PEEK Biomaterials in Trauma, Orthopedic, and Spinal Implants

Physical aging of polymers

Analysis of the nonisothermal melt and cold crystallization kinetics of poly(aryl ether ether ketone ketone) (PEEKK) was performed by using differential scanning calorimetry (DSC). The Avrami equation modified by Jeziorny could describe only the primary stage of nonisothermal crystallization of PEEKK. And, the Ozawa analysis, when applied to this polymer system, failed to describe its nonisothermal crystallization behavior. A new and convenient approach for the nonisothermal crystallization was proposed by combining the Avrami equation with the Ozawa equation. By evaluating the kinetic parameters in this approach, the crystallization behavior of PEEKK was analyzed. According to the Kissinger method, the activation energies were determined to be 189 and 328 kJ/mol for nonisothermal melt and cold crystallization, respectively.

Nonisothermal melt and cold crystallization kinetics of poly(aryl ether ether ketone ketone)

Reversible crystallization and the rigid-amorphous phase in semicrystalline macromolecules

Non-isothermal crystallization of polymers

Crystallization behaviour of poly(ether-ether-ketone)

The effect of thermal history on the tensile properties of polyetheretherketone neat resin films was investigated at different test temperatures (125, 25, and -100) using four samples: fast-quenched amorphous (Q); quenched, then crystallized at 180 C (C180); slowly cooled (for about 16 h) from the melt (SC); and air-cooled (2-3 h) from the melt (AC). It was found that thermal history significantly affects the tensile properties of the material below the glass transition. Fast quenched amorphous films were most tough, could be drawn to greatest strain before rupture, and undergo densification during necking; at the test temperature of -100 C, these films had the best ultimate mechanical properties. At higher temperatures, the semicrystalline films AC and C180 had properties that compared favorably with the Q films. The SC films exhibited poor mechanical properties at all test temperatures.

Effect of thermal history on mechanical properties of polyetheretherketone below the glass transition temperature

A method and apparatus for measuring thermal diffusivity and molecular relaxation processes in a sample material utilizing two light beams, one being a pulsed laser light beam for forming a thermal lens in the sample material, and the other being a relatively low power probe light beam for measuring changes in the refractive index of the sample material during formation and dissipation of the thermal lens More specifically, a sample material is irradiated by relatively high power, short pulses from a dye laser Energy from the pulses is absorbed by the sample material, thereby forming a thermal lens in the area of absorption The pulse repetition rate is chosen so that the thermal lens is substantially dissipated by the time the next pulse reaches the sample material A probe light beam, which in a specific embodiment is a relatively low power, continuous wave (cw) laser beam, irradiates the thermal lens formed in the sample material The intensity characteristics of the probe light beam subsequent to irradiation of the thermal lens is related to changes in the refractive index of the sample material as the thermal lens is formed and dissipated A plot of the changes in refractive index as a function of time during formation of the thermal lens as reflected by changes in intensity of the probe beam, provides a curve related to molecular relaxation characteristics of the material, and a plot during dissipation of the thermal lens provides a curve related to the thermal diffusivity of the sample material

Double-beam optical method and apparatus for measuring thermal diffusivity and other molecular dynamic processes in utilizing the transient thermal lens effect

A method and apparatus for detecting optical radiation by optically monitoring temperature changes in a microvolume caused by absorption of optical radiation to be detected. More specifically, a thermal lens-forming material is provided which has first and second opposite, substantially parallel surfaces. A reflective coating is formed on the first surface, and a radiation-absorbing coating is formed on the reflective coating. Chopped, incoming optical radiation to be detected is directed to irradiate a small portion of the radiation-absorbing coating. Heat generated in this small area is conducted to the lens-forming material through the reflective coating, thereby raising the temperature of a small portion of the lens-forming material and causing a thermal lens to be formed therein. The thus-formed thermal lens is optically detected by irradiating the thermal lens by a collimated light beam. The light beam, after having passed through the thermal lens, is reflected by the reflective coating back through the thermal lens, and directed by a beam splitter to an optical detector. In a further embodiment of the invention, the optical radiation to be detected is passed through a template, thereby defining a plurality of areas on the radiation absorbing coating to be irradiated. A corresponding template is provided in a spread, collimated light beam to define a plurality of coherent light beams, each of which passes through a thermal lens in the lens-forming material. Each beam is then reflected by the reflective coating, passes back through the thermal lens, and is directed by a beam splitter to an optical detector. The invention is particularly useful as a broadband infrared detector.

Broadband optical radiation detector

A study was made on the stress relaxation behavior at 25 C of poly(methyl methacrylate) in uniaxial tension as a function of physical aging at both room temperature and 60 C. Test specimens were compression molded at 165 C, then quenched to room temperature and allowed to age for up to 30 days prior to testing. Stress relaxation curves measured after different aging times could be superposed to a single master curve for each aging temperature. Superposition was achieved by applying vertical and horizontal shifts. Hence, the shape of the response curves was not changed by aging. This is in accordance with observations made by Struik for tensile creep curves. Volume changes as a function of physical aging were also determined. Simple exponential relationships were observed between volume and both horizontal and vertical shifts. The horizontal shift implies a shift in the effective time scale caused by a change in free volume. The vertical shifts could be correlated with changes in Young's modulus caused by a change in density. For the range of aging studied, the response time scale varied over nearly two decades of log-time. For the same conditions modulus varied by 30 percent.

S. D. Hong

Papers

Crystallization behaviour of poly(ether-ether-ketone)

Effect of thermal history on mechanical properties of polyetheretherketone below the glass transition temperature

Double-beam optical method and apparatus for measuring thermal diffusivity and other molecular dynamic processes in utilizing the transient thermal lens effect

Broadband optical radiation detector

Effect of physical aging on stress relaxation of poly(methyl methacrylate)