Kaan Bilge

Poly(propylene)/waste vulcanized ethylene- propylene-diene monomer (PP/WEPDM) blends prepared by high-shear thermo-kinetic mixer

Polypropylene (PP)–waste elastomer blends are particularly attractive as an economical way of producing sustainable materials, relieving the stress on the environment. Although PP is a commodity thermoplastic finding employment in various applications, its relatively low impact strength might be a significant factor limiting the variety of uses in many industries. Extensive consumption of thermoset elastomers has been a worldwide waste disposal problem. Here, we describe a facile, economical method for reuse of waste ethylene-propylene-diene monomer (EPDM) rubber to produce impact resistant blend materials with the PP via a high-shear thermokinetic mixer. In these blends, waste EPDM was used in various concentrations ranging from 20 to 80 wt%, as the remaining part, PP acts as a carrier matrix or a physical binder depending on the concentration in the blend. Briefly, fivefold increase was achieved in the impact resistance of PP by the addition of 60 wt% EPDM waste. The blend with 80 wt% waste EPDM shows characteristics similar to a thermoplastic elastomer. The conclusion of the study is that the blending method is quite effective to produce high-performance blend materials consisting of high concentrations of thermoset waste which addresses the worldwide disposal problem of waste thermoset rubbers.

Low Density Polypropylene/Waste Cellulose Fiber Composites by High-Shear Thermo-Kinetic Mixer

Abstract Achieving an appreciable weight reduction in PP based composite materials, particularly the ones reinforced by glass fibers, is quite challenging while enhancing their mechanical properties and fullfilling other enviromental concerns. To address this issue, low density composites of Poly(propylene) (PP) and waste cellulose fibers (WCF) were produced by high-shear thermo-kinetic mixer. This technique facilitates the ease of processing for the mass production of such composite materials due to the availability of high shear rates and relatively short processing times during manufacturing. The structure-property behavior of the molded samples was investigated as a function of WCF content. Briefly, one-fold increase in elastic modulus, 18 % increase in tensile strength, 87 % increase in flexural modulus and 27 % increase in flexural strength of PP were achieved by the addition of 30 wt.% WCF. The significant enhancements in mechanical properties were mainly attributed to the homogeneous dispersion of intrinsically stiff WCF filler in the PP matrix as a direct result of the high-shear mixing. These results mainly suggest that waste cellulose fibers can be used as an effective reinforcing agent in PP matrix instead of highly dense, non-renewable and non-biodegradable fibers, such as glass fibers, that prevents further stresses on the environment. Along with this, the reuse of waste cellulose fiber in PP matrix, particularly at high concentrations like 30 wt.%, evenly corresponds to the reduction of total PP consumption for PP based composite production. The main conclusion of the study is that the extensive blending technology gives us the ability to produce high performance thermoplastic based composite materials as well as addressing the world-wide waste disposal problem by reusing of natural wastes, which is a great opportunity to ensure sustainability and reduce enviromental and economical costs for many industries.

Interlayer toughening mechanisms of composite materials

Abstract Interlayer toughening in polymer–matrix composite materials can address the usual suspects in regard to the failure of laminated composites. Issues contributing to poor interlaminar strength and toughness can be delayed or eliminated by interleaving, which also suppresses matrix cracking, whether the root cause of delamination is isolated or synchronous. The interlayers/interleafs are considered herein as the additional design features, enabling tuning of the ply-to-ply interfacial (interlaminar) regions. A comprehensive literature review is presented for different interleaving strategies, with a special focus on nanofibrous electrospun interleafs. A road map and a series of examples are also discussed for effective incorporation of the nanofiber interlayers/interleafs into the laminated composites. Toughening mechanisms in the presence of electrospun nanofiber interleafs are shown to be effective under both in-plane and out-of-plane loading. Specifically, epoxy compatible poly(styrene-co-glycidylmethacrylate), P(St-co-GMA), and P(St-co-GMA)/MWCNT nanofibrous interlayers incorporated into carbon/epoxy laminated composites are exemplified for enhancing mechanical behavior under longitudinal and transverse tension, open-hole tension, three-point bending and end-notched flexural tests. Moreover, the working mechanism of these interlayers under in-plane loads is further elaborated by the custom design tensile tests of (0 2 /90 4 ) s interleaved laminates, backed-up by cracking-sound recording and analysis.