GB2203743A - Composites of cellulose based fibers in polyethylene characterized by a silane bonding agent - Google Patents

Abstract

Composites comprise cellulose fibers dispersed in a matrix of polyethylene and bonded thereto with a sane bonding agent, optionally in the presence of an organic peroxide, a polyisocyanate or maleic anhydride, during subsequent extrusion and or molding.

Description

CELLULOSE BASED FIBERS AND BONDED COMPOSITES OF THE FIBERS IN POLYt:THYLENE CHARACTERIZED BY A SILANE BONDli7G AGEir2 This invention relates to composites of cellulose based fibers dispersed in a matrix of polyethylene and to treated cellulose fibers which have improved dispersability into polymer and improved adhesion thereto. More specifically, it relates to such reinforced thermoplastic composites which have good strength and molding characteristics and are derived from readily available cheap componentS.

The published literature includes a number of proposals which teach preparation of composites which consist essentially of thermosetting or thermoplastic resinous matrix materials having dispersed therein inorganic reinforcing fillers, such as mica platelets of flakes. Such materials are described. for example, in U.S. Patent number 3, 764,456 Woodhams issued October 9, 1973; and in U.S. Patent 4.442,243 which describes such micareinforced thermoplastic composites having improved durability, physical and aesthetic properties which are prepared by mixing the resin and the mica in the presence of propylene polymer wax. The mica may be pretreated to provide functional groups thereon for subsequent chemical reaction with the propylene polymer wax.

The use of inorganic fillers such as mica does however present certain technical difficulties. nica is a difficult material to process in making such composites. It is abrasive by nature, so that it tends to wear out processing machinery which it contacts.

The published literature contains certain references to the use of cellulosic fillers as additives for both thermoplastic and thermosett.ng resins. Such fillers may be derived from the finely ground products of wood pulp. the shells of peanuts or walnuts, corn cobs. rice hulls. vegetable fibers or certain bamboo-type reeds or grasses.

TWelgreat abundance and cheapness of such cellulosic materials in every part of the globe has made these cellulosic materials attractive sources for producing useful fillers on thermoset resins (such as the phenolics) for many years, their use in thermoplastics has been limited mainly as a result of difficulties in dispersing the cellulose particles in thermoplastic melts, poor adhesion (wettability) and in conse- quence inferior mechanical properties of the molded composites.

It has been shown that the dispersion of discontinuous cellulose based fibers into polymeric matrix can be greatly improved by pretreatment of the fibers with a plastic polymer and a lubricant. U.S. Pat. no 3,943,079 to Hamed described such pretreatment. Goettler in U.S. Pat. no 4,376,144 has shown that the composites made from cellulose fibers dispersed in a matrix of plasticized vinyl chloride polymer and bonded thereto with a cyclic trimer of toluene diisocyanate can be molded or extruded to produce useful articles.

Coran et al., U.S. Pat. 4,323,625 have shown that the composites can be produced from grafted olefin polymers and cellulose fibers. The polyolefins have been grafted with other polymers carrying methylol phenolic groups before being combined with cellulosic fibers and a bonding agent such as phenol aidehyde resin, a polyisocyanate or the like.

Lachowicz et al., U.S. Pat. 4,107,110 describe that CC cellulose fibers, coated with a graft copolymer comprising 1,2 - polybutadiene to which is grafted an acrylate such as butylmethacrylate could be used in reinforcing of PE and other plastic compositions.

Fujimora et al. Jap. Pat. Kokai 137,243,178 also o describe a cellulosic material which has been acetylated with gaseous acetic anhydride as a reinforcing agent for polyolefins.

Gaylord, U.S. Pat. 3,487,777 (1969) describes compatibilization of polyvinylchloride or polymethylmethacrylate with grafted cellulose.

Caylord, U.S. Pat. 3,645,939 also shows that polyethylene or polyvinylchloride or acrylic rubber can be compatibilized with cellulosic fibers in the presence of an ethylenically unsaturated carboxylic acid or anhydride under conditions which generate free radicals on said polymers, whereby said ethylenically unsaturated carboxylic acid or anhydride reacts with and couples with thermoplastic polymer and cellulose.

Hse, U.S. Pat. 4,209,433 have treated wood material with polyisocyanate before mixing with thermosetting phenol formaldehyde resin.

Lundl et al., U.S. Pat. 4,241,133 mixed elongated wood flakes with binder

(I.e. polyisocyanate) hot-pressed into the form of an elongated structural member as a beam, post, etc.

Wadeson. Brit. Pat. 1,585,074 describe a process to manufacture cellulosepolyurethane material by reaction of fibrous cellulosics with impregnated polyisocyanates in the presence of catalyst (zinc-octoate).

Nakavishl et al., Jap. Kokai 7697648 describe the use of cellulosics in PP.

Theiysohn et al., Ger.-Offen 2916657 presentv heat resistant PP molding composition. Suriyama et al., Jap. Kokai 7972247 introduce heat treated wood filler for thermoplastics. Also, Dereppe et al., Ger. Offen 2635957 as well as Kishikawa et al., Jap. Kokai 7345540 describe filler reinforced polypropygene.

SUMMARY OF THE INVENTION It has now been found that the cellulosic fibers can be well compatibilized with a matrix formed by polyethylene and the adhesion to cellulosic fibers to a matrix can be substantially improved by improving the interfacial adhesion by pretreatment of the filler with

silane coupling agents (in the presence of a free radical source.

the According to / present invention, composites are made of discontinuous cellulosic fibres pre-reacted with silane bonding agent like A-174 or A-172 or

A-1100 of Union Carbide Corporation, (in the presence or peroxide lxke ben=cyiperoxide or t-butyl peroxide or dicumylperoxide.

