Residual stresses determination in injection molded virgin and recycled HDPE blends: mechanical properties and morphology

e-Polymers ◽  
2008 ◽  
Vol 8 (1) ◽  
Author(s):  
Mirigul Altan ◽  
Mehmet Emin Yurci ◽  
Nihan Nugay
Keyword(s):  
Elastic Modulus ◽  
Impact Strength ◽  
Residual Stresses ◽  
Thermal Stresses ◽  
Mold Temperature ◽  
Morphological Properties ◽  
Time Layer ◽  
Melt Temperature ◽  
Injection Molded ◽  
Recycled Hdpe

AbstractAn experimental study of residual thermal stresses has been carried out in injection molded virgin and recycled high density polyethylene (HDPE) blends. Effects of blend concentrations on residual stresses were investigated under different injection conditions such as melt temperature, mold temperature and cooling time. Layer removal technique was used for measuring residual stresses. In order to determine the relation between the residual stresses and material characteristic of HDPE blends, mechanical and morphological properties of the blends were also investigated. Elastic modulus and impact strength were important key factors for determining the blend characteristics. As a result, it was found that HDPE blends gave higher residual stresses but lower impact strength with higher elastic modulus when recycled concentration was increased. Furthermore, it was seen that shape and size of the crystallites were also effective on residual stresses. Small and spherulitic crystallite structured blends such as 30 % recycled HDPE induced reduction in residual stresses due to easier relaxation with lower elastic modulus and higher impact strength while lamellar crystallite structured blends such as 50 % recycled HDPE gave higher elastic modulus but lower impact strength with higher residual stresses.

scholarly journals Post-Processing Time Dependence of Shrinkage and Mechanical Properties of Injection-Molded Polypropylene

Materials ◽  
2020 ◽  
Vol 14 (1) ◽  
pp. 22
Author(s):  
Artur Kościuszko ◽  
Dawid Marciniak ◽  
Dariusz Sykutera
Keyword(s):  
Mechanical Properties ◽  
Impact Strength ◽  
Injection Molding ◽  
Accelerated Aging ◽  
Mold Temperature ◽  
Degree Of Crystallinity ◽  
Injection Mold ◽  
Secondary Crystallization ◽  
Scanning Calorimetry ◽  
Injection Molded

Dimensions of the injection-molded semi-crystalline materials (polymeric products) decrease with the time that elapses from their formation. The post-molding shrinkage is an effect of secondary crystallization; the increase in the degree of polymer crystallinity leads to an increase in stiffness and decrease in impact strength of the polymer material. The aim of this study was to assess the changes in the values of post-molding shrinkage of polypropylene produced by injection molding at two different temperatures of the mold (20 °C and 80 °C), and conditioned for 504 h at 23 °C. Subsequently, the samples were annealed for 24 h at 140 °C in order to conduct their accelerated aging. The results of shrinkage tests were related to the changes of mechanical properties that accompany the secondary crystallization. The degree of crystallinity of the conditioned samples was determined by means of density measurements and differential scanning calorimetry. It was found that the changes in the length of the moldings that took place after removal from the injection mold were accompanied by an increase of 20% in the modulus of elasticity, regardless of the conditions under which the samples were made. The differences in the shrinkage and mechanical properties of the samples resulting from mold temperature, as determined by tensile test, were removed by annealing. However, the samples made at two different injection mold temperature values still significantly differed in impact strength, the values of which were clearly higher for the annealed samples compared to the results determined for the samples immediately after the injection molding.

scholarly journals Simulation and Optimization of Short Fiber Circumferential Orientation in Short-Fiber-Reinforced Composites Overflow Water-Assisted Injection Molded Tube

2019 ◽  
Vol 2019 ◽  
pp. 1-10 ◽  
Author(s):  
Haiying Zhou ◽  
Hesheng Liu ◽  
Tangqing Kuang ◽  
Qingsong Jiang ◽  
Zhixin Chen ◽  
...  
Keyword(s):  
Delay Time ◽  
Water Pressure ◽  
Mold Temperature ◽  
Short Fiber ◽  
Range Analysis ◽  
Melt Temperature ◽  
Simulation And Optimization ◽  
Experimental Scheme ◽  
Filling Time ◽  
Injection Molded

The mechanical properties of the water-assisted injection molded tube can be enhanced by the increase in the short fiber circumferential orientation (SFCO). Thus, the numerical method verified by experiments is used to simulate the SFCO distribution in the overflow water-assisted injection molding (OWAIM), with the mechanism of short fiber orientation analyzed as well. The effect of parameters (filling time, melt temperature, mold temperature, delay time, water pressure, and water temperature) on the SFCO is explored by range analysis and variance analysis of the orthogonal experimental scheme. Moreover, both of artificial neural network (ANN) and genetic algorithm (GA) are used to model and optimize process parameters. Results show that the melt temperature, delay time, and water pressure are predominant parameters. The evolution of SFCO increases with the increase of melt temperature and water pressure, whereas the changes in delay time reverse. The value of the maximum SFCO tensor obtained by GA optimization is found to be 0.234.

