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Thread: Polymer Processing Techniques

  1. #1
    Friendly Member eikhinewai
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    Polymer Processing Techniques

    In chemical engineering, it also study about plastic and rubber.
    Among these, there are various kinds of polymer processing techniques.
    1.Extrusion
    2.Injection Molding
    3.Blow Molding
    (a) Extrusion-Blow molding
    (b) Injection Blow Molding
    (c) Stretch-Blow Molding

    4.Thermoforming
    5.Vacuum forming
    6.Compression and Transfer Molding
    7.Rotational Molding
    The first three polymer processing techniques are more popular than others.

    Extrusion

    Advantages

    · Parts of infinite length can be produced

    · Some parts, like blown film, can only be made with extrusion

    · Extrusion is a continuous process capable of very large production volumes

    · Most thermoplastics, and some thermosets can be extruded

    Disadvantages

    · Since the dies contain no moving parts, only continuous cross sections can be manufactured

    · Complex geometry cannot be produced

    · Complicated feature can be very hard to produce because of difficulties in producing a balanced die

    Application

    apply in food processing

    Injection Molding Machine


    Injection molding machine also known as presses, holds the mold in and components are shaped inside it. Presses are rated by tonnage, which expresses the clamping force that the machine can generated. This pressure keeps the mold closed during the process. Tonnage can vary from less than 5 tons to 6000 tons.
    The injection molding equipment or machine has three basic components (functional units) (1) injection units (plasticator), (2) mold, and (3) clamping unit.
    The function of plasticator is to prepare the proper plastic melt and through the injection unit transfers the melt into the next component that is mold. The clamping system closes and opens the mold. The machine perform certain essential functions –
    1. Plasticizing: heating and melting of the plastic in the plasticator.
    2. Injection: injecting from the plasticator under pressure a controlled volume shot of melt into a closed mold, with solidification of plastics beginning on the mold’s cavity wall.
    3. After filling: maintaining the injecited material under pressure for a specified time to prevent back flow of melt and to compensate for the decrease in volume of melt during solidification.
    4. Cooling: cooling the thermoplastic (TP) molded part in the mold until it is sufficiently rigid to be ejected until it is sufficiently rigid to be ejected or heating: heating the thermoset (TS) molded part in the mold until it is sufficiently rigid to be ejected.
    5. Molded part release: opening the mold, ejecting the part, and closing the mold so it is ready to start the next cycle with the shot of melt.


    Injection molding processes

    1. The mold is first closed as its two halves come together.
    2. The nozzle moves toward the mold, until the parts adjoin.
    3. The material is injected into the mold via a hole in the mold, called the sprue.
    4. The mold is cooled before the product is ready to be ejected.
    5. The material at the end of the screw is decompressed and the shot size of the material is metered.
    6. The mold opens.
    7. The part is ejected.

    Advantages

    • High production rates
    • Design flexibility
    • Repeatability within tolerances
    • Can process a wide range of materials
    • Relatively low labor
    • Little to no finishing of parts
    • Minimum scrap losses

    Disadvantages

    • High initial equipment investment
    • High startup and running costs possible
    • Part must be designed for effective molding
    • Accurate cost prediction for molding job is difficult




    Applications

    It can apply from micro parts to large components such as bumpers and wheelie bins.
    Containers, household goods, auto components, electronic parts, flower pots.

    mold က ေစ်းၾကီးေသာ္လည္း injection molding ကုိအသံုးမ်ားပါတယ္.. အမ်ဳိးမ်ိဳးထုတ္လုိ ့ရလုိ ့ပါ.. ေက်ာင္းမွာ တစ္ခါႏွစ္ခါေလာက္ေတာ့ practical လုပ္ဖူးပါတယ္.. machine က control လုုုပ္ရတာသိပ္မခက္ပါဘူး..

