Molding Xencor™ LFTs parts requires some basic preparation and equipment which are key to the quality of molded parts. Proper measures need to be taken related to drying the resin and keeping it dry before processing, as well as selecting a suitably sized molding machine with respect to the screw design, the shot volume and the total residence time of the compound in the machine. A frequently underestimated aspect is the tool design, gate dimensions and venting aspects, which should be machined in a large dimension to obtain a smooth material flow and a long maintenance and cleaning interval of the tool.
Please read our Xencor™ Processing Guide for further detailed information about molding Xencor™ grades.
Xencor™ compounds need to be dried before they are processed.
Most polymer resins are hygroscopic. When exposed to humid air, they will absorb moisture. While the effects of moisture absorption on the properties and dimensions of molded parts are minimal, effects on the molding process can be significant: excessive fumes at the nozzle, drooling, dosing-phase stability, surface defect, fast-vent clogging. Volatile components which are generated can also sublimate onto the surface leading to mold & vent deposits in the tool. In addition, several Xencor™ compounds are processed at an elevated temperature which is close to the degradation limit of the polymer resin and slight amounts of moisture at this high temperature can lead to polymer chain scission which results in a loss of mechanical properties. For these reasons, the pre-drying of these materials is essential; it is recommended that a desiccated air dryer be used.
Please read our Xencor™ Processing Guide for further detailed information about molding Xencor™ grades and the technical datasheet for detailed information of each grade.
Fibrous reinforcement, which orients parallel to the weld-line during molding, can cause dramatic loss of strength in the weld line area. The phenomenon is inherent to any fiber-reinforced material and the decrease in strength is directly related to the volume of reinforcement.
Proper tool design (gate, overflow tab…) and processing conditions can significantly help minimize fiber orientation and the formation of poor weld lines. Performances similar to those met with standard short-fiber compounds can be achieved with proper guidance on Xencor™ products.
If they cannot be avoided, weld lines must be located in the area where minimal stress is expected.
Venting is also a key element for the area of weld lines. Vents must help the air volume compressed between the 2 melt fronts to escape. In such areas, the use of vent gaps of min. 0.02 mm is recommended.
For more information or technical assistance, contact your Specialty Polymers Customer Technical Development representative.
Sample pellets for molding trials and several shapes of molded articles can be supplied for testing purposes upon request. There are different sample types available. Stock shapes or other thick-walled semi-fabricates for machining prototype parts for example, are not offered routinely due to the complexity of the practical aspects to cool such parts fast enough and prevent the material from degrading at the inner core of thick sections.
For more information or technical assistance, contact your Specialty Polymers Customer Technical Development representative.
Most common Xencor™ grades are fully characterized to run FEA analysis. For more information or technical assistance, contact your Specialty Polymers Customer Technical Development representative.
In order to ensure adequate support and guidance for our customers, reliable simulation capabilities have been developed for most common grades of Xencor™ product lines and are of prime importance for the design of new plastic parts.
Please contact your Specialty Polymers Customer Technical Development representative to help you with your application.