Composites containing from 1 to 50% of cellulosic fibers by weight. based on the total weight of composite are within the scope oi

The silane coupling agent A-174 (gamma-methacryloxy-propyltrimethoxy silane) or A-172 (vinyltri 2-methoxyethoxy silane) or A-1100 (gamma-aoinopro- pvltriethoxy silane) in the presence of a free-radical source is forming a trong adhesive bond vith wood fibers and possibly with matrix and thus provides a composite which has improved strength and stiffness.

The bonding agent has been found to be effective at relatively low ccne- trations - as low as 0.1 parts by weight on 100 parts of the polyethylene in the matrix. The free-radical source is used atlconcentration from 0.1 to 3 parts by weight based on 100 parts of the polyethylene.

The invention also includes treated discontinuous cellulosic fibers with aspect ratio varying from 2 to 5 (saw dust), from 12 to 50 (high yield and ultra high yield pulps) and from 50 to 100 for low yield chemical cellulosic pulps bonded chemically with 1 to 10 parts of polyethylene based on fiber weight in the presence of anhydride 0.5 to 10 parts, peroxide 0.1 to 5 parts and silane varying from 0.1 to 4 parts, all weight parts related to 100 weight parts of filler. The later material has also an excellent dispersability with polyethylene matrix.

DETAILED DESCRIPTION OF THE INVENTION The cellulosic materials used in the invention include cellulosic fibers derived from softwood or/and hardwood pulps, i.e. chemical or mechanical or C chemi-mechanyal or refiner or stone groundwood or thermo-mechanical or chemithermomechanical or explosion or low yield or high yield or ultra high yield pulp, nut shells, corn cobs, rice hulls, vegetable fibers, certain bamboo-type reeds, grasses. bagasse, cotton, rayon (regenerated cellulose), sawdust, wood flour, wood shavings and the like.

Preferred are cellulosic fibers derived from wood sawdust. wood flour, wood pulps, e.g. mechanical pulps or chemi-thermomechanical aspen puips. There are nany available types of wood pulp which may be classified according to where thev vere derived by chemical or mechanical or thermal treatment cr corbina- tion of treatments as well known in the pulp and paper industry. Waste pulp cr recycled pulp can also be used. The fibers have an aspect ratio (length divided by diameter) ranging from 2 to 5 for sawdust. wood flour as well as for mechanical pulps and 15 to 5G for chemi-mechanical and chemi-thermomecha- nical pulps and 50 to 150 for low yield chemical pulps (i.e. kraft, soda or bisulfite).

In some instances, it is desirable to use mixtures of fibers having widely different aspect ratios.

The polymer contained in the matrix is described as being "polyethylene" and includes both polyethylene polymer and copolymer of a major proportion of a polyethylene with / minor proportion of other copolymers like polypropylene.

The polymer "polyethylene includes linear low density polyethylene. low density polyethylene, medium density polyethylene as well as high density polyethylene, polyethylenes prepared at low and high pressures.

The cellulosic based fibers are described as "discontinuous" to distinguish from the well known incorporation of continuous cord reinforcement into rubber and plastic articles. The "matrix" is the material forming a continuous phase which surrounds the fibers. A "composite" is the combination of discontinuous fibers in a matrix wherein the contained fibers may be randomly oriented, or, to a greater or lesser degree, aligned in a particular direction.

The bonding agent A-174 has the formula:

gamma - methacryloxypropyltrimethoxy silane.

Silane A-172 has the following structure: CH2 = CH - Si (O C,H O CH,), vinyltri (2-methoxyethoxy) silane.

Silane Union Carbide A-1100 is gamBa-Aminopropyltricthoxysilane having the formula: H, NCJ H, Si(OCH2 Or3), The bonding agent is used in the composites of the invention in sufficient amount to achieve an adhesive bond between the polyethylene and the cellulcsic fiber. This amount can be as little as 0.1 part by weight of polyethylene up to 3 part by weight based on 100 parts by weight of polyethylene. The amount of bonding agent required can also be expected to vary with the amount of cellulosic fibers present. The free-radical source among others is benzoylperoxide or d-tert-butyl peroxide in proportions varying from 0.1 to 5 parts by weight related to 100 weight parts of filler.

The precise mecanism of the silane bonding is not known but it is highly probable that alkoxy groups hydrolyse to form silanols that react with filler and the other end of the silane coupling agent molecule, the functional organic groups (such as methacryloxy, vinyl or amino) react with the organic matrix resin as well as organic filler. To be effective in any given system, the silane coupling agent must be reactive with both the matrix resin and the filler to some degree.

The coupling may be applied to the filler in a separate pre-treatment step or it may be added directly to the resin during compounding. In general, improved processing is obtained with pre-treatment in the presence of peroxide.

Alternatively, the bonding agent may be combined vith the cellulosic base fiber in pre-treatment and pre-coating step. Following the idea of Gaylord, U.S. Pat. 3,645,939, the fibers can be grafted with a silane bonding agent so as to enhance their dispersability into a composite by admixture thereto of organic polymer which can be processed as thermoplastic in an amount suffi cient to reduce fiber-to-fiber affinity. Preferably, the organic polymer is polyethylene, although other compatible polymers having solubility parameters at midpoint of range vithin one unit of that of polyethylene can be used.The pre-coating step Is divided on pre-reacting of silane with cellulosic fibers in the presence of peroxide, pre-reacting of 3 to 10 weights parts of polyethylene based on 100 weight parts of fiber with 1 - 3 parts of unsaturated bicarboxylic acid (i.e. maleic anhydride) in the presence of 1 - 2 parts f peroxide, (i.e. bentoyl-peroxide, methyiethylketone peroxide. dicumyl peroxide, di-t-butyl peroxide, and 2.5-dimethyl - 2.5 - di(t-butyl peroxy hexane), followed by combining the products from the pre-reacting steps (cellulosic fibers silane treated plus carboylated polymer). Obtained pre-coated cellulosic fibers show excellent dispersability in polymeric matrix.

