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First, we have to understand that what is Polymer. It is a class of molecules with large numbers of repeating structural units connected through covalent bonds. So how we know about different polymers? It is differed by repetition of many similar, identical or complementary subunits.

Polyethylene is the first choice for plastic moulding process and the reason is its availability, ease of use and also it has many suitable properties. There is 80-90 percent of polymers used in plastic moulding industry are polyethylene compounds (HDPE, LDPE and LLDPE). And also, PVC, nylons and polypropylene compounds are used.

Polyethene is widely used thermoplastic created through polymerization of ethylene.

It is also known as Polyethene, Polythene, PE, LDPE, HDPE, MDPE, LLDPE.

• LDPE (Low-Density Polyethylene)

LDPE has a density range of 0.910 – 0.940 g/cm³. LDPE has a high degree of short and long chain branching means the chains do not pack into crystal structures. Due to this, it has less intermolecular forces and the instantaneous-dipole induced-dipole attraction is less. Which means it has lower tensile strength and increased ductility. The LDPE is created by free radical polymerization. LDPE gets its to flow properties from the high degree of branches with long chains.

• HDPE (High-Density Polyethylene)

HDPE has a density of equal or greater than 0.941 g/cm³. It has a low degree of branching gives stronger intermolecular forces and tensile strength. It can be made with chromium/silica catalyst, Ziegler-Natta catalyst or metallocene catalysts.

• MDPE (Medium Density Polyethylene)

MDPE has a density range of 0.926 – 0.940 g/cm³. The MDPE can be produced by chromium/silica catalysts, Ziegler-Natta catalysts or metallocene catalysts.

• LLDPE (Linear-Low Density Polyethylene)

LLDPE has a density range of 0.915 – 0.925 g/cm³. It is a substantially linear polymer and has significant numbers of short branches made by copolymerization of ethylene with a short chain of alpha-olefins like 1-butane, 1-hexene and 1-octene.

Polyvinyl Chloride (PVC)

Polyvinyl Chloride Polymer

Vinyl Chloride Monomer (VCM) 

Polyvinyl Chloride (PVC) is widely used thermoplastic material for various application. To produced it, the required material is derived from Oil and Salt. The vinyl chloride monomer (VCM) is formed by mixing ethylene which is obtained from oil and Chlorine produced by electrolysis of salt water. The VCM molecules are polymerized to form PVC resin and along with different additives made customized PVC compound.

Nylons

Nylon is a group of plastics known as polyamides. It is used in the manufacturing of fiber and film and it is also used as a moulding compound.

There are many types of Nylon available like nylon 6, nylon 66, nylon 6/6-6, nylon 6/9, nylon 6/10, nylon 6/10, nylon 6/12, nylon 11, nylon 12. Nylon is used as homopolymer, copolymer or reinforced. Nylon mixes with other engineering plastics to create required material. It is suitable for injection molding, rotational moulding, casting or extrusion into film or fiber.

Chemical Composition

Polypropylene

The thermoplastic polymer, polypropylene also known as polypropene has properties between LDPE and HDPE and it is more versatile material available.

Chemical Composition

Acrylonitrile Butadiene Styrene

Acrylonitrile Butadiene Styrene (ABS) is an opaque thermoplastic and amorphous polymer. It is a terpolymer consist of Acrylonitrile, Butadiene and Styrene. All these material mixes and creates a product which is flexible and light in weight and it is used in our many daily routine items.

The main benefit of using ABS that it improves impact resistance, toughness and heat resistance. If it is moulded on the high temperature it gives gloss and heat resistance to the product and if it is moulded on the low temperature it gives the highest impact resistance and strength to the product.

ABS is used in drain pipe systems, plastic clarinets, golf clubs heads, automotive parts, kitchen appliances and many more.

Polycarbonate

Polycarbonate plastics are naturally transparent amorphous thermoplastics. It is used in various products but most in where impact resistance and transparency are required like Bullet-Proof Glass. Opposite of different plastics Polycarbonate can goes to large plastic deformation without any crack or breaks.

It is widely used for greenhouses, DVDs, eyewear lenses, medical devices, automotive components and cellular phones.

High Impact Polystyrene

The high impact polystyrene (HIPS) is very popular and tough plastic in polystyrene family. Polystyrene itself is brittle but can be made more impact resistant if mix with other materials. It is made with modifying crystal styrene with rubber which gives it more impact resistance. HIPS is low cost, good dimensional stability and rigidity.

