Influence of supramolecular additives on foam morphology of injection-molded i-PP

2011 ◽  
Vol 47 (6) ◽  
pp. 519-534 ◽  
Author(s):  
Marieluise Stumpf ◽  
Andreas Spörrer ◽  
Hans-Werner Schmidt ◽  
Volker Altstädt
Keyword(s):  
Mechanical Properties ◽  
Injection Molding ◽  
Control Cell ◽  
Large Cell ◽  
Processing Parameters ◽  
Expansion Ratio ◽  
Foam Formation ◽  
Nucleating Agents ◽  
Foam Morphology ◽  
Foam Injection Molding

Foaming isotactic polypropylene (i-PP) by foam injection molding usually results in inhomogeneous, large cell structures. Possibilities to realize more homogeneous and finer foam morphologies are adjusting processing parameters or adding nucleating agents. Often, inorganic nucleating agents such as talc in concentrations of about 2 wt% are used to influence the foam morphology. This article discusses the use of two benzene trisamide-based nucleating agents to control cell nucleation during foaming of i-PP. These additives form supramolecular nanostructures in the polymer melt acting first as nucleating sites for foam formation and second as nuclei for the polymer crystallization. Foaming was performed by foam injection molding with nitrogen as physical blowing agent. A specially designed variotherm mold technology was utilized to exactly control the foaming temperature, foaming pressure, and expansion ratio. Foamed i-PP samples were prepared with a density reduction of 50% and analyzed with respect to foam structure and mechanical properties. We demonstrate that the benzene trisamide additives have a strong influence on the foam morphology at very low additive concentrations. Only 0.02 wt% of an additive is sufficient to obtain a remarkable reduction of the cell sizes. It appears that the cell struts, those dimensions can be influenced by the additives as well, leads to a significant improvement of the mechanical properties.

Process comparison on the microstructure and mechanical properties of fiber-reinforced polyphenylene sulfide using MuCell technology

2018 ◽  
Vol 37 (15) ◽  
pp. 1020-1034 ◽  
Author(s):  
Christoph Lohr ◽  
Björn Beck ◽  
Frank Henning ◽  
Kay André Weidenmann ◽  
Peter Elsner
Keyword(s):  
Mechanical Properties ◽  
High Pressure ◽  
Injection Molding ◽  
Fiber Orientation ◽  
Polyphenylene Sulfide ◽  
Injection Molding Process ◽  
Fiber Reinforced ◽  
Molding Process ◽  
Glass Fiber Reinforced ◽  
Foam Injection Molding

The MuCell process is a special injection molding process which utilizes supercritical gas (nitrogen) to create integral foam sandwiches. The advantages are lower weight, higher specific properties and shorter cycle times. In this study, a series of glass fiber-reinforced polyphenylene sulfide foam blanks are manufactured using the MuCell injection molding process. The different variations of the process (low-pressure also known as structural foam injection molding) and high-pressure foam injection molding (also known as “core back expansion,” “breathing mold,” “precision opening,” decompression molding) are used. The sandwich structure and mechanical properties (tensile strength, bending strength, and impact behavior) of the microcellular and glass fiber-reinforced polyphenylene sulfide foams are systematically investigated and compared to compact material. The results showed that the injection parameters (injection speed, foaming mechanism) played an important role in the relative density of microcellular polyphenylene sulfide foams and the mechanical properties. It could be shown that the specific tensile strength decreased while increasing the degree of foaming which can be explained by the increased number of cells and the resulting cell size. This leads to stress peaks which lower the mechanical properties. The Charpy impact strength shows a significant dependence on the fiber orientation. The specific bending modulus of the high-pressure foaming process, however, surpasses the values of the other two processes showing the potential of this manufacturing variation especially with regard to bending loads. Furthermore, a high dependence of the mechanical properties on the fiber orientation of the tested specimens can be found.