The ethylenically unsaturated carboxylic acid or anhydride coupling agent used in the practice of this invention is preferably dicarboxylic such as maleic acid or anhydride, fumaric acid, citraconic acid or itaconic acid.

Maleic anhydride is the preferred coupling agent. Monocarboxylic acids, such as acrylic acid and methacrylic acid, may also be used.

In addition to peroxides mentined above, a more detailed compilation of free radical initiators which may be used is set forth at pages 11-3 to ll-51 of "Polymer Handbook", Interscience Publishers (1966).

The combining of pre-reacted product can be accomplished in an internal mixer such as a Banbury mixer, Brabender mixer. CS1-max mixing extruder or on Roll mill. The temperature of mixing is a function of mixtures and equipment used. The proportions of the ingredients are dictated by the resulting composite properties. The amount of polymer used should be high enough to prevent fiber to fiber interaction, usually at least 3 parts of polyethylene by weight per 100 parts by weight of wood fibers. Usually, no more than 10 parts of polyethylene by weight per 100 parts of fibers by weight will be used. although higher polymer levels for fiber pre-coating can be employed if desired.

The fibers pre-treated with silane or the ones pre-coated with polymer are mixed with polymer matrix to form a composite usually in an internal mixer, extruder or an a roll mill. Additional ingredients, such as fillers. plasticiders. stabilizers, colorant, etc., can also be added at this point. The following specific examples illustrate the use of silane coupling as well as grafting agent for cellulosic fibers.

EXAMPLE I.

Materials Linear low density polyethylene (LLDPE). Navopol LLGR-0536-A, was supplied by Novacor Chemicals Ltd. Reported properties of LLDPE are as follows: Melt index: 5 g/10 min; density: 934 kg/m3.

The chemithermomechanical pulpsof aspen or birch used in this work wet prepared in a Sund Defibrator and have the properties described in Table 1.

The thermomechanical pulp (TMP) used in this work, prepared from a wood mixture of 75% spruce and 25% balsam fir, was supplied by Abitibi-Paper Co.

Coupling agents i) Vinyltri (2 - Methoxy Ethoxy) silane CH2 = CH - Si (O C2H4 O CH3(3 known as A-172 ii) Gamma - methacryloxy - propyltrimethoxy silane

known as A-174 iii) Gamma - amino propyl triethoxy silane 112N - C2H - Si (OCH2 - CH3)3 known as A-1100 were. supplied by Union Carbide Company, Montreal.

Bonding of fibers vith silanes A-172 and A-174 20 g of fibers, size Mesh 60, placed in 500 ml flask; 150 ml of carbon tetrachloride added; (0.8-2X) benzoylperoxide ######## based on oven dried pulp weight followed vith 1 to 4X of silane (by weight) A-172 or silane A-174. The vhole mixture was heated to reflux at 70 - 75 C while agitated by magnetic stirrer for 3 hours. After cooling, CCl4 was evaporated and mixture was dried at 55 C for 24 hours.

PreParation of comPosites Mixing of polymer and fiber was performed on roll mill, C.U. Brabender Laboratory Prep. Mill, no 065. Usuaily 15 to 20 grams of polymer were mixed with fibers at temperatures from 155 to 160 C, the resulting mixture collected and re-mixed 5-6 times, then allowed to cool down to room temperature and ground to mesh size 20.

The above prepared polymer-fiber mixture was molded into the shoulder type test specimens, (6-24 at the same time), in a mold, which was covered by metal plates on both sides.

The weight of material for one specimen was 0.9 g when molded at a temperature of 155.5'fC for 15 minutes at a pressure of 3.8 MPa. The starting temperature was 93.3'C and cooling time vas 15 minutes.

The samples were taken out from the mold after a 15 minute cooling period and then heat treated (annealed) at 105.0 in the oven for 1-2 hours. and finally allowed to stand at least 3 to 4 hours in the testing room which was kept at 23-C and 50% relative humidity.

Mechanical Tests Mechanical measurements were-made on an Instron tester (model 1131) at 23iC and 50X RH. The rate of elongation was 100X/min in all cases. All samples vere 3.175 mm in width and 6.4 cm in length (1.7 cm between grips). The thickness of samples was usually 0.158 cm.

Dimensions of all samples were measured with a micrometer. All experimental date reported is an average of at least four measurements. Mechanical measurements of samples which have been either pre-treated in boiling water for 3 hours or tempered at -35iC in instron Environmental Chamber Systems (model 3111), were made on an Instron tester (model 4201). Samples, pre treated in boiling water. were tested at 23'C and 50% RH. Mechanical properties, reported for this work, are those measured at yield point. The secant modulus was evaluated from origin to yield point. The properties. measured using Instron 4201, were automatically calculated by HPE6B using the Instron 2 412 005 General Tensile Test Program. The chordal modulus vas measured from I to 5% strain.Average coefficients of variation for mechanical properties were as follows: stress: 3.3X; strain: 4.9X; energy: 8.3X; modulus: 2.3x.

Results in Table 2 demonstrate that CTMP aspen fibers, bonded either with silane A-174 or A-172 were very effective in increasing the stength of resulting composites.

EXAMPLE II The composites were made and evaluated as in Example I but the fibers used were not bonded with silane. Tensile data are presented in Table 3. The addition of fiber causes a sharp increase of modulus, the highest for CTMP aspen fibers going from 43.5 MPa to 467 MPa. There is also increase in stress at least at 30% of fiber addition which is again the highest for aspen fibers.

Contrary the results with silane bonded fibers presented in Example l, there is sharp drop in energy as well as elongation comparing to LLDPE values.

