scholarly journals Causes of the Gloss Transition Defect on High-Gloss Injection-Molded Surfaces

Polymers ◽  
2020 ◽  
Vol 12 (9) ◽  
pp. 2100 ◽  
Author(s):  
Jinsu Gim ◽  
Eunsu Han ◽  
Byungohk Rhee ◽  
Walter Friesenbichler ◽  
Dieter P. Gruber
Keyword(s):  
Polymer Surface ◽  
Process Condition ◽  
Mold Temperature ◽  
Mold Surface ◽  
Flow Front ◽  
Front Speed ◽  
Surface Stiffness ◽  
Molding Condition ◽  
Injection Molded ◽  
Surface Gloss

The gloss transition defect of injection-molded surfaces should be mitigated because it creates a poor impression of product quality. Conventional approaches for the suppression of the gloss transition defect employ a trial-and-error approach and additional equipment. The causes of the generation of a low-gloss polymer surface and the surface change during the molding process have not been systematically analyzed. This article proposes the causes of the generation of a low-gloss polymer surface and the occurrence of gloss transition according to the molding condition. The changes in the polymer surface and gloss were analyzed using gloss and topography measurements. The shrinkage of the polymer surface generates a rough topography and low glossiness. Replication to the smooth mold surface compensates for the effect of surface shrinkage and increases the surface gloss. The surface stiffness and melt pressure influence the degree of mold surface replication. The flow front speed and mold temperature are the main factors influencing the surface gloss because they affect the development rate of the melt pressure and the recovery rate of the surface stiffness. Therefore, the mold design and process condition should be optimized to enhance the uniformity of the flow front speed and mold temperature.

scholarly journals Dielectric Spectroscopy of PP/MWCNT Nanocomposites: Relationship with Crystalline Structure and Injection Molding Condition

Nanomaterials ◽  
2021 ◽  
Vol 11 (2) ◽  
pp. 550
Author(s):  
Marco Monti ◽  
Marta Zaccone ◽  
Alberto Frache ◽  
Luigi Torre ◽  
Ilaria Armentano
Keyword(s):  
Injection Molding ◽  
Crystalline Structure ◽  
Processing Condition ◽  
Mold Temperature ◽  
Dielectric Behavior ◽  
Multi Walled Carbon Nanotube ◽  
Molding Condition ◽  
Frequency Independent ◽  
Injection Molded ◽  
Independent Behavior

In this paper, we study the correlation between the dielectric behavior of polypropylene/multi-walled carbon nanotube (PP/MWCNT) nanocomposites and the morphology with regard to the crystalline structure, nanofiller dispersion and injection molding conditions. As a result, in the range of the percolation threshold the dielectric behavior shifts to a more frequency-independent behavior, as the mold temperature increases. Moreover, the position further from the gate appears as the most conductive. This effect has been associated to a modification of the morphology of the MWCNT clusters induced by both the flow of the molten polymer during the processing phase and the variation of the crystalline structure, which is increasingly constituted by γ-phase as the mold temperature increases. The obtained results allow one to understand the effect of tuning the processing condition in the frequency-dependent electrical behavior of PP/MWCNT injection-molded nanocomposites, which can be successfully exploited for an advanced process/product design.

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 Mechanical Properties Distribution within Polypropylene Injection Molded Samples: Effect of Mold Temperature under Uneven Thermal Conditions

Polymers ◽  
2017 ◽  
Vol 9 (11) ◽  
pp. 585 ◽  
Author(s):  
Sara Liparoti ◽  
Vito Speranza ◽  
Andrea Sorrentino ◽  
Giuseppe Titomanlio
Keyword(s):  
Mechanical Properties ◽  
Thermal Conditions ◽  
Mold Temperature ◽  
Injection Molded

Tolerance Variation and Passive Alignment in Modular, Polymer Microfluidic Devices

