Compression moulding compound

Towflex (Hexcel Composites) is based on carbon, glass or aramid fibres impregnated with polypropylene, polyamide, PPS, polyetherimide, PEEK. Product forms include flexible Towpreg, woven fabric, braided sleeving, UD tape, chopped compression moulding compound, moulded plates, thermoformable laminates. 

Transfer moulding, injection moulding, compression moulding compounds. 

Features Plasticized and plasticizer-free grades Injection moulding, extrusion and compression moulding compounds. 

One limitation of epoxide moulding compositions is their short shelf life (typically 1-3 months), which necessitates strict stock control. The compounds may be compression, transfer or injection moulded, although compression moulding is preferred for long-fibre grades. 

Since 1960, the inner core has been made from c/5-poly-butadiene by the compression moulding technique. This replaced the earlier material made from a suspension of barytes or bentonite clay in water and glycerine or the winding of rubber threads made from t /5-polyisoprene, either from latex or a dry rubber compound. A typical thread recipe is given Table 4. 

In more recent work, talc-filled polystyrene compounds, with various filler volume fractions, have been processed by compression moulding and through a variety of slit, capillary, rectangular and annular dies [37]. Particle orientation has been characterised using wide angle X-ray diffraction, then expressed in the form of pole figures, and by scanning electron microscopy. It was concluded that... 

Transfer moulding involves the distribution of the uncured stock from one part of the mould called as pot into the actual mould cavity. This process permits the moulding of intricate shapes or the introduction of inserts like metals in many composite products. These procedures are difficult in compression moulds. Although these moulds are relatively more expensive than compression moulds, the actual process permits shorter cure times through the use of higher temperatures and better heat transfer which is obtained due to higher pressure applied to force the compound into the mould. 

Three types of moulding processes are available - compression, transfer and injection moulding. In compression moulding the rubber blank is placed directly into the cavity of the mould where it is heated by conduction which causes rubber flow by application of pressure. Transfer moulding uses prewarmed rubber which is heated during transfer and forced through small orifices into the mould cavities in a three-part mould. In the injection moulding process, the rubber compound is pushed under pressure from an injection head where it has been heated and plasticized into a closed heated mould where cure is completed. 

Processing variables can affect to a very great extent the results obtained on the rubber product or test piece and, in fact, a great number of physical tests are carried out in order to detect the result of these variables, for example state of cure and dispersion. In a great many cases, tests are made on the factory prepared mix or the final product as it is received but, where the experiment involves the laboratory preparation of compounds and their moulding, it is sensible to have standard procedures to help reduce as far a possible sources of variability. Such procedures are provided by ISO 2393 which covers both mills and internal mixers of the Banbury or Intermix type, and also procedures for compression moulding. 

Compression moulding (hot press moulding) Moulding compounds (often complex mixtures, e.g. dough or bulk moulding compounds) prepared in Z-blade mixer and heated under pressure in closed mould Small to medium articles, especially electrical mouldings large capital outlay... 

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