Polyetheramine modified polymer rubbers of ethylene-glycidylmethacrylate-vinyl acetate and epoxy resins comprising the same

Field of Invention The present invention relates to rubber polymers of ethylene-glycidylmethacrylate-vinyl acetate polymer. The ethylene-glycidylmethacrylate-vinyl acetate polymer comprises polyetheramine modified glycidyl methacrylate monomer units. The present invention also relates to a method for the manufacture thereof and kits comprising the same for epoxy resins. Background of Invention

Epoxy resins are thermoset compounds with a complicated cross-linked polymeric structure. Epoxy resins are formed by curing (reacting) a two part mixture of a first part providing an epoxy functionality and a second part providing a curing agent.

The curing agents are often referred to as curatives, hardeners or converters. The curing agents can be an anhydride (e.g. phthalic anhydride) or an amine (e.g. polyetheramine).

Depending on a complexity of the first part providing the epoxy functionality and the complexity of the second part providing the curing agent a wide range of characteristics of the epoxy resin results, such as; desirable physical and mechanical properties, thermal stability, chemical resistance and process ability. The characteristics of the epoxy resins make them desirable in a wide range of applications for example in coatings, adhesives, aeronautical and electronic components.

The aforementioned types of epoxy resins however suffer from numerous problems such as brittleness, low fracture resistance, poor impact strength and high notch sensitivity.

These problems limit a use of the epoxy resins in various applications where such problems need to be overcome.

The Handbook of Epoxy Blends, Chapter: 10, Springer International, H. Kargarzadeh et al, “Mechanical properties of Epoxy Rubber Blends” discloses that a method to overcome these problems, is via the incorporation of a dispersed rubber phase (as either core-shell rubber particles or miscible reactive rubber particles) when curing (reacting) the two part mixture of the first part providing an epoxy functionality and the second part providing the curing agent to form a rubber blended epoxy resin. However the resultant epoxy resin exhibits a two-phase microstructure of rubber particles dispersed in the epoxy resin l matrix. The two-phase microstructure often undergoes phase separation at an interface of the dispersed rubber phase and the epoxy resin bulk mass. The phase separation is due to a weak interaction between the dispersed rubber phase and the epoxy resin bulk mass, which undermines the desired properties of the epoxy resin. A type of miscible reactive rubber based on liquid acrylonitrile-butadiene copolymers with end-group functionality such as amino groups (ATBN) are known in the art. However these miscible reactive rubber based on liquid acrylonitrile-butadiene copolymers with end-group functionality such as amino groups (ATBN) are required in relatively high dosage (above 15 phr) due to the low molecular weight, which causes losses of strength, modulus and heat resistance of the final epoxy resin. Environmental ozone is known to adversely affect materials containing double bonds, leading to crack formation and loss of mechanical strength. Acrylonitrile-butadiene copolymers with end-group functionality such as amino groups (ATBN) comprise a high double-bond content leading the aforementioned deficiencies. Rubber polymers of ethylene-glycidylmethacrylate-vinyl acetate are known in the art as disclosed for example in EP 3015483.

There is a need to overcome the aforementioned problems of the prior art.

Summary of Invention

In a first aspect the present invention relates to an ethylene-glycidylmethacrylate-vinyl acetate polymer, the ethylene-glycidylmethacrylate-vinyl acetate polymer comprising polyetheramine modified glycidyl methacrylate monomer units.

In a further aspect the present invention relates to a method for the manufacture of the aforementioned ethylene-glycidylmethacrylate-vinyl acetate polymer, the method comprising, reacting an ethylene-glycidylmethacrylate-vinyl acetate polymer with a polyetheramine.

In a further aspect the present invention relates to a kit for the manufacture of an epoxy resin, the kit comprising the aforementioned ethylene-glycidylmethacrylate-vinyl acetate polymer, a curing agent and an agent providing an epoxy functionality.

