Reactive processing of polymers:functionalisation of ethylene-propylene diene terpolymer (EPDM) in the presence and absence of a co-agent and effect of functionalised EPDM on compatibilisation of poly(ethylene terephthalate)/EPDM blends

Ethylene-propylene diene terpolymer (EPDM) was functionalized with glycidyl methacrylate (GMA) during melt processing by free radical grafting with peroxide initiation in the presence and absence of a reactive comonomer trimethylolpropane triacrylate (Tris). Increasing the peroxide concentration resulted in an increase in the GMA grafting yield, albeit the overall grafting level was low and was accompanied by higher degree of crosslinking of EPDM which was found to be the major competing reaction. The presence of Tris in the grafting system gave rise to higher grafting yield produced at a much lower peroxide concentration though the crosslinking reactions remained high but without the formation of GMA-homopolymer in either of the two systems. The use of these functionalized EPDM (f-EPDM) samples with PET as compatibilisers in binary and ternary blends of PET/EPDM/f-EPDM was evaluated. The influence of the different functionalisation routes of the rubber phase (in presence and absence of Tris) and the effect of the level of functionality and microstructure of the resultant f-EPDM on the extent of the interfacial reaction, morphology and mechanical properties was also investigated. It is suggested that the mechanical properties of the blends are strongly influenced by the performance of the graft copolymer, which is in turn, determined by the level of functionality, molecular structure of the functionalized rubber and the interfacial concentration of the graft copolymer across the interface. The cumulative evidence obtained from torque rheometry, scanning electron microscopy, SEM, dynamic mechanical analysis (DMA), tensile mechanical tests and Fourier transform infrared (FTIR) supports this. It was shown that binary and ternary blends prepared with f-EPDM in the absence of Tris and containing lower levels of g-GMA effected a significant improvement in mechanical properties. This increase, particularly in elongation to break, could be accounted for by the occurrence of a reaction between the epoxy groups of GMA and the hydroxyl/carboxyl end groups of PET that would result in a graft copolymer which could, most probably, preferentially locate at the interface, thereby acting as an 'emulsifier' responsible for decreasing the interfacial tension between the otherwise two immiscible phases. This is supported by results from FTIR analysis of the fractionated PET phase of these blends which confirm the formation of an interfacial reaction, DMA results which show a clear shift in the T s of the blend components and SEM results which reveal very fine morphology, suggesting effective compatibilisation that is concomitant with the improvement observed in their tensile properties. Although Tris has given rise to highest amount of g-GMA, it resulted in lower mechanical properties than the optimized blends produced in the absence of Tris. This was attributed to the difference in the microstructure of the graft and the level of functionality in these samples resulting in less favourable structure responsible for the coarser dispersion of the rubber phase observed by SEM, the lower extent of T shift of the PET phase (DMA), the lower height of the torque curve during reactive blending and FTIR analysis of the separated PET phase that has indicated a lower extent of the interfacial chemical reaction between the phases in this Tris-containing blend sample. © 2005 Elsevier Ltd. All rights reserved.

PET/EPR blends properties in the presence of compatibilisers containing glycidyl methacrylite

Blends of PET with the different commercial co(ter)polymer compatibilisers were prepared and the effect of their glycidyl methacrylate (GMA) content and viscosity on the blend properties was determined. The efficiency of compatibilisation of the commercial co(ter)polymer in the ternary blends was examined and compared. For all the ternary blends (PET/EPR/co(ter)polymer, the PET content was fixed at 70 wt% of the total weight of the blends. Higher compatibilisation effect was found in PET/EPR blends compatibilised with the commercial copolymer ethylene glycidyl methacrylate (E-GMA8(5)) containing 8% GMA and MFI = 5 (g/10min) was achieved as reflected in the observed higher elongation at break when compared to corresponding blends compatibilised with the methyl acrylate containing terpolymer ethylene methyl acrylate glycidyl methacrylate EM-GMA8(6) containing 8% GMA and MFI = 6 (g/10min). The presence of methyl acrylate ester groups in the commercial terpolymer EM-GMA (containing similar amount of GMA and same MFI) resulted in low level of compatibilisation due to the possibility of a higher extent of branching and crosslinking resulting from the presence of the ester groups and this would be responsible for the observed lower elongation, and the less favourable morphology observed. Further, the more bulky structure of the terpolymer compared to the copolymer would give rise to a more difficult migration to the interface, thus lowering the efficiency of compatibilisation. However, the morphology of both blends compatibilised with either the terpolymer or the copolymer were not significantly different.

