title: A process for melt grafting itaconic anhydride onto polyethylene

authors: Hanipah, Suhaiza Hanim

subjects: itaconic anhydride

abstract: Currently, extensive research in using bio‐derived polymers is being done, highlighting the
importance of sustainable, green polymeric materials. Some sustainable alternatives to
synthetic polymers include lignin, starch, cellulose or blends of these with petroleum‐based
polymers.
In New Zealand, large quantities of animal derived proteins are available at very low cost,
making it ideal as a sustainable alternative to petroleum‐derived polymers. However, the
processability of most proteins is very difficult, but can be improved by blending with synthetic
polymers, such as polyolefins. To improve, the compatibility between these substances, a
functional monomer could be grafted onto the polyolefin chain. Using an appropriate functional
group, the polyolefin could then react with certain amino acids residues in the protein. Lysine
and cystein are the two most appropriate amino acid residues because of their reactivity and
stability at a wide pH range.
In this study, free radical grafting of itaconic anhydride (IA) onto polyethylene was investigated.
IA was selected because it is capable of reacting with polyethylene and amino acid residues,
such as lysine. The objective of the research was to identify and investigate the effect of
reaction parameters on grafting. These were: residence time, temperature, initial monomer
concentration as well as peroxide concentration and type. Grafting was characterized in terms
of the degree of grafting (DOG), percentage reacted and the extent of side reactions.
The reaction temperature was taken above the melting point of the polyethylene, monomer
and decomposition temperature of the initiator. It was found that above 160 C polymer
degradation occurred, evident from sample discolouration. A higher degree of grafting can be
achieved by increasing the initial monomer concentration up to a limiting concentration. The
highest DOG achieved was about 1.2 mol IA per mol PE, using 2 wt% DCP. When using 2 wt %
peroxide, the limiting concentration was found to be 6 wt% IA, above which no improvement in
DOG was achieved. It was found that DCP is much more effective at grafting, compared to DTBP
because DTBP is more prone to lead to side reactions than DCP.
iv
It was found that a residence time of 168 seconds resulted in the highest DOG, corresponding to
4 extrusions in series. However, it was also found that an increase in residence time resulted in
an increase in polymer degradation. The tensile strength of PE decreased after two extrusions
when using DTBP, and three extrusions, when using DCP. Young's modulus decreased only
slightly, while all samples showed a dramatic decrease in ductility, even after one extrusion. It
was concluded that degradation had a more pronounced effect on mechanical properties than
cross‐linking, and residence time should therefore not exceed three extrusions in series, which
corresponded to about 126 seconds.
It can be concluded that a high reaction temperature and high initiator concentration lead to a
low degree of grafting, accompanied by high cross‐linking and increased degradation. On the
other hand, high monomer concentration and high residence time lead to a high degree of
grafting.
Optimising grafting is therefore a trade off between maximal DOG and minimising side reactions
such as cross‐linking and degradation and optimal conditions do not necessarily correspond to a
maximum DOG. Other factors, such as the use of additives to prevent degradation should also
be investigated and may lead to different optimum conditions.