The ethylene-glycidylmethacrylate-vinyl acetate polymer comprising polyetheramine modified glycidyl methacrylate monomer units, maintains reactivity towards curing agents and an agent providing an epoxy functionality. The ethylene-glycidylmethacrylate-vinyl acetate polymer comprising polyetheramine modified glycidyl methacrylate monomer units ensures internal bonding within the epoxy resin overcoming the problems associated with a two-phase microstructure of the prior art with significant improvement on impact strength. The ethylene-glycidylmethacrylate-vinyl acetate polymer comprising polyetheramine modified glycidyl methacrylate monomer units fulfils the desired impact toughening effect at relatively low dosages when used in an epoxy resin kit. A critical stress intensity factor (KIC) and critical strain energy release rate (GIC) of epoxy resins is greatly increased with a lower dosage (5 phr versus 15 phr) than required by the prior art.

Brief Description of Figures

Figure 1 shows how the amount of modifier affects the impact strength in the final epoxy resin. Figure 2 shows the impact fracture surfaces of samples as analysed by SEM.

Figure 3 shows how the amount of modifier affects the tensile strength in the final epoxy resin.

Figure 4 shows the TEM images of a) the epoxy resin alone and c) the epoxy resin according to the present invention. Detailed Description

For a complete understanding of the present invention and the advantages thereof, reference is made to the following detailed description.

It should be appreciated that the various aspects and embodiments of the detailed description as disclosed herein are illustrative of the specific ways to make and use the invention and do not limit the scope of invention when taken into consideration with the claims and the detailed description. It will also be appreciated that features from different aspects and embodiments of the invention may be combined with features from different aspects and embodiments of the invention.

In a first aspect the present invention relates to an ethylene-glycidylmethacrylate-vinyl acetate polymer, the ethylene-glycidylmethacrylate-vinyl acetate polymer comprising polyetheramine modified glycidyl methacrylate monomer units.

Ethylene-glycidylmethacrylate-vinyl acetate polymers are a rubber polymer known in the art. Ethylene-glycidylmethacrylate-vinyl acetate rubber polymers are manufactured from the monomers ethylene, vinyl acetate and glycidyl methacrylate as disclosed for example in EP 3015483, the teachings of which are incorporated herein by reference. An exemplary structure of the ethylene-glycidylmethacrylate-vinyl acetate polymer is shown below in Formula I. The exemplary structure doesn’t show the specific amounts of the monomers ethylene, vinylacetate and glycidyl methacrylate or the overall chain length.

Thus the exemplary structure of the ethylene-glycidylmethacrylate-vinyl acetate polymer comprising polyetheramine modified glycidyl methacrylate monomer units could be represented by Formula II. Formula II

Thus the ethylene-glycidylmethacrylate-vinyl acetate polymer according to the present invention is based on modifying at least some glycidyl methacrylate monomer units of the ethylene-glycidylmethacrylate-vinyl acetate polymers with polyetheramine. Polyetheramine

In the context of the present disclosure it is to be understood that modified means, reacted or grafted in which the polyetheramine forms a reaction product with the glycidyl methacrylate monomer units of the ethylene-glycidylmethacrylate-vinyl acetate polymer.

Since polyetheramine is a curing agent, the ethylene-glycidylmethacrylate-vinyl acetate polymer comprising polyetheramine modified glycidyl methacrylate monomer units has improved compatibility with a further curing agent and an agent providing an epoxy functionality when used in forming an epoxy resin. Although polyetheramine was used with approximately 2.5 propylene-glycol units, it may be possible to use other polyetheramines with a different number of propylene-glycol units. Polyetheramines have the advantage of lower volatility and low toxicity compared to diamino-alkanes.

The ethylene-glycidylmethacrylate-vinyl acetate polymer comprising polyetheramine modified glycidyl methacrylate monomer units has preferably the following composition. The monomer vinyl acetate units should be present in a range of 25 - 75 wt%, the range provides a presence of a large enough rubber amorphous phase and provides that a rubber amorphous phase has a glass transition temperature (Tg) below room temperature. The monomer glycidyl methacrylate should be present in a range of 1 - 25 wt%, which is then relevant in the polyetheramine modified glycidyl methacrylate monomer units.