A techno-economic study of the recycling of mixed plastics to useful products

The techno-economic implications of recycling the components of mixed plastics waste have been studied in a two-part investigation: (a) An economic survey of the prospects for plastics recycling, the plastics waste arisings from retailing, building, automotive, light engineering and chemical industries have been surveyed by mans of questionnaires and interviews. This was partially successful and indicated that very considerable quantities of relatively clean plastics packaging was available in major department chains and household stores. The possibility of devising collection systems for such sources, which do not lead to any extra cost, have been suggested. However, the household collection of plastics waste has been found to be uneconomic due to high cost of collection, transportation and lack of markets for the end products. (b) In a technical study of blends of PE/PP and PE/PS which are found in admixture in waste plastics, it has been shown that they exhibit poor mechanical properties due to incompatibility. Consequently reprocessing of such unsegregated blends results in products of little technological value. The inclusion of some commercial block and graft copolymers which behave as solid phase dispersants (SPES) increase the toughness of the blends (e.g. EPDM in PE/PP blend and SBS in PE/PS blend). Also, EPDM is found to be very effective for improving the toughness of single component polypropylene. However, the improved Technical properties of such blends have been accompanied by a fast rate of photo-oxidation and loss of toughness due to the presence of unsaturation in SPD's. The change in mechanical properties occurring during oven ageing and ultra-violet light accelerated weathering of these binary and ternary blends was followed by a viscoelastonetric technique (Rheovibron) over 9,, wide range of temperatures, impact resistance at room temperature (20-41'G) and changes in functional groups (i.e. carbonyl and trans-1,4-polybutadiene). Also the heat and light stability of single and mixed plastics to which thiol antioxidants were bound to SPE1 segment have been studied and compared with conventional antioxidants. The long-term performance of the mixed plastics containing SPE1 have been improved significantly by the use of conventional and bound antioxidants. It is concluded that an estimated amount of 30000 tonnes/year of plastics waste is available from department chains and household stores which can be converted to useful end products. This justifies pilot-experiments in collaboration with supermarkets, recyclers and converters by use of low cost SPD's and additives designed to make the materials more compatible.

Identification of optically clear regions of ternary polymer blends using a novel rapid screening method

The application of a rapid screening method for the construction of ternary phase diagrams is described for the first time, providing detailed visualization of phase boundaries in solvent-mediated blends. Our new approach rapidly identifies ternary blend compositions that afford optically clear materials, useful for applications where transparent films are necessary. The use of 96-well plates and a scanning plate reader has enabled rapid optical characterization to be carried out by transmission spectrophotometry (450 nm), whilst the nature and extent of crystallinity was examined subsequently by wide angle X-ray scattering (WAXS). The moderating effect of cellulose acetate butyrate can be visualized as driving the position of the phase boundaries in poly(l-lactic acid)/polycaprolactone (PLLA/PCL) blends. More surprisingly, the boundaries are critically dependent on the molecular weight of the crystallizable PLLA and PCL, with higher molecular weight polymers leading to blends with reduced phase separation. On the other hand, the propensity to crystallize was more evident in shorter chains. WAXS provides a convenient way of characterizing the contribution of the individual blend components to the crystalline regions across the range of blend compositions. © 2013 Society of Chemical Industry.

Novel three-component blends based on poly(L-lactide)

A significant number of poly a-ester homologues of poly(L-lactide) (PLLA) have been synthesized and used in miscibility studies together with conventional isomeric diacid-diol polyester variants, poly ß-esters (based on ß-hydroxybutyrate (HB) and ß-hydroxyvalerate (HV)), poly e-caprolactone (PCL), poly e-caprolactone copolymers (e.g. poly(L-lactide-co-caprolactone), and a series of cellulose-based polymers (e.g. cellulose acetate butyrate (CAB), cellulose acetate propionate (CAP)). A combinatorial approach to rapid miscibility screening using 96-well plates and a uv-visible multi-wavelength plate reader has been developed enabling the clarity of PLLA-based multi-component blend films to be observed. Using these techniques and materials, the ternary phase compatibility diagrams of a range of three-component blend films was prepared, illustrating ranges of behavior varying from miscible blends giving rise to clear films to immiscible blends which are opaque. In this way, novel three-component blends of PLLA/CAB/PCL were developed which are miscible when the CAB content is more than 30%, PLLA less than 80% and PCL less than 60%.

