A bone...

TEM P LATE Bao-Yi ChangElissa Robbins Elizabeth ImmenLisa Scoppettuolo FINAL PRESENTATION May 17, 2001

Injection Molding Thank you to Speed of Light for the Casting photograph

Iron or Stainless Steel Polymers: PLLA or PCL

To fabricate a bioresorbable bone plate To fabricate a bone plate with a modulus close to that of bone through selection of materials and processing conditions Mission/Goals

Injection Molding Used to fabricate plastic objects -CD cases, water bottles, toys Easy one step process Ideal for mass production

Injection Molding Machine Battenfeld 250 Mold Chamber Hopper Plasticating Unit Control System Equipment Specifications

Injection Mold Process 2. End Plastication 3. Close Mold 4. Begin Injection Mold 5. Eject Part 1. Begin Plastication screw nozzle

Mold -Obtaining Mold Blank -Design Process -Machining -Adjustments Plate Dimensions(in)

Experimental Runs Establishing Ideal IM Conditions Varying Parameters Product Testing….

Instron Tensile Testing

Results: Instron Testing

IM1: low screw speed, low pressure IM Parameters  Mechanics Bone plate, not shaped for tensile testing IM2: low screw speed, high pressure IM3: high screw speed, low pressure IM4: high screw speed, high pressure

Gel Permeation Chromatography PCL degrades by hydrolysis PCL was placed in water to simulate the body’s aqueous environment Hydrolytic cleavage of PCL chains  Decrease in molecular weight

Polymers with low melting points are typically: low molecular weight T m  Mw Differential Scanning Calorimetry Melting point of PCL = o C

Decision Tree

Bioglass Fibers Ceramic Particles: - Hydroxyapatite -  -tricalcium phosphate Fabricate bone plate from a completely bioresorbable COMPOSITE - Satisfy the mechanical requirements of bone plates - Mechanically superior to many bioresorbable homopolymers... Further Work and Study Future Plans Possible Reinforcers  -tricalcium phosphate (Ca 3 (PO 4 ) 2,  -TCP) is a bioresorbable ceramic

FTIR patterns of PDLLA, TCP, and a PDDLA/TCP composite (50 wt. % TCP) Poor adhesion between polymer matrix and ceramic reinforcer Poor mechanical properties Possible Problems :

- Melting and Hot Pressing - Twin Screw Extrusion - Pelletize Composite Mixture - Injection Molding: Viscosity (  ) is an important parameter Methods of fabricating a PCL/  -TCP bone plate:

“To fabricate a bone plate with a modulus of 3 GPa, the composite would have to be 90 % TCP by volume!” E composite = X TCP E TCP + (1-X TCP )E PCL (upper bound) E composite = 1 / [(X TCP / E TCP ) + (1-X TCP )/ E PCL ] (lower bound) Source: Ashby, M. Engineering Materials I. Feasibility of a PCL/  -TCP Composite

TemPlate’s Composite Bone Plate By hot pressing a composite material of volume fraction 90% PCL / 10%  -TCP, the modulus was increased by 60%.

Cost Analysis

$Purchase Mold: (Master Unit Die) = $400 $Design ($60/hr * 30hr) = $1800 $Machining ($52/hr * 35hr) = $ Total for Mold $4060 Polymer Injection Molding

Cost Analysis

Processing Cost Analysis $Battenfeld Machine Repair = $250 $Optimizing Initial Processing Conditions ($60/hr * 6hr) =$360 $Injection Molding 1000 plates ($60/hr * 40hr) = $ Total for IM $3010

Cost Analysis

$Polycaprolactone (Polysciences, Inc. ($200/kg*20kg) = $4000 Cost Analysis Material

$Mechanical testing (Instron) ($60/hr*10hr) = $600 Product Analysis Cost Analysis

$Overhead~ $7000 $Mold = $4060 $Injection Molding = $3010 $Materials = $4000 $Product Analysis= $ 600 Summary Cost Analysis = $18, Total Cost of 1000 bone plates

Cost Analysis $20/bone plate *Biomet.com competition * $168/bone plate