Introduction

Plastic is a synthetic material made from polymers, which are large molecules composed of repeating subunits. These forms can be liquid or paste like resins for embedding, coating, and adhesive bonding, or they can be moulded, laminated, or formed shapes, including sheet, film, or larger-mass bulk shapes. It can be moulded into various shapes and forms, making it a versatile material widely used in electrical insulation, packaging, construction, and many other industries. Powermat uses two type of polymer, thermoplastic and thermoset plastics.

Thermoplastic: Plastics that can be deformed easily upon heating and can be bent easily. Linear polymers and a combination of linear and cross-linked polymers come under thermoplastics. Example: PVC, nylon, polythene, etc.

Thermosetting: Plastics that cannot be softened again by heating once they are moulded. Heavily cross-linked polymers come under the category of thermosetting plastics. Example: Bakelite, melamine, Sheet Moulding Compound & Dough Moulding Compound. 2. Thermoset Composite Material & its Moulding Technique Composites are defined as “a combination of plastic resin and fibre reinforcement.” Another term for composites is used in the past is reinforced plastics.

Thermoset Composite Material & its Moulding Technique

Composites are defined as “a combination of plastic resin and fibre reinforcement.” Another term for composites is used in the past is reinforced plastics.

Sheet Moulding Compound : Sheet moulding compound (SMC) or sheet moulding composite is a ready to mould glass fibre reinforced polyester material primarily used in compression moulding.[1] The sheet is provided in rolls weighing up to 100 kg. Alternatively, the resin and related materials may be mixed on site when a producer wants greater control over the chemistry and filler.

Process : Sheet Moulding Compound (SMC) is a compression moulding compound often used for larger parts where higher mechanical strength is needed. SMC is a fibre reinforced thermoset material. Glass reinforcement is between 10% and 50%, and glass length is slightly longer than Dough Moulding Compound (DMC) - between 1/2-inch and 1-inch (25mm).

Thermoset Sheet Moulding Compound (SMC) is a mixture of polymer resin, inert fillers, fiber reinforcement, catalysts, pigments and stabilizers, release agents, and thickeners and possesses strong dielectric properties. Manufacture of sheet moulding compounds is a continuous in-line process. The material is sheathed both top and bottom with a polyethylene or nylon plastic film to prevent autoadhesion. The paste is spread uniformly onto the bottom film. Chopped glass fibers are randomly deposited onto the paste. The top film is introduced and the sandwich is rolled into a pre-determined thickness.

The sheet is allowed to mature for 48 hours. Sheet moulding compounds can be moulded into complex shapes. Superior mechanical properties and surface appearance, plus excellent electrical insulation make this thermoset material ideal for automotive Class A body panels, high-strength electrical parts, business equipment cabinets, personal watercraft, and various structural components.

Dough Moulding Compound

Dough Moulding Compound (DMC) is a thermoset plastic resin blend of various inert fillers, fiber reinforcement, catalysts, stabilizers, and pigments that form a viscous, 'puttylike' moulding compound. DMC is highly filled and reinforced with short fibers. Glass reinforcement represents between 10% and 30%, with glass length typically between 6mm to 12mm. Depending on the end-use application, dough moulding compounds are formulated to achieve close dimensional control, flame and track resistance, electrical insulation, corrosion and stain resistance, superior mechanical properties, low shrink, and colour stability. Its excellent flow characteristics, dielectric properties, and flame resistance make this thermoset material wellsuited to a wide variety of applications requiring precision in detail and dimensions as well as high performance.

Process

Basic raw materials are resins, additives, catalysts, mould release agents and fillers. For coloured compounds, a pigment is added to the paste. The paste is then mixed with fibres, usually glass fibres. Bulk Moulding Compound (BMC) is prepared in a mixer. After preparing a base paste it will be loaded into the mixing device. Then all other ingredients are added and homogenized. The compound is packed into bags until moulding. To avoid any material changes during storage and transport it is packaged in a styrene tight packaging.

Process Used for Moulding SMC & DMC Composite Materials

Compression Moulding require following components:

1. Component raw materials SMC is available in Sheet form; DMC is available in dough form & Metal inserts if required

2. Mould with desired shaped cavity

3. Moulding Machine The machine is the fundamental element of this process. A compression moulding machine is like a power press except power press have a fast operation and do not stay for more time at stroke. CM machines stay for a predetermined time when actuated. It is more like a UTM machine. According to the shape and volume of the finished product, machine tonnage is decided. We have machines from 25 ton to 500 ton.

