The history of blow molding (first part)
May. 13, 2024
The history of blow molding (first part)
The blowing of plastics
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has its roots in
glass blowing
.
The invention of blown glass
was born in the same period of
the birth of the Roman Empire in the 1st century BC
, which promoted the spread of this new technology. Glass blowing was supported by the Roman government, and glass artifacts were produced in many areas of their empire, on the eastern borders for instance, where now there are the countries of Lebanon, Israel and Cyprus, the Phoenician people created the first large blowing factories.
1935: The blow molding industry born in Italy
Actually, the process for obtaining packaging by "blowing" a thermoelastic material, was known since 1920, but had just a little use and only to produce cellulose objects.
From the 1930 there is a report of the first patents in this field, but we must wait the 40s to see the first successes of this technology, mainly due to the introduction of polyethylene and PVC which allowed the large-scale production of blown bottles.
The first EBM (Extrusion Blow Moulding) technology for hollow bodies was initially applied only for small bottles, later also for large containers up to 5 liters.
Afterwards, the IBM (Injection Blow Molding) technology was developed and used above all to produce flacons and bottles for pharmaceutical or cosmetic markets.
1940s and 1950s: The first manufacturer
The history of blowing hollow bodies began in Italy with Giuseppe Moi, originally from Sardinia, who created an empire between 1937 and 1987. Moi, in fifty years had managed to allow thirty companies start the blow moulding business in Italy and abroad. In 1951 the first half-liter Italian blow molding machine was manufactured, equipped with double screw extruders for the production of bottles for detergents. The first blow molder was followed, in 1962, by machines of different sizes, from 2 to 10 Lt. with either heads in continuous extrusion and with an accumulation head.
1960s: The first large Italian blow molding industries
Just after the second word war, two other companies started the development of these technologies: F.lli Moretti and Co-Mec.
The Moretti was founded in 1957 by the brothers Domenico and Giorgio Moretti as: "Mechanical workshop for the construction of machines and moulds for plastic hollow bodies". F.lli Moretti beyond the machines built also extruders, extrusion heads, dies and small towings. One of the first blowing machine, built in 1959, was continuous extrusion type with pneumatic movements to blow 2 Lt. containers for detergents.
The Co-Mec was founded in 1960 by Herberto Hauda, and until 1965 it built blowers with pneumatic movements with a maximum capacity of 5 Lt., while, in 1966, the first hydraulic type machine see the light, it could be equipped either with single head for 5 Lt container or a double head for up to 1 Lt. bottle.
Towards the end of the 1960s, the first special heads were manufactured (for PVC and PE), with the possibility, in some case, to color the bottles in stripes.
We must also remember Piero Giacobbe founding in 1960 the ASCO - Association of plastics machinery manufacturers. The first blowing machine was called Mini Magic, and equipped with a 38mm / 22D extruder driven by an hydraulic motor and an accumulation head with a control unit panel and 3 thermoregulated heating zones. (The complete line cost at the time 3,558 liras, approximately 1,700 euros today).
The ASCO, in 1965, was changed in MagicMP and quickly became a leader among the Italian blow moulding manufacturers for containers up to 200 liters, thanks to the Miniblow and Maxiblow models – the first for processing rigid PVC for food markets with automatic deflashing and neck calibration and the second for the production of larger containers up to 50 liters, with accumulation head and adjustment of parison weight and thickness.
...But the story continues.
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Blow Moulding: History, Process, and Types
The idea of creating diverse useful shapes by using air to blow a heated material was first employed by the Syrian glass workers about 3,000 years ago. The process used by Syrians consisted of placing a long tube into a receptacle, located in a blast furnace with liquid gas, removing the blob of white-hot liquid glass, spinning it, and finally blowing into a mouthpiece on the other end of the tube. This process later was refined in Europe during the Middle Ages due to the demand for bottles to contain and ship products such as wine. Egyptians also have records of blow moulding in the royal tombs and further developments between 1700-1600 BC.
The process of blow moulding is widely used to produce hollow containers that range from commodity products, such as soda or water bottles, to highly engineered products such as gas tanks or electrical enclosures.