EXAMPLE III The composites vere made and evaluated as in Example 1 but the silane treatment step vas carried out without the presence of benzoylperoxide as follows: Coupling agent treatment The wood fibers were treated using silane coupling agents In dilute ethanol solution as follows: 0.8 g silane A-172 or A-174 vas dissolved in 15 ml of ethanol (90X) and was added by drops for 5 minutes to 20 g of aspen pulp (mesh 60), while stirring. After this addition. stirring continued for 10 minutes.

The mixture was left at 105'C in the oven to dry for 2 hours before mixing with LLDP.

Tensile data are presented in Table 4. There is improvement in both stress as well as modulus when compared to polyethylene values. On the other hand, the absolute values are inferior to that found in Table 2 where fibers were silane treated in the presence of peroxide.

EXAMPLE IV The composites were made and evaluated as in Example I but the silane treatment step was substituted by fiber impregnation with the solution of polyethylene.

Impregnation Impregnation implies polymer deposition on fibers from polymer solution leading to physical bondage. The impregnation procedure used was as follows: 5 g of LLDPE were added to 200 ml of p-xylene and reflux with stirring (at iOO'C). 25 g of untreated aspen (CTMP) 60 mesh size were added to the solution and stirred under reflux for 2 hours. The mixture was left overnight in a mechanical shaker at 20-C. The impregnated pulp was filtered and dried for 12 hours at 105*C, then for 24 hours at 55 C, and ground to 60 mesh size before being mixed with LLDPE. The polymer loading was 20X.

The tensile properties of composites filled with impregnated aspen or birch fibers are presented in Table 5. There is improvement in stress and modulus comparing to polymer matrix but deterioration in absorbed energy as well as strain values. On the other hand, these composites are considerably weaker vhere compared to ones presented in Example 1, Table 2.

EXAMPLE V This time. the composites were made and evaluated as in Example I but the fibers vere pre-coated with polymer before being mixed with polymer matrix.

The pre-coating procedures were divided in the following steps: a) 20 g of fibers, size mesh 60, placed in 500 ml flask; + 150 ml of carbon tetrachloride; + 2% of benzoyl peroxide (0.4 g.) followed with 1 to 4% of

silane A-1100. The whole mixture 1heated to reflux at 70 to 75'C while agitated by magnetic stirrer for 3 hours. After cooling, CCI, evaporated and mixture was dried at 55'C for 24 hours.

b) 2 g LLDPE placed in a round bottom flask and 100 ml of p-xylene was added + 0.1 gm of benzoyl peroxide (5% on LLDPE) + 0.2 g of maleic anhydride (10X on LLDPE).

The whole mixture was tested under reflux while being agitated by the magnetic stirrer for 3 hours.

c) The whole content ( a + b) was put under reflux at 80-55'C, stirred for 2

hours. The contentlleft to cool down, at room temperature,

poured in a centered glass funnel to fiiter, washed with distilled water, then dried at 105'C for 12 hours and at 55'C for 24 hours, then

again to the desired mesh size. Folloved by mixing with LLDPE in percentages 10. 20. 30 and 40X on the roll mill as described in Example I.

The tensile results for pre-coated samples are presented in Table 6.

It is evident that pre-coating of cellulosic fibers leads to excellent adhesion between fibre and matrix and to excellent resulting properties of composition.

EXAMPLE VI The composites were made and evaluated as in Example VI but the molding temperature varied from 154.4iC to 171.1*C. The effect of molding temperature on molding properties is presented.ln Table 7. The best results are obtained at 165.5 C.

EXAMPLE VII The composites were made and evaluated as in Example VI but molding time or pressure were varied from 5 to 20 minutes and from 2.2 to 4.34 MPa respectively. The resulting tensile properties in Table 8 demonstrate the effect of molding parameters on resulting composite properties.

EXAMPLE VIII The composites were made and evaluated as in Example VI but the size of cellulosic fibers was determined by mesh size used and varied from 0.09 to 1.107 milimeters and fiber aspect ratio varied from 4.7 to 46. The effect of fibre size on resulting composite properties is presented in Table 9.

EXAMPLE IX The composites were made and evaluated as in Example VI. In addition, the folloving substrates were used as polyethylene filler: M.ca-2OD-NP-Su=orite (200 mesh, silane treated) and supplied by Marietta Co., Montreal. Glass fibers 731 BA 1/32 (0.8 mm, silane treated) and supplied by Fiber Glass of Canada via Mia Chemical, Montreal.

Composites of mica or glass fiber were made using the same procedure as used for cellulosic fiber with the exception of silane treatment since both of

them have been silane treated by manufacture.

The tensile results are presented in Table 10. It is obvious that the cellulosic filled composites compare well to either mica or glass fiber composites.

EXAMPLE X The composites were made and evaluated as in Example Vl with the exception that the mechanical properties were evaluated after composite exposure to 3 hours boiling in water tensile properties are presented in Table lOb: It can be seen that the strength of grafted aspen fiber composites remained virtually unaffected by boiling and the cellulosic filled composites compared well with that of mica or glass filler.

In addition, cellulosic composites remained dimentionally as stable as mica or glass fiber composites after 35 days submersion in water at room temperature. Uater uptake after a 35 days water treatment varied from 1.3 to 3.9 percent for 20 to 40 percent fiber content respectively.

EXAMPLE XI The composites were made and evaluated as in Example I but the polyethylene uselwas LLDPE Novapol GF-0118-A and the temperature of mixing on the rcli mill was 180 C.

Tensile properties are presented in Table 11 as a function of A-172 concentration varying from 0.5 to 2X in comparison with polyethylene. The optimum improvement of both stress and modulus was achieved at 0.5% of A-172 used.

