Microcellular Polycarbonate with Improved Notched Impact Strength Produced by Injection Moulding with Physical Blowing Agent

2008 ◽  
Vol 27 (6) ◽  
pp. 327-345 ◽  
Author(s):  
A.K. Bledzki ◽  
M. Rohleder ◽  
H. Kirschling ◽  
A. Chate
Keyword(s):  
Impact Strength ◽  
Injection Moulding ◽  
Microcellular Foam ◽  
Processing Technologies ◽  
Compact Material ◽  
Blowing Agent ◽  
Microcellular Foams ◽  
Test Parameters ◽  
Injection Moulding Process ◽  
The Impact

Polycarbonate has the reputation of having a tough breaking behaviour, but it is often unknown that this applies only to special conditions. The impact strength of polycarbonate depends on the temperature, the thickness (with a tough brittle transition at thickness increases), contribution of notch tip radius, impact speed, physical blowing agent, molecular weight of the polymer and the processing parameters. Research results indicated that microcellular foams produced by injection moulding with physical blowing agent (MuCell™ Technology by Trexel) shows significant higher notched impact strength than compact polycarbonate, if the compact material is brittle under the same test parameters. However, if the compact polycarbonate breaks toughly, the notched impact strength of the foamed material is always lower. Therefore, it is highly important to pay attention to the test parameters and conditions when comparing the toughness of the foamed with the compact material. The toughness of microcellular foams shows similar properties to PC/ABS and PC/PP blend systems, which provides the possibility to combine the higher impact strength with the advantages of microcellular foaming like weight reduction, lower shrinkage, shorter cycle times, lower clamp forces and reduced melt viscosity. In order to use technologies and conditions which are applied in the polymer industry, all materials were produced by an injection moulding process. Special processing technologies like gas counter pressure and precision mould opening were used in order to reach microcellular foam structures with cell diameters around 10 μm. These technologies yield exactly adjustable foam morphologies. Special morphologies are required to improve the notched impact strength of the foamed material. Two different equivalent models were extracted from the analyses, which indicate significant higher notched impact strength than the compact material under the same test conditions. The knowledge of the ideal foam morphologies enables the industry to produce foamed materials with improved mechanical properties.

scholarly journals Design of an Experimental Injection Moulding Tool for Testing Microstructured Cavity Surfaces

2021 ◽  
Vol 4 (2) ◽  
pp. 97-102
Author(s):  
Krisztián Kun
Keyword(s):  
Injection Moulding ◽  
Uniform Structure ◽  
Cavity Surface ◽  
Moulding Process ◽  
Injection Moulding Process ◽  
Tool Surface ◽  
Degree Of Orientation ◽  
High Degree ◽  
The Impact

Abstract This research is based on the impact assessment of the active element of injection moulding tools. The quality of the tool surface has a significant effect on the filling and cooling efficiency. Our goal is to create a uniform structure on the cavity’s surface that results in a high degree of orientation during the injection moulding process. A special experimental tool is needed for the research. Our design was based on the results of previous experimental research and preliminary criteria. The design was based on the size and position tolerances of the A side of the tool. As the previous study has shown, there are three main points to consider when designing an experimental moulding tool. These are the applied manufacturing technology, Design for Assembly, and the expansion of the measurement possibilities by using different sensors. The small beam size of the femtosecond laser also allows the machining of microscopic-sized details, a technology used to structure the cavity surface. The success of this was analyzed by microscopic examination.

scholarly journals A Novel Hybrid Foaming Method for Low-Pressure Microcellular Foam Production of Unfilled and Talc-Filled Copolymer Polypropylenes

Polymers ◽  
2019 ◽  
Vol 11 (11) ◽  
pp. 1896 ◽  
Author(s):  
Llewelyn ◽  
Rees ◽  
Griffiths ◽  
Jacobi
Keyword(s):  
Injection Molding ◽  
Mechanical Characteristics ◽  
Low Pressure ◽  
Microcellular Foam ◽  
Foaming Agents ◽  
Blowing Agent ◽  
Weight Saving ◽  
Microcellular Foams ◽  
Foam Injection Molding ◽  
Foam Production

Unfilled and talc-filled Copolymer Polypropylene (PP) samples were produced through low-pressure foam-injection molding (FIM). The foaming stage of the process has been facilitated through a chemical blowing agent (C6H7NaO7 and CaCO3 mixture), a physical blowing agent (supercritical N2) and a novel hybrid foaming (combination of said chemical and physical foaming agents). Three weight-saving levels were produced with the varying foaming methods and compared to conventional injection molding. The unfilled PP foams produced through chemical blowing agent exhibited the strongest mechanical characteristics due to larger skin wall thicknesses, while the weakest were that of the talc-filled PP through the hybrid foaming technique. However, the hybrid foaming produced superior microcellular foams for both PPs due to calcium carbonate (CaCO3) enhancing the nucleation phase.

