Everyone is trying to differentiate their products to get an edge in the market place. Global competition is hotting up and additives offer a way to enhance products at a reasonable cost. Applied Market Information (AMI) brought together leading experts to debate the latest developments at its conference on Polyolefin Additives held in April 2008 in Cologne, Germany.
Polyolefin additives range from chemical stabilisers (antioxidants, heat stabilisers, UV absorbers, UV stabilisers, gamma radiation stabilisers and metal de-activators) to surface active agents such as adhesion promoters and anti-block agents. Noru Tsalic of AMI estimates that the market for chemical stabilisers will grow by 5% per year to 2010, with an increase in volume share in Asia for all types of additives in the same period.
Polypropylene is increasingly being used in applications requiring sterilisation. This can affect the mechanical and optical properties. Borealis Polyolefine has been testing the effects of nucleating agents and copolymers to preserve the properties of sterilised cast PP film. Carmel Olefins has shown that a broad molecular weight distribution (MWD) and nucleating agents increase the rate of crystallisation of PP – the company is developing new PPs using Basell’s Spherizone technology.
The history of antioxidants was reviewed at the conference by Songwon International: aromatic amines were used but were toxic and lacked food approval (now discontinued), then came metal dithiocarbamates (e.g. ZDMC) with discoloration and toxicity issues, followed by metal soaps (e.g. Songstab SZ-210), sterically hindered phenols, phosphites and hydroxylamines.
BASF is developing new light stabilisers including a low aggregate HALS for applications ranging from artificial grass to packaging films (Uvinul 5050 H). It provides good heat sealing properties and less colour shift with alkaline-sensitive pigments. It also offers less interaction with PPAs in film (no effect on melt fracture). Ciba has worked on a new phenol-free light stabiliser for PP fibre (Irgastab FS533) offering good light and heat stability, with lower cost than current additives. DuPont has an ultrafine titanium dioxide which both scatters and absorbs UV light: Light Stabilizer 210 is used in protective films giving transparency and UV protection. Cytec has a series of stabilisers for different applications, for example, black exterior automotive TPO has been compounded with 1.5% carbon black, 15% talc and 0.3% CYASORB®UV-3808PP5 and CYASORB THT has been used in greenhouse films.
PP degradation is mainly due to chain scission: stabilisation aims to prevent discoloration, permit processing and give long term heat stability and extraction resistance. PE degradation is primarily due to crosslinking, with some to chain scission and stabilisation depends on the end use. Albemarle provides primary and secondary antioxidants, HALS and chemical UV absorbers and has studied combinations of additives for different uses and polymer processing conditions.
Smith and Nephew Orthopaedics has looked at the issue of oxidation of UHMWPE in hip implants – crosslinking reduces wear but generates macroradicals that can react with air. The natural antioxidants beta-carotene, vitamin E, naringenin and curcumin were tested and all except the beta-carotene were effective antioxidants.
Wells Plastics provides specialist antimicrobial masterbatches. Organic antimicrobials generally comprise small molecules that migrate/diffuse onto the surface with additive in the polymer acting as a reservoir. Inorganics are usually metal ions, commonly silver.
Timcal has specialist graphite for increasing the thermal and electrical conductivity of polyolefins. It has also had some success with nanocomposite development.
Regulation is a big factor affecting existing and new chemical products, particularly in Europe. REACH comes into full effect in June 2008 and SafePharm has examined the work required for registration by polymer and additive suppliers to Europe, including data and cost sharing in the testing required. The latter depends on volumes of imports. Food contact legislation covers conveyor belts to food packaging, there are changes expected soon on active additives, plasticisers in lids and antimicrobials according to Keller and Heckman.
The purity of antioxidant supplies can be critical in applications such as potable water contact and this has been examined by Norner Innovation. A new test method (prEN 15768) is expected to be put forward in 2008 to ensure that polymer materials do not contaminate the water supply.
Chemtura has a new liquid organophosphate antioxidant, DVS005, being developed as an alternative for tris nonylphenyl phosphite (TNPP). Global registration and food contact approvals are pending.
Rika has a new low dosing, non-acetal sorbitol clarifier for PP providing good thermal stability.
The Universität Der Bundeswehr Munchen has been carrying out experiments with polymer processing additives (PPAs). These have higher adhesion properties and replace the polymer on the die surface. Historically, hydrophobic materials such as fluoropolymers and silanes have been used. The university has been testing hydrophilic PPAs based on PEG, which is relatively cheap and environmentally friendly.
Talc is commonly used as polyolefin reinforcement. Ultrafine particles of 0.7 micron diameter from Rio Tinto Minerals have also been used for PP nucleation.
Polyolefin Additives 2008 brought together experts in polymers, compounding, masterbatch, additives and users of the materials. AMI has plans to run this successful event again in 2009, focusing on the needs and issues for the industry.
Posted April 22nd,2008