Tailoring toughness of injection molded bar of polypropylene random copolymer through processing melt temperature

In all fields of industry it is important to produce parts with good quality. Injection molded parts usually have to meet strict requirements technically and aesthetically. The aim of the measurements presented in our paper is to investigate the aesthetic appearance, such as surface color homogeneity, of injection molded parts. It depends on several factors, the raw material, the colorants, the injection molding machine and the processing parameters. In this project we investigated the effects of the injection molding machine on surface color homogeneity. We focused on injection molding screw tips and investigated five screw tips with different geometries. We produced flat specimens colored with a masterbatch and investigated color homogeneity. To evaluate the color homogeneity of the specimens, we used digital image analysis software developed by us. After that we measured the plastication rate and the melt temperature of the polymer melt because mixing depends on these factors. Our results showed that the screw tips (dynamic mixers) can improve surface color homogeneity but they cause an increase in melt temperature and a decrease in the plastication rate.

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Prediction of crystallinity profile and eject time of injection molded parts using finite element method (FEM)

e-Polymers ◽

10.1515/epoly.2009.9.1.81 ◽

2009 ◽

Vol 9 (1) ◽

Cited By ~ 1

Author(s):

Mehdi Mostafaiyan ◽

Farhad Sharif

Keyword(s):

Finite Element ◽

Degree Of Crystallinity ◽

Element Analysis ◽

Melt Temperature ◽

Crystalline Polymers ◽

Molded Parts ◽

Time Part ◽

Injection Molded ◽

The Subject

AbstractQuality of injection molded parts of semi-crystalline polymers has been the subject of intense interest from both analytical and industrial points of view. Crystallinity profile plays an important role in determining mechanical properties of a part and its quality. Therefore it is important to analyze the effect of injection molding parameters on the crystallinity profile of the molded parts. In this study, finite element analysis has been used to solve the equations of mass, momentum, and energy conservation simultaneously with the equation of crystallization kinetics to predict melt front, its solidification and crystallinity profile. The results from our numerical analysis have been compared with the reported experimental results. Furthermore, progress of the crystallization is proposed to be a proper criterion for estimation of the eject time. Finally, the effects of mold and melt temperature on the eject time; part temperature and average degree of crystallinity, for a specific compound are also presented.

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Effect of Melt Temperature and Hold Pressure on the Weld-Line Strength of an Injection Molded Talc-Filled Polypropylene

Journal of Composites ◽

10.1155/2014/846962 ◽

2014 ◽

Vol 2014 ◽

pp. 1-8 ◽

Cited By ~ 5

Author(s):

Yuanxin Zhou ◽

P. K. Mallick

Keyword(s):

Line Strength ◽

Weld Line ◽

Yield Strain ◽

Stress Strain ◽

Melt Temperature ◽

Strain Behavior ◽

The Core ◽

Nonlinear Constitutive Model ◽

Softening Behavior ◽

Injection Molded

Tensile stress-strain behavior coupled with fractography was used to investigate the weld-line strength of an injection molded 40 w% talc-filled polypropylene. The relationship between processing conditions, microstructure, and tensile strength was established. Fracture surface of the weld line exhibited skin-core morphology with different degrees of talc particle orientations in the core and in the skin. Experimental results also showed that the thickness of the core decreased and the thickness of the skins increased with increasing melt temperature and increasing hold pressure, which resulted in an increase of yield strength and yield strain with increasing melt temperature and increasing hold pressure. Finally, a three-parameter nonlinear constitutive model was developed to describe the strain softening behavior of the weld-line strength of talc-filled polypropylene. The parameters in this model are the modulus E, the strain exponent m, and the compliance factor β. The simulated stress-strain curves from the model are in good agreement with the test data, and both m and β are functions of skin-core thickness ratio.

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