Low-temperature impact properties

VLDPEs, with their very good low-temperature impact properties, are of interest in frozen food packaging. By 1998 the market for UHMWPE materials was estimated at 65 000t.p.a. of which Ticona had about half the market share. 

In the search for substitutes, other considerations than just sulfide stability have to be considered. These include the possible interference of the newly introduced element with other steel porperties, the plasticity of the new sulfides, the physical alloyability of the additive and, of course, the cost effectiveness of the additive. Zirconium and titanium interfere with other properties of the steel because of the excessive stability of their nitrides. Figure 9, and carbides. Figure 10. Although considerable usage of these two elements has played a part in sulfide substitution — over 500 metric tons of nuclear zircalloy scrap were used in — it appears that their role will progressively fade away primarily because of poor low temperature impact properties of steels treated with Zr and Ti. 

PP/PIB miscible ( ) blends low temperature impact properties Ranalli, 1958... 

Predesigned particles of impact modifiers are based on core-shell technology. Core is involved in impact modification and shell improves adhesion between PVC and impact modifier particles.Three major combinations are used methacrylate-butadiene-styrene, MBS, which has a core made out of butadiene-styrene copolymers and shell made out of methylmethacrylate-styrene copolymer, acrylic impact modifiers, AIM, which have a core made out of acrylic and shell from polymethylmethacrylate, and silicone-acrylic have multilayer structures with silicone-acrylic in the core. MBS has excellent compatibility with PVC, similar to ABS, which is used as an impact modifier of PVC, as well. In both cases of ABS and MBS, weather resistance is lacking, therefore they are used for indoor applications only. At the same time, MBS gives translucent to crystal clear products, whereas with AIM, only translucent products are possible. In order to improve optical properties of AIM, it has to be reformulated. For transparent products, the core is made out of acrylic-styrene copolymers. Comparing silicone and all acrylic impact modifiers, PVC containing silicone-based products has superior low temperature impact properties. The incorporation of silicone into an acrylic impact modifier provides excellent weatherability, and thermal stability. It has shown improved retention of impact after outdoor weathering in PVC. ... 

Acrylic impact modifiers will continue to grow with the growth of rigid PVC in the construction market. Product development in this market will target improved low-temperature impact properties to reduce failures, lengthen the installation season, and lower cost. 

Low levels of TPU have been blended with polyesters, such as polybutylene-terephthalate (PBT) and polyethleneterephthalate (PET). Blends of 10 to 30% TPU contribute to the toughness and low-temperature impact properties of PBT and PET [67]. 

The ethylene content of EPR will strongly affect its glass transition temperattue and its adhesion with PP matrix which, in turn, will modify low-temperature impact properties of the copolymer. 

Products requiring higher fill temperatures have layers of HDPE or PP. Heat-sterilized containers heated up to 121°C employ PP, although HDPE can be used for retort temperatures up to about 112°C. HDPE has better low temperature impact properties than PP, which may be important in distribution and warehousing. HDPE and PP are more difficult to thermoform than HIPS PP usually undergoes solid phase forming Fillers are sometimes added to improve polyolefin stiffness and formability. 

Ethylene vinyl acetate copolymer (EVA) is a low density polyethylene copolymer with excellent low temperature impact properties. The higher the level of vinyl acetate, the greater the flexibility of the material. Colorants, flame retardants, and foaming and antistatic agents may be added to polyethylene for specialty applications. Comparisons with other resins are given in Table 2. 

The new metallocene ethylene elastomer TPOs now used in the automotive industry possess better low-temperature impact properties and better lifetime durability than soft vinyl plastic. Some new proprietary ethylene-octene copolymer elastomers are being used as TPOs as well, and a new introduction of an ethylene-butene copolymer has been made as well. 

HDPE, and more recently, modified polyethylene of lower density, are used in gas distribution systems for many important reasons, including economic shaping, ability to withstand both the internal and external loads, good low-temperature impact properties and relative impermeability to the gases... 

Since all specimens exhibited ductile fracture it was possible to compare used and unused polymers. It was noted that, although the materials had been in service for ten years before recycling, the low-temperature impact properties had not deteriorated. As before, it is difficult to compare the values determined for injection-moulded test specimens with those exhibited by the original tank material and those specified by the quality order since the test specimens were only 3 mm thick, compared with the average thickness of a tank, which is between 5 and 8 mm. 

The results for nitrogen are quite clear. Addition of 0.10 nitrogen to an alloy containing 0.08 carbon caused a strong increase in austenite stability. However, the low-temperature impact properties were decreased in both the unwelded and welded condition. This is opposite to the effect noted above for the other alloying elements. 

Impact Properties The impact properties of rigid P VC improve as resin molecular weight increases. There is also a similar improvement in low-temperature impact properties. In order to achieve the impact property improvements afforded by higher-molecular-weight products, the resin must be properly fused. One must remember that many impact resistance failures in rigid PVC are not caused by formulation errors or poor resin selection choices, but by process-related issues. 

Good abrasion resistance and low temperature impact properties highest stiffness and strength of PE grades resistant to stress cracking. 

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