Influence of Processing Parameters in Reaction Injection Foam Molding for Multi-Layer Parts on Foam Structure and Mechanical Properties

2015 ◽  
Vol 805 ◽  
pp. 131-138
Author(s):  
Martin Löhner ◽  
Dietmar Drummer
Keyword(s):  
Mechanical Properties ◽  
Injection Molding ◽  
Chemical Reaction ◽  
Reactive Systems ◽  
Mold Temperature ◽  
Processing Parameters ◽  
Foam Structure ◽  
Blowing Agents ◽  
Reaction Injection Molding ◽  
Plastic Processing

Reaction injection molding is a plastic processing method to produce net shape parts using reactive systems. By integrating semi-finished products as inserts, complex multi-layer parts can be generated in highly integrative and energy efficient processes. The material by far mostly used is polyurethane, a polymer which results from the reaction of isocyanate and polyol. By adding blowing agents, like for example water, to the polyol component, foamed parts can be realized. In contrast to thermoplastic injection molding a chemical reaction takes part during molding within the cavity. Therefore the processing parameters have a significant effect on this chemical reaction and on the properties of the finished part.In this work the influences of different processing parameters like for example mold temperature and injection volume on the resulting foam structure are investigated for reaction injection foam molding. Therefore multi-layer parts based on polyurethane materials (thermoplastic and reactive) were molded varying relevant processing parameters. The foaming took place within an open cavity. The resulting foam structures were characterized using scanning electron microscopy (SEM). Additional the multi-layer parts were characterized mechanically to reveal the resulting effects on the mechanical properties of parts containing a foamed reactive polyurethane component.

Effect of processing condition on properties of polylactic acid parts obtained by foam injection molding

2016 ◽  
Vol 53 (5) ◽  
pp. 491-502 ◽  
Author(s):  
Valentina Volpe ◽  
Roberto Pantani
Keyword(s):  
Mechanical Properties ◽  
Injection Molding ◽  
Polylactic Acid ◽  
Flow Rate ◽  
Flexural Modulus ◽  
Processing Condition ◽  
Blowing Agent ◽  
Injection Flow Rate ◽  
Injection Flow ◽  
Foam Injection Molding

Foam injection molding is a processing technology particularly interesting for biodegradable polymers, which present a very narrow processing window, with the suitable processing temperatures close to the degradation conditions. The addition of a physical blowing agent, besides decreasing the final part weight, reduces both the viscosity and the glass transition temperature of the polymer melt, allowing the processability of these materials at lower temperatures. In this work, structural foams of polylactic acid with nitrogen as physical blowing agent were obtained by foam injection molding. In particular, the effects of back pressure, namely the pressure imposed inside of the cylinder when the screw is returning back to prepare a new amount of material to be injected, and of the injection flow rate on foaming and mechanical properties of the molded parts was assessed. It was found that the samples molded adopting a higher injection flow rate are shorter than those injected at lower flow rate, and this result was ascribed to the large compressibility of the injected shot. As far as the mechanical properties of the foamed parts, it was found that the modulus decreases with decreasing density. However, the density reduction is not the only significant parameter, but also the morphology of the foams should be taken into account in order to justify the differences between tensile and flexural modulus.

Crystallization modification of poly(lactide) by using nucleating agents and stereocomplexation

e-Polymers ◽  
2016 ◽  
Vol 16 (1) ◽  
pp. 1-13 ◽  
Author(s):  
Long Jiang ◽  
Tianfeng Shen ◽  
Pengwu Xu ◽  
Xiyuan Zhao ◽  
Xiaojie Li ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Injection Molding ◽  
Crystallization Rate ◽  
Research Progress ◽  
Nucleating Agents ◽  
Fast Processing

AbstractPoly(lactide), PLA, as one of the most promising biopolymers, has been receiving increasing attention in recent years because of its excellent performances in renewability, mechanical properties, biocompatibility and biodegradability. However, its application is limited by its brittleness and low heat distortion temperatures (HDT). The low HDT mainly results from a low crystallization rate and lack of crystallinity after fast processing, e.g. injection molding. Consequently, considerable attention was paid, in recent years, to achieve fast(er) crystallization of PLA. In here, we briefly review the research progress in the crystallization modification of PLA notably by means of adding nucleating agents and stereocomplexation.

scholarly journals POSS Compounds as Modifiers for Rigid Polyurethane Foams (Composites)

Polymers ◽  
2019 ◽  
Vol 11 (7) ◽  
pp. 1092 ◽  
Author(s):  
Anna Strąkowska ◽  
Sylwia Członka ◽  
Krzysztof Strzelec
Keyword(s):  
Mechanical Properties ◽  
Viscoelastic Behavior ◽  
Physical And Mechanical Properties ◽  
Large Cell ◽  
Processing Parameters ◽  
Polyurethane Foams ◽  
Bending Test ◽  
Polyhedral Oligomeric Silsesquioxanes ◽  
Rigid Polyurethane Foams ◽  
Cell Shapes

