Reactive injection moulding

The move to couple reaction and processing will continue. Reactive injection moulding is a good way to get round the high viscosity processing problem in that the low viscosity material is fed into the mould and the reaction completed within the material. This of course can lead to other complicating issues. 

Keywords Block copolymers, Interface reactive injection moulding, Polyamide degradation, Polyolefine polyamide graft copolymers, PTFE polyamide materials... 

The first results of an interface reactive injection moulding by two-component injection moulding (Fig. 11) are listed in Table 11. 

Typical systems are two-part polyurethane systems that may produce rigid, rubbery, foamed or filled products. Typical fillers include chopped fibres and mineral fillers. Composite systems may also be produced by having pre-placed reinforcements in the mould, in which case the technique is known as reinforced reactive injection moulding (RRIM). 

Sadr A., R. Granger, and J.M. Vergnaud. 1985. Profiles of temperature and state of cure developed within rubber in injection molding systems. American Chemical Society Symposium series Reactive Injection Moulding and Reactive Processes. 18 279-91. 

El Brouzi A., R. Granger, J. Bouzon, and J.M. Vergnaud. 1989. ModeUing and simulation of the process of reactive injection moulding in case of composite with low enthalpy. Plastics Rubber Process. Appl. 12 7-13. 

Reactive injection moulding (used for objects like milk bottle crates). 

Note 3 Reaction injection moulding and reinforced reaction injection moulding are types of reactive polymer processing. 

In blends of polyamide with styrenics, compatibilization of the phases is generally a prerequisite for acceptable mechanical properties. This can be accomplished by having reactive groups in the PSAN phase that react with the amino groups of the polyamide phase. Blending is used to improve the main weaknesses of the polyamide, namely moisture sensitivity, toughness and warp-age on injection moulding. 

The blends (PET plus core-shell elastomers) were compounded using a co-rotating twin screw extruder. The contains of particules ranged from 7 to 21 % in mass. Test bars were injection moulded in a second step. In order to produce compound of different levels of crystallisation, the mould wall temperature was varied. Truly amorphous mouldings could not be obtained. However, for mould temperature of 5°C only a small amount (less than 8 %) of crystalline phase was observed. These mouldings will be considered as amorphous, since their continuous phase is amorphous. Conversely, a wall temperature of 145°C made it possible to reach the maximum level of crystallisation (approximately 30 % in mass). Finally, no evidence for a significant crosslinking effect due to reactive nodules was found. 

Finally, crystalline microstructure of PET is not significantly modified by the blending if one except a small nucleating effect of the non-reactive additive that can be observed in laboratory conditions. However, this nucleating effect is not due to the nodule itself [20] as no transcrystallisation can be observed on particles. Additionally, this nucleating effect does not lead to significant evolution in mean spherulite diameter in injection moulded parts. 

Interface Reactive Two-Component Injection Moulding (Core-Back Process).183... 

Interface Reactive Sandwich Moulding as a Special Two-Component Injection... 

Fig. 12 Interface reactive two-component injection moulding - bond strength in dependence on the type of diisocyanate and TPU elastomer. Bond strength between PA-6/TPU. PA-6 Ultramid B3S TPU Elastollan 1185A, Elastolian B 85A, Eiastollan C 85A, Elastollan C 60D. Modifiers diisocyanates MDI, IPDI, IPDI-Uretdion, PBDI, Oligomer-TDI-DI. Addition of 1 up to 5 wt% ...

Fig. 13 Interface reactive two-component injection moulding - image of fractured specimen after tensile test, polyamide bulk material on the TPU fracture surface (right - fracture with coloured TPU part for differentiation)...

Table 12 Interface reactive two-component injection moulding — bond strength betweai different polyamide materials [32]...

Fig. 18 Reactive surface modification injection moulding - assumed model for the reaction rate profile in dependence of the temperature profile and time...

Fig. 20 Reactive surface modification injection moulding — assnmed model for the modified surface after mould filling process...

The described process is simple. The aim was to provide the first evidence for such a reactive surface modification injection moulding process. A transfer to a production system requires an optimisation of the modifier adding process. The principle of the surface modification injection moulding process can also be transferred to extrusion processes for the manufacture of semi-finished and profile products. 

---