Distribution of fillers and reinforcements in injection moulded thermoplastic composites: Case study of glass bubbles

Abstract

Apart from the complex nature of natural fibers, studying glass bubbles, as reinforcement phase, is considered a good start to understand the flow behaviour of fillers or reinforcements and hence their distribution in the final products after injection moulding. Glass bubbles are thermally stable within the processing temperatures of Polypropylene. They are also void from the effect of fibre aspect ratio. This work explores the uneven glass bubbles content along injection moulded spirals out of polypropylene (PP). Glass bubbles are experimented at 10 and 30% volume fraction Vf levels. The processing temperature during the injection moulding varies in the range of 180-200°C. Injection pressure is changed from 250 to 1000 bar. Flow speed is adjusted at two levels of 60and 100 cm3/s. The response measurement is the distribution of the glass bubbles across the spiral at different distances from the injection point. The experimental results show the significance of the nominal Vf, pressure, temperature and flow speed on the distribution homogeneity where the bubbles move further in case of 30% at high pressure of 1000 bar and higher temperature of 200°C that eases the flow. At 10% Vf, the fluctuations in the measured Vf is minimal. The reason of the fluctuation in case of 30% Vf at high temperature and pressure is the multi-phase flow where the investigation shows that bigger size of bubbles acquires greater momentum to flow. Scaling-up of this study to the synthetic fibres will cover fragmentation. More up-scaling to the case of the natural fibre thermoplastic composites NFTC can deal with other factors like thermal stability and fibre splicing or branching.