    Thermoforming

    Advantages
    • [li]
      large forming
      thin-wall packing
      short-run or prototype products[/li]
      [li][/li]

    Disadvantages
    • [li]Poor material distribution: the wall thickness varies and is difficult to control
      Consider finishing is required and considerable waste
      the polymer has to heated twice, once to form the sheet (extrusion) and again during vacuum forming
      the range of shapes available is limited[/li]
      [li][/li]

    Applications

    The largest application is for food packaging such as toiletries, pharmaceuticals, electronics.
    Food related applications are meat trays, microwave and deep freeze containers, ice-cream and margarine tubs, snack tubs, sandwich packs and vending drink cups.
    Other non-food applications include manufacturing collation trays and blister packaging.

    Vacuum forming

    Advantages
    • [li]economical for small to medium production runs
      low tooling costs
      quick startup
      high strength to weight ratio
      efficient prototyping
      no need for painting; the color and texture are formed in[/li]
      [li][/li]

    Process

    1. The heated plastic sheet is clamped and sealed across the pressure box.
    2. Control air pressure blows the bubble, giving the pre-stretch of 35-40%.
    3. The plug is moved down into the bubble; air-pressure keeps the bubble and the plug contact.
    4. The plug is lowered to its final position, a vacuum is pulled between plug and sheet, and the pressure in the pressure box causes the sheet to take up the shape of the plug.


    Applications

    Baths and shower trays, ski-boxes, refrigerator liners, parts of vehicle cabs, sandwich boxes, exterior shop signs

    Blow Molding

    1. Extrusion-Blow Molding

    Advantages

    low initial mold tooling costs
    flexibility of tooling
    flexibility in production: Neck inner diameters (I.D) can easily controlled to varying requirements. Bottle weights are adjustable.
    container sizes can range from less than 1 oz. to 55 gallons and up
    container shape is not restricted by blow-up ratios. Bottles can be long and flat or have handles.
    wide selection of machine sizes: Molds can geared to volume requirements


    Applications


    bottles and containers
    automotive fuel tanks
    venting ducts
    watering cans
    boat fenders

    Injection Blow-Molding


    Process steps

    step.1 Injection
    step.2 Blowing
    step.3 Ejection

    Applications

    Pharmaceutical products, consumable bottles

    Stretch-Blow Molding


    Applications

    Carbonated and soft drink bottles
    Cooking oil containers
    Bathroom and toiletry products


    Compression and Transfer Molding

    Advantages

    The polymer flows over shorter distance, thus reducing frozen in stress
    Polymer is not forced through small gates which can lead to points of weakness in a molding.
    Low mold maintenance costs.
    Mold design is not complicated by spruce and runner layout
    Its ability to mold large and fairly intricate parts

    Disadvantages

    Offers least product consistency
    Difficult to control flash
    Not suited for some types of parts

    Applications

    superior lighting

    Rotational Molding

    Advantages

    economically produced large products
    minimum design constraints
    stress-free products
    no polymer weld lines
    comparatively low mold costs

    Applications

    rainwater tanks
    diesel fuel tanks
    traffic cones

    [move]အမွားရွိလ်ွင္လည္းျပင္ဆင္ေပးၾကပါ..... [/move]

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  3. #2
    Friendly Member eikhinewai
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    ျပန္စာ -> Polymer Processing Techniques

    အခ်ိန္္္အားရင္ တစ္ခုခ်င္း အႀကာင္းကို ဆက္လက္ ေဖာ္ျပသြား ပါဦးမယ္...............

    အခုေတာ့ စာဖတ္လုိက္ ဦးမယ္

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    Newbie wailynn
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    ျပန္စာ -> Polymer Processing Techniques

    ဆက္ေရးပါအံုး frodo ရ
    မအားဘူးထင္တယ္... အားရင္ဆက္ေရးေနာ္ ...