scholarly journals Tensile and impact strength of alpaca fiber epoxy matrix hybrid composites prepared by injection moulding process

2021 ◽  
Vol 2027 (1) ◽  
pp. 012011
Author(s):  
N. Vinoth ◽  
K. Rajkumar ◽  
R. Santhosh Kumar ◽  
V Mohanavel ◽  
M. Ravichandran ◽  
...  
Keyword(s):  
Impact Strength ◽  
Injection Moulding ◽  
Epoxy Matrix ◽  
Hybrid Composites ◽  
Moulding Process ◽  
Injection Moulding Process

Effects of Process Parameters on the Properties of Replicated Polymeric Parts

2012 ◽  
Author(s):  
Gianluca Trotta ◽  
Vincenzo Bellantone ◽  
Rossella Surace ◽  
Irene Fassi
Keyword(s):  
Process Parameters ◽  
Injection Moulding ◽  
Low Cost ◽  
Injection Velocity ◽  
Processing Technologies ◽  
Moulding Process ◽  
Micro Injection Moulding ◽  
Technical Requirements ◽  
Dog Bone ◽  
Injection Moulding Process

The increasing demand for small and even micro scale parts is boosting the development of reliable micro system technologies. Micro-fabrication process capabilities should expand to encompass a wider range of materials and geometric forms, by defining processes and related process chains that can satisfy the specific functional and technical requirements of new emerging multi-material products, and ensure the compatibility of materials and processing technologies throughout these manufacturing chains. Micro injection moulding is the process of transferring the micron or even submicron precision of microstructured metallic moulds to a polymeric products. It represents one of the key technologies for micro manufacturing because its mass production capability and relatively low production cost. Polymers have relatively low cost, and offer good mechanical and thermal strength, electrical insulation, optical transparency, chemical stability and biocompatibility. In this work the authors investigate the micro injection moulding process parameters on the overall quality of a miniaturized dog-bone shaped specimen. The aim of the experimentation is to calibrate the process and set the machine for the correct filling of the component. A set of injection parameters are selected for study by experimental plan and simulation tool and then discussed. Simulation results are used to better understand the polymer flow behaviour during the filling phase. A commercial software is used and input data, collected during the micro injection moulding process, are included using as performance indicators flow front position and moulded mass. Process simulation can provide, at the present time, mostly qualitative input to the designer and process engineer. Two different polymers materials are tested and evaluated in relation to the process replication capability: Polyoxymethylene (POM) and Liquid Cristal Polymer (LCP). Finally, the moulding factors with significant statistical effects are identified. The holding pressure and holding time for POM and the holding pressure and injection velocity for LCP show the highest influence on achieving high part mass.

Production of components through microcellular processing

2021 ◽  
Author(s):  
◽  
Gethin John Llewelyn
Keyword(s):  
Surface Roughness ◽  
Injection Moulding ◽  
Mechanical Performance ◽  
Processing Parameters ◽  
Experimental Results ◽  
Simulation Accuracy ◽  
Foaming Agents ◽  
Blowing Agents ◽  
Blowing Agent ◽  
Microcellular Foams

The manufacture of light weight plastic components is gaining relevance within the polymer industry as component weight savings of up to 15% can be achieved. Foam Injection Moulding (FIM) is one technology solution that delivers weight saving through the introduction of microcellular structures within components. FIM differs from conventional injection moulding whereby blowing agents are added to the polymer during processing to create a cellular structure. The first part of this research aims to benchmark Unfilled and Talc-filled Copolymer Polypropylene (PP) samples through low-pressure FIM. The research analyses the process response when utilising a chemical blowing agent, a physical blowing agent and a novel hybrid foaming (combination of said chemical and physical foaming agents). The experimental results concluded that Unfilled PP foams produced through chemical blowing agent exhibited superior mechanical characteristics due to larger skin wall thicknesses. However, the hybrid foaming produced superior microcellular foams for both PP variations due to calcium carbonate (CaCO3) enhancing the nucleation phase. The next section of research initially varied then subsequently optimised the main processing parameters to determine their effect on Surface Roughness, Young’s Modulus and Tensile Strength. The experimental results show that the mechanical performance can be improved when processing with higher Mould Temperatures and longer Holding Times. Also, when utilising the CBA, surface roughness is comparable to conventionally processed components. The final stage of the research investigated the ability of an industry standard simulation package to accurately predict the process response when processing with a variety of blowing agents. Initial simulations results failed to accurately replicate physical mouldings which can be attributed to microcellular structure overestimations within the simulation. Through an iterative process, simulation settings have been identified that provide clear correlations to improve the simulation accuracy of FIM.

