Glass Transition Temperature Of Elastomer Research Articles

Influence of Network Structure on Glass Transition Temperature of Elastomers.

It is generally believed that only intermolecular, elastically-effective crosslinks influence elastomer properties. The role of the intramolecular modifications of the polymer chains is marginalized. The aim of our study was the characterization of the structural parameters of cured elastomers, and determination of their influence on the behavior of the polymer network. For this purpose, styrene-butadiene rubbers (SBR), cured with various curatives, such as DCP, TMTD, TBzTD, Vulcuren®, DPG/S8, CBS/S8, MBTS/S8 and ZDT/S8, were investigated. In every series of samples a broad range of crosslink density was obtained, in addition to diverse crosslink structures, as determined by equilibrium swelling and thiol-amine analysis. Differential scanning calorimetry (DSC) and dynamic mechanical analysis (DMA) were used to study the glass transition process, and positron annihilation lifetime spectroscopy (PALS) to investigate the size of the free volumes. For all samples, the values of the glass transition temperature (Tg) increased with a rise in crosslink density. At the same time, the free volume size proportionally decreased. The changes in Tg and free volume size show significant differences between the series crosslinked with various curatives. These variations are explained on the basis of the curatives’ structure effect. Furthermore, basic structure-property relationships are provided. They enable the prediction of the effect of curatives on the structural parameters of the network, and some of the resulting properties. It is proved that the applied techniques—DSC, DMA, and PALS—can serve to provide information about the modifications to the polymer chains. Moreover, on the basis of the obtained results and considering the diversified curatives available nowadays, the usability of “part per hundred rubber” (phr) unit is questioned.

Modelowanie charakterystyki przy sciskaniu oraz wlasciwosci uzytkowe hiperelastycznych materialow poliuretanowych stosowanych w budowie maszyn

The materials showing great reversible deformations (hyperelastic ones) namely non-compressible elastomers and compressible polyurethane foams were subjects of investigations. The behavior of these materials at compression has been modeled. Polynomial models were used for the description of elastomers while Ogden's models of various orders were applied to describe the foams. Calculations results were verified experimentally (Fig. 1-4). Additionally, several functional properties of the materials were evaluated from the point of view of their applications: elastomers differing in ratios of rigid (S) and elastic (G) segments (S/G=0.25, 0.5 or 0.75) as shimmy dumpers (Fig. 5-7, Table 1 and 2) and soft foams applied for car seats' construction (Fig. 8 and 9). The characteristics of materials consisted of glass transition temperature of elastomers (important when applied at low temperature), their resilience, hardness and abrasive wear as well as, for soft foams, also compression modulus and damping capacity.

New side‐chain nematic liquid crystalline elastomers containing smectic crosslinking units

AbstractA series of siloxane‐based liquid crystalline elastomers containing the smectic crosslinking agent M‐1 and nematic monomer M‐2 were synthesized by a one‐step hydrosilication reaction. The chemical structures of the monomers and polymers obtained were confirmed by FTIR spectroscopy. The mesomorphic properties and phase behavior were investigated by differential scanning calorimetry (DSC), polarizing optical microscopy (POM), and X‐ray diffraction (XRD) measurements. The influence of the crosslinking unit on the phase behavior was discussed. The experimental results demonstrated that the glass transition temperatures of elastomers had no remarkable change, and isotropization temperatures decrease with increasing the content of the crosslinking agent M‐1. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 3755–3760, 2004

Wlasciwosci karboksylowanego kauczuku butadienowo-akrylonitrylowego zawierajacego in situ zsyntetyzowane napelniacze krzemionkowe

From silica precursors we synthesized silica fillers in sol-gel reaction in the carboxylated acrylonitrile/butadiene rubber (XNBR). N-2-aminoethyl-3-aminopropyl-trimethoxysilane (DAMS) and tetraethoxysilane (TEOS) were used as fillers' precursors. It has been found that DAMS is a substance crosslinking XNBR. The network points are silsesquioxanes' domains containing amide as well as ionic bonds. Some part of points (∼30%) decompose under ethylenediamine treatment. The bigger DAMS content the bigger crosslinking density of elastomer as well as the stress at suitable elongation and tensile strength (Tables 2 and 4). The dynamic properties measurements show that organosilica compounds do not influence glass transition temperature of elastomer (Table 6) but in the range of 30-40°C the second maximum appears which is a transition connected to ionic aggregates activity. Addition of a mixture of DAMS + TEOS to the elastomer causes the increase of crosslinking of silsesquioxanes' domains and the filler shows tendency to creation of its own structure (Fig. 2). 2 9 Si NMR results show that mostly trifunctional structures Q 3 are obtained for equal ratio of silanes (1:1) but tetrafunctional structures Q 4 are also present (Table 1). The increasing of tetrafunctional structure Q 4 content, that is a synthesis of a filler with DAMS + TEOS mixture, leads to the increase of stress at suitable elongation, and tensile strength (Table 5).

A simplified method for determining the glass transition temperature of elastomers

A simplified method for determining the glass transition temperature of elastomers