Insulation board is made of unbleached sulphate pulp Smooth.tough.mechanical and electric intensity Insulative ... ,1000*1000mm,1400*2500mm,2100*4200mm,3200*4200mmSpecial:Material free of strains,very flat,highest machanical and electrical strength.Good mechanical ... resistance , larger tightness, smaller shrinkage, excellent flatness are the main strong Strengths of this product. Insulation paperboard