Science and technology of rubber reclamation with special attention to NR-based waste latex products

A comprehensive overview of reclamation of cured rubber with special emphasis on latex reclamation is depicted in this paper. The latex industry has expanded over the years to meet the world demands for gloves, condoms, latex thread, etc. Due to the strict specifications for the products and the unstable nature of the latex as high as 15% of the final latex products are rejected. As waste latex rubber (WLR) represents a source of high-quality rubber hydrocarbon, it is a potential candidate for generating reclaimed rubber of superior quality. The role of the different components in the reclamation recipe is explained and the reaction mechanism and chemistry during reclamation are discussed in detail. Different types of reclaiming processes are described with special reference to processes, which selectively cleave the cross links in the vulcanized rubber. The state-of-the-art techniques of reclamation with special attention on latex treatment are reviewed. An overview of the latest development concerning the fundamental studies in the field of rubber recycling by means of low-molecular weight compounds is described. A mathematical model description of main-chain and crosslink scission during devulcanization of a rubber vulcanizate is also given.

[1]  B. Saville,et al.  Structural Characterization of Sulfur-Vulcanized Rubber Networks , 1967 .

[2]  J. Bolland.  Kinetic studies in the chemistry of rubber and related materials. I. The thermal oxidation of ethyl linoleate , 1946, Proceedings of the Royal Society of London. Series A. Mathematical and Physical Sciences.

[3]  M. Gordon,et al.  Good’s theory of cascade processes applied to the statistics of polymer distributions , 1962, Proceedings of the Royal Society of London. Series A. Mathematical and Physical Sciences.

[4]  C. Kok,et al.  The effects of crosslink density and crosslink type on the tensile and tear strengths of NR, SBR and EPDM gum vulcanizates , 1986 .

[5]  E. C. Gregg,et al.  Chemical Structures in CIS-1, 4-Polybutadiene Vulcanizates. Model Compound Approach , 1970 .

[6]  J. Scheirs.  Polymer Recycling: Science, Technology and Applications , 1998 .

[7]  M. Gordon,et al.  Configurational Statistics of Highly Branched Polymer Systems , 1964 .

[8]  A. Tobolsky,et al.  The Dissociation Energy of the Tetrasulfide Linkage , 1965 .

[9]  Werner Hofman,et al.  Rubber Technology Handbook , 1989 .

[10]  A. Isayev,et al.  Devulcanization of Waste Tire Rubber by Powerful Ultrasound , 1996 .

[11]  Theory of Branching Processes and Statistics of Rubber Elasticity , 1965 .

[12]  D. Packham,et al.  The use of thiol-amine chemical probes in network characterisation of NBR vulcanizates , 1997 .

[13]  A. Tobolsky.  The chemistry of sulfides , 1968 .

[14]  C. G. Moore,et al.  Structural characterization of vulcanizates. Part IV. Use of triphenylphosphine and sodium di‐n‐butyl phosphite to determine the structures of sulfur linkages in natural rubber, cis‐1,4‐polyisoprene, and ethylene–propylene rubber vulcanizate networks , 1964 .

[15]  C. M. Blow.  Rubber technology and manufacture , 1971 .

[16]  R. Joseph,et al.  Comparative Investigation on the Reclamation of NR Based Latex Products with Amines and Disulfides , 2005 .

[17]  P. Flory.  Statistical Mechanics of Swelling of Network Structures , 1950 .

[18]  Y. Tokiwa,et al.  Degradation of the rubber in truck tires by a strain of Nocardia , 2004, Biodegradation.

[19]  P. Nicholas.  The Scission of Polysulfide Crosslinks in Scrap Rubber Particles through Phase Transfer Catalysis , 1982 .

[20]  Jacqueline H. Chen,et al.  Novel Ultrasonic Technology for Devulcanization of Waste Rubbers , 1995 .

[21]  Sabu Thomas,et al.  Recycling of natural rubber latex waste and its interaction in epoxidised natural rubber , 2001 .

[22]  C. G. Moore.  The nature of the crosslinks in tetramethylthiuram disulfide–zinc oxide–natural rubber vulcanizates , 1958 .

