MATERIALS USED IN INJECTION MOLDING - THERMOPLASTIC

THERMOPLASTIC

THE THERMOPLASTIC ARE HEATED AND BROUGHT TO MOLTEN STATE IN AN INJECTION MOLDING MACHINE . THE MACHINE INJECT THE PLASTIC INTO THE METAL MOLD WHERE IT COOLED. AFTER SOLIDIFICATION OF THE PLASTIC THE MOLD IS OPEN AND THE THE COMPONENT IS EJECTED THIS PROCESS IS CALLED INJECTION MOLDING.

THE OTHER PROCESS ALSO CAN TAKE PLACE IN THERMOPLASTIC MATERIAL I.E. BLOW MOLDING, ROTATIONAL MOLDING AND EXTRACTION MOLDING PROCESS(HOLLOW ARTICLES)

Polystyrene (PS)

Learn More About High-Quality Polystyrene Plastic Used in Injection Molding

One of the most common plastics used in THERMOPLASTIC MATERIAL is polystyrene, a synthetic polymer often used when molding packaging and industrial components. Usually in the form of foam or plastic, polystyrene is a non-toxic and odorless material, and is one of the predominant plastics used in the food packaging industry as well as the automation industry. Its solidity and clarity make it useful for everything from automobile parts and electronics to toys and plastic utensils.

Polystyrene is often used in cost-effective packaging products since it has many benefits, including:

• Resistance to bacterial growth
• Resistance to moisture
• Lightweight
• Provides insulation
• Durable
• Recyclable                                                                                                       

Specifications of Polystyrene (At Room Temperature)

Chemical Formula	(C8H8)n
Melting Point (°C)	~215°C
Tensile Strength	~7700 psi
Impact Strength	~0.8 ft-lb/in notched Izod
Hardness Level (Rockwell)	R75
Flexural Modulus	~12000 psi

Advantages of Polystyrene Used in Injection Molding

Polystyrene plastic products offer many advantages as an injection molded plastic solution. It's an affordable and versatile material, and it allows businesses throughout the United States to use it for a wide variety of applications.  

APPLICATIONS

POLYSTYRENE IS DONE IN MANUFACTURING OF PARTS WHICH REQUIRE A COMBINATION OF COLOUR CLARITY STIFFNESS ,LOW COST,AND GOOD APPEARANCE
THIN WALL AND RIGID CONTAINER FOR PACKING, TOYS, TRUMBLERS , SOAP, DISHES, FITTING FOR CLAMPS , DESK CALENDERS ETC.


TYPES

1.  GPS : GENERAL PURPOSE POLYSTYRENE 
2. HIPS : HIGH IMPACT POLYSTYRENE 
3. ABS : ACRYLO NITRILE BUTADINE STYRENE

LDPE (Low Density Polyethylene)

After its experimental preparation in the 1930s, the application in high frequency radar cables during World War II, gave impetus to its commercial production. This thermoplastic is available in a range of flexibilities depending on the production process. High density materials are the most rigid. The polymer can be formed by a wide variety of thermoplastic processing methods and is particularly useful where moisture resistance and low cost are required. Polyethylene is limited by a rather low temperature capability (200-250 F) but is manufactured in billions of pounds per year.

Vinyl acetate can be copolymerized with ethylene. The resulting product has improved transparency over homopolymerized polyethylene because of a reduction of crystallinity in the copolymer.

ADVANTAGES:

• Low cost
• Impact resistant from -40 C to 90 C
• Moisture resistance
• Good chemical resistance
• Food grades available
• Readily processed by all thermoplastic methods

DISADVANTAGES AND LIMITATIONS:

• High thermal expansion
• Poor weathering resistance
• Subject to stress cracking
• Difficult to bond
• Flammable
• Poor temperature capability

Note:

In general, high density grades of polyethylene have densities up to 0.97 g/cm^. Low density grades are as low as 0.91 g/cm^. Typically, the high-density material is more linear and consequently more crystalline. As might be expected, this higher crystallinity permits use at temperatures up to 130 C degrees with somewhat better creep resistance below that temperature. Low density polyethylene has less stiffness than the high density type. Blends of the two types are common.

