Development of Crystallization in PLA during Solid-State Foaming Process using Sub-Critical CO2

This paper presents the foaming behavior of PLA-CO2 and PLA/beeswax-CO2 systems for solid state foaming process with particular goal of producing low density foams. The low density PLA foams can be achieved under 2 MPa sub-critical CO2 condition due to CO2-induced crystalline. When 10wt% beeswax was added to PLA matrix, the tensile strain at break increases from 7.9% to 22.2% and crystallinity remain unchanged. The inherent brittle deformation behavior of the PLA was transformed into relatively ductile behavior after blending 10wt% beeswax. The expansion ratio of neat PLA and its blends with 10wt% beeswax increase from 1.08 to 19.4. The ductile deformation behavior of PLA is an important factor for solid-state PLA foam.

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Solid-State Foaming of Polycaprolactone (PCL)

Volume 3: Design and Manufacturing ◽

10.1115/imece2007-42666 ◽

2007 ◽

Author(s):

Hai Wang ◽

Wei Li ◽

Vipin Kumar

Keyword(s):

Electron Microscopy ◽

Scanning Electron Microscopy ◽

Solid State ◽

Room Temperature ◽

Saturation Pressure ◽

Crystalline Polymer ◽

Foaming Process ◽

Quenching Process ◽

Foaming Temperature ◽

Scanning Electron

Polycaprolacton (PCL) is a synthetic biodegradable polymer that is widely used in tissue engineering related studies. It is a semi-crystalline polymer, and has a glass transition temperature (Tg) of −60°C and a melting temperature of 60°C. In this paper, we report on the progress in creating porous PCL foams using the solid-state foaming process. The objective of this study is to examine the foam-ability of PCL using room temperature saturation. PCL specimens were made using compression molding. A “quenching” process was introduced to manipulate the crystallinity of PCL samples. CO2 was used for gas saturation. The effects of saturation pressure and foaming temperature were studied. The created microstructures were characterized using scanning electron microscopy (SEM). The preliminary results have shown that microstructures with pores on the scale of hundreds of nanometers were generated.

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Solid-State Foaming Process Optimization for the Production of Shape Memory Polymer Composite Foam

Applied Sciences ◽

10.3390/app11083433 ◽

2021 ◽

Vol 11 (8) ◽

pp. 3433

Author(s):

Tamem Salah ◽

Aiman Ziout

Keyword(s):

Solid State ◽

Shape Memory Polymer ◽

Sustainable Manufacturing ◽

Holding Time ◽

X Ray Diffraction ◽

Scanning Calorimetry ◽

Foaming Process ◽

Optimum Parameters ◽

Packing Pressure ◽

Foaming Temperature

This research examined the optimization of the sustainable manufacturing process for polyester-based polymers/Fe3O4 nanocomposite foaming. The foamed structure was achieved by using a solid-state foaming process, where the prepared foams were tested in order to ascertain the optimum foaming parameters with the highest foaming ratios and the lowest foaming densities. The foaming parameters used in this research were the polymer type, nanoparticle percentage, packing pressure, holding time, foaming temperature, and foaming time. Two levels were selected for each factor, and a Taguchi plan was designed to determine the number of experiments required to reach a conclusion. Further characterization techniques, namely, differential scanning calorimetry (DSC), Fourier transform infrared spectroscopy (FTIR), and X-ray diffraction (XRD) were used with the original samples to gain a better understanding of their structure and chemical composition. The data analysis showed that regardless of the parameters used, a high foaming ratio resulted in a low density. The introduction of nanoparticles (NPs) to the polymer structure resulted in higher foaming ratios. This increment in foaming ratio was noticeable on Corro-Coat PE Series 7® (CC) polymer more than Jotun Super Durable 2903® (JSD). The optimum parameters to prepare the highest foaming ratios were as follows: CC polymer with 2% NPs, compressed under a pressure of 10 K lbs. for a 3 min holding time and foamed at 290 °C for 15 min in the oven.

