Technical Note Nr Latex Amp Latex Products Nocil Ltd-Books Pdf

Technical Note NR Latex amp Latex Products Nocil Ltd
05 May 2020 | 42 views | 0 downloads | 56 Pages | 454.40 KB

Share Pdf : Technical Note Nr Latex Amp Latex Products Nocil Ltd

Download and Preview : Technical Note Nr Latex Amp Latex Products Nocil Ltd


Report CopyRight/DMCA Form For : Technical Note Nr Latex Amp Latex Products Nocil Ltd



Transcription

Material by weight,Rubber hydrocarbon 86,Water dispersed in rubber hydrocarbon 10. Portentous material 1,Lipid substances 3,Trace metals Mg K Cu etc 0 05. Density of rubber particles 0 92 g cc,Chemical composition Cis 1 4 polyisoprene. Chemical structure,H3C H H3C H,CH2 CH2 CH2 CH2,Number avg mol wt Approx 300 000. Degree of polymerization Approx 5000, Predominantly a cis configuration all CH3 groups on same side.
Some evidence of presence of oxygen in the form of carbonyl groups which cause hardening of NR on. prolonged storage Also contains some peroxides which form redox systems with other constituents. causing cross linking and chain scission, Protein content is in the form of adsorbed layer which surrounds the external surface of NR particles. protein is globulin dissolved in the serum Protein determines the charge the electrophoresis. characterization and coacervation behavior, Lipids comprise of sterols and sterol esters approx 0 4 wax and phospholipids adsorbed on rubber. particles through which the proteins are anchored on rubber particles and are dissolved in the rubber. hydrocarbon, The gel content solvent insoluble rubber steadily increases as latex is stored After 2 to 3 months the. gel content in toluene is as high as 50 process similar to storage hardening of NR which takes its. Mooney viscosity to 80 100,The Aaqueous Phase, The aqueous phase is a dilute solution of density 1 02 g cc contains dissolved chemicals such as. Carbohydrates approx 1 e g methyl inositol, Proteins approx 1 globulin mol wt 200 000 Hevein mol wt 10 000 few others.
Amino acids approx 0 1 glycine tyrocin 12 others,Free nitrogenous bases e g methylamine. Organic acids other than amino acids,Metal ions K Mg Fe Na Cu etc. Complex enzymes, The predominant CATION present in NR latex is Ammonium NH4 although serum also contains. significant 25 35 of Potassium cations Following table summarizes avg anion concentrations found in. the serum of matured NR latex,Anions HA Latex,Carbonate 22 25 22 0. Acetate 12 81 8 74,Malate 9 28 10 14,Succinate 5 45 2 03.
Citrate 5 04 6 94,Formate 4 67 3 13,glycerophosphate 2 81 4 24. Glucose t phosphate 2 24 0 31,Phosphate 2 01 2 22,Oxalate 1 16 1 22. Chloride 1 10 2 01,Sulphate 0 58 0 03,Hydroxide 0 51 0 14. Propionate 5 34,Adsorbed non rubber materials, Protein lipid complexes Lipids hydrolyze releasing fatty acid soaps which improve the mechanical. stability of NR latex, High proportions of phospholipids Furanoid acid representing total fatty acids play role in latex.
stabilization, Anions of various types behave differently towards zinc ammine ions which are major cause of NR latex. destabilization,NR Latex Properties,Whitish fluid Density 0 975 0 980. pH 6 5 7 0,Surface free energy 40 45 ergs cm,Rubber particles 35 by weight. Aqueous phase 55 by weight,Lutoid phase 10 by weight. Rubber phase 25 35 by weight typical 33,Difference between TSC and DRC 3.
Rubber particle size between 200 2000 A 10 A 1m 1 10 1 10 cm. Rubber particles are negatively ve charged i e Anions. Particle Size Distribution,Wide range of diameter 0 01 to 5 0 Avg 0 25 0 8. Particle size distribution is fairly consistent, Synthetic rubber lattices have much lower particle size than NR latex. Latex containing more than 25 by volume of disperse phase is a non Newtonian fluid Hence the. measured viscosity is dependant on the rate of shear rates e g. Brookfield viscosity at 6 rpm 180 mPa s,Brookfield viscosity at 60 rpm 87 5 mPa s. Preservation of NR latex,High Ammonia NR Latex, NR Latex coagulates within few hours due to development of acidity through micro organisms when the. pH falls to around 5 0 Ammonia at 0 7 1 0 is required for long term preservation Ammonia also acts. as a bactericide and sequestering agent for Mg and PO4 ions. The disadvantages of ammonia are that It has a strong odor It is expensive Ammonia preserved latex. undergoes marked thickening when compounded with ZnO It interferes with the gelation of latex foam. compound by Sodium Silicofluoride SSF Excess ammonia has to be driven off before the latex is used. for compounding,Low Ammonia NR Latex, Zinc Dialkyl dithiocarbamates ZDMC ZDEC at 0 1 0 2 along with 0 2 ammonia and 0 2.