text: A process for melt grafting itaconic anhydride onto polyethylene Currently, extensive research in using bio‐derived polymers is being done, highlighting the
importance of sustainable, green polymeric materials. Some sustainable alternatives to
synthetic polymers include lignin, starch, cellulose or blends of these with petroleum‐based
polymers.
In New Zealand, large quantities of animal derived proteins are available at very low cost,
making it ideal as a sustainable alternative to petroleum‐derived polymers. However, the
processability of most proteins is very difficult, but can be improved by blending with synthetic
polymers, such as polyolefins. To improve, the compatibility between these substances, a
functional monomer could be grafted onto the polyolefin chain. Using an appropriate functional
group, the polyolefin could then react with certain amino acids residues in the protein. Lysine
and cystein are the two most appropriate amino acid residues because of their reactivity and
stability at a wide pH range.
In this study, free radical grafting of itaconic anhydride (IA) onto polyethylene was investigated.
IA was selected because it is capable of reacting with polyethylene and amino acid residues,
such as lysine. The objective of the research was to identify and investigate the effect of
reaction parameters on grafting. These were: residence time, temperature, initial monomer
concentration as well as peroxide concentration and type. Grafting was characterized in terms
of the degree of grafting (DOG), percentage reacted and the extent of side reactions.
The reaction temperature was taken above the melting point of the polyethylene, monomer
and decomposition temperature of the initiator. It was found that above 160 C polymer
degradation occurred, evident from sample discolouration. A higher degree of grafting can be
achieved by increasing the initial monomer concentration up to a limiting concentration. The
highest DOG achieved was about 1.2 mol IA per mol PE, using 2 wt% DCP. When using 2 wt %
peroxide, the limiting concentration was found to be 6 wt% IA, above which no improvement in
DOG was achieved. It was found that DCP is much more effective at grafting, compared to DTBP
because DTBP is more prone to lead to side reactions than DCP.
iv
It was found that a residence time of 168 seconds resulted in the highest DOG, corresponding to
4 extrusions in series. However, it was also found that an increase in residence time resulted in
an increase in polymer degradation. The tensile strength of PE decreased after two extrusions
when using DTBP, and three extrusions, when using DCP. Young's modulus decreased only
slightly, while all samples showed a dramatic decrease in ductility, even after one extrusion. It
was concluded that degradation had a more pronounced effect on mechanical properties than
cross‐linking, and residence time should therefore not exceed three extrusions in series, which
corresponded to about 126 seconds.
It can be concluded that a high reaction temperature and high initiator concentration lead to a
low degree of grafting, accompanied by high cross‐linking and increased degradation. On the
other hand, high monomer concentration and high residence time lead to a high degree of
grafting.
Optimising grafting is therefore a trade off between maximal DOG and minimising side reactions
such as cross‐linking and degradation and optimal conditions do not necessarily correspond to a
maximum DOG. Other factors, such as the use of additives to prevent degradation should also
be investigated and may lead to different optimum conditions.

year: 2008

title: Maturation and biomechanical risk factors associated with anterior cruciate ligament injury: Is there a link? A systematic review

authors: Butcher, Anna J.

subjects: ACL

abstract: Objective: To establish the potential link between sex-specific maturation and biomechanical factors associated with ACL injury during dynamic tasks. Design: Systematic review. Literature search: Five databases (CINHAL®, Cochrane Library, PubMed®, Scopus®, and SPORTDiscus) were searched and monitored until 27 May 2024. Study selection criteria: Cross-sectional, cohort, case-control, or interventional studies reporting one or more biomechanical variable linked with ACL injury and which assessed participants across two or more maturation phases were considered eligible. Data synthesis: Studies were assessed for risk of bias using a modified version of the Newcastle Ottawa Scale and overall quality of evidence was rated using GRADE. Metrics and effect sizes were presented where available. Results: Eighteen included studies examined 400 males, 1377 females, and 315 participants of undefined sex across various maturation phases. The methodological quality of most studies (n = 16) was considered good, and satisfactory for two. Knee abduction angle, knee abduction moment, knee flexion angle, and ground reaction forces were most commonly reported. Knee abduction angles and moments and knee flexion angles were greater in late and post-pubertal females than males and pre-pubertal females during both landing and cutting tasks. When normalised for body mass, ground reaction forces were generally greater in males compared to females overall and for less mature participants for both sexes. Overall quality of evidence was low or medium across the four biomechanical measures. Conclusion: Sex-specific maturation considerations are important in the targeted development and implementation of ACL injury risk identification and prevention strategies.

