This has two main different methods, namely Single-stage and two-stage process. In the single-stage process both preform manufacture and bottle blowing are performed in the same machine. The process explained: Imagine the molecules are small round balls, when together they have large air gaps and small surface contact, by first stretching the molecules vertically then blowing to stretch horizontally the biaxial stretching makes the molecules a cross shape. These "crosses" fit together leaving little space as more surface is contacted thus making the material less porous and increasing barrier strength against permeation. This process also increases the strength to be ideal for filling with carbonated drinks.
Advantages: Highly suitable for low volumes and short runs. As the preform is not released during the entire process the preform wall thickness can be shaped to allow even wall thickness when blowing rectangular and non-round shapes.
In extrusion blow moulding, plastic is melted and extruded into a hollow tube (a parison). This parison is then captured by closing it into a cooled metal mould. Air is then blown into the parison, inflating it into the shape of the hollow bottle, container, or part. After the plastic has cooled sufficiently, the mould is opened and the part is ejected.
Extrusion Blow moulding allows for a wide variety of container shapes, sizes and neck openings, as well as the production of handle-ware. Extrusion blown containers can also have their gram weights adjusted through an extremely wide range, Extrusion blow moulds are generally much less expensive than injection blow moulds and can be produced in a much shorter period of time.
Advantages: A high rate of production, low tooling cost, and a vast majority of machine manufactures. Some disadvantages usually include a high scrap rate, a limited control over wall thickness, and some difficulty of trimming away excess plastic. Also, extrusion blow moulding can be used to process many different plastics, including HDPE, PVC, PC, PP, and PETG.
Injection moulding utilizes a ram or screw-type plunger to force molten plastic material into a mould cavity; this solidifies into a shape that has conformed to the contour of the mould. Injection moulding consists of high pressure injection of the raw material into a mould which shapes the polymer into the desired shape. Moulds can be of a single cavity or multiple cavities. In multiple cavity moulds, each cavity can be identical and form the same parts or can be unique and form multiple different geometries during a single cycle.
Advantages: High rate of production, flexibility in design, repeatability within tolerances, can process a wide range of material, relatively low labour cost and better finishing of parts and minimum scrap losses.
The most commonly used material is PET - Polyethylene Terephthalate. PET in its natural state is a colorless, semi-crystalline resin. Based on how it is processed, PET can be semi-rigid to rigid, and it is very lightweight. It makes a good gas and fair moisture barrier, as well as a good barrier to alcohol (requires additional "barrier" treatment) and solvents. It is strong and impact-resistant. PET becomes white when exposed to chloroform and also certain other chemicals such as toluene.
Advantages: Excellent clarity, nearing that of glass, lighter weight products, high breakage resistance to avoid risk and injury, dimensionally accurate bottles, thermally stable, suitable for hot filling, suitable for recycling.
Polypropylene (PP), also known as polypropene, is a thermoplastic polymer used in a wide variety of applications including packaging and labeling, textiles, stationery, plastic parts and reusable containers of various types and more. An addition polymer made from the monomer propylene, it is rugged and unusually resistant to many chemical solvents, bases and acids.
Melt processing of polypropylene can be achieved via extrusion and molding. Common extrusion methods include production of melt-blown and spun-bond fibers to form long rolls for future conversion into a wide range of useful products, such as face masks, filters, diapers and wipes.
The most common shaping technique is injection molding, which is used for parts such as cups, cutlery, vials, caps, containers, housewares, and automotive parts such as batteries. The related techniques of blow molding and injection-stretch blow molding are also used, which involve both extrusion and molding. The large number of end-use applications for polypropylene are often possible because of the ability to tailor grades with specific molecular properties and additives during its manufacture.
Advantages: Offers a larger colour pallet, excellent chemical resistance and UV resistance, results in energy savings, lowest carbon footprint, greater durability, flexibility in design.
PCTA stands for Poly cyclo-hexane-dimethanol-terephthalate acid which is a copolyster.
Copolyester forms when modifications are made to polyesters, which are combinations of diacids and diols. For example, by introducing other diacids, such as isophthalic acid(IPA), or other diols, such as cyclohexane dimethanol (CHDM) to the polyester polyethylene terephthalate (PET), the material becomes a copolyester due to its comonomer content.
Copolyesters retain their strength, clarity, and other mechanical properties even when exposed to a variety of chemicals that typically affect other materials, such as polycarbonates. This, plus their versatility and flexibility, allows manufacturers to use them effectively in the design of both high-volume, low-cost parts as well as critical, more expensive component parts.
High-density polyethylene (HDPE) or polyethylene high-density (PEHD) is a polyethylene thermoplastic made from petroleum. Known for its large strength to density ratio, HDPE is commonly used in the production of plastic bottles, corrosion-resistant piping, geomembranes, and plastic lumber. HDPE is commonly recycled.
Advantages: Impact, stress and crack resistant, tough yet flexible, good chemical resistance, food contact acceptable, processability.
Three types of advanced machines are used within this process. These are imported, Japanese machines from Nissei – 70DPW for very high repetitive production, 70DPH for big Jars and 50 MB for small bottles.
With the cutting-edge machine from Ferromatik Milacron India, we have ventured into EBM recently. The machine is capable of producing various possible sizes and shapes of HDPE/PP containers, equipped with a 300 point comparison control for producing well-distributed, high-quality containers. We have two other machines within functioning within this process as well.
Three powerful, Ferromatic machines of Italian make offer different capacities to produce PP caps for jars and bottles.