Gas foaming technique

Figure 3.3 (a) Porous P-TCP scaffold fabricated by spark-plasma sintering of nanocrystaUine powder and using 350-650 pm polyethylene glycol particles as porogens (adapted with permission from Ref. [38]) (b) a porous HA scaffold prepared by gas-foaming technique ... 

Using effervescent materials, the pore size of the pol5mier scaffolds can be easily controlled, and biodegradable polymer scaffolds can be more simply prepared compared to conventional methods such as salt leaching technique, phase separation technique, or gas foaming technique. 

Ji, C.D., Annabi, N., Hosseinkhani, M., Sivaloganathan, S., Dehghani, R, 2012. Fabrication of poly-(DL)-lactide/polyethylene glycol scaffolds using the gas foaming technique. Acta Biomaterialia 8, 570-578. 

Fig. 5. SEM image of morphology of pure PLDL (PAM) scaffold obtained using combination of salt leaching and gas foaming techniques...

To prepare nanocomposite scaffolds based on bioresorbable polymers (PLDL), two different methods were used salt leaching and a combination of salt leaching and gas foaming techniques. The obtained scaffolds were characterized by good mechanical properties and high porosity, required for materials for bone tissue regeneration. Additionally, high water absorption for these scaffolds, especially for nanocomposite scaffolds, may indicate the presence of interconnected... 

HA hydrogel after 7 days. (B) Mineralization in SBF for PEGMC/HA composite with 40 wt.% HA at 7 days. (C) 10 pm section of PEGMC scaffold showing the porosity created from a gas foaming technique. 

Air and gas, unstable foam and stable foam techniques are used almost exclusively for onshore drilling operations, rarely in offshore applications. Aerated mud, however, is used for both onshore and offshore drilling operations. 

During the polymerization reaction to form a solid polymer the isocyanate also reacts to liberate a gas which forms the cells. This is the basis of some polyur-ethane foam techniques. 

Injection compression molding (ICM) is, similarly to the gas injection technique and thermoplastic foam injection (TFI), particularly well-suited to making thick-walled moldings with little warping and few sink marks. However, thin-walled parts with long flow paths can also be produced efficiently by means of ICM. 

Suitable processing techniques for the formed hydrogels or solid biomaterials include gas foaming, stereolithography, photopatterning, and inkjet printing. 

Heparin-conjugated PLGA scaffolds have been fabricated though techniques such as gas-foaming/salt-leaching and have been used to sustain drug delivery of growth factors like BMP-2 to enhance bone formation [92,93]. 

Omega seals, thin flexible carbon or stainless steel strips,were welded over the horizontal joints between the tie straps to form a gas seal. The carbon steel omega seals at the three old reactors have rusted and permit gas leakage. A foaming technique is being tried to stop the gas leaks. 

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