4. Process Flow

• Heating the Mould (temperature 165 deg C maximum)
• Placing the material in the cavity & close the mould
• Curing Reaction depends on the shape & volume of the raw material.
• Mould opening & Ejection.
• Cleaning the Mould for next operation.
• Post moulding operation for deflashing.
• Quality check of moulded products
• Packing and dispatch

Thermoplastic Material & its Moulding Technique

All the plastic materials which can be softened and melted by heating, but they set again when cool are called thermoplastics. Many thermoplastic polymers are reinforced with fibres. Reinforcement is used to improve physical properties - specifically heat deflection temperature. Glass fibres are the most used reinforcing material. The wear resistance and abrasion resistance of thermoplastic polymers are improved using aramid reinforcing. Although fibres can be used with any thermoplastic polymer, the following are the most important.

• Polyamide polymers use glass fibres to control brittleness. Tensile strengths are increased by a factor of three, and heat deflection temperature increases from 150 to 500oF.
• Polycarbonate compounds using 10, 20, 30 and 40% glass fibre loading have their physical properties greatly improved
• Other polymers benefiting from the addition of glass fibres include polyphenylene sulphide, polypropylene and polyether sulfone.

Process Used for Moulding Thermoplastic Materials:

The thermoplastic injection moulding process starts with the addition of pellets to a hopper. Thereafter, the material is passed through a heated barrel where the rotation of the screw initiates a shearing action causing the pellets to melt. The material is pushed at high pressure such that the mould cavities are filled. Once the cooling cycle ends, the mould is opened to release the moulded parts manufactured by thermoplastic injection moulding process.

Steps:

Injection moulding requires following component.

• Clamping unit is described in terms of machine tonnage.
• Mould for the desired shape.
• Injection Unit for injecting the molten material into the mould.
• Dwelling and cooling unit allows the molten material to settle & holding pressure is used to replace injection pressure in this step to compact the molten plastic during its solidification.
• Ejection Process, the cooled part is separated from the mould in this stage.
• Trimming process, the last stage where the excess cooled plastic material is trimmed from the finished part.

Difference between Thermoplastic Injection Moulding & Thermoset Mouldings

Thermoplastic Injection Moulding vs. Thermoset Moulding The way thermosets are made differs from thermoplastics in several aspects, and both the categories require varied treatment during the injection moulding process. Included below are a few differences when moulding thermosets and thermoplastics.

Testing on Moulded Parts

Following testing is done on the moulded products on regular basis in accordance with the international & national standards & the criterion of acceptance is to achieve or exceed the defined values.

1. Mechanical Testing Includes

Following testing is done on the moulded products on regular basis in accordance with the international & national standards & the criterion of acceptance is to achieve or exceed the defined values.

• Cantilever / Bending Testing
• Tensile / Pulling Testing
• Torque Strength
• Shear Testing
• Compressive Strength

Universal Testing Machine

Torques Tester

Compressive Strength

2. Electrical Testing includes Breakdown Voltage

• Insulation Resistance
• Impulse withstands Voltage.
• Comparative Tracking Index

CTI Tester

Impulse Tester

3. Flammability Testing Includes

• Glow Wire Flammability Index
• Glow Wire Ignition Test
• Flammability Test as per UL 94
• Heat Deflection Temperature Test

GWIT Test

Heat Deflection Tester

Applications

In view of their excellent features and benefits, these materials will continue to be used for many demanding applications. Electrical & Electronics (mechanical integrity and electrical insulation) Low voltage and medium voltage energy systems Mass Transportation (light weight and fire resistance) Train, tram interior and body parts Electrical components Track switch components Under the hood components for trucks. Automotive & Truck (low fuel emissions through weight reduction) Light weight body panels for vehicles Lighting systems, headlamp reflectors and LED lighting Structural parts, front ends, etc. Domestic Appliances (manufacturing in large volumes) Iron heat shields Coffee machine components Microwave ware White goods components, grips, and handles Pump housings as metal substitution Motor housings as metal substitution.

Engineering (strength and durability) Functional parts in mechanical engineering as metal substitution Pump components for various media Sport equipment, golf caddy Safety products for leisure and public application

Summery and conclusion

Powercam electricals Pvt. Ltd. is a global producer and supplier of SMC and DMC, and their products, particularly in the fields of electrical insulations under the brand name POWERMAT. To ensure provide the highest quality of insulator to their customers, company continuously involve in the research and development of the products. Multi-level quality check has carried out from raw material to finish product.