A sum of the three monomers ethylene, vinyl acetate and glycidyl methacrylate could be 100%; however other monomer units may be present.

The ethylene-glycidylmethacrylate-vinyl acetate polymer comprising polyetheramine modified glycidyl methacrylate monomer unit has preferably the following molecular weight. The molecular weight should be at least 10,000 g/mol (Mn). The molecular weight may be above 40,000 g/mol (Mn) to avoid the drawbacks of liquid rubber modifiers of the prior art (loss of modulus strength). It is observed that when using liquid rubber modifiers of the prior art a necessary phase separation during curing of the epoxy resin depends on curing conditions and this results in uneven phase separation. When using the molecular weight according to the above, a phase separation sets in easier, resulting in more even and surprisingly smaller particle size distributions in the epoxy matrix. The preferred molecular weight above 40,000 g/mol furthermore facilitates easier handling in epoxy applications. The ethylene-glycidylmethacrylate-vinyl acetate polymer comprising polyetheramine modified glycidyl methacrylate monomer units is modified with a degree of modification (also referred to as grafting degree or GD) of the glycidyl methacrylate monomer units by polyetheramine of at least 0.5%. This degree of modification ensures a sufficient reactivity of the amine groups of the polyetheramine when forming an epoxy resin for interfacial bonding. The degree of modification can also be preferably 1% and more as this facilitates a higher reactivity with the epoxy resin matrix. It is to be appreciated that there is no upper limit for the degree of modification, except a possible complete modification with polyetheramine of all glycidyl methacrylate monomer units. Thus the degree of modification is important for the benefits brought about by the ethylene- glycidylmethacrylate-vinyl acetate polymer comprising polyetheramine modified glycidyl methacrylate monomer units as certain minimum degree of grafting is necessary.

A grafting efficiency (GE) is a mass ratio of grafted polyetheramine content to the initially provided polyetheramine, as further discussed below. It is understood that the GE can be increased by choosing the ethylene-glycidylmethacrylate-vinyl acetate polymer with a higher content of glycidyl methacrylate monomer units and more polyetheramine. The grafting efficiency should be at least 10%, preferably 20% and more to increase the benefits in the final epoxy compound.

In a further aspect the present invention relates to a method for a manufacture of ethylene-glycidylmethacrylate-vinyl acetate polymer comprising polyetheramine modified glycidyl methacrylate monomer units. The method comprising, reacting ethylene- glycidylmethacrylate-vinyl acetate polymers with a polyetheramine.

The polyetheramine thus reacts with the epoxy groups of the glycidyl methacrylate monomer units, thus modifying them in part with polyetheramine which is the curing agent and hence providing additional curing ability. It is preferable that the polyetheramine is according to the following formula: Although polyetheramine was used with approximately 2.5 propylene-glycol units, it may be possible to use other polyetheramines with a different number of propylene-glycol units. Polyetheramines have the advantage of lower volatility and low toxicity compared to diamino-alkanes. According to the method for the manufacture, the ethylene-glycidylmethacrylate-vinyl acetate polymer is mixed with polyetheramine to form a homogenous mixture.

Due to a polymeric and viscous nature of the starting materials and the products, a suitable mixer is used such as a melt mixer, a Z-blade mixer or an internal mixer. Such mixer provide sufficient mechanical mixing for the starting materials and the products and further allows a control of temperature by appropriate cooling or heating facilities. Such mixers are known in the art in the rubber industry. However, is also possible to carry out the reaction in solution if a solution based epoxy compound is intended to be manufactured.

