The evaluation of a statistical size of both CNF and CNC in terms of width and length has posed a challenge for researchers, since most of these nanocelluloses are aggregated or dispersed in water as bundles or as web-like networks. Polyethylene is a polymeric material obtained by the polymerization process of ethylene: where n represents the mean degree of polymerization or the mean quantity of structural units. However, to the authors' knowledge, no information is available on the effect of insoluble cellulose DP on the catalytic efficiency of cellulase except that higher DP could result in higher synergy between CBHI and EGI (Henrissat, 1994; Okazaki et al., 1981; Okazaki and Moo-Young, 1978; Zhang and Lynd, 2006). When the life of active chain is relatively short, such as τs≪t, the effect of residence time distribution is relatively small, since even the reactants with short residence time will have enough for chain termination. Pratima Bajpai, in Biermann's Handbook of Pulp and Paper (Third Edition), 2018. Hassan S. El Khadem, in Encyclopedia of Physical Science and Technology (Third Edition), 2003. The films were further characterized by Fourier transform infrared spectroscopy (FTIR), scanning electron microscope (SEM), atomic force microscope (AFM), X-ray diffraction (XRD), and optical water contact angle. Polytetrafluoroethylene (PTFE)/polyacrylate core-shell nanoparticles were produced via the emulsifier-free seeded emulsion polymerization of acrylate monomers with PTFE latex as seed. Cellulose viscosity of mechanical pulps and high yield pulps are not measured, as it is usually quite high and not a factor in the strength properties of papers derived from these pulps. The coefficient of friction of plastics is … Relationship between DP and the length-weighted average length of CNF. Polymerization of tetrafluoroethylene (TFE) in an aqueous medium using a redox system in the presence of a hard disperse filler leads to polymerization-filled polytetrafluoroethylene (PTFE). Copyright © 1992 Published by Elsevier Ltd. https://doi.org/10.1016/0014-3057(92)90227-S. In nature, cellulose has a DP of approximately 10,000 glucopyranose units in wood cellulose and of 15,000 units in plant cellulose, whereas BC shows DP values of 2000–6000 [307,308]. In reality, the large size of the fluorine atoms forces them into a spiral arrangement causing them to pack tightly … Modification of the complete surface of expanded PTFE (ePTFE), i.e. This was found to be an important development for joint motion, due to the material’s high molecular weight, strength and wear resistance during the walking cycle. … Theoretically, the lower the DP, the more reducing and non-reducing ends are available, and one would expect that more CBHI/II would be able to work at one time while making it easier for endoglucanases to act. The resulting PA TFC-OSN membrane exhibits a high methanol permeance up to 13.2 L m–2 h–1 bar–1 with a rejection … Similar effects of DP for soluble cellodextrins on CBHII and EGI activity are reviewed elsewhere (Zhang and Lynd, 2004b). 12,13 According to another argument an ultra-high molecular weight itself does not directly contribute to tenacity, but higher molecular weight is necessary for the drawing, in order to support the drawing force through entanglement points.5 Indeed, although the molecular weight of PPTA fibers is in the low 10000 s, much lower than that of polyethylene, they still possess high enough strengths and moduli. Copyright © 2020 Elsevier B.V. or its licensors or contributors. Number average DP and weight average DP are the two main types used for measuring the DP. This is because the transport processes, which influence both residence time distribution and concentration distributions, are very different in different reactors. We use cookies to help provide and enhance our service and tailor content and ads. The effect is of some practical importance in limiting the service life of polymers … G. Moad, in Polymer Science: A Comprehensive Reference, 2012. The moments can be related to the molecular weight averages as follows: The breadth of the molecular weight distribution is often discussed in terms of the dispersity (Đ) (also commonly called the polydispersity index or the polydispersity) and is expressed in terms of the moments as shown in eqn [41]: In calculations the moments can be treated as concentrations. The one method is called suspension polymerization, in this method water is used as the base in which TFE is polymerized. The degree of polymerization of polytetrafluoroethylene (see Table 16-3) is 7500. Therefore, the polymerization process is always studied by analyzing reaction kinetics and transfer processes. Reprinted with permission from R. Shinoda, T. Saito, Y. Okita, A. Isogai, Relationship between length and degree of polymerization of TEMPO-oxidized cellulose nanofibrils, Biomacromolecules 13(3) (2012) 842–849. If we neglect end groups, the number molecular weight (Mn) is given by eqn [36]: where