Rigid PVC Modification

DuPont™ Elvaloy® resin modifiers improve the performance and lower the cost of rigid PVC compounds

- January 01, 2016 -

For makers of rigid PVC products, Elvaloy® resin modifiers widen the melt temperature processing window and lower PVC compound viscosity without increasing fusion time. This helps users increase extruder speed and improve the dimensional accuracy of PVC extruded profiles.

Benefits of Using Dow™ Elvaloy®

  • Increased production rates due to ductile dart-drop impact performance at lower extrusion temperatures. Parts will cool faster, extrudate should be stiffer and easier to handle, size etc.
  • Reduced ingredient costs by increasing the low-cost filler level, reducing thermal stabilizers and/or reducing process aids
  • Better ductile impact performance at higher filler loadings that competitive products
  • Smoother extrudate surfaces, as evidence by higher gloss, will maintain impact performance longer and resists cracking better

The following table shows Gardner dart drop test* results comparing PVC impact brittleness for three different modification resins at three different processing temperatures:

PROCESS TEMPERATURE 

 ACRYLIC  ELVALOY® 4924   ELVALOY® HP661 
 180°C   Ductile  Ductile  Ductile
 170°C  Brittle  Ductile  Ductile
 160°C  Brittle  Brittle  Ductile
 

*Gardner Drop Dart: ASTM D4226 \"Impact Resistance of Rigid PVC Building Products\" - Procedure B. All samples are tested until either brittle failure or the capacity of the test was exceeded at 264 in.-lb.

A Range of Choices for PVC Impact Modification

The following table lists Dow™ Elvaloy® terpolymers (arranged by chemical type) used for rigid PVC toughening:

ELVALOY® GRADE USED IN RIGID PVC

POLYMER TYPE   MELT INDEX (G/10 MIN.)   DENSITY (G/CM3)
 Elvaloy® 741   E/VA/CO  35   1
 Elvaloy® 742  E/VA/CO  35  1.02
 Elvaloy® 4924  E/VA/CO  15   1.03
 Elvaloy® HP441  E/nBA/CO  8  0.98
 Elvaloy® HP661  E/nBA/CO  12   0.96
 Elvaloy® HP662  E/nBA/CO  25   0.96
 

Although effective when used as the primary PVC impact modifier, Elvaloy® also can be used in combination with other impact modifiers to balance viscosity, die swell and cost.