Monitoring polymeric compounding processes inline with THz time-domain spectroscopy

Krumbholz, N.; Hochrein, Thomas; Vieweg, N.; Hasek, T.; Kretschmer, Karsten; Bastian, Martin; Mikulics, M.; Koch, Martin

doi:10.1016/j.polymertesting.2008.09.009

Cited by 119 publications

(48 citation statements)

References 19 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Other applications, for which it is anticipated that THz technologies will be increasingly implemented, span from plant physiology, 4 investigations of the historical and cultural artifacts 5 to monitoring industrial production processes. 6 A field which will most certainly have an impact on our daily life is short-range wireless communication with THz waves, i.e., the wireless local area network (LAN) of tomorrow. 7 Yet, a mature THz technology not only requires reliable and affordable sources and detectors but also devices which can be used to guide or manipulate THz waves.…”

mentioning

confidence: 99%

Highly birefringent, low-loss liquid crystals for terahertz applications

et al. 2013

Self Cite

View full text Add to dashboard Cite

With growing interest in switchable devices for the THz frequency range, there is a strong demand for liquid crystals (LC) exhibiting both a high birefringence and a low absorption. We present the refractive index and absorption coefficient of the liquid crystal mixtures 1852 and 1825 in the frequency range between 0.2 and 2.5 THz. Both mixtures are designed specifically for high birefringence Δn of 0.32 and 0.38, respectively, in the THz region. In addition, they show low absorption coefficients for both ordinary and extraordinary polarization. This low absorbance in combination with the high birefringence makes these LCs particularly well suited for applications in switchable devices for THz optics

show abstract

mentioning

confidence: 99%

Highly birefringent, low-loss liquid crystals for terahertz applications

et al. 2013

Self Cite

View full text Add to dashboard Cite

show abstract

“…Krumbholz et al [76] demonstrated the potential of an in-line monitoring method using a fibre-coupled THz spectrometer, to study the influence of temperature and pressure on molten PP. Measurements were performed in a custommade die at the end of a planetary gear extruder.…”

Section: Terahertz Spectroscopymentioning

confidence: 99%

Process monitoring and visualization solutions for hot-melt extrusion: a review

Saerens

Vervaet

Remon

et al. 2014

Journal of Pharmacy and Pharmacology

View full text Add to dashboard Cite

Objectives Hot-melt extrusion (HME) is applied as a continuous pharmaceutical manufacturing process for the production of a variety of dosage forms and formulations. To ensure the continuity of this process, the quality of the extrudates must be assessed continuously during manufacturing. The objective of this review is to provide an overview and evaluation of the available process analytical techniques which can be applied in hot-melt extrusion. Key Findings Pharmaceutical extruders are equipped with traditional (univariate) process monitoring tools, observing barrel and die temperatures, throughput, screw speed, torque, drive amperage, melt pressure and melt temperature. The relevance of several spectroscopic process analytical techniques for monitoring and control of pharmaceutical HME has been explored recently. Nevertheless, many other sensors visualizing HME and measuring diverse critical product and process parameters with potential use in pharmaceutical extrusion are available, and were thoroughly studied in polymer extrusion. The implementation of process analytical tools in HME serves two purposes: (1) improving process understanding by monitoring and visualizing the material behaviour and (2) monitoring and analysing critical product and process parameters for process control, allowing to maintain a desired process state and guaranteeing the quality of the end product. Summary This review is the first to provide an evaluation of the process analytical tools applied for pharmaceutical HME monitoring and control, and discusses techniques that have been used in polymer extrusion having potential for monitoring and control of pharmaceutical HME.

show abstract

“…Recently, there have been enormous efforts devoted to the fabrication of THz optical components [11][12][13][14][15][16][17][18]. Among the THz components, lenses and off-axis parabolic mirrors play a crucial role in THz-TDS systems, which are the basic optical elements for focusing and collimating THz waves.…”

Section: Introductionmentioning

confidence: 99%

“…Among the THz components, lenses and off-axis parabolic mirrors play a crucial role in THz-TDS systems, which are the basic optical elements for focusing and collimating THz waves. For example, planoconvex lenses are commonly used in THz-TDS systems of linear configuration [11]. The lenses operating in the THz frequency range are fabricated with various materials: high resistive silicon [12,13], polytetrafluoroethylene (PTFE, Teflon) [3,[12][13][14], high-density polyethylene (HDPE) [3,11,14], TPX [13], TOPAS [13,14], Zeonex [15], Picarin [16], micropowders [17], and polymeric compounds [18].…”

Section: Introductionmentioning

confidence: 99%

“…For example, planoconvex lenses are commonly used in THz-TDS systems of linear configuration [11]. The lenses operating in the THz frequency range are fabricated with various materials: high resistive silicon [12,13], polytetrafluoroethylene (PTFE, Teflon) [3,[12][13][14], high-density polyethylene (HDPE) [3,11,14], TPX [13], TOPAS [13,14], Zeonex [15], Picarin [16], micropowders [17], and polymeric compounds [18]. Also, special lenses such as off-axis metallic diffractive lens [19], diffractive paper lens [20], variable-focus lens using medical white oil [21], and THz Brewster lens [22] have also been reported recently.…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Terahertz lens made out of natural stone

et al. 2013

View full text Add to dashboard Cite

Terahertz (THz) time-domain spectroscopy probes the optical properties of naturally occurring solid aggregates of minerals, or stones, in the THz frequency range. Refractive index and extinction coefficient measurement reveals that most natural stones, including mudstone, sandstone, granite, tuff, gneiss, diorite, slate, marble, and dolomite, are fairly transparent for THz frequency waves. Dolomite in particular exhibits a nearly uniform refractive index of 2.7 over the broad frequency range from 0.1 to 1 THz. The high index of refraction allows flexibility in lens designing with a shorter accessible focal length or a thinner lens with a given focal length. Good agreement between the experiment and calculation for the THz beam profile confirms that dolomite has high homogeneity as a lens material, suggesting the possibility of using natural stones for THz optical elements.

show abstract

Monitoring polymeric compounding processes inline with THz time-domain spectroscopy

Cited by 119 publications

References 19 publications

Highly birefringent, low-loss liquid crystals for terahertz applications

Highly birefringent, low-loss liquid crystals for terahertz applications

Process monitoring and visualization solutions for hot-melt extrusion: a review

Terahertz lens made out of natural stone

Contact Info

Product

Resources

About