Kinetics of silane grafting and moisture crosslinking of polyethylene and ethylene propylene rubber

Abstract

SYNOPSISPeroxide initiated graft copolymerization of vinyl trimethoxy silane ( VTMO ) and vinyl triethoxy silane (VTEO) onto polyethylene ( P E ) and ethylene propylene copolymer ( E P R ) was studied. The kinetics of grafting, studied by differential scanning calorimetry, are the same for all the systems and the activation energy for VTMO is 170 ? 4 KJ/mol. Activation energy for VTEO is 185 ? 5 KJ/mol. The VTMO and VTEO graft copolymers of PE and EPR were prepared by reactive processing in a Brabender extruder in the temperature range of 150-200°C. Moisture catalyzed crosslinking of the silane grafted copolymer was also studied. The influence of the structure of the catalyst, its concentration, moisture concentration, temperature, and time on degree and rate of crosslinking has been evaluated. Crosslinking reactions follow first order kinetics with respect to both catalyst and moisture concentration. Activation energy ( E , ) of the crosslinking reaction has been determined as 65 K J mol-' . The mechanism of grafting and crosslinking is discussed.

Thermal and Mechanical Properties of Vinyltrimethoxysilane (VTMOS) Crosslinked High Molecular Weight Polyethylene (HMWPE)

“…Although the energy of the Si-O-Si linkages is high, 779 kJ/mol, the introduction of crosslinks hardly affect the polyethylene thermal stability, especially in a nitrogen atmosphere 21 . Similar results have been found by others researchers 12,15 .…”

“…The crosslinking occurs through condensation reactions of these silanol groups, leading to the formation of siloxane bridges (-Si-O-Si-), which restricts the mobility of the polymeric chains. An organotin catalyst is generally employed [11][12][13][14][15][16][17][18][19][20][21][22][23][24][25][26] . This crosslinking process may be performed in one single step (Monosil process) or in two steps (Sioplas process) 11 .…”

Funcionalização do Polipropileno com Viniltrietoxisilano em Solução e no Estado Fundido

“…Entretanto, na literatura científica poucos trabalhos são encontrados, sendo que a maior parte dos mesmos visa à obtenção de poliolefinas reticuladas [30][31] . Os polímeros obtidos têm sido explorados comercialmente como isoladores de cabos elétricos e de dutos para água quente [32,33] .…”

Optical sensor for pH monitoring using a layer-by-layer deposition technique emphasizing enhanced stability and re-usability

“…There is a further report in the literature [18] which focused on the film stability under chlorine treatment as a means to improve the stability of the LbL-assembled nanofilteration membranes in combined high ionic strength conditions and under chlorine treatment. In another approach, the stabilizing of the thin film is achieved by forming siloxane bonds owing to a silane coupling reaction between oppositely charged polyelectrolytes which leads to the crosslinking between the silane groups [18,19]. Egawa et al demonstrated [20] crosslinking between the sulfonate group in the polyanion and the diazonium ion in polycation due to exposure to UV light.…”