Processing Performance Improvements Return to the techdata List

Technical parameters: Improvement of Processing Performance
The molecular chain of ultra high molecular weight polyethylene (UHMW-PE) resin is longer and susceptible to fracture by shear force, or heat degradation. Thus, the lower processing temperature, the shorter processing time and reducing its shear are necessary.
In order to solve the processing problems of ultra high molecular weight polyethylene (UHMW-PE), in addition to ordinary molding machinery for special design, it can also improve the resin formulations: blended with other resins or adding flow modifiers, so that it can process in ordinary extruders and injection molding machines, which is lubricated extrusion (injection).
Blending modification
Blending method to improve ultrahigh molecular weight polyethylene (UHMW-PE) melt flow is the most effective, easiest and most practical way. Currently, this technology is common in patent documents. The second component of the main used blending refers to the low melting point, low viscosity resin, such as LDPE, HDPE, PP, PET, etc., which is used frequently medium molecular weight PE (molecular weight 400,000 to 600,000) and low molecular weight PE (molecular weight <400 000). When the blend is heated to above the melting point, ultrahigh molecular weight polyethylene (UHMW-PE) resin will suspend will be suspended in the liquid second component resin to form the extrudable, injectable suspension material.
(1)blend with low, moledular weight PE
Ultra high molecular weight polyethylene (UHMW-PE) blends with low molecular weight LDPE (molecular weight of 1,000 to 20,000, 5,000 to 12,000 is preferred), so that the molding processability can be inproved significantly, but at the same time, tensile strength, flexural elasticity declined. HDPE can also significantly improve the ultrahigh molecular weight polyethylene (UHMW-PE) of the processing flow, but it can also cause the impact strength, wear-resisting  properties declining. For the mechanical properties of ultra-high molecular weight polyethylene (UHMW-PE) blending systems maintained at a high level, an effective way to compensate is to join PE nucleating agents, such as benzoic acid, benzoic acid, stearate , adipate, etc. can be improved by the PE crystallinity, size of spherulites fine homogenization and play strengthening effect, so as to effectively prevent the decrease in mechanical properties. Patent pointed out that the small little amount of wollastonite(whose particle size range is 5nm ~ 50nm, the surface area of ​​100m2 /g ~ 400m2 / g )nucleating agent is added to the ultra high molecular weight polyethylene (UHMW-PE) / HDPE blending systems, can be well compensated for the reduction of mechanical properties.
(2) Blending morphology
Ultra high molecular weight polyethylene (UHMW-PE) with a chemical structure similar to other varieties of PE, but in general melt mixing equipment and conditions, and their blends are difficult to form a uniform shape, which may be related to viscosity difference between components. Ordinary single-screw mixing get ultra high molecular weight polyethylene (UHMW- PE) / LDPE blend, the crystallization of respective components, can not form a eutectic, ultra-high molecular weight polyethylene (UHMW-PE) basically filling in the form LDPE is dispersed in the matrix. Melt prolonged treatment and refining of twin-roll presses mixing, the role has been strengthened between the two components, there are further improved performance, but still can not form a eutectic morphology.
Vadhar found that when using a two-step blending process, that is, first at a high temperature ultrahigh molecular weight polyethylene (UHMW-PE) melt, and then reduced to a lower temperature blending with LLDPE, which forms a eutectic blends. Vadher used method of  solution blending to be formed of co-crystal ultrahigh molecular weight polyethylene (UHMW-PE) / LLDPE blend.
(3)The mechanical strength of the blends
For the addition of the nucleating agent is not an ultra-high molecular weight polyethylene (UHMW-PE) / PE system, which will form a large spherulites during the cooling process, there is a clear interface between the spherulites, but the existence of internal stress in these interface caused by the different arrangement of the molecular chains, and thereby causes the generation of cracks, compared with the base polymer, the tensile strength of the blend is often decreased. Crack when subjected to external shocks will quickly along spherulite interface development leading to the final crushing, it is also cause a decline in impact strength.