text: Maturation and biomechanical risk factors associated with anterior cruciate ligament injury: Is there a link? A systematic review Objective: To establish the potential link between sex-specific maturation and biomechanical factors associated with ACL injury during dynamic tasks. Design: Systematic review. Literature search: Five databases (CINHAL®, Cochrane Library, PubMed®, Scopus®, and SPORTDiscus) were searched and monitored until 27 May 2024. Study selection criteria: Cross-sectional, cohort, case-control, or interventional studies reporting one or more biomechanical variable linked with ACL injury and which assessed participants across two or more maturation phases were considered eligible. Data synthesis: Studies were assessed for risk of bias using a modified version of the Newcastle Ottawa Scale and overall quality of evidence was rated using GRADE. Metrics and effect sizes were presented where available. Results: Eighteen included studies examined 400 males, 1377 females, and 315 participants of undefined sex across various maturation phases. The methodological quality of most studies (n = 16) was considered good, and satisfactory for two. Knee abduction angle, knee abduction moment, knee flexion angle, and ground reaction forces were most commonly reported. Knee abduction angles and moments and knee flexion angles were greater in late and post-pubertal females than males and pre-pubertal females during both landing and cutting tasks. When normalised for body mass, ground reaction forces were generally greater in males compared to females overall and for less mature participants for both sexes. Overall quality of evidence was low or medium across the four biomechanical measures. Conclusion: Sex-specific maturation considerations are important in the targeted development and implementation of ACL injury risk identification and prevention strategies.

year: 2024

title: He Piko, He Repo: Environmental DNA as a biomonitoring tool for wetland restoration

authors: Bird, Starsha

subjects: colonisation

abstract: Wetlands are biodiversity hotspots, harbouring distinctive species while providing numerous ecosystem services. Unfortunately, throughout human civilisation, they have been systematically degraded, resulting in a dramatic global loss in wetland extent, the establishment of invasive species and the extinction of many natives and, in Aotearoa New Zealand, impediment of the special connection Māori share with their repo (wetlands). Monitoring wetland biodiversity to take appropriate restorative action and minimise further degradation is imperative, particularly in the face of climate change. Environmental DNA (eDNA; genetic material released by organisms into the environment) is an increasingly popular non-invasive biomonitoring method that provides information about the presence or potential absence of species inhabiting a given ecosystem, but has yet to be optimised for wetland environments. My thesis aimed to address the consequences of colonisation on the relationship between Māori and their wetlands, and to explore the value eDNA holds for wetland biomonitoring. The first analysis (Chapter 2) delved into the past (post-European settlement; 1840s), the present (2023), and the future (2073) of Opuatia Wetland (Waikato, Aotearoa New Zealand) through a series of interviews with three individuals who whakapapa to (are connected with) Opuatia Wetland and its surroundings. I found that Opuatia Wetland once flourished with native biodiversity, and kai (food) was readily available. However, land confiscation by European settlers marked the downfall of this once productive and connected catchment such that it is presently in a fairly degraded state, dominated by exotic species, with Māori feeling disconnected from their whenua (land). Considering the future, the interviewees envisioned a revived abundance of native species and desire for restoration efforts to be facilitated by both mātauranga Māori (Māori knowledge) and science. The second analysis (Chapter 3) examined a publicly available eDNA database to retrieve data from 26 wetland sites across Aotearoa New Zealand to understand taxonomic diversity patterns. Here, I showed that DNA sequence composition varied across the motu (country), illustrating that varying environmental conditions among wetland types influences biodiversity. Notably, most sites were dominated by >50% exotic species. These findings highlight the value of publicly shared data for generating new insights, and the need for resource allocations to tackle the persistence of exotic species in wetland ecosystems. The third analysis (Chapter 4) focused on analysing biodiversity dynamics at a single wetland and tested various eDNA sampling techniques. I sampled four spatially distant sites across Opuatia Wetland at three time points during an austral spring and simultaneously obtained data from conventional taxonomic surveys, tested three different filter sizes, and assessed DNA degradation rates using foreign DNA. I found significant differences in biodiversity across time and space, and when using different eDNA collection filters. Foreign DNA persisted for up to one week post-release within a 10 m radius, and combining conventional and eDNA methods provided a more comprehensive overview of biodiversity patterns. These findings collectively showcased key changes in biodiversity, even over short spatial and temporal scales, and identified parameters to consider for wetland biodiversity monitoring and associated data interpretation. It is only a matter of time until the impacts of climate change and invasive species take firmer hold of Aotearoa New Zealand's distinctive and fragile environment. Undoubtedly, eDNA can be part of the solution to mitigate these challenges, owing to its versatility across ecosystem types, capacity to extend to various substrates, and accessibility for researchers and citizen scientists alike. As eDNA methods continue to improve and become integrated into ongoing biomonitoring schemes, building equitable and empowering relationships between Māori and researchers/government bodies will best ensure that Aotearoa New Zealand repo and other environments are maintained and conserved for future generations.

