No abstract

SYNOPSISPolypropylene (PP) was extruded and injection-molded several times to mimic the effect of recycling procedures on PP. Differential scanning calorimetry (DSC) was used to follow crystallization rates under isothermal conditions in a temperature range of 120-130°C. Melting behavior and equilibrium melting temperatures were studied using the HoffmanWeeks method of extrapolation. Optical microscopy combined with a hot stage was also used to follow the spherulite microstructure and crystal phase upon recycling of PP. Wideangle X-ray spectroscopy identified the crystal phase a t different isothermal crystallization temperatures. Twin melting peaks obtained for PP melting following isothermal crystallization were associated with crystal rearrangement during fusion. PP spherulite size and equilibrium melting temperatures were seen to increase with processing events, whereas reprocessing decreased nuclei density. 0 1996 John Wiley & Sons, Inc.

No abstract

SYNOPSISPolypropylene (PP) was extruded and injection-molded several times to mimic the effect of recycling procedures on PP. Differential scanning calorimetry (DSC) was used to follow crystallization rates under isothermal conditions in a temperature range of 120-130°C. Melting behavior and equilibrium melting temperatures were studied using the Hoffman-Weeks method of extrapolation. Optical microscopy combined with a hot stage was also used to follow the spherulite microstructure and crystal phase upon recycling of PP. Wideangle X-ray spectroscopy identified the crystal phase a t different isothermal crystallization temperatures. Twin melting peaks obtained for PP melting following isothermal crystallization were associated with crystal rearrangement during fusion. PP spherulite size and equilibrium melting temperatures were seen to increase with processing events, whereas reprocessing decreased nuclei density.

Titanium has excellent properties as an engineering material such as light weight, high strength and high resistance to corrosion and fracture. However, the high cost associated with the materials and current process technologies is not conducive to higher-volume production for consumer industry. It appears near net shape manufacturing has to be used to manufacture titanium and titanium alloys parts. Investigators are exploring several near net shape technologies. However, most of these technologies involve melting and solidification. Each new layer starts out molten, solidifies, and must eventually cool to room temperature. Oxygen sensitive material such as titanium needs to be processed under vacuum. There is a great need for revolutionary coating and direct Manufacturing technology to extend the application of titanium and titanium alloys from top end, aerospace and biomedical to lower end consumer use. It appears Cold Spray Technology can deliver a suitable and cost effective coating and direct manufacturing solution for titanium industry. CSIRO Light Metals Flagship has pioneered in developing direct manufacturing technologies to fabricate titanium parts using Cold Spray. Mechanical properties of Cold Spray titanium in as sprayed and heat treated conditions are presented and compared with wrought titanium. Some of technologies such as Cold Spray for direct manufacturing of seamless titanium pipes are discussed.