lauric acid enhance the stability of NR Latex to the level of 0 7 ammonia preserved latex without. any significant effect on vulcanization However the latex may give deposits that discolor badly on. ageing copper staining, Boric acid at 0 2 with 0 2 ammonia 0 05 lauric acid is most popular LA Preservative system. Precaution 0 1 boric acid increases the KOH number by 0 14 units The deposits are free from. discoloration and boric acid is cheap harmless to human beings easy to handle and can be. estimated accurately However the unvulcanized deposits tend to soften faster. Sodium Pentachlorophenate at 0 2 with 0 2 ammonia is used as a stabilizer but not popular due. to toxicity problems associated with pentachlorothiophenol. Creaming of Latex Concentrates, The density of rubber 0 92 g cc dispersed in latex is less than the density of serum 1 02 g cc. hence the rubber particles move upwards This creaming effect is prominent if NR latex is left. undisturbed for more than a week,Filterability, Filterability is defined as amount of latex which will pass through a filter under standard conditions before. clogging takes place Creamed latex gives greater filterability than centrifuged latex SR Lattices have. high filterability due to smaller particle size,NR Latex Grades. NR latex Specification ASTM D 1076 Type 1 Type 2 Type 3. Total Solids contents TSC min 61 5 66 0 61 5,Dry Rubber Content DRC min 60 0 64 0 60 0.
TSC DRC max 2 0 2 0 2 0, Total alkalinity as ammonia as on latex 0 60 min 0 55 min 0 29 max. Sludge content max 0 10 0 10 0 10,Coagulum content max 0 05 0 05 0 05. KOH number max 0 80 0 80 0 80,Mechanical Stability min sec 650 650 650. Copper content max 0 0008 0 0008 0 0008,Manganese content max 0 0008 0 0008 0 0008. Color on visual inspection A A A,Odor after neutralization with boric acid B B B.
Note A No pronounced blue or gray B No putrefactive odor Type 1 Centrifuged NR latex. preserved with ammonia Type 2 Creamed NR latex preserved with ammonia Type 3. Centrifuged NR latex preserved with ammonia and secondary preservatives. Destabilization of latex or Gelation, NR latex may be destabilized by acidification addition of salts of polyvalent metals higher concentration. of any salt dehydration mechanical agitation or freezing Important methods of destabilization are those. which produce uniform destabilization gelation of a three dimensional aggregate of rubber particles. The aqueous phase is retained in the interstices of the gel NR latex has excellent gel strength hence. excellent film forming ability most suitable for manufacture of dipped goods and foamed products. Gels do not have constant composition or structure and film shrinks due to exudation of aqueous phase. Excessive stabilization results in weaker gels and slower rate of gelation. Three methods of Gelation,Organic acid acids or acid liberating substances. Use of salts of multivalent cations,Application of heat. Gelation By Acids, NR latex particles are stabilized due to adsorbed carboxylic anions from fatty acid soaps and protein. molecules on the surface This net ve charge produces repulsive forces and ensures absence of. aggregation Reduction in pH by the addition of acids reduces ionization of adsorbed anions and. decreases the repulsive forces due to which gelation takes place. Gelation by Salts, Calcium nitrate is widely used in the dipping industry to produce gels of compounded latex on the.
formers Calcium ions form insoluble salts with all fatty acid soaps solutions of proteins and destabilize. the latex The Calcium ions also effect high concentration of ions which reduce the colloidal stability of. compounded latex by creating a electrical double layer around rubber particles and thus reducing the. strength of ve electrical potential, Zinc ions also produce effect similar to Calcium ions However Zinc ions react with ammonia to form. complex ammine cations that form insoluble salts with fatty acid soaps but do not react with proteins. thus producing partial destabilization effect,Heat Sensitized gelation. Latex compounds are specially formulated to give rapid gelation when the temperature is increased with. room temperature stability unaffected The zinc oxide ammonium salt process ZOA uses the ability of. ammonium salts to increase the solubility of Zinc oxide in aqueous ammonia solutions and thus enhance. the effect of Zinc ions The addition of an ammonium salt also increases the ionic strength of the. aqueous phase and contributes to destabilization The ZOA process is truly not heat sensitive since the. gelation occurs at room temperature within a short time However heat accelerates the process. Film formation and structure, Formation of film involves immobilization of free moving polymer particles