Piezoelectric properties of the hottest biodegrada

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Piezoelectric properties of biodegradable plastic PHB and its application in bone transplantation

piezoelectric properties of biodegradable plastic PHB and its application in bone transplantation Jiang Lingfei, Hu Pingqing, Department of chemical engineering, Beijing 1084, possible application in bone growth. The shear piezoelectric properties and bending piezoelectric properties of bone graft materials should be observed. 2.1 shear piezoelectric properties because in practice, it is difficult to act on the shear stress in the crystal and it is inconvenient to check the shear strain, it is often used to cut along the 45 direction of the film orientation. At this time, the sample is subjected to normal stress 0, and its piezoelectric constant can be measured in the direction. Introduction piezoelectric polymers can be divided into two categories: biopolymers, such as protein DNA, and synthetic polar polymers, such as polyvinylidene fluoride. The piezoelectricity of the latter is attributed to the coupling of residual polarization and size change. The former is due to the molecular poly (3-hydroxybutyrate) and the copolymer of 0-hydroxybutyric acid and 0-hydroxyvaleric acid, which are thermoplastic like polymers that can be obtained by microbial fermentation. It has complete biodegradability and good biocompatibility. The degradation products are 3-hydroxybutyric acid or hydroxyamyl acid, time, temperature and stress/tensile acid. Human blood can be found to contain p-hydroxybutyric acid with a concentration of 3lomg パ oomi blood. PHB and PHBV also have piezoelectric properties. Their piezoelectric mechanism is similar to that of protein, and their piezoelectric value is equivalent to that of bone. Piezoelectricity of bone!. oneself. The view of long mechanism has been popular 2 The accelerating effect of small current on bone growth has been studied in many experiments 31 Therefore, hurisi and its copolymers have received extensive attention as bone graft materials in the future. The electrical properties of 2phb and its copolymers can be used by microorganisms in 30 and, India. Under the nitrogen limiting condition of 0, fructose or acid was used as the medium for fermentation. Microorganisms grow on nutrients containing yeast, and cells then cry in the mouth on a nitrogen-free substrate containing sodium acetate and sodium propionate. It can be obtained by culturing 48 under 030. The chemical structure of Yang Cong is 4. The chemical structure of mail is obtained by biological fermentation. 1 has an isotactic structure, and each monomer has a chiral carbon atom in the configuration, so it has optical activity. The molecule is considered to have a helical conformation., X-ray fiber diffraction energy * low state analysis and cross * small multiplication analysis both believe that the Japanese crystal belongs to the orthogonal crystal system, and the two helical axes follow the direction of molecular chain extension. Because the crystal type belongs to the 222 point group of the orthogonal crystal system, yando et al. Studied the shear piezoelectric properties K5 of PHB and PHBV only in the shear stress, and found that significant piezoelectric relaxation occurred in the glass transition temperature region; Results the influence of temperature on the piezoelectric strain constant, 14=, part, substituting the imaginary part, 4. From 1, we can see that the piezoelectric strain constant 44=, 14, such as the real number part 4 in 1, changes with the change of temperature. At the glass transition temperature of 101 or so, with the increase of temperature, the content of L in phb2 and 3 in 2 of the mole fraction of PHBV 17 decrease, but the decrease of the latter is small. However, 2 in HV2 with mole fraction of phbviyiiu7 treated with e-imitation and 4 in 2 with mole fraction of 25 untreated phbviyiiu7 increased with the increase of temperature in the glass transition temperature region. Progress, why does piezoelectric relaxation occur in the region of glass transition temperature. The piezoelectric effect mainly comes from the crystallinity of polymer on the receiving date of 19989. When the external force is applied, the dipoles of molecules in the crystal region rotate, resulting in polarization; The glass transition is mainly caused by the thermal motion of molecules in the amorphous region. 