Methyl ethyl ketone peroxide MEKP

The reaction rate of fumarate polyester polymers with styrene is 20 times that of similar maleate polymers. Commercial phthaHc and isophthaHc resins usually have fumarate levels in excess of 95% and demonstrate full hardness and property development when catalyzed and cured. The addition polymerization reaction between the fumarate polyester polymer and styrene monomer is initiated by free-radical catalysts, commercially usually benzoyl peroxide (BPO) and methyl ethyl ketone peroxide (MEKP), which can be dissociated by heat or redox metal activators into peroxy and hydroperoxy free radicals. 

Commercial methyl ethyl ketone peroxide (MEKP) is a mixture of compounds and is a liquid usually supplied blended into dimethyl phthalate, the mixture... 

Triethylamine was fractionally distilled from lithium aluminum hydride under nitrogen and acryloyl chloride was distilled under nitrogen. 1,1,2-Trichlorotrifluoroethane (Freon 113) was distilled from phosphorus pentoxide under nitrogen. Azobisisobutyronitrile (AIBN) was used as received. Methyl ethyl ketone peroxide (MEKP) (9% Organic Peroxide VN 2550) was obtained from Witco. Alumina (neutral, Brockman activity 1, 80-200 mesh) was obtained from Fisher Scientific Co. All reagents were obtained from Aldrich unless otherwise specified. 

The polyester product is first dissolved in styrene at a level of 60 % polyester and 40 % styrene. The initiators, either benzoyl peroxides (BPOs) or methyl ethyl ketone peroxide (MEKP), with appropriate co-catalysts, are added. The mixture is then poured into a glass mold and cured at room temperature for the MEKP system or at 100 °C for the BPO systems. A post-cure at 100 °C or 130 °C, respectively, for 5 h is then carried out. Blending experiments were carried out by using a dicyclo pentadiene (DCPD) resin, 61-AA-364, from GLS Fiberglass (Woodstock, IL, USA). This sample is pre-promoted , so we could only use the MEKP system. 

Toxieology. Methyl ethyl ketone peroxide (MEKP) is a skin and eye irritant. 

Starting with ketones and hydrogen peroxide in the presence of a catalytic amount of acid, mixtures of up to eight components have been identified, i.e.. (1, X = OH. R3 = H), (1, X = OOH, R3 = H), (2, X = Y = OH). (2, X = Y = OOH), (2, Y = OH, Y = OOH), (3). (4), and (5). The ketone structure and reaction conditions, i.e., acid strength, reactant molar ratios, temperature, and time, determine which compounds form and predominate. Mixtures of several peroxide structures usually are present. Individual peroxides have been isolated from several ketones under different conditions (Table 5). The pure peroxides should be handled with extreme caution since most, especially those derived from the low moleculai weight ketones, ate shock- and friction-sensitive and can explode violently. Methyl ethyl ketone peroxide (MEKP) mixtures are produced commercially only as solutions containing <40 wt% MEKPs in solvents, commonly dialkyl phthalates. 

Fig. 1.14 Molecular structures of triacetone triperoxide (TATP), hexamethylene triperoxide diamine (HMTD), methyl ethyl ketone peroxide (MEKP) and diacetone diperoxide (DADP).

The two most important peroxy materials used for room temperature curing of polyester resins are methyl ethyl ketone peroxide (MEKP) and cyclohexanone peroxide. These are used in conjunction with a cobalt compound such as a naphthenate, octoate, or other organic-solvent-soluble soap. The peroxides are referred to as catalysts (though, strictly speaking, these are polymerization initiators) and the cobalt compound is referred to as an accelerator. 

When it is necessary to start and even cause a complete cure at lower temperatures so that the polymerization heat can readily be dissipated, methyl ethyl ketone peroxide (MEKP) is the catalyst generally used. It does not lead to a full cure by itself at ambient temperatures. However, with the addition of an accelerator, the catalyst will cause gelation and almost complete cure within short periods of time, depending on the percentage of each used with the resin. From 0.5 to 2.0% of MEKP and 0.1 to 1.0% of cobalt naphthe-nate accelerator can be used, depending on the desired working time of the resin. 

