The effect of moisture conditioning on the mechanical and physical properties of long glass fibre reinforced nylon 66 materials

Abstract

The effect of moisture conditioning on the mechanical and physical properties of ICI's 'Verton' range of long glass fibre reinforced Nylon 66 materials have been investigated using injection moulded test specimens. Natural and black grades, at glass loadings of 35%, 50% and 60% by weight have been examined together with a natural un-reinforcd Nylon 66 grade.The tensile strength of the matrix polymer reduced from 80 MPa at dry - "as moulded" to 30 MPa when fully moisture saturated. Dry - "as moulded" tensile strength values for the glass reinforced grades ranged between 198 MPa and 255 MPa for the natural grades and between 183 MPa and 251 MPa for the black. With moisture conditioning for 1000 hours (42 days) at 60ºC these values were reduced from 92 MPa to 119 MPa for the natural grades and 87 MPa to 120 MPa for the black. The dry - "as moulded" flexural strength values ranged between 280 MPa to 365 MPa and 249 MPa to 369 MPa for the natural and black materials, respectively. As with tensile strength these values were also reduced with moisture uptake. For the same moisture conditions the values of strength measured in flexure were reduced more than in tension. For natural materials the values ranged between 80 MPa to 102 MPa and from 70 MPa to 92 MPa for the black. The dry impact strength of notched samples ranging from 22 kJ/m^2 to 42 kJ/m^2 was found to increase to approximately 63 kJ/m^2 for the natural glass/Nylon 66 materials when fully moisture conditioned. The impact strength of black materials ranged from 15 kJ/m^2 to 37 kJ/m^2 dry and increased to approximately 61 kJ/m^2 with moisture conditioning for 1000 hours at 60ºC. All changes in mechanical and physical properties were interpreted in terms of the effects of Fickian moisture uptake on the likely properties of the 'skin' and 'core' regions of injection moulded samples.