Two-dimensional FTIR spectroscopic analysis of crystallization in cross-linked poly(ether ether ketone)

This study focuses on comprehensively investigating polyethylene glycol (PEG) with different molecular weight. Thermal properties of the PEGs were investigated by differential scanning calorimetry (DSC), as well as gradual melting and freezing tests with thermocouples. Results show that the degree of PEG crystallization increased with the increasing of the molecular weight of polymers. The temperatures of pure PEG 1000 and PEG 1000‐PEG 600 blends ranged from 20 to 50°C. The apparent activation energy of pure PEG1000 was 300 kJ/mol, whereas that of the PEG blend was 239 kJ/mol. During the crystallization process, Avrami index n ranged from 5 to 3 and half‐crystallization time t1/2 decreased with the acceleration of the crystallization rate R. This difference was due to the increase in polydispersity of the PEG system and decrease in the degree of crystallization. POLYM. ENG. SCI., 54:2872–2876, 2014. © 2014 Society of Plastics Engineers

A comprehensive investigation was carried out to study the effects of in vacuo γ-irradiation on the crystallization behavior of ultrahigh molecular weight polyethylene (UHMWPE) used in joint replacement prostheses. A wide variety of experimental techniques, including differential scanning calorimetry (DSC), wide-angle X-ray diffraction (WAXD), synchrotron small-angle X-ray scattering (SAXS), hot stage optical microscopy (HSOM), and depolarized light scattering (DLS), was used to access information about lamellar and supramolecular morphology, degree of crystallization, and crystallization kinetics during different nonisothermal and isothermal procedures. It was found that network formation prevailed over chain scission processes in the in vacuo irradiated samples, lowering the crystallizability of the polymer due to imposed geometrical constrains. In addition, the physical net of stable entanglements accompanied by the extensive cross-linking produced by γ-irradiation generated quite unique crystallization morphology of UHMWPE. We detected the presence of distinct ordered grains, whose size depended on the irradiation dose, that did not “melt” even after being subjected to a high-temperature heating cycle. At lower temperatures, however, progressive chainlike nucleation proceeded right on the skirt of these domains, maintaining the constant crystallization rate regardless of the degree of undercooling.

Chapter Ten - Differential scanning calorimetry (DSC) of nanoencapsulated food ingredients

The crystal condition of the poly lactic acid that was a crystalline polymer was changed (degree of crystallization etc.), and the tensile test was done. Then the influence of crystal condition on the mechanical attribute was examined. Therefore, heat-treatment was first given to the material based on the melting point and the crystallization temperature of the material requested from differential scanning calorimetry (DSC), and the material that changed the degree of crystallization was made. Next, when the change in the degree of crystallization in the extensional deformation was confirmed because the crystallinity dependence was seen in the extensional deformation as a result of doing the tensile test and having examined it, it was understood that the degree of crystallization had changed by the extensional deformation.

ABSTRACTBlends of poly (ethylene terephthalate), or PET, and polycarbonate (PC) over a range of compositions were studied in isothermal crystallizations from the melt using differential scanning calorimetry (DSC). Both crystallization rate and degree of crystallinity of PET depend on blend composition. The glass transition temperature, Tg, of PET and PC in blends and pure polymer were also measured by DSC. Elevation of the Tg of PET and depression of the Tg of PC are observed upon blending. In cooling scans, dynamic crystallization from the melt was observed. In PET/PC blends with high PC content, a novel dual-peak crystallization of PET was observed. The effects of thermal history on crystallization kinetics and degree of crystallinity were also determined in isothermal crystallization studies. For Melt processing times between 1 and 30 Min and for processing temperatures between 280 and 300 °C, Melt processing temperature was seen to have a stronger effect than processing time.

Poly(lactic acid) (PLA)/cellulose nanocrystal (CNC) nanocomposites with 1 or 3 phr of CNC were prepared by melt mixing and compression molding then their % crystallinities as well as crystallization and melting behavior during the first heating/cooling/second heating process were investigated by differential scanning calorimetry (DSC). Isothermal crystallization at 80–130°C for 5 min was performed during the cooling process to see how the isothermal crystallization affects % crystallinity at 25°C. The % crystallinity at 25°C as well as the crystallization rate of the nanocomposite increased with CNC content and showed a maximum at the isothermal crystallization temperature of 105°C regardless of CNC content. The bimodal DSC melting peaks observed during the second heating process were considered due to the crystals with many defects (α′) and the crystals with more perfect structure (α), respectively. Isothermal crystallization kinetic analysis by Avrami equation showed that the Avrami exponents of the nanocomposites were about 1, meaning a rod‐ or disc‐shaped crystal growth mechanism. Improving the mechanical properties of the PLA/CNC nanocomposite would be possible because the % crystallinity at 25°C could be effectively increased by changing CNC content and cooling history.Highlights PLA/CNC nanocomposites. Crystallization and melting behavior analysis of the nanocomposites by DSC. Isothermal crystallization at 80–130°C for 5 min during cooling by DSC. Crystallization degree was maximum for the isothermal crystallization at 105°C. Isothermal crystallization kinetic analysis by Avrami equation.

