Interfacial properties of highly oriented coextruded polypropylene tapes for the creation of recyclable all-polypropylene composites

The creation of highly oriented, coextruded polypropylene (PP) tapes allows the production of novel, wholly thermoplastic, recyclable all-polypropylene (all-PP) composites, which possess both a large temperature processing window (>30°C) and a high volume fraction of reinforcement phase (highly oriented PP tapes: >90%). This large processing window is achieved by using coextruded, highly drawn PP tapes. To achieve coherent all-PP composites the interfacial characteristics following consolidation must be understood. This article investigates the interfacial characteristics of these coextruded tapes by using microcomposite models to create interfaces between tapes of varying draw ratios, drawing temperatures, skin/core ratios, and skin layer thicknesses. The tape drawing parameters are seen to control the interfacial properties in subsequent microcomposite models. The failure mode of these specimens, and hence bond strength, varies with consolidation temperature, and a model is proposed describing and explaining this behavior.