It is preferable that the polyetheramine is used in a molar excess of up to 1 .5 in order to cap the glycidyl groups of the glycidyl methacrylate monomer units and to avoid crosslink reactions. The ethylene-glycidylmethacrylate-vinyl acetate polymer may be mixed with polyetheramine in an amount of 100/5, wt/wt, however this can depend on the amount of the glycidyl methacrylate monomer units in ethylene-glycidylmethacrylate-vinyl acetate polymer. A purpose of the first step is to homogenise the ethylene-glycidylmethacrylate-vinyl acetate polymer with polyetheramine without any reaction. The first step is carried out at a temperature in a range of 40 - 120 °C, and more preferably in a range of 60 - 80 °C. The first step is carried out at a mixing rate in a range of 30 - 70 rpm. The first step is carried out for a time in a range of 5 - 30 mins. It is to be appreciated that any of the temperatures, mixing rates and times can be combined to homogenise the ethylene- glycidylmethacrylate-vinyl acetate polymer with polyetheramine. Since achieving the homogenous mixture may depend on amounts of the ethylene-glycidylmethacrylate-vinyl acetate polymer and polyetheramine, a size of a mixing vessel for example may be determined accordingly by one skilled in the art. It is nevertheless appreciated that a higher temperature in the range noted above leads to a lower viscosity and thus a more rapid formation of the homogenous mixture.

The mixture is then subjected to a second step in which a higher temperature in a range of 100 - 140 °C and more preferably in a range of 110 - 130 °C to obtain a high reaction speed and simultaneously avoid gel formation. The second temperature is determined by carrying out the reactions at different temperatures and determining a gel content of the product such that essentially no gel is formed which can be determined by suitable test experiments beforehand. The formation of gel should be avoided and/or minimised in order to not to create difficulties for dissolution in an epoxy resin kit or the final epoxy resin. The mixing rates and the mixing times can be those as used in the first step.

The reaction mixture is then worked-up to remove unreacted polyetheramine and provide the final product, the ethylene-glycidylmethacrylate-vinyl acetate polymer comprising polyetheramine modified glycidyl methacrylate monomer units. The mixture is dissolved in a solvating solvent (e.g. chloroform) at room temperature to form a solution. A non- solvating solvent (e.g. ethanol) is then added in excess to precipitate out the ethylene- glycidylmethacrylate-vinyl acetate polymer comprising polyetheramine modified glycidyl methacrylate monomer units. The work-up is repeated three times.

The product, the ethylene-glycidylmethacrylate-vinyl acetate polymer comprising polyetheramine modified glycidyl methacrylate monomer units, is then dried to ensure removal of the solvating solvent and/or non-solvating solvent (the presence of which can be identified by ¹ H NMR). The drying can be conducted in any suitable means known in the art such as a drying oven and or under vacuum. A drying temperature can be in a range of 50 - 60 °C. The product, the ethylene-glycidylmethacrylate-vinyl acetate polymer comprising polyetheramine modified glycidyl methacrylate monomer units is identified by ¹ H NMR and UV spectroscopy.

The grafting efficiency (GE) and the grafting degree (GD) are calculated by ¹ H NMR data. Calculation of the GE and GD is as follows.

NMR peak area is proportional to a content of the corresponding components of the ethylene-glycidylmethacrylate-vinyl acetate polymer comprising polyetheramine modified glycidyl methacrylate monomer units. The content of the ethylene-glycidylmethacrylate- vinyl acetate polymer component remains constant after removing the unreacted polyetheramine, so a ratio of a peak area corresponding to unreacted polyetheramine to the peak area corresponding to ethylene-glycidylmethacrylate-vinyl acetate polymer comprising polyetheramine modified glycidyl methacrylate monomer units can reflect the content of grafted polyetheramine. The grafting efficiency (GE) is the mass ratio of grafted polyetheramine content to the initially provided polyetheramine. The grafting efficiency can be calculated by the following formula:

AT /A

GE = - - - - x 100%

A' A _a where A and A' are the resonance peak areas of the un-purified and purified blends respectively, b refers to a peak of the aliphatic portion of the polyetheramine between 3.00 and 3.75 ppm (-CH ₂ - and -CHCH ₃ -, reacted or unreacted) and a refers to a reference peak in the terpolymer such as the CH adjacent to the acetate ester groups. The grafting degree (GD, i.e., weight percentage of the grafted polyetheramine in the purified blends) can be calculated by the following equation:

