SupportDetail

LCP plastic molding technology

LCP plastic molding technology

【Date】:2014-03-05 【Hit】:7968
I. INTRODUCTION
    VECTRA (LCP) is a wholly aromatic liquid crystalline polyester having a unique chemical structure.
    Its chemical structure and the fine structure compared with ordinary polyester is very different, so the basic physical properties and processability are also unique .
    VECTRA (LCp) all have a thermoplastic , a commercially available ordinary injection molding machine for molding ( but need to have some level of corrosion and high temperature range of injection molding machine ). VECTRA (LCP) generally has a low viscosity when melted and cured when a high rigidity , but it exists in its anisotropic mechanical properties . following describes the basic methods VECTRA plastic injection molding areas , but special grades of molding problems need to be negotiated .
Second, the pre-drying
    VECTRA hygroscopicity is very small, such as equilibrium moisture content of polymer A level at 23 ℃, 50% RH condition was only 0.03% (300ppm) so because the polyester material is VECTRA , so even if a moisture-proof package , and should be pre-dried before molding .
    Proposal under 140 ~ 160 ℃, more than 4 hours ( up to 24 hours ) in dry conditions dried desiccant dryer .
    Frame can be used or a hot air dryer hopper dryer . Regardless of which , the hot air temperature and air volume should be adjusted such that the pellets can be obtained according to the above conditions uniformly dried in the particular case of hopper dryer , should be taken to prevent short track (short pass) phenomenon and ensure that pellet temperature ( rather than the set temperature ) to achieve the above temperature.
    In order to prevent re- absorption in the molding process , it is recommended to use the dryer hopper during molding .
Third, the use of recycled materials
    If the molding press molding conditions recommended , VECTRA will show good thermal stability under laboratory findings , even if 100% recycled five times , the static strength and elastic modulus can be 75 to maintain the initial value 90% Please note that repeatedly recycled material will darken slightly .


Notwithstanding the above experimental examples, but the amount of recycled materials or to remain at around 25% of the total is appropriate. This is because about 25% of the incorporation will greatly reduce the proportion of times the material back , so that the new material and a second material back the ratio remains at 93.8% in order to prevent the above-mentioned changes in hue , too, should take this approach.
    Regrind sizes can sometimes lead to measurement instability, involved gas bubbles etc. Therefore , the use of recycled material in the proposal and granulation (re-pellet), the material should be removed if using crushed oversized particles and crushed material powder to make a uniform particle size .
Fourth, choose molding machine
    VECTRA available ordinary screw -type molding machine for molding.
    Although the level of the cylinder temperature due VECTRA type varies, but generally does not exceed the estimated maximum temperature 380 ℃, therefore ordinary molding machine heating coil can be.
    In terms of the size of the plasticizing unit , an injection amount is preferably 50 to 75% of maximum injection molding machine .
    VECTRA available ordinary molding nozzle opening . Nozzle opening pressure loss is usually minimal and without considering the reliability of the mechanical action , so that the nozzle should be used , but due to the VECTRA has good flowability in order to obtain higher if flowability deliberately set very high cylinder temperature , the phenomenon occurs salivation .
    A nozzle with a heating coil should be controlled independently of the controller. So, salivation and drawing phenomenon , the lower the temperature of the nozzle will be an effective method , but if excessively lower barrel set temperature , the flow will deteriorate , filled sharp rise in pressure, the cold material and air bubbles into the product . shown in Figure 1 "LCP nozzles" can prevent drooling and stringing while not excessively decrease the temperature of the nozzle , thus helping to stabilize the molding .
    VECTRA has fast curing and good mold release characteristics , thus forming a short period can be an advantage in order to play , you should try to use the plasticizing ability of the molding machine screw shape generally follows the shape is appropriate . :
    ● front of the metering section of the screw fixing groove depth of several threads
    ● check valve intact
    ● grow feed formula ( transportation segment is longer , Long feeding type)
    Figure 1. LCP nozzle
    ● nozzle diameter is small (φ1 ~ 2mm)
    ● tip of the nozzle has a high-power heating coil
    ● set in front of the thermocouple




Five , mold design
    VECTRA anisotropic , so the mold design is necessary to comply with a variety of basic principles , but also consider this feature .
    The physical properties of the molded article depends on the degree of orientation and VECTRA itself and the filler material , and this is due to orientation of the shear force in the material flow , therefore , must combine the characteristics of the final product required to consider the material filling the mold cavity form . Generally , the thinner wall thickness , orientation more obvious . meet the characteristics of the molded product requirements, product designers should work closely with the mold designers .
    In addition, the weld lines at times unable to play VECTRA inherent advantage, so mold design should try to avoid weld lines .
1 . Mold material
    VECTRA less corrosive mold , mold material and therefore can be used for all standard and some filler materials are also subject to wear and tear will die , and you should choose the appropriate steel and filled with the same kind of treatment as filler material as ordinary molding material quenching and other measures taken .