Influence of Mould Temperature on the Thickness of a Skin Layer and Impact Strength in the Microcellular Injection Moulding Process

2005 ◽  
Vol 24 (5) ◽  
pp. 279-297 ◽  
Author(s):  
Jung Joo Lee ◽  
Sung Woon Cha
Keyword(s):  
Impact Strength ◽  
Layer Thickness ◽  
Injection Moulding ◽  
Amorphous Materials ◽  
Crystalline Polymer ◽  
Processing Parameters ◽  
Skin Layer ◽  
Mould Temperature ◽  
Moulding Process ◽  
Injection Moulding Process

The thickness of a skin layer on the parts made by a microcellular injection moulding process may influence its properties, including impact and tensile strength, density and sound transmission. Therefore it is necessary to study the variations in skin layer thickness with processing parameters. In this paper, the influences of temperatures in the mould cavity on the skin layer's thickness are addressed. In addition, the relationship between the temperature distributions across the cavity of the mould, with impact strength on parts made using a microcellular injection moulding process, was addressed. *TSL, the temperature at which the skin layer forms, was proposed. According to previous studies, TSL is expected to be similar to the polymer melting point for semi-crystalline polymer and the glass transition temperature for amorphous materials. In addition, a method to predict variations in skin layer thickness with mould temperature is discussed.

Расчетные методы оценки ударной вязкости сварных элементов с трещинами

2020 ◽  
Vol 44 (3) ◽  
pp. 22-36
Author(s):  
Keyword(s):  
Stress Intensity ◽  
Impact Strength ◽  
Welded Joints ◽  
Development Process ◽  
Welded Joint ◽  
Operating Temperature ◽  
Crack Development ◽  
Heterogeneous Structure ◽  
Critical Crack Length ◽  
The Impact

Практика показывает, что для сварных конструкций, эксплуатируемых в условиях Крайнего Севера необходимо уделять внимание работоспособности сварных соединений при низких температурах. Металл сварных соединений в процессе воздействия обработки изменяет свои свойства, снижается ударная вязкость, образуется гетерогенная структура с большой степенью разнозернистости. Чтобы оценивать и иметь возможность правильно контролировать термическое воздействие и последствия сварочного процесса, требуется решить задачу аналитического определения ударной вязкости для всех зон сварного соединения. В настоящей статье представлен инженерный метод оценки ударной вязкости, применимый для любой зоны сварного соединения, в которой имеется острый или особый концентратор напряжений – трещина. Разработанный аналитический метод расчета ударной вязкости отражает качественную и количественную картину взаимосвязи структурно-механических характеристик и работы развития трещины в диапазоне температур 77…300 К. Предложенная схематизация зависимости критического коэффициента интенсивности напряжений от температуры позволила найти коэффициенты, характеризующие свойства материала, и выполнить расчеты изменения предела текучести и предела прочности от температуры эксплуатации. Построены графики зависимости работы развития трещины от температуры эксплуатации для сталей 15ГС и 17ГС, сравнение которых с экспериментальными данными показывает удовлетворительное согласование. Найдено, что при напряжениях предела выносливости отношение работы развития трещины к критической длине трещины постоянно, не зависит от температуры и для сталей 15ГС и 17ГС равно около 10. Ключевые слова: ударная вязкость, работа разрушения, коэффициент интенсивности напряжений, трещина, феррито-перлитная сталь, зона термического влияния. For welded structures under operation in the Far North, attention must be paid to the performance of welded joints at low temperatures. The properties of metal of welded joints are changed in the process of treatment, its toughness decreases, and a heterogeneous structure with a large range of different grain sizes is formed. In order to evaluate and be able to correctly control the thermal effect and the consequences of the welding process, it is necessary to solve the problem of analytical determination of impact strength for all zones of the welded joint. The paper presents an engineering method for evaluation of the impact strength applicable to any area of the welded joint in which there is a sharp or super sharp stress concentrator – a crack. The developed analytical method for calculating the impact strength reflects a qualitative and quantitative codependency of structural and mechanical characteristics and the process of crack development in the temperature range of 77–300 K. The proposed schematization of dependence of the critical coefficient of stress intensity on the temperature made it possible to find coefficients characterizing the properties of the material and to perform calculations of changes in yield strength and tensile strength on operating temperature. Graphs of the crack development process dependency on the operating temperature for 15ГС and 17ГС steels were constructed, and their comparison with experimental data displays satisfactory agreement. It was found that at endurance limit stresses, the ratio of the crack development process to the critical crack length is constant, non-dependent on temperature, and is equal to 10 for 15ГС and 17ГС steels. Keywords: impact strength, fracture work, stress intensity factor, crack, ferrite-pearlite steel, heat affected zone, steel tempering.

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