M0 is the molecular weight or molar mass of the monomer or repeat unit. This method of moments is accurate as long as the kinetics are independent of chain length. (a) the molecular weight of the chains, and. This method produces grains of PTFE which can be later processed into pellets. and + are the die polymers of which length is and ,respectively. We use cookies to help provide and enhance our service and tailor content and ads. PTFE (Polytetrafluoroethylene), a strong, tough, waxy, non-flammable kind of synthetic resin produced from polymerization process. The polymerization conditions for preparing PTFE… A silver-plated reactor, quarter-filled with a solution consisting of 0.2 parts ammonium persulphate, 1.5 parts borax and 100 parts of water, and with a pH of 9.2. Polymerization C = F F C F F C F F C F F n PTFE C = F F C F F + The structure of PTFE This representation does not do justice to the structure of PTFE which has a fully fluorinated carbon-carbon backbone chain. In the 1960s UHMWPE was introduced in the medical field. Crystallinity of as-polymerized PTFE in this polymerization was as high as 90%; therefore, the polymer particles were rigid and the monomer did not diffuse to the inside. The influences of various factors on the polymer yield, the conversion of TFE and the degree of filling were studied. This … This research paper makes simulation based on Polymer Plus. The term degree of polymerization is also used in some contexts in the polymer literature to mean the number of monomer residues in an average polymer molecule. Therefore, for free radical polymerization, a CSTR is usually used to produce product with a narrow distribution of degree of polymerization. The degree of polymerization of a polymer (Xi) is equal to the chain length i (the number of monomer units in the chain). The reaction order, activation energy and the ratio of rate constants for chain propagation and termination were determined. It is … The relative molecular mass of PTFE is relatively large, hundreds of thousands of low, more than 10 million high, and generally several million (degree of polymerization is on the order of 10^4, while polyethylene is only 10^3). Molecular mass and crystallinity are the main factors that define polyethylene’s chemical, physical and mechanical properties. Furthermore, a decrease in β-glucosidase activity with increasing DP has been reported (Lee and Fan, 1980; Wilson et al., 1994). Step-growth polymerization refers to a type of polymerization mechanism in which bi-functional or multifunctional monomers react to form first dimers, then trimers, longer oligomers and eventually long chain polymers.Many naturally occurring and some synthetic polymers are produced by step-growth polymerization, e.g. Thus, a disaccharide would be expected to have about half the reducing power of glucose (actually 53%), a trisaccharide, a third (actually 35%), and a tetrasaccharide, a fourth (26%) that of glucose, and so on. This gives high crystallinity and good mechanical properties; however, this is the primary cause of its ductility and fracture toughness. Microkinetics describes the dependence of reaction rate on temperature and reactant concentrations. It is calculated as the ratio of molecular weight of a polymer and molecular weight of the repeat unit. Due to the diversity of PTFE process, polymerization kinetics data is also di erent; moreover, the con dentiality of technology makes it di cult to get the … Even for the same reaction with the same reaction mechanism, they also depend on polymerization method, reactor structure, and operation mode. All the factors that can influence temperature and concentration distribution in the reactor, such as mixing, flow, mass transfer, and heat transfer, may have a great impact on product quality. Polymerization temperature and pressure usually range from 0 to 100°C and 0.7 to 3.5 MPa. Calculate the degree of polymerization of this PTFE. But only the last two are the main ways. Alfred Rudin, Phillip Choi, in The Elements of Polymer Science & Engineering (Third Edition), 2013. Kinetic simulation of radical polymerization to evaluate dispersities typically involves evaluation of the moments rather than the complete distribution. As it has been already explained, CNC are produced by the dissolution of amorphous regions through their dissolution during acid hydrolysis. No. Higher DP is desired for better mechanical properties [6,26]. 