WO2013003591A2

WO2013003591A2 - Moisture resistant polymeric composites

Info

Publication number: WO2013003591A2
Application number: PCT/US2012/044647
Authority: WO
Inventors: Jeffrey Jacob Cernohous; Adam R. Pawloski; Neil R. Granlund
Original assignee: Interfacial Solutions Ip, Llc
Priority date: 2011-06-28
Filing date: 2012-06-28
Publication date: 2013-01-03
Also published as: WO2013003591A3

Abstract

A melt processable composite derived from the combination of a polymeric matrix, a cellulosic material, a coupling agent, a multifunctional coupling agent and an optional desiccant. The composite exhibits color fastness and resistance to moisture.

Description

MOISTURE RESISTANT POLYMERIC COMPOSITES

CROSS REFERENCE TO RELATED APPLICATONS

[0001] This application claims priority to U.S. Provisional Patent Application No. 61/501,886 filed June 28, 2011, and U.S. Provisional Patent Application No. 61/618,929 filed April 2, 2012, the disclosures of which are herein incorporated by reference in their entirety.

TECHNICAL FIELD

[0002] This disclosure is directed to polymer composites containing cellulosic materials that are moisture resistant and possess desired color fastness. The inclusion of a coupling agent, a multifunctional coupling agent, and an optional desiccant enable the composite to resist moisture uptake while possessing desirable mechanical properties.

BACKGROUND

[0003] Synthetic fiber reinforced thermoplastic composite materials have become staples for automotive, construction, defense, aerospace and consumer products. Most of these composites are derived from glass or carbon fiber reinforced engineering thermoplastics. However, polyolefin based composite materials are being applied in cost sensitive applications that demand higher performance. Examples include glass reinforced polypropylene (PP) composites and natural fiber reinforced polyolefin composites. Wood polymer composite based products (WPC's) have rapidly penetrated non- structural wood applications because they offer the consumer low maintenance attributes and durability.

[0004] WPC's have found broad application in the building and construction industry, especially for non-structural applications. These materials typically comprise a thermoplastic matrix filled with 20 to 80 wt % of a cellulosic fiber. As a result, the composite is often very sensitive to moisture. When a composite component is exposed to high humidity conditions, it is not uncommon for it to absorb as much as 10% of its mass in moisture. This absorption, and the resulting swelling, can have an extremely deleterious effect on the composite's dimensional stability, color fastness, microbial resistance and aesthetics. Additives have been utilized to improve the mechanical properties and moisture resistance of WPC's. However, conventional technologies arguably do not provide adequate protection for these applications. The WPC's often exhibit poor moisture resistance, which in turn may cause the color or aesthetics of the article to fade when exposed to wet or humid environments over time.

SUMMARY

[0005] The moisture resistance, weatherability and color fastness of WPC's may be enhanced by the inclusion of a coupling agent and a multifunctional coupling agent. The combination of a coupling agent with a multifunctional coupling agent at specific loading levels in WPC's enhances the moisture resistance and color fastness of the WPC. Additionally, WPC's containing the specific materials also demonstrated greater retention of mechanical properties after steam exposure. In certain embodiments, composite formulations containing the present combination exhibited slight darkening rather than lightening in color after steam exposure. Generally, the additives provided better color retention and fastness when compared to conventional composite formulations. In another embodiment a desiccant is utilized to address the moisture content of raw material for WPC's during melt processing and allow the coupling agent to function properly.

[0006] For purposes of the present disclosure, the following terms used in this application are defined as follows:

"color fastness" means a polymeric composite material that retains at least its original color without fading after exposure to moisture over an extended or repeated period of time.

"coupling agent" means a composition that improves the compatibility and interfacial adhesion between the thermoplastic matrix and the cellulosic material and any other fillers or materials.

"desiccant" means a material that can effectively irreversibly react with or bind water under melt processing conditions. "multifunctional coupling agent" means a composition having at least two distinct functional groups all capable of interaction with other materials in a melt processable composition.

"resistance to moisture" or "moisture resistance" means a polymeric composite material that does not absorb more than the greater of (i) 2.5% water by weight of the total composite, or (ii) 8.5% by weight of cellulosic material, when allowed to soak in a room temperature bath for over 35 days.

"hydrophilic synergist" means a water soluble or dispersible material that when combined with a desiccant improves the efficacy or kinetics of its reaction with moisture.

