Resin transfer molding (RTM) comprises resin injection in a closed mold in which the reinforced material is placed in advance. This can be done in an ambient temperature mold, but also in a mold with external heating to cure at elevated temperatures.

Nouryon curing agents

The curing system for RTM is mainly determined by the time which is needed to fill the mold and on the peak exotherm that is allowed given the thickness of the part. The geltime of the resin formulation is related to the needed injection time. The main peroxides used for RTM are Butanox® M-50 and Butanox M-60.

Trigonox® 44B gives similar gel time as Butanox M-50 but gives a much higher peak exotherm and a faster curing. It is used when the part is thin and the peak exotherm is not prohibitive.  Trigonox 61,Trigonox 63 and Trigonox 65 are blends of Butanox M-50 and Trigonox 44B and will give similar geltime but in-between peak exotherms.

To monitor the curing Nouryon also offers peroxides with a red color indicator that vanishes during the curing step, the so called Vanishing Red (VR) grades. This material is particular use for vacuum foil injection process. It gives a visual check that the peroxide is mixed-in during the injection step (the resin is colored red) and allows monitoring the curing as during curing the red color disappears. The main product for RTM is Butanox M-50 VR .

In special occasions the curing for RTM can be done using Perkadox® L-40RPS which is a phthalate-free pumpable 40% benzoylperoxide suspension which is used in combination with a tertiary amine such as Accelerator NL-67 as accelerator.

Trigonox 42PR and Trigonox 524 are used when curing is done at elevated temperature and with a peak exotherm which is sufficiently high. These peroxides give an efficient curing and very low residual styrene levels.

Main end products

The end products from the RTM process are very diverse and range from very small parts to very large. A two-sided mold has limited size, whereas a one-sided mold (using a vacuum bag injection technique) can deliver, for example, 75 meter long rotor blades for wind turbines. RTM parts are for example used in the construction market, automotive industry, sandwich panels and boats. 

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