Design and characterisation of novel blends of poly(lactic acid)

This thesis is concerned with the effect of polymer structure on miscibility of the three component blends based on poly(lactic acid) (PLA) with using blending techniques. The examination of novel PLA homologues (pre-synthesised poly(a-esters)), including a range of aliphatic and aromatic poly(a-esters) is an important aspect of the work. Because of their structural simplicity and similarity to PLA, they provide an ideal system to study the effect of polyester structures on the miscibility of PLA polymer blends. The miscibility behaviour of the PLA homologues is compared with other aliphatic polyesters (e.g. poly(e-caprolactone) (PCL), poly(hydroxybutyrate hydroxyvalerate) (P(HB-HV)), together with a series of cellulose-based polymers (e.g. cellulose acetate butyrate (CAB)). The work started with the exploration the technique used for preliminary observation of the miscibility of blends referred to as “a rapid screening method” and then the miscibility of binary blends was observed and characterised by percent transmittance together with the Coleman and Painter miscibility approach. However, it was observed that symmetrical structures (e.g. a1(dimethyl), a2(diethyl)) promote the well-packing which restrict their chains from intermingling into poly(L-lactide) (PLLA) chains and leads the blends to be immiscible, whereas, asymmetrical structures (e.g. a4(cyclohexyl)) behave to the contrary. a6(chloromethyl-methyl) should interact well with PLLA because of the polar group of chloride to form interactions, but it does not. It is difficult to disrupt the helical structure of PLLA. PLA were immiscible with PCL, P(HB-HV), or compatibiliser (e.g. G40, LLA-co-PCL), but miscible with CAB which is a hydrogen-bonded polymer. However, these binary blends provided a useful indication for the exploration the novel three component blends. In summary, the miscibility of the three-component blends are miscible even if only two polymers are miscible. This is the benefit for doing the three components blend in this thesis, which is not an attempt to produce a theoretical explanation for the miscibility of three components blend system.

Upgrading fast pyrolysis liquids:blends of biodiesel and pyrolysis oil

Fast pyrolysis liquid or bio-oil has been used in engines with limited success. It requires a pilot fuel and/or an additive for successful combustion and there are problems with materials and liquid properties. It is immiscible with all conventional hydrocarbon fuels. Biodiesel, a product of esterification of vegetable oil with an alcohol, is widely used as a renewable liquid fuel as an additive to diesel at up to 20%. There are however limits to its use in conventional engines due to poor low temperature performance and variability in quality from a variety of vegetable oil qualities and variety of esterification processes. Within the European Project Bioliquids-CHP - a joint project between the European Commission and Russia - a study was undertaken to develop small scale CHP units based on engines and microturbines fuelled with bioliquids from fast pyrolysis and methyl esters of vegetable oil. Blends of bio-oil and biodiesel were evaluated and tested to overcome some of the disadvantages of using either fuel by itself. An alcohol was used as the co-solvent in the form of ethanol, 1-butanol or 2-propanol. Visual inspection of the blend homogeneity after 48 h was used as an indicator of the product stability and the results were plotted in a three phase chart for each alcohol used. An accelerated stability test was performed on selected samples in order to predict its long term stability. We concluded that the type and quantity of alcohol is critical for the blend formation and stability. Using 1-butanol gave the widest selection of stable blends, followed by blends with 2-propanol and finally ethanol, thus 1-butanol blends accepted the largest proportion of bio-oil in the mixture. © 2013 Elsevier Ltd. All rights reserved.

Compatibilisation and stabilisation of immiscible polymer blends by reactive processing