[23]  A. Charlesby.  Gel formation and molecular weight distribution in long-chain polymers , 1954, Proceedings of the Royal Society of London. Series A. Mathematical and Physical Sciences.

[24]  R. E. Humphrey,et al.  Reduction of Aromatic Disulfides with Triphenylphosphine. , 1964 .

[25]  D. Campbell.  Structural characterization of vulcanizates part X. Thiol‐disulfide interchange for cleaving disulfide crosslinks in natural rubber vulcanizates , 1969 .

[26]  J. L. Potter,et al.  Reduction of Disulfides with Tributylphosphine. , 1965 .

[27]  H. Mark,et al.  Encyclopedia of polymer science and engineering , 1985 .

[28]  A. Isayev,et al.  Basic Study of Continuous Ultrasonic Devulcanization of Unfilled Silicone Rubber , 1999 .

[29]  J. Blake,et al.  The chemistry and technology of rubber , 1937 .

[30]  W. C. Warner.  Methods of Devulcanization , 1994 .

[31]  J. Noordermeer,et al.  Mechanisms involved in the recycling of NR and EPDM , 1998 .

[32]  K. Takeda,et al.  Rubber-Degrading Enzyme from a Bacterial Culture , 1990, Applied and environmental microbiology.

[33]  C. Rader.  Recycling of Rubber , 1995 .

[34]  A. Isayev,et al.  Ultrasonic devulcanization of rubber vulcanizates. I. Process model , 1996 .

[35]  Ultrasonic Devulcanization of SBR Rubber: Experimentation and Modeling Based on Cavitation and Percolation Theories , 1998 .

[36]  M. Minagawa.  New developments in polymer stabilization , 1989 .

[37]  Grant Crane,et al.  Scrap Tire Disposal Procedures , 1978 .

[38]  A. Isayev,et al.  Ultrasonic devulcanization of rubber vulcanizates. II. Simulation and experiment , 1996 .

[39]  Paul J. Flory,et al.  Molecular Size Distribution in Three Dimensional Polymers. II. Trifunctional Branching Units , 1941 .

[40]  B. Milligan.  Vulcanization Accelerator and Activator Complexes. 2. Chemistry of Amine and Zinc Carboxylate Complexes of Zinc and Cadmium Benzothiazolyl Mercaptides , 1966 .

[41]  Shinzo Kohjiya,et al.  Devulcanization of sulfur-cured isoprene rubber in supercritical carbon dioxide , 2003 .

[42]  K. Knörr.  Reclaim from natural and synthetic rubber scrap for technical rubber goods , 1994 .

[43]  A. Isayev,et al.  Ultrasound Devulcanization of Sulfur Vulcanized SBR: Crosslink Density and Molecular Mobility , 1996 .

[44]  A. Isayev,et al.  Superior Mechanical Properties of Ultrasonically Recycled EPDM Rubber , 2003 .

[45]  A. Charlesby.  Solubility and molecular size distribution of crosslinked polystyrene , 1953 .

[46]  A. Isayev,et al.  Superior Mechanical Properties of Reclaimed SBR with Bimodal Network , 1997 .

[47]  V. Yashin,et al.  A Model for Rubber Degradation under Ultrasonic Treatment: Part I. Acoustic Cavitation in Viscoelastic Solid , 1999 .

[48]  K. Takeda,et al.  Microbial Degradation of Natural Rubber Vulcanizates , 1985, Applied and environmental microbiology.

[49]  M. M. Horikx.  Chain Scissions in a Polymer Network , 1956 .

[50]  Ultrasound devulcanization of SBR : Molecular mobility of gel and sol , 1997 .

[51]  D. S. L. Beau.  Science and Technology of Reclaimed Rubber , 1967 .

[52]  V. Yashin,et al.  A Model for Rubber Degradation under Ultrasonic Treatment: Part II. Rupture of Rubber Network and Comparison with Experiments , 2000 .

[53]  J. A. Beckman,et al.  Scrap Tire Disposal , 1974 .