Plastics and Composite Materials: Forming and Shaping

Plastics and Composite Materials: Forming and Shaping

1. Extrusion

   • Screws have three distinct sections
     • Feed section: Conveys the material from the hopper into the central region of the barrel
     • Melt section, also called compression or transition section: Where the heat generated by the viscous shearing of the plastic pellets and by the external heaters around the barrel cause melting to begin3
     • Metering or pumping section: Where additional shearing and melting occur, with pressure building up at the die entrance

2. Processing Polymer-matrix Composites

   • Fiber Impregnation
     • Prepregs
       • In a typical procedure for making fiber-reinforced plastic prepregs (meaning pre-impregnated with resin), the continuous fibers are aligned and subjected to a surface treatment to enhance the adhesion to the polymer matrix

3. Blow Molding

   • proses manufaktur plastik untuk membuat produk-produk berongga (botol) di mana parison yang dihasilkan dari proses ekstrusi dikembangkan dalam cetakan oleh tekanan gas. Pada dasarnya blow molding adalah pengembangan dari proses ekstrusi pipa dengan penambahan mekanisme cetakan dan peniupan

4. Thermoforming

   • ThermoformingThermoforming is a process for forming thermoplastic sheets or films over a mold through the application of heat and pressure
     • Plastik termoset tidak bisa diproses secara pembentukan termal karena pemanasan tidak bisa melunakkan termoset akibat rantai tulang belakang molekulnya saling bersilangan. Contoh produk yang diproses secara pembentukan termal adalah nampan biskuit dan es krim

5. Casting

   • Compared to other methods of processing plastics, casting is a slow, but simple and inexpensive
   • Potting
     • Potting is carried out in a housing or case, which becomes an integral part of the component.
   • Encapsulation
     • the component is coated with a layer of the plastic, surrounding it completely and then solidifying.

6. Injection Molding

   • Injection molding is similar to hot-chamber die casting. The pellets or granules are fed into the heated cylinder, and the melt is forced into the mold, either by a hydraulic plunger or by the rotating screw system of an extruder. As in plastic extrusion, the barrel (cylinder) is heated externally to promote melting of the polymer. In injection-molding machines, however, a far greater portion of the heat transferred to the polymer is due to frictional heating
     • • a runner inject plastic into the cavities of an injection mold
       • Plastik leleh diinjeksikan dari barrel ke dalam mold melalui sprue. Dari sprue alirannya dibagi ke beberapa runner, kemudian melalui gate material memasuki rongga (cavity) di mana produk terbentuk. Setelah itu material akan didinginkan oleh cairan bersirkulasi.
   • Pultrusion
     • is a process for making long parts with various uniform cross sections such as rods, tubing that are made continuously. The sequence includes continuous reinforcements where the bundle is pulled first through a thermosetting polymer bath, then through a performing die, and finally through a heated steel die
     • untuk membuat bahan komposit yang kuat tetapi ringan,
     • Batang digunakan pada struktur atap, jembatan.
   • Pulforming
     • Continuously reinforced products other than those with uniform cross sectional profiles are made with this process. After being pulled through the polymer bath, the composite is clamped between the two halves of a die and cured into a finished product

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