Equilibrium melting temperatures and crystallization parameters of polyamide 6/polyurethane blends were investigated. Thermal
properties of the crystalline phase of blends obtained from polyamide 6 and polyurethane containing 40 wt% of hard segments,
are only limited influenced by the overall blend compositon. Because from separate measurements single glass transitions for
all samples were estimated, so in the investigated case the blending process may occur mainly between amorphous fraction of
polyamide 6 and the polyurethane or, what is more probable, the polyurethane phase is dispersed in the continuous polyamide
matrix, although some interactions exist.
Authors:B. Youssef, B. Mortaigne, M. Soulard, and J. Saiter
In this work, we have studied the degradation processes of polyurethane containing phosphonate groups used as a fireproofing
agent. These studies are undertaken by simultaneous thermogravimetry (TG) and differential scanning calorimetry (DSC) measurements.
It is found that fireproofing agents with phosphonate react with oxygen in the air and prevent the complete combustion of
the material. It is also found that the energy released during combustion is low when comparison is performed with other fireproofing
Authors:J. Ledru, J. Saiter, J. Grenet, B. Youssef, F. Burel, and C. Bunel
Polyurethane acrylate resins cured by two different ways, a thermal way and a photochemical way, are investigated by means of differential scanning calorimetry (DSC) and thermally stimulated depolarization currents (TSDC). Even if both curing methods lead to the same material from a chemical point of view, we show that important differences exist between the thermocured resin and the photocured resin in terms of molecular relaxation behaviour.
A thermodynamic analysis of the uniaxial stretching of polyurethanes of various compositions and mechanical histories was carried out by using deformation calorimetry. The initial small strain deformations were found to result from the volume elasticity of the hard phase. The intramolecular energy contributions of the soft blocks were estimated. The hard block contributions were shown to depend on their content and on the degree of sample stretching. The predominant role of the soft component is proved to be manifested only in softened samples with a hard block content not exceeding 30%. The thermodynamics of the softening and hysteresis phenomena were studied. The dependence of the deformation mechanism on the hard block content and mechanical history is discussed.
Blends of poly(vinyl chloride) and a polyurethane elastomer were investigated by DSC and tensile testing. Up to 30 wt% single
glass transition was found. It was concluded that the polyurethane forms partly a true blend and is partly disperged in the
continuous blend phase.
In this work thermal
transitions and thermal stability of polyurethane intermediates and polyurethanes
were investigated. The intermediates were obtained by glycolysis of waste
polyurethane (PUR) in the reaction with hexamethylene glycol (HDO). The excess
of HDO was not separated from the product after the glycolysis process was
finished. The effects of different mass ratio of HDO to PUR foam on selected
physicochemical properties (hydroxyl number, Brookfield viscosity and density)
were also determined.
The polyurethanes were synthesized from
the obtained intermediates by the prepolymer method using diisocyanate (MDI)
and glycolysis product of molecular mass in range 700/1000 g mol–1.
Hexamethylene glycol, 1,4-butanediol and ethylene glycol were used as chain
extender agents. Influence of NCO groups concentration in prepolymer on glass
transition temperature (Tg)
and storage and loss modulus (E’, E’’) of polyurethanes were investigated
by the DMTA method. Thermal decomposition of obtained glycolysates and polyurethanes
was followed by thermogravimetry coupled with Fourier transform infrared spectroscopy.
Main products of thermal decomposition were identified.
Authors:Cheila Mothé, Carla de Araujo, and Shui Wang
Polyurethane composites reinforced with curaua fiber at 5, 10 and 20% mass/mass proportions were prepared by using the conventional
melt-mixing method. The influence of curaua fibers on the thermal behavior and polymer cohesiveness in polyurethane matrix
was evaluated by dynamic mechanical thermal analysis (DMTA) and by differential scanning calorimetry (DSC). This specific
interaction between the fibers and the hard segment domain was influenced by the behavior of the storage modulus E′ and the loss modulus E″ curves. The polyurethane PU80 is much stiffer and resistant than the other composites at low temperatures up to 70°C. All
samples were thermoplastic and presented a rubbery plateau over a wide temperature range above the glass transition temperature
and a thermoplastic flow around 170°C.
Summary A series of semi-interpenetrating polymer networks (semi-IPN) of polyurethane (PU) and poly(vinyl chloride) (PVC) has been obtained by prepolymer method and characterised by FTIR; morphological features were examined by SEM-EDS. It has been found that PVC spherical aggregates are dispersed in the PU matrix, but Cl atoms location indicates partial miscibility of both polymers at the interphase which is probably due to hydrogen bonding and/or dipole-dipole interactions. The PVC component influences the phase behaviour of PU’s hard segments, as evidenced by DSC results. Thermogravimetric analysis (TG) reveals a complex, multi-step decomposition process with the main mass loss at 503-693 K, while the DTG maxima are located between 540 and 602 K.
Authors:C. Rotival, E. Renacco, C. Arfi, A. Pauli, and J. Pastor
The thermal decomposition of a polypropylene film, a polyurethane adhesive, as well as a polypropylene coated with a polyurethane
adhesive have been studied by a thermogravimetric (TG) analysis, at a heating rate of 5°C a minute with air flow. During the
thermal analysis different decomposition steps which correspond to different weight loss rates were obtained on thermal curves.
Gases were collected between the different decomposition steps and then analyzed. The results reported deal with the conversion
of carbon into oxides and aldehydes—ketones, and also with that of nitrogen into hydrogen cyanide and isocyanates. The findings
lead to a better understanding of the hazards and risks of toxic emissions that may be generated by the gas formation following
heating of these materials.
New polyurethanes with mesogenic units in the main chain due to the use of a liquid crystalline chain extender were synthesized
from 4,4'-methylenebis(cyclohexyl isocyanate) (HMDI)using diisocyanates of different trans, trans isomer content, a low molecular diol4,4'-bis(6-hydroxyhexoxy)biphenyl (BHHBP) and a high molecular poly(hexyleneadipate)diol
(PHA). The growth of trans, trans isomer content in HMDI used to syntheses of PU induces monotonic growth of melting point, rectilinear growth of crystallization
temperatures and the growth of crystallization enthalpy, both for hard segment polyurethanes and block polyurethanes. The
increase of trans, trans isomer content in HMDI increases also glass transition temperatures and dynamic storage modulus of the polyurethanes.