Abstract:
A system or apparatus and associated method is provided to remove pinholes from bio composite materials in order to increase the strength and functionality of the composites. The apparatus and method uses an inert gas, such as nitrogen, that is introduced into the processing chamber where the fiber and the polymer are combined to form the biocomposite material. The inert gas is introduced through an inlet into the chamber and creates a pressure differential between the interior and exterior of the product mixture to force the air and moisture out of the mixture and through an outlet or vent on the chamber, along with the inert gas and any other gases, thereby preventing or at least significantly limiting the formation of pinholes in the biocomposite product.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application claims priority from U.S. Provisional Patent Application Ser. No. 61/948,844 filed on Mar. 6, 2014, the entirety of which is expressly incorporated herein by reference. 
     
    
     FIELD OF THE INVENTION 
       [0002]    The subject matter disclosed herein relates generally to biocomposite materials and, in particular, to an apparatus or system and method for the reduction and/or removal of pin holes in biocomposite materials formed during their production in order to increase the strength and functionality of the biocomposite. 
       BACKGROUND OF THE INVENTION 
       [0003]    Fibrous materials such as straw from flax, sisal, hemp, jute and coir, banana, among others, are used in the formation of biocomposite materials, where the fibrous material is combined with another compound(s), such as a polymer or blend of polymers, The fibrous materials can he in the form of raw fibrous materials, or fibers selected from the components of the raw fibrous material, such as the cellulose fibers once separated from the hemicelluloses, lignin and impurities components of the raw fibrous materials. 
         [0004]    Once the fibers, such as from flax, hemp, jute, coir, sisal and banana among other sources, are cleaned, and processed, they are combined with polymers to make biocomposite products. However, during this manufacturing stage for the biocomposite materials, in conventional systems and methods, air, other gases and moisture are trapped inside the resulting biocomposite product. This air and moisture retained in the biocomposite material create pinholes in the biocomposite product formed from the material. In particular, pinholes are air and moisture pockets formed during the processing of the biocomposite product development, when processed fiber is blended with polymer materials, that can expand such as when subjected to heat and pressure during extraction/injection molding process to form the biocomposite materials. These pinholes render the resulting biocomposite material quite porous, which significantly weakens the resulting biocomposite product. 
         [0005]    As a result, an apparatus or system and method for reducing or removing the air and moisture present in the biocomposite material, and consequently the pores or pinholes formed in the biocomposite product formed from the biocomposite material in order to increase the strength and durability of biocomposite products is needed. 
       SUMMARY OF THE INVENTION 
       [0006]    According to one aspect of an exemplary embodiment of the present disclosure, a system or apparatus and associated method is provided to remove pinholes from biocomposite materials in order to increase the strength and functionality of the biocomposites. The apparatus and method uses an inert gas, such as nitrogen, that is introduced into the processing chamber, which can he the chamber where the fiber and the polymer are combined to form the biocomposite material or the chamber in which the biocomposite material is formed into the biocomposite end product. The inert gas is introduced through an inlet into the chamber and passes into the mixture of the fiber and polymer to for a pressure differential within the chamber to force the air and moisture out of the mixture through an outlet, along with the inert gas and any other gases, to remove any pinholes in the final biocomposite product. 
         [0007]    According to another aspect of an exemplary embodiment of the present disclosure, the apparatus, system and method optimizes the residence time of the biocomposite raw materials in the processing chamber during the material formation or molding processes to provide a biocomposite product with improved properties, including enhanced strength. 
         [0008]    These and other objects, advantages, and features of the invention will become apparent to those skilled in the art from the detailed description and the accompanying drawings. It should be understood, however, that the detailed description and accompanying drawings, while indicating, preferred embodiments of the present invention, are given by way of illustration and not of limitation. Many changes and modifications may be made within the scope of the present invention without departing from the spirit thereof, and the invention includes all such modifications. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0009]    The drawing furnished herewith illustrates a preferred construction of the present disclosure in which the above advantages and features are clearly disclosed as well as others which will be readily understood from the following description of the illustrated embodiment. 