Thermal Stresses in Nonlinearly Viscoelastic Solids

1992 ◽  
Vol 59 (2S) ◽  
pp. S43-S49 ◽  
Author(s):  
Giancarlo U. Losi ◽  
Wolfgang G. Knauss
Keyword(s):  
Glass Transition ◽  
Residual Stresses ◽  
Free Volume ◽  
Thermal Stresses ◽  
Morphological Changes ◽  
Polymer Chains ◽  
Transition Range ◽  
Rheological Models ◽  
Molded Parts ◽  
Injection Molded

Three different rheological models are applied to the study of transient and residual thermal stresses in amorphous polymers cooled across the glass transition. The models differ mainly in their treatments of the nonequilibrium (time-dependent) portion of the morphological changes in the polymer and their influence on the relaxation process. The interstitial volume between polymer chains (free volume) is found to play an important role in the residual stresses; they are affected by the relative time scale of thermal diffusion and thermoviscoelastic relaxation/creep. This result has implications for injection molded parts of different section dimensions and for extrusion products. This fact must also be accounted for in determining the thermomechanicalproperties in the glass transition range. The step cooling ofPVAc spheres (1 and 20 mm dia.) and a cylinder (20 mm dia.) have been considered; most of the results presented apply to the sphere(s). Residual stresses can vary by as much as 100percent depending on whether the interstitial molecular (free) volume is counted or not. It is also demonstrated that residual stresses can be higher than an elastic analysis based on the glassy properties would suggest; thus the “stressfree temperature” is found to be significantly above the glass transition.

scholarly journals Characterization of Microchannel Replicability of Injection Molded Electrophoresis Microfluidic Chips

Polymers ◽  
2019 ◽  
Vol 11 (4) ◽  
pp. 608 ◽  
Author(s):  
Bingyan Jiang ◽  
Laiyu Zhu ◽  
Liping Min ◽  
Xianglin Li ◽  
Zhanyu Zhai ◽  
...  
Keyword(s):  
Microfluidic Chip ◽  
Mold Temperature ◽  
Disease Diagnosis ◽  
Injection Rate ◽  
Holding Time ◽  
Critical Element ◽  
Profile Curve ◽  
Microfluidic Chips ◽  
Melt Temperature ◽  
Injection Molded

Microfluidic chips have been widely applied in biochemical analysis, DNA sequencing, and disease diagnosis due to their advantages of miniaturization, low consumption, rapid analysis, and automation. Injection molded microfluidic chips have attracted great attention because of their short processing time, low cost, and mass production. The microchannel is the critical element of a microfluidic chip, and thus the microchannel replicability directly affects the performance of the microfluidic chip. In the current paper, a new method is proposed to evaluate the replicability of the microchannel profile via the root mean square value of the actual profile curve and the ideal profile curve of the microchannel. To investigate the effects of injection molding parameters (i.e., mold temperature, melting temperature, holding pressure, holding time, and injection rate) on microchannel replicability, a series of single-factor experiments were carried out. The results showed that, within the investigated experimental range, the increase of mold temperature, melt temperature, holding pressure, holding time, and injection rate could improve microchannel replicability accuracy. Specifically, the microchannels along the flow direction of the polymer melt were significantly affected by the mold temperature and melt temperature. Moreover, the replicability of the microchannel was influenced by the distance from the injection gate. The effect of microchannel replication on electrophoresis was demonstrated by a protein electrophoresis experiment.

