Crosslinked EVA

Crosslinked EVAs are more resistant to creep but loading must still be low. 

MPR (Melt Processable Rubber), a blend of vinylidene chloride and crosslinked EVA,... 

Details are given of the E266-4 injection press developed by Main Gronp for the production of shoe soles from EVA and crosslinked EVA foams. 

Toronto, 27th April-2nd May 1997, p.2060-4. 012 MICROCELLULAR CROSSLINKED EVA FOAM BY INJECTION MOULDING PROCESS LeeJJ... 

The injection moulding process for producing a microcellular crosslinked EVA has several advantages over the conventional compression moulding process reduced cycle time, labour and scrap. The presence of skin adds aesthetic value and ability to engrave logos in one step. However, the injection moulding process has... 

BXL Plastics ERP division is introducing two new grades of antistatic and conductive foams at this years Intemepcon exhibition at the Birmingham NEC in the UK in March 1988. Brief details are given on conductive closed-cell crosslinked EVA copolymer foam, Evazote C, and antistatic PE foam Plastazote AS, both used for electronics packaging. 

EVA reins can be conveniently crosslinked by both peroxide or irradiation to enhance the mechanical properties and the heat resistance. It is the crosslinking, coupled with the inherent rubbery nature of the polymer, which makes EVA suitable for production of tough and abrasion resistant foams, especially suitable for footwear applications. Crosslinked EVA foams can be manufactured by two methods (8) ... 

AZBN, in contrast to various peroxides, to crosslink EVA copolymers radically, which means that the formation of radicals at the macromolecules does not take place to a sufficient extent. 

The aim of this work is to analyze the changes in the relevant thermal behavior of the crosslinked EVA encapsulant material due to outdoor exposure in Mediterranean climate by TSC and DSC thermal analysis. The changes in thermal properties should be discussed and special interest will be focused on the specific TSC relaxation parameters like activation energy and relaxation frequency determination by using the initial rise method. 

Original EVA film submitted to the cure step cycle is referred to as cured or crosslinked EVA. The gel content can be determined by a solvent (toluene) extraction method as a standard procedure described by STR. The gel content measurement during the cure cycle, is 87.4 % according to STR procedure. 

In order to investigate the viscoelastic behavior of crosslinked EVA, rheological measurements were made to determine at what temperatures the phase transitions occur and their effect on the dynamic mechanical modulus. The complex dynamic modulus E expression is given by Eq. (6). 

Thermo-mechanical properties of the crosslinked EVA were measured using a Rheometric DMTA IV in a nitrogen atmosphere. Crosslinked EVA specimens were cut from the samples and mounted in the rectangular tension fixture. The typical sample dimensions were 10 mm long, 3.3 mm wide and 0.4 mm thick. During the dynamic temperamre ramp experiment, the heating rate was 7 °C/min and the frequency was 1 Hz. The static force was maintained at 20 % higher than the dynamic force. 

Fig. 10 TSDC spectra of unaged and aged crosslinked EVA under polarization temperature of 60 °C at CDER site...

Results concerning permittivity of EVA before and after exposure are illustrated in Figs. 14 and 15 respectively. As shown, permittivity of EVA is a non-linear function of temperature and it decreases with increasing liequency. The plot of dissipator factor versus temperature at various frequency before and after exposure as represented in Figs. 16 and 17 respectively, shows that EVA exhibits relaxation phenomenon. It is found that the relaxation behavior changes with frequency. At frequency of 1 Hz the glass transition temperature of the crosslinked EVA is found... 

Fig. 18 DSC curves of the crosslinked EVA before and after exposure at CDER site...

Fig. 20 DSC curves of the crosslinked EVA aged for 18 months at CDER site in heat-cool-heat mode with expanded heating cycles...

The activation energy of the crosslinked EVA before and after exposure is calculated to be 52.8 and 162.2 kJ/mol respectively according to Fig. 25. After exposure in desert climate, the activation energy of EVA is very high due to environment weathering and time exposure duration. 

FTIR spectmm in ATR mode of the crosslinked EVA before and after exposure is illustrated in Fig. 27. It is noted several peaks related to different modes of vibration of the bonds. The crosslinked EVA has two peaks due to CH bond located at 2847 and 2921 cm . An important peak appears at 1736 cm corresponding to the harmonic vibration of C=0 (carbonyl group). At 1372 cm an intense peak appears, corresponding to the vibration of the CH3 bond. The vibration of the ester bond C-O-C function appears at 1247 cm [26, 27]. After exposure in the natural environment the FTIR spectra of the crosslinked EVA has a relatively broad peak between 3402 and 3323 cm, which corresponds to the vibration of the hydroxyl group (OH) due to the effect of moisture in natural exposme. Nevertheless, other... 

Agroui, K., Collins, G., Earenc, J. Measurement of glass transition temperature of crosslinked EVA encapsulant by thermal analysis for photovoltaic application. Renew. Energy 43, 218-223 (2012)... 

Table 6.2 A comparison of the flame retardant performance of aluminium hydroxide (ATH) and MCS [125 phr in crosslinked EVA] ...

Herbert has carried out a comprehensive study of the effect of ATH on the fire resistance of a peroxide crosslinked EVA (18% vinyl acetate), using the cone calorimeter [34]. This work showed that ATH was an effective fire retardant in this test, with significant reductions in most parameters, notably reduced peak heat release rate and smoke level. 

Herbert has reported on the effect of ATH in a peroxide crosslinked EVA [34]. Using the cone calorimeter with an irradiation of 35 kW/m, the ATH was found to give much lower smoke levels than calcium carbonate and aluminium oxide fillers. 

Some characteristics of borates are given in Table 2. FIREBRAKE ZB has been used as a fire retardant in PO wire and cables as well as electrical parts. It improves elongation properties of PO, crosslinked EVA-electrical parts, etc. [22]. 

Shoe soles (formed and crosslinked EVA, PE) Rotational molding (PE, EVA) ... 

Before the advent of suitably flame-retardant crosslinked EVA insulation compounds, peroxide and radiation-crosslinked blends of PVC/VA solution copolymers and EVA were used for switchboard wire and related applications. These compounds routinely passed 90°C long-term wet electrical testing and 7-day heat aging at 150 °C. This is an approach that might be reconsidered. 

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