[0007] The above summary is not intended to describe each disclosed embodiment or every implementation of the claimed subject matter. The detailed description that follows more particularly exemplifies illustrative embodiments.

DETAILED DESCRIPTION

[0008] The combination of a coupling agent and a multifunctional coupling agent in a polymer and cellulose composite enhances the moisture resistance and color fastness of the resulting WPC. Alternatively, the function of the multifunctional coupling agent in the WPC may also be addressed by a tetraalkyl orthosilicate compound. The composite derived from the combination of the polymeric matrix, a cellulosic material, a coupling agent, and a multifunctional coupling agent exhibits exceptional moisture resistance and color fastness upon repeated or extended exposure to water or water vapor. Additionally, the optional use of a desiccant and hydrophilic synergist during melt processing can reduce moisture present in the raw materials.

[0009] The polymeric matrix functions as the host polymer and is a primary component of the melt processable composition. A wide variety of polymers conventionally recognized in the art as suitable for melt processing are useful as the polymeric matrix. The polymeric matrix includes polymers that are suitable for melt processing, especially when combined with cellulosic materials. Both hydrocarbon and non-hydrocarbon polymers are applicable. Examples of useful polymeric matrices include, but are not limited to, polyamides, polyimides, polyurethanes, polyolefmes, polystyrenes, polyesters, polycarbonates, polyketones, polyureas, polyvinyl resins, polyacrylates, and polymethylacrylates. The polymeric matrix may comprise from about 20% to about 90% by weight of the entire composition.

[0010] In certain embodiments, polymeric matrices may include high density polyethylene (HDPE), low density polyethylene (LDPE), linear low density polyethylene (LLDPE), polypropylene (PP), polyolefm copolymer (e.g., ethylene -butene, ethylene -octene, ethylene vinyl alcohol), polystyrene, polystyrene copolymers (e.g., high impact polystyrene, acrylonitrile butadiene styrene copolymer) polyacrylates, polymethacrylates, polyesters, polyvinylchloride (PVC), fluoropolymers, liquid crystal polymers, polyamides, polyether imides, polyphenylene sulfides, polysulfones, polyacetals, polycarbonates, polyphenylene oxides, polyurethanes, thermoplastic elastomers, epoxies, alkyds, melamines, phenolics, ureas, vinyl esters or combinations thereof. Polyolefins are well suited for many applications.

[0011] Useful polymeric matrices include blends of various thermoplastic polymers and blends thereof containing conventional additives such as antioxidants, light stabilizers, fillers, fibers, antiblocking agents, heat stabilizers, impact modifiers, biocides, compatibilizers, flame retardants, plasticizers, tackifiers, colorants and pigments. The polymeric matrix may be incorporated into the melt processable composition in the form of powders, pellets, granules, or in any other extrudable form.

[0012] Cellulosic materials may be utilized in melt processable compositions as fillers to impart specific physical characteristics, reduce cost of the finished composition or both. Cellulosic materials generally include natural or wood based materials having various aspect ratios, chemical compositions, densities, and physical characteristics. Non-limiting examples of cellulosic materials include wood flour, wood fibers, sawdust, wood shavings, newsprint, paper, flax, hemp, rice hulls, kenaf, jute, sisal, and peanut shells. Combinations of cellulosic materials and a modified polymer matrix may also be used in the melt processable composition. The amount of cellulosic filler in the composite material may be adjusted to address end use processing. For example, cellulosic filler amounts may be adjusted in the composite to prevent defects in thermoforming applications, such as tearing during molding. The cellulosic materials may be included in the WPC in amount from about 10% to about 90% by weight. In certain embodiments, a master batch with greater than 60% by weight of cellulosic materials may be created and subsequently let down into a host polymer.

[0013] The melt processable composition includes coupling agents to improve the compatibility and interfacial adhesion between the thermoplastic matrix and the cellulosic material and any other fillers. Non-limiting examples of coupling agents include functionalized polymers, organotitanates and organozirconates. Preferred functionalized polymers included functionalized polyolefms, maleated polyolefms, polyethylene-co-vinyl acetate, polyethylene-co-acrylic acid, and polyethylene-co-acrylic acid salts. The coupling agents may be included in the WPC in amount from about 0.25% to about 15% by weight. In certain embodiments, the coupling agent may be included at about 0.5% to about 5% by weight.