when brought into contact In. most of latex goods manufacturing processes the contact between polymer particles is achieved by. gelation process result of drop in pH as the volatile ammonia stabilizer during the initial stages of. drying Note that if the pH is maintained by using a fixed alkali stabilizer like KOH this process will not. proceed Gelation does not affect the rate of drying of the film or any other characteristics The film is. leached before drying to remove water soluble serum residues residual coacervant and other surface. active substances This improves the feel of the film eliminates porosity defects and resists water. absorption and ageing Warm hot water is used for leaching use of water soluble compounding. ingredients e g water soluble accelerators is avoided where leaching process is involved The film. thickness per dip varies from 0 1 mm to 0 2 mm depending on the viscosity of the latex compound Multi. dip systems are used to produce a product of desired film thickness. Chemically Modified Lattices,Prevulcanized NR Latex. PV NR latex is a chemically modified NR latex which on drying gives a vulcanized film PV NR Latex is. produced in the rubber plantation factory using field latex or concentrates or in the consumer s factory. NR latex compounds containing ZDEC or ZDBC ultra fast accelerators usually achieve some degree of. pre vulcanization during the process of maturation in the dispersed rubber phase Commercially. produced PV NR latex is prepared as follows,Compounding Ingredients Dry pbw Wet pbw.
NR Latex 60 Ammonia preserved 100 167,50 ZnO dispersion 1 2. 50 ZDEC dispersion 1 2,50 Sulphur dispersion 2 4,10 KOH Solution 0 3 3. 10 Stabilizer Solution Sodium Caseinate 0 2 2, The latex is contained in a stirred and jacketed mixing vessel and the compounding ingredients are. added The vessel is heated by passing hot water through the jacket After heating for 3 5 hr at 50. 60 C or when the QC tests show that the desired degree of cross linking has been achieved the latex. compound is cooled to room temperature It is then filtered or clarified centrifugally before use. The degree of cross linking is determined by solvent swelling combined sulphur analysis or by. assessment of tensile properties PV latex is popular in medium small sector dipped goods industry since. further compounding of latex is not necessary or is limited to incorporation of desired pigments e g. manufacture of toy balloons medical goods feeding bottle teats etc The cross linking can be achieved. by reaction with sulphur sulphur donors e g TMTD DTDM TETD or by gamma radiation The. compounding formulations can vary depending on end applications If ZDEC ZDBC is present ZnO is. not necessary ZnO reduces the film clarity and may be substituted by ZnCO3 to improve the same For. peroxide cross linking tert butyl hydro peroxide and tetra ethylene pentamine are used Maximum film. clarity is obtained by using ZDBC alone The cross links found in Prevulcanized latex are predominantly. polysulphidic except for Sulfurless Sulfur donor cures. Heveaplus MG graft polymers, Grafted side chains of polymethyl methacrylate on NR molecule. The grades Polymethyl methacrylate contents 15 MG15 30 MG30 49 MG49. The film forming ability of MG lattices decreases as polymethyl methacrylate content increases. This latex can be blended with unmodified latex in desired proportions Such blends provide considerable. increase in modulus and retention of tensile strength tear resistance Film forming properties can be. improved if methylacrylate is partially replaced by butyl methacrylate in the grafting reaction. Hydroxyl amine modified latex HRH latex, On storage the viscosity of the rubber in latex concentrates increases due to the molecular cross linking.
process The rate of storage hardening is faster during the first 20 30 days and beyond 100 days the. process is completed When hydroxylamine is added at 0 15 phr at the latex production stage the. hardening effect is inhibited The vulcanizates show slightly low modulus thus for latex foam a lower. volume shrinkage Other properties are largely unchanged This latex is useful for production of latex. foam and latex adhesives for quick grab strength used in footwear production. Deprotenized latex, Latex concentrate contains about 2 by weight protein of which 50 is . Technical Note NR Latex amp Latex Products Rubber Latex is a stable dispersion of polymeric substances in aqueous medium and is essentially a two phase system 1 Disperse phase discontinuous phaseof rubber molecules amp 2 Dispersion medium aqueous continuous phaseof serum Basically there are two types of lattices viz Natural lattices and

