Grivory® HT1VA - 5 FWA BLK 9225

Grivory HT1V-5 FWA black 9225 is delivered dry and ready for processing in sealed, air tight packaging. Pre-drying is not necessary, provided that the packaging is undamaged

Storage

Sealed, undamaged bags can be kept over a period of time of at least one year in storage facilities which are dry and can protect the bags from the influence of weather, direct sunlight and any kind of damage.

Drying

Grivory HT1V-5 FWA black 9225 is dried to a moisture content of £ 0.10 % and sealed air tight. If the packaging becomes damaged or is left open too long, then the material must be dried. A too high moisture content becomes evident by a foaming melt, excessive nozzle drool and silver streaks on the moulded part. Drying can be done in two ways:

1. Desiccant dryer
2. Vacuum oven

Drying time

If there is only little evidence of foaming of the melt or just slight silver streaks on the part, then the above mentioned minimal drying time will be sufficient. If material is stored open for days, shows strong foaming, unusually easy flow, streaks or a rough surface on the moulded part, then the maximum drying time is required.

Warning : Silver streaks can also be caused by overheating of the material or by a too long melt residence time in the barrel.

Drying temperature

Temperatures above 100°C for both desiccant dryers and vacuum ovens should be avoided. Visible yellowing of the material is an indication of oxidation in case of light colours. In order to detect yellowing, it is recommended to keep a small granule sample as reference. For longer residence times (over 1 hour) in the hopper a hopper heating or a hopper dryer (80°C) is required in order to avoid moisture uptake of the granules.

Use of regrind

Grivory HT1V-5 FWA black 9225 is a thermoplastic material. Hence, incomplete mouldings as well as sprues and runners can be reprocessed. The following points should be observed:

• Moisture absorption already occurred
• Grinding: Dust particles and particle size distribution
• Contamination through foreign material, dust, oil, etc.
• Level of addition to original material
• Possible colour variations
• Reduction of mechanical properties 

When adding regrind, the operator has to take extra care during processing

For components in direct contact with drinking water or food the use of regrind should be avoided. As long as the mechanical performance of parts made with regrind is secured, a new drinking water approval or certification has to be obtained for parts with the maximum possible regrind content.

Grivory HT1V-5 FWA black 9225 can be processed economically and without problems on all machines suitable for polyamides.
 

Screw

Wear protected, universal screws with shut-off nozzles are recommended (3 zones).

Shot volume

In order to reduce the average dwell time of the polymer melt in the cylinder, a suitable screw diameter has to be selected. The following rule applies:

Selecting the injection unit : Shot volume = 0.5 - 0.8 x max. shot volume of injection unit

Heating

At least three separately controllable heating zones, capable of reaching cylinder temperatures up to 350°C are recommended. Separate nozzle heating is necessary in order to avoid the formation of plugs. The cylinder flange temperature must be controllable by cooling in order to counteract the formation of condensate in the feed zone of the cylinder.

Nozzle

Open nozzles are preferred because they allow an easy melt flow and last longer than needle shut-off nozzles, and they exhibit less wear. If the open nozzle remains open for too long, cold plugs can be formed at the tip. Removal of the open nozzle after dosing requires adapted decompression in most cases. Needle shut-off nozzles, however, increase the shear of the material during filling and may cause critical weld lines in the part, but they can still be used.

Clamping force

As a rule of thumb the clamping force can be estimated using the following formula:
Clamping force = 7.5 kN (for a cavity pressure of 750 bar) x projected area (cm2 )

The design of the mould tool should follow the general rules for reinforced thermoplastics. For the mould cavities common mould tool steel quality (e.g. hardened steel) which has been hardened to a level of 56 - 65 HRC is necessary. We recommend additional wear protection in areas of high flow rates in the tool (e.g. pin point gates, hot runner nozzles).

Demoulding / Draft angle

Parts moulded from Grivory HT1V-5 FWA black 9225 solidify very quickly and show excellent dimensional stability. Asymmetric demoulding and undercuts are to be avoided. Generous provision should be made for ejection with many large pins or a stripper plate. Demoulding draft angles between 1 and 5° are acceptable.

Venting

In order to prevent burning marks and improve weld line strength, proper venting of the mould cavity should be provided (venting channels on the parting surface dimensions: depth 0.02 mm, width 2 - 5 mm).

Gate and runner

To achieve the best mould filling and avoid sink marks, a central gate at the thickest section of the moulding is recommended. Pin point (direct) or tunnel gates are more economical and more common with technical moulding; however, they will also cause higher shear of the polymer melt. To avoid premature solidification of the melt and difficult mould filling, the following points should be considered:

Gate diameter : .8 x thickest wall section of the injection moulding part
Runner diameter : .4 x thickest wall section of the injection moulding part (but minimum 4 mm)

Mould filling, post pressure and dosing

The best surface finish and high weld line strength are achieved when a high injection speed and a sufficiently long post pressure time are employed. The injection speed should be regulated so as to reduce towards the end of the filling cycle in order to avoid burning. For dosing at low screw revolutions and pressure the cooling time should be fully utilised

Basic machine settings 

The required tool surface temperature depends on the geometry and the wall thickness of the part. As a rule of thumb it can be assumed that the thinner the wall thickness is, the higher the tool surface temperature has to be. Tool surface temperatures up to 190°C are recommended for small wall thicknesses. The flow temperature of the temper unit should be adjusted so that the measured surface temperature of the mould cavity exceeds 140°C.

Start up and purging

Foreign materials in the cylinder should be removed with suitable purging materials. Hot-runner systems should be purged likewise. Glass fibre reinforced polyamide 66 is a suitable “bridging material”. Cylinder heating should start with a clean, productfree screw, starting from the temperature level of the “bridging material” of 300°C up to the required temperature level of 340°C. After at least three full dosings (free-shots) - applying the shortest possible residence time - the startup procedure can be implemented.
After completion of production with Grivory HT the screw, cylinder and melt distribution system should be cleaned out thoroughly.

Conditioning

The dimensions and the mechanical properties of Grivory HT products are only marginally influenced by moisture absorption. For testing purposes, parts can be stored in a climatic chamber until an increase in weight of 1.5 % has been achieved.