[0014] The physical and aesthetic properties of the WPC is enhanced by also including a multifunctional coupling agent in combination with those coupling agents previously noted. The combination of coupling agents with the WPC prevents the uptake of water or moisture and enables color fastness. For purposes of this disclosure, a multifunctional coupling agent has at least two distinct functional groups all capable of interaction with other materials in the melt processable composition, such as for example, other coupling agents and available hydroxyl groups on fillers. With no desire to bound by theory, it is believed that the interaction between the multifunctional coupling agent make take the form of covalent bonding, ionic bonding, hydrogen bonding, dipole bonding or attraction by van der Waals forces.

[0015] Non- limiting examples of multifunctional coupling agents include various organosilanes. In one embodiment, 3-glycidoxypropyltrimethoxysilane is well suited to prevent moisture uptake of the WPC and exhibits a very desirable color fastness. In certain embodiments alkoxysilanes are desirable. In certain embodiments, the multifunctional coupling agent may be included in the WPC in amount from about greater than 1.0% to about 5% by weight. Alternatively, the multifunctional coupling agent may be 3.5%) to 10%o by weight of the cellulosic material.

[0016] In an alternative embodiment, terra alkyl orthosilicates are used with the coupling agent in the WPC to generate a resulting product that is resistant to moisture and does not fade in color over time. In one embodiment, tetraethyl orthosilicate is well suited to for achieving moisture resistance and color fastness in WPC applications. The tetra alkyl orthosilicate may be included in the WPC in amount from about 0.25% to about 5% by weight.

[0017] In another alternative embodiment, a desiccant is utilized to address the moisture content of any additive or filler during melt processing. The function of the desiccant in the melt blend is to tie up the moisture present in the filler, any additives, and the polymer matrix in order to allow the coupling agent to serve its intended function. The desiccant may be any conventional material capable of moisture uptake and suitable for application in melt processed polymeric matrices. In one embodiment, the desiccant is selected from calcium oxide, magnesium oxide, strontium oxide, barium oxide, aluminum oxide, or combinations thereof. Those of ordinary skill in the art of melt processing polymers are capable with knowledge of this disclosure of selecting a specific desiccant in combination with a compatibilizer to achieve the beneficial results identified in this disclosure. The amount of desiccant will vary, but may include a range of about 1 to 80 wt % of the formulation in the compatibilizer blend.

[0018] In another embodiment, a hydrophilic synergist is added to improve the efficacy of the desiccant material at scavenging moisture during melt processing. The hydrophilic synergist acts to help disperse the desiccant in the polymeric matrix, subsequently exposing more surface area to moisture and improving the overall kinetics and efficiency of the moisture scavenging event. Non-limiting examples of suitable hydrophilic synergists include polyalkylene oxide polymers and copolymers and polyvinyl alcohol copolymers, and organic polyols (e.g., glycerol, pentaerythirtol). The desiccant and optional hydrophilic synergist may improve the processibility and reduce the surface defects encountered when melt processing polymeric matrices containing fillers. [0019] The desiccant and optional hydrophilic synergist may be pre-compounded in a thermoplastic carrier to form a concentrate and subsequently added to a filled polymeric matrix to improve dispersion, processibility, and reduce melt defects. For example, the concentrate may be supplied separately as a pellet or masterbatch concentrate to the melt processable composition. The additive may optionally include the hydrophilic synergist and/or a polymeric carrier material. One example of a concentrate with a polymeric carrier is XP340 from Interfacial Solutions LLC (River Falls, WI).

[0020] The melt processable composition can be prepared by any of a variety of ways. For example, the polymeric matrix, filler, coupling agent, multifunctional coupling agent and desiccant can be combined together by any of the blending means usually employed in the plastics industry, such as with a compounding mill, or a Banbury mixer. The melt processable materials may be used in the form, for example, of a powder, a pellet, or a granular product. The mixing operation is most conveniently carried out at a temperature above the melting point or softening point of the polymeric matrix. The resulting melt- blended mixture can be either extruded directly into the form of the final product shape or pelletized or otherwise comminuted into a desired particulate size or size distribution and fed to an extruder, which typically will be a single-screw extruder, that melt-processes the blended mixture to form the final product shape. In one embodiment, WPC may be injection molded. The resulting composite exhibits superior performance results.

