Annealing of nylon-1010 under high pressure

Full Paper: A study has been made on the annealing of nylon-1010 under high pressures. Heat treatment of melt-crystallized nylon-1010 was performed at 250degreesC for 30 min in the pressure range 0.7 similar to 2.5 GPa. It was found that the triclinic crystals of virgin nylon-1010 were retained at pressures less than 1.0 GPa or larger than 1.2 GPa. The X-ray diffraction intensity of (100) planes decreased with increasing pressure. The diffraction peaks shifted slightly to higher angles (2theta) relative to the virgin nylon-1010, indicating dense packing of polymer chains at high pressures. The highest melting temperature was 208degreesC for the sample annealed at 1.5 GPa. No extended-chain crystals were formed under the experimental conditions. Crosslinking occurred in the pressure range 1.0 similar to 1.2 GPa. The structure of the crosslinked samples was characterized by means of infrared spectroscopy and X-ray photoelectron spectroscopy. It is concluded that a mechanism of crosslinking via carbodiimide can explain the nature of crosslinking of nylon-1010 annealed at high pressures. The remarkable changes of the structure of annealed nylon-1010 are also discussed in this article.

Non-isothermal crystallization behavior and kinetics of metallocene short chain branched polyethylene

The non-isothermal crystallization behavior and kinetics of metallocene short chain branched polyethylene were investigated via DSC at cooling rates from 2.5 to 20 degreesC/min, and subsequent heating at rate of 10 degreesC/min. To verify the effect of molecular weight and branching content on crystallization, three group samples were chosen: (1) linear polyethylene with low molecular weight and high molecular weight; (2) low molecular weight polyethylene with low branching content and high branching content; (3) high molecular weight polyethylene with low branching content and high branching content. The results show that crystallization temperature, crystallinity, melting temperature and crystallization rate are highly branching content-dependent. Molecular weight effect is less important, compared to branching content. A dramatic decrease of crystallization temperature, crystallinity, crystallization rate and melting temperature was observed for branched samples. The non-isothermal kinetics was analyzed via the methods, developed by Gupta and Mo Zhi-shen, and good agreement was obtained.

Crystallization and Crosslinking of polyamide-1010 under elevated pressure

The structure and thermal properties of polyamide-1010 (PA1010), treated at 250degreesC for 30 min under pressures of 0.7-2.5 GPa, were studied with wide-angle X-ray diffraction (WAXD), infrared (IR), differential scanning calorimetry (DSC), and thermogravimetric analysis (TGA). Crystals were formed when the pressures were less than 1.0 GPa or greater than 1.2 GPa. With increasing pressure, the intensity of the diffraction peak at approximately 24degrees was enhanced, whereas the peak at approximately 20degrees was depressed. The triclinic crystal structure of PA1010 was preserved. The highest melting temperature of the crystals obtained in this work was 208degreesC for PA1010 treated at 1.5 GPa. Crosslinking occurred under pressures of 1.0-1.2 GPa. Only a broad diffraction peak centered at approximately 20degrees was observed on WAXD patterns, and no melting and crystallization peaks were found on DSC curves. IR spectra of crosslinked PA1010 showed a remarkable absorption band at 1370 cm(-1). The N-H stretching vibration band at 3305 cm(-1) was weakened. Crystallized PA1010 had a higher thermal stability than crosslinked PA1010, as indicated on TGA curves by a higher onset temperature of decomposition.

Crystallization behavior of a novel ether ketone polymer containing meta-phenylene linkage: PEKEKK (T/I)

Nonisothermal and isothermal melt crystallization kinetics of a novel aryl ether ketone polymer containing meta-phenylene linkages, PEKEKK (T/I), were studied by differential scanning calorimetry (DSC). The Avrami equation modified by Jeziorny and a new approach by combining the Avrami equation with the Ozawa equation could describe the nonisothermal crystallization. Isothermal crystallization could also be described by the Avrami equation. The activation energies were 187 and 159 kJ/mol for nonisothermal and isothermal crystallization, respectively. Using the Hoffman-Weeks method, the equilibrium melting point T-m(o) was estimated as 353 degrees C. From the spherulitic growth equation proposed by Hoffman and Lauritzen, the nucleation parameter K-g of the isothermal melt crystallization was estimated as 5.49 x 10(5) K-2. The crystallization characteristics of PEKEKK (T/I) were compared with those of all-para PEKEKK. The differences were explained by differences in the chain flexibility of the two polymers.