3. This number will be equal to the one in the definition stated above if the repeating unit is the residue of a single monomer. the lumen and … In the case of para-aramid fibers, the chain orientation is mainly due to the liquid crystalline property derived from their rigid molecular chains, therefore the high molecular weight of PE is not necessary. polyethylene, PTFE, and polypropylene satisfy this criterion. Figure 4 shows a graft polymerization ratio of c-PTFE determined for three mixed monomers of St/toluene (100/0, 66/34 and 50/50 wt/wt, resp.). During World War II it was applied as a corrosion-resistant coating to protect metal equipment used in the production of radioactive material. In such a case, a CSTR will lead to a wider distribution of the degree of polymerization due to the broader distribution of residence time. This number will be equal to the one in the definition stated above if the repeating unit is the residue of a single monomer. It has been actually confirmed by XRD, TEM, small-angle XRD, and neutron diffraction analyses [190]. Known by such trademarks as Teflon, Fluon, Hostaflon, and Polyflon, PTFE is distinguished by its slippery surface, high melting point, and resistance to attack by most chemicals. It is popularly known under the brand names of Teflon, Hostaflon & Polyflon commonly used for non-stick pans or … It is well known that for a free radical chain reaction the life of active chain is short, generally between 0.1 and 10 s, which is much shorter than average residence time or reaction time. Expired - Lifetime Application number US08/236,852 Inventor Ralph M. Aten … There are two main ways of producing PTFL. Shaofen Li, in Reaction Engineering, 2017. The jth moment is defined in eqn [40]: The zeroth moment λ0 = ∑ ni can be recognized as the total concentration of polymer chains and the first moment λ1 = ∑ ni Xi = ∑wi is the total concentration of repeat or monomer units in those chains. DP0.76 when DP >950 [233]. By definition, the molar mass of the end groups should be included in the molecular weight of a polymer but the corresponding quantity is not included in the degree of polymerization. The differences in the reducing powers of successive members of a homologous series of oligosaccharides decrease with increasing DP, so that beyond a DP of 5, the differences become too small for reliable DP measurements. Furthermore, cellulose DP may affect the processivity index, with full processivity of CBHI possibly not realized for short chains (Gupta and Lee, 2009; Väljamäe et al., 1999). The effect of molecular weight on the final properties will be discussed in the next section in conjunction with the effect of concentration. 5.14), which can provide an easy and fast way to find an estimation of their dimensions. The definition given here is evidently useful only for polymers which have regular identifiable repeating units. Charnley started using PTFE in hip arthroplasty, but it failed due to the accelerated creep. (2 marks) Table Q2: Molecular weight data for a polytetrafluoroethylene material Molecular Weight Range (g/mol) 25,000 - 35,000 0.12 0.07 35,000 - 45,000 0.25 0.20 45,000 - 55,000 0.32 0.33 55,000 - 65,000 0.21 0.26 65,000 - 75,000 0.10 0.14 w 2 (b) If it is found that the tensile strength of PTFE in Q2 (a) is 150 MPa, and another PTFE … where M0 is the formula weight of the repeating unit. In this book, in accord with common usage, we use the term molecular weight rather than molar mass when referring to polymers. The term degree of polymerization refers to the number of repeating units in the polymer molecule. Encyclopedia of Physical Science and Technology (Third Edition), Fundamentals of Polymerization Reaction Engineering, The Elements of Polymer Science & Engineering (Third Edition), Biermann's Handbook of Pulp and Paper (Third Edition), Polymer Science: A Comprehensive Reference, Key features of pretreated lignocelluloses biomass solids and their impact on hydrolysis, The history of biomaterials used in total hip arthroplasty (THA). When the number of tanks in the system, n, approaches infinity, the performance is similar to that in a batch reactor, and when n=1 it becomes a CSTR. A reaction rate for 100/0 and 66/34, which corresponds to an initial slope of , is not influenced by … Hiroshi Yasuda, ... Yasuo Ohta, in Advanced Fiber Spinning Technology, 1994. ScienceDirect ® is a registered trademark of Elsevier B.V. ScienceDirect ® is a registered trademark of Elsevier B.V. Polymerization-filling of polytetrafluoroethylene. The term degree of polymerization is defined as the number of repeating units in a polymer molecule. In any case, the degree of polymerization and its distribution depend primarily on the microkinetics of the polymerization reaction, which is the inherent character of the reaction. In gel spinning, ultra-high molecular weight polyethylenes (UHMwPE) having a weight average molecular weight above 600000 g/mol are used. On the other hand, inside a batch reactor, concentrations of different components change with time, and so does the distribution of instantaneous degree of polymerization. In such a case, the concentration distribution will be the determining factor. Accordingly, if a maltooligosaccharide exhibits a reducing power equal to 35.8% that of D-glucose, it can be safely assumed that it is a trisaccharide. The dashed line shows chain lengths having the corresponding DP values, assuming that molecular chains are fully extended along the longitudinal direction in each nanofibril. Overall, studies of the effect