Posted tagged ‘Chloride’


August 23, 2011

Today, when walking in your supermarket, it is increasingly difficult to find items packed in glass and jars.  Packaging for soft drinks, healthcare and beauty products, household chemicals and medicines, among other products, have switched from glass or metal to plastics.  Today the Blow Molding industry has expanded from simple plastic containers to plastic drums, gas tanks, automobile parts and toys in all shapes and sizes.

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Blow Molding (BM) process makes it possible to manufacture molded products economically, in unlimited quantities, with virtually no finishing required.  The basic process of blow molding involves a softened thermoplastic hollow form which is inflated against the cooled surface of a closed mold.  The expanded plastic form solidifies  into a hollow product.

Blow molded components are now seen all over the markets and industries for traditional materials, particularly in liquid packaging applications.  The last few decades saw the introduction of  Poly Ethylene (PE) squeeze bottles for washing liquids, Poly Vinyl Chloride (PVC) for cooking oil and fruits squash bottles, and Poly Ethylene Terephthalate (PET) for carbonated beverage bottles.  Nowadays, it is also used for the production of toys, automobile parts, accessories and many engineering components.

There are basically four types of blow moulding used in the production of plastic bottles, jugs and jars. These four types are:

  1. Extrusion blow molding,
  2. Injection blow molding,
  3. Stretch blow molding and
  4. Reheat and blow molding.

Extrusion blow molding is perhaps the simplest type of blow molding, whereby a hot tube of plastic material is dropped from an extruder and captured in a water cooled mold. Once the molds are closed, air is injected through the top or the neck of the container; just as if one were blowing up a balloon. When the hot plastic material is blown up and touches the walls of the mold the material “freezes” and the container now maintains its rigid shape. There are various types of shuttle, reciprocating and wheel style machines for the production of extrusion blown bottles. Shuttle or reciprocating type machines can be used for small, medium and high volume production with wheel machines being the most efficient for huge volume production of certain resins.

01-petblow-plastic products manufacturing-PET Preform-PET bottles-stretch blow molding

A typical apparatus consists of following major components i.e. blow pin, plunger, accumulator and lastly a mold.

Actually the process utilizes air pressure to inflate softened thermoplastic tube which is sealed at one end (also called as parision). This parision is constantly inflated and extruded. Then later on it is cut according to required dimensions. The temperature in Accumulator is maintained around 400 degree Celsius or so.

Stretch_blow_mold-dies-PET Pre form mold-household appliance mold

The mold consists of two split parts which have a semi-circular cross-section. Usually the air pressure which is applied in low pressure molding is about 50 to 250 psi. Various forms of blow molding used in industry today on a wide scale are Injection Blow Molding.

Injection Blow Molding though not used in industry, has very limited and specific applications like making small medicine plastic bottles etc. Extrusion blow molding is the simplest form of blow molding. A tube of plastic material which is generally maintained hot, is dropped from an extruder only to be captured in a water cooled mold. Once the molds are closed, air is injected through the top or the neck of the container and the tube is inflated just like a balloon. When the hot plastic material is blown up and touches the walls of the mold the material is cooled and the container now maintains a solid, rigid shape.

Now Stretch blow molding, this process requires the raw material to be formed in a pre-form using injection molding and later on stretch blow molding process can be applied.

The product range varies from various cylindrical components like bottles, cans, floats heater ducts in automobile parts and various small pipe fittings and hollow cylindrical parts can be produced in mass production.

The advantages are many like the tooling costs are very less as compared to injection molding, the part performance is excellent under pressure. Then the products have excellent environmental stress crack resistance. The products also perform excellently in high speed impact strength than even the metal components the process can be automated and used in mass production.

The disadvantages mainly raise environmental concerns. It depends on petroleum industry as any plastic industry depends. Also the cylindrical shapes are delicate so if the dimensions are not accurate then they result in scrap.


August 23, 2011

Plastics are excellent materials with unique and very useful properties. You can produce just about anything you can imagine using plastics.

01-Plastics-food-containers-durable plastic products-plastic boxes

Characteristics of Plastics

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History Of Plastics:

1. Before Plastics—Age of the Natural Resins

  • Rubber—Tough elastic substance (light cream or dark amber
    colored) from the milky juice (sap) of rubber tree
  • Ebonite—Hard black rubber; natural rubber + sulfur
  • Gutta-Percha—Dark brown substance like natural rubber
  • Shellac—dark-brown material from lac insects

2. Bakelite—The First True Synthetic Plastics

  • Leo Hendrik Baekeland invented Bakelite from coal
  • Bakelite helped make 20th century “The Age of Electricity”

01-Reaction to produce plastics-plastic formation-industrial plastic manufacturing-plastic production methods3. Industrialization of Major Plastics

Year Type of plastics Note
1872 Celluloid (Hyatt, USA) Semi-synthetic
1910 Phenolic resin, “Bakelite” (Baekeland, USA) From coal
1931 Polymethyl methacrylate (PMMA) (Rohm and Haas, Ger-many) From coal
1935 Polyvinyl chloride (PVC) (IG Farben, Germany) From coal
1935 Polystyrene (IG Farben, Germany)

From oil

1938 Nylon 6 (IG Farben, Germany)
1939 Nylon 66 (DuPont, USA) From coal
1939 High-pressure low-density polyethylene (LDPE) (ICI, Eng-land)
1953 Polyethylene terephthalate (PET) (DuPont, USA)
1953 Low-pressure high-density polyethylene (HDPE) (Montecatini, Italy) Ziegler catalyst
1955 Medium-pressure high-density polyethylene (HDPE) (Phillips, USA) Phillips catalyst
1957 Low-pressure high-density polyethylene (HDPE) (Hoechst, Germany) Ziegler catalyst
1959 Polypropylene (Montecatini, Italy)
1977 Linear low-density polyethylene (LLDPE) (UCC, USA)
1991 Metallocene very-low-density polyethylene (VLDPE) (Exxon, USA) Metallocene cata-lyst

4. Concept of High Molecular Weight Compounds & Polymers

  • Herman Staudinger, German chemist, proposed a new theory that several thousands of reactive units bonded together in chains and form giant molecules to make up cellulose and rubber
  • In 1920, Staudinger proposed calling such materials: high molecular weight compounds, macromolecules, or polymers.

5. Nylon—The First Tailor-Made Plastics

  • 1931 – Fiber 66 was produced, later called Nylon 66 in 1938