TYPICAL APPLICATIONS:

Toys, utensils, films, bottles, pipe and processing equipment. Wire and cable insulations.

HIGH DENSITY POLY ETHYLENE(HDPE)

                                                     

                                      HDPE is a commonly used petroleum thermoplastic and the most used of the three polyethylenes for a wide range of applications. If you look at this plastic under a microscope, you would see that it has a linear structure with few branches lending to its optimal strength/density ratio. As a result of its molecular makeup, this polymer shines brightest in applications where moisture resistance and cost-effectiveness are needed.

 its higher density versions yield a more rigid result, HDPE can vary in flexibility. Low-density grades of the thermoplastic are less stiff and the high-density grades have equally high crystallinity.

The Advantages and Disadvantages of HDPE

Even with its popularity, there are some advantages and disadvantages you should consider before using HDPE for your application:

Advantages

• Cost-effective
• Can withstand temperatures from -148 to 176 degrees Fahrenheit
• Non-leaching
• UV-resistant
• Dishwasher safe
• Resistant to most chemical solvents
• Stiff material

Disadvantages

• Poor weathering resistance
• Flammable
• Sensitive to stress cracking
• Difficult to bond

4 Common Uses for HDPE

1. Plastic bottles: Most people are informally introduced to the durable plastic through water bottles. HDPE is great for blow-molding applications, particularly food and beverage containers because it won’t leach into the bottles’ contents. In addition, HDPE is recyclable which makes it a great choice for these highly disposable products.

1. Toys: HDPE is UV resistant which helps keep the toys resistant to the ray’s damaging and discoloring effects.

1. Chemical containers: With its chemical resistant properties, HDPE is great for laundry, shampoo, conditioner, household cleaning products, motor oil, antifreeze and recycling bins. The strength of these bottles is increased when they’ve been colored or pigmented.

1. Pipe systems: HDPE pipe grade sheet has a higher molecular weight compared to the standard HDPE used in the above examples. This strengthening with its UV-resistance makes it ideal for piping and outdoor applications. Pipe grade sheet has the ability to withstand -220 to 180 degrees Fahrenheit. It’s durable in most chemical interactions which make it useful in a lot of industrial applications.

POLYPROPYLENE :

Polypropylene (PP) is one of the most commonly used thermoplastics in the world. Polypropylene uses range from plastic packaging, plastic parts for machinery and equipment and even fibres and textiles. It is a rigid, semi-crystalline thermoplastic that was first polymerised in 1951 and is used widely today in a range of domestic and industrial applications. Today, global demand for polypropylene is estimated at around 45 metric tons and this figure continues to rise exponentially.

Uses for polypropylene

Polypropylene has a slippery, tactile surface, making it ideal for

• plastic furniture
• low friction applications, such as gears in machinery and vehicles.

It is highly resistant to chemical corrosion, making it an excellent choice for packaging for

• cleaning products
• bleaches and
• first-aid products

It offers excellent fatigue resistance and elasticity, securing it a well-deserved reputation for toughness and durability.

Polypropylene has high insulation properties too, making it safe to use for plastic casing in electrical goods and cables. In its fibre form, polypropylene uses are not limited to not only useful for tote bags but also encompass a much wider range of other products, including ropes, twine, tape, carpets, upholstery, clothing and camping equipment. Its waterproof properties make it especially effective for the marine sector. In the automotive industry, polypropylene is also used widely, for example in for battery casings, trays and drink holders, bumpers, interior details, instrumental panels and door trims.

Finally, the medical world appreciates the waterproof properties of polypropylene too, as well as its flexible strength, resistance to mould, bacteria and chemical corrosion. It cleans well a sit can stand up to steam sterilisation methods. Some medical applications include,

1. syringes
2. medical vials
3. Petri dishes
4. pill containers
5. specimen bottles