Abbasalizadeh M, Hasanzadeh R, Mohamadian Z, Azdast T, Rostami M. Experimental Study to Optimize Shrinkage Behavior of Semi-Crystalline and Amorphous Thermoplastics. IJMSE 2018; 15 (4) :41-51
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http://ijmse.iust.ac.ir/article-1-1010-en.html
Abstract: (19590 Views)
Shrinkage is one of the most important defects of injection molded plastic parts. Injection molding processing parameters have a significant effect on shrinkage of the produced parts. In the present study, the effect of different injection parameters on volumetric shrinkage of two polymers (high-density polyethylene (HDPE) semi-crystalline thermoplastics and polycarbonate (PC) as a representative of amorphous thermoplastics) was studied. Samples under different processing conditions according to a L27 orthogonal array of Taguchi experimental design approach were injected. Effect of material crystallinity on the shrinkage of injected samples was investigated. Obtained results revealed that semi-crystalline thermoplastics have larger shrinkage values in comparison with amorphous thermoplastics. Shrinkages of injected samples were also studied along and across the flow directions. Results showed that the flow path can dramatically affect the shrinkage of semi-crystalline thermoplastics. However for amorphous thermoplastics, results showed an independency of obtained shrinkage to flow direction. Analysis of variance (ANOVA) results illustrated that cooling time was the most effective parameter on shrinkage for both PE and PC injected samples; followed by injection temperature as the second important parameter. The optimum conditions to minimize shrinkage of injection molded samples are also achieved using signal to noise ratio (S/N) analysis.
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- The effect of different injection parameters on volumetric shrinkage was studied.
- Semi-crystalline polymers had noteworthy higher shrinkage compared to amorphous.
- The shrinkages along and across the flow directions were calculated.
- Cooling time was the most effective parameter on shrinkage of PE and PC.
- The optimal conditions for minimization of shrinkages of PE and PC were achieved.