36 for such a two-phase system, a spherical model is proposed, which is different from 2. Phase 1 has no piezoelectric effect; 1. It contains non oriented amorphous molecules with random conformation. Phase 2 is a region with piezoelectric effect, which includes oriented crystalline region and oriented amorphous region. Phase 2 is dispersed in phase 1. For copolymers 25, 75 and copolymers treated with chloroform 17.83 Their relaxation effect is caused by the elastic and dielectric relaxation of the factory non product area. For PHB and copolymer 17hv, lljllmv, kirjtl5 not treated with chloroform; In the amorphous region of femitfillftlxl, the piezoelectric constant is relaxed, and the sign is opposite to the sign of the piezoelectric effect produced by the crystalline region., Et al. Believed that the orientation of the amorphous region existing at the interface between the crystalline region and the amorphous region could be maintained due to the high molecular rigidity, while when the content was large, or treated with chloroform, the orientation of the amorphous region was reduced due to the reduction of the molecular rigidity. This better explains the phenomenon that the piezoelectric constant of the former decreases while that of the latter increases. It is not entirely clear why the piezoelectric constant sign of the oriented amorphous region is opposite to that of the crystalline region. Perhaps it is because the molecules in the crystalline region are dimensional ordered, while the molecules in the oriented amorphous region are dimensional ordered, and their molecular distances are randomly distributed. Due to the difference of intermolecular forces, the rotation direction of stress-induced dipole becomes opposite due to the degree of freedom of peek in its design. It is reported that for oriented cellulose acetate crystal films, the sign of piezoelectric constant will change when the temperature increases or hydration occurs in the crystal. StepI et al. Studied the reversible elastic effect of oriented crystalline Fiber Poly (2,2 methylpropanolactone) under low tension, and believed that this may be due to the reversible transition of helical conformation to planar sawtooth conformation. 17 compared with mouth analogy, 3 it is suggested that the conformation of mouth amorphous region changes to extended chain conformation under cold tension. 8.3 For, book and, diffraction test shows that there is phase., It is pointed out that it may not be transformation. Because the phase is not transformed from phase 0, but formed by (3) the amorphous area between crystal areas at No. 508, Qinzhou Road, Shanghai. Therefore, the phase is formed, not transformed, and the type conformation is not all trans, nor is it a completely straight chain. 2. Bending piezoelectric effect of PHB 33, 3 reported in 953 1. Bending piezoelectric effect of bamboo head 1 For wet bones in the body, the potential difference caused by bending effect is mainly caused by the flow of ions through the bone matrix, which is called flow potential difference. Adopt 4 small devices to measure the piezoelectric constant of Yang Qiaoqu. When the sample is bent in the direction of, the polarization intensity 1 can be p=c.s7 S+fmdt3ckl, where 15 is the shear piezoelectric constant related to the shear stress 75 in the plane of household 1 and 7, and ⑶ is the bending piezoelectric constant related to the gradient of tensile stress along the thickness direction. 030 is equal to the ratio of the elastic modulus in 2 directions to the radius of the bending part. 4. Apply a sinusoidal load with a constant frequency to 2 away from the clamped electrode, and measure the voltage generated by the two electrodes. The relationship with 2 is as follows, where 4 is the dielectric constant in the thickness direction. Are the width and thickness of the specimen respectively. The results show that the bending piezoelectric constant is anisotropic, and has a large value when the bending direction is perpendicular to the direction of molecular orientation. Its bending piezoelectric constant is about 0.51.018, while the dry bone is reported to be about 210180, and the dry tendon is about 217; Theoretical calculations of the shear piezoelectric constants of polypeptide molecules with helical conformation of about 5 degrees of orientation polarization have been reported. The bending piezoelectric constants of molecules with helical conformation should also be similarly estimated, and the history of Yang molecules is simpler than that of peptides. For this research, Yang 8 is a very suitable model material. In terms of JR electric Stocks of 3phb and PHBV composites, 1 pure mouth is formed, and the fracture recovery is small. The density may not be enough or the degradation rate cannot be controlled at will. Therefore, composite materials are generally used more. 0, 63 et al. Studied the electrical properties of the dielectric material of copolymer 93 Volume 7 and glass powder 75106 12 Glass powder plays a reinforcing role in