Two polyamide grades for water injection moulding are the result of three years' R and D to find an optimal balance between water injection processing and glycol resistance in an application context.

Rhodia Engineering Plastics introduces two new Technyl polyamide grades specifically designed for water injected cooling pipes : Technyl A 338Wit1 V30 blk 36N and Technyl A 338Wit2 V30 blk 36N. This major product introduction follows three years of dedicated research and process development work, including the development of Rhodia's own WIT mold, water injectors and injection unit. The challenge of the Rhodia WIT development team was to find an optimal balance between water injection processability and glycol resistance in an application context where specific material properties are required to fit to the technology, while cooling circuit specifications are increasing.

In terms of glycol resistance, these 2 new grades equal or even outperform the actual Technyl GIT product A 218Z1 V30 blk 34N used in mass production for numerous cooling pipes.

For example, following a life test (1000h at 130C in a mix of water and long life coolant), the tensile strength at break of Technyl A 338Wit1 V30 is as good as the GIT grade, when this level is increased by 15% with Technyl A 338Wit2 V30.

Other retained properties such as impact resistance are improved about 80% with a Technyl A 338Wit1 V30 and doubled with Technyl A 338Wit2 V30, when compared to the GIT material.

However, the primary benefit of Technyl Wit1 and Wit2 grades is their ability to create high quality inner surfaces, thanks to even glass fibre coverage by the polymer, along with a constant wall thickness free of water inclusion.

In cooling pipe applications, the end benefits include greatly reduced pressure loss in the cooling circuit, along with reduced water pump size, and a reduced risk of cooling fluid pollution by glass fibres during engine life time.

Prototypes of cooling pipes, designed with critical angles and varied sections to approximate real shapes, have been produced internally by Rhodia Engineering Plastics engineers with Technyl Wit1 and Wit2, using side-cavity moulds (other molding techniques such as pushback, water flow or pre-filling can be also used).

They show a high consistency in the process, with great precision, each shot giving identical part quality and performance, while adding the benefit of reduced shrinkage, reduced warpage and reduced cooling time compared to standard injection molding or Gas Injection Technology.

To validate performance over part life (test 1000h at 130degC under 2,4 bars rel constant overpressure), pipes tested in Rhodia automotive validation labs showed no breakage, along with consistent full wall thickness (no erosion), and no exposure of glass fiber through the polymer barrier.

In addition, Rhodia Engineering Plastics has developed a specific expertise in CAE calculation methods to simulate the WIT process, allowing development engineers to utilize precise engineering data in order to make appropriate decisions when designing a part and a manufacturing tool.

Rhodia Engineering Plastics' unique know-how in the WIT process, injector design, computer simulation, added to available tools and devices for prototype tests, has already led to promising partnerships with customers and equipment manufacturers for industrial developments with new Technyl Wit1 and Wit2 grades.

With the introduction of these two new grades, Rhodia Engineering Plastics has completed its portfolio of Technyl PA66 GF30 glycol resistant grades, and is now in the unique position of being able to supply high performance materials optimized for every technology available to produce cooling pipes (standard injection molding, blow molding, gas injection technology and now water injection technology).

Apart from these two new specific glycol resistant grades dedicated to WIT, a number of Technyl Star grades have already reached the market for use in WIT produced parts, such as design parts as door handles and roof-rails, or semi-structural parts such as front-ends and pedals.

Rhodia Engineering Plastics, headquartered in Lyon, France, is the world wide specialist in polyamide engineering thermoplastic materials.

The company has a sales network that spans the world, with manufacturing plants and technical development centres in Europe, North America, South America and Asia.

Rhodia is one of the world's leading manufacturers of specialty chemicals.

Providing a wide range of innovative products and services to the consumer care, food, industrial care, pharmaceuticals, agrochemicals, automotive, electronics and fibers markets, Rhodia offers its customers tailor-made solutions based on the cross-fertilization of technologies, people and expertise.

Rhodia subscribes to the principles of Sustainable Development communicating its commitments and performance openly with stakeholders.

Rhodia generated net sales of EUR 5.5 billion in 2003 and employs 23,000 people worldwide.