GD= B ^A +A ^xG «G ^E E x 100% where B and A are the parts by weight of ethylene-glycidylmethacrylate-vinyl acetate polymers and polyetheramine in the blends, respectively. Thus for example GD and GE can be manipulated (and is within the ability of one skilled in the art based on the present disclosure) based on content of glycidyl methacrylate monomer units in the polymer, amounts of polyetheramine, longer reaction times or further optimised reaction temperatures which can contribute to higher GD enhancing the benefit of the inventive polymer. In a further aspect the present invention relates to a kit for the manufacture of an epoxy resin. The kit comprising the ethylene-glycidylmethacrylate-vinyl acetate polymer comprising polyetheramine modified glycidyl methacrylate monomer units, a curing agent and an agent providing an epoxy functionality. A ratio between the agent providing an epoxy functionality and the curing agent is determined by considering an epoxy equivalent of the curing agent.

In the kit, one equivalent of curing agent should be present with two equivalents of the agent providing an epoxy functionality.

The ethylene-glycidylmethacrylate-vinyl acetate polymer comprising polyetheramine modified glycidyl methacrylate monomer units is present in an amount of up to 15 wt% in the kit.

The curing agent can be an anhydride, such as those derived from phthalic anhydride, preferably the hydrogenated and alkylated types such as methyl-tetrahydrophthalic anhydride, hexahydro-methyl-phthalic anhydride and hexahydrophthalic anhydride. The curing agent can be a pyromellitic dianhydride, a trimellitic anhydride, a nadic anhydride, a nadic methyl anhydride, various alkylated succinic anhydrides and maleic anhydride. The curing agent can be derived from ethylenediamine-tetraacetic acid (EDTA) after conversion into its respective anhydrides. The agent providing the epoxy functionality can be multi-functional glycidyl ethers which can be obtained from reaction products with epichlorohydrin, such as glycidyl ethers from bisphenol A or bisphenol F. Depending on a ratio of epichlorohydrin and bisphenol A epoxy compound of various chain length and viscosity can be obtained. Glycidyl ethers of cresol and more generally various di-and trihydric phenols, of various polyols like glycerol, pentaerythritol, tetraphenol-ethane, trimethylol propane and trimethylol ethane, glycidyl- ethers of novolac resins. Cycloaliphatic glycidyl ether is preferred for superior UV resistance. The agent providing the epoxy functionality can be epoxy compounds which contain 3,4-epoxycyclohexyl-groups such as 3,4-epoxy cyclohexyl-methyl-3, 4-epoxy cyclohexane carboxylate. The agent providing the epoxy functionality can be provided by combining oligo-amino precursors with epichlorohydrin to glycidyl compounds which gives epoxy resins with high functionality. Anhydrides can also be converted into epoxy compounds such as hexahydrophthalic acid diglycidyl ester. The agent providing the epoxy functionality can also be based on linear oligomers with terminal epoxy groups such as liquid polybutadiene with epoxy end-groups, polyethers with terminal epoxy groups or simpler diglycidylethers of alkylene-diols. Glycidyl amines can provide reactivity from both the glycidyl group and the amino functionality. The agent providing the epoxy functionality can also be used in their function as reactive diluents for the purpose of lowering the viscosity for example. The agent providing the epoxy functionality is preferably a liquid at room temperature. The agent providing the epoxy functionality preferably has a molecular weight in a range of from 200 - 800 g/mol. This range is determined by the need to provide easy to handle liquid epoxy agent and to have a suitable high enough epoxy group content. The number of epoxy groups is determined by the desired crosslink density after curing and necessary flexibility.

