Evaluation of dynamic elastic properties of wood‐filled polypropylene composites

Dynamic modulus of elasticity (MoE) and shear modulus of wood‐filled polypropylene composite at various filler contents ranging from 10% to 50% was determined from the vibration frequencies of disc‐shaped specimens. Wood filler was used in both fiber form (pulp) and powder form (wood flour). A novel compatibilizer, m‐isopropenyl‐α,α‐dimethylbenzyl‐isocyanate(m‐TMI) grafted polypropylene with isocyanate functional group was used to prepare the composites. A linear increase in dynamic MoE, shear modulus, and density of the composite was observed with the increasing filler content. Between the two fillers, wood fiber filled composites exhibited slightly better properties. At 50% filler loading, dynamic MoE of the wood fiber filled composite was 97% higher than that of unfilled polypropylene. Halpin‐Tsai model equation was used to describe the changes in the composite modulus with the increasing filler content. The continuous improvement in elastic properties of the composites with the increasing wood filler is attributed to the effective reinforcement of low‐modulus polypropylene matrix with the high‐modulus wood filler. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 1706–1711, 2006     

An investigation on the mechanical and dynamic rheological properties of single and hybrid filler/polypropylene composites based on talc and calcium carbonate

Some results of experiments on the mechanical and rheological properties of mineral filled polypropylene were presented. Single filler and hybrid filler composites of talc and calcium carbonate (CaCO₃) were prepared in a co‐rotating twin‐screw extruder. The effect of filler type, filler content, and coupling agent on the mechanical and rheological properties of the polypropylene were studied. The coupling agent was maleic anhydride‐grafted polypropylene (PP‐g‐MA). It was found that the mechanical properties are affected by filler type, filler concentration, and the interaction between filler and matrix. The tensile strength of the composite is more affected by the talc while the impact strength is influenced mostly by CaCO₃ content. The elongation at break of PP/CaCO₃ composites was higher than that of PP/talc composites. The incorporation of coupling agent into PP/mineral filler composites increased the mechanical properties. Rheological properties indicated that the complex viscosity and storage modulus of talc filled samples were higher than those of calcium carbonate filled samples while the tan δ was lower. The rheological properties of hybrid‐filler filled sample were more affected by the talc than calcium carbonate. The PP‐g‐MA increased the complex viscosity and storage modulus of both single and hybrid composites. POLYM. COMPOS., 2009. © 2009 Society of Plastics Engineers     

Mechanical properties and morphologies of polypropylene/single‐filler or hybrid‐filler calcium carbonate composites

Three types of polypropylene (PP) with different intrinsic toughness were used to study the mechanical properties and morphologies of the PP composites filled with single‐filler and hybrid‐filler of calcium carbonate particles. The calcium carbonate particles used were with average particle sizes of 25 μm (CC25), and 0.07 μm (CC0.07), respectively. A hybrid‐filler CaCO₃ named CC25/CC0.07 was used as a mixture of CC25 and CC0.07 (CC25/CC0.07 weight ratio = 1:1). It was found that the type of PP and the particle size of inorganic filler were the two important factors for the determination of mechanical properties of the composites. And the general mechanical properties of the composites filled with hybrid‐filler CaCO₃ were better than those of the composites filled with single‐filler CaCO₃, but the synergistic hybridization effect of the hybrid‐filler CaCO₃ did not exist. The major toughening mechanism of the PP/CC25 composites was the cavitation of the matrix caused by CC25, and the major toughening mechanism of the PP/CC0.07 composites was the pinning effect introduced by CC0.07. For the PP/CC25/CC0.07 composites, the cavitation of the matrix caused by CC25 and the pinning effect introduced by CC0.07 existed simultaneously. And when the intrinsic toughness of the matrix was large enough, the major factor to toughen PP was the pinning effect introduced by CC0.07, otherwise the major factor to toughen PP was the cavitation of the matrix caused by CC25. POLYM. ENG. SCI., 47:95–102, 2007. © 2007 Society of Plastics Engineers     