           [0010]    In the drawing: 
           [0011]    The FIGURE is a schematic view of an exemplary embodiment of an apparatus constructed according to the present disclosure. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0012]    With reference now to the drawing FIGURE in which like reference numerals designate like parts throughout the disclosure, a system or apparatus provided for forming a biocomposite material product from various types of fibers and or fibrous materials and various types of polymers is illustrated generally at  10 . This apparatus, system and method is related to the processes disclosed in co-owned and co-pending U.S. patent application Ser. No. 14/087326, filed on Nov. 22, 2013, the entirety of which is expressly incorporated by reference herein. 
         [0013]    In the illustrated exemplary embodiment, the system  10  includes a processing chamber  12  which in the illustrated embodiment is formed as a mold in a suitable molding process, such as an injection or extrusion molding process. The chamber  12  includes a fiber inlet  14 , a polymer inlet  16 , a gas inlet  18 , a gas outlet  20 , a vent  22  and a product/material outlet  24 . In the method, the processing chamber  12  is utilized to apply sufficient heat and pressure to the fiber and polymer introduced into the chamber  12  to form the biocomposite material or product  26  that exits the chamber  12  through the product outlet  24 . Alternatively, instead of a product outlet  24 , the chamber  12  can be formed as an openable structure, such as a mold having separable halves or portions, in order to enable the biocomposite product  26  formed therein to be removed from the chamber  12 , such as in an injection molding process. Further, the chamber  12  can be a chamber utilized to form the biocomposite material by mixing the selected polymer(s) and fiber(s) therein, with the product exiting the chamber  12  through the outlet  24  being the biocomposite material. 
         [0014]    In operation, the fibrous material  28 , of any suitable type, and the polymer  30 , of any suitable type, are introduced through the respective inlets  14  and  16  into the chamber  12 , which can be any suitable type of chamber, such as a barrel extruder for an extrusion process or a mold for an injection molding process. The fiber or fibrous material  28  and the polymer  30  are subjected to temperatures and pressures within the chamber  12  as are known in the art to form them into the biocomposite material/product  26  having the desired shape as defined at least in part by the shape of the interior of the chamber  12 . The fibrous material  28  and polymer  30  can also optionally be mixed along with the application of pressure and heat to form the material  26 . 
         [0015]    During the biocomposite material/product  26  manufacturing process within the chamber  12 , an inert gas  32 , for example, nitrogen, helium, or argon gas, among other suitable inert gases, is introduced through the gas inlet  18  into the chamber  12 . An inert gas  32  is selected due to its ability to interact mechanically with the fiber  28 , the polymer  30  and/or the product  26 , and in a non-chemically reactive manner, so as not to affect or alter the composition of the biocomposite product  26  or its components. The as  32  is introduced at a regulated temperature and/or pressure to develop and maintain a pressure difference in the processing chamber  12 , i.e., between the interior and exterior of the molten biocomposite material (fiber/polymer) mass within the chamber. This pressure difference acts on the product mass  26 , such as by compressing the mass  26 , and forces the air and moisture out of the product  26  within the chamber  12 . 
         [0016]    This temperature and pressure for the incoming inert gas  32 , as well as the flow rate, can be maintained through the use of a suitable controller  34  operably connected to the gas inlet  18 , gas outlet  20  and vent  22 , as well as to a sensor  36  disposed on the chamber  12  to continuously monitor the temperature and pressure differentials within the chamber  12 . As the differential changes during the production process, the controller  34  can operate the inlet  18  to allow additional gas  32  at the necessary temperature and pressure to flow into the chamber  12 , or the vent  22  to enable the gas  32  to escape from the chamber  12 . 
