INTRODUCTION TO POLYMER ADDITIVES AND STABILIZATION Bobbijo van Beusichem, Ph.D., Senior Staff Scientist, Expert Services, Michael A. Ruberto, Ph.D., Head of Regulatory Services, NAFTA, Expert Services Ciba Expert Services, Ciba Specialty Chemicals Introduction Polymer Auto-oxidation Cycle Role of Additives Stabilizers (cont’d) Phenolic AO Oxidation Chemistry R-H Melt Processing Energy . O (Polymer) O OH O• Polymers are used in ALL aspects of our lives, including pharmaceutical packaging and Catalyst Residues • Most polyolefins contain one or more antioxidants Additives provide to Plastics: + RO• medical device preparation. HO CH CH O CH -] -C + RO• at levels of 0.05 – 0.10% 2 2 2 4 -ROH -ROH Oxygen Stabilization ¾ Primary antioxidants are generally radical Irganox 1010 R R Cycle II Cycle I scavengers or H-donors H R* R • R R Quinonemethide RO • + • OH ROO • To retain the original molecular architecture of the – i.e. hindered phenols such as BHT, Irganox 1010, or Irganox 1076 HO CC OH R • polymer under the effect heat, light etc. Coupling + – Long-term protection for the polymer ROOH + 2 RO• and ¾ Secondary antioxidants are typically O O -2 ROH Path of R • Alkyl radical P Degradation RO • Alkoxy radical hydroperoxide decomposers Without the use of the proper stabilization package, polymers will degrade. Interaction ROO • Peroxy radical O R R ROOH Hydroperoxide Functionalization – i.e. trivalent phosphorus compounds with oxygen and light can cause significant degradation of the polymer. These degradation O products are potential leachables and extractables. such as Irgafos 168 O CC Often, blends of stabilizers will be used to protect the Auto-oxidation: Most labile hydrogens To provide additional attributes to the polymer which – Process stabilization (protects the primary Irgafos 168 polymer at various stages throughout the polymer lifecycle. add value for end use application. AO against decomposition during processing) Stilbenquinone – An organophosphite, may be used as a short-term Polyamide: -CO-NH-CH - {Bright Canary Yellow} antioxidant to protect the polymer during the high 2 temperature and shear conditions of processing. Chemistry of Phosphite Polyester: -CO-O-CH2- – A phenolic antioxidant may then be used for long-term protection. BHT Oxidation Chemistry Polyacetal: -O-CH2-O- Extending Beyond Polymer Hydrolysis Additives may be incorporated into a product either as neat material or as a concentrate or masterbatch. Unsaturated system: -CH=CH-CH - Some additives are designed to react and transform 2 Protection OH OH OH – A masterbatch is polymer resin containing a high For example, an active phosphite, such as Irgafos 168, [Oxid] [Oxid] concentration of the additive to be incorporated. Polypropylene/ -CH2-CH-CH2- can undergo hydrolysis: Polyethylene O – The polymer resin may contain its own stabilization R = Customer Product Properties O H O OOH package, which may or may not be different than the Customer Product Properties Antimicrobials Protection P(OR)3 + H2O (RO)2P-H + ROH package used in the final product. (More potential Lit.: F. Gugumus in Plastics Additives, Gächter & Müller, Ed., 3rd Ed., Ch. 1 Antistats OH leachables and extractables!) Colorants OH O O Oxidative = Some additives are designed to transform during use. = Decarboxylation – An organophosphite, for example, will be oxidized to form the phosphate. Products of polymer degradation UV Absorbers (RO)2P-H + H2O RO-P-OH + ROH Polymer Properties _ O OH – In this case, BOTH the phosphite and phosphate are potential leachables and extractables. Anti-fogging additives Alcyl radical (R ) (carbon centered free radical) Extension O H Polymer stabilization is a dynamic process resulting in ever- Optical Brighteners Active = changing transformation and degradation products – Peroxy radical (R-OO ) (oxygen centered radical ) Slip Agents -4H· O products: Light Stabilizers RO-P-OH + H OHPO + ROH O Diphenoquinone all potential leachables and extractables. Intermediates 2 3 3 _ Oxidative Coupling of degradation Alkoxy radical (R-O ) Additives can also provide special effects or properties to Polymer Properties H the polymer system. Hydroperoxide (R-OOH Æ R-O + OH) Plasticizers (hydroxy radical) Retention – Benzophenones or benzotriazoles can provide Phenolic Alcohol (R-OH) Organophosphites UV protection to a polymer. Inactive AOs Relative Discoloration products: Aldehyde (R-C-H) Conclusions – Phenylglyoxylates can serve as photoinitiators in Influence • a UV curable coating. organoleptics O Polymers stabilized with phenolic AO’s can be susceptible to discoloration if the system Ketone (R-C-R) Additives can provide additional properties or effects beyond stabilization. is “abused” • Use of the proper stabilizer package can provide protection to the polymer. – Colorants – dyes or pigments used to impart a particular color Modified O to a polymer system. properties Polymer Calendered Polyolefin Sheet ¾ A combination of short-term and long-term stabilizers may be employed. Each of these compounds poses the potential for leachables and – Primary and secondary antioxidants extractables. Polymer Stabilization Stabilizers • Additives can also impart particular properties or effects to a polymer system What are the differences between Additives, • Good stabilization will reduce formation of aldehydes, ketones, and color bodies ¾ Colorants Degradation of Polyolefins Stabilizers, Modifiers and Fillers ? • Some stabilizers, which can terminate alkyl radicals, are especially effective ¾ Photoinitiators Tape Technical preparation of “purest” polymer is simply not possible! Additives are ingredients added to the polymer to stabilize, (vitamin E, lactone, hydroxyl amine) removed ¾ Antistats Structural defects and impurities can not be excluded modify or enhance it’s performance • Systems for gamma irradiation have been developed ¾ Antimicrobials Organic materials undergo degradation in the presence of Oxygen. Stabilizers are used to maintain the polymer’s strength, flexibility • Systems for reduction of organoleptics from slip agents are under development Forming peroxides, alcohols, ketones, aldehydes, acids, peracids... and toughness; in other words, the attributes of the polymer’s • Many additives will transform and/or degrade during use. original molecular architecture • Auto-oxidation can be suppressed by the use of radical scavengers Oxidation is assisted by: Energy (e.g. mechanical stress, heat, light) Outside of Polyolefin Sheet Roll Sample removed from sheet ¾ Each of these products must be taken into consideration when evaluating leachables metals/-ions (catalyst residual, impurities, co-add.) Modifiers improve / alter the polymer’s performance; e.g., Slip (area where tape held roll together after unrolling a few loops and extractables. Agents, Antistats, Antiblocks, Processing Aids, Fillers is visible) Oxidation can affect mechanical properties • Stabilization is a dynamic process Discoloration, rougher surface, decreased tensile strength Fillers, such as SiO2,CaCO3, Talc, or TiO2 are used to improve BHT and Irganox 1076 undergo similar chemical physical properties, or dilute the matrix with something less ¾ Transformation and degradation products must be considered along with the intact Oxidation of hydrocarboncompounds proceeds autocatalytically expensive than the polymer itself transformations leading to chromophore chemistries. additives as potential leachables and extractables. Poster prepared at www.SciFor.com.