EXAMPLE Xll The composites were made and evaluated as in Example 11. Tensile properties are presented in Table 12 for A-174 used either with benzoyl-peroxide or di-cumylperoxide.

EXAMPLE XIII The composites were made and evaluated as in Example II but the fibers were used without silane pre-treatment. In addition, CTMP aspen composite properties were compared to that of aspen sawdust (M60) or cotton cellulose (M60).

The tensile properties are presented in Table 13. It is obvious that without silane treatment there is a IDSS in strength expressed as stress when compared to virgin polyethylene.

EXAMPLE XIV The composites were prepared and evaluated as described in Example I but silane A-1100 was used. In Table 14 the tensile properties of composites prepared with A-1100 are compared to that with A-174. It is shown that both a silanes are having / beneficial effect on resulting composite properties.

EXAMPLE XV The composites vere prepared and evaluated as described in Example I but medium density polyethylene KDPE-ClL 560B was used as a polymer matrix. The tensile properties of virgin polyethylene as well as the composite are compared in Table 15. An excellent adhesion between A-172 silane treated fibers and polymer matrix has been demonstrated by the increase of stress values for composites going from 9.5 MPa to 16 MPa at 30 weight percent of CTMP aspen wood fibers addition. In case of modulus, the values increase from 150 MPa of virgin PE to 510 MPa in case of 40X of fiber addition.

EXAMPLE XVI The composites were prepared and evaluated as described in Example I but the polymer matrix used was high density polyethylene HDPE GRSN-8907 and fibers were mixed with polyethylene matrix in CSI-max-extruder, model CS-094 at mixing temperature of 145 C.

Tensile properties are presented in Table 16. The reinforcing properties of CTMP aspen fibers, treated with 1X of silane A-172 are clearly demonstrated by increased stress (33.3 MPa versus 24.7 MPa for virgin HDPE) as well as by increased modulus (1647 MPa at 40 weight percent of CTMP aspen fibers present versus 966 MPa for virgin HDPE).

EXAMPLE XVII The composites were prepared. and evaluated as in Example XVI but in addition to silane treatment of fibers. three weight percent of PnPFIC based on HDpE, were premixed at room temperature to HDPE before the fibers were mixed in CSI-max-extruder. PMPFIC is a linear polymethylene polyphenylisocya

nate of the formula: AJc-O A'CO I'CO co 9 Do OH%77 The effect of bonding isocyanate agent in addition to 1x of silane A-172 treatment is presented in Table 16. It is obvious that the added bonding leaA to further properties improvement when comparing to silane treatment alone.

This improvement was mainly in energy (20.1 compared to 14.6 KJ x 10- of virgin HDPE), in stress (36.9 HPa compared to 24.7 MPa for HDPE) and in modulus (1556 MPa compared to 966 MPa of virgin HDPE).

Although the foregoing invention has been described in some detail by the vay of examples for purposes of clarity of understanding, it vill be obvious that certain changes and modifications may be practised within the scope of the appended claims.

TABLE 1 PROPERTIES OF BIRCH AND ASPEN PULP

PROPERTIES BIRCH ASPEN Drainage index (CSF), ml 117 119 Brightness, Elrepho (%) 55.7 60.9 Opacity, (%) 94.1 91.4 Braking length, km 4.22 4.46 Elongation (%) 1.79 1.79 Tear index, mN.m/g 6.08 7.20 Burst, index, kPa.m/g 1.88 2.59 Yield (%) 90.0 92.0 Kappa index No 128.0 121.7 Lignin % 18.8 17.9 TABLE 2 COMPOSITES OF SILANE TREATED ASPEN PULPS

Energy Strain Stress Moduls EXPERIMENT (kj/m) (cm/cm) (MPA) (MPA) GRAFTED ASPEN PULPS 10% 20% 30% 40% 10% 20% 30% 40% 10% 20% 30% 40% 10% 20% 30% 40% SILANE CONCENTRATION and 2% of BENZOYL PEROXIDE A-174 - 1% 38.2 50.0 40.3 36.4 0.42 0.31 0.26 0.22 18.7 23.0 24.5 25.4 44.5 74.2 94.2 115.5 A-174 - 2% 41.2 60.1 52.2 40.4 0.41 0.29 0.24 0.21 20.5 23.6 26.4 28.6 50.6 81.4 110 136.2 A-174 - 3% 44.8 63.1 54.3 44.6 0.38 0.30 0.22 0.20 21.0 23.0 26.8 29.0 55.3 76.7 116.5 145.0 A-174 - 4% 51.8 69.1 57.4 54.5 0.35 0.31 0.27 0.193 20.8 24.2 28.1 29.9 59.4 78.1 104.1 154.1 A-172 - 4% 40.4 49.7 49.0 41.3 0.32 0.30 0.27 0.23 19.1 20.3 23.6 24.9 59.5 66.5 87.4 109.2 LLDPE # 20.4 # # 0.346 # # 14.8 # # 43.5 # TABLE 3 COMPOSITES OF UNTREATED @OOD PULPS

Energy Elongation Stress Modulus Experiment (KJ) x105 (%) (MPA) (MPA) Fibers. (wt %) 10 20 30 40 10 20 30 40 10 20 30 40 10 20 30 40 Aspen (CTMP) 1.6 15.4 8.4 8.3 14 10 7 5.8 12.6 15.2 18.4 27.1 90 152 262 467 (Mesh 60) Birch (CTMP) 9.6 10.9 5.0 2.7 16 10 9 6.7 22.5 22.6 18.8 17.1 148.5 226 208.8 255.2 TMP 1.4 6.2 4.3 1.8 10.4 10.3 10 6.7 19.3 18.1 17.4 13.1 189.5 175.7 174 195.5 LLDPE 20.4 34.6 14.8 43.5 TABLE 4 COMPOSITES OF SILANE TREATED ASPEN PULPS