Radiation effects on the immiscible polymer blend of nylon1010 and high-impact polystyrene (HIPS) I: Gel/dose curves, mathematical expectation theorem and thermal behaviour

This paper studies the radiation properties of the immiscible blend of nylon1010 and HIPS. The gel fraction increased with increasing radiation dose. The network was found mostly in nylon1010, the networks were also found in both nylon1010 and HIPS when the dose reaches 0.85 MGy or more. We used the Charleby-Pinner equation and the modified Zhang-Sun-Qian equation to simulate the relationship with the dose and the sol fraction. The latter equation fits well with these polymer blends and the relationship used by it showed better linearity than the one by the Charleby-Pinner equation. We also studied the conditions of formation of the network by the mathematical expectation theorem for the binary system. Thermal properties of polymer blend were observed by DSC curves. The crystallization temperature decreases with increasing dose because the cross-linking reaction inhibited the crystallization procession and destroyed the crystals. The melting temperature also reduced with increasing radiation dose. The dual melting peak gradually shifted to single peak and the high melting peak disappeared at high radiation dose. However, the radiation-induced crystallization was observed by the heat of fusion increasing at low radiation dose. On the other hand, the crystal will be damaged by radiation. A similar conclusion may be drawn by the DSC traces when the polymer blends were crystallized. When the radiation dose increases, the heat of fusion reduces dramatically and so does the heat of crystallization. (C) 1999 Elsevier Science Ltd. All rights reserved.

Synthesis and characterization of novel crosslinkable side-chain liquid crystalline polyesters

Crosslinkable side-chain liquid crystalline polyesters PCn from N-[n-(4-(4-nitrophenylazo)phenyloxy)alkyl]diethanolamine (Cn, n = 3, 5, 6, 10) as mesogenic monomers and maleic anhydride were synthesized and characterized. The thermal properties of PCn's were studied by means of DSC, polarized optical microscopy (POM) and wide angle X-ray diffraction (WAXD), and the results showed that all the polymers studied exhibit enantiotropic liquid crystallinity. In the molar mass independent region, the relatively high content of cis -CH=CH- groups in the polymer backbone of PC3 causes an increase of the melting temperature (T-m) and a decrease of T-g and isotropisation temperature (T-i). The crosslinking of PCn in the radical polymerization with styrene was confirmed by FTIR spectroscopy. The absorption band at 1300 cm(-1) attributed to the in-plane C-H-bending vibration of trans -CH=CH- in the polymer backbone disappeared after crosslinking, indicating that the trans -CH=CH- functions are consumed in the crosslinking polymerization of styrene.

Crystallization kinetics of poly(ether ether ketone) (PEEK) from its metastable melt

After isothermal crystallization of the amorphous poly(ether ether ketone), double endothermic behaviour can be found through differential scanning calorimetry experiments. During the heating scan of semicrystalline PEEK, a metastable melt, which comes from the melt of the thinner lamellar crystal populations, can be obtained between these two endotherms. The metastable melt can recrystallize immediately just above the lower melting temperature and form slightly thicker lamellae than the original ones. The thickness and the perfection depend upon the crystallization time and the crystallization temperature. By comparing the TEM morphological observations of the samples before and after partial melting, it can be shown that lamellar crystals, having different thermodynamic stability, form during isothermal crystallization. After partial melting, only the type of lamellar crystal exhibiting the higher thermodynamic stability remains. Wide angle X-ray diffraction measurements shows a slightly change in the crystallinity of the samples before and after the partial melting. Small angle X-ray scattering results exhibit a change in the long period of the lamellar crystals before and after the partial melting process. The crystallization kinetics of the metastable melt can be determined by means of differential scanning calorimetry. The kinetic analysis showed that the isothermal crystallization of the metastable PEEK melt proceeds with an Avrami exponent of n = 1.0 similar to 1.4, reflecting that probably one-dimensional or an irregular line growth of the crystal occurred between the existing main lamellae with heterogeneous nucleation. (C) 1998 Elsevier Science Ltd. All rights reserved.

