RIM polyurethane

Polymeric isocyanates or PMDI ate cmde products that vary in exact composition. The main constituents are 40—60% 4,4 -MDI the remainder is the other isomers of MDI, trimeric species, and higher molecular weight oligomers. Important product variables are functionaHty and acidity. Rigid polyurethane foams are mainly manufactured from PMDI. The so-called pure MDI is a low melting soHd that is used for high performance polyurethane elastomers and spandex fibers. Liquid MDI products are used in RIM polyurethane elastomers. 

All structural foam substrates were 1/4 inch in thickness except for RIM polyurethane, which was 1/2 inch in thickness. These comments hold for samples throughout the study. For solid plaques, samples were 3/32 inch thick. 

The substrates tested alone have substantially different values. Polycarbonate (1/4 inch) structural foam has an of 27.5, modified-polyphenylene oxide (1/4 inch), 84.4, and RIM polyurethane (1/2 inch), 173.3. These values compare with 164.4 for 1/4 inch hardboard and 139.1 for 1/4 inch plywood. A comparison of graphite, nickel, and copper/aciylic coatings on polycarbonate and modified-polyphenylene oxide substrates illustrate a dramatic result. Despite a factor of 3 difference in substrate performance, the Q and Fs values for the coated samples are very similar. The Q for the modified-polyphenylene oxide samples are 0.7 to 0.5 that of the uncoated sample. One would expect a similarity in Fs for the coated sample, but such a reduction in Q is dramatic. Both Q and Fs are determined by the 2 mil surface. 

Two of the zinc surface samples show results that might intuitively be expected for metal coated surfaces. The polycarbonate and RIM-polyurethane substrates show much lower Fs values with the zinc coating as expected, but Q values are very similar to that of the uncoated substrates. For modified-polyphenylene oxide, however, a very low Q value is obtained suggesting flame... 

Figure 3. Continued. NBS Smoke Chamber results (non-flaming) for modifled-polyphenylene oxide and RIM polyurethane structural foam.

Tables VII and VIII sumnarize present and future RIM engineering plastic developments. This is an emerging area for RIM processable materials part of which will be made possible by recent equipment developments such as hot RIM. Polyurethane materials which now exist in this hard segment range are plastics...

Several studies have been published in recent years on the properties of RIM polyurethanes and polyurethane-ureas (1-7). Unlike most studies, however, we have restricted our attention to simplified linear systems in order to establish the effect of reaction rates and mold temperatures on the phase separation and molecular weight of segmented polyurethane elastomers produced by RIM(6). 

Investigations of the Structure-Property Relationships for RIM Polyurethane Elastomers... 

TURNER ET AL. RIM Polyurethane Elastomers Amine Additive Effects... 

Results and Discussion. X—ray diffraction densitometer scans are presented In Figures 2 for the 18 EG and Figure 3 for the 30 EG series for RIM polyurethanes. DSC and Storage Modulus traces (El) for the same specimens are shown In Figures 4, 5 and 6, and flexural modulus, elongation, Impact strength, and heat sag data are given In Table I. 

NBC (Nyrim) is more expensive than RIM polyurethane but it may be heated to 200°C without softening. NBC moldings are produced by the reaction injection molding (RIM) of polypropylene glycol and caprolactam in the presence of a catalyst. The tendency for this copolymer to swell in the presence of water is reduced by reinforcing with glass fibers. 

RIM polyurethane elastomers are a natural to meet the regulations. The process is highly suitable for producing complicated large, thin fascia to cover the entire front end... 

All the above factors taken together - damageability resistance, styling freedom, and weight savings - have led to a very rapid rise in the RIM polyurethane fascia and bumper cover market. Table I historically summarizes the market from 1977 to 1980. 

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