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Polmeros sintticos:processamento e uso como
biomateriais
Luiz Henrique Catalani
Laboratrio de Biomateriais Polimricos
http://www2.iq.usp.br/docente/lhc/
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ConsiderePara polmeros, o termo peso
molecular ambguo porque cadamolcula no tem o mesmo nmero
e un a es repe vas. s asituao no-uniforme ocorre
devido ao processo qumico desntese do polmero.
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Anlise do peso molecular de um polmero
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A distribuio do peso molecular muda com o tempo depolimerizao.
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A habilidade das cadeias polimricas se
rearranjarem por processos de relaxaopermite que propriedades do polmero mudemcom o tempo ou com a temperatura.
Considere
Polmeros apresentam uma variedade depossveis associaes no estado slido. Almdisso, uma simples cadeia pode ter umatrajetria que passa atravs de mltiplos
estados de agregao. Estes fatores podemfazer que o comportamento do polmero noestado slido seja complexo.
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Temperature can have a profound effect onpolymer properties. Below the glass transition anamorphous PMMA polymer is a rigid glass.Above the glass transition it is a plastic solid. Forthis amphous polymer the glass transition is 4C.
As temperature is increased, tensile behaviorgoes from brittle failure to plastic deformation.
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The primary chain structure of polymers allow
different types of internal morphology to develop.These different morphologies strongly influencephysical behavior. Control of these morphologies
allow control of physical behavior.
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http://web.utk.edu/~mse/pages/Textiles/Polymer%20Crystallinity_files/image002.jpghttp://pslc.ws/mactest/crystal.htm
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Polmeros semicristalinos
http://dmseg5.cwru.edu/Classes/ENGR145-SU07/Lectures/L27su07-MechPropII.ppt#280,5,Slide 5
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Mecanismo de deformao microscpica
ures
/L27su
07-Mech
Prop
II.p
pt#275
,6,S
lide
6
http:/
/dmseg
5.c
wru.e
du
/Classes
/ENGR145-S
U07/Lec
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necking
CallisterFig. 16.5
slope = tensile modulus
http://dmseg5.cwru.edu/Classes/ENGR145-SU07/Lectures/L27su07-MechPropII.ppt#276,7,Slide 7
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Amorphous polymers are typically not in their lowest thermodynamic state whenthey are vitrified. Because non-crystalline polymer chains can undergo
temperature and time dependent relaxations, they will continue to relax towardsa lower thermodynamic state which is more dense. If this is done deliberately, itis called annealing. If it occurs spontaneously, it is called ageing.
Supercooled liquids and the glass transition,Pablo G. Debenedetti & Frank H. StillingerNATURE, VOL 410, MARCH 8, 2001, p. 259
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Cold crystallization
http://centrum.vslib.cz/centrum/itsapt/Summer2005/files/manich.pdf
http://ieeexplore.ieee.org/iel2/3195/9096/00404381.pdf?arnumber=404381
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Enthalpy recovery of two distinct amorphousregions can be observed. One represents thenoncrystalline interlamellar region, while theother represents the bulk amorphous region.
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In some cases it is possible for
portions of the polymer chainto crystallize forming a twophase, semi-crystallinematerial. The cr stalline hase
is rigid with a high modulus,while the amorphous phasehas a much lower modulus.Increasing the crystallinity will
increase the modulus of thematerial.
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The ability of a polymer chainto move can be constrained bycrosslinking. There are several
modes of crosslinking(entanglements, chemicalbonding, physical interaction).A r linkin in r
chain mobility decreases andthe stiffness of the materialincreases. Thermosets arehighly crosslinked three
dimensional polymer chainnetworks (Bakelite, Plexiglas,Epoxy Resins)
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Polmeros como materiais
O termo plstico frequentemente usado para se referir amateriais polimricos. Ele se refere a uma categoria demateriais que podem ser moldados em vrios formatos.
Termoplsticos: materiais polimricos que fluem em ummolde ou forma sob a influncia de calor e mantm o formatosob dresfriamento (e perde quando reaquecido).
Termofixos: materiais polimricos que so formados em ummolde sob a influncia de calor e so reticulados (cura)permanentemente no formato moldado. So insolveis einfusveis.
Geralmente, produtos polimricos so formados near-net-shapee no requerem acabamento (uma vantagem sobre oprocessamento de metais).
