Preparation of Porous Materials by Magnesium Phosphate Cement with High Permeability

Abstract

High permeability and strength magnesium phosphate cement (MPC) with porosity, average pore size, and compressive strength varied from 63.2% to 74%, 138.7 μm to 284.7 μm and 2.3 MPa to 4.7 MPa, respectively, were successfully prepared by combining the physical foaming method and chemically entrained gas method at room temperature. The effects of borax content, chemical foaming agent content, zinc powder content and W/S ratio on the porosity, pore size distribution, compressive strength, and permeability of the MPC were investigated. The results indicate that the chemical foaming agent content tends to have little impact on the porosity and compressive strength, and the zinc powder content has the most significant influence on the average pore size of MPC. The air pores distribution and connectivity of MPC were mainly controlled by the borax content, W/S ratio, and chemical foaming agent content. Zinc powder played a destructive role in the pores formed by the early physical foaming and led to an increase in pore size and a large number of through pores, which increased the permeability of the materials.

An Overview of Magnesium-Phosphate-Based Cements as Bone Repair Materials

“…To achieve this, macropores must be induced on purpose in the MPC matrix. In the literature, few attempts have been described for the preparation of macroporous MPCs: zinc powder [ 59 ], also in combination with a chemical foaming agent [ 73 ]; sodium bicarbonate [ 104 ]; and protein-based foaming agents [ 103 ] have been used, even though none of these materials were designed for application in the biomedical field. Macroporous MPCs for orthopedic applications have been obtained using biodegradable Mg particles as porogens during cement setting [ 69 ], polyurethane foams [ 143 ], and gelatin microparticles [ 158 ].…”

“…For this purpose, the role of additives that could prolong the setting time and in turn increase the workability and moldability of cements has been investigated in the literature. The data summarized in Table 2 show that by far the most widely investigated retarder for MPCs is borax (Na 2 B 4 O 7 ·10H 2 O)/boric acid (H 3 BO 3 ), in both the biomedical [ 57 , 58 , 63 , 77 , 126 , 135 ] and (particularly) construction fields [ 59 , 62 , 64 , 65 , 66 , 67 , 68 , 70 , 71 , 72 , 73 , 74 , 75 , 76 , 77 , 80 , 82 , 83 , 84 , 85 , 86 , 87 , 89 , 90 , 91 , 92 , 101 , 102 , 104 , 107 , 112 , 113 , 116 , 119 , 120 , 124 , 128 , 129 , 130 , 131 , 136 ]. Borax was in fact traditionally used to delay the setting time of MgO-based MPCs, and its setting mechanism has been well investigated in the literature, from both an experimental and a theoretical perspective [ ...…”

“…Some organic acids have also been reported as retarders for MPCs, in particular, acetic [ 62 , 64 , 67 ] and citric acid [ 73 , 111 , 117 , 188 ]. Besides the increment in the setting time, the inclusion of citric acid has also been reported to positively impact the compressive strength of cements [ 188 ].…”

“…For this purpose, the role of additives that could prolong the setting time and in turn increase the workability and moldability of cements has been investigated in the literature. The data summarized in Table 2 show that by far the most widely investigated retarder for MPCs is borax (Na 2 B 4 O 7 •10H 2 O)/boric acid (H 3 BO 3 ), in both the biomedical [57,58,63,77,126,135] and (particularly) construction fields [59,62,[64][65][66][67][68][70][71][72][73][74][75][76][77]80,[82][83][84][85][86][87][89][90][91][92]101,102,104,107,112,113,116,119,120,124,[128][129][130][131]…”

Alendronate-loaded gelatin microparticles as templating agents for macroporous magnesium phosphate-based bone cements

“…Macroporous MPCs have been investigated to a lesser extent: the first reports include foaming with zinc powder [25], also combined with a chemical foaming agent [26], sodium bicarbonate [27] or protein-based foaming agents [28], even if none of these materials was designed for biomedical applications. In the orthopedic field, macroporous MPCs were obtained using biodegradable Mg particles as porogens during cement setting [29] or polyurethane foams [30].…”