         [0017]    As the pressure differential generated by the gas  32  acts on the product  26 , the gas  32  mechanically compresses the product  26  and forces the air and moisture within the product  26  out of the product  26  and out of the chamber  12  through the gas outlet  20 . In one exemplary embodiment for the apparatus, system and method, the inert gas  32  is introduced into the chamber  12  and as to result it protects the degradation of fiber and reduces the melt temperature, while increasing the viscosity of the product/mass/material  26  and develop the necessary pressure in the chamber  12 . The particular flow rate of the gas into the chamber  12  depends upon the chamber dimensions, processing conditions (including screw speed (rpm), diameter, residence time, and temperature, alone or in combination with one another, among other conditions) biocomposite material ingredients, fiber loading (%) of fiber, moisture content in the fiber, among other parameters. In one particular example, for a biocomposite formed with HDPE and 15% (w/w or v/v) fiber loading, 0.6 ml/min of inert gas was introduced to the chamber  12  during processing to achieve a pressure differential within the chamber  12  to remove the pinholes in the biocomposite product  26 . The pressure differentials to be created within chamber  12  depend on type of polymer, fiber % and fiber moisture content of the product components, as well as the processing conditions or parameters within the chamber  12 , such as those discussed previously, among other considerations. For example, the pressure differential between the interior and exterior of the product mass in the chamber  12  varies in the range of 1-20% of the chamber pressure for on a thermoplastic-based biocomposite with up to 30% w/w or v/v of fiber loading. Without introduction of the inert gas into the chamber  12 , the normal pressure build up in the chamber  12  due to the processing and attributes of the biocomposite composition, for example, the fiber %, fiber moisture content, type of polymer and its moisture content, etc., allows any moisture and gases present in the composition to produce pores i.e., pin holes, in the biocomposite product  26 . However, when the inert gas is directed into the chamber  12 , the pressure differential created between the interior of the material (lesser pressure) and the exterior of the material (greater pressure) compresses the biocomposite material  26  to urge the moisture and gas present in the material  26  out of the material  26  to be carried away from the material  26  and vented out of the chamber  12  along with the inert gas, producing a non-porous, solid biocomposite material  26  without the pin holes. 
         [0018]    In one exemplary embodiment, the residence time of the fiber  28  and polymer  30  within the chamber  12  is optimized to effectively remove all the air bubbles and moisture within product  26  during the processing under the pressure differential created by the introduction of the inert gas  32 . Factors that affect the required residence time, and thus the size of any pinholes that would otherwise be formed in the product  26  include, but are not limited to: the particle size and shape of the fiber  28 , the particle distribution of the fiber  28  within the polymer  30 , the viscosity of the polymer  30 , the surface tension at the chamber  12 /polymer  30  interface, the temperature within the chamber  12 , time, and the pressure within the chamber  12 . In a particular exemplary embodiment, the volume of the inert gas introduced to the system/chamber  12  will be dependent upon the following:
       1. Type of base polymer of biocomposite   2. Polymer processing temperature   3. Composition of fiber percentage in biocomposite formulation   4. Volume of materials (biocomposite formulation) processing per hours in the systems.       
 
         [0023]    This determination can be done in real-time to provide an inert gas volume optimization for the system/chamber  12  by using heat and trail methods, as are known in the art, by employing the above four factors in those analyses. Further, in another particular exemplary embodiment, it is also contemplated to use a suitable model predictive control optimization-based control strategy for determine the volume of inert gas introduced to the system/chamber  12  using the above four variables as the inputs to the control strategy. 
         [0024]    When the product  26  is formed with the inert gas  32  to remove the air and moisture from the fiber  28 /polymer  30  mass or biocomposite mixture from which the product  26  is formed, the benefits to the resulting product include, but are not limited to: improved quality of the product  26 , such as, but not limited to improved product  26  consistency, increased strength and durability of the product  26 , reduced shrinkage at crystalline regions of the product  26 , enhanced dimensional stability for the product  26 , a reduction in the differential stress and residual stress of the product  26 , and the ability to maintain the temperature gradient inside the chamber  12  during processing. 
         [0025]    It should he understood that the invention is not limited in its application to the details of construction and arrangements of the components set forth herein. The invention is capable of other embodiments and of being practiced or carried out in various ways. Variations and modifications of the foregoing are within the scope of the present invention. It also being understood that the invention disclosed and defined herein extends to all alternative combinations of two or more of the individual features mentioned or evident from the text and/or drawings. All of these different combinations constitute various alternative aspects of the present invention. The embodiments described herein explain the best modes known for practicing the invention and will enable others skilled in the art to utilize the invention.