title: Improving Impact Properties of Novatein through Polymer Blending and Reactive Extrusion

authors: Smith, Matthew J.

subjects: Biopolymer

abstract: Novatein is a brittle thermoplastic made from protein and requires impact strength modification before it can be used in a wider variety of applications, such as in the agricultural, horticultural and meat processing industries. Polymer blending is often used for improving material properties cost effectively. This study aimed to improve the energy absorbing properties of Novatein through manipulating the morphology of blends and assessing the factors that are important during this process; these were, the choice of polymer, composition, viscosity ratio, interfacial tension and chemical interactions.

Novatein was blended with either elastomeric core-shell particles, polyethylene (PE), or biodegradable polybutylene adipate-co-terephthalate (PBAT) using twin-screw extrusion to allow for sufficient mixing and residence time for chemical interactions or reactions to form. Materials were characterized for mechanical (tensile and impact testing), thermal (dynamic mechanical analysis and differential scanning calorimetry) and morphological (microscopy and solvent extraction) properties.

The greatest increase in energy absorption occurred in blends containing core-shell particles, but only above a critical particle concentration. This was attributed to good particle dispersion, efficient stress transfer to the particles and a decrease in interparticle distance, allowing the matrix to elongate freely during fracture, forming fibrillar structures. When the particle content was high, the protein secondary structure became more ordered in these fibrils during fracture. It was suggested that the change in protein conformation contributed to the increase in energy absorption, along with matrix yielding.

In contrast, in-situ formation of morphologies required for impact strength modification through reactive extrusion of Novatein and modified polyethylene proved difficult due to the viscosity ratio and interfacial tension. In most Novatein/PE blends these factors were not favorable for PE to form stable, dispersed droplets. However, blends containing ethylene-based zinc ionomer performed well in mechanical testing, with high elongation and greatly increased impact strength attributed to strong ionic interactions at the interface. However, no changes in protein secondary structure were detected, suggesting that improvements to impact properties were as a result of morphological changes in these blends.

To preserve the biodegradability of Novatein, PBAT was used instead of PE to achieve the same goal. The compatibilization of Novatein/PBAT blends was explored using dual compatibilizer systems whereby it was found that a compatibilizer system of epoxy functionalized chain extender (Joncryl ADR4368) and imidazole catalyst brought about increased energy absorption compared to poly-2-ethyl-2-oxazoline (PEOX) with polymeric diphenyl methane diisocyanate (pMDI). Compatibilization dramatically reduced PBAT’s phase size and led to a well distributed PBAT dispersion, required for improved impact properties. However, the dispersed phase coalesced at very low PBAT concentration (~ 5 wt. % PBAT) due to inappropriate viscosity ratio and interfacial tension. The onset of coalescence can typically be modified by manipulating these factors.

The viscosity ratio and interfacial tension were altered by increasing the water content in Novatein, which is included as a processing aid, leading to a reduction in blend viscosity ratio and an increase in interfacial tension. As water was removed after injection moulding, water was not considered a plasticizer at this stage.
Coalescence of PBAT was reduced when the viscosity ratio decreased and interfacial tension increased in uncompatibilized blends, with a further reduction in domain size upon compatibilization with Joncryl/imidazole. Impact strength was higher in compatibilized blends attributed to this fine domain size and improved interfacial adhesion. Increasing PBAT content to 30 wt. % showed higher impact strength, however a co-continuous morphology formed at this composition, demonstrating that composition can override the effect of viscosity ratio and interfacial tension.

Novatein thermoplastic protein can be impact strength modified through polymer blending or the incorporation of elastomeric particles, however this process is not straightforward. The unique nature of Novatein, whereby the viscosity is exceptionally high during processing and the lack of a traditional melt causes viscosity to be insensitive to temperature, make blending particularly difficult. Interfacial interaction and good particle dispersion are crucial when incorporating pre-synthesized impact modifiers into Novatein, whilst careful consideration is needed of factors such as viscosity ratio, interfacial tension and chemical interactions when blending Novatein with reactive polymers. The morphology formed during blending, along with composition and interfacial interaction, heavily influenced energy absorption. The theories presented for impact strength modification in conventional polymers can be applied here, yet additional considerations need to be made when aiming to modify impact strength in unconventional polymers such as Novatein.

text: Improving Impact Properties of Novatein through Polymer Blending and Reactive Extrusion Novatein is a brittle thermoplastic made from protein and requires impact strength modification before it can be used in a wider variety of applications, such as in the agricultural, horticultural and meat processing industries. Polymer blending is often used for improving material properties cost effectively. This study aimed to improve the energy absorbing properties of Novatein through manipulating the morphology of blends and assessing the factors that are important during this process; these were, the choice of polymer, composition, viscosity ratio, interfacial tension and chemical interactions.