Influence of Process Parameters on Plastic Injection Molding of Automobile Interior Trim

2011 ◽  
Vol 189-193 ◽  
pp. 1675-1680
Author(s):  
Qing Qing Liu ◽  
Lin Hua ◽  
Wei Guo
Keyword(s):  
Mold Temperature ◽  
Process Conditions ◽  
Injection Time ◽  
Molding Process ◽  
Melt Temperature ◽  
Influence Of Process Parameters ◽  
Packing Pressure ◽  
Optimal Setting ◽  
Injection Molded ◽  
Packing Time

The influence of process conditions on the formability of injection-molded PX0034 (9% talc-filled PP) automobile B column mounting trim applied as a model has been studied in current work. This study has been focused on the interactive influence of melt temperature and mold temperature, the interactive influences of injection time and packing time and the influences of packing pressure. Weighting the effect of optimization is by formability including the values of pressure at V/P switchover, volumetric shrinkage differential at ejection, and maximum warpage. Aforementioned values were obtained by numerical simulation of the whole molding process using commercial dedicated code Moldflow. Results indicate that the combination of mold temperature at 25 °C, melt temperature at 220 °C, injection time at 2.2 s, packing time at 16 s and packing pressure at 90% of the filling pressure is the optimal setting for formability of this trim. The simulation results obtained under the optimized parameters are that the pressure at V/P switchover is 27.29 Mpa, the shrinkage differential at ejection is 6.55 %, and maximum warpage is 3.072 mm. Good correlation is highlighted between the experiments and the simulations by comparing effects of the global optimization in formability, which verifies the validity of the optimal combination.

scholarly journals Study of the Mechanical and Morphology Properties of Recycled HDPE Composite Using Rice Husk Filler

2014 ◽  
Vol 2014 ◽  
pp. 1-6 ◽  
Author(s):  
Jia Ying Tong ◽  
Nishata Royan Rajendran Royan ◽  
Yong Chuen Ng ◽  
Mohd Hafizuddin Ab Ghani ◽  
Sahrim Ahmad
Keyword(s):  
Impact Strength ◽  
Rice Husk ◽  
Morphological Properties ◽  
Flexural Properties ◽  
Twin Screw Extrusion ◽  
Screw Extrusion ◽  
Twin Screw ◽  
The Impact ◽  
Extrusion Method ◽  
Recycled Hdpe

WPCs are being used in a large number of applications in the automotive, construction, electronic, and aerospace industries. There are an increasing number of research studies and developments in WPC technology involving rice husk as fillers. This study investigated the effects of different compositions of rice husk (RH) filler on the mechanical and morphological properties of recycled HDPE (rHDPE) composite. The composites were prepared with five different loading contents of RH fibers (0, 10, 20, 30, and 40 wt%) using the twin screw extrusion method. Maleic acid polyethylene (MAPE) was added as a coupling agent. Results showed that tensile and flexural properties improved with increasing RH loading. However, the impact strength of the composites decreased as the RH loading increased. SEM micrographs revealed good interfacial bonding between the fiber and polymer matrix.

scholarly journals Thermoplastic Overmolding onto Injection-Molded and In Situ Polymerization-Based Polyamides

Materials ◽  
2018 ◽  
Vol 11 (11) ◽  
pp. 2140 ◽  
Author(s):  
Róbert Boros ◽  
Praveen Rajamani ◽  
József Kovács
Keyword(s):  
In Situ Polymerization ◽  
Mold Temperature ◽  
Technological Parameters ◽  
Temperature Dependent ◽  
Welding Zone ◽  
Melt Temperature ◽  
Injection Molded ◽  
The Individual ◽  
Dependent Mass

We investigated products manufactured by in situ polymerization, which were reinforced with overmolded ribs. We developed our own mold and prototype product for the project. We used three different materials as preform: a material with a magnesium catalyst, manufactured by in situ polymerization, a Brüggemann AP-NYLON-based in situ polymerization material and an injection-molded PA6 (Durethan B30S, Lanxess GmbH) material. The ribs were formed from the same PA6 material (Durethan B30S, Lanxess GmbH). We examined the effect of the different technological parameters through the pull-off of the overmolded ribs. We measured the effect of melt temperature, holding pressure and holding time, and mold temperature. Considering the individual preforms, we pointed out that monomer migration and binding strength are related, which we concluded from the temperature-dependent mass loss of the materials, measured by thermogravimetric analysis (TGA). Finally, we designed a mold suitable for manufacturing overmolded parts. We designed and built pressure and temperature sensors into the mold to examine and analyze pressures and temperatures around the welding zone of the materials.

scholarly journals Effect of Process Parameters on Repeatability Precision of Weight for Microinjection Molding Products