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Optimization of Actuation Load and Shape Recovery Speed of Polyester-Based/Fe3O4 Composite Foams

Materials ◽

10.3390/ma14051264 ◽

2021 ◽

Vol 14 (5) ◽

pp. 1264

Author(s):

Tamem Salah ◽

Aiman Ziout

Keyword(s):

Solid State ◽

Polymer Matrix ◽

Shape Recovery ◽

Experimental Results ◽

Foaming Process ◽

Nanocomposite Foams ◽

Composite Foams

In this research, polyester-based polymers/Fe3O4 nanocomposite foams were prepared in order to study their performance; namely shape recovery speed and actuation load. A foamed structure was obtained through a solid-state foaming process, which was studied and optimized in previous research. The optimum foaming parameters were applied in an attempt to achieve the highest foaming ratio possible. A Taguchi Map was then designed to determine the number of experiments to be conducted. The experimental results showed that the maximum actuation load obtained was 3.35 N, while optimal (fastest) recovery speed was 6.36 mm/min. Furthermore, temperature had no impact on the actuation load as long as a temperature above the Tg was applied. Moreover, the addition of nanoparticles reduced shape recovery speed due to discontinuity within the polymer matrix.

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Preliminary Study on Solid-State Foaming of PMMA/CNT Nanocomposites

Volume 13: Processing and Engineering Applications of Novel Materials ◽

10.1115/imece2007-42742 ◽

2007 ◽

Author(s):

Xiaoxi Wang ◽

Wei Li ◽

Vipin Kumar ◽

Soumen Jana ◽

Katie W. H. Zhong

Keyword(s):

Solid State ◽

Relative Density ◽

Polymer Nanocomposites ◽

Bubble Nucleation ◽

Pure Pmma ◽

Microcellular Foams ◽

Foaming Process ◽

Significant Difference ◽

Carbon Nano Tubes ◽

Preliminary Study

Polymer nanocomposites with carbon nano tubes (CNTs) added in the polymer matrices have been shown to have improved material properties comparing to their neat forms. Foaming of polymer nanocomposites is even more interesting because these foams promise higher strength-to-weigh ratio and multifunctionality. However, many foaming results on polymer nanocomposites are inconclusive, for example, the effect of nano-additives on the bubble nucleation. In this study, solid-state foaming of pure PMMA and PMMA/CNT composite were performed. CNTs were dispersed in PMMA solution with ultrasonication. Microcellular foams were achieved in both cases. The resulted relative density and microstructures were investigated. It was found that nano carbon tubes aggregated on the cell walls of the microcellular foams. In terms of the cell size and relative density, there is no significant difference between pure PMMA and PMMA/CNT foams. Better dispersion of CNTs is needed in order to further study the CNT effect on the solid-state foaming process.

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Constrained Solid-State Foaming of Microcellular Panels

Cellular Polymers ◽

10.1177/026248930502400202 ◽

2005 ◽

Vol 24 (2) ◽

pp. 71-90 ◽

Cited By ~ 13

Author(s):

Krishna Nadella ◽

Vipin Kumar ◽

Wei Li

Keyword(s):

Solid State ◽

Systematic Study ◽

Design Of Experiment ◽

Sandwich Structures ◽

Housing Construction ◽

Process Variables ◽

Two Stage ◽

Load Bearing ◽

Foaming Process ◽

Constrained Foaming

This paper presents a novel constrained foaming process to produce microcellular panels. A systematic study of various process variables is conducted using a two-stage, sliding-level design of experiment approach. The resulting microcellular sheets have thicknesses in the 5 – 15 mm range and densities reductions as low as 92%. It is shown that an unfoamed integral skin of desired thickness can be produced with a microcellular core at various densities. These microcellular panels are envisioned for use in advanced panel systems and sandwich structures, such as in housing construction and other load-bearing applications.

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The mechanics of solid-state nanofoaming

Proceedings of The Royal Society A Mathematical Physical and Engineering Sciences ◽

10.1098/rspa.2019.0339 ◽

2019 ◽

Vol 475 (2230) ◽

pp. 20190339

Author(s):

Frederik Van Loock ◽

Victoria Bernardo ◽

Miguel Angel Rodríguez Pérez ◽

Norman A. Fleck

Keyword(s):