Synthesis of a new aryl ether ketone polymer

The synthesis of a new aryl ether ketone polymer with an advantageous ratio of glass transition temperature to melting temperature is reported.

Isothermal and nonisothermal melt crystallization kinetic behavior of poly(aryl ether biphenyl ether ketone ketone): PEDEKK

Isothermal and nonisothermal melt crystallization kinetics of a novel poly(aryl ether ketone), PEDEKK, were investigated by differential scanning calorimetry. Several kinetic analyses were used to describe the crystallization behavior. The activation energies were determined as 425 and 176 KJ/mol for isothermal and nonisothermal crystallization, respectively. The equilibrium melting point T-m(o) was estimated to be 444 degrees C by using the Hoffman-Weeks approach. The observed crystallization characteristics of PEDEKK were compared with those of the other members of the poly(arpl ether ketone) family.

Studies on biodegradable poly(hexano-6-lactone) fibers 1. Structure and properties of drawn poly(hexano-6-lactone) fibers

Using high molecular weight (M-n=80,000) Poly(hexano-6-lactone) (PCL'), tough and high tenacity PCL monofilaments with various draw ratios (undrawn to 9 times drawn) were prepared by melt-spinning. The relationship between microstructure and properties of the PCL fibers is described in this current IUPAC Technical Report. Analysis of microstructure of the drawn PCL fibers by wide-angle X-ray diffraction revealed typical c-axis orientation with an increase in crystallinity. It was also supported by sonic velocity measurements. The thermal, mechanical, and dynamic mechanical properties of the PCL fibers were affected significantly by draw ratio. DSC thermograms showed that the melting temperature and the enthalpy of fusion increased with draw ratio. The temperature dependence curves of dynamic viscoelasticity showed that the temperature at tan delta peak of alpha dispersion corresponding to the glass transition temperature shifted toward higher temperature and the peak value of tan delta decreased with draw ratio. The dynamic storage modulus and the sonic modulus increased with draw ratio. These results are due to the increase in crystallinity and molecular orientation with drawing, and are responsible for an increase in tensile tenacity as well as knot tenacity of the PCL fibers.

Thermal analysis of ethylene propylene copolymer-grafted-acrylic acid

The thermal properties of ethylene propylene copolymer-grafted-acrylic acid (EP-g-AA) were investigated by using differential scanning calorimetry (DSC). Compared with the ethylene propylene copolymer (EP), the peak values of the melting temperature (T-m) of the propylene sequences in the grafted EP changed a little, the crystallization temperature (T-c) increased about 8-12 degrees C, and the melting enthalpy (Delta H-m) increased about 4-6 J/g. The isothermal crystallization kinetics of grafted and ungrafted samples was carried out by DSC. Within the scope of the researched crystallization temperature, the Avrami exponent (n) of the ungrafted sample was 1.6-1.8, and that of grafted samples were all above 2, which indicated that the grafted monomer could become the crystal nuclei for the crystallization of propylene sequence. With increasing grafted monomer content, the crystallization rate of propylene sequence in grafted EP increased; it might be the result of rapid nucleation rate and crystal growth rate.