The main objectives of this research were to develop optimised chemical compositions and reactive processing conditions for grafting a functional monomer maleic anhydride (MA) in polypropylene (PP), ethylene propylene diene monomer (EPDM) and mixtures of PP-EPDM, and to optimise synthetic routes for production of PP/EPDM copolymers for the purpose of compatibilisation of PP/EPDM blends. The MA-functionalisation was achieved using an internal mixer in the presence of low concentrations (less than 0.01 molar ratio) of a free radical initiator. Various methods were used to purify MA-functionalised PP and the grafting yield was determined using either FTIR or titrametry. The grafting yield of MA alone, which due to its low free-radical reactivity towards polymer macroradicals, was accompanied by severe degradation in the case of PP and crosslinking for EPDM. In the case of MA-functionalised PP/EPDM, both degradation and crosslinking occurred though not to a great extent. The use of tri-functional coagents e.g. trimethylopropane triacrylates (TRIS) with MA, led to high improvement of the grafting yield of MA on the polymers. This is almost certainly due to high free-radical activity of TRIS leading to copolymerisation of MA and TRIS which was followed by grafting of the copolymer onto the polymer backbone. In the case of PP, the use of coagent was also found to reduce the polymer degradation. PP/EPDM copolymers with optimum tensile properties were synthesised using a 'one-step' continues reactive processing procedure. This was achieved firstly by functionalisation of a mixture of PP (higher w/w ratio) and EPDM (low w/w ratio) with MA, in the presence of the coagent TRIS and a small concentration of a free radical initiator. This was then followed by an imidisation reaction with the interlinking agent hexamethylene diamine (HEMDA). Small amount of copolymers, up to 5 phr, which were interlinked with up to 15 phr of HEMDA, were sufficient to compatibilise PP/EPDM75/25 blends resulting in excellent tensile properties compared to binary PP/EPDM 75/25 blend. Improvement in blend's compatibility and phases-stabilisation (observed through tensile and SEM analysis) was shown in all cases with significant interphases adhesion improvement between PP and EPDM, and reduction in domain size across the fractured surface indicating efficient distribution of the compatibiliser.

Reactive processing methods for functionalisation of polymers and in-situ compatibilisation of poly(ethylene terephthalate)-based blends

One of the main objectives of this study was to functionalise various rubbers (i.e. ethylene propylene copolymer (EP), ethylene propylene diene terpolymer (EPDM), and natural rubber (NR)) using functional monomers, maleic anhydride (MA) and glycidyl methacrylate (GMA), via reactive processing routes. The functionalisation of the rubber was carried out via different reactive processing methods in an internal mixer. GMA was free-radically grafted onto EP and EPDM in the melt state in the absence and presence of a comonomer, trimethylolpropane triacrylate (TRlS). To optinuse the grafting conditions and the compositions, the effects of various paranleters on the grafting yields and the extent of side reactions were investigated. Precipitation method and Soxhlet extraction method was established to purifY the GMA modified rubbers and the grafting degree was determined by FTIR and titration. It was found that without TRlS the grafting degree of GMA increased with increasing peroxide concentration. However, grafting was low and the homopolymerisation of GMA and crosslinking of the polymers were identified as the main side reactions competing with the desired grafting reaction for EP and EPDM, respectively. The use of the tri-functional comonomer, TRlS, was shown to greatly enhance the GMA grafting and reduce the side reactions in terms of the higher GMA grafting degree, less alteration of the rheological properties of the polymer substrates and very little formation of polyGMA. The grafting mechanisms were investigated. MA was grafted onto NR using both thermal initiation and peroxide initiation. The results showed clearly that the reaction of MA with NR could be thermally initiated above 140°C in the absence of peroxide. At a preferable temperature of 200°C, the grafting degree was increased with increasing MA concentration. The grafting reaction could also be initiated with peroxide. It was found that 2,5-dimethyl-2,5-bis(ter-butylproxy) hexane (TIOI) was a suitable peroxide to initiate the reaction efficiently above I50°C. The second objective of the work was to utilize the functionalised rubbers in a second step to achieve an in-situ compatibilisation of blends based on poly(ethylene terephthalate) (PET), in particular, with GMA-grafted-EP and -EPDM and the reactive blending was carried out in an internal mixer. The effects of GMA grafting degree, viscosities of GMAgrafted- EP and -EPDM and the presence of polyGMA in the rubber samples on the compatibilisation of PET blends in terms of morphology, dynamical mechanical properties and tensile properties were investigated. It was found that the GMA modified rubbers were very efficient in compatibilising the PET blends and this was supported by the much finer morphology and the better tensile properties. The evidence obtained from the analysis of the PET blends strongly supports the existence of the copolymers through the interfacial reactions between the grafted epoxy group in the GMA modified rubber and the terminal groups of PET in the blends.

