Compounding technology for Epoxy Moulding Compounds (EMC)

 Long known for their good electrical and mechanical properties as well as excellent chemical and aging resistance, epoxy moulding compounds were first described and patented in the 1930s.

Epoxy moulding compounds consist of a polymer matrix (epoxy resins, hardener and accelerator catalyst) mixed with fillers, reinforcing materials, pigments, release agents, etc. and formed into pellets or chips.

Epoxy resin moulding compounds undergo a polyaddition reaction, i.e. no by-products are formed during moulding. Therefore, the same end properties are achieved regardless of the type of moulded part, regardless of wall thickness. Once the reaction is complete in the mould, no further change in mechanical, electrical or thermal properties takes place. Post-curing is not required and post-shrinkage due to the reaction is virtually zero. This is also one of the reasons for the excellent long-term thermal stability of epoxy moulding compounds.

Typical applications

EMC thus meet demanding requirements for a wide range of applications in electronics, medical technology and the automotive industry. With the ongoing miniaturization of electrical components and the simultaneous increase in their performance, the requirements for insulating encapsulation systems that protect against environmental influences are becoming increasingly stringent. In medical technology, for example, they must be able to withstand numerous sterilization processes without damage and exhibit a high degree of resistance to X-rays.

Compounding requirements

Central requirement in the preparation of epoxy resin moulding compounds, apart from the gentle incorporation of high additive proportions, is to maintain the absolute temperature limit below the cross-linking temperature. The Buss Kneader achieves this in an outstanding manner due to its operating principle, in which a relaxation sequence takes place after each gentle shear cycle. The optimum process temperatures can be recorded at any time by exact measurement of the product temperature via drilled kneading pins. This data can also be used as proof of quality assurance. Thanks to customized solutions according to material, service lives in the process chamber are above average.

With cost-effective throughputs and all the advantages of continuous production, such as extremely constant and traceable product quality, high utilisation factor and plant availability, the Buss Kneader technology is certainly well proven in this field.

Backed by broad-based Buss process expertise, Buss Kneaders are therefore first choice for the continuous preparation of epoxy moulding compounds.

Typical plant layout for EMC

BUSS compounding systems for EMC offer the following specific benefits

  • Intensive distributive mixing at low temperatures
    The Buss Kneader achieves intensive distributive mixing because the combined rotation and axial motion of the Kneader screw generates extensional flow, a large number of shear interfaces, and cross channel mixing. The energy for melting and mixing is provided almost entirely mechanically and optimally dissipated according to the imparted shear rates.

  • High filler loadings
    Filler loadings up to 90% are possible with Buss technology thanks to additional inlet openings, split feed of fillers, removal of trapped air by back venting, and excellent conveying efficiency. Moderate shear rates allow perfect handling of the highest viscosities at such high loadings.

  • Uniform, moderate shear rates
    Uniformly moderate shear rates allow controlled mixing at low-temperatures while imparting only the required shear for the specific task. A narrow shear rate distribution compared to alternative systems ensures uniform shear histories for every individual particle. This results in high quality compounding with reduced energy input.

  • Precise Temperature Control
    The Buss Kneader technology has been widely recognized for precise temperature control since more than 6 decades. This is achieved via controlled energy input due to uniform, moderate shear rates and precise temperature monitoring by thermocouples mounted in pins at any position along the process section.

  • Highly wear resistant material
    Novel carbide alloys provide outstanding performance for highly abrasive application such as EMC. Elements and kneading pins lifetime could be increased by a factor of 5 compared to traditional wear resistant materials.

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