FACT SHEET K0027 Europe/Africa. Ageing Characteristics of KRATON G Compounds

Transcription

1 FACT SHEET K0027 Europe/Africa Ageing Characteristics of KRATON G Compounds

2 Introduction The resistance of polymers against oxygen, UV and ozone attack is very important in a number of end-use applications. During manufacture, antioxidants are added to the KRATON G Polymers to provide protection during transport and storage. However, specific stabiliser packages have to be added to compounds to tailor their ageing resistance to the specific end-use requirement. Degradation of elastomers is a result of polymer bond oxidation activated by mechanical stresses, high temperatures, ultraviolet radiation and chemical reactions. It can also be catalysed by the presence of and contact with metals. The degradation pathway is shown in Figure 1. Degradation results in a deterioration of mechanical properties, changes in melt flow characteristics and discolouration. Antioxidants are thus used to halt the degradation process. There are a variety of antioxidant types: primary, secondary or radical scavenging agents. Often a combination of these antioxidants is used because of synergistic effects. Figure 1: The degradation pathway of Elastomers RO + H2O RO + OH +RH RH Light, Heat Initiation R +O2 ROO UV Absorbers Radical scavengers e.g. Sumilizer GS/Irganox 3052 Primary AO e.g. Irganox 1010 Light, Heat, Catalyst ROOH +RH Secondary AO e.g. TNPP KRATON G Polymers have a high resistance against heat/ozone compared to SBS polymers due to the fully saturated rubber mid-block. There is a strong phase separation between the rubber EB mid-block and styrene end-blocks of KRATON G Polymers. KRATON G compounds are a unique class of material, often consisting of KRATON G Polymers, a plasticiser and other polymers. The EB mid-block, the polystyrene phase, and all other compounding ingredients have to be well stabilised. The choice of the antioxidant package will depend on the nature of the compound (natural or black), the intended application (outdoor or indoor) and the type of the required ageing test (UV, Florida). page 2 of 7

3 UV-light stability of KRATON G compounds Traditionally, UV stabilisers such as Tinuvin are added to KRATON G compounds in order to restrict or prevent degradation caused by environmental parameters such as light, air and heat, to ensure adequate end-use durability. Physical and optical performance after UV treatment or hot air ageing have been evaluated using Tinuvin 326 and 327 as stabilisers. Table 1 lists the results of tensile tests 1, weight loss, linear shrinkage 2 and YI 3 on cast films based on KRATON G 1650 compound mixed with oil at a ratio of 1/1. Table 1: Properties of oil extended KRATON G 1650 compound cast films Composition (pbw) Irganox Tinuvin Tinuvin Initial properties Tensile strength MPa Elongation % YI Heat aged at 70 C 1 week, weight loss % <0.10 < linear shrinkage % YI weeks, weight loss % linear shrinkage % YI UV light aged, 3 weeks Tensile strength MPa * Elongation % * YI *Degraded, not measurable After heat ageing at 70 C for respectively 1 to 12 weeks, weight loss, linear shrinkage and YI changes showed little difference but Tinuvin 327 tended to be marginally better overall. (1) Cast films dumbbells are prepared according to ASTM D412, conditioned at 23 C, 50% humidity for 16 hours. (2) Measured after 2 months' hot air ageing. (3) YI: yellowness index according to ASTM E313. page 3 of 7

