Weld line is the most common problem found in injection moulding and manufacturing. The aim of this thesis is to know what and how the factors influence the injection moulded weld line. The factors considered are process parameters, selection of materials and environment. At first, the material composites were compounded and tensile tested to see their strength. Then, an experimental design was performed to observe the influence of process parameters. As a final test the materials obtained from compounding with mineral C were placed under a specific environment to imbibe moisture and then to see how they effect on weld line strength. In one of those material composites compounded, the ‘mineral A’ was used in a little proportion to the whole mixture. The results obtained from the tensile test were examined and compared with mineral B, since it is the general material used in present industrial application. From the comparisons and results it was found that strength of mineral A is relatively equal with respect to mineral B. Finally, the effects of environment on weld line were observed using the mineral C. Experiments carried out for the fracture failure of dogbones. The notches present in the samples failed at low stress at break values and the notched samples of mineral A and mineral B were compared in this test. After all tests, mineral A has been more favourable besides mineral B. Also ‘mineral A’ can be a potential mineral for this application in the industry.