ASPEN Energy Elongation Stress Modulus (KJ)x105 (%) (MPa) (MPa) Mesh 60 (wt %) 10 20 30 40 10 20 30 40 10 20 30 40 10 20 30 40 4% Silane A-172 12.3 13.3 11.8 9.64 24 21 19.4 12 15.6 17.7 18.4 19.7 65.0 84.3 95 164.2 4% Silane A-174 13.8 15.2 12.7 10.4 26 24.5 21 20 17.8 19.8 20.3 24.7 68.5 94.2 96.7 123.5 LLDPE 20.4 34.6 14.8 43.5 TABLE 5 COMPOSITES OF POLYMER IMPREGNATED PULPS

LLPDE Energy Elongation Stress Modulus IMPREGNATED (KJ)x105 ( % ) (MPa) (MPa) PULPS (wt %) 10 20 30 40 10 20 30 40 10 20 30 40 10 20 30 40 Aspen 16.9 13.9 12 11.1 19.6 16 15 15 34.0 22.2 18.4 16.1 122.4 138.8 122.7 107.3 (Mesh 60) Birch 15.7 13.3 11.2 10.0 19 14 13 11 23.7 21.4 22.8 12.4 112.6 152.8 175.4 117.7 (Mesh 60) LLDPE 20.4 34.6 14.8 43.5 TABLE 6 COMPOSITES OF GRAFTED ASPEN FIBERS

EXPERIMENTALY Energy Elongation Stress Modulus SILANE A-1100 (KJ) x105 (%) (MPa) (MPa) CONCENTRATION 10 20 30 40 10 20 30 40 10 20 30 40 10 20 30 40 1% 19.5 22.1 26.7 27.7 41.3 40.3 38.6 32.6 17.4 19.3 20.8 21.4 42.1 47.8 53.8 65.7 2% 22.1 27.4 31.7 34.3 40.0 38.9 35.8 31.5 18.7 21.4 22.2 22.7 46.8 54.9 62.0 72.2 4% 31.0 40.9 41.5 42.4 40.1 39.2 34.2 30.6 20.6 23.2 26.8 34.9 51.3 59.1 78.4 114.1 LLDPE 20.4 34.6 14.8 43.5 TABLE 7 COMPOSITES OF GRAFTED ASPEN PULP Effect of Press Temperature

Experimentally Grafted Aspen Energy Elongation Stress Modulus Pulp (KJ) x105 (%) (MPa) (MPa) (wt %) 10 20 30 40 10 20 30 40 10 20 30 40 10 20 30 40 (Mesh 60) 171.1 C 29.6 37.3 38.2 38.5 33.5 36.5 28.7 27.6 20.25 22.4 27.6 30.27 60.19 61.32 58.7 109.5 165.5 C 31.0 40.9 41.5 42.4 40.1 39.2 34.2 30.6 20.55 23.16 26.78 34.82 51.29 59.06 78.39 114.1 154.4 C 28.8 34.9 37.2 38.0 32.1 30.4 29.6 28.5 19.7 22.5 25.6 27.4 61.3 74.1 86.4 96.3 1% of A-1100 TABLE 8 COMPOSITES OF GRAFTED ASPEN PULP Effect of Time and Pressure

Experimentally Energy Elongation Stress Modulus Grafted Aspen Pulp (KJ)x105 ( % ) (MPa) (MPa) (wt %) 10 20 30 40 10 20 30 40 10 20 30 40 10 20 30 40 (Mesh 60) B) Effect of time 5 minutes 26.5 34.6 35.8 32.7 34 32 28 24 19.6 20.0 25.1 25.4 57.6 62.5 89.6 105.8 15 minutes 30.80 39.7 40.2 41.5 40 38 32 20 20.4 23.0 26.4 29.9 51.0 60.5 82.1 99.6 20 minutes 27.6 30.6 35.20 27.7 39 31 31 29 18.6 20.4 26.2 28.4 47.7 65.8 84.5 101.9 10 minutes 31.0 40.9 41.5 42.4 40 39 34 30 20.6 23.1 26.8 34.9 51.6 59.2 78.4 114.1 C) Effect of pressure (Arbitrary Units) 20 arbitrary units 26.5 35.3 35.8 37.1 36 30 29 25 18.5 20.4 26.2 29.9 51.4 68.0 90.3 119.6 35 arbitrary units -- -- 41.5 -- -- -- 34.2 -- -- -- 26.8 -- -- -- 78.4 -40 arbitrary units -- -- 41.4 -- -- -- 33.1 -- -- -- 26.8 -- -- -- 78.4 -30 arbitrary units 31.0 40.9 41.5 42.4 40 39 34 30 20.6 23.2 26.8 34.9 51.3 59.7 78.4 114.1 PRESSURE PRESSURE (Arbitrary Units) (MPa) 4% of A-1100 20 2.2 25 2.7 30 3.3 35 3.0 40 4.34 TABLE 9 COMPOSITES OF GRAFTED ASPEN PULP Effect of the Mesh Size