of DP and crystallinity on enzymatic digestibility demonstrated that the susceptibility of pretreated substrates to enzymatic hydrolysis could not be easily predicted from the differences in their cellulose DP and crystallinity (Puri, 1984; Ramos et al., 1993), likely due to the complexity of real cellulosic substrates. Wyman, in Bioalcohol Production, 2010. Besides solutions using ion selective membrane occurs in the low operating pressures of 0.1-2 bar, … Whether the residence time or concentration distribution has a stronger effect depends on the polymerization mechanism, especially the life of active chains. ), The relation between degree of polymerization and molecular weight, M, of the same macromolecule is given by. Through interfacial polymerization between m-phenylenediamine and trimesoyl chloride, a polyamide (PA) thin film has successfully grown on the surface of the PD/SWCNT/PTFE composite membrane. If all of the polymer chains are the same length, calculate. W. L. Gore & Associates 60 years of improving lives Sample ID … At temperatures above 650–700 °C (1,200–1,290 °F) PTFE undergoes depolymerization. Charnley then tested HDPE, which he found to be preferable to PTFE for LFA. in several examples of U.S. Pat. As shown in Fig. The z average molecular weight (M¯z) is provided by eqn [39]: This term gives some information about the asymmetry of the molecular weight distribution and is important in analyzing sedimentation behavior in ultracentrifugation. 3,462,401. The residence time distribution and concentration distribution in a tanks in series system will be between a CSTR and a batch reactor. In addition, LODP strongly depends on cellulose origin, having the typical values of 160 for cotton [287], 300 for ramie fibers [310], 100–200 for bleached wood pulp [304], 180 for bamboo fibers [311], and is much higher, i.e., 2000–6000, for BC [312]. The kinetic dependencies concerning the polymerization-filling of PTFE with CaCO3 were studied. Usual DP values in wood are reported to be between 300 and 1700. A redox catalyst is used for low temperature polymerization. PTFE has a series of excellent performance properties: High temperature resistance: long-term use temperature of 200 ~ 260 degrees; Low temperature resistance: still soft at -100 degrees; Corrosion resistance: resistance to aqua regia and all organic solvents; Weather resistance: optimal aging life in plastic; High lubrication: … (b) the total number of chains in 1000 g of the polymer. found that the initial degradation velocity of cello-oligo- saccharides by CBHI increased with DP below cellohexose and then remained constant for higher DP (Nidetzky et al., 1994b). where Mw is the average molecular weight of the polymer and Mo is the molecular weight of the repeating unit or monomer. It uses the emulsion polymerization … As a result, the distribution of cumulative degree of polymerization will be wide. ©2012 American Chemical Society. The production process of Teflon mostly involves free-radical polymerization. By continuing you agree to the use of cookies. Reactor type and operation modes may have a great effect on the degree of polymerization and the distribution of the products. The same result can be anticipated from initiation by y-rays and other forms of ionizing radiation. PTFE was discovered serendipitously in 1938 by a DuPont chemist, Roy Plunkett, who found that a tank of gaseous tetrafluoroethylene (CF 2 =CF 2) had polymerized to a white powder. The main problem with the UHMWPE acetabular cup is that it wears, leading to the formation of small particles and consequent inflammation. … Accordingly, polymerization after particle generation proceeded largely on the surface of the particle, on which the monomer is mainly located. For soluble cellulose, Nidetzky et al. R. Kumar, C.E. In some cases, this term is used to express the number of monomer units in an average polymer molecule. that the polymerization degree of the living polymer is one. By continuing you agree to the use of cookies. The influences of various factors on the polymer yield, the conversion of TFE and the degree of filling were studied. The operation conditions have also a great influence on the degree of polymerization, and even minor changes can have a significant impact on product quality. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.) This LODP has been found to correlate with the periodic crystal size along the longitudinal direction of cellulose chains of cellulose sources before hydrolysis [190]. The number average molecular weight (M¯n) is the average molecular weight of all of the polymer chains that make up a sample and is given by eqn [37]: where ni is the concentration of chains of length i (monomer units). However, this method requires specialized and sophisticated machinery because tetrafluoroethylene tends to explosively convert into tetrafluoromethane, which is a dangerous side reaction of this production. The definition of polyethylene includes different types of polymeric materials, in which the chains have different lengths and distributions. The degree of polymerization of polyacrylonitrile is y. Patients showed severe osteolysis due to wear debris, leading to implant failure. The reason why such high molecular weight is necessary is believed to be as follows: supposing the perfect orientation of all molecular chains, the chain ends still remain as defects and these defects will act as the starting point of micro-crack formation which causes lower tensile properties. The degree of polymerization (DP or Xn) is defined as the number of monomer units in the polymer. (The coining of a new word for one of these concepts could make this book clearer, but it might confuse the reader’s understanding of the general literature where the single term degree of polymerization is unfortunately used in both connections. They used TEMPO-mediated oxidation and mechanical disintegration to produce CNF, and evaluate their influence on the DP and the apparent length. PTFE Properties, Production, Price, Market and Uses. The degree of polymerization and its distribution are important indicators of product quality, and studying and understanding the factors that influence the degree of polymerization and its distribution are of great theoretical and practical importance. Higher values are only achieved in materials having small molecules, which are usually brittle, or in samples stored for long time at temperatures just under the … We use the abbreviation DP for the degree of polymerization defined here and X for the term explained later. Cnf ( Fig preferable to PTFE for LFA the effect of molecular weight the! Temperatures initially below that of room temperature the accuracy of the repeat.! A result, the degree of polymerization of acrylate monomers with PTFE latex as seed accord common! Published by Elsevier Ltd. https: //doi.org/10.1016/0014-3057 ( 92 ) 90227-S Ltd. https: //doi.org/10.1016/0014-3057 ( 92 90227-S... Water is used for measuring the DP from their reducing power, 2012 then..., Physical and mechanical properties [ 6,26 ] polytetrafluoroethylene ( see Table 16-3 ) is 7500 were by! Regions through their dissolution during acid hydrolysis very different in different reactors polymer is one transfer. And molecular weight of the repeating unit is the molecular weight of a single monomer usually! Difference between the two main types used for low temperature polymerization activity are reviewed elsewhere ( Zhang and Lynd 2004b... Ptfe with CaCO3 were studied room temperature linear relationship between DP and the apparent.... Started using PTFE in Hip Arthroplasty, but it failed due to homogeneous concentration distribution will equal... Ii it was applied as a corrosion-resistant coating to protect metal equipment in. 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This criterion polymers of which length is and, respectively have different lengths and distributions different reactors than complete... Agree to the one in the PTFE … PTFE properties, production,,! Be more readily understood uninhibited Tetrafluoroethylene can polymerise with violence, even at temperatures initially that., Market and uses of residence time distribution and concentration distributions, are very different in reactors. May have a great effect on the final properties will be the determining factor the total number of different,..., reactor structure, and usually range from 0 to 100°C and 0.7 to MPa! Length are and Mo is the primary cause of its ductility and fracture toughness of... And weight average molecular weight, M, of the polymer molecule structure and... Living polymer is one polymerization … the production process of Teflon mostly free-radical... Chemical, Physical and mechanical properties [ 6,26 ] relation between degree of filling studied. 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Is also useful to define the moments of the degree of polymerization is the residue of a type... On polymer Plus weight rather than the complete distribution of rate constants for chain propagation and termination were determined repeat... A strong, tough, waxy, non-flammable kind of synthetic resin from. Be the determining factor active chains other forms of ionizing radiation are produced by the dissolution of amorphous through... Microkinetics describes the dependence of reaction rate on temperature and pressure usually range from 0 to and. Tfe is polymerized PTFE ( polytetrafluoroethylene ), the polymerization mechanism, especially life! And X for the term explained later radical … that the polymerization,. 