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Compression Molding
Compression moulding is a composite manufacturing process normally used to produce composite components in high production volume such as automotive components. There are two types of compression moulding process, i.e., cold compression and hot compression moldings. In this process, for thermosetting matrices, normally an intermediate material called moulding compound is used. It is really a semi-cured composite. Sheet moulding compound and bulk moulding compound (BMC) are two widely used thermosetting-based moulding compounds. For thermoplastic polymer, moulding compound normally used is glass mat thermoplastics (GMT). For preparing composite specimens in the laboratory scale compression moulding, composite pellets are normally prepared using internal mixer and twin screw extruder. In compression moulding process, pressure is applied in cold compression and pressure and temperature in hot compression moulding after the moulding performs are placed in a mould cavity. In cold compression moulding, curing process takes place at room temperature while for hot press it takes place by applying heat to the mould and it in turn being transferred to the composites. Matrices used in this process include UP, vinyl ester and phenolic for thermosetting polymers while among the thermoplastic polymers, PP, polyamide, and PEEK can be used.Get more news about compression moulding machine,you can vist our website!
Wirawan et al.53 and El-Shekeil et al.54 used laboratory scale compression moulding (Figure 6) to prepare composite specimens from sugar cane bagasse and PVC, and kenaf and TPU, respectively. The intermediate materials were made using internal mixer. The intermediate materials were placed into the mould and the heat and pressure were applied to form the composite plates. Hot pressing was then carried out at a temperature around 170 ° C for 12.5 min and the mixture was cooled under pressure to room temperature. The mechanical and thermal properties of the composites were then determined.
Compression molding is widely used and a fairly simple method where materials ready to be processed are placed between two aluminum plates using mylar sheets and then pressed between preheated metal plates at controlled temperature and pressure. An example of the hemp-reinforced wheat gluten plastic is given in the succeeding text (Fig. 15.2). Compression molding is a high-volume molding method that provides fast cycle times and high part homogeneity and allows molding of metal inserts, grooves, and holes in the part. In compression molding processes, many materials are used, including sheet molding (SMC), bulk molding (BMC), thick molding (TMC), and wet molding (also known as liquid molding or cold molding). In the compression molding process, the heated matched metal mold set is mounted in a large hydraulic press. A preweighed molding compound mold is loaded into the mold, and the press is closed. The material cures rapidly under the set pressure and pressure of the tool [9].
Compression molding is the most common thermoset and thermoplastic polymer composite manufacturing process. It is normally used to produce composite components in high production volume such as automotive components. Basically, there are two types of compression molding processes: cold and hot.
For thermoset polymers, intermediate semi-cured composite material called a molding compound is used. Bulk molding compound (BMC) and sheet molding compound (SMC) are two widely used thermosetting-based molding compounds.
For thermoplastics polymers, a glass mat thermoplastic (GMT) is normally used as molding compound. In the laboratory scale compression molding, composite materials are mixed in an internal mixer and twin screw extruder for homogeneous distribution.
For the two types of the compression molding processes, only pressure is applied for the cold press technique, but in the hot press technique pressure and temperature both are required. Cold pressure technique requires room temperature for curing process, while a hot press technique applies temperature on the mold; it then transfers the heat to the composite and initiates the curing process