Mesh Energy Elongation Stress Modulus Grafted Aspen Pulp (KJ)x105 (%) (MPa) (MPa) (wt %) 10 20 30 40 10 20 30 40 10 20 30 40 10 20 30 40 #1-40 24.6 30.8 35.9 32.5 29.2 27.4 27.8 24.4 19.45 24.03 26.46 31.59 66.66 87.58 95.08 129.74 #;2-60 Mix.* 31.0 40.9 41.5 42.4 40.1 39.2 34.2 31 20.6 23.2 26.7 34.9 51.3 59.1 78.4 114.1 #3-20 Pure 25.5 32.1 31.0 31.1 29.2 27.5 26.0 24.9 24.1 26.85 29.77 30.00 82.5 92.6 114.5 120.50 #4-60 Pure 24.1 31.7 31.6 30.4 32 29.0 23.6 22.3 26.8 28.33 30.42 33.94 83.8 97.6 128.9 152.19 #;5-80 Pure 26.3 32.7 34.3 33.8 33.2 30.1 28.9 25.4 20.2 22.6 28.6 29.27 60.8 75.1 99.0 115.2 LLDPE 37.1 34.6 14.8 43.5 *#Mesh 60, Mix# is defined MESH AVERAGE FIBER as the one containing the Length (1) Diameter (d) $Aspect (1/d) following fiber sizes: mm mm 60.5% of Mesh 60; 20.2% of Mesh 80; 20 1.107 0.024 46 15.5% of Mesh 100 and 40 0.46 0.027 17.7 3.5% of Mesh 200. **60 0.30 0.022 13.9 80 0.22 0.021 10.1 100 0.18 0.020 9.1 200 0.09 0.019 4.7 ** For #Mesh 60 Mix# the average aspect ratio is about 11.9.

4% of A-1100 TABLE 10 COMPOSITES OF GRAFTED ASPEN PULP OR MICA OR GLASS FIBER

Experiment Energy Elongation Stress Modulus Filler (KJ)x105 (%) (MPa) (MPa) (wt %) 10 20 30 40 10 20 30 40 10 20 30 40 10 20 30 40 *Grafted Aspen pulp #Mesh (60) Mix# 31.0 40.9 41.5 42.4 40.1 39.2 34.2 30.6 20.6 23.2 26.8 34.9 51.3 59.1 78.4 114.1 MICA (Suzorite-200 NP) 12.0 22.2 9.56.7 24 20 12 09 18.4 20.1 19.7 22.0 75.0 100.5 159.3 238.7 GLASS FIBER (0.8 mm) 13.9 17.1 21.2 20.9 31 29 26 19 16.9 15.2 14.2 12.2 54.0 52.8 53.7 65.1 *10% of polyethylene addition.

4% of A-1100 TABLE 10b. COMPOSITES OF GRAFTED ASPEN PULP OR MICA OR GLASS FIBER EFFECT OF BOILING WATER PRETREATMENT*

EXPERIMENT ENERGY ELONGATION STRESS MODULUS FILLER (wt %) (KJ x 105) (%) (MPa) (MPa) 10 20 30 40 10 20 30 40 10 20 30 40 10 20 30 40 Grafted Aspen Pulp 40.1 41.7 45.0 23.5 21.2 19.1 22.9 25.5 30.5 282 341 429 "Mesh 60 Mix" Mica (Suzorite10.8 - - 9.5 - - 16.8 - - 232 - 200-NP) Glass fiber (0.8 mm) 18.5 - - 18.8 - - 13.6 - - 148 - LLDPE 27 23.1 16.1 183 * LLDPE and grafted aspen fibers (mica or glass fiber) composites, 3 hours boiling water pretreatment, followed 2 hours conditioning at 23 C and 50% RH before properties' evaluation.

LLDPE also treated as above.

TABLE 11 COMPOSITE PROPERTIES OF GRAFTED PULPS AT YIELD POINT

PROPERTIES TYPE OF FIBERS A-172 .5% A-172 1% A-172 2% PE 10% 20% 30% 40% 50% 10% 20% 30% 40% 50% 10% 20% 30% 40% 50% (GF-0118-A) STRESS 10.3 12.5 11.8 16.6 17.6 25 13 13.6 16 21 23 12.5 13.6 15 16 19 (MPa) STRAIN 18 25 14 4.4 4.3 4.3 27 13 7 5 5 19 10 4.5 4.3 4.2 (%) ENERGY 0.15 .243 .059 .032 .037 .046 .328 .064 .047 .051 .041 .191 .106 .032 .05 .023 (J) MODULUS 130 194 278 309 442 630 187 200 247 348 601 181 235 335 344 525 (MPa) TABLE 12 COMPOSITE PROPERTIES OF GRAFTED PULPS AT YIELD POINT

PROPERTIES TYPE OF FILLER BENZ. PER. A-174 .5% DI-CUMYL PER. A-174 1% M PE (GF-0118-A) 10% 20% 30% 40% 50% 10% 20% 30% 40% 50% 10% 20% 30% 40% 50% 10.3 STRESS 12.4 16 16.2 18.5 25 10.8 11 12 15.6 19 (MPa) 18 STRAIN 19 10 5 4.2 4.3 11.6 10 8 6 4 (%) 0.15 ENERGY .17 .08 .03 .016 .017 .09 .06 .025 .025 .09 (J) 130 MODULUS 188 266 481 465 559 180 202 244 327 579 (MPa) TABLE 13 COMPOSITE PROPERTIES OF NON-TREATED FIBERS AT YIELD POINT

PROPERTIES TYPE OF FIBERS ASPEN SAW DUST (MGO) CELLULOSE (cotton) CTMP (aspen) T = 165 C CTMP (aspen) T = 180 C PE (GF-0118-A) 10% 20% 30% 40% 50% 10% 20% 30% 40% 50% 10% 20% 30% 40% 50% 10% 20% 30% 40% 50% STRESS 10.3 9.03 8.47 7.87 8.18 -- 9.90 9.70 9.93 10.4 -- 8.73 7.52 6.93 -- -- 9.99 9.37 7.31 -- - (MPa) STRAIN 18 12.0 10.3 6.26 3.2 -- 11.4 8.44 3.9 2.51 -- 15.8 11.8 7.82 -- -- 12.0 8.6 1.9 -- - (%) ENERGY 18 .084 .069 .043 .024 -- .088 .067 .031 .023 -- .106 .071 .048 -- -- .095 .064 .014 -- - (J) 30 MODULUS 162 179 190 357 -- 172 218 351 426 -- 129 139 143 159 -- 176 199 403 -- - (MPa) CTMP ... chemithermomechanical pulp TABLE 14 COMPOSITES OF TREATED ASPEN PULPS LLDPE GR 0534-A