it. Research results the electrical properties of the composite of riyuekou and glass powder are similar to those of bone. The 36 of bone, that is, the potential difference generated by strain, is about 6, while the composite material is about 3, 50. The influence of load size on 86 mouths shows a linear increasing relationship, while the composite material has a non-linear and slow relationship, and the influence of load application frequency. When square load is applied, the 36 curve has asymmetry. This is due to the unloading phase; Caused by the relaxation effect of the sample. When the frequency is increased, the relaxation effect decreases, and when the frequency reaches about 17. The generated 36 is close to the square wave., The frequency range of 1 also belongs to human physiology. The piezoelectric effect of frequency on bone is similar to this. Therefore, whether from the strength of piezoelectric effect or the response to load, the composite material and bone are comparable, and grade 0, 65 et al. Also designed a kind of glass. The composite material 31 of strong household response 93 Volume 7 and completely soluble phosphate ester has a clear dissolution rate during production, which is expected to be used to control the comprehensive degradation process of the composite material, Including mass loss and changes in mechanical properties. The piezoelectric effect of the composite was measured. The results showed that the potential difference produced by strain was similar to that of bone. Both in vivo and in vitro studies show that the behavior and solubility of composites have four applications in orthopedic transplantation. At present, there are a large class of degradable polymers that can be used in surgery. These are basically poly (1-glycolide) copolymers or blends. For scraping, a metal ruler is used to frame the first end of the top of the test mold at an approximate angle to reduce the cracks caused by fractures. The development of these materials is mainly in two Frontiers: the design of traditional fracture fixation plates, and the other is to make some simple grafts to repair the bone. When the bone tissue grows well, its own degradation occurs in the body. The degradation mechanism of kouyang and yang7 mainly includes thermal degradation, enzyme catalyzed degradation and hydrolytic degradation in vitro. In vivo, its degradation mechanism is mainly hydrolytic degradation. Q 018 et al. Found that the degradation rate of agent and its copolymer at 2.17203 was much higher than that in vitro. It is speculated that there is an enzyme in the immune system of human body. It can be catalytically degraded, but the polymer needs to be activated in advance. There are many factors affecting the degradation rate. Shape of polymer molecular weight temperature sample with degradation medium. Specific area. Crystallinity, etc. 15 There is no unified standard to compare mustard biological decline; The degradation rate of polymer, but it can be considered that the degradation rate of PHB and PHBV is slower than that of polylactide and polyglycolide. Therefore, how to adjust it by blending and other methods to adapt to the growth of cells is an important work. Yang, out of 7 with bone like piezoelectric effect. This pair of phosphate composite materials, such as fracture light base apatite, was transferred to the bone defect of animals for research. It was found that there was no adverse reaction within 12 months, and new bone 1619 grew around the material Culture human bone cells with the membrane of Yang. It is found that cells can adhere to colonization 1, Yang, Volume 7 can also be made into porous materials. To adapt to the growth of cells. Conclusion although phbphbv and composite materials have been studied abroad. But there are still some questions about running. For example, in Book 9, it is 1 oriented 1 The piezoelectric symbol of the product is opposite to the oriented crystal region, etc. And because the structure is similar to that of polypeptides, but the signal is response. Therefore, the piezoelectric research has been paid to the piezoelectric research of Xunbu biological fraction, which has a good guiding role. It is compounded with PHB and PHBV through other materials. The biodegradation process can be controlled by adjusting the ratio or selecting different materials. So as to adapt to different stages of fracture repair. These different conditions may have a definite impact on its piezoelectric properties. We can find * a suitable scheme among them, so as to have a good effect on fracture repair. It can improve the piezoelectric research of phbphbv and its composites, both in theory and in practice

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