Mechanical properties of talc‐ and (calcium carbonate)‐filled poly(vinyl chloride) hybrid composites

The main objective of this study was to investigate and compare the mechanical properties of poly(vinyl chloride) (PVC) composites filled with calcium carbonate (CaCO₃), talc, and talc/CaCO₃. Talc and CaCO₃ with different grades were incorporated into the PVC matrix. To produce the composites, the PVC resin, fillers, and other additives were first dry‐blended by using a laboratory mixer before being milled into sheets in a two‐roll mill. Test specimens were prepared by compression molding, after which the mechanical properties of the composites were determined. Single and hybrid filler loadings used were fixed at 30 phr (parts per hundred parts of resin). Talc‐filled composite showed the highest flexural modulus and the lowest impact strength, whereas uncoated, ground, 1‐μm CaCO₃ (SM 90) showed optimum properties in terms of impact strength and flexural modulus among all grades of CaCO₃. It was selected to combine with talc at different ratios in the hybrid composites. The impact strength of the hybrid composites gradually increased with increasing SM 90 content, but the flexural and tensile properties showed an opposite behavior. Hybrid (10 phr talc):(20 phr SM 90)‐filled PVC composite reached a synergistic hybridization with balanced properties in impact strength, as well as flexural and tensile properties. J. VINYL ADDIT. TECHNOL., 2012. © 2012 Society of Plastics Engineers     

Highly filled polyolefin plastomer formulations for possible PVC replacement in flooring

Calcium carbonate highly filled composites of a polyolefin plastomer (POP), and its blends with postconsumer linear low‐density or high‐density polyethylene (PC‐LLDPE or PC‐HDPE) were prepared and evaluated. The mechanical properties of compounded POP and its blends were compared with those of a PVC–calcium carbonate formulation used for flooring applications. Tensile and impact properties of calcium carbonate‐filled POP composites compare very favorably to the PVC‐based formulation at filler loadings as high as 200 phr. Moreover, postconsumer LLDPE or HDPE can replace at least 50% of the POP in these composites without affecting their main properties. DSC analyses indicate that the synergism occurring in mechanical properties for some of the blend compositions, may be related to the ability of the individual polymers to cocrystallize in the respective blends. This article presents the results of a preliminary study. Continued research is expected to contribute toward a complete characterization of the compounded POP/postconsumer PE blends to establish if they can replace plasticized PVC compounds in some or all flooring applications. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 74: 1156–1168, 1999     

Thermal properties and processability of talc‐ and calcium carbonate‐filled poly(vinyl chloride) hybrid composites

The main objective of this investigation was to study and compare the thermal rigidity, thermal stability, and processability of poly(vinyl chloride) (PVC) composites filled with single fillers of talc and uncoated ground CaCO₃ (SM 90) or a hybrid filler consisting of talc/SM 90. To produce the composites, the PVC resin, fillers, and other additives were dry‐blended in a laboratory mixer before being milled into sheets by using a two‐roll mill. Test specimens were prepared by compression molding, after which the thermal properties and processability of the composites were determined. Single and hybrid filler loadings used were fixed at 30 phr (parts per hundred parts of resin). Talc‐filled PVC composite showed slightly better thermal stability and rigidity than the composite filled with SM 90, and its thermal stability and rigidity slightly decreased with SM 90 content increasing from 5 to 25 phr in order to replace talc filler in the hybrid composites. The fusion time of talc‐filled PVC composite was shorter than that of SM 90‐filled PVC composite; thus, the fusion time of hybrid composites increased with increasing SM 90. The fusion torque showed an opposite behavior. J. VINYL ADDIT. TECHNOL., 2012. © 2012 Society of Plastics Engineers     