It is highly flammable but there are also flame retardant and high gloss grades are used for injection moulding.

The plastic is synthetically produced non-metallic compounds. Plastic can mould into various forms and hardened for commercial use. The plastic products are easily seen. The plastic products we use like jars, protective caps, bottles, toys, kitchen utensils, accessories and many more.

We cannot imagine the world without plastic products. The keyboard and mouse we use is also made with plastic moulding. The plastic part of chairs which you sit is also made with the same process.

The process is just simple. The molten liquid plastic is inserted into a mould like the plastic bottle. After that, it is left for cooling and after that the final product is ready.

The moulds are used to form various plastic products like cabinets, barriers, barricades, traffic signage, garden pots and many more.

If you want to start a plastic moulding process, you should have to understand the different processes first. Choose one of the plastic moulding processes according to your budget, resources and expertise. Below there are various processes for plastic moulding.

Blow Moulding

In the blow moulding process, the air pressure is used to inflate the molten plastic into the mould cavity. This process is used to make one-piece hollow plastic products like bottles and containers. The blow moulded items are widely used in consumer beverages and manufacturers arrange the production for maximum numbers.

The blow molding process has two steps:

 – Starting the process with making the tube of molten plastic called parison.

– Inflate the parison into the final shape.

The Parison is formed from extrusion or injection moulding techniques.

Extrusion Blow Moulding

Manufacturers used extrusion blow moulding for high-production operations for making plastics bottles. The process is automatic and combines with operations like bottle filling and labeling. The blown containers must be rigid. The rigidity depends on various factors like wall thickness.

The extrusion blow moulding process contains below steps.

– Extrude the Parison.

– Cut the Parison from the top and seal at the bottom and the two halves of mould come together.

– After inflating the plastic tube took the mold cavity’s shape.

– Open the mold and remove the final product.

Injection Moulding

The injection blow molding process contains the injection of mold the prison instead of extrusion. It has low production rate than the extrusion process.

The process has below steps.

– Injection-mould the parison around a blowing rod.

– The parison is transferred to a blow mold.

– Inflate the soft polymer to the mold.

– Open the mould and remove the product.

Stretch Blow Moulding

The manufacturers use the variations of injection blow moulding known as stretch blow moulding. In this technique, the blowing rod is extending downward into the injection moulded parison and this stretch the plastic and create a more stressing of polymer than conventional injection blow moulding. The final product is more rigid, higher transparency and it is more impact-resistant.

The Polyethylene terephthalate (PET) is the most widely used material for plastic injection moulding. The PET is polyester with low permeability and the stretch-blow-molding process gives strength and it is ideal for making containers for carbonated beverages.

The Stretch blow moulding steps:

– Injection moulding

– Stretching

– Blowing

Blow Moulding Materials and Products

The polyethylene (PE) is an ideal for blow moulding process as it has high density and high molecular weight polyethylene.

Materials used for blow moulding:

– Polypropylene

– Polyvinylchloride (PVC)

– Polyethylene terephthalate

Rotational Moulding

Rotational moulding or roto moulding use gravity inside a rotation mold to create a hollow form. This technique is used also as an alternative to blow moulding to make the large, hollow shape. This is used for thermoplastic polymers but now thermoset and elastomer are more common. The roto moulding is better than blow moulding for more complex external geometries, large parts and for lower production quantities.

The roto moulding process has below steps.

– First, load a predetermined amount of polymer powder into a split mould cavity.

– Heating and rotating the mould on two perpendicular axes so the powder can coat the mould’s internal surfaces equally and make sure to make uniform thickness layer.

– Open the mould and unload the ready product.

The speed during the process is slow. The process is done with gravity not with centrifugal force and this coat the mould surfaces.

The Rotomolding Moulds

The rotomoulding process is simple and less expensive than injection moulding and blow moulding. But the production cycle took more time around 10 minutes. To minimize time there is three station moulding machine.

First Station – In this station, unloading of final product and load the powder for the next step in the cavity.

Second Station – the Heating station where hot-air convection heats the mould as rotate and the temperature inside reaches up to 375^o C depends on polymer and item molded.

Third Station – The third station is a cooling station that cools the mould with cold air or spray of water to solidify the plastic moulding inside.

The products are made with rotational moulding.

Toys, Boat and canoe hulls, Sandboxes, small swimming pools, Buoys and other floatation items, truck body parts, automotive dashboard, fuel tanks. Furniture, garbage cans, fashion mannequins, containers, storage tanks and many more.

