PREPARATIONS AND MECHANICAL PROPERTIES OF LOW PROTEINS RADIATION VULCANISED NATURAL RUBBER LATEX (RVNRL)

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1 MY PREPARATIONS AND MECHANICAL PROPERTIES OF LOW PROTEINS RADIATION VULCANISED NATURAL RUBBER LATEX (RVNRL) Wan Manshol bin W Zin and Chai Chee Keong RAYMINTEX Plant Malaysian Institute for Nuclear Technology Research (MINT) Bangi, Kajang, Selangor ABSTRACT Low proteins latex can be used in RVNRL preparation Either Formulation RII, uses single sensitiser or Formulation RIII, uses a combination of sensitisers are useful in low proteins RVNRL preparation However, these RVNRL formulations produce film vulcanisates of different mechanical properties and accelerated ageing resistance Lateks kandungan protin rendah boleh digunakan untuk menyediakan lateks prapemvulkanan menggunakan kaedah sinaran (RVNRI,) Sama ada Fomulasi RII yang menggunakan satu bahan pemeka, atau Fomulasi RIII yang menggunakan gabungan dua bahan pemeka boleh digunakan Walaubagaimana pun dua sistem fomulasi ini menghasilkan RVNRL kandungan protin rendah yang mempunyai sifat mekanikal dan daya tahan kepada proses penuaan yang berbeza Introduction Since the early 1990's, the emergence of latex proteins allergy related to the use of natural rubber latex gloves has raised concern to natural rubber latex gloves users that such gloves are health risks and should be avoided at all costs The fact natural rubber latex gloves have been proven to be effective for a long time as a first line of defence against infectious diseases for healthcare workers and patients and that billions of natural rubber latex glove users have been protected against virus transmission as a consequence seem easily forgotten In recognition of the heightened concern of health risk arising from the proteins in natural rubber latex products especially gloves 1 " 3, the authors and their colleagues have embarked in an R&D the use of low proteins latex for the preparation of prevulcanised natural rubber latex by gamma irradiation The many factors which favours the use of gamma irradiation in the preparation of prevulcanised natural rubber latex are discussed elsewhere 4 " 6 The present studies involved in the laboratory scale preparation of low proteins prevulcanised natural rubber latex and its properties INISMY063

2 Materials Natural rubber latex Low proteins concentrated natural rubber latex is used in carrying out the research work This latex is supplied by Getahindus (M) Sdn Bhd Before further work the latex is analysed for its total solid content (tsc), dry rubber content (drc), mechanical stability time (MST) and ph value is recorded Sensitisers Sensitisers are used to increase the efficiency of vulcanization and to reduce the y irradiation dose require to produce radiation prevulcanised natural rubber latex of optimum tensile strength The sensitisers use are either a combination of 1,6hexane dioldiacrylate (HDDA) and nbutyl acrylate (nba) or HDDA only Stabiliser The sensitisers are found to affect the stability of the latex To overcome the problem, the use of a stabilizer is a prerequisite Potassium laurylic acid is used for the purpose Antioxidant Prevulcanised natural rubber latex by yirradiation exhibits poor accelerated ageing properties Adding antioxidant into the latex is a must The antioxidant employed in these studies is IRGANOX 1520 Formulation and Method Examples of latex formulations employed in preparing low proteins radiation prevulcanised natural rubber latex are given in Table 1 The addition of a stabilizer, sensitiser/s, antioxidant is carried out with continuous stirring and in the order given in Table 1 The latex mixture is diluted with water and stir for a couple of hours before it is placed into one liter screwcapped bottles and irradiated with yrays from cobalt60 source for absorbed dose of between approximately 9 to 16 kgy After irradiation the latex now known as prevulcanised natural rubber latex is analyses for properties Properties of Low Protein RVNRL Vulcanisates Film vulcanisates are prepared by having the irradiated latex diluted to 35 tsc and coagulant dipped using calcium nitrate on cleaned glass plates Films are leached overnight before drying in an air convection oven at 100 C until fully transparent (30 minutes) Dried films are then subjected to overnight maturation at room temperature in a desiccators Five dumbbellshaped test pieces are cut from each film samples according

