Papers by Keyword: Biodegradable Material

Abstract: Fused Deposition Modeling (FDM) is widely used in additive manufacturing. The main limitations of 3-Dimentisonal (3D) printing are the expansive cost of the material and its low strength as compared to the traditional molding process. The supported material was more expensive because of the extrusion process. The high surface roughness in the nature of 3D printed objects is the principal reason for mechanical property weakness. To eliminate such problems, a pellet-based 3D printer coupled with the layup fiber technique was introduced in this preliminary study. The obtained result indicated that the sample produced by the pellet-based printer had the highest mechanical strength in the machine direction. A reduction in tensile strength was found at another raster angle. After considering the differences between carbon fiber (CF) formats, it was found that chopped fiber was ineffective in terms of printed strength. At the same time, the layup fabric type and continuous fiber could promote better mechanical properties. When analyzing the ratio of maximum strength/fiber weight, it should be noted that continuous fiber presented the highest reinforced efficiency.

Abstract: Magnesium and its alloys are potential biodegradable implant materials. However, they are characterized by rapid degradation in the electrolytic environment of the body. This phenomenon might result a sudden implant failure before bone restoration was complete, or inflammation subsided. This research will explore ways to improve the corrosion resistance of AZ31 magnesium alloy by improving the coating layer of hydroxyapatite (HA) through multiple coating layers by an electrophoretic deposition (EPD) process. In this study, the quality of the coating layer was improved by multiple coating processes without using any binders. X-ray diffraction spectrometer (XRD) showed that an amorphous structure of HA was successfully deposited on the AZ31 alloy. Scanning electron microscopy (SEM) has been used to observe that the morphology of the AZ31 alloy coated with multiple layers of HA has a denser coating structure with improved adhesion at the interface as compared to the single coating layer. A denser coating structure with greater bonding between the coating layer and the substrate is expected to protect the substrate from a high corrosion rate, thus resulting in a longer period of biodegradation as in implant in the electrolytic environment.

Abstract: Both magnesium and zinc are considered as suitable elements for preparation of biodegradable materials that can be gradually dissolved in human organism without the production of toxic compounds. Although many magnesium-based materials possess good mechanical properties and biocompatibility, corrosion rates accompanied by hydrogen release and pH increase are too high. On the contrary, Zn is characterized by much lower corrosion rate in physiological solution compared to magnesium and its alloys. Therefore, we study Zn-Mg binary alloys with 0-7 wt.% of Mg. In this case, magnesium was selected to improve mechanical properties and biocompatibility of pure Zn. The structures of alloys were studied by an optical metallographic microscope and SEM equipped with EDS analyzer. Mechanical properties were studied using Vickers hardness measurements. Our results showed that mechanical properties of binary Mg-Zn alloys improve with increasing content of Mg, achieving the maximum at eutectic composition. Higher Mg concentrations strongly deteriorate mechanical properties of binary Mg-Zn alloys.

Abstract: Directly starting from D,L-lactic acid (LA) and melamine (MA), poly (lactic acid-co- melamine) [P(LA-co-MA)] as a kind of potential polymeric flame retardant is synthesized via melt polycondensation. The properties of P(LA-co-MA) s at different molar feed ratios are characterized by XRD, DSC and TGA. Most decomposition temperatures of P(LA-co-MA) s are higher than these of homopolymer poly (D,L-lactic acid) (PDLLA). For the char yield, all copolymers have higher char yield than PDLLA. Furthermore, the more MA in the feed content, the higher char yield.

Abstract: When poly (lactic acid-co-melamine) [P(LA-co-MA)] is synthesized via direct melt polycondensation (DMP), with the more MA in the feed content, the copolymer with a three-MA-core structure linked by the ether bond is formed. Increasing the molar feed ratio n(LA)/n(MA), the structure of the copolymers is gradually changed from multi-core structure into SPLA structure only containing one MA core, and a peak value of M_w exists as expected. The aromatic cores with different functional groups have an important influence on the M_w peak value, and the internal factors are the conjugate effect and the nucleophilicity caused by the different functional groups themselves.

Abstract: Using flame retardant melamine (MA) as a new aromatic core, biodegradable material poly (lactic acid-co-melamine) [P(LA-co-MA)] with different molar feed ratios are synthesized via direct melt copolycondensation. The structures of P(LA-co-MA) s are characterized by FT-IR, ¹H-NMR, ¹³C-NMR and GPC. The results indicate that MA moiety as the core is incorporated into the PLA backbone as expected, and the obtained products are copolymers indeed.

Abstract: Directly starting from D,L-lactic acid (LA) and melamine (MA), novel star-shaped biodegradable material poly (lactic acid-co-melamine) [P(LA-co-MA)] as a kind of potential flame retardant is synthesized via melt polycondensation. When the molar feed ratio n(LA)/n(MA) is 60/1, the optimal synthetic conditions are discussed. After the prepolymerization at 140 °C for 8 h, using 0.4 wt % stannous chloride as the catalyst, the melt copolymerization at 160 °C for 8 h gives the copolymer with the biggest intrinsic viscosity 0.87 dLg^-1.

Abstract: The development of biomaterial has reached biodegradable stage. Biodegradable means it can be degraded after certain period of time after implantation and cause no harm for the system. Degradable Biomaterial has the potential to be used as Coronary Stent to minimize the risk from thrombosis issue. Thrombosis is a symptom of body defense where will be a clots blood effect around stent area. The formation of clots blood will disturb a blood flow in artery and it will result a restenosis effect.

Abstract: Nine groups of biomass packaging materials with different formula have been synthesized, which were made up of straw fiber and starch by foaming technique. In order to analysis the influence of main composites on cushion performance, a series of tests were conducted to measure the impact behavior, rebound property and static compression performance of materials. Measuring results show that material impact toughness increases with content of fiber. When the content of plasticizer is 10%, the material impact energy absorption is maximum, when the ratio of active agent and foaming agent is 1:1, a stable foaming process can be obtained, which makes the bubble uniform and increases rebound rate.

Abstract: The starch grafted acrylic super absorbent resin was used as a basic material of refrigerant in insulating packaging. The influence of the amount of initiator on water absorption ability of starch grafted acrylic super absorbent resin was investigated. When the amount of initiator is 4 percent of the starch, the resin's water absorption that is 230g/g displays the best. By adding NaCl solution, the phase change temperature of refrigerant can be conditioned. The experimental results show that the phase change temperature and the latent heat of refrigerant decrease as the NaCl solution concentration increases. The starch grafted acrylic super absorbent resin and the NaCl solution with the concentration of 0~5 percent as refrigerant can be used to transport the products whose required temperatures is between -4 and 0°C. The starch grafted acrylic super absorbent resin can replace the ordinary high polymer materials, playing the role of being easily biodegradable and friendly to environment.