Novatein was blended with either elastomeric core-shell particles, polyethylene (PE), or biodegradable polybutylene adipate-co-terephthalate (PBAT) using twin-screw extrusion to allow for sufficient mixing and residence time for chemical interactions or reactions to form. Materials were characterized for mechanical (tensile and impact testing), thermal (dynamic mechanical analysis and differential scanning calorimetry) and morphological (microscopy and solvent extraction) properties.

The greatest increase in energy absorption occurred in blends containing core-shell particles, but only above a critical particle concentration. This was attributed to good particle dispersion, efficient stress transfer to the particles and a decrease in interparticle distance, allowing the matrix to elongate freely during fracture, forming fibrillar structures. When the particle content was high, the protein secondary structure became more ordered in these fibrils during fracture. It was suggested that the change in protein conformation contributed to the increase in energy absorption, along with matrix yielding.

In contrast, in-situ formation of morphologies required for impact strength modification through reactive extrusion of Novatein and modified polyethylene proved difficult due to the viscosity ratio and interfacial tension. In most Novatein/PE blends these factors were not favorable for PE to form stable, dispersed droplets. However, blends containing ethylene-based zinc ionomer performed well in mechanical testing, with high elongation and greatly increased impact strength attributed to strong ionic interactions at the interface. However, no changes in protein secondary structure were detected, suggesting that improvements to impact properties were as a result of morphological changes in these blends.

To preserve the biodegradability of Novatein, PBAT was used instead of PE to achieve the same goal. The compatibilization of Novatein/PBAT blends was explored using dual compatibilizer systems whereby it was found that a compatibilizer system of epoxy functionalized chain extender (Joncryl ADR4368) and imidazole catalyst brought about increased energy absorption compared to poly-2-ethyl-2-oxazoline (PEOX) with polymeric diphenyl methane diisocyanate (pMDI). Compatibilization dramatically reduced PBAT’s phase size and led to a well distributed PBAT dispersion, required for improved impact properties. However, the dispersed phase coalesced at very low PBAT concentration (~ 5 wt. % PBAT) due to inappropriate viscosity ratio and interfacial tension. The onset of coalescence can typically be modified by manipulating these factors.

The viscosity ratio and interfacial tension were altered by increasing the water content in Novatein, which is included as a processing aid, leading to a reduction in blend viscosity ratio and an increase in interfacial tension. As water was removed after injection moulding, water was not considered a plasticizer at this stage.
Coalescence of PBAT was reduced when the viscosity ratio decreased and interfacial tension increased in uncompatibilized blends, with a further reduction in domain size upon compatibilization with Joncryl/imidazole. Impact strength was higher in compatibilized blends attributed to this fine domain size and improved interfacial adhesion. Increasing PBAT content to 30 wt. % showed higher impact strength, however a co-continuous morphology formed at this composition, demonstrating that composition can override the effect of viscosity ratio and interfacial tension.

Novatein thermoplastic protein can be impact strength modified through polymer blending or the incorporation of elastomeric particles, however this process is not straightforward. The unique nature of Novatein, whereby the viscosity is exceptionally high during processing and the lack of a traditional melt causes viscosity to be insensitive to temperature, make blending particularly difficult. Interfacial interaction and good particle dispersion are crucial when incorporating pre-synthesized impact modifiers into Novatein, whilst careful consideration is needed of factors such as viscosity ratio, interfacial tension and chemical interactions when blending Novatein with reactive polymers. The morphology formed during blending, along with composition and interfacial interaction, heavily influenced energy absorption. The theories presented for impact strength modification in conventional polymers can be applied here, yet additional considerations need to be made when aiming to modify impact strength in unconventional polymers such as Novatein.

