Crystallization and Melting of PCL/PTHF Copolymers - METTLER TOLEDO

Crystallization and Melting of PCL/PTHF Copolymers

Sample

Three different PCL/PTHF copolymers in various ratios:
A: 100% PCL (modified); B 90:10 PCL/PTHF; C: 50:50 PCL/PTHF..
The purpose of the investigation was to measure the crystallization temperature of the samples when cooled from the melt and determine the influence of the copolymer on the modulus.

Background: Normally, bone fractures are held in place while they mend by encasing them in gauze bandages dipped in plaster of Paris (partly dehydrated gypsum). One serious disadvantage of this material, however, is that it loses stiffness if it comes in contact with water. Alternatives to plaster of Paris for medical applications were therefore sought. A suitable copolymer was developed consisting of poly-ε-caprolactone (PCL) and polytetrahydrofurane (PTHF). This material (PCL/PTHF) can be applied at body temperature, has the right stiffness and is insensitive to contact with water. 

 

Conditions

Measuring cells: DMA/STDA861e with shear clamp sample holder

                               DSC822e with 40 μm; frequency 1 Hz; offset control zero

Atmosphere: Static air

 

Interpretation

The first diagram shows the shear modulus (G') of sample C from the DMA heating/cooling experiment and the corresponding DSC heat flow curves. During heating, two endothermic effects are measured that correspond to the melting of the two components. The modulus drops during the first effect and the material is already soft at about 40 °C

The first two peaks during cooling show that PCL crystallizes in two stages; the third peak shows the crystallization of PTHF. During these transitions, the material regains the original stiffness, as the increase of the modulus shows. 

 

Conclusions

DSC and DMA are complementary tools that can be used to investigate the melting and crystallization behavior of PCL/PTHF copolymers. The phase transition temperatures measured by DMA agree well with results obtained by DSC and X-ray investigations. The results show that super-cooling during crystallization time therefore increases. PTHF seems to delay crystallization. This could be of interest for specific applications such as in medical use. The PTHF content also influences the modulus. This means that the mechanical properties of the material can be adjusted to optimum values depending on the application.

The results can be used to gain more information on the molecular properties of PCL/PTHF copolymers.

 

Crystallization and Melting of PCL/PTHF Copolymers | Thermal Analysis Handbook No.HB253 | Application published in METTLER TOLEDO TA Application Handbook Thermoplastics