Gabriella Zsoldos

Investigating poly-(vinyl-chloride)-polyethylene blends by thermal methods

Poly-vinyl-chloride (PVC)-polyethylene (PE) alloys were prepared by melt blending using both low- and high-density polyethylene without applying a compatibilizer. The PVC and the PE are incompatible polymers; in spite of this fact stable microheterogeneous materials were obtained. Mechanical methods e.g. tensile tests generally (measured in the usual concentration range) do not support any compatibility. At higher concentrations, the incompatible parts mask the effect of molecular mixing, easily detected at low PE contents. Dynamic mechanical (DMA), differential scanning calorimetric tests were carried out. Glass transition temperatures were determined by both methods. DMA tests were made at four frequencies, and the energy of activation of PVC main transition was also calculated. The decrease of glass-transition temperatures and energy of activation show that there is a slight mixing of the polymers. Specimens were also investigated by infrared method. From the results of IR spectra, grafting reaction of PE can be assumed onto the PVC because of its dehydrochlorination.

Examination of Biodegradable Polymer Thin Films

Fourier Transformed Infrared Spectroscopy (FTIR) was used to study the effect of water immersion of guar gum, gelatin and pektin films. Animal-derived gelatin, citrus-derived pektin and natural guar gum made from guar seeds was used to manufacture thin films (using a 2% concentration starting solution) by casting. The biodegradable polymer films were immersed in distilled water before FTIR analysis to absorb water. The immersion time varied between 1 to 15 sec for not to make hydrocolloids, only observe swelling. After 20 sec the biofilms effectively dissolved in the distilled water.

Polyethylene Crystalline Structure Differences in UHMWPE Ram Extruded Rod

Ultra-high-molecular-weight polyethylene (UHMWPE) is a subset of the thermoplastic polyethylene. Also known as high-modulus polyethylene, (HMPE), or high-performance polyethylene (HPPE), it has extremely long chains, with a molecular mass usually between 2 and 6 million Daltons. The longer chain serves to transfer load more effectively to the polymer backbone by strengthening intermolecular interactions. This results in a very tough material, with the highest impact strength of any thermoplastic presently made. UHMWPE is a odorless, tasteless, and nontoxic material. It is highly resistant to corrosive chemicals except oxidizing acids; has extremely low moisture absorption and a very low coefficient of friction; is self-lubricating (see boundary lubrication); and is highly resistant to abrasion, in some forms being 15 times more resistant to abrasion than carbon steel. When disease, trauma, or overuse cause natural joints to fail, they can be replaced by artificial ones to regain function and offset debilitating pain. Most often, artificial joints contain one or more metallic components integrated with bone, and a polymer component that promotes easy movement. The polymer must be biocompatible and tough enough to handle the loads imposed on the joint by normal life activities. It must also resist wear and mechanical damage, and have excellent lubricity, among other properties. This article discusses properties of RAM extruded ultra-high-molecular-weight polyethylene (UHMWPE).

Determing the Viscosity of Rarely Examined Glasses

High energy explosions and irradiation may cause that the minerals and mineraloids form glassy phase on the earth surface. We would like to determine the mechanical properties of these glassy materials. To achieve this and manufacture samples we need to measure the main technological property, the viscosity.

UHMWPE Modified Sodium Alginate

Aim of our experiments was to modify prosthetic material UHMWPE powder using sodium alginate. The sodium alginate has an important property that the appropriate chemical reagent could exchange its Na+ ions to Ca2+ ions. The Ca has important role in the healing process, so modifying this substance the UHMWPE material helps patients healing. In the first step we examined that the raw material UHMWPE powder is necessary to be treated in order to adhere alginate at the surface of the UHMWPE powder. In a second step, we examined that insoluble Ca alginate coating left at the surface of UHMWPE powder after the exchange of Na ions. The treated powders were analyzed by Fourier Transformed Infrared Spectroscopy and Diffential Scanning Calorymetry methods. SEM investigations were carried out on the prepared samples moreover energy-dispersive X-ray spectroscopy (EDAX) measurements were performed,-for detection of the presence of small amounts of Na and Ca ions. It has been found that the complex and complicated Caro’s acid chemical treatment is unnecessary in order to prepare alginate coated substrates. The best results were achieved by selecting the correct order of surface layer preparation; first coating the substrate with alginate solution then treating with aqueous CaCl2.

Tribological Testing Results Comparison by Microscope Techniques

Ultra high molecular weight polyethylene (UHMWPE) was modified by 20 % methyl-methacrylate (MMA). Specimens were examined by two directional tribological wearing methods. Wear resistance of the modified materials was found to be increased by 38 %. Despite the promising results further experiments are needed to utilize it as human implant.

In Vivo Failure Phenomena of Ultra-High Molecular Weight Polyethylene Acetabular Cups

During this study the distortion phenomenon was investigated on selected UHMWPE cups removed from patients, using 3dimensional measurement method. The cups investigated were machined by Metrimed Ltd. from ram extruded Chirulen 1020 type UHMWPE rods. The samples were measured with a 3D touch coordinate measurement device with an accuracy of 3 microns.