3/28/2015 Customized Compounding Boosts Resilience in Harsh Conditions | Pumps & Systems

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&  Pumps)  مضخاتت  ووأأنظظمة  االشررقق  ااألووسطط  ووشمالل  أأفرريیقيیاSystems  MENA)  تفتتح  مكتبب  أألمبيیعاتت  ااألووررووبيMar  24,  2015

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Written  by:  Dr.  Joel  Bell  &  Will  Taber  (RTP  Company)

Published:  March  26,  2015

Pump  manufacturers  have  a  long,  successful  history  of  working  with  metals

and  are  familiar  with  the  beneficial  properties  they  deliver  in  a  variety  of

pumping  applications.  Similarly,  the  pump  industry  has  been  using

thermoplastics  in  pump  designs  for  several  decades  because  of  their  low

cost,  light  weight,  superior  chemical  resistance,  manufacturability  and  other

valuable—and  profitable—advantages.

While  unmodified  thermoplastic  resins  have  many  inherent  benefits,  they

also  pose  many  limitations  for  pump  applications  if  used  in  an  unmodified  form.  Chief  among  these

limitations  are  strength,  impact,  wear  resistance  and  flame-­retardant  properties  that  can  often  fall  short  of

those  same  properties  in  metals.

Despite  these  setbacks,  manufacturers  have  a  broad  range  of  options  for  enhancing  the  properties  of

unmodified  resins.  Compounders  can  add  combinations  of  reinforcing  fibers,  fillers  and  additives  to  a

carefully  selected  base  resin  to  create  a  high-­performance  compound  with  a  host  of  distinct  properties

instilled  into  a  single  material.  Many  manufacturers  are  frequently  surprised  at  the  diversity  of  properties

that  can  be  readily  built  into  a  compound—including  flame  retardancy,  impact  resistance,  strength,  wear

and  friction  resistance,  conductivity,  temperature  resistance,  chemical  resistance,  corrosion  resistance  and

colorability—to  deliver  the  exact  performance  criteria  that  they  have  specified.

Developing  the  Right  FormulationThe  job  of  the  compounder  is  to  first  understand  the  pump  application  and  its  challenges  and  then  consider

the  wide  variety  of  base  resins,  reinforcing  fibers,  fillers  and  additives  in  its  portfolio  to  develop  the  optimum

formulation.  Experienced  compounders  can  begin  with  lower  cost  base  resins  such  as  polypropylene  for

less  demanding  applications,  higher-­temperature  resins  such  as  polyphenylene  sulfide  (PPS)  and

polyetheretherketone  (PEEK)  for  more  demanding  thermal  and  wear  requirements,  or  fluoropolymers  such

as  polyvinylidene  fluoride  (PVDF)  and  ethylene  tetrafluoroethylene  (ETFE)  for  extreme  chemical

resistance.

From  this  base  resin,  the  compounder  works  to  create  the  composite  using  a  combination  of  reinforcing

fibers,  fillers  and  additives  such  as  long  glass  fiber  to  increase  mechanical  properties  or  the  internal

lubricant  polytetrafluoroethylene  (PTFE)  for  reduced  wear  and  friction.  Other  options  include  aramid  fibers,

graphite  or  ceramic  powders  for  improved  wear  resistance,  halogenated  or  non-­halogenated  flame-­

retardant  additives,  conductive  carbon  fiber,  and  pigments  and  dyes  for  custom  color  options.

Depending  on  the  challenges  presented  by  the  application,  some  of  these  formulations  may  be  created

from  scratch  with  no  base  resin  in  mind,  while  others  may  begin  with  previously  developed  resin/additive

combinations.

During  the  development  stage,  manufacturers  often  continually  request  additional  properties.  For  example,

they  may  begin  by  requesting  that  strength  be  added  to  the  compound.  Later,  they  may  ask  for  a  flame

retardant  and  finish  off  by  requesting  that  the  compound  be  made  the  company's  corporate  color.  An

experienced  compounder  is  often  able  to  accommodate  these  requests,  but  compounding  technology

requires  balance  and  compromise  of  ingredients  and  properties.  Sometimes,  when  one  performance

criteria  is  added,  issues  may  arise  with  others.  For  example,  imparting  conductive  properties  may  result  in

reduction  of  overall  strength  or  impact  resistance  for  which  the  formulation  must  compensate.  A  skilled

compounder  understands  how  different  constituents  of  the  formulation  interact,  as  well  as  their  advantages

Reinforcing  additives  combined  with  a  carefully  selected  base  resincan  create  a  high-­performance  compound  for  any  application.