2019 ◽  
Vol 2019 ◽  
pp. 1-8
Author(s):  
Quan Wang ◽  
Jinrong Wang ◽  
Chongying Yang ◽  
Kaihui Du ◽  
Wenli Zhu ◽  
...  
Keyword(s):  
Orthogonal Experiment ◽  
Mold Temperature ◽  
Tensile Specimen ◽  
Cavity Pressure ◽  
Melt Temperature ◽  
Microinjection Molding ◽  
Packing Pressure ◽  
Impact Specimen ◽  
Injection Molded ◽  
The Impact

The repeatability precision of weight for injection molded products is important technical parameter to measure the quality and accuracy of injection molded products and evaluate the performance of injection molding machine. The influence of mold temperature, melt temperature, packing pressure, and packing time on the weight of microinjection molding products was studied by Taguchi orthogonal experiment. The influence of peak cavity pressure on the weight of products also was analysed. The experimental results show that the packing pressure is the most important process parameter affecting both the weight of the tensile and the impact specimens. With the increase of the packing pressure, the weight of the tensile and the impact specimens increases. When the peak cavity pressure reaches a certain value, the pressure value of the tensile specimen is 65 MPa, and the pressure value of the impact specimen is 68 MPa, the weight of the product increases quickly. The packing pressure increased from 85 MPa to 100 MPa, the weight of the tensile specimen increased from 0.544g to 0.559g, an increase of 2.7%, and the weight of the impact specimen increased from 0.418g to 0.425g, an increase of 1.7%.

Correlation Between Mechanical Properties in Standard Test Specimens and Injection Molded Thin-Wall Parts

2013 ◽  
Author(s):  
Laurentiu I. Sandu ◽  
Felicia Stan ◽  
Catalin Fetecau
Keyword(s):  
Mechanical Properties ◽  
Elastic Modulus ◽  
Yield Strength ◽  
Injection Molding ◽  
Process Conditions ◽  
Thin Wall ◽  
Optimal Process ◽  
Melt Temperature ◽  
Molded Parts ◽  
Injection Molded

In this paper, we investigated the effect of injection molding parameters on the mechanical properties of thin-wall injection molded parts. A four-factor (melt temperature, mold temperature, injection speed and packing pressure) and three-level fractional experimental design was performed to investigate the influence of each factor on the mechanical properties and determine the optimal process conditions that maximize the mechanical properties of the part using the signal-to-noise (S/N) ratio response. The mechanical properties (e.g., elastic modulus, yield strength and strain at break) were measured by tensile tests at room temperature, at a crosshead speed of 5 mm/min, and compared with those of the injection-molded specimens. The experimental results showed that the tensile properties were highly dependent on the injection molding parameters, regardless of the type of the specimens. The values of Young modulus and yield strength of the injection-molded specimens were lower than those of the injection-molded parts, while the elongation at break was considerably lower for the injection-molded parts. The optimal process conditions were strongly dependent on the measured performance quantities (elastic modulus, yield strength and strain at break).

Injection Molding of PC/PMMA Blend for Fabricate of the Secondary Optical Elements of LED Illumination

2012 ◽  
Vol 579 ◽  
pp. 134-141 ◽  
Author(s):  
Hoang Van Thanh ◽  
Chao Chang Arthur Chen ◽  
Chia Hsing Kuo
Keyword(s):  
Mechanical Properties ◽  
Tensile Strength ◽  
Impact Strength ◽  
Injection Molding ◽  
Mold Temperature ◽  
Injection Molding Process ◽  
Molding Process ◽  
Melt Temperature ◽  
Maximum Tensile Strength ◽  
Pmma Blends

This paper is to investigate the optimization of mechanical properties for the maximum tensile strength, elongation, and impact strength of Polycarbonate and Polymethyl methacrylate (PC/PMMA) blends by injection molding process. The PC/PMMA plastics composites with different blending percentage are first blended have been injected as the tensile and impact specimens designed according to ASTM, type V by injection molding machine. Taguchi’s method is then used to find the optimal parameters for the maximum tensile strength, elongation and impact strength. The control factors selected in this study are melt temperature, packing pressure, mold temperature and cooling time. An ANOVA table has been used for determining the significance of injection molding parameters. Results of experiments show that the melt temperature is the most significant parameter for improvement of mechanical properties of PC-PMMA plastics composites. Blends with high PC concentrations result in low tensile strength and high impact strength. Illumination testing of the tatol internal reflection (TIR) of PC/PMMA blends has been proceeded and the TIR lens illumination intensity is compared with three compositions of the PC/PMMA blends. Illumination results show that the PC/PMMA 80/20 blend has the highest intensity of illumination. Results of this study can be applied on the optimization of injection molding parameters for polymer blends of LED lens.

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