All-PP composites (PURE®) with unidirectional and cross-ply lay-ups: dynamic mechanical thermal analysis

Abstract

The original concept of self-reinforced composite, a composite with matrix and reinforcement from the same polymer, was presented by Capiati and Porter [1] three decades ago for high density polyethylene. Later this concept was adopted to polypropylene (PP) [2][3][4][5] [20,21]. Particularly, in a series of recent papers, Alcock and coworkers [22][23][24] described composite materials in which both the reinforcement and the matrix were based on PP. The related composites under the trade name of PURE ® are produced from highly oriented co-extruded tapes having a skin-core-skin (A:B:A) morphology. The skin layer (A) contains a PP random copolymer, whereas the core layer (B) is composed of PP homopolymer.Since the copolymer skin layer has a melting temperature below that of the homopolymer core, selfreinforced (also termed as homocomposites or all-PP composites) PP systems can be produced using a suitable processing window. Note that during consolidation the PP copolymer forms the matrix, while the highly oriented PP homopolymer fraction acts as continuous reinforcement. This approach (i. e. copolymer for the matrix and homopolymer for the reinforcement) can be used to produce all-PP composites using the film stacking technique, as well [25]. The most recent development with all-PP composites is to exploit the polymorphism-related difference in the melting range between the beta-(giving the matrix) and alpha-phases (serving as reinforcement) PPs [26,27]. All-PP composites are characterized by their outstanding mechanical properties at very low density. Their main advantage over conventional glass fiber reinforced ver-519 * Corresponding author, e-mail: karger@ivw.uni-kl.de © BME-PT and GTE Abstract. All polypropylene (all-PP) composite laminates with unidirectional (UD) and cross-ply (CP) lay-ups were produced by hot consolidation from oriented coextruded PP tapes (PURE ® ). The consolidation of the tapes, wound on a steel plate, occurred in autoclave vacuum bag molding. The set processing conditions resulted in all-PP laminates of high rigidity as the PP copolymer surface layers of the tapes were molten and thus forming the matrix, while their PP homopolymer core remained unaffected and thus fulfilled its role as reinforcement. Specimens cut off from the laminates were subjected to dynamic mechanical thermal analysis (DMTA) in a broad temperature range (T = -50…120°C) at various frequencies (f = 10 -2 …10 1 ). For the DMTA results the time-temperature superposition principle was adopted and master curves in the form of storage modulus vs. frequency (f = 10 -9 …10 20 ) and loss factor vs. frequency were created. All-PP composites (PURE

Fabrication and mechanical properties of self-reinforced poly(ethylene terephthalate) composites

“…Ward and coworkers [7][8][9][10][11] further developed this type of composite material using the 'hot compaction' technique. Following this study, opening literatures has reported numerous studies on the preparation of self-reinforced polypropylene (PP) [8,[11][12][13][14][15][16][17], polyethylene terephthalate (PET) [4,9,[18][19], polymethyl methacrylate [20], liquid crystal copolymer [21][22], polylactic acid [23], and poly amide [24][25][26] composites. In particular, the self-reinforced PP composites are now available on the market under the trade name Curv ® , Armordon ® , and Pure ® [5].…”

“…Therefore, in order to minimize the degradation, the hot compaction process should be performed as rapidly as possible. Bárány, Karger-Kocsis and coworkers [14][15][16]34] studied the processing parameters of self-reinforced PP composites and concluded that the consolidation temperature is more suited to control the parameter than the holding time when the consolidation pressure is invariable. The increase in the consolidation temperature caused an increase in tensile properties, but a decrease in the impact energy.…”

“…Using fibers produced from the same material, but with different drawing ratios, can enlarge the processing window. Bárány, Karger-Kocsis and coworkers [14][15][16]32] reported another novel approach that used the film stacking method to prepare the self-reinforced PP composites by taking the polymorphism-related difference in the melting range between the ! and " phases PP.…”

Modelling of polypropylene fibre-matrix composites using finite element analysis

“…Complicated geometries, loading conditions and material properties often do not yield analytical solutions, due to complexity and the number of equations. In this case, numerical methods are used for approximate solutions, but they still make some simplifying assumptions about the inherent microstructures of heterogeneous multiphase materials, one such method is finite element analysis (FEA) [8,9]. The finite element method is an alternative approach to solving the prevailing equations of a structural problem.…”

“…They avoid the abrasion to processing equipment that may occur with PP-glass fibre and other mineral filled composites. All-PP composites have been commercialized as PURE ® , a technology from Lankhorst Indutech bv of the Netherlands [8], Milliken and Company, Spartanburg, S.C., introduced Moldable Fabric Technology (MFT), and Curv, produced commercially in Gronau, Germany, by Amoco Fabrics and Fibers Co., a unit of BP Amoco. All-PP composites require a difference between the matrix-PP and the PP fibres that will allow the matrix to consolidate by fusion without changing the fibres, this difference maybe a PP copolymer or even differing orientation [9].…”