The samples used in this study include a modified blocked isocyanate, isophorone diisocyanate (IPDI), (B-1370, Huls AG, Gelsenkichen-Buer, W. Ger.) and both catalyzed and uncatalyzed polyester gel coat resins. Gel coat cure reactions were initiated with the addition of 1.0 wt. percent of methyl ethyl ketone peroxide (MEKP, Lucidol Div., Pennwalt Corp., Buffalo, N.Y.) and catalyzed with the addition of 0.15 wt. percent cobalt octoate solution (12% cobalt in mineral spirits, Mooney Chemicals, Cleveland, OH.). 

Similar to the vegetable oil-based polyesters, the curing system must be selected according to the nature of the oil. As an example, for non-drying oil-based poly(ester amide), the following system can be used. A homogeneous mixture of resin with 30 parts of styrene or methyl methylacrylate as the reactive diluent, four parts of methyl-ethyl ketone peroxide (MEKP) as an initiator and two parts of cobalt octate/naphthenate as an activator, are prepared in a container at room temperature by mechanical stirring. The thin films of the resin system can then be cured at the desired temperature for a predetermined period of time. 

Non-drying vegetable oil-based poly(ester amide) resins require a long time period and a high temperature for curing by conventional transition metal catalysed peroxide systems, such as Co-/Mn-octate/naphthate with methyl ethyl ketone peroxide (MEKP), in the presence of styrene as a... 

The most widely used peroxide catalyst is methyl ethyl ketone peroxide (MEKP), which is really a mix of several peroxides and is available for various activity levels. 

Methyl ethyl ketone peroxide (MEKP, MED, and peroxide) n. A complex peroxide mixture made by reacting hydrogen peroxide with MED, with the approximate formula (CH3C00C2H5)3. MEKP is an initiator for free-radical polymerization and a curing agent for polyester resins. In combination with an accelerator such as cobalt naphthenate, MEKP can bring about cure at room temperature. Because... 

Ketone peroxides. Ketone peroxides are mixtures of peroxides and hydroperoxides that are commonly used during the room temperature curing of polyester. Methyl ethyl ketone peroxide (MEKP) is the major product. 

The family of dialkyl peroxides includes dicumyl peroxide, which accounts for one-third of the volume of dialkyls world-wide and is the workhorse of this family of peroxides. Dicumyl peroxide is commonly used as a catalyst in polyester resin systans and for cross-linking polyethylene. Benzoyl peroxide is the most common of the diacyl peroxides. It is also used as a catalyst for curing polyester resins. Hydroperoxides are generally used as a raw material to produce other organic peroxides. The most common peroxides in this family include cumene hydroperoxide and t-butyl hydroperoxide. Ketone peroxides are mixtures of peroxides and hydroperoxides that are commonly used for room-temperature curing of polyester resins. Methyl ethyl ketone peroxide (MEKP) is the major product in this family. Peroxydicarbonates are largely used to initiate polymerization of polyvinyl chloride (PVC). 

The high-strength Basalt fiber (Plain weave, 150 g/m2) which is supplied by ASA. TEC, Austria are used in the present study. The isopthalic polyester resin used for matrix system is ISO-4503 procured from Vasavibala resins (P) Ltd., Chennai (viscosity 500-600 cps, acid value 15-19, gel time 15-25 min, heat deflection temperature 95 °C). One weight percent of accelerator (cobalt Napthanate) and 1 wt% of methyl ethyl ketone peroxide (MEKP) catalyst were mixed with the polyester resin. The type of epoxy resin used here is LY 556 and the hardener HT 951 both supplied by M/s Hindustan Ciba Geigy Limited, Mumbai, India. 

Unsaturated polyester (Butanox M-60) mixed with 1.5% of Methyl Ethyl Ketone Peroxide (MEKP) as catalyst was selected as a resin for the current work. Treatedbetelnut fiber reinforced polyester (T-BFRP) composite was fabricated using hand lay-up technique. In composite preparation, a metal mould (100 x 100 x 12 mm) was fabricated. The inner walls of the mould were coated with a thin layer of wax as release agent. The first layer of the composite was built by pouring a thin layer of polyester. A prepared mat was placed carefully on the polyester layer. Steel roller was used to arrange the mat and eliminate trapped bubbles. This process was repeated until the composite block was built containing 13 layers of fiber mats and 14 layers of polyester. The prepared blocks were pressed at approximate pressure of 50 kPa in order to compress the fiber mats and to force out the air bubbles. The blocks were cured for 24 hr and then machined into specimens in the size of 10 x 10 x 20 mm. 

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