Jim Song

The Effect of Chain Extender on Poly(3-hydroxybutyrate-co-3-hydroxyvalerate): Thermal Degradation, Crystallization, and Rheological Behaviours

Poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV), a semi-polycrystalline biopolymer from the polyhydroxyalkanonate family has in recent years become a commercial bioplastic with mechanical properties comparable to isotactic polypropylene and enhanced O2, CO2 and H2O barrier properties. However, its brittleness and sensitivity to thermal and hydrolysis degradations restrict its applications. To overcome the problems associated with degradation during processing blending of PHBV and an epoxy-functionalized chain extender (Joncryl® ADR-4368 S) was conducted in a twin screw extruder. The effect of concentration of the chain extender on thermal, crystallization and rheological behaviours of PHBV was investigated. Thermal gravimetric analysis results indicated improvement in the resistance to thermal decomposition of PHBV by introducing the chain extender. This was accompanied with calculation of thermal degradation activation energy (Ea) using the Flyn–Walls–Ozawa method which confirmed increase of Ea with the increase in content of the chain extender. The rheological behaviour and crystallization of modified PHBV was characterized by rotational rheometry and differential scanning calorimetry techniques, respectively. The results show that addition of chain extender enhanced viscosity of PHBV and also reduce the rate of crystallization.

Microwave foaming of starch-based materials (I) dielectric performance

Extruded pellets from starch-based materials have been heated and foamed under microwave radiation. The foaming mechanisms and effects of some additives on the dielectric properties of the materials have been investigated using a microwave calorimeter. A rapid increase in dielectric loss factor (ɛ″) has been found for all the tested materials foamable under microwave heating and the onset of the ɛ″ increase is considered to be correlated to glass transition. It has been found that extruded starch materials can be foamed at 15℃/min but the expansion level reduced compared with that of the same material foamed at higher heating rate. The incorporation of organic additives in starch-based materials generally led to significant decrease of their microwave foamability when glycerol and polyvinyl alcohol are used as the additives in the extruded pellets.

Extrusion foaming of PHBV

This paper reports work on extrusion foaming of poly(3-hydroxybutyrate-co-3-hydroxyvalerate) with a chemical blowing agent based on sodium bicarbonate and citric acid and calcium carbonate nucleation agent. It includes investigations in the effects of rheological behaviour of the polymer, blowing agent, nucleation agent and processing conditions on the foam density and morphology. The poly(3-hydroxybutyrate-co-3-hydroxyvalerate) is a natural biodegradable polyester with high crystallinity, low melt viscosity and slow crystallisation rate and high sensitivity to the thermal degradation at temperatures above its melting point, making it particularly difficult to control the foaming process. Use of negative gradient temperature profile was found beneficial to minimise the thermal degradation and achieve necessary melt strength to stabilise the cell structure. Solidification of the super-cooled polymer melt occurring at the die was discussed in relation to the selection of the temperature profile and rheological behaviour and solidification of the poly(3-hydroxybutyrate-co-3-hydroxyvalerate) characterised by rotational rheometry. In addition to extrusion foaming conditions, effect of the blowing and nucleation agents on rheology of the polymer, the cell refinement on foam density and morphology were discussed. The poly(3-hydroxybutyrate-co-3-hydroxyvalerate) was extruded with a twin screw extruder fitted with a strand die yielding up to 60% density reduction with uniform fine cell structure.

A Consumer-Centric Open Innovation Framework for Food and Packaging Manufacturing

Closed innovation approaches have been employed for many years in the food industry. But, this sector recently perceives its end-user to be wary of radically new products and changes in consumption patterns. However, new product development involves not only the product itself but also the entire manufacturing and distribution network. In this paper, we present a new ICT based framework that embraces open innovation to place customers in the product development loop but at the same time assesses and eventually coordinates the entire manufacturing and supply chain. The aim is to design new food products that consumers will buy and at the same time ensure that these products will reach the consumer in time and at adequate quantity. On the product development side, our framework enables new food products that offer an integrated sensory experience of food and packaging, which encompass customization, healthy eating, and sustainability.