year: 2018

title: Ecological values of Hamilton urban streams (North Island, New Zealand): constraints and opportunities for restoration

authors: Collier, Kevin J.

subjects: biodiversity

abstract: Urban streams globally are characterised by degraded habitat conditions and low aquatic biodiversity, but are increasingly becoming the focus of restoration activities. We investigated habitat quality, ecological function, and fish and macroinvertebrate community composition of gully streams in Hamilton City, New Zealand, and compared these with a selection of periurban sites surrounded by rural land. A similar complement of fish species was found at urban and periurban sites, including two threatened species, with only one introduced fish widespread (Gambusia affinis). Stream macroinvertebrate community metrics indicated low ecological condition at most urban and periurban sites, but highlighted the presence of one high value urban site with a fauna dominated by sensitive taxa. Light-trapping around seepages in city gullies revealed the presence of several caddisfly species normally associated with native forest, suggesting that seepage habitats can provide important refugia for some aquatic insects in urban environments. Qualitative measures of stream habitat were not significantly different between urban and periurban sites, but urban streams had significantly lower hydraulic function and higher biogeochemical function than periurban streams. These functional differences are thought to reflect, respectively, (1) the combined effects of channel modification and stormwater hydrology, and (2) the influence of riparian vegetation providing shade and enhancing habitat in streams. Significant relationships between some macroinvertebrate community metrics and riparian vegetation buffering and bank protection suggest that riparian enhancement may have beneficial ecological outcomes in some urban streams. Other actions that may contribute to urban stream restoration goals include an integrated catchment approach to resolving fish passage issues, active reintroduction of wood to streams to enhance cover and habitat heterogeneity, and seeding of depauperate streams with native migratory fish to help initiate natural recolonisation.

text: Ecological values of Hamilton urban streams (North Island, New Zealand): constraints and opportunities for restoration Urban streams globally are characterised by degraded habitat conditions and low aquatic biodiversity, but are increasingly becoming the focus of restoration activities. We investigated habitat quality, ecological function, and fish and macroinvertebrate community composition of gully streams in Hamilton City, New Zealand, and compared these with a selection of periurban sites surrounded by rural land. A similar complement of fish species was found at urban and periurban sites, including two threatened species, with only one introduced fish widespread (Gambusia affinis). Stream macroinvertebrate community metrics indicated low ecological condition at most urban and periurban sites, but highlighted the presence of one high value urban site with a fauna dominated by sensitive taxa. Light-trapping around seepages in city gullies revealed the presence of several caddisfly species normally associated with native forest, suggesting that seepage habitats can provide important refugia for some aquatic insects in urban environments. Qualitative measures of stream habitat were not significantly different between urban and periurban sites, but urban streams had significantly lower hydraulic function and higher biogeochemical function than periurban streams. These functional differences are thought to reflect, respectively, (1) the combined effects of channel modification and stormwater hydrology, and (2) the influence of riparian vegetation providing shade and enhancing habitat in streams. Significant relationships between some macroinvertebrate community metrics and riparian vegetation buffering and bank protection suggest that riparian enhancement may have beneficial ecological outcomes in some urban streams. Other actions that may contribute to urban stream restoration goals include an integrated catchment approach to resolving fish passage issues, active reintroduction of wood to streams to enhance cover and habitat heterogeneity, and seeding of depauperate streams with native migratory fish to help initiate natural recolonisation.

year: 2009

title: An exploration of the role of semantic relations in the theory and practice of translation (with special reference to English/Māori and Māori/English translation)

authors: Roa, Tom

subjects: clause relations

abstract: It is over forty years since Beekman and Callow, working within the context of the tagmemic tradition, drew attention to the potential significance so far as the theory and practice of translation are concerned of inter-propositional relations (also referred to as ‘discourse relations’, 'semantic relations', ‘semantico-pragmatic relations’, 'rhetorical relations’ and ‘clause relations’).  Since then, the importance of these relations has been increasingly acknowledged within linguistics and a range of other disciplines, including artificial intelligence. In spite of this, inter-propositional relations remain largely unexplored by the vast majority of those involved in translation. My aim in this research project was to determine (a) what impact, if any, a short training course in inter-propositional relations and inter-propositional relational signalling had on novice Māori-English/ English-Māori translators, and (b)  what impact my own understanding of these relations has had on my own practice as a translator. In connection with this, I conducted two studies.  

