Additives antioxidant suppliers

A variety of methods for evaluating antioxidants in polypropylene has been developed during the past several years. Polymer producers, end-use manufacturers, additive suppliers, academicians, and others have developed widely disparate test methods, all of which presumably yield the same results—i.e., the test methods rate the antioxidants and antioxidant systems in the same relative order of effectiveness. Many of these test methods are useful tools in distinguishing unstabilized polymer, moderately stabilized polymer, and highly stabilized polymer systems. Today, all of the polypropylene producers offer highly stabilized polymers. Effective antioxidants are available from several additive suppliers. How does one select the best antioxidant or polymer formulation for a particular end use This paper compares the results obtained by various test methods used to evaluate the two basic types of oxidative stability, processing stability and end-use or environmental stability. The correlation or lack... 

Typical minimum requirements for the packaging necessitate the addition of other polymer modifiers. Prevention of discoloration requires addition of an antioxidant. The resin supplier is... 

Starting January 2003 GeoDeck boards were made without adding antioxidant, as the HDPE supplier had assured that the plastic had an unusually high amount of antioxidants. These boards were made until March-April 2003, and after that the manufacturing continued with another HDPE source but the additions of the antioxidant was not resumed. This was a dramatic mistake. Manufacturing without the antioxidant was continued until the beginning of October 2003. The plant QC system could not detect the problem because there was no procedure in place that would have been able to detect a low amount (or a complete absence) of antioxidants in composite materials. The procedure was developed and implemented in the plant QC system later (see below). 

In the presence of additives, both crosslinking and scission are usually affected e.g., antioxidants reduce both of these, whereas crosslinking agents predominantly enhance crosslinking [Makhlis, 1975 Sasaki et al., 1979 Charlesby, 1987 Carls-son et al, 1991 Feng and Ma, 1992 Kashiwabara and Seguchi, 1992 Lyons, 1992 Williams, 1992]. Lyons [1992] has pointed out that in the presence of antioxidants, chain scission, which is usually a unimolecular reaction, may be affected to a smaller extent than crosslinking, which is usually a bimolecular reaction. Most commercial polymers contain low amounts of antioxidants. Thus the results obtained with them may vary from batch to batch and supplier to supplier. 

The number and amount of additives incorporated in a resin vary with resin type and application. A polyethylene resin, for instance, may have only an antioxidant incorporated, or a colorant may also be added. A PVC resin may require several plasticizers, a filler, a heat stabilizer, and a colorant. There are many variations, and in most cases, the final resin formulation is considered by the manufacturer to be proprietary information. A confidentiality agreement may be necessary to make certain that the material meets regulatory compliance, unless the supplier can give the end-user sufficient information to make the determination. 

Mold-Release Agents Plasticizers Stabihzers Antioxidants PVC Heat Stabilizers UV Stabihzers Thermoplastic Materials Thermoset Materials Classified Directory of Suppliers (Primary Equipment, Auxiliary Equipment, Materials, Chemicals and Additives, Specialized Services)... 

Occasionally, one additive will interfere with the effectiveness of another. Therefore suppliers should ideally provide laboratory or case-history evidence of the durabUity of the precise grade proposed for future use, with all the ingredients, and not simply rely on data from earlier grades. In practice this is a counsel of perfection, because users cannot reasonably expect the latest advances in resins, Ught stabilizers, antioxidants, fillers, and so on and also 20 years test data ... 

Another consideration of pellets from a resin supplier is the inclusion of an additive for processing stabilization, generally an antioxidant. Although this additive is often included in first-generation pellets, the percentage is usually low and provides limited effectiveness when a significant amount of reprocessed material is blended into the mix. Of course, pellets from a resin supplier are generally more expensive than reprocessed pellets. 

One constant concern of additive suppliers is how to help their customers achieve higher production speeds. Ciba Specialty Chemicals makes the ease of addition of Irgastab Cable KVIO, a liquid antioxidant stabiliser for high voltage cable insulation, one of its selling points. It is used in conjimction with a peroxide crosslinking agent, and is said to allow increased cable extrusion speeds because it minimises gel formation. 

Liquid colorants can create problems in extrusion such as solids conveying problems. This can be avoided by using a porous carrier resin. Several resin suppliers (e.g., DSM, Akzo, Montell) now have porous carriers for use with liquid additives these can be colorants or other additives, such as antioxidants, peroxides, silanes, etc. Mixing can further be improved by starve feeding the extruder as discussed in Section 11.3.4.2.5. 

Typical minimum requirements for the packaging necessitate the addition of other polymer modifiers. Prevention of discoloration requires addition of an antioxidant. The resin supplier is typically required to meet a general performance specification however, die final use of the packaging may not be stipulated or considered when an antioxidant is chosen. Ultraviolet resistance is required for some packaging where extended sunlight exposure is expected. A common UV-inhibiting additive is carbon black. 

For product identification analysis of additives (as unintended markers) is a frequently used tool. Lang et al. [163] have examined PET samples of different suppliers by means of ToF-SIMS. Dependent on the origin, antioxidants and lubricants such as Irgafos 168, octylstearate, octylpalmitate, octylarachi-date and a contaminant (polydimethylsiloxane) were found on the PET surface. Galuska [186] has developed ToF-SIMS calibration lines for PIP, PBD, PE,... 

If the vitamin E movement in UHMWPE biomaterials was bom in Torino in 2003, then its conception occurred in Japan by Professor Naohide Tomita from the University of Kyoto. Japan has a history of early adoption of vitamin E both in packaging as well as in orthopedic implants. Vitamin E has been used in Japan as an environmentally friendly additive for polyolefins since the late 1980s [11]. In light of its acceptance as an effective antioxidant, a manufacturer from Japan (Nakashima Medical Co., Ltd., http //www.medical.nakashima.co.jp) was also the first supplier to produce UHMWPE blended with vitamin E for total knee replacements, and these implants have been in clinical use in Japan since 2006 [18] (Figure 16.4). The commercialization of vitamin-E-blended UHMWPE in Japan is largely based on the research efforts of Professor Tomita and Nobuyuki Shibata, who was a doctoral student at the time [1,19-21]. These studies have been recently summarized [18] consequently the contributions of the Kyoto research group are only briefly reviewed herein. 

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