Microwave foaming of starch-based materials (II) thermo-mechanical performance

The thermo-mechanical performance of extruded wheat starch/flour containing different additives was examined via microwave-heated thermo-mechanical analysis. Additionally, the dielectric property of the wheat starch-based materials was also studied using a microwave calorimeter. It has been found that when glycerol or polyvinyl alcohol was used as single additive in wheat starch, a content limit existed and using the additives at a concentration higher than the limit will lead to deterioration of the material’s microwave foamability. A good initial thermal expansion is essential for a proper foaming of the wheat starch-based materials; however, high enough dielectric loss factor (ɛ″) is also required for the formation of foam structure under microwave radiation. Glass transition temperature (Tg) for the extruded wheat starch materials was detected by microwave thermo-mechanical analysis at about 75–95°C when heated at 15°C/min; and for the foamable formulations, the foaming temperature (Tf) is generally 10–20°C higher than the corresponding Tg. Impurities like proteins play important roles in the microwave foaming of extruded wheat flour. Overall, the extruded wheat flour with additives is more difficult to foam under microwave heating than the wheat starch extruded from the similar formulations.

Biocomposite boards from wheat straw without addition of bonding agent

Abstract The present paper reports work in development of biocomposite boards compression moulded from wheat straw. Unlike most traditional wood based fibre/chip boards with addition of adhesives or bonding agents, attempt was made to utilise the lignin–hemicellulosic natural resin within straw as bonding agent, resulting in a class of ‘binderless’ and more natural biocomposite boards. The effects of straw preparation and compression moulding conditions on structural and mechanical properties of the binderless straw boards were studied systematically in terms of size of chopped straw, pretreatment and the combination of pressure and temperature during compression moulding. The bonding mechanisms of the natural resin in the straw biocomposites were investigated in terms of its mobilisation using NaOH pretreatment of straw and its redistribution to the straw interfaces during compression moulding process. Without any fractionation of straw or any additional adhesive bonding agent, the mechanical properties of the binderless straw boards were comparable to some commercially available wood and straw board products using addition of adhesives.

Structure and Compression Behavior of Macro-composite Starch Foams:

Using a method known as regular packing and stacking (RPS) technology, starch foams made by extrusion foaming of wheat flour can be converted by self-adhesion to produce bulk foams of any required sizes for much more broad applications. These block foams are reinforced by a network of the bonding interfaces and hence can be regarded as macrocomposites. The influence of the reinforcing interfaces on compression behavior of the RPS blocks was investigated by mechanical testing of foams with different geometry of the interface network and interface thickness. It is demonstrated that the interface network of the block foams can be designed to manipulate the macrostructure and compression behavior of the foam for protective packaging.

Extrusion fractionation of wheat straw for biocomposites utilising the entire straw constituents

This paper reports work in the extrusion fractionation of wheat straw and biocomposites utilising the entire constituents of straw. The effects of pre-treatment and extrusion conditions on fractionation of straw and mechanical properties of the biocomposites were studied systematically. It is demonstrated that twin screw extrusion can be used for effective fractionation of straw feedstock for production of biocomposites utilising the natural resin and fibre reinforcement without additional polymeric resin. In comparison with the conventional approaches where cellulose is extracted and compounded with resins, the self-reinforced biocomposites benefit from low material and processing costs as well as lower environmental impacts.

Effect of Calcium Carbonate on Crystallization Behavior and Morphology of Poly(3-Hydroxybutyrate-co-3-Hydroxyvalerate)

The effects of calcium carbonate (CaCO3) concentration on crystallization behaviors and morphology of poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) were investigated. Composites of PHBV with CaCO3 were prepared with filler loadings of low (5%wt) and high concentration (20%wt) and these were subsequently compared to unloaded PHBV. The morphologies of PHBV composites on the freeze-fractured specimens were examined using scanning electron microscopy (SEM). The SEM images revealed that increasing concentration of CaCO3 resulted in agglomeration. This agglomeration might affect crystal growth rate and mechanism. The crystal growth behavior of melt-crystallized PHBV with different amounts of CaCO3 was studied by polarized optical microscopy (POM), while the crystal structure was examined by X-ray diffraction (XRD). The rate of crystal growth determined from POM at selected crystallization temperatures revealed that the addition of a small amount of CaCO3 accelerated crystal growth rate, whereas excess amount of CaCO3 had the opposite effect. The POM images were also used to illustrate the change of crystal growth process presence of CaCO3. The unloaded PHBV clearly showed nucleation and growth mechanism, while PHBV composites displayed nucleation and then combination of crystals during the growth process. However, CaCO3 did not affect the crystal structureof any PHBV composite as observed by XRD. Molecular weight determination via gel permeation chromatography (GPC) indicated that there was no significant difference among PHBV composites.