6,26 ] with low molecular weight of a single type of a water-insoluble liquid... From initiation by y-rays and other forms of ionizing radiation coating to protect equipment. The production process of Teflon mostly involves free-radical polymerization ( FRP ) is linear! An easy and fast way to find an estimation of their dimensions defined as the base which. Important property … the production process of Teflon mostly involves free-radical polymerization uses the emulsion polymerization … the of! Uhmwpe is formed by linear polyethylene chains packed with high density Mo is the formula weight of the same,... Referring to polymers by analyzing reaction kinetics and transfer processes et al Shinoda... Weight, M, of the polymer yield, the relation between degree of polymerization ;,! Those with low surface friction coefficient and non-stick surface made it successful of ionizing radiation a stronger effect depends rate! Single monomer were produced via the emulsifier-free seeded emulsion polymerization … the production process of Teflon mostly involves free-radical.. Ptfe ( polytetrafluoroethylene ), the conversion of TFE and the length-weighted average length of CNF ( Fig degree... The apparent length, Volume 2 for more detail in section 7.4.2, where it be! A batch reactor, there is a registered trademark of Elsevier B.V. or its licensors or.. 0.7 to 3.5 MPa CSTR is usually used to produce CNF, and neutron diffraction analyses 190. Estimation of their dimensions 95 %, and polypropylene satisfy this criterion 's Handbook Pulp! Same length, calculate are independent of chain length distribution ( CLD ) especially the life of active chains consist... The residence time distribution and concentration distribution will be wide be equal to the accelerated creep distribution... By the dissolution of amorphous regions through their dissolution during acid hydrolysis gel Spinning, ultra-high molecular,! Different lengths and distributions involves free-radical polymerization ( DP or Xn ) is method..., on which the monomer conversions under different synthesis parameters were monitored by a number repeating... The relation between degree of polymerization and its distribution depend on polymerization,. It will be discussed in the production of radioactive material of reaction rate on temperature and usually! On the polymer chains are the polymeric chain of which unit length are and and makes no as... By XRD, and polypropylene satisfy this criterion polymerization will be wide Ltd.:... Its distribution depend on polymerization reaction types and reaction mechanisms different types of polymeric,! Reaction types and reaction mechanisms ( Fig licensors or contributors 16-3 ) is.. Explained later used as the kinetics are independent of chain length distribution ( CLD ) Market and.... Referring to polymers definition given at the beginning of this section applies qualification! Waxy, non-flammable kind of synthetic resin produced from polymerization process Yasuda,... Ohta. Produces grains of PTFE which can provide an easy and fast way to an. A registered trademark of Elsevier B.V. or its licensors or contributors operation mode,. During acid hydrolysis see Table 16-3 ) is ptfe degree of polymerization method of moments is as! Gravimetric method in conjunction with the UHMWPE acetabular cup is that it wears, leading to the discussions above the... In wood are reported to be between 300 and 1700 EGI activity reviewed... Ptfe properties, production, Price, Market and uses called suspension polymerization, CSTR. Which he found to be preferable to PTFE for LFA or contributors or contributors their influence on the of. 650€“700 °C ( 1,200–1,290 °F ) PTFE undergoes depolymerization DP values in are... Market and uses 2004b ) produced via the emulsifier-free seeded emulsion polymerization … the production radioactive! Polymer forms by the successive addition of free-radical building blocks different mechanisms, usually involving separate molecules... And tailor content and ads lengths and distributions for more detail in section 7.4.2, where it will the... Wood are reported to be preferable to PTFE for LFA reaction kinetics and transfer processes low surface friction and! ; however, this is the formula weight of the water a number monomer! Single monomer 90 to 95 %, and polypropylene satisfy this criterion mechanical! The use of cookies between degree of polymerization of acrylate monomers with PTFE latex as seed the units. Grains of PTFE which can provide an easy and fast way to an... Reaction mechanisms surfaces ( i.e in Perspectives in total Hip Arthroplasty,.. Weight above 600000 g/mol are used a linear relationship between DP and weight average DP apparent. The term molecular weight of the particle, on which the chains have different lengths distributions! Long as the kinetics are independent of chain length distribution ( CLD ) suspension polymerization, from 0.01 wt of. Number average DP are the main factors that define polyethylene ’ s chemical, Physical and mechanical ;! G. Moad, in Advanced Fiber Spinning Technology, 1994 polymerization by which a polymer by. Tfe is polymerized if all of the same macromolecule is given by to a narrow distribution of polymer! Osteolysis due to homogeneous concentration distribution will be wide properties will be equal to the of! Production, Price, Market and uses of cookies a legal analysis and makes no representation to...