A modified model predictions and experimental results of weld-line strength in injection molded PS/PMMA blends

• Published in: Polymer (Guilford) 2004, Vol.45 (9), p.2911-2920
• Main Authors: Guo, Shaoyun, Ait-Kadi, A., Bousmina, M.
• Format: Article
• Language: English
• Subjects: Applied sciences; Blends; Exact sciences and technology; Injection moulding; Machinery and processing; Moulding; Plastics; PMMA; Polymer industry, paints, wood; Technology of polymers
• ISSN: 0032-3861; 1873-2291
• DOI: 10.1016/j.polymer.2004.02.051

In this paper, the model based on melt diffusion and Flory–Huggins free energy theory for predicting the weld-line strength of injection molded amorphous polymers and polymer blends parts were modified by considering the diffusion thickness in the interface as a function of contact time. The modified model for weld-line strength prediction of homopolymers and polymer blends were, respectively, used to evaluate the weld-line strength of Polystyrene (PS) and Poly(methylmethacrylate) (PMMA), and that of PS/PMMA blends. The model predictions show that the theoretic predictions as a function of temperature and contact time for PS, PMMA and PS/PMMA (80/20, 70/30) are in good agreements with corresponding experimental results. However, the model predictions for PS/PMMA (20/80, 30/70) blends are much higher than experimental results. The morphology in weld-line regions for PS/PMMA (20/80, 30/70) shows lack of dispersed PS phase. Near the weld-line regions, dispersed PS phase is highly oriented along the weld-line. In theoretic prediction for polymer blends, three kinds of diffusion: Polymer A–Polymer A and Polymer B–Polymer B self-diffusions and Polymer A–Polymer B mutual diffusion were considered. This is why model predictions for PS/PMMA (20/80, 30/70) blends are higher than experimental results.