The effect of draw ratio on the mechanical properties and crystalline structure of single polymer polypropylene composites

• Published in: Polymer (Guilford) 2016-05, Vol.91, p.156-161
• Main Authors: Foster, Richard J., Hine, Peter J., Ward, Ian M.
• Format: Article
• Language: English
• Subjects: Compacting; Crystal structure; Differential scanning calorimetry; Draw ratio; Hot compaction; Mechanical properties; Orientation; Polymer composites; Polymer matrix composites; Polypropylenes; Tensile strength
• ISSN: 0032-3861; 1873-2291
• DOI: 10.1016/j.polymer.2016.03.042

The properties of self-reinforced single polymer composites produced by the Leeds hot compaction process are highly dependent on the compaction temperature as well as the constituent oriented elements used to produce the compacted sheets. In this paper, the variation in tensile mechanical properties of uniaxial hot compacted sheets manufactured from drawn polypropylene (PP) tapes with change in compaction temperature have been investigated, for a range of different draw ratio tapes. It is shown that there is a measureable difference between the optimum compaction temperatures required for obtaining the highest modulus and strength in the compacted sheets. The compaction temperature required to achieve the maximum tensile modulus was seen to increase with increasing draw ratio. The compaction temperature to obtain the maximum tensile strength was found to be both independent of the draw ratio and a few degrees higher than that for obtaining the maximum modulus. Peak modulus and peak tensile strength was shown to be dependent on the draw ratio of the drawn tape. Differential scanning calorimetry measurements on the compacted sheets were also performed in order to investigate the change in crystalline structure with compaction temperature and draw ratio. This has shown that the changes in structure within the oriented phase (i.e. tapes) during the compaction process itself are directly related to the final properties of the hot compacted sheets. [Display omitted] •Max Young's modulus and failure strength require different processing conditions.•Crystalline structure change is directly related to change in mechanical properties.•Maximum failure strength is independent of draw ratio.