Search results for "MELT"

THERMOTROPIC HOMOPOLYESTERS. IV. STUDY OF FIBER FORMATION.

1983

We report a melt spinning and viscosity study of two semiflexible homopolyesters containing both rigid and flexible segments in the repeating unit. Single filaments of the polyesters formed from 4,4′-diacetoxybiphenyl and azelaic acid (PB7) and sebacic acid (PB8), and from 4′-hydroxyphenyl-4-hydroxycinnamate and azelaic acid (C7), were spun at temperatures between 205 and 255°C. The temperature dependence of the Newtonian melt viscosity of PB7 and C7 was investigated, and a range of molecular weights was studied for PB7. The spinning parameters, fiber characteristics, and viscosity-temperature behavior are related to the type of mesophase formed. The mechanical properties of fibers spun fro…

Testing of a constitutive equation for entangled networks by elongational and shear data of polymer melts

1973

An entangled network such as a polymer melt or a concentrated solution is here described by a set of two simultaneous equations. One of them is a balance of entanglements, the other gives the stress in the classical form of aMaxwell equation.

The non-isothermal rheological behaviour of molten polymers: Shear and elongational stress growth of polyisobutylene under heating

1981

Data of stress growth under both shear and elongational kinematics have been taken in presence of heating temperature ramps on a commerical polyisobutylene.

Crystallization kinetics of LDPE/Ny6 blends

1988

The crystallization behaviour of low density polyethylene/nylon 6 blends has been investigated as a function of the composition. The melting points of the polymers are almost uninfluenced by the presence of the other homopolymers except for blends with a nylon content of 75–90%. Blends with 10% nylon content do not exhibit the crystallization peak during the cooling step probably because of the low concentration and high viscosity of the low density polyethylene matrix. The crystallinity degree of the polyethylene is independent of the composition, while some variations are shown by the polyamide. Finally the rate of nucleation is strongly affected by the composition, in particular for the …

Thallium geochemistry in the metamorphic Lengenbach sulfide deposit, Switzerland: Thallium-isotope fractionation in a sulfide melt

2014

The Lengenbach (Switzerland) Pb-As-Tl-Zn deposit was formed from a sulfide melt at about 500 °C during Alpine metamorphism, but details on its formation and especially the source of the metals are still under debate. In this study we present two sample sets to address these questions: 1. MC-ICP-MS analyses of thallium isotopes in sulfides, sulfosalts, and melt inclusions from the Alpine metamorphic Lengenbach deposit in the Binn Valley of Switzerland, the non-metamorphic Wiesloch Mississippi Valley-type deposit in Southern Germany, and the Cu- and As-rich mineralization at Pizzo Cervandone about 2 km SW of the Lengenbach deposit, which has been discussed as potential source of the Lengenbac…

Anti-/Pro-Oxidant Behavior of Naturally Occurring Molecules in Polymers and Biopolymers: A Brief Review

2019

Polymers and biopolymers are continuously subjected to the action of different stress factors, such as oxygen, heat, UV light, mechanical stress, humidity, etc., during their processing and service life, undergoing overall oxidative degradation, that causes performance and property deterioration. To improve the resistance at high temperatures and long-term weatherability of the polymers and biopolymers, usually, during their manufacturing, synthetic antioxidants and UV-light stabilizers are added. In the past decade, several concerns related to the impact of the synthetic stabilizers have emerged, and to reduce their negative effect on human health and the environment, their replacement wit…

A kinetic study of the formation of smectic phases in novel liquid crystal ionogens

2013

[EN] A multi-rate non-isothermal kinetic analysis of the isotropic-melt to liquid crystalline phase transition of novel liquid crystalline ionogenic copolymers, LCIs, the 10-(4-methoxyazobenzene-4'-oxy)decyl methacrylate]-co-2-(acrylamido-2-methyl-1-propanesulfonic acid)s, 10-MeOAzB/AMPS, copolymers, has been performed by means of calorimetric experiments. An analytical methodology which includes the study of the phase transition rate parameter, the determination of the activation energies by using Kissinger and Flynn-Wall-Ozawa models, and the study of the phase transition kinetics by the use of the Avrami theory, has been applied. The formation of the mesophases from the isotropic state o…

Publisher’s Note: “Polymer-specific effects of bulk relaxation and stringlike correlated motion in the dynamics of a supercooled polymer melt” [J. Ch…

2004

a! Present address: Department of Physics, Wesleyan University, Middletown, CT 06459. b!Author to whom correspondence should be addressed. Electronic mail: baschnag@ics.u-strasbg.fr c!Author to whom correspondence should be addressed. Electronic mail: sglotzer@umich.edu FIG. 8. Temperature dependence of the ratio of ^sseg(tstr )& and ^s(tstr )&. tstr max is the peak time of ^sseg& and ^s& at different temperatures. TMCT 50.45. JOURNAL OF CHEMICAL PHYSICS VOLUME 120, NUMBER 14 8 APRIL 2004

1989

A series of combined main-chain side-group liquid-crystalline polymers was synthesized by melt polycondensation from trans-1,4-cyclohexanedicarboxylic acid, chloro-1,4-phenylene diacetate and 6-(4-methoxy-4′-biphenylyloxy)hexyl-1,4-phenylene diacetate. These polyesters combine the features of rigid-rod main-chain LC-polymers and of side-group LC-polymers. Polymers with small fractions of mesogenic side-groups (5 and 10 mol-%) have lower melting points than the parent polymer poly(chloro-1,4-phenylene 1,4-cyclohexanedicarboxylate) but are still liquid crystalline up to their decomposition at T ≥ 400°C. In polymers with larger fractions of mesogenic side-groups (50 and 100 mol-%) partial isom…

Melt stabilization of wet polyamide 6

2002

Abstract Melt processing of polycondensate polymers must be carried out after careful drying in order to avoid any hydrolytic chain scission caused by the presence of water or other small molecules. In this work, the effect of two different antioxidants on the processing and flow properties of a polyamide 6 sample not dried before processing operations has been studied. One of these stabilizers seems to protect the wet polymer from hydrolytic chain scission. This action has been interpreted considering that the stabilizer hydrolyses instead of the polyamide macromolecules.