2 . Runner
    Sorted by degree of processing is easy , then usually semicircular , trapezoidal and circular flow channel , and the cross-sectional area and pressure loss from the perspective of sort ( from good to bad ) , then was circular , trapezoidal and semicircular , it is recommended to use circular or trapezoidal channel , if considering economy, depending on the desired diameter of the top of the flow channel length of the flow path , product size , and therefore can not be generalized , but is usually 2 ~ 5mm. flow path length should be as short as possible . for multi-cavity mold , the mold cavity in order to reduce the difference between the best so that the distance between each cavity remains the same.
    Further, if the injection molding machine sprue nozzle diameter is much larger than the size occurs within a spray pattern sprue , involved air bubbles to this end , for the injection molding machine nozzle diameter , the minimum diameter of the proposed design of the sprue a nozzle diameter larger than about 0.5mm, and the slope is set to 0.5 ~ 1 °.
    VECTRA had a good releasability, but the mobility is also very good, if the mold surface has a wound , the wound will be transcribed and significantly reduce releasability . Wear can not be ignored and the sprue channel . Should the end of the flow channel and the main channel is set to prevent cold slug well inflow of cold material products .
3 . Runner
    In VECTRA mold design, gate design is particularly important.
    VECTRA the anisotropy , it is necessary to consider the position of the gate up to determine the base fill mode especially want to play in a particular direction VECTRA good characteristics of the product , the direction of flow as it should in principle .
    If the product of complex shape and direction of the process of filling the disorder , but also not too consider the impact of gate location .
    Side of the point , latent and other common gate way can be used.
4 . Vent
    VECTRA almost no gas during molding , the mold cavity is evacuated in order to fill air , the exhaust groove is still provided a good method with VECTRA exhaust groove depth to 1/100 ~ 2/100mm appropriate in the depth of the cross section is very small , the air flow will be restricted , thus not only provided at the exhaust air is easy to stay in the groove , the exhaust groove provided also in a wide range as possible.
Six , forming characteristics ( mobility, mold shrinkage , after shrinkage )
1 . Mobility
    VECTRA bar flow length in the thickness of 0.2 ~ 0.3mm 3 to 4 shown in FIG . Plastics and even compared with the general purpose engineering plastic ( not to mention the variety of super engineering plastics ) , can be obtained very long flow length of the rod , VECTRA fully demonstrated the advantages of . Figure 4 shows , even in the thin-walled (0.2mm) case can be easily obtained over the flow length of 30mm , which is very conducive to thin-wall molding . , please refer to the product design and mold design information .


2 . Molding shrinkage
    Table 3 and Figure 5-10 shows a representation of the various levels VECTRA molding shrinkage. The overall shrinkage is small , and therefore helps to maintain the correct product size especially the flow direction shrinkage is small , and the vertical shrinkage direction is greater if the molded shape of complex and disordered flow will actually take intermediate values ​​of both treated in order to determine the average shrinkage cavity size.












    . Simple shapes and values ​​are 5 to 10 are given in Table 3, the complex shape of the actual molded product may be slightly different values ​​obtained , but the absolute shrinkage is small , it may also be that the impact on the dimensional accuracy is small , but if a very strict dimensional accuracy of the product , and should be considered a pre- production test mode the correct measure shrinkage , estimated or corrected by formal mold cavity to determine shrinkage size.
3 . After shrinkage
    A130 resin at temperature 150 ℃ and 200 ℃ annealing time relationship with FIG shrinkage after 10 shown after about two hours of annealing is saturated after contraction , the shrinkage does not change .


Seven, molding conditions
1 . Barrel temperature
    Plain nozzle and barrel temperature as shown in Table 7-1 . This setting is a recommended standard can also be adjusted according to the state formed 10 ~ 20 ℃. To prevent the phenomenon of drawing and salivation , nozzle temperature can be lowered from 10 to . 20 ℃ , however , please note the following points :
• Reduce the barrel temperature : cold material plasticized lead to a decline or inadequate mechanical properties .
• Improve barrel temperature : Almost will not stay long residence time and produce a gel or corrosive gases in the barrel , but should reduce prolonged interruption molding barrel temperature , and should reboot several times before cleaning (shot purge).
    Adverse measure , it is recommended to set the barrel temperature set straight or backslash as shown below .
    ( Example ) For E130i
    (NH) 350 ℃ - 350 ℃ - 350 ℃ - 350 ℃ ( straight )
    (NH) 350 ℃ - 350 ℃ - 360 ℃ - 370 ℃ ( temperature raise the rear of the barrel )