[0021] Melt-processing typically is performed at a temperature from 120° to 300° C, although optimum operating temperatures are selected depending upon the melting point, melt viscosity, and thermal stability of the composition. Different types of melt processing equipment, such as extruders, may be used to process the melt processable compositions of this invention. Those of ordinary skill in the art in polymer processing are able to select appropriate operating conditions based upon the specific materials utilized in the composite.

[0022] The resulting articles produced by melt processing the inventive composition exhibit desirable mechanical characteristics in the field of composite structures. For example, a WPC comprised of a polypropylene matrix, wood flour, maleated polypropylene and an epoxysilane, exhibit desirable tensile strength, increases in flexural modulus, and flexural strength and impact strength.

[0023] CIE L*a*b* (CIELAB) is the most complete color space specification. It is often used to describe the colors visible to the human eye and was created to serve as a reference model. The three coordinates of CIELAB represent the lightness of the color (L*), its position between red/magenta and green (a*), and its position between yellow and blue (b*). An L* value of zero represents black and an L* value of 100 indicates white. For purposes of this disclosure, the L* value is used to demonstrate fading or lightening of the WPC after exposure to steam over a given period of time.

[0024] In certain embodiments, the L* value of the resulting WPC, after exposure to steam for a twenty-four hour period, does not increase. An increase in the L* value would represent an undesirable lightening of the material. Wood materials are hydrophilic and tend to absorb water. With the absorption of water, a conventional WPC will generally tend to fade in color. Color fastness, for the purpose of this disclosure, indicates a resistance to fade, which may be measured according to the L* value of the WPC. An increase in the L* value, essentially a move toward the L* limit of 100, is considered whitening or fading of the material. In certain commercial applications, it is preferred that the WPC's retain this color over continued use, particularly under exposure to continuous wet or moist environments. For example, the WPC may be applied to household applications that are subject to continued dishwashing. It is important under those circumstances that the material minimally fades over its useful life. In some embodiments, the resulting WPC may even demonstrate a negative change in its L* value after exposure to moisture. A negative change in L* is an indication of darkening. Often this may be desirable aesthetic property and comparable to the aging of wood.

[0025] In another embodiment, the desired L* value having no change, or a negative change, is coupled with an increase in the a* value. According to CIELAB, a negative change in a* values indicate a move toward green while positive values indicate magenta. In certain embodiments, the combined coupling agent and multifunctional coupling agent enable a darkening of the WPC after exposure to water or water vapor over time. The darkening is exemplified by either no change, or a negative change, in the L* value and a positive change in the a* value. Certain embodiments exhibit a negative change in L* of 5 points or more and positive change in a* of 5 or more points.

[0026] Some embodiments prevent the significant uptake of moisture by cellulose materials that are generally very hydrophilic. For example, certain embodiments are capable of achieving an average water uptake of (i) 2.5% water by weight of the total composite, or (ii) 8.5% by weight of cellulosic material, when allowed to soak in a room temperature bath for over 35 days.

EXAMPLES

[0027] Materials. The materials that were utilized to formulate the composite materials described in this work are given in Table 1.

Table 1. Materials Description

[0028] Experimental Details. Wood polymer composite (WPC) materials were prepared and characterized as described in the following sections.

Composite Formulations

Table 2 lists the compositions of formulations tested in these experiments. Table 2. Wood Polymer Composite Formulations

[0029] Preparation and Characterization of Composite Examples A-F

Composite Examples A-E, as comparative Examples, and composite Example F were prepared and tested using the following protocol. Polymer, filler (wood flour) and CA and the multifunctional coupling agent, if utilized, were blended in a polyethylene bag. The resulting blend was volumetrically fed into the feed zone of a 27 mm co-rotating twin screw extruder fitted with a strand die (commercial available from American Leistritz Extruder Corporation, Sommerville, NJ). All Examples were processed at 125 rpm screw speed using the following temperature profile: zone 1 = 170 °C, zone 2-7 = 180°C, and zone 8 = 160°C. The resulting strands were subsequently cooled in a water bath and pelletized into 0.64 cm pellets to produce the composite formulation. The resulting pellets were injection molded into test specimens following ASTM D638 (tensile) and D790 (flexural) specification. Injection molding on composite formulations was performed using an 85 ton machine (commercially available from Engel Corporation, York, PA) having a barrel and nozzle temperature of 200 °C. The tensile and impact resistance properties were subsequently tested as specified in the ASTM methods.