AT YIELD POINT AT BREAK EXPERIMENT FILLED ENERGY STRAIN STRESS MODULUS ENERGY STRAIN STRESS MODULUS (%)* (Jx102) (%) (MPa) (MPa) (Jx102) (%) (MPa) (MPa) LLDPE GR 0534-A 0 20 15 15 100 79 645 7.9 81 CTMP Aspen + 2% A-174 30 25 10.5 23.9 491 (1%)** 31.7 13 22 148 (10%)* TMP Aspen + 3% A-1100 30 37 14.7 25.1 205 (1%) 52.8 20.6 19.7 154 (10%) * CTMP Aspen; Mesh 60-Mix ** Value of strain at which modulus taken TABLE 15

ENERGY ELONGATION STRESS MODULUS COMPOSITE FIBER % (J x 105) (%) (MPa) (MPa) 10 20 30 40 10 20 30 40 10 20 30 40 10 20 30 40 MDPE-CIL 560B 16 9.5 150 MDPE + CTMP aspen 15 14.9 7 3 12.8 15 16 12.5 252 335 460 510 + 1% A-172 TABLE 16

COMPOSITE LOAD ENERGY MODULUS STRESS ELONGATION (N) (KJ x 105) (MPa) (MPa) (%) FIBER (%) 10 20 30 40 10 20 30 40 10 20 30 40 10 20 30 40 10 20 30 40 MDPE GRSN-B907 113 14.6 966 24.7 9.8 MDPE + CTMP aspen 112 122 145 - 12.4 11.7 13.3 - 1062 1350 1647 - 26.0 28.3 33.3 - 6.0 7.3 7.2 + 1% A-172 MDPE + CTMP aspen - - 166 - - - 20.1 - - - 1556 - - - 36.9 - - - 8.9 + 1% A-172 + 3% PMPPIC

Claims (28)

1. CLAIMS 1. A composite containing discontinuous cellulose fibers dispersed in a matrix comprising polyethylene and bonded to the matrix by a bonding agent containing an alkoxy silane having a further reactive group therein.
2. 2. A composite according to claim 1 wherein the silane is a trialkoxy silane.
3. 3. A composite according to claim 1 or claim 2 wherein the said reactive group of the silane is a terminal double bond or an amino group.
4. 4. A composite according to any preceding claim wherein the bonding agent contained also a free radical compound.
5. 5. A composite according to claim 4 wherein the free radical compound is a peroxide.
6. 6. A composite according to claim 5 wherein from 0.1 to 5 parts by weight of peroxide is present based on 100 parts by weight of cellulose fibers.
7. 7. A composite according to any preceding claim wherein the bonding agent is vinyltri (2-methoxyethoxy) silane or gamma-aminopropyltriethoxy silane.
8. 8. A composite according to any preceding claim wherein polymethylene polyphenyleneisocyanate is present.
9. 9. A composite according to claim 8 wherein from 0.1 to 5 parts by weight of polymethylenepolyphenyleneisocyanate is present based on weight of polyethylene matri.
10. 10. A composite according to any preceding claim wherein from 0.1 to 10 parts by weight of silane bonding agent is present, based on 100 parts of cellulose fibers by weight.
11. 11. A composite according to any preceding claim wherein the fibers have an aspect ratio from 2 to 150.
12. 12. A composite according to any preceding claim wherein 9, YA1. 1 D 6

    A + ". a acid U. 14011
13. 13. The composites or ole to 7Awherein the fibers are softwood pulp.

    k nA tuckclol
14. 14. fke composites of Il.z I t 7 wherein the matrix contain a partlculate filler.
15. 15. The composite o! Gla; o 7wherein the polyethylene is copolymer from a monomer mixture comprising at least fifty percent of polyethylene.
16. 16. A composite comprising from 9 to 45X of discontinuous cellulose fibers dispersed in a matrix comprising from 5 to 95X by weight of polyethylene being coupled to each other by reaction with 0.1 to 10% by ueight of silane and 0.1 to 10% by weight of maleic anhydride and 0.1 to 10% by weight of peroxide.
17. 17. The composite as defined in claim 16 wherein the silane is gamma methacryloxypropyltrimethoxysilane of formula:

    is
18. 18. The composite as defined in claim 16 wherein the silane #f vinyltri (2-methoxyethoxy) silane of formula: CH2 = CH - Si -(OC2H, OCH3)3
19. 19. The composite as defined in claim 16 wherein the silane is H2N -C3H4 Si (OCH2 CH,)
20. 20. The composite as defined in claim 16 wherein the fibers are softwood pulp.
21. 21. The composite as defined in claim 16 wherein the fibers are hardwood pulp.
22. 22. The composite as defined in claim 16 wherein the fibers have an aspect ratio from 2 to 150.
23. 23. The composite as defined in claim 16 wherein the fiber contain a particu late filler.

    A =zsto at
24. 24. Tke composite! of claims 1 to 7 wherein the polyethylene is present in an amount of 10 to 90 parts by weight based on 100 parts of total composite weight.

    40
25. 25. Te composites of claims 1 to 9 wherein the cellulose fiber is present in an amount from 10 to 90 parts by weight based on 100 parts of total composite weight.
26. 26. A compression molding made from

    composites of claims 1 to q.
27. 27. A compression molding made from

    composites #of claims 16 to 23.
28. 28. An injection molding made from

    composites of claims 1 to

    16 to 23.