Please note that we only supply polymer in granular form for Injection Moulding or Extrusion applications. We do not supply polymer in rod, sheet or block form.

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    Is Thermoplastic Polyester your PET Subject?

    The most important member of the Thermoplastic Polyester family is polyethylene terephthalate (PET). It was invented in the early 1940s in Manchester by Whitfield and Dickson.  This is a good example of how inventions tend to emanate from smaller organisations, in this case Calico Printers Association.  It was left to big organisations, ICI and DuPont, to develop the material commercially.  (My closest brush with fame was back in the 1960s when I inherited Jim Dickson’s desk when I changed companies.)

    Thermoplastic Polyester Image

    The initial attraction of PET was as a fibre (‘Terylene’, ‘Dacron’). However. it quickly became popular as a transparent packaging film (‘Melinex’, ‘Mylar’). Eventually it has become the material of choice for bottles.

    Early on, injection moulding machines could not cope very well with PET’s high melt transition temperature (265oC). Today that is less of a problem.  To fill the gap, polybutylene terephthalate (PBT) was introduced as a moulding material, with a slightly lower Tm (230oC) and a lower melt viscosity, while still retaining much of the good mechanical, chemical, electrical and thermal properties of PET.  Today PBT, particularly its glass filled grades, finds many applications in electrical equipment. These applications include connectors, sockets, bobbins, motor housings and insulation.

    PET Trade names: Arnite, Impet, Ramapet, Rynite, Valox, Skygreen, Tripet

    PBT Trade names: Arnite, Celanex, Crastin, Lupox, Luranyl, Pocan, Ultradur, Valox

    In terms of properties, PBT is now featuring in blends with PET and also with polycarbonate, ABS and ASA.

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    Coping with weld lines

    In injection moulding, weld lines (knit lines) form when two melt fronts meet. If the melt fronts do not coalesce completely, at best there will be a cosmetic flaw. At worst there will be a mechanical weak-spot, with strengths of the order of 10 - 90 % of the material potential.

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    What determines friction between thermoplastic components?

    Friction is an important property for thermoplastics in bearings and gears but also has a part to play in assembly of plastic parts (snap-fit and interference-fit) and ejection during moulding.

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    Polypropylene: the Workhorse of the Plastics Industry

    Polypropylene. Little did Karl Zeigler or Giulio Natta realise, 60 years ago, when they were developing a catalyst system to produce a useful thermoplastic from the inexpensive monomer, propylene, that their work would have such far reaching consequences.

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    What makes medical grade plastics so special?

    Toughness and transparency are important properties for the constituents of intravenous lines.

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    The Long and the Short of Fibre Reinforcement of Thermoplastics

    Fibre Reinforcement. The advantages of adding glass fibre to thermoplastics to increase stiffness (modulus), strength, heat distortion resistance and dimensional stability are well known.

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    What causes mouldings (and moulders) to be off-colour?

    When mouldings are not the intended colour, the first thing to check is the raw material, particularly the dosing rate, if you are using masterbatch, and the quality of regrind.

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    Transparent ABS can be a clear winner

    Transparent ABS. Mentioning transparency in the context of ABS moulding materials can raise a few eyebrows. This is because ABS is normally taken to be opaque and indeed the vast majority of grades of ABS are opaque.

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    Understanding the difference between SBS & SEBS thermoplastic elastomers?

    The difference between SBS and SEBS thermoplastic elastomers explained.

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    Is MFR really much help to moulders these days ?

    Often a moulder has to change material grades. One of the first properties to be consulted on the new data sheet is usually the MFR. This is to establish if the new grade has the same melt viscosity performance.

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    What gives Moulders a Warped View on Life?

    Warping is one of the most frustrating injection moulding faults. This is because it does not always appear immediately, the causes are complex and prevention is difficult.

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