摘要:
New fluoroelastomers are described, comprising monomeric units deriving from a bis-olefin having general formula: ##STR1## wherein: R.sub.1, R.sub.2, R.sub.3, R.sub.4, R.sub.5, R.sub.6, equal or different from each other, are H or alkyls C.sub.1 -C.sub.5 ; Z is an alkylene or cycloalkylene radical C.sub.1 -C.sub.18, linear or branched, optionally containing oxygen atoms, preferably at least partially fluorinated, or a (per)fluoropolyoxyalkylene radical.Such products are endowed with improved processability, especially during calendering of the vulcanization mixture, along with superior mechanical and workability properties during extrusion and injection molding, with a very good mold release.
摘要:
A polyvinylidenefluoride (PVDF) having high mechanical properties both at room temperature and at high temperatures, having very good processability and high thermochemical resistance to dehydrofluorination, is prepared by means of a polymerization process of vinylidenefluoride in aqueous emulsion at a temperature comprised between 95.degree. and 120.degree. C., in the presence of a chain transfer agent. In this way it is possible to obtain, using non-hazardous peroxidic initiators (for instance diterbutylperoxide), a PVDF particularly suitable for applications where high mechanical and thermochemical resistance properties are required, such as for instance the manufacture of articles for chemical industry (pipes, valves, fittings, tanks, heat exchangers, membranes, flanges, etc.).
摘要:
Fluoroelastomeric copolymers exhibiting high resistance to bases and alcohols, as well as high mechanical properties and low-temperature resistance, comprising, in moles:4-75% of units of vinylidene fluoride;12-40% of units of hexafluoropropene and/or perfluorovinylether and/or hydropentafluoropropene and/or chlorotrifluoroethylene;2-35% of units of an olefin containing up to 4 carbon atoms;2-60% of units of tetrafluoroethylene, provided that, when the sum of the olefin units and the perfluorovinylether units is equal to or greater than 70%, such copolymers possess a molecular weight sufficiently high to exhibit good mechanical characteristics.
摘要:
New fluoroelastomers are described, having iodine atoms in terminal position and monomeric units in the chain deriving from an iodinated olefin of formula: CHR═CH—Z—CH2CHR—I (I) wherein: R is —H or —CH3; Z is a (per)fluoroalkylene radical C1-C18, linear or branched, optionally containing one or more ether oxygen atoms, or a (per)fluoropolyoxyalkylene radical. These products, upon peroxide curing, require extremely short post-curing treatments (around 30-60 minutes at 180°-230° C.) and are characterized by compression set values lower than 25% (measured on O-rings at 200° C. for 70 hours according to ASTM Standard D395 Method B).
摘要:
New fluoroelastomers are described, having iodine atoms in terminal position and monomeric units in the chain deriving from an iodinated olefin of formula: CHR.dbd.CH--Z--CH.sub.2 CHR--I (I) wherein: R is --H or --CH.sub.3 ; Z is a (per)fluoroalkylene radical C.sub.1 -C.sub.18, linear or branched, optionally containing one or more ether oxygen atoms, or a (per) fluoropolyoxyalkylene radical. These products, upon peroxide curing, require extremely short post-curing treatments (around 30-60 minutes at 180.degree.-230.degree. C.) and are characterized by compression set values lower than 25% (measured on O-rings at 200.degree. C. for 70 hours according to ASTM Standard D395 Method B).
摘要:
Fluoroelastomers characterized by the presence of iodine or bromine atoms at the end of the polymeric chain in an amount equal to or lower than 1 iodine or bromine atom per polymeric chain, and by a bromine content in the chain ranging from 0.05 to 2% by weight referred to the total weight of the monomeric units.Said fluoroelastomers exhibit improved characteristics of processability, particularly as regards the utilization in injection molding processes and the detaching from the molds, as well as of stability to heat.A process for preparing fluoroelastomers containing iodine or bromine atoms at the ends of the polymeric chain, in an amount equal to or lower than 1 iodine or bromine atom per polymeric chain, which process comprises polymerizing mixes of fluorinated monomers (VDF, TFE, HFP, FVE) in bulk, in suspension, in aqueous emulsion, or in solution of organic solvents by means of radical starters, in the presence of compounds capable of providing I.sup.- or Br.sup.- ions in the polymerization medium and conditions.
摘要:
Fluoroelastic copolymers, suitable for the manufacture of O-rings, comprising by weight:48-65% of VDF units21-36% of HFP units3-9% of PAVE units0-17% of TFE units
摘要:
Fluoroelastomers characterized by the presence of iodine or bromine atoms at the end of the polymeric chain in an amount equal to or lower than 1 iodine or bromine atom per polymeric chain, and by a bromine content in the chain ranging from 0.05 to 2% by weight referred to the total weight of the monomeric units.Said fluoroelastomers exhibit improved characteristics of processability, particularly as regards the utilization in injection molding processes and the detaching from the molds, as well as of stability to heat.A process for preparing fluoroelastomers containing iodine or bromine atoms at the ends of the polymeric chain, in an amount equal to or lower than 1 iodine or bromine atom per polymeric chain, which process comprises polymerizing mixes of fluorinated monomers (VDF, TFE, HFP, FVE) in bulk, in suspension, in aqueous emulsion, or in solution of organic solvents by means of radical starters, in the presence of compounds capable of providing I.sup.- or Br.sup.- ions in the polymerization medium and conditions.
摘要:
The invention relates to new fluoroelastomeric copolymers endowed with resistance to bases and suitable in particular for preparing O-rings, comprising:______________________________________ (I) VDF 47-80 mols % HFP and/or PAVE 16-30 mols % hydrogenated olefin containing 2-25 mols % 2-4 C or (II) VDF 42-80 mols % PAVE 16-30 mols % hydrogenated olefin containing 2-30 mols % 2-4 C ______________________________________ The invention relates to new fluoroplastomeric copolymers endowed with resistance to bases, comprising:______________________________________ (III) VDF 70-99 mols % HFP and/or PAVE 0-16 mols % hydrogenated olefin containing 1-30 mols % 2-4 C ______________________________________ A further object of the invention is a process for preparing the abovesaid fluoroelastomeric and fluoroplastomeric copolymers.
摘要:
The invention relates to new fluoroelastomers endowed with a low Tg and a low compression set at low temperature, characterized by the following monomeric composition:______________________________________ vinylidene fluoride: 60.5-64% by weight hexafluoropropene: 30-33% by weight tetrafluoroethylene: 5-8% by weight. ______________________________________