Compatibilisation of heterogeneous polymer blends by reactive processing

Functionalisation of polystyrene, PS, and ethylene-co-propylene-co-cyclopentadiene terpolymer, EPDM, with acrylic acid, AA, in a melt reactive processing procedure, in the presence of peroxide, trigonox 101, and coagents, Divinyl benzene, DVB (for PS), and trimethylolpropane triacrylate, TRIS (for EPDM), were successfully carried out. The level of grafting of the AA, as determined by infrared analysis, was significantly enhanced by the coagents. The grafting reaction of AA takes place simultaneously with homopolymerisation of the monomers, melt degradation and crosslinking reactions of the polymers. The extent of these competing reactions were inferred from measurements of melt flow index and insoluble gel content. Through a judicious use of both the peroxide and the coagent, particularly TRIS, unwanted side reactions were minimized. Five different processing methods were investigated for both functionalisation experiments; the direct addition of the pre-mixed polymer with peroxide and reactive modifiers was found to give optimum condition for grafting. The functionalised PS, F-PS, and EPDM, F-EPD, and maleinised polypropylene carrying a potential antioxidant, N-(4-anilinophenyl maleimide), F-PP were melt blended in binary mixtures of F-PS/F-EPD and F-PP/F-EPD in the presence (or absence) of organic diamines which act as an interlinking agent, e.g, Ethylene Diamine, EDA, and Hexamethylene Diamine, HEMDA. The presence of an interlinking agent, particularly HEMDA shows significant enhancement in the mechanical properties of the blend, suggesting that the copolymer formed has acted as compatibiliser to the otherwise incompatible polymer pairs. The functionalised and amidised blends, F and A-PSIEPDM (SPOI) and F and A-PPIEPDM (SPD2) were subsequently used as compatibiliser concentrates in the corresponding PSIEPDM and PPIEPDM blends containing various weight propotion of the homopolymers. The SPD1 caused general decreased in tensile strength, albeit increased in drop impact strength particularly in blend containing high PS content (80%). The SPD2 was particularly effective in enhancing impact strength in blends containing low weight ratio of PP (<70%). The SPD2 was also a good thermal antioxidant albeit less effective than commercial antioxidant. In all blends the evidence of compatibility was examined by scanning electron microscopy.

The chemical modification of polymer blends by reactive processing

The primary objective of this research was to examine the concepts of the chemical modification of polymer blends by reactive processing using interlinking agents (multi-functional, activated vinyl compounds; trimethylolpropane triacrylates {TRIS} and divinylbenzene {DVD}) to target in-situ interpolymer formation between immiscible polymers in PS/EPDM blends via peroxide-initiated free radical reactions during melt mixing. From a comprehensive survey of previous studies of compatibility enhancement in polystyrene blends, it was recognised that reactive processing offers opportunities for technological success that have not yet been fully realised; learning from this study is expected to assist in the development and application of this potential. In an experimental-scale operation for the simultaneous melt blending and reactive processing of both polymers, involving manual injection of precise reactive agent/free radical initiator mixtures directly into molten polymer within an internal mixer, torque changes were distinct, quantifiable and rationalised by ongoing physical and chemical effects. EPDM content of PS/EPDM blends was the prime determinant of torque increases on addition of TRIS, itself liable to self-polymerisation at high additions, with little indication of PS reaction in initial reactively processed blends with TRIS, though blend compatibility, from visual assessment of morphology by SEM, was nevertheless improved. Suitable operating windows were defined for the optimisation of reactive blending, for use once routes to encourage PS reaction could be identified. The effectiveness of PS modification by reactive processing with interlinking agents was increased by the selection of process conditions to target specific reaction routes, assessed by spectroscopy (FT-IR and NMR) and thermal analysis (DSC) coupled dichloromethane extraction and fractionation of PS. Initiator concentration was crucial in balancing desired PS modification and interlinking agent self-polymerisation, most particularly with TRIS. Pre-addition of initiator to PS was beneficial in the enhancement of TRIS binding to PS and minimisation of modifier polymerisation; believed to arise from direct formation of polystyryl radicals for addition to active unsaturation in TRIS. DVB was found to be a "compatible" modifier for PS, but its efficacy was not quantified. Application of routes for PS reaction in PS/EPDM blends was successful for in-situ formation of interpolymer (shown by sequential solvent extraction combined with FT-IR and DSC analysis); the predominant outcome depending on the degree of reaction of each component, with optimum "between-phase" interpolymer formed under conditions selected for equalisation of differing component reactivities and avoidance of competitive processes. This was achieved for combined addition of TRIS+DVB at optimum initiator concentrations with initiator pre-addition to PS. Improvements in blend compatibility (by tensiles, SEM and thermal analysis) were shown in all cases with significant interpolymer formation, though physical benefits were not; morphology and other reactive effects were also important factors. Interpolymer from specific "between-phase" reaction of blend components and interlinking agent was vital for the realisation of positive performance on compatibilisation by the chemical modification of polymer blends by reactive processing.