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

Abstract

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 (>308C) 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.

The influence of process parameters on the properties of hot compacted self-reinforced polypropylene composites

“…This process has a narrow, yet viable temperature window. An alternative process is co-extrusion, developed by Peijs and co-workers [3][4][5][6]. This process uses bicomponent tapes, in which the outer layer is a lower-melting point copolymer and the inner layer is a homopolymer.…”

Injection moulded all-polypropylene composites composed of polypropylene fibre and polypropylene based thermoplastic elastomer

“…Their combination opens a new horizon for the industrial production of all-polymer composites. Nowadays, all-polymer and self-reinforced materials/composites [7] can be produced with narrow processing window by hot compaction (single-component self-reinforced materials (SRM)) [8][9][10][11], consolidation of coextruded tapes [12][13][14] and filmstacking methods (multi-component SRM) [15][16][17][18][19][20][21]. In addition, all of the above processing methods yield sheet-like (pre)products which can be shaped thereafter by thermoforming.…”

Hot consolidated all-PP composites from textile fabrics composed of isotactic PP filaments with different degrees of orientation

“…The first technique is hot compaction, where the outer layer of the fibers melts and recrystallizes as a matrix in a suitable temperature and pressure range [1,5,6]. The second one is co-extrusion, where a thin layer with lower melting temperature is co-extruded with a highly oriented, thicker core, and these bands are textile structured and hot consolidated [2,[7][8][9]. Finally, there is the filmstacking method, where the matrix and reinforcement layers are laminated onto each other and are hot pressed [3,4,10,11].…”

“…In case of the film-stacking method, the material selection and combination is more flexible and the composite production can also made continuously by using a double belt press. In case of the latter two methods the melting temperature difference (20-30°C; in case of PP) can be reached if random PP copolymer/isotactic PP (iPP) [2,3,[7][8][9][10][11][12]; beta polymorph of iPP/iPP fiber [4] combinations are used. Furthermore, the processing window is narrower (7-8°C) if various iPP fibers having different stretching ratios (orientation degrees) are used.…”