Chemistry Reference
In-Depth Information
The morphology development upon cooling from the melt was also studied by polar-
ized optical microscopy.
The mechanical characterization of new polymeric systems is essential to under-
stand their performance under loads and may help to elucidate on the micro-structure
of heterogeneous systems, such as semi-crystalline polymers, blends, or copolymers.
Especially for implanted materials that will withstand mechanical stresses in clinical
use (e.g., in vascular or orthopaedic applications), a proper mechanical characteriza-
tion is among the most important physical tests that must be carried out. Implantable
materials should have a similar mechanical performance of the living tissues that will
be in contact with. Most of the biological tissues, possibly excepting dental enamel
and echinoderm skeletons, exhibit a time-dependent mechanical behavior due to their
viscoelastic nature. Therefore, it is important to evaluate the solid-state rheological
properties of materials aimed at being used in biomedical applications. Dynamic me-
chanical analysis (DMA) is a thermal analysis technique in which the response of the
material under a cyclic load or strain excitation is measured as a function of frequency
or temperature, being adequate to probe the viscoelastic properties of polymeric sys-
tems. It has also been shown that this technique may be useful to extract relevant infor-
mation in biomaterials. A few authors have shown some DMA data of PCL and SPCL,
but they only reported the results at a single frequency; moreover, the data were never
integrated in the context of the potential biomedical applications of the materials. In
this work DMA was also used to access the thermal properties of the studied materials,
especially near glass transition temperature (Tg), and to obtain information about the
viscoelastic properties in this temperature region at meaningful frequencies.
Hydroxyapatite--Starch Nano Biocomposites Synthesis and Characterization
Chemical formula of Hydroxyapatite (HAp) is Ca10(PO4)6(OH)2 which is very simi-
lar to the materials forming the bones in the human body. The HAp crystals in natural
bone are needle-like or rod-like in shape 40-60 nm in length, 10-20 nm in width, and
1-3 nm in thickness. The synthesized HAp with bone-bonding properties is widely
used in hard tissue replacement due to their biocompatibility and osteoconductive
properties. Many characteristics of HAp, such as surface characteristics and bioactiv-
ity can be affected by the shape of HAp crystal. Therefore, the applications of the HAp
can be expanded by controlling the crystal shape of the nanometer HAp, such as nee-
dle-like, spherical, plate-like shape and so on. At present, many studies have reported
to synthesize the nanometer HAp with different shapes. For example, the needle-like
HAp has been synthesized by different processing methods including organic gel sys-
tems, homogeneous precipitation, or hydrothermal technology. The rod-like HAp has
been synthesized by precipitating calcium nitrate tetra hydrate and ammonium dibasic
phosphate in the presence of polyacrylic acid followed by hydrothermal treatment.
Brittleness of HAp limits its use. One of the methods to solve the problem is combina-
tion of it with polymer. Surfaces of organic materials can be tailored to achieve differ-
ent properties, such as the capability of carrying functional groups, chelate to metal
ions by their functional groups and hydrophilicity [9]. For instance, major approach
in the development of materials for bone regeneration and replacement is the use of
degradable polymers as matrices. Biodegradable materials have to degrade without
Search WWH ::
Custom Search