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FAQ

Frequently Asked Questions

2 ) What is the best mold temperature to use when molding Xarec?

3 ) Is there a difference in creep resistance between the different grades of Xarec?

4 ) Can I obtain Xarec in different colors?

5 ) What is the effect of UV light on Xarec?

6 ) Do Xarec grades have established automotive specifications?

7 ) What kind of surface finish can I expect from a molded part with Xarec?

8 ) Is it possible to extrude Xarec?

9 ) Are film grades of Xarec available?

10 ) Is Xarec suitable for the new ‘lead free’ solders for connectors?

Answers:

1 ) Because the surface of molded Xarec EA and WA grades is non polar, few organic adhesives provide good, unprimed adhesion. High energy surface pretreatments such as plasma, corona or UV in conjunction with typical organic adhesives, do provide durable adhesion. Additionally, there are several 2 part, temperature cured encapsulants, pottants or liquid silicone rubbers available. The Xarec N WA grades are blended with Nylon and therefore easier to bond to. Several different epoxy based adhesives systems are available.

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2 ) The selection of the optimum mold temperature is dependant on the performance requirements of the finished part. Typically, water cooled tool temperatures (50˚C - 80˚C) result in a molded part having a slightly lower surface crystallinity than parts molded with a ‘hot’ tool (130˚C - 155˚C). Parts with lower surface crystalinity are, in general, adequate for the majority of components molded with Xarec, however, hot tool temperatures help to maximize heat resistance (DTUL), chemical resistance as well as dimensional stability. Parts molded with water cooled tools (i.e. less than maximum surface crystallinity) can be fully a crystallized (annealed) by subsequent exposure to temperatures of 150˚C for 90 seconds or more.

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3 ) Typically, the flexural creep modulus of Xarec EA and WA grades, at equivalent wall thicknesses and glass fiber loading, is lower than that of PBT or Nylon based thermoplastics. Syndiotactic polystyrene (SPS) is a non-polar polymer with very low propensity to hydrogen bond, a chemical characteristic that improves creep resistance of polar polymers such as PBT or Nylon. The flexural creep modulus of Xarec N grades, a combination of SPS with Nylon, is significantly improved compared to the EA and WA grades and at a similar level to that of PBT or Nylon. For maximum flexural creep performance of the EA and WA grades, tool temperatures should be maintained in the range of 130˚C to 155˚C.

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4 ) A range of standard colors can be provided in pre-formulated, factory compounds. Custom color matches can also be supplied provided minimum order quantities are met.

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5 ) The primary effect of exposure to UV light on Xarec materials is a color shift. The natural color of the SPS material (slight off white) shifts to yellow after significant UV exposure. The visual perception of the shift is mostly masked by use of darker colors. Typically, the color shift is accompanied by a slight, predictable reduction in mechanical properties. Contact Idemitsu Chemicals for specific grade recommendations if your application will involve long term exposure to UV light.

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6 ) Currently the Xarec WA and N WA grades comply with a significant number of automotive specifications of both U.S., European and Japanese car manufacturers. Contact Idemitsu Chemicals for details.

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7 ) Xarec products rapidly solidify during the cooling phase of an injection molding cycle. At tool temperatures in the range of 50˚C - 80˚C rapid solidification can result in a non uniform texture on the part surface if the tool surface is ‘smooth’. Hot tool temperatures in the range of 130˚C to 155˚C will produce a more uniform surface. Alternatively, by applying a light ‘texturing’ to the ‘smooth’ surface of the tool, parts molded at lower tool temperatures will display a more uniform appearance.

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8 ) Xarec WA grades have been successfully extruded using sheet extrusion systems with calendaring rolls which helps to develop biaxial orientation that improves sheet strength and reduces the potential for defects such as holes or tears.

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9 ) Injection molding grades of Xarec are typically manufactured with homopolymer SPS. The crystallization rate of homopolymer SPS is fast and film extruded from homopolymer is of limited value. Copolymer grades of Xarec SPS are available and are slow to crystallize. Subsequent orientation of the film in a biaxial stretching process will induce crystallization and result in film with useful properties.

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10 ) Connectors manufactured with Xarec SPS are suitable for connector to printed circuit board soldering processes provided that the ‘on board’ temperatures during the heating phase of soldering are maintained at or below 260˚C. Additionally, consideration should be given to the design of connector as it pertains to amount of stress that might be placed on the plastic housing by the metal terminal. If pre-stressed pin designs are used, consideration must be given to the correct creep modulus in the design of the pin cavities. Additionally, it is advantageous for Xarec housings with pre-stressed pin designs to be molded with tool temperatures in the range of 130˚C to 155˚C to insure full crystallization of the component.

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