4 The real effect of the UV stabiliser was seen in the stress/strain properties after UV-light exposure for 3 weeks. The non-stabilised sample degraded completely with severe discolouration whereas Tinuvin 327 stabilised films showed the best overall retention. The effect of Tinuvin 327 on the UV light and heat ageing stability has been evaluated in, containing Irganox 1010/DLTDP (0.2/0.2 phr 4 ). The results are summarised in Table 2. Table 2: Properties of KRATON G 2705 compound with and without Tinuvin 327 after 2 months hot air ageing at 120 C phr Tinuvin MD 5 PMD MD PMD Tensile strength, MPa (181) 6 (158) (130) (148) Elongation, % (167) (98) (147) (102) Colour YI 16 (229) 16 (178) Loss, weight % Shrinkage, % Properties of after 2 months hot air ageing at 120 C show a slightly improved retention when using Tinuvin 327. The more significant advantage of the addition of UV stabiliser is illustrated in Table 3. Table 3: Properties of KRATON G 2705 compound with and without Tinuvin 327 after 2 months hot air ageing and UV ageing at 120 C phr Tinuvin MD PMD MD PMD Tensile strength, MPa (22) (5) (86) (106) Elongation, % (4) (4) (112) (104) Colour YI 20 (285) 14 (150) Loss, weight % Shrinkage, % Under conditions that imply UV light exposure, UV stabilisers should be added to KRATON G compounds. (4) phr: parts per hundred parts rubber. (5) MD: mould direction; PMD: perpendicular to mould direction. (6) (--) denotes percentage retention. page 4 of 7

5 Weathering resistance of KRATON G compounds To improve the weathering stability of KRATON G 7720 compound, a combined antioxidant package of TiO 2 and Tinuvin can be used. TiO 2 reduces the transmission by reflecting the light while Tinuvin agents absorb it. The resulting light transmission is decreased by more than 60% by adding 1% of TiO 2 in the compound. Increasing the loading level of TiO 2 will further reduce the light transmission. A very good retention of mechanical properties is obtained by adding such stabiliser packages, as shown in Table 4. Table 4: 2000 hours QUV weathering antioxidant (AO): TiO 2 /ZnO, Tinuvin 327 and 770: 2.5, 0.07 and 0.23% 313 nm 340 nm % Retention in Strength Elongation Strength Elongation KRATON G 7720 compound KRATON G 7720 compound +AO The combined benefits of carbon black and UV absorbers, or TiO 2 pigment and UV absorbers added in KRATON G automotive compounds have been found to give 100% retention of strength after 4 years exposure in Florida. Natural or black KRATON G 1654 Polymer-based compounds containing 100 phr of calcium carbonate have been aged in a SEPAP oven. All compounds contain Tinuvin 327 (1.2 phr), Irganox 1010 (0.4 phr) and TiO 2 (10 phr). The effect of the addition of Tinuvin 770, Epikote 1004 and carbon black on the ageing resistance is reported in Table 5. Table 5: Suntest: accelerated ageing at 60 C under a UV light: nm Phr F1 F2 F3 F4 F5 F6 Tinuvin Epikote Carbon black % Retention in Tensile strength Elongation at break Table 5 shows that a big improvement in mechanical properties retention is observed when adding Epikote 1004 (F1 versus F3, or F2 versus F4). This is probably due to the action of the epoxy, coating and deactivating the filler surface. Thus it prevents the absorption of the antioxidant system by the filler. The addition of Tinuvin 770 also results in a better ageing resistance (F1 versus F2 and F3 versus F4). In all cases the addition of carbon black gives better properties retention (F5 and F6). page 5 of 7

6 Comparison with other products Table 6: A comparison of black KRATON G 1651 Polymer-based filled compounds with EPDM and PVC roofing materials Irganox Tinuvin CaCO Epon month at 120 C KRATON G 1651 EPDM 7 PVC Polymer % Retention in tensile strength Elongation at break week at 158 C % Retention in tensile strength melts Elongation at break With a suitable antioxidant package, black KRATON G 1651 Polymer-based compounds show improved ageing behaviour if compared with PVC and vulcanised EPDM. (7) Range for 4 different commercial products. Vulcanised EPDM. page 6 of 7

