Strength mould material

Wall sections in foam moulding are thicker than in solid material. Longer cycle times can therefore be expected due to both the wall thickness and the low thermal conductivity of the cellular material. In contrast, however, the injection pressures in foam moulding are low when compared with conventional injection moulding. This means that less clamping force is needed per unit area of moulding and mould costs are less because lower strength mould materials may be used. 

In the early days nearly all thermosetting moulding materials were composites in that they contained fillers such as woodflour, mica, cellulose, etc to increase their strength. However, these were not generally regarded as reinforced materials in the sense that they did not contain fibres. 

This structural information can also help explain changes observed in the mechanical properties of the nanocomposites. As the amorphous content of the samples decreases from UM to dPC and the material becomes more crystalline, the nanocomposites become stronger. Also in the core of the injection moulded test bars where slow cooling is prevalent, the more stable a structure appears to form readily. As the y crystal structure is said to be more ductile than the a, it would be expected that the tensile strength of materials containing mostly a crystals, like DdPC-OdPC, to be much stronger than those with high levels of y crystal in the core. So not only is the increase in modulus due to the reinforcement provided by the clay layers and increase in crystallinity, but also the reduction in y crystal content. 

BS 2782, Methods 340A and B, Determination of shear strength of moulding material (.340A). Determination of shear strength of sheet material (340B), 1978. 

Figure 3.447. Tensile strength of tested LCPs for both test directions. Visible is the high anisotropy between testing (a) parallel (T) and (b) perpendicular (L) to the mould-filling direction. ( ) Separated skin layer measured, separated core layer measured, ( ) injection+moulded material measured and dl injection-moulded material calculated [1263].

This is manufactured by reacting cellulose with ethyl chloride. It is tough and retains flexibility and impact strength down to -40 °C and has a similar moisture pickup to cellulose acetate. It is widely used as a moulding material and in film manufacture. 

---