flow characteristics virtually the same as liquid-crystal polymers (LCP), with a cost savings of up to 50%, according to the company.

According to DSM, there is only a 10% difference between the viscosity of standard unfilled nylons and its Akulon Ultraflow 30% glass-fiber (GF) reinforced nylon 6 grades.

Offering high toughness in dry-as-molded conditions, the weld-line strength of the new nylon grade is three times higher than that of LCP, enabling connector manufacturers to post-inset pins directly after injection molding without the risk of cracking, thereby reducing rejection levels.

DSM claims that components made of the new nylon maintain their dimensional integrity during reflow soldering up to 280°C (536°F) due to the extreme high stiffness level of the material at those temperatures. This is important for the new lead-free soldering techniques. While LCP is often specified for such components, DSM says the cost of LCP is significantly higher than that of Stanyl.

DSM's Akulon Ultraflow is a glass-fiber reinforced nylon 6. DSM says the new nylon 6 offers up to 25% improved flow over standard materials with comparable glass loadings. According to the company, the material's benefit is that it retains the mechanical performance levels of standard glass-reinforced nylon while also reducing cycle times and improving surface appearance. The company's proprietary method of reducing viscosity in the new material translates to such improvements as shorter cycle times, less molded-in stress, reduced energy costs, and superior surface appearance. The reduction in total cycle time is the result of improved flow length, which yields a shorter injection and hold time. Using less holding pressure to produce the same part decreases the stress on the mold caused by high-injection pressures. In addition, with the better flow, the operator is able to use a lower processing temperature, reducing the inherent energy costs associated with injection molding while still achieving a completely packed-out part.

Environmental control knobs require enhanced mechanical, thermal, and chemical-resistance properties, which DSM says it provides with its 20% glass bead reinforced nylon 6, Akulon K224-R4U.

A trend in the marketplace is the desire for a high-gloss finish, usually only obtained with unfilled nylon. Glass-reinforced products in the past have tended to have the glass inter-dispersed within the nylon, resulting in a rough surface appearance. DSM claims that its chemistry allows the nylon to flow to the surface faster and wet out the glass matrix better, resulting in a higher gloss and improved finish.

Grades for the new productswhich include natural, black, and custom colors in unfilled 30 and 50% glass-fiber reinforced compoundswill be targeted toward injection-molding applications and others where reduced cycle times and improved surface appearance are important. DSM says this new technology can also be applied to other Akulon glass-fiber reinforced grades.

- Jean L. Broge

ULSAB progress

The automotive industry may throw up its collective hands in horror at some of the legislative, economic, and engineering challenges it faces, but after this initial ritual, it generally gets on with the business of solving problems. One problem has been the need to reduce vehicle weight. This is a continuing difficulty, with additional features introduced to satisfy the consumer often offsetting weight trimmed from components.

Autolaser Technology's new Nd:YAG two-dimensional laser-welding facility.

To find ways of economically reducing vehicle weight, the international UltraLight Steel Auto Closures (ULSAC) study continues. Preliminary results from its validation phase confirmed that by using innovative design combined with currently available steel technologies, engineers could reduce vehicle weight significantly with no cost increase while designing state-of-the-art structures for vehicle safety.

One ULSAC member, Corus, cites a window-frameless door that has been built 33% lighter than the benchmarked average of all types in the concept phase and 42% lighter than the benchmarked average for such doors in validation. Some 30 sheet steel producers commissioned the ULSAC study to help find ways to reduce vehicle weight without cost penalties or added manufacturing complexity. Porsche Engineering Services is managing the program.

ULSAB is opening the door to lighter-weight structures.

To design a lightweight, mass-efficient closure that exceeds crash safety requirements for lateral stiffness and side intrusion, those leading the ULSAC study have completely reappraised the typical car door, according to Corus. This has led to reduced weight in key areas but stronger hinges and latches. Key to this has been the replacement of the normal steel inner panel with four tubes: two tubes hydroformed in 280-MPa (40-ksi) high-strength steel (HSS) for the latch and hinge uprights, with another two straight tubes in 800-MPa (116-ksi) ultra HSS forming the adjoining upper and lower longitudinal members. A stamped laser-welded tailored blank of 1.2 and 1.0 mm (0.05 and 0.04 in) gauge 140-MPa (20-ksi) mild steel provides an additional reinforcing inner front member, which incorporates the mirror flag. The resulting mass of the basic steel structure, at 10.5 kg (23.1 lb), is almost 2 kg (4.4 lb) lighter than the target mass.

The UltraLight Steel Auto Suspension (ULSAS) study also demonstrated that it is possible to produce a steel multi-link suspension design that is 3% lighter than the benchmarked aluminum system. These details have emerged from the mid-term report of the overall Advanced Vehicle Concepts study. According to the study, when the dynamic properties of steels are taken into account in design calculations, the overall deformation of a vehicle structure can be reduced for a given crash deceleration. These concepts have major implications for passenger safety with the potential, for example, of less intrusion into the footwell in a frontal collision. This new approach to crash design is said to provide a shorter crash pulse associated with the use of steel's dynamic properties and a lower level of deformation and crash intrusion.

Autolaser Technologies (part of Corus) has established what it describes as Europe's first Nd:YAG two-dimensional laser welding facility. Corus intends to produce up to 3 million advanced tailor-welded blanks annually for the auto industry.

- Stuart Birch

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