3 TABLE 1: Materials NR Latex Stabiliser Sensitiser I Sensitiser II Antioxidant Water Latex Formulation Formulation RII pphr To dilute the latex to 52 tsc Formulation RIII pphr To dilute the latex to 52 tsc to BS 6746 The tensile strength, modulus and elongation at break are determined per relevant ASTM standards To elucidate the effects of ageing on low protein RVNRL film vulcanisates, film samples cut into dumbbellshaped test pieces are subjected to accelerated ageing in a Toyoseiki Geer Oven at 100 C for 22 hours It is repeated at 70 C for seven day Results and Discussions The results of mechanical properties evaluations on films vulcanisates of low proteins RVNRL prepared according to Formulation RII and Formulation RIII are summarized in Table 2 and Table 3 respectively And graphical representations of the results are given in Figure 1, Figure 2 and Figure 3 Within the range of irradiation dose employed in the experiment, in general, tensile strengths of film vulcanisates of low proteins RVNRL prepared according to Formulation RII are higher compared to low proteins RVNRL film vulcanisates from Formulation RIII Film vulcanisates from Formulation RII also found to give better resistant to the process of accelerated ageing carried out at 100 C for 22 hours and at 70 C for 7 days For both formulations, RII and RIII the modulus at 500 and 700 elongations increases with irradiation dose However, Formulation RII gives film vulcanisates of lower modulus compared to Formulation RIII, please refer to Figure 2 and Figure 3 The irradiation dose range used in these studies is found insufficient to clearly determine the irradiation dose for the optimum tensile strength From Figure 1 it is most likely that the minimum irradiation dose used is already exceeded the irradiation dose require for the optimum tensile strength This is especially true for the studies using Formulation RIII where after the minimum irradiation dose of approximately 9 kgy, further increased in irradiation dose give film vulcanisates of lower tensile strengths Based on the results obtained in these studies, it is most likely that to prepare RVNRL of optimum tensile strength using low protein natural rubber latex require lower irradiation dose compared to the use of the standard high ammonia natural rubber latex Hence, despite higher cost of

4 low proteins natural rubber latex compared to the standard high ammonia natural rubber latex, radiation vulcanisation can still be applied on the latex because the high latex cost may be compensated by the lower irradiation dose requires for optimum tensile strength The experiment will be repeated using lower irradiation doses Moreover, irradiated latex will also be analysed for other properties like physical properties and water soluble proteins content, and the result will be reported in the next paper Conclusions More research works need to be done and lower irradiation dose range is use in irradiating the latex Studies done this far show that RVNRL can be prepared from low proteins natural rubber latex Low proteins RVNRL prepared by Formulation RII has the required mechanical properties and can be made useful in the production of examination gloves and finger cots Acknowledgements The authors are very grateful to their coworkers Najib bin Mohamad Zakey, Mohd Mazren bin Mohamad, Khairul Hisyam bin Mohamed Yusof and Hafizuddin bin Maseri for their excellent effort and contribution to make this project a success References 1 Lai Pin Fai (1997) Benefits Versus the Risk of Using Natural Rubber Latex Gloves Full Texts International Rubber Conference 1997 Kuala Lumpur, Malaysia, 69 October Esah Yip (1997) Measurement of Total Extractable Proteins in Latex Gloves: A Comparative Study of the RRIM and ASTM Modified Lowry Method Full Texts International Rubber Conference 1997 Kuala Lumpur, Malaysia, 69 Octoberl Tan Nee Hong, Naoya Ichikawa, Fong Weng Kong, and Atsuko Kawasaki (1997) Highly Deproteinised Natural Rubber Latex Examination Glove Production Full Texts International Rubber Conference 1997 Kuala Lumpur, Malaysia, 69 October Wan Manshol bin W Zin, Norjanah bte Mohid, Jusoh bin Hasan, Wan Khairul Amalina bte Wan Md Noor and Zulkifli Jaafar (1993) The Preparation of RVNRL Using MalaysianProduced Latices Radiat Phys Chem, 42, Wan Manshol bin W Zin, Norjanah Mohid and Meor Yahaya Razali (1995) RVNRL A Potential Material In Latex Dipped Products Manufacturing Radiat Phys Chem, 46, Wan Manshol bin W Zin (1998) Semi Industrial Scale RVNRL Preparation, Products Manufacturing and Properties Radiat Phys Chem, 52,

5 TABLE 2: and at Break of Low Proteins RVNRL, Formulation RII Before Ageing Ageing 100 C for 22 hours 70 C for 7 days Dose, 500, _ TABLE 3: and at Break of Low Proteins RVNRL, Formulation RIII Before Ageing 100 C for 22 hours 70 C for 7 days Dose, 500,

6 Rll Rill Irradiation Dose, kgy FIGURE 1: Strength of Low Proteins RVNRL, Formulation RII and Formulation Rill c o O5 c _o LLJ S CD O CL s 3 O Rll Rill Irradiation Dose, kgy FIGURE 500 of Low Proteins RVNRL, Formulation RII and Formulation Rill Rll Rill Irradiation Dose, kgy FIGURE 700 of Low Proteins RVNRL, Formulation RII and Formulation RIII