The global market for blow moulding products has an important size, particularly for the blow moulded plastics, for which about USD 75 billion were estimated in 2018 with a projection of 4.5% between 2019 and 2025. The growing demands include the construction, automotive, and packaging industries with lead markets in Brazil, Russia, India, China, and South Africa and growth additions in the recent years in the Middle East and the Asia Pacific.
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In this article you will learn about:
- The history of blow moulding
- The blow moulding process
- Types of blow moulding
- Future trends of blow moulding
The history of blow moulding
The official application of blow moulding began with the use of celluloid and celluloid nitrate that were used to develop a limited number of products as the celluloid is highly flammable. The process was commercialised with the first automatic blow moulding machine by the Plax Corporation in the 1930s. By 1939, this corporation had a machine capable of producing 25,000 bottles per day, and in 1945, introduced the use of the recently developed low-density polyethylene (LDPE) to squeeze bottles.
In 1953, the market for blow moulding products exploded with the appearance of high-density polyethylene (HDPE). The introduction of polyethylene terephthalate (PET) in the 1970s also allowed the development of more efficient processes. The production of other diverse resins with time allowed a wide range of other material properties to become available, the appearance of larger and more robust equipment, that lead to the production of a large range of industrial and technical applications.
The blow moulding process
The process of blow moulding consists of forming a hollow object by literally blowing a thermoplastic hollow cylinder called parison or preform, in the shape of a mould cavity. The parison is dropped between two female open-mould halves, which are shaped to the desired product. Once the parison has enough length, it is heated and blown with pressurised gas, generally air, against the mould. The product is cooled and crystallised until it is removed from the blow mould to avoid deformation.
Typical materials used for processing by blow moulding are shown in the table below.
Table 1. Materials processed by blow moulding
Material
Acronym
Polyethylene (Low Density)
LDPE, LLDPE
Polypropylene
PP
Polyethylene - Terephthalate
PET
Polyvinyl chloride
PVC
Polyethylene (High Density)
HDPE
Types of blow moulding
The most common processes of blow moulding are extrusion blow moulding, injection blow moulding, and stretch moulding.
Figure 1. Breakdown of blow moulding methods
Extrusion blow moulding
Extrusion blow moulding is the process where:
- The thermoplastic material is melted and extruded (expelled) into the hollow tube (parison),
- The mould is closed,
- Compressed air is blown into the parison filling the mould,
- Finally, after cooling and crystallization, the product is removed.
The extrusion process is further divided into continuous and intermittent processes. In the continuous process, the parison is extruded continuously and the mould is opened and closed to complete the process. On the other hand, in the intermittent process, the material is collected by the extruder and then pushed to the die.
Extrusion is the most common method in blow moulding and is used in manufacturing products such as milk bottles, shampoo bottles, automotive ducting, watering cans, and other industrial parts. The main advantages of this method are the low cost and fast production rates, as well as the ability to produce complex geometries. Some of the limitations include the mere production of hollow parts and the material's low strength. When used for producing wide neck bottles, spin trimming is required.
Injection blow moulding
Injection blow moulding is the process where the material is melted and injected (forced) into a precisely dimensioned die until it cools and solidifies to the desired product shape. The process consists of three steps: injection, blowing, and ejection.
Injection blow moulding is mainly used to produce bottles, jars, and containers in large quantities. This method is less common due to the limitations on the production rate and is preferably used for small products such as those for medical applications. Its main advantage is the ability to produce accurately complex-moulded necks. However, it suffers from the restriction to small bottles production only and low strength in the barrier.
Stretch moulding
In stretch moulding, the parison is formed in a similar way as the injection blow moulding, but with the difference that once transferred to the blow mould, it is heated and stretched downward by the core before inflation. The stretching method allows for the use of increased strength in the material.
Stretch moulding is highly advantageous for low volumes and for allowing the mould wall to be shaped in rectangular and non-round shapes. Yet, the method has restrictions on bottle designs. It is used to produce parts subjected to internal pressures or with high durability demands, such as soda bottles.
Future trends
The future of blow moulding is the innovation of machinery. Diverse equipment that include energy-efficient features has been developed in the recent years (i.e., EBLOW 37 for manufacturing of canister for packing industry). The challenge of this technology is in offering a technological, economical and attractive solution for product manufacturing that also include considerations regarding environmental concerns on product disposal.
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