  5. #4
    Newbie nayzaw3053 is an unknown quantity at this point
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    ယေန႕ေခတ္ အခ်ိန္အခါတြင္ polyethylene ကို plastic production နယ္ပယ္အသီးသီးတြင္ က်ယ္ျပန္႕စြာ အသုံးျပဳလ်က္ရွိသည္ကုိေတြ႕ရသည္။ polyehtylene ကုိ High,low, medium pressure သုံးမ်ိဳးတြင္ polymerization(ပုိလီမာျပဳလုပ္ျခင္း) လုပ္ႏူိင္သည္။ polyethylene ျပဳလုပ္ရာတြင္ အေျခခံအားျဖင့္ ethylene ကုိ method အမ်ဳိးမ်ိဳးျဖင့္ structure and properties မ်ားပုိမုိတုိးတက္ေကာင္းမြန္ေအာင္ျပဳလုပ္ျခင္းျဖင့္ ျပဳလုပ္ႏူိင္သည္။ Method တစ္ခု၏ေအာက္တြင္ပင္ temperature, pressure စသည့္ condition မ်ားေပၚတြင္ မူတည္၍ မူကြဲ products မ်ားထြက္ႏူိင္ေသးသည္။ အဓိက အားျဖင့္ structure and properties မ်ား ကြဲျပားႏူိင္သည္။
    High pressure ေအာက္တြင္ ethylene ကုိ polymerization ျပဳလုပ္၍ ရရွိေသာ polyethylene ကုိ Low Density Polyethylene LDPE ဟုေခၚသည္။
    pressure range မွာ 100 မွ 300 MPa ျဖစ္သည္။ polymerization method မွာ မ်ားေသာအားျဖင့္ vinyl compound မ်ားပါ၀င္ေသာ Free Radical Mechanism method ကုိ အသုံးမ်ားပါသည္။ ဤနည္းတြင္ ေတြ႕ရေသာ ထူးျခားခ်က္မွာ concentration of monomer သည္ ရရွိလာေသာ product ၏ molecular mass ကုိ လႊမ္းမုိးသည္ဟူေသာ အခ်က္ျဖစ္သည္။ conc ျမင့္ေသာ monomer မ်ားကုိ အသုံးျပဳလွ်င္ high molecular polyethylene ကုိရရွိမည္ျဖစ္သည္။ polymerization ျပဳလုပ္စဥ္အတြင္း pressure သည္လည္း process ကုိ လႊမ္းမုိးမႈရွိေနသည္။ pressure ျမင့္ေလ product ၏ density ျမင့္တက္လာေလျဖစ္သည္။ tempreature ကုိ ေလွ်ာ့ခ်ျခင္းအားျဖင့္လည္း density of polyethylene ကုိ ျမွင့္တင္ေပးႏူိင္ပါသည္။ ဤ process ကုိ Temperature 80 မွ 300 C ၾကားတြင္ျပဳလုပ္ပါသည္။
    (ဒီေခါင္းစဥ္ေလးေတြ႕လုိ႕ ဒီေအာက္မွာပဲ ၀င္ေရးျဖစ္သြားပါသည္။ ၾကဳံရင္ၾကဳံသလုိ ၀င္ေရးသြားပါဦးမည္။)

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  7. #5
    Special Member konge will become famous soon enough konge's Avatar
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    ေက်းဇူးပါဗ်ာ.. အတတ္ပညာ အေတြ႔အၾကံဳ ပညာရပ္ ေတြမွ်ေ၀တဲ့အတြက္။
    လိုခ်င္တာေတြကိုနည္းနည္းေလ်ာ့လိုက္ပါအားလံုးအဆင္ေျပသြားပါလိမ့္မယ္

