Vibrational spectroscopic studies of laboratory scale polymer melt processing : application to a thermoplastic polyurethane nanocomposite

A laboratory scale twin screw extruder has been interfaced with a near infrared (NIR) spectrometer via a fibre optic link so that NIR spectra can be collected continuously during the small scale experimental melt state processing of polymeric materials. This system can be used to investigate melt state processes such as reactive extrusion, in real time, in order to explore the kinetics and mechanism of the reaction. A further advantage of the system is that it has the capability to measure apparent viscosity simultaneously which gives important additional information about molecular weight changes and polymer degradation during processing. The system was used to study the melt processing of a nanocomposite consisting of a thermoplastic polyurethane and an organically modified layered silicate.

Scaffold development using 3D printing with a starch-based polymer

Rapid prototyping (RP) techniques have been utilised by tissue engineers to produce three-dimensional (3D) porous scaffolds. RP technologies allow the design and fabrication of complex scaffold geometries with a fully interconnected pore network. Three-dimensional printing (3DP) technique was used to fabricate scaffolds with a novel micro- and macro-architecture. In this study, a unique blend of starch-based polymer powders (cornstarch, dextran and gelatin) was developed for the 3DP process. Cylindrical scaffolds of five different designs were fabricated and post-processed to enhance the mechanical and chemical properties. The scaffold properties were characterised by scanning electron microscopy (SEM), differential scanning calorimetry (DSC), porosity analysis and compression tests

Preparation and characterisation of composites from starch and sugar cane fibre

The aim of this study was to prepare and characterise composites of Soluble potato starch or hydroxypropylated maize starch with milled sugar cane fibre (i.e., bagasse). Prior to the preparation of the starch-fibre composites, the ‘cast’ and the ‘hot-pressed’ methods were investigated for the preparation of starch films in order to select the preferred preparation method. The physicochemical and mechanical properties of films conditioned at different relative humidities (RHs) were determined through moisture uptake, crystallinity, glass transition temperature (Tg), thermal properties, molecular structure and tensile tests. Hot-pressed starch films have ~5.5% less moisture, twice the crystallinity (~59%), higher Tg and Young’s modulus than cast starch films. The VH-type starch polymorph was observed to be present in the hot-pressed films. The addition of bagasse fibre to both starch types, prepared by hot-pressing, reduced the moisture uptake by up to 30% (cf., cast film) at 58% RH. The addition of 5 wt% fibre increased the tensile strength and Young’s modulus by 16% and 24% respectively. It significantly decreased the tensile strain by ~53%. Fourier Transform infrared (FT-IR) spectroscopy revealed differences in hydrogen bonding capacity between the films with fibre and those without fibre. The results have been explained on the basis of the intrinsic properties of starch and bagasse fibres.

Moisture uptake and tensile properties of starch-sugar cane fibre films

THERE is an increasing need for biodegradable plastics because they are environmentally friendly and can replace petroleum-based non-degradable plastics which pollute the environment. Starch-derived films reinforced with sugar cane bagasse fibre, which are biodegradable, have been prepared and characterised by gravimetric analysis for moisture uptake, X-ray powder diffraction for crystallinity, and tensile testing for mechanical properties. Results have shown that the addition of bagasse fibre (5 wt%, 10 wt% or 20 wt%) to either (modified) potato starch (Soluble starch) or hydroxypropylated maize starch reduced moisture uptake by up to 30% at 58% relative humidity (RH). Also, the tensile strength and the Young’s Modulus increased up to 63% and 80% respectively, with the maximum value obtained with 5 wt% fibre at 58% RH. However, the tensile strain of the films significantly decreased by up to 84%. The results have been explained based on the crystallinity of the films and the intrinsic properties of starch and bagasse fibres.

Training program impact on thermoplastic immobilization for head and neck radiation therapy

Purpose: To determine whether uniform guidelines and training in the stabilization and formation of thermoplastic shells can improve the reproducibility of set-up for Head and Neck cancer patients. Methods and materials: Image based measurements of the planning and treatment positions for 35 head and neck cancer patients undergoing radical radiotherapy were analysed to provide a baseline of the reproducibility of thermoplastic immobilization. Radiation therapists (RT) were surveyed to establish a perception of their confidence in thermoplastic procedures. An evidence based staff training program was created and implemented. Set-up reproduction and staff perception were reviewed to measure the impact of the training program. Results: The mean (SD) 3D vectors of anatomical displacement, measured on the patient images, improved from 4.64 (2.03) for the baseline group compared to 3.02 (1.65) following training (p < 0.01). The proportion of 3D displacements of patient data exceeding 5 mm 3D vector was decreased from 37.1% to 5.7% (p < 0.001) and the 3 mm vector from 85.7% to 42.9% (p < 0.001). The post-training survey scores demonstrated improved confidence in reproducibility of set-up for head and neck patients. Conclusion: The Thermoplastic Shells Training Program has been found to improve the treatment reproducibility for head and neck radiation therapy patients. Uniform guidelines have increased RT confidence in thermoplastic procedures.

