Unique Additives for Polymer Modification

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Products Referenced

SMA®
Ricon®
Resources

Technical Paper
CARE

Reactive Extrusion

Cray Valley styrene maleic anhydride (SMA®) resins can be used as additives to promote reactive chain extension, mainly in polyamides, in order to improve the melt characteristics and mechanical properties. The function of the chain extender is to bridge two or more adjacent polyamide chains together thereby increasing the effective molecular weight, and branching structure. Altering the molecular architecture via reactive extrusion can increase the melt flow, and tensile properties of both virgin and recycled* polyamides alike. Alternatively, low molecular weight polybutadiene additives offer a rubbery link between chains to promote flexibility. Typical levels of SMA® are in the range of 0.25 – 1 weight % based on the entire compound.

Figure 1 demonstrates the range of expected property improvements from introducing SMA® to a recycled polyamide. The absolute improvements will be a function of the inherent properties of the recycled polyamide, along with the grade and loading level of SMA®. Historical data has shown that SMA® had a significant influence on heat distortion temperature (HDT), tensile modulus, flex modulus and Izod impact strength. Compared to other commercial anhydride functional materials, SMA® resins are low molecular weight with variable functional loadings that allow the user to select the most appropriate product for a given application.

Figure 1
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Figure 2 demonstrates the typical improvement in melt strength produced by integrating a fractional loading of SMA® into an unfilled, undried PA66. Incorporating 0.5 weight % SMA® 3000P into the melt stream the processibility of the extrudate improved dramatically.

Figure 2
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Cray Valley HSC’s Functional Additives are applicable to both filled and unfilled systems alike. Figure 3 demonstrates the value of incorporating 1 weight % of a functional low molecular weight polybutadiene to a standard 30 weight % glass fiber filled PA66. The anhydride functional polybutadiene (Ricon® 131MA5) can increase modulus, tensile strength and impact by extending the matrix with a rubbery additive.

Figure 3
Diamond-Graph
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