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Processamento de termoplsticos
Extruso
Foundations of Materials Science and Engineering, Smith and Hashemi, McGraw Hill, 2006
profile extrusion
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Moldagem porinjeo
Processamento de termoplsticos
Foundations of Materials Science and Engineering, Smith and Hashemi, McGraw Hill, 2006
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Moldagem de
sopro
Processamento de termoplsticos
Foundations of Materials Science and Engineering, Smith and Hashemi, McGraw Hill, 2006
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Processamento de termofixos
Foundations of Materials Science and Engineering, Smith and Hashemi, McGraw Hill, 2006
Moldagem porcompresso
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Fiao do fundido
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Biomateriais Polimricos
A maioria so sintticos (poucos so naturais)
As propriedades variam de:macios (hidrogis, lentes) elastmeros (cardiovasculares)
rgidos (ortopedia, odontologia)
composio qumica
estrutura macromolecular propr iedades macroscpicas
comportamento in ter fac ia l do mater ia l comsangue ou tec idos b io lgicos
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Critrios para uso
Propriedades fsicas e mecnicas apropriadasDevem ser livres de monmeros e materiais permeveisSer biocompatveis:
No deve induzir mudanas clnicas no ambienteimplantadoNo deve roduzir substncias txicas na
degradaoSe biodegradvel, deve ser bioabsorvvelSe biodegradvel, velocidade de degradaocompatvel com aplicao
Propriedades qumicas, fsicas e mecnicas estveisdurante implanteDeve ser esterilizvelBaixo custo
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Alguns polmeros usados como biomateriais
Polietileno
Polimetilmetacrilato (PMMA)
Politetrafluoroetileno (PTFE)
Poli(cloreto de vinila) (PVC)
Polidimetilsiloxano (Silicone)
Nylons
Poliesteres
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Polyethylene
five major grades:very low density,low density,linear low density,
high density,and ultra high molecular weight.
catheters,pharmaceutical bottles,non-woven fabrics,flexible tubing,bags
orthopedic implant fabricationespecially for knee and hip joint prostheses.
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Polyethylene chemistry
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MEDPOR Biomaterial
MEDPOR Surgical Implants are manufactured from linear high-densitypolyethylene. Polyethylene has a long history of use in surgical implants.MEDPOR Biomaterial allows for tissue ingrowth because of itsinterconnecting open pore structure. The porosity of MEDPOR Biomaterial
is maintained large with average pore sizes greater than 100 micro-metersand a pore volume in the 50 percent range. The firm nature of the materialallows carving with a sharp instrument without collapsing the porestructure.
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The temperature at which thepolymer chains become mobilewill determine the temperatureat which the material willsoften
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Sheets and blockstrim easily with
surgical scissors ora small scalpelblade.
Submerge theimplant in a hot,
sterile saline bath(180F) to softens.
Thicker implants
may be shapedwith large scalpels.
Gently bend the
implant to thedesired shape.
Multiple pieces of
implant materialmay be stackedand suturedtogether.
Hold the implant in
the final shape andallow to cool.
Proper rigid fixationtechniques allow
for stabilization ofthe implant.
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Photograph of femoral stem and
femoral head. The head may bemade out of metal or ceramic, andthe finish of the head may vary.
Photograph of the acetabularcomponents of a contemporary totalhip replacement. The shell is usually
made out of metal, and the linermay be ceramic, metal, orultra-high-molecular weightpolyethylene.
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Modification of UHMW polyethylene
wear behavior by crosslinking.
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Polimetilmetacrilato
vtreoTransparentebiocompatvel
Lentes ocularesDentes postiosCimento sseo
Bombas sangumeas
Membranas para dilise
-Poli(hidroxietil)metacrilato (PHEMA) usado em lentes de contatomacias (forma hidrogel)
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Poly(Methyl Methacrylate) Chemistry
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FDA concerned about use of PMMA cement in spineThe U.S. Food and Drug Administration (FDA) has expressed concern about
potential serious patient care issues involved with the use ofpolymethlymethacrylate (PMMA) bone cement in the spine. A physician might insertthe PMMA bone cement into vertebrae by various procedures, includingvertebroplasty and kyphoplasty. Orthopaedic surgeons should be alert to possible
. .
October 1999, the FDA reclassified PMMA bone cement as a Class II device for itsintended use "in arthroplastic procedures of the hip, knee and other joints for thefixation of polymer or metallic prosthetic implants to living bone." The use of adevice for other than its FDA-cleared indication is an off-label use. Physicians mayuse a device off-label if they believe, in their best medical judgment, that its use is
appropriate for a particular patient (e.g., tumors). The use of PMMA bone cement inthe spine is described in Academy educational courses, videotapes and publicationsfor educational purposes only. As is the Academys policy regarding all of itseducational offerings, the fact that the use of PMMA bone cement in the spine isdiscussed does not constitute an Academy endorsement of this use.
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Intraocular Lense
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Modern cataract operation in the 1990's involved sophisticated technology utilizingmicrosurgery on the cataract with delicate, controlled ultrasound removal of thecataract and the placement of a foldable intraocular lens made of acrylic or silicone.Amazingly, this is accomplished through a very small incision with special wound
construction that has, essentially, eliminated the need for sutures except on
infrequent occasions.
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PHAKIC INTRAOCULAR LENS(PIOL)
involves placement of a lens implant
inside the eye for the correction ofeither nearsightedness orfarsightedness. This lens becomesin effect an internal contact lensinside the eye rather than on the
surface of the eye. At the presenttime this lens is being studiedoutside the United States.
