Ivan Vulic

Thermal catalytic depolymerization of polyamides

SummaryThe formation of cyclic diamides of polyamides 4,6 and 6,6 by thermal catalytic depolymerization of the corresponding polyamides was investigated. This method was optimized by changing external factors, like: concentration of catalyst; depolymerization temperature; — time; working under nitrogen flow and under a high vacuum (10-5 mbar). The catalyst sodium-2-ethylhexanoate was used to accelerate the reaction. The different multi-component depolymerization products were analyzed by reversed phase HPLC. The formation of cyclic diamides of polyamides 4,6 and 6,6 was 10, respectively 20 wt.-%, under optimum conditions, which is not sufficient to be used as feed stock for new (co)polyamides.

Synthesis, Structure, and Properties of Polymers Based on Pivalolactone

Abstract Since the introduction of poly(ethy1ene terephthalate) (PET) and polyamide 6, many attempts have been made to synthesize other polymers with a large variety of properties. One of the polymers which has been studied extensively is polypivalolactone (PPVL), formed by ring-opening polymerization of pivalolactone (PVL). PPVL is a highly crystalline aliphatic polyester (≥75% crystallinity) with mechanical properties comparable with those of PET and polyamide 6. Although the technology and expertise to prepare PPVL on a commercial scale was already available in the early 1970s, most of the projects concerning PPVL, especially in fiber applications, were discontinued on the basis of economic considerations.

Dissolution behaviour of thermotropic liquid-crystalline polyesters in 3,5-bis(trifluoromethyl)phenol and pentafluorophenol

Abstract Determining η sp c as a function of time has been used to investigate rates of dissolution and stabilities of solutions of liquid-crystalline polyesters (LCPs). The dissolution behaviour of commercial LCPs and prepolymers, post-condensates and pelletized LCPs prepared in-house has been studied in 3,5-bis(trifluoromethyl)phenol (BTFMP) and pentafluorophenol (PFPh). All of the investigated polyesters dissolved in both solvents. Optimum temperatures for dissolution appeared to be 25°C for BTFMP and 40°C for PFPh. Dissolution times ranged from 10 to 40 h. The solutions remained stable for at least 80 h. Dissolution of post-condensates is very difficult. Fortunately, by reducing the crystallinity, they dissolved more readily in both solvents without modifications of the molecular structure. Therefore, determining reliable molecular parameters of LCPs seems to be possible in these solvents.

The structure of 1,6-diazacyclododecane-7,12-dione, a cyclic monomeric model of polyamide 46

Abstract1,6-Diazacyclododecane-7,12-dione (C10H18N2O2),Mr=198.27, monoclinic, one molecule in the asymmetric unit,P21/c;a=9.802(4),b=12.966(6),c=9.20(1) Å,V=1083(1) Å3,Z=4,Dx=1.215(2) Mg·m−3, λ(CuKα)=1.54184 Å,μ=6.5 cm−1,F(000)=432,R=0.062 for all 866 unique observed reflection data. The molecules form hydrogen bonded stacks with two hydrogen bonds between each pair of succeeding molecules. The stacks consist of molecules with two alternating orientations, as in A-B-A-B. No strong intermolecular contacts exist between adjacent stacks, this results in a partial two-fold positional disorder of the stacks in the direction of thea-axis: two adjacent stacks can slide over half a unit cell along thea-axis without severely affecting the packing. This disorder results in very broad reflectionsh≠2n, which could only be discerned on a rotation photograph. The 12-membered ring which forms the basis of the structure has a pseudo two-fold axis through the bonds C(8)-C(10) and C(9)-C(11).

Mechanical properties and chemical stability of pivalolactone-based poly(ether ester)s

The processing, mechanical and chemical properties of poly(ether ester)s, prepared from pivalolactone (PVL), 1,4-butanediol (4G) and dimethyl terephthalate (DMT), were studied. The poly(ether ester)s could easily be processed by injection moulding, owing to their favourable rheological and thermal properties. The tensile response of a poly(ether ester) with a butylene terephthalate (4GT) content of 72 mol%, which exhibited the phenomena of necking and strain-hardening, was related to the morphology of these copolymers. The influence of the short 4G-PVL segments was reflected in a high Youngs modulus and yield stress, and resulted in a tough behaviour for the poly(ether ester), with an ultimate elongation of 500%. The poly(ether ester)s were stable towards treatment at room temperature with water or weakly acidic or alkaline solutions. Conditioning at 90°C in water for 264 h resulted in a water uptake of 1 wt%, whereas the rate of hydrolysis was 0.0003 (expressed in An rel h-1) for the poly(ether ester) with a 4GT content of 72 mol%. Although a decay in the mechanical properties for the PVL-based poly(ether ester) after exposure to water at 90°C was observed, these materials were assumed to have a higher hydrolytical stability than other poly(ether ester)s

The (Co)Polymerization of the Cyclic Diamide 1,6-Diazacyclododecane-7,12-Dione

Abstract It is demonstrated for the first time that the cyclic diamide 1,6- diazacyclododecane-7,12-dione (c-4) can be polymerized. Polyamide 46 was prepared by thermal or hydrolytic ring-opening polymerization of c-4. c-4 polymerized in the melt to form polyamide 46, containing approximately one-third of the original c-4. Due to possible degradation of c-4 near its melting point, the polyamide 46 formed possibly contained a crosslinked fraction which was insoluble. Therefore, the thermal behavior deviated from that of Stanyl (a commercial polyamide 46 from DSM, The Netherlands). Furthermore, polyamide 46 was prepared by anionic polymerization of c-4 in N-methyl-2-pyrrolidone solution at 202°C. c-4 polymerized with NaH and 1,6-hexamethylene diisocyanate as catalysts. Almost all c-4 was converted to polyamide 46. Due to possible crosslinking, the polyamides had difficulties in dissolving. Furthermore, the thermal behavior of this low molecular-weight polyamide 46 deviated from that of Stanyl, but solid-sta...