Cell Wall ◽

Solid State ◽

Cell Walls ◽

Uniaxial Stress ◽

Nucleation Density ◽

One Dimensional ◽

Foaming Process ◽

Cell Nucleation ◽

Foaming Temperature ◽

Versus Strain

Solid-state nanofoaming experiments are conducted on two polymethyl methacrylate (PMMA) grades of markedly different molecular weight using CO 2 as the blowing agent. The sensitivity of porosity to foaming time and foaming temperature is measured. Also, the microstructure of the PMMA nanofoams is characterized in terms of cell size and cell nucleation density. A one-dimensional numerical model is developed to predict the growth of spherical, gas-filled voids during the solid-state foaming process. Diffusion of CO 2 within the PMMA matrix is sufficiently rapid for the concentration of CO 2 to remain almost uniform spatially. The foaming model makes use of experimentally calibrated constitutive laws for the uniaxial stress versus strain response of the PMMA grades as a function of strain rate and temperature, and the effect of dissolved CO 2 is accounted for by a shift in the glass transition temperature of the PMMA. The maximum achievable porosity is interpreted in terms of cell wall tearing and comparisons are made between the predictions of the model and nanofoaming measurements; it is deduced that the failure strain of the cell walls is sensitive to cell wall thickness.

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Influence of Thermoplastic PEG, GLY and Zein in PCL/TZ and HAp Bio Composite via Solid State Supercritical CO2 Foaming

Scientific Research Journal ◽

10.24191/srj.v17i2.9534 ◽

2020 ◽

Vol 17 (2) ◽

pp. 177

Author(s):

Istikamah Subuki ◽

Suffiyana Akhbar ◽

Farrah Khalidah Nor Wahid

Keyword(s):

Electron Microscopy ◽

Carbon Dioxide ◽

Solid State ◽

Porous Structure ◽

Supercritical Co2 ◽

Saturation Pressure ◽

Thermal Characterization ◽

Foaming Process ◽

Scanning Electron

This study is aimed to investigate the characteristics of the composite containing blended poly (ɛ-caprolactone) (PCL), hydroxyapatite (HA) and thermoplastic zein (TZ). Thermoplastic zein was developed by mixing zein with glycerol (GLY) and polyethylene glycol (PEG). The thermal characterization of mixed TZ and bio composite was characterized in order to investigate the characterization of PCL/TZ/HA composites. The bio composited was then moulded and produce porous structure via solid state supercritical carbon dioxide (scCO2) foaming process. The specimen was saturated with CO2 for 6 hours at 50˚C and saturation pressure of 20MPa at high depressurization rate. The morphology of porous specimen produced were characterized by scanning electron microscopy (SEM). The results indicated that after polymer saturation with CO2, high depressurization causes the formation of nucleated gas cells that give rise to pores within the foamed specimens. The blended bio composite with composition of PCL60/TZ20/HAp20 exhibit well interconnected porous structure compared to other bio composite prepared. The foaming effect produce foams with heterogeneous morphologies on bio composite material at relatively low temperature.

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A Study of PLA Crystallization During Solid-State Foaming

Volume 3: Design and Manufacturing ◽

10.1115/imece2007-42547 ◽

2007 ◽

Author(s):

Xiaoxi Wang ◽

Vipin Kumar ◽

Wei Li

Keyword(s):

Tissue Engineering ◽

Solid State ◽

Thermoplastic Polymer ◽

Gas Sorption ◽

Tissue Engineering Scaffolds ◽

Foaming Process ◽

Saturation Stage ◽

Main Factors ◽

Foaming Temperature ◽

Process Ability

Polylactic acid (PLA) is a biodegradable semi-crystalline thermoplastic polymer that can be used in many applications such as tissue engineering scaffolds and packaging. The crystallinity of PLA is an important factor that affects its process-ability, mechanical strength, and biodegradability. The solid-state foaming of semi-crystalline PLA has been a subject of recent investigations. In this paper, crystallization through out the solid state foaming process was studied. It was found that the crystallization reaches the equilibrium once the gas sorption reaches the equilibrium. There are two main factors that will affect the PLA crystallization: gas sorption during the saturation stage and the heating and stretching during the foaming stage. Within the range of 2 to 5 MPa saturation pressures and 60 to 100 °C foaming temperatures, a maximum crystallinity of approx. 25% was observed in the foamed PLA. Effects of stretching and foaming temperature on crystallinity of foamed specimens were also investigated.

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