Related Books

Het verhaal van de Industri le Revolutie

Het verhaal van de Industri le Revolutie

Vanwege die omstandigheden stierven er veel kinderen wel een kwart van alle geborenen Oorlogen veroorzaakten ook veel slachtoffers omdat allerlei legers het land en de boerderijen van de boerenbevolking verwoestten En dan had je nog die vreselijke ziekte de pest In het jaar 1350 kwam een derde van de bevolking om het leven door die ziekte De

Nieuwe tijden industri le revolutie

Nieuwe tijden industri le revolutie

Niet Belgi maar Engeland was het eerste land dat te maken kreeg met de Industri le Revolutie en dit in het jaartal 1750 Wat betekent het woord revolutie Een plotse grote verandering Wat is dan Industri le revolutie Eerst werden spullen met de hand gemaakt Door de industri le revolutie konden de spullen met machines gemaakt worden De uitvinding van de stoommachine door

DIE DRITTE INDUSTRIELLE REVOLUTION AUfbRUch IN EIN

DIE DRITTE INDUSTRIELLE REVOLUTION AUfbRUch IN EIN

DIE DRITTE INDUSTRIELLE REVOLUTION A U fb RU ch IN EIN k OLO g IS ch ES J A h R h UNDERT Dimensionen und h erausforderungen des industriellen und gesellschaftlichen Wandels BESTELLUNG VON PUBLIKATIONEN Bundesministerium f r Umwelt Naturschutz und Reaktorsicherheit BMU Postfach 30 03 61 53183 Bonn Tel 0228 99 305 33 55 Fax 0228 99 305 33 56 E Mail bmu broschuerenversand de

Strata CIX General Description content us dynabook com

Strata CIX General Description content us dynabook com

TOSHIBA Telecommunication Systems Division December 2007 Strata CIX40 CIX100 S CIX100 CIX200 and CIX670 General Description Title Page

Strata CIX Voice Mail System Hardwire Telecom

Strata CIX Voice Mail System Hardwire Telecom

Strata CIX Voice Mail System System Administrator Guide Publication Information Toshiba of Canada Limited reserves the right without prior notice to revise this information publication for any reason including but not limited to utilization of new advances in the state of technical arts or to simply change the design of this document Further Toshiba of Canada Limited also reserves the

CIX Programming Manual Index Trading Toshiba Avaya

CIX Programming Manual Index Trading Toshiba Avaya

Programming Manual Volume 1 Software Release 5 2 Title Page May 2008 Publication Information Toshiba America Information Systems Inc Telecommunication Systems Division reserves the right without prior notice to revise this information publication for any reason including but not limited to utilization of new advances in the state of technical arts or to simply change the design

Strata CIX and CTX IPT DKT Telephone User Guide

Strata CIX and CTX IPT DKT Telephone User Guide

Strata CIX and CTX IPT DKT Telephone User Guide is the repair or replacement of such defective or missing parts as are causing the malfunc tion by TAIS or its authorized dealer with new or refurbished parts at their option If TAIS or one of its authorized dealers does not replace or repair such parts the retail customer s sole remedy will be a refund of the price charged by TAIS to

Strata CIX and CTX IPT DKT Telephone Administrator Manual

Strata CIX and CTX IPT DKT Telephone Administrator Manual

Telephone Administrator Manual Publication Information Toshiba America Information Systems Inc Digtal Solutions Division reserves the right without prior notice to revise this information publication for any reason including but not limited to utilization of new advances in the state of technical arts or to simply change the design of this document Further Toshiba America

Strata CTX Standard Telephone User Guide

Strata CTX Standard Telephone User Guide

Standard Telephone User Guide Digital Business Telephone Systems Publication Information Toshiba America Information Systems Inc Telecommunication Systems Division reserves the right without prior notice to revise this information publication for any reason including but not limited to utilization of new advances in the state of technical arts or to simply change the design of this

CTX100 and CTX670 General Description

CTX100 and CTX670 General Description

CTX100 and CTX670 General Description Digital Business Telephone Systems Publication Information Toshiba America Information Systems Inc Telecommunication Systems Division reserves the right without prior notice to revise this information publication for any reason including but not limited to utilization of new advances in the state of technical arts or to simply change the design

An Interdisciplinary Journal CONTENTS Dedicated to

An Interdisciplinary Journal CONTENTS Dedicated to

Art Science amp Practice of Hypnosis Editorial iii The Use of Hypnosis and Relaxation Therapy in Professional and Life Skills Coaching 81 Jeff Berger Ego State Therapy and the Treatment of Depression 89 Debbi Holopainen and Gordon J Emmerson Psychoneuroimmunological Background to a Controlled Trial of Hypnotherapy as a Treatment for Irritable Bowel Syndrome 101 Julie Phillips Moore