7 End Use Requirements If the finished article is intended for use in contact with food or in pharmaceutical applications, toys, and other human contact areas, the relevant regulations should be observed. Detailed information is available from the supplier. For food packaging, manufacturers of the final product should ensure that all ingredients used comply with the regulations. It should be noted that some of these regulations require tests to be carried out on the final product, e.g. migration. These are the responsibility of the final product manufacturer. Restriction on Medical/Healthcare Applications DO NOT USE KRATON POLYMERS PRODUCTS IN ANY DEVICES OR MATERIALS INTENDED FOR TEMPORARY OR PERMANENT IMPLANTATION IN THE HUMAN BODY. THE KRATON POLYMERS BUSINESS ALSO RESTRICTS THE USE OF ITS PRODUCTS IN OTHER MEDICAL/HEALTHCARE APPLICATIONS. Please contact your KRATON Polymers Sales Representative for more details. THE KRATON POLYMERS BUSINESS HAS NO SPECIFIC EXPERTISE IN THE MEDICAL/HEALTHCARE MARKET OR APPLICATIONS and does not intend to perform testing, clinical studies or other investigations of the suitability of its products for specific medical/healthcare applications. KRATON Polymers products are generally manufactured for use in a variety of commercial applications. DO NOT USE THE TRADENAMES, TRADEMARKS, LOGOS OR OTHER SIMILAR IDENTIFYING CHARACTERISTICS OF THE KRATON POLYMERS BUSINESS IN THE MANUFACTURE, SALE OR PROMOTION OF MEDICAL DEVICES OR MATERIALS. THE KRATON POLYMERS BUSINESS MAKES NO WARRANTY OF MERCHANTABILITY OR FITNESS FOR PURPOSES (INCLUDING MEDICAL APPLICATIONS) FOR ITS PRODUCTS. Each customer or user of KRATON Polymers products is solely responsible for determining the suitability of the materials they select for the intended purpose. With regards to medical/healthcare applications, each customer or user must conduct their own studies, registrations, and other related activities to establish the safety and efficacy of their products. Safety and Handling Precautions Read the Material Safety Data Sheet for KRATON Polymer products carefully and thoroughly before beginning any work with this product. Additional information relating to Health, Safety, Storage, Handling and Processing can be found in the KRATON Polymer HSE Fact Sheet (ref. K0155), available from your local KRATON Polymers representative. It is also recommended to consult other sources of safety information, for example, the current edition of Toxicity and Safe Handling of Rubber Chemicals - Code of Practice 4th Edition 2000, British Rubber Manufacturers Association Limited (BRMA), London, EC2A 3JE, UK, Tel: +44 (0) KRATON Polymers and compounds can accumulate electrostatic charges when rubbed, chafed or abraded. Equipment should provide a means of dissipating any charges that may develop. Processing of KRATON Polymers and compounds in high shear equipment can cause the temperature to rise. Do not allow the temperature to exceed C ( F) for KRATON D Polymers and compounds and C ( F) for KRATON G Polymers and compounds. Maintain a fire watch if these temperatures are reached. KRATON Polymer products (the neat resin or the base product) are high molecular weight polymers which by all accounts are non-toxic and biologically inactive. Warranty The information contained in this publication is, to the best of our knowledge, true and accurate, but any recommendations or suggestions which may be made are without guarantee, since the conditions of use are beyond our control. Furthermore, nothing contained herein shall be construed as a recommendation to use any product in conflict with existing patents covering any material or its use. All products purchased from or supplied by the KRATON Polymers Business are subject to terms and conditions set out in the contract, order acknowledgement and/or bill of lading. The KRATON Polymers Business warrants only that its products will meet those specifications designated as such herein or in other publications. All other information supplied by the KRATON Polymers Business is considered accurate but is furnished upon the express condition that the customer shall make their own assessment to determine the products suitability for a particular purpose. The KRATON Polymers Business makes no other warranty, either express or implied, including those regarding such other information, the data upon which the same is based, or the results to be obtained from the use thereof; that any products shall be merchantable or fit for any particular purpose; or that the use of such other information or product will not infringe any patent. For further information: In the USA call toll free KRATON ( ) In Europe/Africa fax +44-(0) In Asia-Pacific fax In South America fax +55 (0) or contact your local KRATON Polymers representative Contact us: Marketing Communications Manager KRATON Polymers Stellar House Barbour Square High Street Tattenhall Chester CH3 9RF UK Visit us at: K0027 FSb 00E Ageing Characteristics W&B/ KRATON Polymers 11/2000. All rights reserved. page 7 of 7