[0030] Water Absorption of Examples A-F

To test the effects of water on Examples A-F, molded specimens were subjected to two types of tests. The first test measured water absorption by the composite. In this test, Examples A-F were allowed to soak in a room temperature water bath for 35 days. Periodically, the Examples were removed from the water bath, dried with a towel to remove surface moisture, and weighed. The second test was designed as an accelerated aging test. For this test, specimens were subjected to steam between 34.5 and 103 kPa in a closed vessel in 8 hour increments. [0031] Room Temperature Water Uptake

FIG. 1 is a graph of the average percent water uptake of the composite over time for Examples A-F. When a multifunctional coupling agent is added to polypropylene and wood, a reduction in water absorption is found. This demonstrates that when used alone, the multifunctional coupling agent imparts an improved barrier to water absorption by the wood.

[0032] Mechanical Properties of Examples A-F After Accelerated Aging

To simulate an accelerated aging of the polymer wood composites in a wet environment, molded test specimens were subjected to a low pressure steam bath for 8 hours. After 8 hours, the test specimens were allowed to condition in a 50% humidity environment for 48 hours prior to testing tensile and impact resistance properties. Table 3 lists the results from tensile tests, and Table 4 lists the results from impact resistance tests before and after steam treatment.

[0033]

Table 3. Tensile Properties of Examples A-F Before and After 8 Hour Steam Treatment

Table 4. Impact Resistance of Examples A-F Before and After 8 Hour Steam Treatment

[0034] As indicated by the data in Tables 3 and 4, the addition of the coupling agent generally improves mechanical properties of tensile strength, modulus, and impact resistance. Increasing the concentration of the coupling agent increases tensile strength and impact resistance. This trend is preserved in the Examples subjected to 8 hours of steam treatment, despite a significant drop in tensile properties after steam treatment.

[0035] Example E containing solely a multifunctional coupling agent (without a coupling agent) exhibits properties very close to those of the comparative formulation A, both before and after steam treatment. However, the use of both the multifunctional coupling agent and the coupling agent for formulation F significantly improves mechanical properties over all other formulations. The improvement is substantially greater than the coupling agent alone, even when added at significantly higher concentration. Formulation F demonstrates a 30% increase in tensile strength above the control formulation A and about 17% increase over formulation C that contains the same concentration of the coupling agent. The results for impact resistance are even more substantial with more than a 50% increase over formulation A and more than 40% increase over formulation C. Furthermore, after steam treatment, the tensile and impact resistance properties for formulation F are largely unchanged. [0036] Surface Appearance and Color Fastness After Steam Treatment of Examples A-F A screening process was used to evaluate the effects of heat and moisture on color fastness and the surface appearance of the composites. For these tests, Examples were placed in a pressurized steam bath between 10-15 psi pressure for intervals of 8, 16, and 32 hours. After steam treatment the Examples were removed, allowed to dry, and photographed. FIGS. 2 (a-d) display photographs of Examples from Examples A, C, and F prior to and after steam treatment at various intervals. As seen by the photographs, the addition of the multifunctional coupling agent dramatically improved the surface appearance of the composite. Even after 32 hours of steam treatment, Example F exhibits a smooth surface finish with minimal swelling of wood fibers. Example F exhibited desired color fastness. Table 5.

Color data summary

[0037] Preparation and Characterization of Example G - coupling agent Example G was prepared using the following protocol. Polymer (polypropylene, Grade 5626 2mi from Exxon Mobil, Irving, TX), maleic anhydride (Alpha Aesar, Ward Hill, MA) and peroxide (2,5-Dimethyl-2,5-di(tert-butylperoxy)hexane, United Initiators, Elyria, OH) were blended in a polyethylene bag in the following percentages: 97.8% of the noted poypropylene, 2% maleic anhydride, 0.2% peroxide. The resulting blend was volumetrically fed into the feed zone of a 26 mm co-rotating twin screw extruder (commercially available from Labtech Engineering Company, Praksa, Maung, Samutprakan, Thialand). Calcium oxide (Mississippi Lime, St. Louis, MO) was used as a desiccant. The extruder was fitted with a side stuffer which fed the desiccant in zone 4 at a rate such that desiccant was 50% of the total formulation . The Examples were processed at 300 rpm screw speed and extruded through a strand die using the following temperature profile: zone 1 = 150°C, zone 2-3 = 190°C, zone 4-5: 200°C, zone 6-9 220°C and die = 220°C. The resulting strands were subsequently cooled in a water bath and pelletized into 0.64 cm pellets. The resulting product was used to produce Example H..