The kit for the manufacture of the epoxy resin may contain at least one catalyst. The catalyst is used to speed-up the curing reaction when forming the epoxy resin. The catalysts can be quaternary ammonium salts, quaternary phosphonium salts, substituted imidazoles, transition metal salts, phosphine compounds, metal acetylacetonates and amino-compounds, such as dimethylaminomethyl-phenol. The catalyst can be at least one of the aforementioned or any combination thereof. A choice of the catalyst depends on a desired curing rate and the processing temperature. An amount of the at least one catalyst is in the range from 0.5 - 5-vol%. This range is preferable since more amounts low molecular weight materials in the final epoxy resin have a negative effect on the mechanical properties of the epoxy resin.

The kit for the manufacture of the epoxy resin may contain at least one filler. The at least one filler can be used to add certain functionality to resultant epoxy resins, such as abrasion resistance, overcoming shrink reduction, to give thermos-conductivity or electrical conductivity or to modify a viscosity of the uncured epoxy resin. The fillers can be silica particles such as fumed silica to provide thixotropic properties,; quartz, small glass beads may control shrink, mica may lower a friction coefficient; glass fibres, carbon fibres and nano-sized fibres help to further increase the modulus and/or also impact resistance. Without limiting the choice only a few are mentioned here such as aluminium hydroxide for flame retardency, aluminium oxide or boron-nitride for thermos-conductivity , Al flakes, silver powder and carbon black may provide antistatic effects or electrical conductivity, metal sulphates, talcum and clays may reduce costs. The dosage is limited in order not to affect the mechanical and adhesion performance of the final epoxy resin. As fillers can have a broad range of densities one can consider a volume fraction of the at least one filler in the kit and thus up to 20-vol%.

A use of ethylene-glycidylmethacrylate-vinyl acetate polymer comprising polyetheramine modified glycidyl methacrylate monomer units in epoxy resins increases an impact strength and a fracture toughness of the epoxy resin. Mechanical properties such as modulus, glass transition of the resin phase and a viscosity before cure are only minimally affected.

The following analytic tools were used.

¹ H Nuclear Magnetic Resonance (NMR) analysis was measured using a 400 MHz Bruker Advance 2B spectrometer using CDCI ₃ as solvent.

The molecular weight was measured by GPC in THF/CHCI ₃ following the procedure outlined in EP 3015483.

Visible Light Transmittance. Transparency was measured using an UV-visible spectrophotometer (TU-1901 , Beijing Purkinje General Instrument Co. Ltd.). Air was used as blank reference, and transmittance spectra were recorded in a wavelength range of 200 - 800 nm.

Rheology Analysis. Viscosity was measured on a rheometer (Discovery DHR-2, TA Instruments, USA) with a diameter of 25 mm aluminium parallel plates at the temperature of 25 °C. Frequency sweeps from 1 - 1000 Hz were performed at a strain of 1%. Differential Scanning Calorimetry (DSC). Thermal analysis was measured on a thermal analyser (Netzsch 204 F1 , Germany). About 5 mg of each sample was heated from 30 - 200 °C at 10°C/min under a N ₂ atmosphere. Dynamic Mechanical Analysis (DMA). Thermomechanical behaviour was measured on a DMA-Q800 (TA Instruments). The specimens (60 x 10 x 4 mm ³ ) were heated under a double cantilever mode from -30 - 180 °C at 3 °C/min. The amplitude and frequency were set as 15 pm and 1 Hz, respectively. Thermogravimetric Analysis (TGA). Thermal stability was measured using TGA (1100SF, Mettler-Toledo, Switzerland) from 50 - 600 °C at 10 °C /min under a N ₂ atmosphere.

Mechanical Properties. Tensile properties were measured on a tensile tester (lnstron5967, USA) at 5 mm/min, and the geometry of the parallel section of the dumbbell-shaped tensile bar is 60 x 10 x 4 mm ³ . Unnotched impact strength was measured using a pendulum impact tester (HIT-2492, China), sample dimension was 80 x 10 x 4 mm ³ . The measurements were performed at a temperature of 23 °C and at least five independent specimens were tested to obtain the average values for each sample.