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    Newbie nayzaw3053 is an unknown quantity at this point
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    ပုိလီမာအမ်ိဳးအစားမ်ားထဲမွ ဟုိင္ဒရုိဂ်င္ႏွင့္ ကာဘြန္ႏွစ္မ်ိဳးထဲသာေပါင္းစပ္ထားေသာပုိလီမာမ်ားကို polyolefin ဟုေခၚသည္။
    polyethylene သည္လည္း polyolefin အုပ္စုထဲတြင္ တစ္ခုအပါအ၀င္ျဖစ္သည္။ ထုိပုိလီမာမ်ားသည္ semi-crystalline ပုိလီမာမ်ားျဖစ္သည္။
    ဆုိလုိသည္မွာ ပုိလီမာမ်ားသည္ လုံး၀ crystall ျဖစ္သြားသည္ဟုမရွိေပ။ ပုိလီမာမ်ားတြင္ amorphous အေျခအေနသည္ အနည္းႏွင့္အမ်ားရွိေနတတ္သည္။
    ပုိလီအီသုိင္လင္းမွာ လူသိမ်ားေသာ ပုိလီမာျဖစ္သည္။ ၄င္း၏ ကမ္မစ္ကယ္ ေဖာ္မ်ဴလာမွာ (CH2-CH2)n ျဖစ္သည္။ PE ပုိလီအီသုိင္လင္းသည္ non polar material
    ျဖစ္သည္။ ဆုိလုိသည္မွာ ၄င္းသည္ common solvent and hardly swells မ်ားတြင္ မေပ်ာ္၀င္ပါ။ ထုိ႕ေၾကာင့္ ပုိလီအီသုိင္လင္းမွ ထုတ္လုပ္ေသာ ပုိက္မ်ားအခ်င္းအခ်င္းဆက္
    သည့္ေနရာတြင္ ေကာ္ သုိ႕ အရည္ cement တစ္ခုခုႏွင့္ဆက္၍မရပါ။ ဤေနရာတြင္ အသင့္ေတာ္ဆုံးနည္းလမ္းမွာေတာ့ အပူေပး၍ဆက္ျခင္းျဖစ္သည္။ လွ်ပ္စစ္ႏွင့္ ဆက္ျခင္း
    အနီေအာက္ေရာင္ျခည္သုံး၍ဆက္ျခင္းစေသာနည္းလမ္းမ်ားလည္းရွိေသးလည္။
    ပုိလီအီသုိင္လင္းကုိ ပုိက္မ်ားျပဳလုပ္၍အသုံးျပဳျခင္းျဖင့္ေအာက္ပါအက်ိဳးေက်းဇူးမ်ားရရွိႏူိင္သည္။
    ၁-တပ္ဆင္အသုံးျပဳခသက္သာျခင္း
    ၂-အေလးခ်ိန္ေပါ့ပါးျခင္း
    ၃-အပူခ်ိန္ကုိ -၅၈ မွ ၁၄၀ ဒီဂရီဖာရင္ဟုိက္ၾကားတြင္ ခံႏူိင္ရည္ရွိျခင္း
    ၄-ေကြးႏူိင္ဆန္႕ႏူိင္ေသာ ေပ်ာ့ေျပာင္းမႈရွိျခင္း
    ၅-ပြန္းပဲ့ဒဏ္ကုိ ေကာင္းစြာခံႏူိင္၇ည္ရွိျခင္း
    ၆-ပြတ္တုိက္မႈဒဏ္ကုိလည္းေကာင္းစြာခံႏူိင္ရည္ရွိျခင္း (ပုိက္ထဲတြင္ အရည္မ်ားျဖတ္သန္းစီးဆင္းေသာအခါ)
    ၇-ကမ္မစ္ကယ္ ပစၥည္းမ်ားျဖတ္သန္းစီးဆင္းရာတြင္လည္း က်ယ္ျပန္႕စြာ အသုံးျပဳႏူိင္ျခင္း