[0038] Preparation and Characterization of Composite Example H

Composite sample H was prepared and tested using the following protocol. Polymer (PP), filler, coupling agent, Example G, and the multifunctional coupling agent (MFCA) were blended in a polyethylene bag. The resulting blend was volumetrically fed into the feed zone of a 27 mm co-rotating twin screw extruder fitted with a strand die (commercial available from American Leistritz Extruder Corporation, Sommerville, NJ). All Examples were processed at 125 rpm screw speed using the following temperature profile: zone 1 = 170 °C, zone 2-7 = 180°C, and zone 8 = 160°C. The resulting strands were subsequently cooled in a water bath and pelletized into 0.64 cm pellets to produce the composite formulation. The resulting pellets were injection molded into test specimens following ASTM D638 (tensile) and D790 (flexural) specification. Injection molding on composite formulations was performed using an 85 ton machine (commercially available from Engel Corporation, York, PA) having a barrel and nozzle temperature of 200 °C. The tensile and impact resistance properties were subsequently tested as specified in the ASTM methods. [0039] From the above disclosure of the general principles and the preceding detailed description, those skilled in this art will readily comprehend the various modifications and embodiments to which the present invention is susceptible. Therefore, the scope of the invention should be limited only by the following claims and equivalents thereof.

Claims

What is claimed is:

1. A composition comprising a composite derived from the combination of a polymeric matrix, a cellulosic material, a coupling agent and a multifunctional coupling agent, wherein the composite exhibits color fastness and resistance to moisture.

2. The composition of claim 1, further comprising a desiccant.

3. The composition of claim 1, wherein the color fastness is demonstrated by either no change or a negative change in an L* value under the CIELAB color coordinate system after a twenty-four hour exposure to steam.

4. The composition of claim 3, wherein the negative change in the L* value is greater than

5. The composition of claim 1, wherein the color fastness is demonstrated by a positive change in an a* value under the CIELAB color coordinate system after a twenty-four hour exposure to steam.

6. The composition of claim 1, wherein composite darkens in color after a twenty- four hour exposure to steam as demonstrated by a positive change in an a* value and a negative change in an L* value under the CIELAB color coordinate system.

7. The composition of claim 6, wherein the a* value and the L* value change by 5 points or more.

8. The composition of claim 1, wherein the average water uptake is less than 2.5 % water by weight of the composite when allowed to soak in a room temperature bath for over 35 days.

9. The composition of claim 1, wherein the multifunctional coupling agent is an alkoxy silane.

10. The composition of claim 9, wherein the alkoxy silane is a

3-glycidoxypropyltrimethoxysilane.

11. The composition of claim 1 , wherein the multifunctional coupling agent is present at levels of (i) greater than 1% by weight of the composite, or (ii) about or greater than 3.5% by weight of the cellulosic material.

12. A composition comprising a composite derived from the combination of a polymeric matrix, a cellulosic material, a coupling agent and a tetraalkyl orthosilicates.

13. A method comprising melt processing a polymeric matrix, a cellulosic material, a coupling agent, a multifunctional coupling agent, and optionally a desiccant to form a composite that exhibits color fastness and resistance to moisture.

14. A method comprising a melt processing a polymeric matrix, a cellulosic material, a coupling agent, optionally a desiccant, and tetraalkyl orthosilicates to form a composite.

15. A composition comprising a composite derived from the combination of a polymeric matrix, a cellulosic material, a coupling agent, a multifunctional coupling agent, and a desiccant.

16. The composition of claim 15, wherein the desiccant includes calcium oxide, magnesium oxide, strontium oxide, barium oxide, aluminum oxide, or combinations thereof.

17. The composition of claim 15, further comprising a hydrophilic synergist.

18. The composition of claim 17, wherein the hydrophilic synergist includes olyalkylene oxide polymers, polyalkylene oxide copolymers, polyvinyl alcohol copolymers, or organic polyols.

19. The composition of claim 15, wherein the multifunctional coupling agent is an alkoxy silane.

20. The composition of claim 1, wherein the cellulosic material is greater than 60% by weight of the composite.