Ultra-high Modulus Polyethylene Fibers Research Articles

Polyethylene-Ultra High Modulus Polyethylene Short Fibers Composites

Composites based on chopped ultra high modulus polyethylene fibers (UHMPE) and low density polyethylene (LDPE) were prepared in the melt state. It is shown that the UHMPE fibers do not melt during the preparation operations, and an im portant enhancement of the mechanical properties is obtained as a function of fiber content and length. The efficiency of these fibers was found to be comparable to those of Kevlar® fibers, and higher than those of glass fibers. An important transcrystalline region has been observed for all the fibers, however, its effect on their efficiency as a reinforcing agent is questionable. It is also shown that UHMPE fibers can advantageously replace Kevlar® fibers in some particular applications.

Induction time approach to surface induced crystallization in polyethylene/poly (ɛ-caprolactone) melt

The surface induced crystallization of poly (ɛ-caprolactone) (PCL) on an ultra-high modulus polyethylene (PE) fibre was investigated using a new approach based on the induction timeti. This approach allows estimation of the free energy difference function Δσ as it appears in the theory of heterogeneous nucleation. The classical approach based on the rate of heterogeneous nucleationl is not applicable to transcrystallization because the nucleation density at the fibre surface cannot be measured. A relationship betweenl andti is proposed and a theoretical justification is presented. Good agreement between the two approaches is obtained for a verification case where bothl andti can be determined. A transcrystalline growth rate study yields an estimate of the parameter σσe for PCL of 680 erg2cm−4. The maximum growth rateg* is also obtained. The results obtained indicate the influence of certain parameters on the appearance of transcrystallinity. It is also shown how the interfacial morphology can be controlled by the knowledge of the variations of the induction time with temperature.

Surface treated polyethylene fibres as reinforcement for acrylic resins

The use of poly(methyl methacrylate) as a bone and dental cement material over several decades has provided us with experience related to processing and performance. A recognized disadvantage of such cements is their mechanical behaviour, expressed by low crack propagation resistance, impact strength, fatigue resistance and reduced fracture toughness. Many attempts have been made to resolve these problems either by modifying the poly(methyl methacrylate) chemical structure via copolymerization or incorporating reinforcing additives. The latter is of great importance, because it can lead to the preparation of composite materials with considerably improved performance. Besides reinforcement, the incorporation of additives, such as fibres, results in better processing characteristics e.g. lowers polymerization exotherm. In this work, poly(methy) methacrylate) reinforced with Tekmilon® ultra high modulus polyethylene fibres was studied, focussing on the interfacial bonding between matrix and reinforcement. Some finishing agents were used to treat the fibres and their efficiency was mainly evaluated through the effect on the mechanical properties of the composite material prepared.

Fiber-matrix Adhesion of Hydroperoxidized and Corona Discharge Treated Ultra-high Modulus Polyethylene

Controlled hydroperoxidation of commercial ultra-high modulus polyethylene (UHMPE) fibers has been used to provide grafting sites for the styrene crosslinking reaction of an unsaturated polyester resin. This has provided a covalent bond between the reinforcing fiber and matrix of the composite material so maximizing the interfacial adhesion. By using chemiluminescence and X-ray photoelectron spectroscopy to determine the nature of the oxidized surface of UHMPE, the treatment was optimized for hydroperoxide formation. This yielded the highest fiber-resin bond as determined by yarn pullout force. Commercial corona discharge treatment resulted in a lower bond strength which was attributed to a weak outer layer of highly oxidized material. This produced fiber slippage as indicated by scanning electron microscopy, in contrast to matrix cracking and interior shear of the fiber on pullout of the hydroperoxidized material.

A study of the adhesion of drawn polyethylene fibre/polymeric resin systems

The effect of plasma etching and chromic acid treatment on the surface adhesion of ultra-high modulus polyethylene fibres to an epoxy resin has been studied. The adhesion was determined from pull-out tests, and showed a significant improvement for both plasma and acid treatments. The mechanism of failure, however, appeared to be different in the two cases. Untreated and acid-treated monofilaments showed a fairly smooth surface and failure of the pull-out samples involved sliding along the monofilament/resin interface. Plasma treatment, on the other hand, produced a remarkable structure on the monofilament surface, into which resin penetrated to produce a mechanical keying between monofilament and resin. Failure in the pull-out test then involved rupture within the monofilament.

Direct measurements of crystallite size distribution in ultra-high modulus polyethylene fibres

Direct measurements of crystallite size distribution in ultra-high modulus polyethylene fibres