Jen-Feng Kuo

Morphology and properties of nylon 6-polyoxypropylene-nylon 6 block copolymers

Abstract The morphology and mechanical properties of nylon 6-polyoxypropylene (POP)-nylon 6 block copolymers as functions of POP content were studied using infrared spectrophotometry, electron microscopy, X-ray diffraction, reheometric measurement and impact testing. The copolymers exhibit a unique morphology having spherulites with feather-like texture, containing POP-rich amorphous domains; the texture varies with POP content. The spherulite is presumed to consist of lamellae, nylon-rich amorphous domains between lamellae and POP-rich amorphous domains outside the interlamellar region. The crystal structure of the copolymers is mainly α-form with a relative shift of hydrogen-bonded sheets in the crystal unit cell. In the dynamic damping spectra, multiple transitions appear in the α-transition range of nylon 6. One is due to the conventional transition of nylon segments, another is due to POP-hydrogen bonded nylon segments. The impact strength is better than that of pure nylon 6 and increases with decrease of POP content. The area of indent zones in the fractured surface change in the same manner as the change of impact strength and POP domain size with POP content. The size and distribution of the POP-rich domains in the spherulites is suggested to be a governing factor for the morphology and properties of the nylon block copolymers.

Permeation of oxygen/nitrogen in cobalt-chelated copoly(EDTA-MMA-BA) membranes

EDTA-MMA-BA copolymer was prepared by radical polymerization in aqueous solution. EDTA, which chelated cobalt ions (Co2+), at the chain end of copolymer was as an oxyphilic carrier. Different cobalt ions contents of chelated copolymer membranes were prepared and shown good oxygen permeability (PO2=10×10−9 cc(STP)cm/cm2 s cmHg (100 barrer)) and highly permselectivity (α(O2/N2)=10) of oxygen/nitrogen. The separation factor increased with the increasing of Co2+ contents in copolymer membranes. Both the permeation behaviors and the change of pressure were in good agreement with Petropoulos [J.H. Petropoulos, J. Polym. Sci. A2 8 (1970) 1797], Paul and Koros’ [D.R. Paul, W.J. Koros, J. Polym. Sci.: Polym. Phys. Ed. 14 (1976) 675] modified dual-mode absorption theory. The relationship between the oxygen or nitrogen permeability and temperature follows the Arrhenius relation. The apparent diffusion activation energies of oxygen and nitrogen were estimated to be 7.4–11.4 and 12 kcal/mol, respectively.

Polymerization of styrene initiated by a novel initiator sodium formaldehyde sulfoxylate and sodium lauryl sulfate

Sodium formaldehyde sulfoxylate (SFS) along with sodium lauryl sulfate (SLS) was used as a novel initiator for aqueous polymerization of styrene (St) at 80°C. The rather stable emulsion lattices and a uniform size distribution of lattice particles were obtained. The polymerization behaviors and the qualities of the product were determined. The course of polymerization is similar to the traditional emulsion polymerization including three reaction periods: formation of the particle, a constant number of particles and a first-order reaction. The rate of polymerization almost does not depend upon the St concentration and depends on a 0.7-power on the concentrations of SFS and SLS. The aqueous solutions consisting of SFS, SLS and St at 80°C exhibited the free radical spectrum of electron paramagnetic resonance. The conductivity measurement showed that SLS does not exhibit the critical micelle concentration in the aqueous solution containing SFS. The polymerization is assumed to be a soap-free emulsion one. The polystyrene obtained showed a small Z-direction thermal expansion coefficient (431 μm m−1 (°C)−1), a very small specific refractive index increment (dn/dc=0.0664 ml g−1), a smaller second virial constant (A2=1.41×10−4 mol-cm3 g−2), and a high glass transition temperature (Tg=106°C) as well as a high film formation temperature (MFT = 120°C).

Study on the Properties of a Poly(hexamethylene adipamide) Film at the Air/Water Interface

Abstract A monolayer film of poly(hexamethylene adipamide) (nylon 66) was obtained by spreading N-trifluoroacetic anhydride (NTF)- modified nylon 66 in chloroform solution on an air-water interface at 14.7 °C. The pressure relaxation in a constant area and hysteresis of the film were measured. The surface moment versus surface area isotherm shows that the film holds the same conformation over the surface area region between 120 and 52.6 A 2 repeat-unit , and collapses at 52.6 A 2 repeat-unit . However, pressure relaxation at a constant surface area smaller than some transition value between 85 and 70 A 2 repeat-unit and significant hysteresis were observed. These phenomena were attributed to the effect of intermolecular interaction of hydrogen bonding. The mechanism of collapse was evaluated using the Avrami crystallization equation. Two-step crystallization was observed.