A study on the friction and wear behavior of polytetrafluoroethylene filled with potassium titanate whiskers

Objective To investigate the effects of different particle sizes on the collagen structure of demineralized bone matrix (DBM) and the effectiveness of dry ice as an irradiation protectant in the procedure of gamma irradiation. Methods DBM samples with different particle sizes (0.5-1.0 mm, 1.2-2.8 mm, 3.3-4.7 mm and 5.7-7.0 mm) were prepared, and sterilized with several doses of gamma irradiation (0 kGy, 15 kGy and 25 kGy) at room temperature. Additionally, another group of DBM samples were sterilized with 25 kGy gamma irradiation with protective agent. Changes in surface and characteristics of collagen were observed by using scanning electron microscope (SEM), Sodium dodecyl sulfatepolyacrylamide gel electrophoresis (SDS-PAGE), differential scanning calorimetry (DSC) and carbonyl content. Results The color of collagen extract indicated that oxidative damage is directly related to irradiation dose. SEM showed that the gamma irradiation caused collagen structure disorder and fiber breakage. As the irradiation doses increased, the damage area significantly increased. When the particle size increased, the damage area tended to decrease. The DSC showed that the thermal denaturation temperature of 5.7-7 mm, 3.3-4.7 mm, 1.2-2.8 mm and 0.5-1.0 mm were 142.8℃, 97.3℃,84.3℃ and 83.9℃, respectively. The differences of the thermal denaturation temperatures among the four particle sizes were statistically significant (F=0.560, P=0.650). Collagen structure was destroyed by gamma irradiation, resulting in a decrease in collagen molecular weight. While, large particle DBM had a tendency to resist radiation damage. There was a significant difference on the contents of carbonyl in collagen from same particle sizes of DBM with different irradiation dose. The carbonyl content gradually decreased with the increase of particle size, but the difference was not statistically significant (F=0.560, P=0.650). Conclusion The gamma irradiation and collagen oxidative damage have obvious dose-response relationship. With the increase of gamma irradiation dose, the degree of collagen damage increases. The sizes of DBM could affect the sensitivity of collagen to gamma irradiation. With the decrease of particle sizes, DBM particles are more susceptible to gamma irradiation damage. Additionally, dry ice, as a radiation protection agent, has a certain degree protection effect against radiation. Key words: Bone matrix; Collagen; Radiation; Gamma rays

Exfoliated poly(ethylene terephthalate) (PET)‐layered silicate nanocomposites (PetLSNs) excluding (PetLSNeom) and including (PetLSNiom) organic modifiers were obtained by solution methods with and without solvent‐nonsolvent system, respectively. From wide angle X‐ray diffraction and high resolution transmission electron microscopy, both PetLSNs were found to have exfoliated structure attributed to sufficient dispersion of silicate in prepared solvents, regardless of sample preparation method. However, organic modifier in PetLSNeom was confirmed to be well removed by elemental analysis, whereas organic modifier was still remained in PetLSNiom. Thus, the effect of the presence and absence of organic modifiers in PetLSNs on the nonisothermal crystallization behavior was investigated by differential scanning calorimetry (DSC) on the basis of a modified Avrami analysis and polarized optical microscopy (POM). From DSC results, it was found that both PetLSNs had higher degrees of crystallinity and shorter crystallization half‐times than neat PET, because of the dispersed silicate layers acted as nucleating agents in both PetLSNs. However, PetLSNiom exhibited a lower degree of crystallinity and longer half‐time of crystallization than PetLSNeom. Difference of crystallization behavior between PetLSNeom and PetLSNiom was ascribed to organic modifier in PetLSNiom, which may act as crystallization inhibitors. POM measurements also revealed the results which were in good agreement with crystallization behavior observed from DSC measurement. © 2008 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 46: 989–999, 2008

Plasticized poly (lactic acid) (PPLA) was prepared by melt blending poly (lactic acid) (PLA) with 10 wt% of poly (ethylene glycol) (PEG), with varied molecular weights range from 400 to 4000. The structure, thermal property, morphology, and surface free energy of the PPLA were investigated by Fourier transform infrared spectroscopy (FTIR), differential scanning calorimeter (DSC), thermogravimetric analysis (TGA), scanning electron microscopy (SEM), and contact angles (CA). The resulting PPLA results indicated that the introduction of PEG to the blend systems resulted in a ductile fracture, a decrease in the melt temperature (Tm) and glass transfer temperature (Tg), and an increase in the degree of crystallization (χc), which indicated an improved flexibility. In addition, the polarity of the PPLA increased and the surface free energy decreased. The resulting PPLA was subsequently used as matrix to blend with wood flour to prepare composites. The mechanical strength, melting behavior, thermal stability, and microscopy of the PPLA/wood flour composites were also evaluated. These results illustrated that the plasticized PPLA matrix was beneficial to the interfacial compatibility between the polar filler and the substrate.