Customized  Compounding  Boosts  Resiliencein  Harsh  Conditions

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compound  strength ATEX RTP  Company Joel  Bell Will  Taber

and  limitations.

Maximizing  Compound  Strength

Compounders  use  a  variety  of  reinforcing  fibers,  including  short  glass  fiber,  carbon  fiber  and  very  longglass  fiber,  to  achieve  maximum  strength  and  other  specific  properties.  The  manner  in  which  these  fibersare  introduced  into  the  melt  stream  and  the  sizing  chemistry  used  on  the  fiber  are  key  considerations  whenstriving  to  maximize  material  strength.

As  an  example,  a  manufacturer  was  looking  to  convert  components  of  a  fluid-­handling  pump  that  moveswaste  products  at  up  to  155  gallons  per  minute  (gpm)  from  metal  to  a  thermoplastic.  Polypropylene  wasconsidered  because  its  weight  savings  were  projected  at  20  to  50  percent  and  the  manufacturing  processwas  relatively  quick  and  easy.  Because  of  the  inherent  properties  of  polypropylene,  the  manufacturerachieved  excellent  chemical  resistance  but  was  unable  to  obtain  the  required  level  of  tensile  strength.

After  carefully  analyzing  the  application,  the  compounder  selected  a  40  percent  long  glass  fiber  reinforcedpolypropylene,  with  a  17,500  pounds  per  square  inch  (121  megapascal)  tensile  strength  and  5.0  foot-­pounds  per  inch  (267  joule/meter)  notched  izod  impact  strength  that  met  all  structural  and  impactrequirements  of  the  application.  The  long  glass  fiber  reinforcement,  with  its  unique  balance  of  strength  andimpact  properties,  allowed  the  manufacturer  to  benefit  from  the  use  of  a  thermoplastic  compound,  ascenario  that  otherwise  would  have  been  impossible  because  of  the  inherent  strength  deficit  of  thepolypropylene  alone.

Incorporating  Superior  Wear  Resistance

Another  property  of  enormous  consequence  to  pump  manufacturers  is  wear  and  abrasion  resistance.Despite  the  large  number  of  moving  parts,  pumps  must  provide  a  long  useful  life  with  minimal  downtimewhile  maintaining  effective  operation  in  corrosive,  high-­temperature  and  other  inhospitable  environments.

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3/28/2015 Customized Compounding Boosts Resilience in Harsh Conditions | Pumps & Systems

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MORE  PUMP  INDUSTRY  NEWS  »

&  Pumps)  مضخاتت  ووأأنظظمة  االشررقق  ااألووسطط  ووشمالل  أأفرريیقيیاSystems  MENA)  تفتتح  مكتبب  أألمبيیعاتت  ااألووررووبيMar  24,  2015

Pumps  &  Systems  MENA  Opens  EuropeanSales  OfficeMar  24,  2015

Flowserve  to  Supply  Valves  to  Klabin'sNew  Pulp  Mill  in  BrazilMar  23,  2015

Dow  Announces  Affiliation  with  the  Valueof  Water  CoalitionMar  20,  2015

KSB  Urges  Action  on  WastewaterReclamation  for  World  Water  DayMar  20,  2015

Water  for  People  and  TOMS  Roasting  Co.Provide  over  100,000  Weeks  of  Water  toGlobal  CommunitiesMar  20,  2015

                     

Written  by:  Dr.  Joel  Bell  &  Will  Taber  (RTP  Company)

Published:  March  26,  2015

To  incorporate  wear  resistance,  the  compounder  can  select  an  additive

technology,  such  as  PTFE,  perfluoropolyether  (PFPE),  silicone,  carbon  and

aramid  fibers,  graphite  and  molybdenum  disulfide.  As  illustrated  in  Figure  1,

wear  resistance  (per  American  Society  for  Testing  and  Materials  D3702)

can  be  improved  in  inherently  wear-­resistant  materials  such  as  nylon  6/6

and  acetal  (POM)  by  incorporating  PTFE  alone  or  in  combination  with

PFPE.

