Search results for "Thermal"

A new equipment to measure the combined effect of humidity, temperature, mechanical stress and UV exposure on the creep behaviour of polymers

2008

To be able to study and predict the physical properties of a polymeric material under different environmental conditions is very important. Moisture, UV irradiation, thermal and mechanical stresses can dramatically change the characteristics of the material and hinder some specific applications. In this work, a new equipment able to perform creep tests under different environmental conditions (temperature, humidity, stress) is presented. Some preliminary results are also presented using a sample of polyamide 6. As this polymer is sensitive to all these variables, it is appropriate to verify the effectiveness of the new instrument.

Synthesis, optical, and thermal properties of glassy trityl group containing luminescent derivatives of 2-tert-butyl-6-methyl-4H-pyran-4-one

2012

In this work we present simple preparation of original trityl group containing glassy luminescent 6-styryl substituted derivatives of 2-(2-tert-butyl-4H-pyran-4-ylidene)malononitrile (DWK-1TB), 2-(2-tert-butyl-4H-pyran-4-ylidene)-2- ethyl-2-cyanoacetate (KWK-1TB), 2-(2-tert-butyl-4H-pyran-4-ylidene)-1H-indene-1,3(2H)-dione (ZWK-1TB) and 5-(2-tert-butyl-4H-pyran-4-ylidene)pyrimidine-2,4,6(1H,3H,5H)-trione (JWK-1TB). Their optical properties have been investigated. The absorption maxima of synthesized glasses is in region from 425 nm to 515 nm and emission maxima is from 470 nm to 625 nm in solution of dichloromethane. But absorption maxima of their solid films is from 425 nm to 500 nm and em…

1986

In order to graft methacrylonitrile onto preformed networks containing thermolabile azo groups, the monomer was used to swell the networks and then the temperature raised to the decomposition temperature for the azo groups. The unusually high grafting efficiencies yields (e) achieved are explained in terms of both the differences in the reactivities of the primary radicals formed and side reactions, which lead to additional grafting sites. As an aid to understand the dependence of monomer conversion on that of the initiator a kinetic model is discussed, which involves the consideration of the polymerization taking place both in the homogeneous phase and within the polymer pearls, which can …

Thermal and optical properties of 4H-pyran-4-ylidene fragment and bis-styryl and triphenyl groups containing derivatives

2014

Small D-π-A type organic molecules with incorporated 4H-pyan-4-ylidene (pyranylidene) fragment in their structures show potential in organic photonics - such as materials for organic light emitting diode application studies and organic solid state lasers. Additional incorporation of bulky triphenyl- groups in their structures gives them the ability to form thin amorphous solid films from volatile non-polar organic solvents. Unfortunately, there is still no clear relation between compound organic structures and their thermal and optical properties. In order to investigate the above mentioned regularities we have synthesized a series of tripheyl- group containing derivates of 2,6-bis-styryl-4…

Polymere acroleine, I. Mitt. Untersuchungen über die polymerisation des acroleins.

1955

Unter der Einwirkung typischer Polymerisations-Katalysatoren wie z. B. Azoisobuttersaurenitril, Peroxyde, Redox-Systeme, metallorganische Verbindungen und Friedel-Crafts-Katalysatoren geht Acrolein in polymere Produkte uber. Deren physikalische Eigenschaften (thermische Bestandigkeit, Viskositat der Losungen u. a.) hangen von den Polymerisationsbedingungen ab. Einige der erhaltenen polymeren Produkte unterscheiden sich deutlich von den bisher bekannten Polyacroleinen. By the action of typical catalysts of polymerisation (e.g. azo-bis-isobutyronitrile, peroxides, redox-systems, organometallic compounds, Friedel-Crafts-catalysts) acrolein forms polymeric products. The physical properties of s…

Cyclopolymerisation einiger glutardialdehyde. Struktur der polymeren

1962

Die loslichen Spontanpolymerisate des Glutardialdehyds, β-Methyl- und β-Phenylglutardialdehyds bestehen auf Grund ihrer Eigenschaften und IR-Spektren vornehmlich aus Tetrahydropyranstruktureinheiten, die durch eine Cyclopolymerisation gebildet werden. Es wird ein infrarotspektroskopischer Vergleich mit verschiedenen niedermolekularen Tetrahydropyran-Modellsubstanzen durchgefuhrt. Die unkatalysierte Polymerisation last sich infrarotspektroskopisch verfolgen. Die Poly-glutardialdehyde konnen acetyliert werden. Die Polymeren erfahren durch die Acetylierung eine wesentliche thermische Stabilisierung. Die Eigenschaften und IR-Spektren der Spontanpolymerisate werden mit denen des vernetzten Poly-…

Mass spectrometric investigation of polymers: Thermal degradation of truxillic and truxinic polyamides

1975

The thermal degradation mechanism of four isomeric truxillic and truxinic polyamides were investigated by direct pyrolysis in the ion source of a mass spectrometer. Thermal degradation reactions were followed directly by this method by detecting the thermal and electron impact-induced fragments. The results obtained have shown that the thermal degradation products are sensibly different for the head-to-head (hh) and head-to-tail (ht) polymers and that the predominant pyrolytic process is the cyclobutane ring cleavage. In the hh isomers, both symmetrical and asymmetrical cyclobutane ring cleavage was detected, while in the ht isomers only symmetrical cleavage occurs; this explains the notice…

Phase selective synthesis of ZnS nanoparticles from structurally new dithiocarbamate precursor

2015

Abstract A phase selective solvothermal synthesis of ZnS (wurzite) nanoparticles with a flower-like morphology using a dithiocarbamate precursor, [Zn(4-dpmpzdtc)2(dpmpz)] (1) (where, dpmpz=(diphenylmethyl)piperazine), is described. The nanoparticles were identified as ZnS (wurzite) with the particle size of about 3 to 10 nm by scanning and transmission electron microscopy as well as powder X-ray diffraction (XRD). In addition, the precursor complex 1 was characterized using single crystal X-ray diffraction.

Binding abilities of new cyclodextrin-cucurbituril supramolecular hosts

2015

Various combined techniques (UV–vis spectrophotometry, isothermal titration calorimetry, thermogravimetry, ESI-MS mass spectrometry, polarimetry and 1H NMR spectroscopy) were used in order to study the interaction between a new combined supramolecular host, namely a bow-tie-structured cyclodextrin–cucurbituril association solely held by non-covalent interactions, and a suitably selected guest, namely the N-(p-nitrophenyl)-1,8-diaminooctane hydrochloride. In particular, the use of different techniques highlighted the peculiar features of the possible host–guest supramolecular interactions under different concentration conditions.

Recognition of Viologen Derivatives in Water by N-Alkyl Ammonium Resorcinarene Chlorides

2017

Three water-soluble N-alkyl ammonium resorcinarene chlorides decorated with terminal hydroxyl groups at the lower rims were synthesized and characterized. The receptors were decorated at the upper rim with either terminal hydroxyl, rigid cyclohexyl, or flexible benzyl groups. The binding affinities of these receptors toward three viologen derivatives, two of which possess an acetylmethyl group attached to one of the pyridine nitrogens, in water were investigated via 1H NMR spectroscopy, fluorescence spectroscopy, and isothermal titration calorimetry (ITC). ITC quantification of the binding process gave association constants of up to 103 M–1. Analyses reveal a spontaneous binding process whi…