P l t t fl th l
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Polytetrafluoroethylene
very inertdense and crystallinevery low surface tension
low friction coefficient.
artificial ligaments and tendonsporous vascular grafts (foam)
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The Advanta SST is nothing short ofrevolutionary and is the only PTFE
graft that pulses and performs likenature intended, with little or noneedle hole bleeding or weeping.
Using state-of-the-art membranetechnology Atrium has crafted aperfect blend of biomaterial science
into the worlds most pulsatilevascu ar gra . s cons ruc e rom
an amazing hydrostatic protectionmembrane developed and patentedby Atrium. Our proprietary
trilaminate construction has beenengineered to meet or exceed all
surgical and performance strengthrequirements, with the benefit ofbeing extraordinarily supple withincredible vein-like handling
qualities.
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PVDF Ligament with Fixation Screw
Optimal ligament material: 100% PVDF braided monofilamentsHighest ligament stability > 500 NSuperb biocompatibility: PVDF-ligament / titanium-screwNewly designed connection between screw and ligament (patented
adhesive connection)Optimal handling: Integrated fixation screw and application needleTension free ligament fixation
Polyurethane
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Polyurethane
large family of polymersbiomedical applications polyurethane thermoplastic elastomershigh resistance to abrasion, tear, and fatiguegood biocompatibility
resistance to degradation in the biological environment
vascular rosthesesintra-aortic balloonspacemaker lead insulationcardiac valveswound dressingsbreast implants
facial reconstruction
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A PU is made by mixing together theingredient chemicals (isocyanate
and polyol) in predeterminedproportions, which then react toform the polymer.
Uniquely, PUs utilise simultaneouspolymerisation and shaping of thepart. The production of consistent
end products depends on mixing, inprec se ra o, e ngre en
chemicals and maintenance of theappropriate processingtemperatures. As the liquid
isocyanate and polyol react to formthe PU, the liquid mix becomes
increasingly viscous eventuallyforming a solid mass.
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Polyurethane Cardiac Valve
Carpentier-Edwards Pericardial
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The fully developed foreign body reactioncan debilitate the functional utility of amedical device.
Polyvinylchloride (PVC)
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Polyvinylchloride Chemistry
Polyvinylchloride (PVC)
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Unplasticized PVC has a Tg of85C, making it a rigid solid at roomtemperature suitable for plasticpipes. Adding a small amount ofplasticizerto PVC can lower the Tg
to 40C. This addition renders thePVC a soft, flexible material at roomtemperature, ideal for applications
PVC hose can, however, becomestiff and brittle in winter. In this case,
as in any other, the relation of theTg to the ambient temperature iswhat determines the choice of agiven material in a particularapplication.
Polyvinylchloride (PVC)
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o y y c o de ( C)
Changes in some hormones by low doses of di (2-ethyl hexyl) phthalate(DEHP), a commonly used plasticizer in PVC blood storage bags & medicaltubingINDIAN JOURNAL OF MEDICAL RESEARCH, Apr 2004 by Gayathri, N
S, Dhanya, C R, Indu, A R, Kurup, P A
The results indicated decrease in serum insulin, cortisol and liver glycogen, andincrease in blood glucose, serum T3 and T4 in rats receiving DEHP. These changes
.
hormones were also observed in the blood stored in DEHP plasticized blood bags.
Also evidence of carcinogenicity at this link
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This blood bag is made with medicalgrade PVC rolled film and filled with
Jiaxing Tianhe Pharmaceutical Co., Ltd.
,16G needle. For blood collection,preservation and transfusion
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Il PVC plastificato o semirigido il
materiale maggiormente utilizzatoper la produzione di sacche e tubiper trasfusioni di sangue grazie alleeccellenti propriet meccaniche, labassa tendenza alla formazione di
fish eyes, l'elevata purezza e laresistenza agli agenti chimici. Questimanufatti sono prodotti percalandratura o estrusione.
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Polydimethylsiloxane (Silicone)
excellent biocompatibility
flexibilityresistance to degradationoxygen permeabilityrelatively poor tear and abrasion resistance
cosmetic and reconstructive surgeryeye and ear prostheses
materials to aid the healing of damaged skin
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Polydimethylsiloxane Chemistry
methyl
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In a narrow decision, the Food andDrug Administration (FDA) decidedagainst allowing silicone gel breast
implants back on the market. Thisdebate was sparked by the worriesof the medical community that theimplants could cause cancer,autoimune and connective tissue
disorders among other problems.
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Pol (eth lene terephthalate) PET
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Poly(ethylene terephthalate) PET
PET belongs to the family of polyestersrigid crystalline
high melting polymereasily processed into various shapesgood mechanical properties and chemical resistance
excellent biocompatibility
woven vascular graftsartificial heart valves
sutural materialsligament and tendon prosthesessupporting meshes
Polyester Chemistry
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Polyester Chemistry
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The primary chain structure of polymers allowdifferent types of internal morphology to
develop. These different morphologies stronglyinfluence physical behavior.
Polyesters
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Precision parts such as injection-
molded winged luers are among themany medical products made from
polyester resins. Photo: EastmanChemical Co.
Polyester/Spandex Leg Bag Holder