Curing initiators

For a complete panel replacement, the refinisher starts with a panel preprimed in the appropriate stoving primer. For spot repairs or larger repairs without replacement of metal, there will be areas which have to be rubbed through to clean metal. Any indentations then have to be filled with a stopper or spray filler, probably based on unsaturated polyester resins and styrene, with cure initiated by mixing in an organic peroxide. After sanding, remaining bare metal areas are sprayed with a two-pack etch primer. 

Coating materials may be based on short or medium-oil alkyds (e.g. primers for door and window frames) nitrocellulose or thermoplastic acrylics (e.g. lacquers for paper or furniture finishes) amino resin-alkyd coatings, with or without nitrocellulose inclusions, but with a strong acid catalyst to promote low temperature cure (furniture finishes) two-pack polyurethanes (furniture, flat boards) unsaturated polyester resins in styrene with free-radical cure initiated by peroxides (furniture) or unsaturated acrylic oligomers and monomers cured by u.v. radiation or electron beams (coatings for record sleeves paperback covers, knock-down furniture or flush interior doors). 

This procedure, at first glance, merely involves combining a dried expl, such as HMX, with binder constituents and curing initiators in a mixing vessel, blending to desired homogeneity,... 

In films cured initially at 175°C, determination by infrared spectroscopy of the concentration of anhydride groups indicated that all potential cross-linking groups had reacted. 

The type of crosslinking achieved with electron beam and uv radiation is very similar, but the way curing initiates is different. Electron beams have the higher energy, and the electron itself has sufficient energy to initiate polymerization. In uv curable materials, the polymerization reaction is not directly initiated by uv light, and a photoinitiator is required to interact with the uv radiation and produce the initiating species. 

This moldable material primarily consists of TS polyester resin, glass fiber reinforcement, and filler. Additional ingredients, such as low-profile additives, cure initiators, thickeners, and mold-release agents are used to enhance the performance or processing of the material. As with any material, such as metallics and plastics, SMC can be formulated in-house or by compounders to meet performance requirements of a particular application such as tensile properties or Class A surface finish. Varying the type and percentage of the composition will result in variations in mechanical properties and processability. 

A review of flash photolysis spin resonance describes CIDEP techniques which can be used to identify free radicals. Time resolved ESP and ENDOR has been used during the photolyses of M,W-dimethoxy-W-phenylacetophenone, an efficient UV curing initiator. ... 

The elastomers investigated were prepared by curing a silicone resin (supplied by Rhodia Silicones) containing a blend of ingredients polysiloxane-diols, small amounts of hydrogen-methyl polysiloxane, tetraalkoxy silane and fumed silica filler. An organotin ingredient, stannous 2-ethylhexanoate, supplied as a 77% w/w solution in 2-ethyl hexanoic acid, was used as a cure initiator. Typically, 5 wt. of initiator is mixed into the polysiloxane resin. After the initial cure, the material is post-cured at 70°C for 16 h in an air oven. 

Vents It shall be provided on the equipments at suitable places for escape of moisture during curing/initial heating. This can prevent development of stress inside. 

Change in the light-scattering profile with time in seconds since cure initiation. 

Such multifunctional esters are used to promote the formation of a rigid cross-linked structure on polymerization. Quantitation of these esters is normally based on GC analysis using an internal standard. Either narrow or wide bore capillary columns may be used. In the case of ultraviolet cure-initiated formulations, the use of higher-molecular mass urethane-methacrylate resins such as Scheme 7 is involved. 

Many of these adhesives have a rather stringy nature and all require the use of a cure initiator, which may be pre-mixed prior to application or applied to at least one of the adherends prior to assembly. 

Vents should be provided for escape of moisture during curing/initial heating. 

UV cure initiators include aromatic ketone, used in printing ink and paper coating benzoine ether, a general UV cure initiator for FRP laminates, putties and lacquers, particularly effective with fillers and a mixture of ketones, used with an amine accelerator for UV-curlng FRP laminates. 

SMC is refrigerated before use because it contains a curing initiator and thus has a limited shelf-life. SMC should be handled with care because the styrene cross-linker is quite volatile. 

One-part aqueous emulsion (cure initiated by slight drop in water content on exposure to atmosphere). 

Cure Initial 15 mins/RT. Full cure 48 hr. Cure RT. ... 

Cure Initial cure 15 mins, Full cure 1 hr. Cure Full cure 72 hr. ... 

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