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Home Work 2

Home work 2

Q Q1. True or False Questions (put “T” or “F” below for each questions, each 10 points) 1.To shape a thermoplastic polymer, it must be heated so that it softens to the consistency of a liquid. 2.Polymer melt typically display a shear-thinning behavior, which means that as the shear rate increases, the viscosity decreases. 3.The shear rate of 103 s-1 is the typical shear rate in injection molding. 4. The L/D ratios for screws are usually between 10 and 30: lower ratios for thermoplastics, higher ratios for elastomers. 5.For plastics, their dimensional changes, due to temperature changes, are much less significant than for metals.

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1. _T__ To shape a thermoplastic polymer, it must be heated so that it softens to the consistency of a liquid. 2. ___T_ Polymer melt typically display a shear-thinning behavior, which means that as the shear rate increases, the viscosity decreases. 3. __T_ The shear rate of 103 s-1 is the typical shear rate in injection molding. 4. __F__ The L/D ratios for screws are usually between 10 and 30: lower ratios for thermoplastics, higher ratios for elastomers. 5. __F__ For plastics, their dimensional changes, due to temperature changes, are much less significant than for metals.