| Polypropylene (PP) is a semicrystalline polymer and is one of the most widely used polymeric materials today. Thermomechanical properties of three kind PPs with high crystallinity, homopolymer and random copolymer are studied. It is found that the properties strongly depend on Wt%-xl, comonomer, strain rates and temperatures, which are the most important parameters in the film fabrication process. Analytical equations between yield stress, strain rate and temperature are creatively deduced for the three kinds PPs. Necking of polyolefins (PE, PP and PB) is studied using Inframatrics during tensile test by observing the temperature changes around the necking propagation boundaries. Thermodynamic analysis about necking is performed.; To simulate film fabrication process in lab scale is a big challenge. Testing set up of simulating MD stretching is creatively established and is performed successfully. Testing set up of simulating MD and TD stretching is also creatively established. But, strain recovery is a big problem during TD starching simulation test. The challenge is to design an effective grip system and specimen to avoid the strain recovery problem. In simulation MD and TD stretching test in lab scale, to quantitatively obtain the stress-strain relationship during TD stretching after MD stretching is very difficult due to gripping problem. |