Moisture and tensile strength properties of starch-sugar cane nanofibre films

There is an increasing need for biodegradable, environmentally friendly plastics to replace the petroleum-based non-degradable plastics which litter and pollute the environment. Starch-based plastic film composites are becoming a popular alternative because of their low cost, biodegradability, the abundance of starch, and ease with which starch-based films can be chemically modified. This paper reports on the results of using sugar cane bagasse nanofibres to improve the physicochemical properties of starch-based polymers. The addition of bagasse nanofibre (2.5, 5, 10 or 20 wt%) to (modified) potato starch (‘Soluble starch’) reduced the moisture uptake by up to 17 % at 58 % relative humidity (RH). The film’s tensile strength and Young’s Modulus increased by up to 100 % and 200 % with 10 wt% and 20 wt% nanofibre respectively at 58% RH. The tensile strain reduced by up to 70 % at 20 wt% fibre loading. These results indicate that addition of sugar cane bagasse nanofibres significantly improved the properties of starch-based plastic films

Preparation and characterization of composites from starch with sugarcane bagasse nanofibres

This paper reports on the results of using unbleached sugar cane bagasse nanofibres (average diameter 26.5 nm; aspect ratio 247 assuming a dry fibre density of 1,500 kg/m3) to improve the physico-chemical properties of starch-based films. The addition of bagasse nanofibres (2.5 to 20 wt%) to modified potato starch (i.e. soluble starch) reduced the moisture uptake by up to 17 % at 58 % relative humidity. The film’s tensile strength and Young’s modulus increased by up to 100 % (3.1 to 6.2 MPa) and 300 % (66.3 to 198.3 MPa) respectively with 10 and 20 wt% fibre addition. However, the strain at yield dropped by 50 % for the film containing 10 wt% fibre. Models for composite materials were used to account for the strong interactions between the nanofibres and the starch matrix. The storage and loss moduli as well as the glass transition temperature (Tg) obtained from dynamic mechanical thermal analysis, were increased with the starch-nanofibre films indicating decreased starch chain mobility due to the interacting effect of the nanofibres. Evidence of the existence of strong interactions between the starch matrix and the nanofibres was revealed from detailed Fourier transform infra-red and scanning electron microscopic evaluation.

Injection velocity control of thermoplastic injection molding via a double controller scheme

Injection velocity has been recognized as a key variable in thermoplastic injection molding. Its closed-loop control is, however, difficult due to the complexity of the process dynamic characteristics. The basic requirements of the control system include tracking of a pre-determined injection velocity curve defined in a profile, load rejection and robustness. It is difficult for a conventional control scheme to meet all these requirements. Injection velocity dynamics are first analyzed in this paper. Then a novel double-controller scheme is adopted for the injection velocity control. This scheme allows an independent design of set-point tracking and load rejection and has good system robustness. The implementation of the double-controller scheme for injection velocity control is discussed. Special techniques such as profile transformation and shifting are also introduced to improve the velocity responses. The proposed velocity control has been experimentally demonstrated to be effective for a wide range of processing conditions.

Studies on glass transition and starch re-crystallization in wheat bread during staling using electrical impedance spectroscopy

Bread staling is a very complex phenomenon that is not yet completely understood. The present work explains how the electrical impedance spectroscopy technique can be utilized to investigate the effect of staling on the physicochemical properties of wheat bread during storage. An instrument based on electrical impedance spectroscopy technique is developed to study the electrical properties of wheat bread both at its crumb and crust with the help of designed multi-channel ring electrodes. Electrical impedance behavior, mainly capacitance and resistance, of wheat bread at crust and crumb during storage (up to 120 h) is investigated. The variation in capacitance showed the glass transition phenomenon at room temperature in bread crust after 96 h of storage with 18% of moisture in it. The resistance changes at bread crumb showed the starch recrystallization during staling.

Fungal colonization of sago starch in Papua New Guinea

Sago starch is an important source of dietary carbohydrates in lowland Papua New Guinea. Over the past 30 years there have been sporadic reports of severe illness following consumption of sago starch. A common assumption is that fungal metabolites might be associated with the illness, leading to the need for a more thorough investigation of the mycoflora of sago starch. Sago starch was collected from areas of high sago consumption in Papua New Guinea for fungal analysis (69 samples). Storage methods and duration were recorded at the time of collection and pH on arrival at the laboratory. Yeasts were isolated from all samples except two, ranging from 1.2 × 103 to 8.3 × 107 cfu/g. Moulds were isolated from 65 of the 69 samples, ranging from 1.0 × 102 to 3.0 × 106 cfu/g. Of 44 samples tested for ergosterol content, 42 samples showed the presence of fungal biomass. Statistical analyses indicated that sago starch stored for greater than five weeks yielded significantly higher ergosterol content and higher numbers of moulds than sago stored for less than five weeks. The method of storage was also shown to influence mould numbers with storage in natural woven fibre containers returning significantly greater numbers than present in other storage methods tested. Potentially mycotoxigenic genera of moulds including Aspergillus and Penicillium were commonly isolated from sago starch, and as such storage factors that influence the growth of these and other filamentous fungi might contribute to the safety of traditional sago starch in PNG.