Micro injection molding processing of UHMWPE using ultrasonic vibration energy

Publication date: 15 October 2017
Source:Materials & Design, Volume 132
Author(s): Xavier Sánchez-Sánchez, Marcelo Hernández-Avila, L.E. Elizalde, Oscar Martínez, Inés Ferrer, Alex Elías-Zuñiga
Ultrasonic micro injection molding was confirmed to be an efficient processing technique for the fabrication of a well-filled miniaturized dog-bone shaped specimen of ultra-high molecular weight polyethylene (UHMWPE). The influence of four process parameters on the filling phase of the reduced-size cavity was then analysed. It was established that it is possible to fabricate well-defined specimens when the highest ultrasonic amplitude is applied intermittently at specific intervals during the ultrasonic process to small compacted irregularly shaped UHMWPE samples and the mold temperature is set to 100°C. GPC results showed a decrease in the molecular weight, which was the greatest when 100% of the ultrasonic amplitude was applied. The degree of crystallinity of the processed sample was increased because the reduction of the molecular weight. TGA showed that the thermal stability of UHMWPE fabricated by ultrasonic processing was not significantly influenced by the decrease in the molecular weight. FTIR spectra indicated oxidative degradation in three different regions of the processed UHMWPE specimen. Additionally, the band identified at the wavenumber 910cm⁻¹ indicated a chain scission phenomenon the polymer experienced during the ultrasonic processing.

Graphical abstract

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