In the first of these studies, two small groups of novice translators were asked to translate seven text segments - some from English into te reo Māori, others from te reo Māori into English. They were then given a two-day workshop on inter-propositional relations and inter-propositional relational signalling in English and te reo Māori. No translation exercises were included in the workshop. The novice translators were then asked to translate the same text segments again. Comparison of the two sets of translations revealed some interesting differences, the second set indicating a higher level of sensitivity to inter-propositional relations and their signalling in the original text segments. This resulted in, it is argued here, translations that more accurately reflect authorial intentions as indicated in the source texts (see Chapter 3). In connection with this, it is relevant to note that, as indicated in the introductory chapter (Chapter 1) and in parts of the literature review (Chapter 2), while some of those involved in the Western tradition of translation theory and practice have argued that authorial intention is largely irrelevant in relation to textual interpretation, this essentially post-structural positioning is not available to those involved in translating indigenous texts within the context of indigenous worldviews.

In the second study, I used self-reflective think-aloud protocols to record my thoughts during the process of translating, from English into te reo Māori, text segments from five very different texts, all of these translations having been commissioned by different commissioning agencies. I then, making reference to the think-aloud transcripts, compared the source texts with the translations to determine the ways in which my reflections on inter-propositional relations and their signalling had impacted on the translations (Chapter 4).

My overall conclusion is that an understanding of inter-propositional relations and inter-propositional relational signalling can make a positive contribution to the theory and practice of translation and should be included in translator training and in the teaching of additional languages more generally (Chapter 5).

text: An exploration of the role of semantic relations in the theory and practice of translation (with special reference to English/Māori and Māori/English translation) It is over forty years since Beekman and Callow, working within the context of the tagmemic tradition, drew attention to the potential significance so far as the theory and practice of translation are concerned of inter-propositional relations (also referred to as ‘discourse relations’, 'semantic relations', ‘semantico-pragmatic relations’, 'rhetorical relations’ and ‘clause relations’).  Since then, the importance of these relations has been increasingly acknowledged within linguistics and a range of other disciplines, including artificial intelligence. In spite of this, inter-propositional relations remain largely unexplored by the vast majority of those involved in translation. My aim in this research project was to determine (a) what impact, if any, a short training course in inter-propositional relations and inter-propositional relational signalling had on novice Māori-English/ English-Māori translators, and (b)  what impact my own understanding of these relations has had on my own practice as a translator. In connection with this, I conducted two studies.  

In the first of these studies, two small groups of novice translators were asked to translate seven text segments - some from English into te reo Māori, others from te reo Māori into English. They were then given a two-day workshop on inter-propositional relations and inter-propositional relational signalling in English and te reo Māori. No translation exercises were included in the workshop. The novice translators were then asked to translate the same text segments again. Comparison of the two sets of translations revealed some interesting differences, the second set indicating a higher level of sensitivity to inter-propositional relations and their signalling in the original text segments. This resulted in, it is argued here, translations that more accurately reflect authorial intentions as indicated in the source texts (see Chapter 3). In connection with this, it is relevant to note that, as indicated in the introductory chapter (Chapter 1) and in parts of the literature review (Chapter 2), while some of those involved in the Western tradition of translation theory and practice have argued that authorial intention is largely irrelevant in relation to textual interpretation, this essentially post-structural positioning is not available to those involved in translating indigenous texts within the context of indigenous worldviews.

In the second study, I used self-reflective think-aloud protocols to record my thoughts during the process of translating, from English into te reo Māori, text segments from five very different texts, all of these translations having been commissioned by different commissioning agencies. I then, making reference to the think-aloud transcripts, compared the source texts with the translations to determine the ways in which my reflections on inter-propositional relations and their signalling had impacted on the translations (Chapter 4).

My overall conclusion is that an understanding of inter-propositional relations and inter-propositional relational signalling can make a positive contribution to the theory and practice of translation and should be included in translator training and in the teaching of additional languages more generally (Chapter 5).

year: 2016