text: He Piko, He Repo: Environmental DNA as a biomonitoring tool for wetland restoration Wetlands are biodiversity hotspots, harbouring distinctive species while providing numerous ecosystem services. Unfortunately, throughout human civilisation, they have been systematically degraded, resulting in a dramatic global loss in wetland extent, the establishment of invasive species and the extinction of many natives and, in Aotearoa New Zealand, impediment of the special connection Māori share with their repo (wetlands). Monitoring wetland biodiversity to take appropriate restorative action and minimise further degradation is imperative, particularly in the face of climate change. Environmental DNA (eDNA; genetic material released by organisms into the environment) is an increasingly popular non-invasive biomonitoring method that provides information about the presence or potential absence of species inhabiting a given ecosystem, but has yet to be optimised for wetland environments. My thesis aimed to address the consequences of colonisation on the relationship between Māori and their wetlands, and to explore the value eDNA holds for wetland biomonitoring. The first analysis (Chapter 2) delved into the past (post-European settlement; 1840s), the present (2023), and the future (2073) of Opuatia Wetland (Waikato, Aotearoa New Zealand) through a series of interviews with three individuals who whakapapa to (are connected with) Opuatia Wetland and its surroundings. I found that Opuatia Wetland once flourished with native biodiversity, and kai (food) was readily available. However, land confiscation by European settlers marked the downfall of this once productive and connected catchment such that it is presently in a fairly degraded state, dominated by exotic species, with Māori feeling disconnected from their whenua (land). Considering the future, the interviewees envisioned a revived abundance of native species and desire for restoration efforts to be facilitated by both mātauranga Māori (Māori knowledge) and science. The second analysis (Chapter 3) examined a publicly available eDNA database to retrieve data from 26 wetland sites across Aotearoa New Zealand to understand taxonomic diversity patterns. Here, I showed that DNA sequence composition varied across the motu (country), illustrating that varying environmental conditions among wetland types influences biodiversity. Notably, most sites were dominated by >50% exotic species. These findings highlight the value of publicly shared data for generating new insights, and the need for resource allocations to tackle the persistence of exotic species in wetland ecosystems. The third analysis (Chapter 4) focused on analysing biodiversity dynamics at a single wetland and tested various eDNA sampling techniques. I sampled four spatially distant sites across Opuatia Wetland at three time points during an austral spring and simultaneously obtained data from conventional taxonomic surveys, tested three different filter sizes, and assessed DNA degradation rates using foreign DNA. I found significant differences in biodiversity across time and space, and when using different eDNA collection filters. Foreign DNA persisted for up to one week post-release within a 10 m radius, and combining conventional and eDNA methods provided a more comprehensive overview of biodiversity patterns. These findings collectively showcased key changes in biodiversity, even over short spatial and temporal scales, and identified parameters to consider for wetland biodiversity monitoring and associated data interpretation. It is only a matter of time until the impacts of climate change and invasive species take firmer hold of Aotearoa New Zealand's distinctive and fragile environment. Undoubtedly, eDNA can be part of the solution to mitigate these challenges, owing to its versatility across ecosystem types, capacity to extend to various substrates, and accessibility for researchers and citizen scientists alike. As eDNA methods continue to improve and become integrated into ongoing biomonitoring schemes, building equitable and empowering relationships between Māori and researchers/government bodies will best ensure that Aotearoa New Zealand repo and other environments are maintained and conserved for future generations.

year: 2023