Coextruded PVC/wood‐flour composites with WPC cap layers

Wood‐plastic composites (WPCs) can absorb moisture in a humid environment owing to the hydrophilic nature of the wood, thereby making the products susceptible to microbial growth and loss of mechanical properties. In this study, rigid poly(vinyl chloride) (PVC)/wood‐flour composites (core layer) were coextruded with either unfilled rigid PVC (cap layer) or rigid PVC filled with a small amount (5–27.5%) of wood flour (composite cap layers) in order to decrease or delay the moisture uptake. The thickness of the cap layer and its composition in terms of wood flour content were the variables examined during coextrusion. Surface color, moisture absorption, and flexural properties of both coextruded and noncoextruded (control) composite samples were characterized. The experimental results indicated that both unfilled PVC and composite cap layers can be encapsulated over rigid PVC/wood‐flour composites in a coextrusion process. The moisture uptake rate was lower when a cap layer was applied in the composites, and the extent of the decrease was a strong function of the amount of wood flour in the cap layer but insensitive to cap layer thickness. Overall, coextruding PVC surface‐rich cap layers on WPCs significantly increased the flexural strength but decreased the flexural modulus as compared with those of control samples. The changes in bending properties were sensitive to both cap layer thickness and wood flour content. J. VINYL ADDIT. TECHNOL., 2008. © 2008 Society of Plastics Engineers     

Mechanical properties of poly(vinyl chloride)/wood flour/glass fiber hybrid composites

Short glass fibers were added to poly(vinyl chloride) (PVC)/wood flour composites as reinforcement agents. Unnotched and notched impact strength of PVC/wood flour/glass fiber hybrid composites could be increased significantly without losing flexural properties by adding type L glass fibers and over 40% of PVC. There was no such improvement when using type S glass fiber. The impact strength of hybrid composites increased along with the increment of the type L glass fiber content at a 50% PVC content. At high PVC contents, impact fracture surfaces were characterized by wood particle, glass fiber breakage and pullout, whereas interfacial debonding was the dominant fracture mode at higher filler concentrations. The significant improvement in impact strength of hybrid composites was attributed to the formation of the three‐dimensional network glass fiber architecture between type L glass fibers and wood flour.     

Damping behavior of wood filled polypropylene composites

The damping coefficient (tanδ) of wood flour filled polypropylene composites, having varying filler concentrations were measured using the free vibration decay of disk‐shaped specimen, vibrating in flexural vibration mode. The damping coefficients decreased with the increase of filler load in composites. There was no significant difference in damping behavior of composites with and without compatiblizer at low filler level (upto 30%). At higher filler loading (>30%), composites with compatiblizer had lower damping coefficient suggesting improved interfacial adhesion between wood and polypropylene. The damping in composite is attributed to the damping because of the composite constituents and damping at the interface. The damping because of interface was estimated using a model and was found to increase with the increase in filler loading. At higher filler content, damping due to interface in composites with compatiblizer was significantly lower than in composites without compatiblizer suggesting a better interfacial adhesion between the wood filler and polypropylene matrix with compatiblizer. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Mechanical properties of particulate‐filler/woven‐glass‐fabric‐filled vinyl ester composites

Studies of the effect of particulate fillers on specific mechanical properties of vinyl ester epoxy (VE) reinforced with woven glass fiber composites were carried out with different filler types and particulate filler contents (1%, 3%, and 5% by weight). Two types of particulate filler were used, i.e., calcium carbonate (CC) and phenolic hollow microspheres (PHMS). The composites were prepared by using a hand lay‐up and vacuum bagging method. Woven glass fabric composites filled with particulate PHMS were observed to have better specific flexural strength and specific impact strength, as well as lower density, than those filled with particulate CC. Morphological features determined by scanning electron microscope (SEM) proved that the PHMS filler experienced good bonding in the VE matrix, a feature which contributed to the improvement in the properties of the composites. The incorporation of particulate fillers into the composites also influenced the storage modulus with a minimal effect on T_g. J. VINYL ADDIT. TECHNOL., 2010. © 2010 Society of Plastics Engineers     

