Polimeros Sinteticos Como Biomateriais Aula 3

8/22/2019 Polimeros Sinteticos Como Biomateriais Aula 3

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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

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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




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Moldagem de

sopro




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Processamento de termofixos


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



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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.



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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

Polimeros Sinteticos Como Biomateriais Aula 3

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