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Frapak has a wide range of standard PP jars available, such as the softline, the straight and the stackable versions. Neck size 89-400 jar and 70-400 jars are available in a range of different sizes: 5 ml, 15 ml, 30 ml, 50 ml, 100 ml, 200 ml up to 500 ml in standard PP. We also have many jars available in stock.
The most common plastic used in the construction of jars is polypropylene or PP. This abbreviation is the general name for a number of different varieties of PP like homopolymer, copolymer and random copolymer used in the injection moulding of PP jars. PP as a material is often used for making cream jars and containers as it has good product resistance to fats and almost all other organic solvents.
The injection moulding (IM) process is known for its flexibility in materials and the preciseness of the PP parts. Pellets of PP material are fed into the hopper of the machine and then heated up the thermoplastic PP material to the right temperature for processing. This heating process is created by a combination of the heat from a barrel and the shear created by the screw.. When enough material has been processed, the injection machine forces the heated material under pressure into the injection mould to form the components of the PP jar. The injection moulds for PP jars can be made with 2 cavities up to 12 depending on the size and the design of the jar. As the PP jar should be able to be released from the injection mould there is always a draft angle and the jar, therefore, is always slightly conical.
One of the main advantages of the injection moulding of jars is that the surfaces can frosted; an effect which is created by treating the outer plate of the injection mould. When the injection mould is filled during the moulding process, the surface of the mould creates the frosted or matt effect on the PP jars.
Basically there are two types of PP cream jars: the single walled and the double walled. The construction of the double walled PP jars consists of an inner jar which is fitted into an outer jar. The inner jar is injection moulded, completed with the neck finish and then mounted into the outer jar on an assembly line.
The inner jar is mainly produced in PP material as this plastic has very good product compatibility properties and when assembled gives the jars a more luxurious appearance. A single walled PP jar consists of one part and is, therefore, more cost effective.