2 . Mold temperature
    VECTRA recommended setting mold temperature in the range of 80 ~ 120 ℃. Mold temperature is 80 ℃, generally not a problem , but if there is a gloss surface finish appearance such problems , it is recommended to use high mold temperature .
3 . Plasticizing
    Screw speed is usually 100rpm, but can also be used to accelerate high- speed measurement cycles and improve stability .
    In order to prevent drooling and fiber breakage , we recommend backpressure set 0 ~ 2MPa.
4 . Injection pressure and injection speed
    VECTRA all levels are very low melt viscosity , and therefore can usually be much lower than the ordinary molding of the thermoplastic resin pressure for most of the molded article can be molded at a resin pressure of 15 ~ 45MPa Further , VECTRA curing speed soon, the good results obtained so rapid injection .
5. Molding machine stopping and switching on and materials
    ① molding stops
    Stop molding machine should be thoroughly cleaned of residual resin barrel .
    If the next molded using the same material , can be cleaned only , but if the next molded using different resins , the cleaning material should be switched at this time should be used can be adapted to a resin molding temperature before cleaning material . for example , the molding having the same VECTRA temperature and good thermal stability of the resin include polycarbonate containing glass fibers , high density polyethylene , commercially available acrylic and the like.
    VECTRA different levels of molding temperature vary greatly.
    It is noteworthy that the cleaning material varies by grade .
    ② forming the beginning
    If the resin in the barrel VECTRA molding temperature range is stable , can be directly heated to the molding temperature VECTRA then washed with VECTRA but VECTRA the melt viscosity is low, the residual resin in the cylinder is hard to completely cleaned out , so to thoroughly clean a simple and effective method is to use polycarbonate with glass fiber cleaning , then use VECTRA cleaning.
    If the residual resin in the molding temperature range is different VECTRA, the proposed cylinder barrel temperature is adjusted in the temperature of the residual molding resin , and then the residue was used in both the VECTRA resins and molding temperature can be used , and a resin having good thermal stability ( polycarbonate containing glass fibers , high density polyethylene , ( as the case may be ) and polycarbonate ) cleaning, then set VECTRA molding temperature and molding within the above temperature range as VECTRA stabilizing resin used for cleaning .
    If the barrel resin is VECTRA, can be directly heated to VECTRA molding temperature with VECTRA cleaning However , VECTRA molding temperature range due to class -specific, and should therefore be recognized that with a temperature range if the different temperatures , even VECTRA be cleaned are also the same as the molding temperature range of different resins .
When switching resin ③
    If the resin may be directly switched with VECTRA , reference may stop and start the molding method , while maintaining the cylinder temperature of a direct cleaning.
If the resin is not intact VECTRA switching, can be used and it is recommended to use a resin having good thermal stability ( glass fiber -containing polycarbonate in the handover between the VECTRA resin and the desired molding temperature , high-density polyethylene , etc. ) cleaned , and then set the molding temperature.
    Especially in the case where the switching and the residual resin VECTRA viscosity greater than VECTRA , since the switching is difficult, and therefore should be thoroughly cleaned .
    ④ Other
    If long-term stay in the barrel , VECTRA sometimes deteriorated into a foreign body , this time must be fully cleaned.
    If the black coloring agents and other dark -colored material is difficult to completely , it is recommended to use a polycarbonate containing glass fibers cleaning, followed by washing of polyethylene , and then alternately repeated between cleaning would be completely discharged after the cleaning material in the cartridge a cleaning material and then into the next , then the effect will be better.
    * When using a variety of materials to clean the clean machine , make sure each purging material MSDS.
Eight Safety Precautions
    As long as some of the industry´s compliance with forming basic safety precautions , VECTRA molding would not dangerous if hypoventilation , these decomposition occurred , but , like other plastics , VECTRA at high temperatures produces decomposition after being heated. sometimes it will accumulate and cause health damage , and therefore should be properly ventilated.
    To prevent thermal decomposition of the initiator and the gas pressure in the barrel should be level A, B, C, D / Rating Ei / class T, S , respectively, to control the resin temperature below 350 ℃ / 370 ℃ / 385 ℃. Since these temperatures much higher than ordinary molding temperature , so do not be heated to such high temperatures . If you want a short break forming, although can be placed at the molding temperature, but the boot will have to be fully cleaned again when if left for longer than 30 minutes, and should the molding temperature down about 50 ℃.
    Before feeding the pellets and the screw rotation , so that the cartridge should be sufficient so that the temperature of the heating time for each level of at least a molding temperature of -10 ℃. Operating personnel should wear goggles ( especially during cleaning ) The operation of the mold is very hot protective gloves should be used . pause during molding , injection devices should be made so as to avoid contact with the mold back nozzle resulting cured .

Previous:Injection molding machine temperature is too high causes and treatment
Next:Encyclopedia of plastic shrinkage
<<Back

Phone
0769-82834131