2006 ◽  
Author(s):  
Byoung Hee You ◽  
Daniel S. Park ◽  
Christopher W. Mock ◽  
Wilfredo M. Caceres ◽  
Dimitris E. Nikitopoulos ◽  
...  
Keyword(s):  
Surface Temperature ◽  
Microfluidic Devices ◽  
Mold Surface ◽  
Injection Point ◽  
Replication Fidelity ◽  
Commercial Package ◽  
Assembly Features ◽  
Injection Molded ◽  
Successful Replication ◽  
Passive Alignment

Simulations and experiments to assess the predictability of dimensional and locational tolerances of passive alignment structures on injection molded microfluidic components were performed. A center-gated disk with microscale assembly features, to aid metrology, was reproduced using injection molding. The feature dimensions were 100, 200, 300, and 400 μ. Dimensions of the features were measured using optical profilometery and optical microscopy. Simulations using a commercial package overestimated replication fidelity. Mold surface temperatures and injection speeds significantly affected the replication fidelity as the ratio of surface area to volume increased. The location of better replication fidelity, at each mold surface temperature, moved from the edge of the mold cavity to the injection point as the mold surface temperature increased from 100°C to 150°C. Therefore, process parameters and the design of a mold have to be considered for successful replication of the features.

scholarly journals Effect of Mold Temperature on the Impact Behavior and Morphology of Injection Molded Foams Based on Polypropylene Polyethylene–Octene Copolymer Blends

Polymers ◽  
2019 ◽  
Vol 11 (5) ◽  
pp. 894 ◽  
Author(s):  
Santiago Muñoz-Pascual ◽  
Eduardo Lopez-Gonzalez ◽  
Cristina Saiz-Arroyo ◽  
Miguel Angel Rodriguez-Perez
Keyword(s):  
Impact Resistance ◽  
Mold Temperature ◽  
Impact Behavior ◽  
Critical Parameters ◽  
Crystalline Morphology ◽  
Copolymer Blends ◽  
Opposite Trend ◽  
Izod Impact ◽  
Injection Molded ◽  
The Impact

In this work, an isotactic polypropylene (PP) and a polyethylene–octene copolymer (POE) have been blended and injection-molded, obtaining solids and foamed samples with a relative density of 0.76. Different mold temperature and injection temperature were used. The Izod impact strength was measured. For solids, higher mold temperature increased the impact resistance, whereas in foams, the opposite trend was observed. In order to understand the reasons of this behavior, the morphology of the elastomeric phase, the crystalline morphology and the cellular structure have been studied. The presence of the elastomer near the skin in the case of high mold temperature can explain the improvement produced with a high mold temperature in solids. For foams, aspects as the elastomer coarsening in the core of the sample or the presence of a thicker solid skin are the critical parameters that justify the improved behavior of the materials produced with a lower mold temperature.

Warpage Measurement of a Micro Electrical Fan on Micro-Injection Molding

2012 ◽  
Vol 184-185 ◽  
pp. 1651-1654
Author(s):  
Jeou Long Lee ◽  
Y. Lin ◽  
Y.K. Shen
Keyword(s):  
Injection Molding ◽  
Injection Pressure ◽  
Acrylonitrile Butadiene Styrene ◽  
Mold Temperature ◽  
Micro Injection Molding ◽  
Optimum Result ◽  
Suitable Material ◽  
Packing Pressure ◽  
Injection Molded ◽  
Packing Time

This study characterizes warpage of a micro-injection molded micro electrical fan using the Michelson interference method. This study conducts experiments to analyze different polymers-polypropylene (PP), polyamide (PA), acrylonitrile-butadiene styrene (ABS), ABS+ polycarbonate (PC), and polyoxymethylene (POM)-process parameters, such as mold temperature, injection temperature, injection pressure, injection time, packing time, and packing pressure, for a micro electrical fan. To obtain the optimum result (minimum warpage), this study assesses the effect (warpage) of each material on micro-injection molding. PA plastic is the very suitable material for micro electrical fan with Michelson interference analysis on micro-injection molding.

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