Three types of polyhedral oligomeric silsesquioxanes (POSSs) with different functional active groups were used to modify rigid polyurethane foams (RPUFs). Aminopropylisobutyl-POSS (AP-POSS), trisilanoisobutyl-POSS (TS-POSS) and octa(3-hydroxy-3-methylbutyldimethylsiloxy-POSS (OH-POSS) were added in an amount of 0.5 wt.% of the polyol weight. The characteristics of fillers including the size of particles, evaluation of the dispersion of particles and their effect on the viscosity of the polyol premixes were performed. Next, the obtained foams were evaluated by their processing parameters, morphology (Scanning Electron Microscopy analysis, SEM), mechanical properties (compressive test, three-point bending test, impact strength), viscoelastic behavior (Dynamic Mechanical Analysis, DMA), thermal properties (Thermogravimetric Analysis, TGA, thermal conductivity) and application properties (contact angle, water absorption). The results showed that the morphology of modified foams is significantly affected by the fillers typology, which resulted in inhomogeneous, irregular, large cell shapes and further affected the physical and mechanical properties of the resulting materials. RPUFs modified with AP-POSS represent better mechanical properties compared to the RPUFs modified with other POSS.

An Experimental Investigation of a Micro Injection Molded Mechanical Device

2005 ◽  
Author(s):  
Alan M. Tom ◽  
Aleksandar K. Angelov ◽  
John P. Coulter
Keyword(s):  
Mechanical Properties ◽  
Experimental Investigation ◽  
Injection Molding ◽  
Processing Parameters ◽  
Primary Objective ◽  
Crystalline Materials ◽  
Reduced Modulus ◽  
Molded Parts ◽  
Secondary Objective ◽  
Injection Molded

The primary objective of this study, through a scientific experimental investigation, was to determine optimum injection molding processing parameters on semi-crystalline materials HDPE and POM focusing on mechanical properties, obtained thru the use of a nano-indenter, of micro gears being manufactured on non-heated and heated mold bases. A secondary objective was to initiate a similar experimental study using amorphous COC material. Taguchi’s method utilizing an L-9 orthogonal array was used to determine the effects of Tnoz, Tmold, Pinj, Vinj, Ppack, and tpack injection molding processing parameters. A nano-indenter was used to determine investigated mechanical properties on final injection molded parts that included stiffness (S), reduced modulus (Er), and hardness (H). Results showed HDPE, POM and COC, heated mold experiments exhibiting increases in mechanical properties S, Er, and H, on the order of 1.2–4.0 times those of non-heated molding trials. Decreases in optimum molding conditions for Tnoz, Pinj, and Ppack was also observed for heated molding trials. The highest mold temperatures and injection pressures tested did not produce greatest optimum molding conditions. However, largest packing times tested produced optimum molding conditions.

scholarly journals Effect of Femtosecond-Laser-Structured Injection Molding Tool on Mechanical Properties of the Manufactured Product

Polymers ◽  
2021 ◽  
Vol 13 (13) ◽  
pp. 2187
Author(s):  
Krisztián Kun ◽  
Zoltán Weltsch
Keyword(s):  
Mechanical Properties ◽  
Injection Molding ◽  
Femtosecond Laser ◽  
Polymer Surface ◽  
Processing Parameters ◽  
Injection Molding Process ◽  
Mold Surface ◽  
Molding Process ◽  
Melt Temperature ◽  
Polymer Product

During the injection molding process, the melt travels with a flow due to friction. As the velocity of the layers next to the wall is less than that of those flowing in the middle of the channel, a fountain flow is formed at the melt front. The temperature of the polymer surface decreases from the melt temperature to the contact temperature after contacting the mold surface. Based on all this, a complex shell–core structure is formed in injection-molded products, which can be influenced by the processing parameters and the surface of the tool insert. This paper focuses on investigating the effect of the microstructures replicated from the insert to the polymer product on its mechanical properties. During the research, two microstructured surfaces were created, with different effects on the melt flow formed by the femtosecond laser. These were compared with a ground insert to analyze the effects. For examining the effect of technological variables on the mechanical properties, an experimental design was used. The structure created by the femtosecond laser on the surface of the tool influenced the mechanical properties of the polymer products. Recognizing the effect of microstructures on the melt front and, through this, the change in mechanical properties, a predefined polymer product property can be achieved.

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