    ၈-အပူေပး၍ပုိက္ဆက္ေသာအခါမ်ားတြင္လည္း လြယ္ကူလုံျခဳံမႈရွိျခင္း
    ပုိလီအီသုိင္လင္း မ်ားထဲတြင္ ပုိလီအီသိုင္လင္းအမွတ္ ၁၀၀ သည္ ပုိက္မ်ားထုတ္လုပ္ရာတြင္ က်ယ္ျပန္႕စြာအသုံးျပဳသည္။ ၄င္းကုိ PE 100
    ဟု လြယ္ကူစြာ ေခၚေလ့ရွိသည္။ ေမာ္ဒန္ PE 100 မ်ားသည္ bimodal ေမာ္လီက်ဴးမ်ားျဖင့္ ဖြဲ႕စည္းထားသည္ကမ်ားသည္။ ဆုိလုိသည္မွာ ၄င္း ပုိလီမာထဲတြင္
    မတူညီေသာ ေမာ္လီက်ဴးဆက္တန္းႏွစ္မ်ိဳးပါသည္။ ေမာ္လီက်ဴးဆက္တန္းအရွည္ႏွင့္အတုိျဖစ္သည္။ ထုိကဲ့သုိ႕ေသာ ပုိလီမာမ်ားမွျပဳလုပ္ေသာ ပစၥည္းမ်ားသည္
    ဆြဲဆန္႕ႏူိင္အား ေတာ္ေတာ္ေလးျမင့္မားသည္။ ထုိ႕အျပင္ ကြဲအက္ျခင္း က်ိဳးေၾကျခင္းမ်ားလည္းေတာ္ရုံႏွင့္မျဖစ္ေပၚႏူိင္ပါ။ ထုိ႕အျပင္ ၄င္းပုိလီမာသည္ ၄င္းခံႏူိင္ရည္ရွိေသာ
    အပူအခ်ိန္အတုိင္းအတာတစ္ခုအတြင္းတြင္ ျပင္ပ မွသက္ေရာက္ေသာ ဒဏ္မ်ားကုိလညး္ေကာင္းစြာခံႏူိင္သည္။ လက္ေတြ႕နယ္ပယ္တြင္တုိင္းတာခ်က္မ်ားအရ ပုိလီအီသုိင္လင္း
    ၁၀၀ သည္ မ်က္ႏွာျပင္ထိခုိက္မႈတြင္ အညွာလြယ္ေသာ အမ်ိဳးအစားမဟုတ္ေပ။
    Bimodal PE မ်ားသည္ non polar သဘာ၀မ်ားျဖစ္သည္။ non polar ဆုိသည္မွာ ေမာ္လီက်ဴးအတြင္း အက္တမ္မ်ားအခ်င္းအခ်င္း တူညီေသာ အီလက္ထရြန္ကုိ
    ရွယ္ထားသည္။ ထုိသေဘာသဘာ၀ေၾကာင့္ ၄င္းပုိလီမာမ်ားသည္ ကမ္မစ္ကယ္ပစၥည္းမ်ား၏သက္ေရာက္မႈကုိေကာင္းစြာခံႏူိင္ရည္ရွိသည္။ ပိုလီအီသုိင္လင္းသည္ အက္စစ္မ်ား
    အယ္လ္ကာလုိင္းအရည္မ်ား၊ ေပ်ာ္ရည္အမ်ိဳးမ်ိဳးႏွင့္ အရက္မ်ား ေရမ်ားတြင္ မေပ်ာ္၀င္ႏူိင္ပါ။ အဆီမ်ားကေတာ့ ပုိလီအီသုိင္လင္းကုိ အနည္းငယ္ပြေရာင္းေစႏူိင္သည္။ ပုိလီအီသုိင္လင္း
    သည္ oxydizing acids ketones aromatic hydrocarbon chlorinated hydrocarbon စသည္မ်ား ကုိေတာ့ခံႏူိင္ရည္မရွိေပ။
    စမ္းသပ္ေတြ႕ရွိခ်က္မ်ားအရ ပုိလီအီသုိင္လင္းသည္ သံႏွင့္အျခားပလပ္စတစ္ မ်ားထက္ပုိ၍အသုံးျပဳရတာ အဆင္ေျပပါသည္။ ၄င္းမွျပဳလုပ္ထားေသာ ပုိက္မ်ားသည္