The material used for roto moulding

– Polyethylene, mainly HDPE

– Polypropylene

– Acrylonitrile butadiene styrene (ABS)

– High-impact polystyrene

The plastic moulding process is a technical process which cannot be done by everyone. It requires knowledge about various materials and knows the process in every stage.

So it is advisable to study the business and market of your final product.

The choosing of proper Screw and Barrel combination is a very essential part for the plastic product manufacturing process. However, most people make mistake while choosing a proper screw and barrel. The companies are not serious about choosing screw and barrel. But now the situation is better companies started think about that still the screw and barrel are secondary when purchasing the machine.

The manufacturers are always considering the performance, controls, clamp speed, dry cycle speed and other important features while purchasing the new machine. There is the reason why they focusing on this feature because these features are important for maximum production and performance. The screw and barrel selection comes after these, since a very long time before.

Now companies use more engineered resin and they want more production and minimize the scrap, are the main features that have to be considered before choosing proper screw and barrel. The production growth is increased in the last 10 years as the industry is developed plastic/resin used in products. As the continuous research and development made in plastic and resin, it draws the attention of manufacturers to choose appropriate parts for screw and barrel set up to get maximum production from it.

So how to choose proper screw and barrel?

There are various factors that affect a selection of right screw and barrel. The industrial standards, material use is directly affected. Factors like the size of the machine, heat, cycle time, recovery time, melting temperature and so many other factors direct or indirect effect it.

There is a factor to be considering the ratio of screw and barrel and also metallurgy. The choosing the proper screw and barrel is essential for any machine. The manufacturers forget to upgrade the existing screw and barrel with improved and latest technology. They have to care about the sizing of screw and barrel, coating and metallurgy with material handling against cost and changes of clamp end to improve overall performance. When any plastic manufacturer wants to upgrade existing machinery with the latest or just to improve existing machinery, they have to take care of the screw and barrel for maximum productivity and performance.

For Buying Any Type of Blow Molding Machine: plastic product making machine

There are different types of the moulding processes is used for forming a plastic to make various products of different size and shapes. The plastic turns liquid and becomes soft when heated. It can be easily formed for various products. The melted plastic is inserted into a mold and after it is cooled the mold is removed and the product is ready. The plastic products are made with different processes like casting, injection molding, blow moulding, compression molding and rotational molding.

Let’s start with the casting process. In this process, the plastic molding is completed with casting. The plastic is heated till it turns liquid and then inserted into a mold. There is no additional pressure is applied to this process. In the casting process the liquid turns into solid by various methods like evaporation, cooling, use chemical or applied external heat. The casting process is completed with less equipment and it is not costly. The products have little to no internal stress. The Nylon type 6 and Polyurethanes have widely used a material for casting. It is mainly used for complex designs.

The next is the Injection Molding. The process contains three steps. First is design the product. After designing and testing the second step is mold design. There are various metals used for mold to give strength and durability. In the third step, the thermoplastic material is fed from a hopper to a heating barrel. The plastic is heated and took to the mold by a large screw. After filling the mold the screw applies pressure for cooling. After cooled, the product is removed from a mold and this cycle is repeating more and more time to make lots of products. The dashboard of a car, bottle caps, plastic cup lids etc is made with injection molding process.

Ahead in the list is Blow Molding Process. As the name stated blow molding, in this process, the plastic is melted and made a hollow tube. This tube is inserted into a mold and blows the air and the tube is inflated to mold size and shape. The cold air is blown to cool down and it is ejected automatically. The blow molding process is mainly used for making hollow products like milk containers, water bottles etc.

The Compression molding is more complicated and required more labors. The compression molding is more complicated, it is used for large-scale production not for mass production. In the process, the molten plastic is poured into the mold and the second mold pressed it with high pressure. These molds compress the molten plastic before cooled. After removing the mold we get a product with maximum strength with desired size and shape. The compression molding is used for making car tires.

The rotational molding process the plastic in powder form is added to a mold. After it, the mold is closed and heated while rotating. When the plastic is melted it coated the wall of the mold. Then it took to the cooling area and cooled with air. After the product turns to solid the mold is opened and ejects the product. Products like water storage tank, containers, crates, traffic dividers, furniture and toys are made with the rotational molding process.

For Buying Any Type of Blow Molding Machine: Automatic Blow Moulding Machine Manufacturer