Study On Manufacture And Properties Of Polyvinylidene Fluoride (PVDF) Hernia Mesh

Biomedical textile is a combination of textile technology and medical science. It is one of the most creative research areas in textile engineering. Hernia mesh belongs to the surgical implantation textile. It is an essential part of tension-free herniorrhaphy. The properties of hernia mesh have great effects on the performance of postoperative rehabilitation. Hernia has great harm to the human body. It doesn’t have a self-healing capability. Without herniorrhaphy, it will affect the daily life or even cause death. Each year about5million people are diagnosed with hernia. Hernia is not only a kind of geriatrics, the risks of hernia disease for children and adults increase year by year. Therefore, the development and study on hernia mesh have a very broad prospect of application and social and economic benefits.Polyvinylidene fluoride (PVDF) is a relatively new hernia repair material, which has stable physical and chemical properties. The researches of PVDF mesh in hernia repair have demonstrated that it has satisfactory biocompatibility and biostability. But the research on the preparation and mechanical properties of PVDF mesh is relatively scarce. In this paper, the mechanical properties of PVDF monofilament and PVDF mesh, and the heat setting parameters of PVDF mesh are investigated. Patterned electrospun anti-adhesive membrane and a novel polycaprolactone (PCL)/PVDF composite hernia mesh are developed. The main research contents can be summarized as follows:(1) Study on the mechanical properties of PVDF monofilament and meshThis paper studies the mechanical properties of PVDF monofilament and hernia mesh, including tensile testing, creep testing, elastic recovery testing, fatigue deformation testing, tear resistance testing and suture retention testing. The results are compared with the commonly used material PP monofilament, PP mesh and the needs of human body. The results exhibit that PVDF monofilament has less creep deformation, higher elasticity and smaller fatigue deformation. PVDF monofilament has good flexibility and stability to avoid shape deformation or fracture during and after operation. In addition, both PVDF mesh and PP mesh can meet the demand of the human body in tear resistance testing, ball burst testing and suture retention testing. PVDF mesh shows less creep deformation and higher elastic recovery percentage. The flexibility and the long-term stability of PVDF mesh are better than PP mesh. There are significant differences between wale and course direction of mesh. Wale direction tends to have larger strength and smaller elasticity.(2) Study on creep models of PVDF monofilament and meshThis paper studies the creep behaviors of monofilament and mesh theoretically. Three creep models (four-element model, modified generalized Maxwell model, Eyring’s model) are used to fit the creep experimental data of monofilament and mesh. Through comparison, the suitable creep model is obtained. The calculated creep equation is used to predict the long-term creep properties of PVDF mesh. The results show that the modified generalized Maxwell model is more suitable to describe the creep curves of hernia meshes. Better agreements between theoretical and measured creep curves are observed. This paper compares the calculated theoretical creep deformation and the experimental data when the creep time is600s. The results show that the difference between experimental data and calculated result is small. The difference rate is about1.5%. The creep equation can be used to predict the long-term creep behavior of mesh. The results of theoretical long-term creep behaviors exhibit that PVDF mesh is still better than PP mesh. The theoretical creep deformation of the PVDF mesh is less than PP mesh in both wale and course direction. With the increasing of creep time, the creep deformation of PVDF mesh is still less than that of PP mesh. PVDF mesh exhibits better long-term stability than PP mesh. This method can shorten the time of creep experiment and obtain the long-term creep behavior of mesh through short-time experimental data.(3) Thermal finalization technology of PVDF hernia meshIn this paper, the orthogonal experiment method is used. Three levels of three factors (temperature, time and tension) are chosen. The influences of heat temperature, time and tension on basic parameters of PVDF mesh, such as density, thickness, porosity, etc, and mechanical properties of PVDF mesh, including tensile property, ball bursting property, suture retention property, elastic recovery property, are studied in this paper. The results show that tension and temperature have the largest influences on basic parameters and mechanical properties of PVDF mesh. Better mechanical properties of PVDF mesh can be obtained when the heat temperature is140℃, the time is10min and the tension is the intermediate force.(4) Manufacture and properties of patterned electrospun anti-adhesive membraneThis paper uses aluminum foil with PVDF mesh as a receive apparatus in electrostatic spinning process. The nanofibers are directly collected on PVDF mesh, forming a patterned membrane. This paper studies the effect of electrospinning process parameters on the nanofibers, the pattern, the hydrophilicity and permeability of membrane, and the influence of aluminum foil on membrane pattern. The results show that large solution concentration, small conductivity, low voltage, and short fiber receiving distance are conducive to obtain larger nanofiber diameter. The influence of the conductivity is more obvious than the others. For the porosity, the influences of electrospinning process parameters are small. There is no obvious relationship between porosity and process parameters. For surface area to volume ratio, the results show that with the decrease of the fiber diameter, the surface area to volume ratio increases. Patterned electrospun membrane has higher hydrophilicity and larger permeability than the nonwoven electrospun membrane. The water absorption rate of patterned electrospun membrane is530.8%, while nonwoven electrospun membrane is102.7%. The air permeability rate of patterned electrospun membrane is68.12%, while nonwoven electrospun membrane is25.16%. Results show that finer nanofibers are more susceptible to the electric field force, and are prone to deposited on the monofilament to form a clear patterned membrane. It is easier to obtain a clear patterned membrane when the monofilament diameter is larger and the mesh is thicker. The aluminum foil behind PVDF mesh is beneficial to attract the nanofibers to gather in the mesh surface, increase the stickiness between electrospun membrane and fabric, and improve the pattern definition.(5) Manufacture and properties of PCL/PVDF composite meshThis paper develops a novel type of PCL/PVDF composite mesh which has a sandwich structure. The mechanical and the biological properties of the composite mesh are tested to explore the practical feasibility of the composite mesh. The outer layer of PCL/PVDF composite is smooth PCL electrospun membrane, which has good biological performance. The middle layer is PVDF warp-knitted mesh with large pore size, which improves the mechanical properties of composite mesh. The results show that the mechanical properties of PCL/PVDF composite mesh are strong enough to meet the most of the body’s demands. Compared with the single PCL electrospun membrane, the tear resistance strength, the ball burst strength and the suture retention strength of PCL/PVDF composite mesh is obviously improved. Ball burst strength and suture retention strength is higher than the human demands (32N/cm and20N, respectively). The ball burst strength of PCL/PVDF composite mesh is34.86N/cm, while PCL electrospun membrane is only27.77N/cm. The suture retention strength of PCL/PVDF composite mesh in wale direction is23.52N and in course direction is30.74N, while PCL electrospun membrane is only9.4N. In addition, the elasticity of PCL/PVDF composite mesh decreases to the range of human body10%-30%. The elasticity of PCL/PVDF composite mesh is24.56%, while PCL electrospun membrane is50.56%. Cell toxicity test shows that the toxicity of PCL/PVDF composite mesh belongs to slight level. PCL/PVDF composite mesh can be used in clinic and will not produce serious adverse reactions.