    အရည္အမ်ဳိးမ်ိဳးသယ္ယူပုိ႕ေဆာင္ေရးတြင္ က်ယ္ျပန္႕စြာအသုံးျပဴသည္။ အျခားပလပ္စတစ္ပစၥည္းမ်ားကဲ့သုိ႕ပင္ ပုိလီအီသုိင္လင္းသည္လည္း ေနေရာင္ျခည္မွ UV ray ႏွင့္
    ေအာက္ဆီဂ်င္ တုိ႕ေၾကာင့္အနည္းငယ္ထိခုိက္မႈမ်ား အရည္အေသြးက်ဆင္းမႈမ်ားျဖစ္ႏူိင္သည္။ ၄င္းျပသနာကုိ carbon black ကုိ ပုိလီမာအတြင္းေပါင္းစပ္ေပးျခင္းျဖင့္ UV
    exposure ကုိ ခံႏူိင္ရည္ရွိေစသည္။
    ပုိလီအီသုိင္လင္းပုိက္မ်ားကုိ အပူခ်ိန္ -58 မွ 140 ဒီဂရီဖာရင္ဟိုက္ၾကားတြင္ အသံုးျပဳႏူိင္သည္။ ၄င္း၏အပူေလွ်ာက္ကူးမႈႏႈန္းမွာ 2.7BTU-in/sqft/hr/deg F ျဖစ္သည္။
    ဤကဲ့သုိ႕ အပူခ်ိန္ကုိေကာင္းစြာ ခံႏူိင္ရည္ရွိေသာေၾကာင့္ ပုိလီအီသုိင္လင္းပုိက္မ်ားသည္ အျခား စတီးလ္ သံ စသည္မ်ားကဲ့သုိ႕ အပူအတြက္ထပ္မံ၍ ကာထားရျခင္းမ်ားစသည္ အေထြအထူးမလုိအပ္ပါ။ ထုိအခ်က္ကလည္း
    စီးပြားေ၇းအရ တြက္ေျခကုိက္မႈတစ္ခုလည္းျဖစ္လာသည္။ ပုိလီအီသုိင္လင္းသည္ ေအာက္ဆီဂ်င္ 17% ထက္ေက်ာ္ေသာ အေျခအေနတြင္ မီးေလာင္လြယ္ေသာ ပစၥညး္တစ္ခုျဖစ္သည္။ ပုိလီအီသုိင္လင္းမီးေလာင္ေသာအခါ
    အဆိပ္ရွိဓာတ္ေငြ႕မ်ားထြက္ႏူိင္သည္။ အထူးသျဖင့္ ကာဗြန္မုိေနာက္ဆုိဒ္ သည္ လူတုိ႕အတြက္ အဆိပ္ျပင္းေသာ ဓာတ္ေငြ႕တစ္မ်ိဳးျဖစ္သည္။
    ပုိလီအီသုိင္လင္းသည္ အပူခ်ိန္ 662 ဒီဂရီဖာရင္ဟုိက္တြင္ကုိယ္တုိင္မီးေလာင္ႏူိင္သည္။
    ပုိလီအီသုိင္လင္းသည္ အရည္စုပ္ယူမႈအားလည္း အလြန္းနည္းသည္။ ထုိ႕ေၾကာင့္ ၄င္းကုိယ္တုိင္သည္ လွ်ပ္စစ္စီးဆင္းမႈမရွိေပ။ ထုိ႕အတြက္ေၾကာင့္ ၄င္းအတြက္
    ျပင္ပ လွ်ပ္ကာပစၥည္းမ်ားထပ္မံအုပ္ကာေပးရန္မလုိအပ္ေပ။
    မွတ္ခ်က္=ရုရွားဘာသာမွ ျပန္ဆုိပါသည္။

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    PVC pipe production ေလးအေၾကာင္းသိသူမ်ား ေ၇းေပးၾကပါ

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