Effect Of Peroxide Content Research Articles

Evaluating storage conditions on the effect of peroxide content in acrylonitrile

AbstractThe content of peroxide in acrylonitrile is critical for the production of polyacrylonitrile‐based carbon fibers. Peroxide‐free acrylonitrile is used as a blank solution for testing the peroxide content of acrylonitrile, which storage conditions are important to the test. Of course, for the change of peroxide content in acrylonitrile stored for a period of time has an effect on the production of carbon fiber. In order to study the effect of storage conditions on peroxide in peroxide‐free acrylonitrile and acrylonitrile, the changes at refrigerator and room temperature were studied, respectively. Studies have shown that storage at temperatures below 20 °C for 3 months hardly affect the use of either peroxide‐free acrylonitrile or acrylonitrile. The experimental results obtained are useful for practical production and testing, which can improve the accuracy of testing and stability of production.

Rheological Properties and Melt Spinning Application of Controlled-Rheology Polypropylenes via Pilot-Scale Reactive Extrusion.

Based on pilot-scale twin-screw reactive extrusion, the structural and rheological properties of controlled-rheology polypropylenes (CR-PPs) are investigated, where the effects of peroxide content and extrusion conditions such as screw configuration, extrusion temperature, and screw speed are prioritized. The active chain cleavage reaction by a small peroxide content of less than 600 ppm inside the extruder gradually increases the melt index and narrows the molecular weight distribution of CR-PPs, thereby affording favorable properties that are applicable to the fiber spinning process. The mechanical properties of CR-PPs are slightly degraded owing to the generation of unsaturated chain ends during the reactive extrusion, which suppresses crystal growth. Under all extrusion conditions, the chain scission and thermal degradation of polypropylene samples occur actively in the harsh twin-screw extruder compared with those in the mild twin-screw extruder. Finally, it is confirmed that CR-PPs can be suitably applied to the melt-spinning process for staple fiber production, thereby guaranteeing a more stable spinning process window against draw resonance instability.

Cross-Linking of Rubber Matrices with Dicumyl Peroxide and Zinc Dimethacrylate. Part II: Effect of Peroxide Content

Cross-Linking of Rubber Matrices with Dicumyl Peroxide and Zinc Dimethacrylate. Part II: Effect of Peroxide Content

Effect of Peroxide Content on Morphology and Properties of Thermoplastic Vulcanizates Based on PP and NR

Thermoplastic vulcanizates (TPVs) of natural rubber (NR) and polypropylene (PP) (60:40) containing various dosages (0.5-5.5phr) of peroxide were prepared using a Haake Rheocord. The effects of peroxide content on the crosslink density, thermal behaviors, morphology, mechanical and rheological properties of NR/PP TPVs were studied. The crosslink density of TPVs increased with increasing of peroxide content. However, the tensile strength, tear strength and elongation at break obtained the maximum values when 2.5phr peroxide was added, which was ascribed to the presence of smallest particle size of crosslinked rubber phase at this peroxide content. It was proposed that the effect of DCP, which not only initiated crosslink reaction in NR phase, but also degraded the polypropylene molecules, played an important role in determined the morphology and properties of TPVs. The viscosity of TPVs decreased with shear stress, indicating pseudoplastic nature of the TPV samples. The elastic modulus of the samples gradually increases with the increase in DCP content.

The effects of peroxide content on the wear behavior, microstructure and mechanical properties of peroxide crosslinked ultra-high molecular weight polyethylene used in total hip replacement

The wear of the ultra-high molecular weight polyethylene (UHMWPE) acetabular components and wear debris induced osteolysis are the major causes of failure in total hip replacements. Crosslinking has been shown to improve the wear resistance of UHMWPE by producing a network structure, resisting the plastic deformation of the surface layer. In this study organic peroxides were used to crosslink two different types of UHMWPE resins, using hot isostatic pressing as the processing method. The effects of peroxide content on the different properties were investigated, along with the effect of the crosslink density on the wear behavior. An increase in peroxide content decreases the melting point and the degree of crystallinity, which results in a decrease in the yield strength. The ultimate tensile strength remains essentially unchanged. The molecular weight between crosslinks decreases with an increase in the peroxide content and reaches a saturation limit at around 0.3-0.5 weight percent peroxide, its value at the saturation limit is a function of the virgin resin used for processing. The wear rate decreases linearly with the increase in crosslink density.

Effect of network heterogeneities on the physical properties of nitrile rubbers cured with dicumyl peroxide

AbstractThe scope of this study is to continue our earlier studies on the peroxide curing of diene elastomers. The effect of peroxide content and temperature on the curing and mechanical properties of NBR and H‐NBR rubbers with different acrilonitrile content was evaluated. Experimental evidence indicates that saturated rubbers behave as expected whereas in unsaturated nitrile rubbers abstraction of allylic hydrogen and addition to the double bonds can act as mechanism of crosslinking, the weight of each mechanism is dependent of DCP content and curing temperature. The addition mechanism produces densely crosslinked zones or clusters, generating a heterogeneous network with effect on the vulcanizate properties. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 3377–3382, 2007

Effect of fat content on protein fractions and textural properties of minced cod flesh in the course of frozen storage

In this study minced cod flesh, with the addition of 4%, 8% and 10% cod liver oil, was maintained in frozen storage for periods of up to 12 months. The changes in protein fraction of the tissue was determined during frozen storage and found to be dependent on lipid content and rate of freezing. The effects of peroxide content, carbonyl compounds and lipid fractions on the solubility of myofibrillar proteins in cod muscle tissue, and the changes of cod mince consistency arising from changes in protein fraction and lipid content in frozen storage, are discussed.