and PP are possible. The long analysis times and the inefficiency in separating PE
and EP copolymers are the only limitations of TREF.
2.2.2.1 Aim
In the present application, the capabilities of CRYSTAF for the fractionation of
polyolefin blends shall be explored. CRYSTAF is faster than TREF and is based on
a single crystallization step of the blend components out of the solution. The
detection limit of each component shall be determined and compared to DSC for
investigation of blends of metallocene-catalysed PE and PP. The successful separation and quantification of blends of commercial HDPE, LDPE and PP shall be
demonstrated. Finally, the analysis of recycled polyolefins by CRYSTAF shall be
discussed. It shall be demonstrated that CRYSTAF can be the workhorse of the
polyolefin industry for routine analysis of complex polyolefin blends to obtain
direct quantitative results.
2.2.2.2 Materials
• Polymers. Laboratory products of metallocene-catalysed PE and PP, and commercial HDPE, LDPE and PP.
2.2.2.3 Equipment
• CRYSTAF system. CRYSTAF instrument model 200 (Polymer Char, Valencia,
Spain).
• Detector. Built-in dual wavelength IR detector with heated flow-through micro
cell at 150
C.
• Solvent. TCB.
• Crystallization protocol. Crystallization between 100
C and 30
C, at a rate of
0.1
C/min.
• Sample concentration. 30 mg in 30 mL TCB.
• DSC. Perkin-Elmer DSC 7 (Perkin-Elmer, Waltham, USA), heating and cooling
rates of 10
C/min were applied. DSC curves of the second heating cycle were
used for analysis.
• SEC. Waters 150 HT-SEC apparatus (Waters Inc., Milford, USA) equipped with
a differential refractometer, oven temperature 145
C, mobile phase TCB,
column set: Styragel 500 A ˚ + HT3 + HT4 + HT5 + HT6, flow rate 1 mL/min.
2.2.2.4 Preparatory Investigations
Blends of metallocene-catalysed PE and PP were analysed by SEC and DSC as a
first step. The molar masses of the blend components (PE 342 kg/mol and PP
143 kg/mol) are not very different. Therefore, SEC was not the technique of choice
for this separation. The MMDs for PE/PP blends of varying compositions are
shown in Fig. 2.31.
DSC separates with regard to melting or crystallization temperatures. PE melts
at 132
C while PP melts at 147
C. The difference is sufficiently large to obtain
well resolved melting peaks. As long as the concentration of PP exceeds 20 %, both
components can be easily identified; see Fig. 2.32. For blends containing low
54
2 Crystallization-Based Fractionation Techniques
and EP copolymers are the only limitations of TREF.
2.2.2.1 Aim
In the present application, the capabilities of CRYSTAF for the fractionation of
polyolefin blends shall be explored. CRYSTAF is faster than TREF and is based on
a single crystallization step of the blend components out of the solution. The
detection limit of each component shall be determined and compared to DSC for
investigation of blends of metallocene-catalysed PE and PP. The successful separation and quantification of blends of commercial HDPE, LDPE and PP shall be
demonstrated. Finally, the analysis of recycled polyolefins by CRYSTAF shall be
discussed. It shall be demonstrated that CRYSTAF can be the workhorse of the
polyolefin industry for routine analysis of complex polyolefin blends to obtain
direct quantitative results.
2.2.2.2 Materials
• Polymers. Laboratory products of metallocene-catalysed PE and PP, and commercial HDPE, LDPE and PP.
2.2.2.3 Equipment
• CRYSTAF system. CRYSTAF instrument model 200 (Polymer Char, Valencia,
Spain).
• Detector. Built-in dual wavelength IR detector with heated flow-through micro
cell at 150
C.
• Solvent. TCB.
• Crystallization protocol. Crystallization between 100
C and 30
C, at a rate of
0.1
C/min.
• Sample concentration. 30 mg in 30 mL TCB.
• DSC. Perkin-Elmer DSC 7 (Perkin-Elmer, Waltham, USA), heating and cooling
rates of 10
C/min were applied. DSC curves of the second heating cycle were
used for analysis.
• SEC. Waters 150 HT-SEC apparatus (Waters Inc., Milford, USA) equipped with
a differential refractometer, oven temperature 145
C, mobile phase TCB,
column set: Styragel 500 A ˚ + HT3 + HT4 + HT5 + HT6, flow rate 1 mL/min.
2.2.2.4 Preparatory Investigations
Blends of metallocene-catalysed PE and PP were analysed by SEC and DSC as a
first step. The molar masses of the blend components (PE 342 kg/mol and PP
143 kg/mol) are not very different. Therefore, SEC was not the technique of choice
for this separation. The MMDs for PE/PP blends of varying compositions are
shown in Fig. 2.31.
DSC separates with regard to melting or crystallization temperatures. PE melts
at 132
C while PP melts at 147
C. The difference is sufficiently large to obtain
well resolved melting peaks. As long as the concentration of PP exceeds 20 %, both
components can be easily identified; see Fig. 2.32. For blends containing low
54
2 Crystallization-Based Fractionation Techniques