Fracture Toughness. Critical stress intensity factor (KIC) and critical strain energy release rate (GIC) was measured using a tensile tester (lnstron5967, USA) under a three-point- bend (SEN-3PB) mode according to the ASTM D5045 standard. The geometry of the samples was 53 x 12 x 6 mm ³ . All samples were tapped using a razor blade to create sharp cracks with a 6 mm length. The measurements were carried out under a constant displacement rate of 1 mm/min. Scanning Electron Microscopy (SEM). Impact- fractured surfaces was measured using a SEM (S-4800, HITACHI, Japan) at an accelerating voltage of 3.0 kV. Before testing, the fractured surfaces of the samples were coated with a thin evaporated layer of gold.

Transmission Electron Microscopy (TEM). Phase morphologies of the samples were observed by using TEM (200 kV, JEOL-JEM-2100, Japan). The samples were ultra- microtomed at -120 °C to a section with a thickness of ~70 nm. The ImageJ software was used to analyse the average particle size. The area of each particle (A!) was calculated and then converted to an equivalent diameter (d!) of a sphere by cf, = 2 x (A;/TT) ^1/2 . The number average diameter (d _n ) of rubber particles is then obtained from d _n

= å d/N where N is the number of observed particles. Heat Deflection Temperature (HDT). The HDT was measured by using an HDT tester (V- 3216, China) under a bending stress of 1.80 MPa. The dimension of specimens is 80x10x4 mm3 and the heating rate is 1202 °C/hmin. The present invention is demonstrated by the following non-limiting examples.

Examples

Ethylene-glycidylmethacrylate-vinyl acetate polymer (60 wt% vinyl acetate and 3.1 wt% glycidyl methacrylate) was provided by Arlanxeo as Levapren NPG. Polyetheramine with approximately 2.5 propylene-glycol units was purchased from Huntsman Corp. under the tradename JEFFAMINE.

Tris (dimethylaminomethyl) phenol (DMP-30) used as catalyst was purchased from Aladdin Bio-Chem Technology Co., Ltd., China.

Methyltetrahydrophthalic (MTHPA) used as curing agent was purchased from Aladdin Bio- Chem Technology Co., Ltd., China.

Epoxy EPIKOTE 828 (EEW = 184-190 g/equiv), a glycidyl-ether of bisphenol was purchased from Guangzhou Picks Chemical Co., Ltd., China, here referred to EP monomer

Liquid acrylonitrile-butadiene copolymers with end amino groups (ATBN) were purchased from Shandong Baiqian Chemical Co., Ltd., China.

Ethanol and chloroform was provided from Sinopharm Chemical Reagent Co., Ltd., China.

All materials were used as provided.

1. Manufacture of ethylene-qlvcidylmethacrylate-vinyl acetate polymer comprising polyetheramine modified qlvcidyl methacrylate monomer units Ethylene-glycidylmethacrylate-vinyl acetate polymer and polyetheramine (100/5, wt/wt) was blended in a Haake mixer (HAAKE Polylab-OS) at 60°C at 50rpm for 10min to form a homogeneous mixture.

The temperature was then elevated to 120 °C at 50 rpm for a further 10 min.

The reaction mixture was then dissolved in chloroform and precipitated by the addition of ethanol to remove any unreacted polyetheramine. This was repeated three times.

The product was then dried in an oven for 20 mins at a temp of 55 °C.

The grafting degree of polyetheramine was determined by ¹ H-NMR to 2.43%. The grafting efficiency GE with polyetheramine was 49%. 2. Manufacture of epoxy resins

Examples 4, 5, 6 and 7: 50g epoxy and various amount of the polymer according to the present invention were charged into a 250 mL beaker. The mixture was stirred at 110 °C for 3 h. After that, 45g MTHPA curing agent (90 wt% of the EP monomer) and 0.75g DMP30 catalyst (1.5 wt% of the EP monomer) were added and stirred for 30 min. As EP monomer Epikote 828 (medium viscosity liquid epoxy resin produced from bisphenol A resin and epichlorohydrin) from Hexion was used. After degassing in a vacuum oven, the mixture was poured into the mould and then cured at 80 °C for 2 h and then 130 °C for 2 h. Specimens were then prepared to analyse the epoxy resin for tensile and impact properties.