Epitaxial recrystallization of HDPE-quenched ultrathin films on oriented iPP substrates

The recrystallization behavior of high-density polyethylene (HDPE) on the highly oriented isotactic polypropylene (iPP) substrates at temperatures below the melting temperature of HDPE has been investigated by means of transmission electron microscopy. The results obtained by the bright-field observation and the electron diffraction show that upon annealing the HDPE-quenched films on the oriented iPP substrates at temperatures below 125 degrees C, only a small amount of HDPE recrystallizes on the iPP substrate with [001](HDPE)//[001](iPP), while annealing the HDPE-quenched films at temperatures above 125 degrees C, all of the HDPE crystallites recrystallize epitaxially on the iPP substrate with [001](HDPE)//[101](iPP). (C) 1997 John Wiley & Sons, Inc.

The synthesis and thermotropic liquid crystalline behavior of the novel poly(aryl ether ketone)s containing chloro-side group

The novel poly(aryl ether ketone)s containing chloro-side group were synthesized by nucleophilic substitution reactions of 4,4'-biphenol and chlorohydroquinone with either 4,4'-difluorobenzophenone(BP/CH/DF) or 1,4-bis(p-fluorobenzoyl)benzene (BP/CH/BF) and their thermotropic liquid crystalline properties were characterized by a variety of experimental techniques. The thermotropic liquid crystalline behavior was observed in the copolymers containing 50 and 70% biphenol. Melting transition (Tm) and isotropization transition (Ti) both appeared in the DSC thermograms. A banded texture was formed after shearing the sample in the liquid crystalline state. The novel poly(aryl ether ketone)s had relatively higher glass transition temperature (Tg) in the range of 168 similar to 200 degrees C and lower melting temperature (Tm) in the range of 290 similar to 340 degrees C. The thermal stability (Td) was in the range of 430 similar to 490 degrees C.

Synthesis and properties of poly(aryl ether ether ketone ketone) containing meta-phenyl links

A Series of poly(aryl ether ether ketone ketone) containing meta-phenyl link were synthesized, the general properties were studied by DSC, stretch, impact, etc.. The results indicated that with the raising of meta linkage monomer fractions, the glass transition point decreased, the melting temperature decreased at first, and then disappeared, but for all-meta-linked polymer, T-m appeared once more. And this kind of polymer had good stretch and impact resistance performance.

The crystal structure and drawing-induced polymorphism in poly(aryl ether ketone)s .1. Poly(oxybiphenyl-4-4'-diyloxy-1,4-phenylenecarbonyl-1,3-phenylenecarbonyl-1,4-phenylene)

Crystal structure and polymorphism induced by uniaxial drawing of a poly(aryl ether ketone) [PEDEKmK] prepared from 1,3-bis(4-fluorobenzoyl)benzene and biphenyl-4,4'-diol have been investigated by means of transmission electron microscopy (TEM), electron diffraction (ED), wide-angle X-ray diffraction (WAXD), and differential scanning calorimetry (DSC) techniques. The melting and recrystallization process in the temperature range of 250-260 degrees C, far below the next melting temperature (306 degrees C), was identified and found to be responsible for the remarkable changes in lamellar morphology. Based on WAXD and ED patterns, it was found that crystal structure of isotropic-crystalline PEDEKmK obtained under different crystallization conditions (melt-crystallization, cold-crystallization, solvent-induced crystallization, melting-recrystallization, and crystallization from solution) keeps the same mode of packing, i.e., a two-chain orthorhombic unit cell with the dimensions a = 0.784 nm, b = 0.600 nm, and c = 4.745 nm (form I). A second crystal modification (form II) can be induced by uniaxial drawing above the glass transition temperature, and always coexists with form I. This form also possesses an orthorhombic unit cell but with different dimensions, i.e., a = 0.470 nm, b = 1.054 nm, c = 5.064 nm. The 0.32 nm longer c-axis of form II as compared with form I is attributed to an overextended chain conformation due to the expansion of ether and ketone bridge bond angles during uniaxial drawing. The temperature dependence of WAXD patterns for the drawn PEDEKmK suggests that form II can be transformed into the more stable form I by relaxation of overextended chains and relief of internal stress at elevated temperature in absence of external tension.