Figure  1.  Wear  resistance  of  unmodified  vs.  modified  materials  (Graphics  courtesy  of  RTP  Company).

Another  common  scenario  for  pumps  used  in  corrosive  environments  is  selecting  PPS—a  highly  chemically

resistant  thermoplastic  with  excellent  thermal  stability—and  building  in  required  wear  resistance  with  the

addition  of  carbon  fibers  used  in  conjunction  with  PTFE.  This  particular  type  of  compound  has  been  highly

successful  in  pump  vane  applications.

All  fiber  reinforcement,  fillers  and  additives  have  some  considerations,  and  the  compounder  must

understand  them.  For  example,  mating  surfaces,  applied  loads  and  speeds,  and  operating  temperatures

influence  wear  and  friction  along  with  the  wear  package  used.

Compounding:  A  Key  to  ATEX  SuccessATEX  is  a  legal  guideline  based  on  two  European  Union  directives  that  describe  what  equipment  and

protective  systems  are  allowed  in  an  environment  with  a  potentially  explosive  atmosphere.  Derived  from

the  French  title  of  the  94/9/EC  directive  Appareils  destinés  à  être  utilisés  en  ATmosphères  Explosives,

ATEX  is  a  concern  for  thousands  of  manufacturers  worldwide.  Often,  it  is  a  race  to  meet  stringent

conductivity  standards  so  that  products  can  continue  to  be  used  in  mines  and  other  potentially  explosive

environments.  Ironically,  these  are  many  of  the  same  environments  where  the  light  weighting,  strength  and

corrosion  resistance  provided  by  thermoplastic  compounds  have  become  so  valuable  (see  Figure  2).

To  maintain  the  use  of  thermoplastics  in  these  applications,  manufacturers  can  work  with  compounders  to

find  the  appropriate  conductive  technology  from  possibilities  such  as  carbon  fibers,  carbon  nanotubes,

Reinforcing  additives  combined  with  a  carefully  selected  base  resincan  create  a  high-­performance  compound  for  any  application.

Customized  Compounding  Boosts  Resiliencein  Harsh  Conditions

Pump  Ed  101

Pump  Repair

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3/28/2015 Customized Compounding Boosts Resilience in Harsh Conditions | Pumps & Systems

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Figure  2.  Centrifugal  pump  impeller  utilizing  PPSwith  carbon  fiber  and  PTFE  for  maximum  strength

and  wear  resistance

Figure  3.  ATEX-­compliant  pump  utilizing  aconductive  PP  with  glass  fiber  reinforcement

Author  Bio:  

Dr.  Joel  Bell  is  the  international  technology  manager  for  RTP  Company  in  Winona,  Minnesota.  He  holds  a

Doctor  of  Philosophy  in  materials  science  engineering  from  the  University  of  Minnesota-­Twin  Cities.  He

may  be  reached  at  jbell@rtpcompany.com  or  507-­454-­6900.

Will  Taber  is  industrial  market  manager  for  RTP  Company  in  Winona,  Minnesota.  He  holds  a  bachelor\'92s

in  plastics  engineering  technology  from  Pittsburg  State  University  and  an  MBA  in  finance  from  the

University  of  Kansas.  He  may  be  reached  at  wtaber@rtpcompany.com  or  507-­454-­6900.

Tags:   March  2015 Harsh  Conditions compounding thermoplastic additives

compound  strength ATEX RTP  Company Joel  Bell Will  Taber

inherently  conductive  polymers  and  carbon  black.

Some  of  these  impact  the  strength  of

thermoplastics,  so  the  compounder  must  create  the

right  formula  to  maintain  all  the  properties  required

by  the  application.  The  compounder  also  needs  to

understand  that  ATEX  compliance  might  require  a

combination  of  several  other  properties,  such  as

flame  retardancy,  impact  resistance  and  thermal

resistance—most  of  which  are  well  within  reach  of

compounded  thermoplastics.

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