Examples 2*, 11*, 12* and 13*: Manufacture was carried like in the above examples except that polymer according to the present invention was exchanged for ethylene- glycidylmethacrylate-vinyl acetate polymer.

Examples 14*, 15*, 16* and 17*: Manufacture was carried like in the above examples except that polymer according to the present invention was exchanged for liquid rubber modifier ATBN.

As a control example 1*, 50g epoxy and various amount of ethylene-glycidylmethacrylate- vinyl acetate polymer were charged into a 250 mL beaker. The mixture was stirred at 110 °C for 12 h. After that, 45g MTHPA curing agent (90 wt% of the EP monomer) and 0.75g DMP30 catalyst (1.5 wt% of the EP monomer) were added and stirred for 30 min. After degassing in a vacuum oven, the mixture was poured into the mould and then cured at 80 °C for 2 h and then 130 °C for 2 h. Specimens were then prepared to analyse the epoxy resin for tensile and impact properties.

The various examples and analysis are shown in the below tables. Wherein * indicates comparative examples and indicated not measured.

EG represents ethylene-glycidylmethacrylate-vinyl acetate polymer, EG-N represents polymer according to the present invention.

The examples clearly demonstrate that an impact strength and an elongation at break of the epoxy resins containing the polymer (modifier) according to the present invention are higher than that of the control. Figure 1 shows how the amount of modifier affects the impact strength in the final epoxy resin. The impact strength is significantly improved using the modifier of the present invention.

The impact fracture surfaces of samples was analysed by SEM and the results are shown in Figure 2, (a) neat epoxy resin, (b) epoxy resin 5% modifier of ethylene- glycidylmethacrylate-vinyl acetate polymer, (d) epoxy resin 5% modifier of the present invention. The fracture surface of the neat (a) is smooth without any plastic deformation, indicating a typical brittle fracture. For the (b) epoxy resins the fracture surface exhibits some faintly visible plastic deformation, corresponding to the limited improvement in impact strength. Regarding to the (d) epoxy resins, the fracture surface becomes significantly rough, reflecting the increase in energy dissipation during the fracture process. Thus, the impact strength is highly improved. In addition, the uniform dispersion of the modifier according to the present invention facilitates the plastic deformation throughout the matrix of the epoxy resin, resulting in considerable energy dissipation. As shown from the experiments a thermal stability of epoxy resins did not decrease substantially.

Figure 3 shows how the amount of modifier affects the tensile strength in the final epoxy resin. It is evident that tensile strength is maintained with up to 15% dosage of the modifier according to the present invention.

Figure 4 shows the TEM images of a) the epoxy resin alone and c) the epoxy resin according to the present invention. The TEM images clearly demonstrate that the use of the modifier according to the present invention leads to a smaller particle size of the rubbers in the epoxy resin. It is also noticeable that the dispersed rubber phase does not show smooth surfaces any more, instead an interphase is formed and the surface of the rubber particle is rough which indicates an increased interaction with the bulk epoxy resin whereby the bulk appears to maximise a contact interphase.

A critical stress intensity factor (KIC) and critical strain energy release rate (GIC) of epoxy resins with 5 phr polymer according to the present invention were 158% and 341% higher than that of pure epoxy resin, respectively.

The examples clearly demonstrate the effects of the present invention.

Having thus described the present invention and the advantages thereof, it should be appreciated that the various aspects and embodiments of the present invention as disclosed herein are merely illustrative of specific ways to make and use the invention. The various aspects and embodiments of the present invention do not limit the scope of the invention when taken into consideration with the appended claims and the foregoing detailed description.

What is desired to be protected by letters patent is set forth in the following claims.