A Study of PLA Crystallization During Solid-State Foaming

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.

Solvent Free Fabrication of Biodegradable Porous Polymers

2004 ◽  
Author(s):  
Xiaoxi Wang ◽  
Wei Li ◽  
Vipin Kumar
Keyword(s):  
Tissue Engineering ◽  
Polymer System ◽  
Solvent Free ◽  
Porous Polymers ◽  
Tissue Engineering Scaffolds ◽  
Co2 Gas ◽  
Biochemical Sensors ◽  
Foaming Process ◽  
Cell Structures ◽  
Chemical Blowing Agents

Biodegradable porous polymers with interconnected pores of sub-micrometers to a few hundred micrometers find many applications in emerging technology areas such as tissue engineering, controlled drug delivery, and biochemical sensors. However, most of the current fabrication processes involve organic solvents and chemical blowing agents that may cause environmental concerns and leave residues harmful to biological cells. This paper presents a solvent free fabrication approach for biodegradable porous polymers. Ultrasound cavitation is introduced after the solid state foaming process to produce open cell structures. The material used in this study is polylactic acid (PLA). It belongs to a family of biodegradable polymers that can be used for tissue engineering scaffolds. In order to identify suitable conditions to apply ultrasound, a saturation and foaming study is conducted for the PLA-CO2 gas polymer system. The effects of various process variables are discussed.

scholarly journals Modeling and Simulation of a Selective Laser Foaming Process for Fabrication of Microliter Tissue Engineering Scaffolds

2017 ◽  
Vol 139 (11) ◽  
Author(s):  
JinGyu Ock ◽  
Wei Li
Keyword(s):  
Tissue Engineering ◽  
Laser Power ◽  
Biomedical Applications ◽  
Processing Parameters ◽  
Tissue Engineering Scaffolds ◽  
Element Analysis ◽  
Laser Absorption ◽  
Fea Model ◽  
Foaming Process ◽  
And Control

Selective laser foaming is a novel process that combines solid-state foaming and laser ablation to fabricate an array of microliter tissue engineering scaffolds on a polymeric chip for biomedical applications. In this study, a finite element analysis (FEA) model is developed to investigate the effect of laser processing parameters. Experimental results with biodegradable polylactic acid (PLA) were used for validation. It is found that foaming always occurs before ablation, and once it occurs, the temperature increases dramatically due to an enhanced laser absorption effect of the porous structure. The geometry of the fabricated scaffolds can be controlled by laser parameters. While the depth of scaffolds can be controlled by laser power and lasing time, the diameter is more effectively controlled by the laser power. The model developed in this study can be used to optimize and control the selective foaming process.

Fabrication of Hydroxyapatite Ceramics with Interconnected Macro Porosity

2005 ◽  
Vol 284-286 ◽  
pp. 277-280 ◽  
Author(s):  
Lenka Müller ◽  
Frank A. Müller ◽  
Jürgen Zeschky ◽  
Tobias Fey ◽  
Peter Greil
Keyword(s):  
Tissue Engineering ◽  
Calcium Phosphate ◽  
Pore Structure ◽  
Cellular Structure ◽  
Orthopedic Implants ◽  
Tissue Engineering Scaffolds ◽  
Porous Bodies ◽  
Hydroxyapatite Ceramics ◽  
Foaming Temperature ◽  
Methyl Phenyl

Calcium phosphate bioceramics with an interconnective pore structure were produced by foaming of hydroxyapatite and methyl phenyl poly(silsequioxane) melts in the temperature range between 250 °C and 310 °C. The cellular structure of the resulting porous bodies were controlled by foaming parameters and filler load. A porosity of up to 92 % was achieved by decreasing the HAfiller amount and increasing the foaming temperature. Subsequent pyrolysis in air at temperatures of 900 °C and 1100 °C resulted in macroporous foams composed of HA and HA/b-TCP, respectively. The porous bodies with tailorable structure and composition are of interest for bone tissue engineering scaffolds and orthopedic implants.

Solid-State Foaming of Polycaprolactone (PCL)

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.

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

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.

scholarly journals The mechanics of solid-state nanofoaming

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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