Self-Reinforced Plastics
“Self-reinforced plastics are a new family of composite materials, where the polymer matrix is reinforced by highly oriented polymer fibres, usually derived from the same polymer. Self-reinforced plastics (SRPs) have enhanced strength and stiffness compared to unreinforced plastics and they have improved recyclability and reduced weight compared to glass fibre-reinforced plastics. They also have outstanding impact energy absorption and the absence of abrasive fibres has advantages in terms of handling and tool wear.”
“To date, this technology has most commonly been applied to polypropylene (PP), which has a good balance of properties and is relatively low cost but has limited performance at elevated temperature.”
“There are two main techniques for producing self-reinforced PP materials, namely hot-compaction or co-extrusion. In the hot-compaction process, developed in 1989 at the University of Leeds, fibre fabrics are stacked together and consolidated by applying heat and pressure in a static press or, on an industrial scale, a double belt press. The process conditions are controlled precisely so that just the surface of the fibres melt and this molten polymer forms the matrix phase of the composite. In the coextrusion process, PP fibres are coextruded with a thin layer of a polypropylene-polyethylene copolymer, which has a lower melting temperature than the homopolymer fibre. On application of heat and pressure, the copolymer surface layer melts to form the matrix phase. Both processes have recently been commercialised and a number of SRPP materials are available, either as preconsolidated sheets, woven fabrics or tapes.”
“There are a wide range of potential applications for SRPs including:
• Automotive – body panels, parcel shelves, under-shields, load floors
• Off-road vehicles – high-impact exterior panels
• Marine – personal watercraft
• Sports – helmets, pads, guards
• Leisure – suitcases, loudspeaker cones
• Personnel protective equipment – safety helmets, anti-ballistic shields
• Medical – orthoses, temporary supports
• Construction – shuttering, formwork “
Recent US Patents
2/15/2011
7,887,726
Self-Reinforced Composite made of Recycled Materials and Process of making the same.
Tsai of Novana, Georgia, developed a a self-reinforced composite of a recycled fiber having a Young's modulus at least about 500 MPa in a recycled thermoplastic matrix from the carpet and automotive industries. The process is based on melt-blending recycled immiscible polymers, phase-migration fiber spinning the recycled immiscible polymers to form a fiber surrounded by a second recycled thermoplastic polymer, and (c) drawing the fiber to form a high modulus fiber. (RDC 8/26/2011)
Recent Journal Articles
Repeated low energy impact behaviour of self-reinforced polypropylene composites
(216-221) Polymer Testing 30 #2 (2011)
Aurrekoetxe et al of the Mondragon Unibertsitatea, Spain studied the repeated impact behaviour of self-reinforced polypropylene composite by tensile impact and instrumented falling weight tests. The nature of the tapes is highly anisotropic with strain hardening failure. Plastic deformation of the tape is the dominant mechanism, and the resulting penetration mode is a highly localised “star”-shaped hole. Damage and perforation thresholds are 5 J and 31.4 J respectively. Impact fatigue life exceeds 500 impact events up to 13 J, but drops sharply for 14 J. Strain-hardening is the origin of the trend of peak load increase and plastic deformation decrease with impact events. As a consequence, the amount of energy absorbed by each impact is reduced. However, when tape breaking takes place the absorbed energy increases up to perforation. (RDC 3/89/2011)