ISONATE* 143L modified MDI is a polycarbodiimide-modified diphenylmethane diisocyanate. Liquid at room temperature, this product has a low viscosity and good storage stability down to 75°F (24°C). The polycarbodiimide adduct offers extra flexibility because adduct formation is reversible (dissociation generates an additional isocyanate function). The carbodiimide linkage aids the stabilization of the polymer against hydrolytic degradation. Because this product can be used alone or in mixtures with prepolymers, its higher functionality offers faster demold times than is ordinarily possible with linear prepolymers. A unique combination of high modified MDI content, available carbodiimide, and liquid state allows ease of handling, ease of processing and maintenance of high physical properties under strenuous wear and environmental conditions.
Applications: Adhesive and Sealants, Elastomers, Coatings, Automotive Parts, Integral-Skin Plastics , Tires and Wheels, Shoe soles, Carpet underlay/adhesives, Recreational goods and Mechanical goods.
Isocyanate equivalent weight 144.5
NCO content by weight 29.2%
Hydrolyzable chloride 30 ppm
Acidity (as HCl) 0.002%
Viscosity (at 25oC) 33 cps
Density (at 25oC) 1.214 gm/ml
Vapor Pressure (at 25oC) < 10-5 mm Hg
Extrapolated Boiling Point 314oC
Approximate Decomposition Point 230oC
Flash Point (ASTM D 93, closed cup) > 177oC
Specific Heat 0.43 gm.cal/gm.oC
Thermal Conductivity 0.0003 gm.cal/cm.sec.oC
Coefficient of Thermal Expansion 0.0009 kg/l/1oC
Heat of Vaporization 86 cal/gram
Viscosity Growth (at 25oC) 2 – 5 cps/mo
Packaging Sizes: 1 quart and 1 gallon plastic bottles
* Isonate 143L is a Trademark of the DOW Chemical Company
Drums of modified MDI must be protected from moisture contamination. Exothermic generation of CO2 may cause dangerous pressure build-up if contamination occurs. If conditions favor polymeric growth, solids will form and will adversely affect product performance.
To prevent polymeric formation, ISONATE 143L modified MDI must be protected from exposure to water vapor or oxygen and from exposure to temperatures below 75°F (24°C) and above 105°F (41°C).
Recommended shipping and storage temperatures for ISONATE 143L modified MDI are 75° to 105°F (24°F to 41°C). If shipping or storage temperature should fall below 65°F (18°C), some crystallization could result. Unless proper action is taken to re-form the original solution, subsequent dimerization will proceed quickly and will deteriorate the assay of the product.
If drum shipments of polymeric or modified MDI products arrive in a crystallized, frozen, or fused state, they should be promptly unloaded and heated as soon as possible. Polymeric, pure and modified MDI products that have been frozen will exhibit the same dimerization characteristics as pure MDI. Unless proper action is taken to heat or melt the product, dimerization will proceed rapidly and deteriorate both the clarity and assay of the product.
While several methods for melting frozen or crystallized MDI have been developed, the method of choice should be one in which dimer formation is minimized. This can best be accomplished by rapid, even heating of the drums, as follows.
The preferred method for heating drums is “drum rolling” (usually at 5 rpm on a mechanical drum roller) in atmospheric steam. The principal advantage of this method is that it permits efficient heat transfer – that is, the solid MDI crystals cool the liquefied material so that the contents are not heated much beyond 70°C
(158°F), the point at which dimer formation can increase significantly.
Experience has shown that a frozen drum of polymeric, pure or modified MDI, with a temperature between -4° to 32°F (-20° to 0°C), will usually melt completely (i.e. reach 70°C [158°F] in approximately four to five hours). Also, while 70°C
(158°F) is significantly higher than the recommended storage and handling temperature, it is necessary to reach this temperature, at least briefly, in order to melt the product both quickly and thoroughly. Before heating, any opened drums should be reblanketed with dry nitrogen (-40°F [-40°C] dew point) and all drums, previously opened or not, should have bungs tightened securely.
Upon removal from the steam chest, residual heat will usually evaporate free water from the drum head. In any event, the top of the drum should be wiped with a dry cloth. As can be seen, agitation and even heating is the key to maintaining quality during melting.
Dow does not recommend static melting in hot-air oven or with electric heating apparatus, or by hot-water bath.
CAUTION: The “drum rolling” procedure should be carefully monitored to prevent bumping, rubbing or other conditions that could puncture or otherwise damage the drums.
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