Poly(ethylene glycol) (PEG) dissolves in the room-temperature ionic liquid 1-ethyl-3-methylimidazolium ethylsulfate [EMIM][EtSO(4)] above approximately 60 degrees C, the neat polymer's melting temperature, and if polymer concentration and molecular weight are high enough, the solution transforms into a semitransparent gel when cooled. The modulus, reaching 100 KPa or higher, is strongly affected by PEG concentration, and self-supporting materials are made even from solutions somewhat below coil overlap. Via differential scanning calorimetry (DSC), rheology, and optical microscopy, thermoreversible solidification is traced to kinetically frustrated polymer crystallization, an established mechanism for many pairings of crystallizable polymer with aqueous or organic solvent. Optical microscopy reveals nucleation and growth of PEG crystals with a largest dimension of tens to hundreds of micrometers. Crystalline chain packing in gels is identical to that of neat PEG, and degrees of crystallization are similar. Simple preparation, nontoxicity, and vanishing volatility suggest unique new gel applications.

Overall crystallization behavior and polymorphism of partially miscible blends of poly(vinylidene fluoride)/ poly(ethylene oxide) (PVDF/PEO) were systematically investigated. The PVDF/PEO blends were prepared from solution in the whole composition range. Isothermal and non-isothermal experiments were carried out using differential scanning calorimetry (DSC). Since the components of the blend crystallize separately due to high difference of the melting points, the changes in melting, crystallization, and equilibrium melting temperatures of PVDF and PEO as well as the degree of crystallization were evaluated. As the binary blends display an asymmetric lower critical solution temperature (LCST)-type phase diagram, the crystallization behavior and kinetics were strongly affected by the miscibility state of the blends in the melt. Particularly, the overall crystallization of PEO was accelerated in the blends with high level of PEO (>50 wt%) by two different mechanisms. The formation of phase separated domains at this composition range enhanced the nucleation ability due to the “spinodal decomposition/ interface assisted crystallization”. Moreover, presence of preexisting crystals of PVDF could act as a substrate for PEO crystallization and increased the crystallization growth rate. Wide angle X-ray diffraction (WAXD) and Fourier transform infrared spectroscopy (FTIR) were also utilized to study the crystalline polymorphism of PVDF and PEO in the blends.

Radiation processing, being a physical process, is an environmentally friendly alternative to chemical modifications. It is economically viable, safe, and possesses several advantages over other conventional methods employed for modification and grafting. To improve the physico-mechanical properties of Ca-alginate fiber (CaAF), poly (ethylene glycol) (PEG) was grafted by applying γ-radiation of different intensities. The effect of γ-irradiation on the physico-mechanical, thermal, morphological, thermal and water aging, water, and simulated body fluid (SBF) uptake were evaluated. FT-IR results confirmed that PEG was successfully grafted onto Ca-alginate fibers by γ-irradiation. From the detailed experimental results, irradiation doses and PEG concentration were optimized for grafting processes. The results showed that 50% PEG and 2.5 kGy irradiation dose yielded the highest tensile strength. Differential scanning calorimetric (DSC) analysis showed that with increasing γ-intensity a decrease of dehydration temperature of the fibers had occurred. On the other hand, the glass transition temperature (T g) increased with increasing irradiation dose. The tensile cracked surfaces of the grafted alginate fibers were analyzed by scanning electron microscope (SEM) in order to monitor their surface morphologies. The SEM images of the cracked surfaces demonstrated that spherical shape rods were present for irradiated fiber sample while no such rods were observed for non-irradiated fibers. The characteristic data obtained from SBF and water uptake, and water and thermal aging experiments indicated that CaAF grafted with 50% PEG by applying 2.5 kGy γ-irradiation can be potentially employed for biomedical purposes, such as surgical suture.

Effect of γ-irradiation on cationic and hydrogen zeolites reactivity: clinoptilolite and ferrierite

In this article, the syntheses and thermal properties of several alkyne- and phosphorus-containing materials are discussed. The materials were synthesized using substituted phenolic molecules which were added to phosphorus oxychloride. The materials synthesized include phosphine oxides, phosphates, diphosphates, and oligophosphates. The thermal properties of the synthesized materials were studied using differential scanning calorimetry (DSC) and thermal gravimetric analysis (TGA). In general, the DSC and TGA data showed that synthesized materials containing alkynes and phosphorus had good-to-excellent thermal stability with high-onset decomposition temperatures. Materials with a high alkyne-to-phosphorus ratio showed the highest char yields. DSC data showed crosslinking events for the alkynes and the phosphorus moieties. DSC also showed that the alkynes crosslinked at lower temperatures than the phosphates. Based on the TGA and DSC data of the alkyne-containing phosphorus materials, alkynes generally appeared to be better char-inducing groups than was phosphorus. The materials were blended into polycarbonate and tested for ignition resistance using the UL-94 flame test. In two cases, these halogen-free compounds, with their dual alkyne/phosphorous crosslinking mechanisms, are condensed-phase flame retardants that can be easily blended into polycarbonate at 10 wt % loadings to afford blends that give a UL-94 V-0 rating. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 73: 707–718, 1999