A systematic study on the effect of processing conditions on mold shrinkage was undertaken for seven common thermoplastic polymers. It turned out that the holding pressure was ahvays the key parameter. The effect of the melt temperature is slightly less important. Injection velocity and mold temperature do not show a general trend for all polymers. It was shown that at least for amorphous polymers a simple thermoelastic model could describe all experimental results. For semi-crystalline materials the model overpredicts shrinkage.

In this paper, a method to fabricate radio frequency (RF) circuit structures is described. This method involves inkjet printing of a silver nanoparticle-based ink on a functional substrate material to create the seed track (i.e., the seed layer), onto which copper is subsequently deposited by an electroless plating method, to obtain the desired thickness and conductivity of the RF structures. This process combination was validated by fabricating an S-band filter on a high-frequency substrate and comparing the RF performance of this filter with that of a filter fabricated using the conventional lithography-based method. The adhesion of the circuit structures to the substrate was qualitatively ascertained by the scotch tape test method. The performance of the inkjet-printed-electroless-plated filter was comparable to that of the conventional filter, thus proving the suitability of this novel method for practical RF applications.

The deformation mechanisms in polypropylene as a function of strain rate have been studied by scanning electron microscopy. Injection molded, dogbone specimens were tested in tension at a temperature of 50°C and strain rates from 10−4 to 90 s−1. With increasing strain rate a gradual transition from cold drawing and necking to nearly homogeneous deformation was observed. The transition is characterized by a strong elastic recoil after fracture. At \documentclass{article}\pagestyle{empty}\begin{document}$ {\rm \dot \varepsilon } $\end{document} = 90 s−1, the elastic recovery has its maximum value of 70% of the strain at break (ε = 0.3). The morphology was studied post mortem at small strains outside the neck using permanganically etched samples. The transition in the macroscopic behavior was found to coincide with a change in the deformation mechanism. Whereas yielding is the dominant mechanism at low strain rates, homogeneous voiding is found at \documentclass{article}\pagestyle{empty}\begin{document}$ {\rm \dot \varepsilon } $\end{document} = 90 s−1. A correlation is suggested between the failure of chain slip within the lamellae and the occurrence of voiding, leading to distinct voiding patterns in the spherulites.

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This paper includes a systematic study of the effect of fiber concentration and molding conditions on fiber orientation and shrinkage in injection molded composites. Closed-form expressions were derived to relate shrinkage and internal stresses to the molding pressure and fiber orientation. The shrinkage predictions were seen to agree well with experimentally measured shrinkages.