[1] The difference in Mooney viscosity of the elastomer used is too large;
  [2] Inappropriate selection of plasticizer and rubber;
  [3] Too much granules;
  [4] Small particle size filler excess;
  [5] Use resins with excessively high melting points;
  [6] Liquid plasticizers are not enough;
  [7] Excessive fillers and plasticizers