Characterization of melt‐compounded and masterbatch‐diluted polypropylene composites filled with several fillers

The effect of various fillers on the mechanical, barrier, and flammability properties of polypropylene (PP) was studied. PP was filled with 4 wt% of nano‐sized calcium carbonate, titanium dioxide, organoclay, and multiwalled carbon nanotube (MWCNT). For comparison, micron‐sized calcium carbonate was also studied. Two‐step masterbatch dilution approach of the composites suggested no or only minor improvements in Young's modulus and tensile yield strength, whereas their ductility decreased compared to coupling agent‐modified PP matrix. The water vapor transmission results of filled films showed increased permeability compared to their coupling agent‐modified counterpart. Oxygen permeability, however, decreased for the composites. The MWCNT‐filled matrix showed the highest barrier and fire performance, attributed mainly to its higher filler volume content, but also other reasons such as the effect of filler dispersion, composite's thermal stability, and polymer crystallinity were discussed.POLYM. COMPOS., 2013. © 2013 Society of Plastics Engineers     

Performance of hybrid reinforcements in PVC composites. II: Use of surface-modified mica and different cellulosic materials as reinforcements

The effect of the composition of various wood fibers and surface-treated mica as well as different surface treatments of cellulosic materials on the mechanical properties of PVC composites has been evaluated. Cellulosics were surface modified by prior coating with maleic andydride (MA), mixtures of MA and Na-silicate and isocyanate. The filler concentration was fixed at 25 wt%. Both tensile strength and modulus of composities filled solely with mica are superior to those of non-treated wood fiber-filled composities. while the reverse is true for impact strength (except for bagasse-filled composities), ultimate elongation, and tensile toughness. Moreover, the mechanical properties of composities, with the exception of modulus, filled only with mica and/or non-treated wood fibers are inferior to those of unfilled PVC. Compared to non-treated fiber-filled composites, properties improved when surface-modified wood fibers were used alone, or along with mica. Isocyanate-coated wood fibers ranked best with regard to the mechanical properties of the composities. Properties also changed with the change of wood species and compositions of mica and wood fibers. Experimental results indicate good compatibility between surface-treated wood fibers/mica and PVC composities.     

Tensile property and interfacial dewetting in the calcite filled HDPE, LDPE, and LLDPE composites

Mechanical properties and complex melt viscosity of unfilled and the calcite (calcium carbonate: CaCO₃) filled high density polyethylene (HDPE), low density polyethylene (LDPE), and linear low density polyethylene (LLDPE) composites using dumbbell bar and film specimens are studied. In addition, the formation of air holes between calcium carbonate and the resin matrix was investigated from the phase morphology and interfacial behavior between the above constituents upon stretching using scanning electron microscopy. The tensile stress and the complex melt viscosity of the calcite filled (50%) polyethylene composites were higher than that of unfilled ones, implying that the reinforcing effect of calcium carbonate. The crack was initiated up to first 50% elongation along the transverse direction and the formation of air holes was originated by dewetting occurring through machine direction in the interface between calcium carbonate surface and HDPE. The propagation mechanism of the air hole formation was proposed to firstly originate by dewetting up to 300% elongation, and enlarged not only by breaking of a superimposed fibril structure, but also by merging effect air holes between fibrous resin matrix. However, the crack propagation was not observed at the very beginning elongation for the calcite filled LDPE and LLDPE systems. Less fibril structure was observed in LLDPE, then LDPE composites. The observed shape and the average size of the air holes were different from system to system. This sort of different interfacial behavior and mechanical properties may arise from different configuration of polyethylene.     

Mechanical,thermal, and water uptake characteristics of woodflour‐filled polyvinyl chloride/acrylonitrile butadiene styrene blends

Woodflour‐filled composites based on polymeric blends of polyvinyl chloride (PVC) and super high‐impact grade ABS were developed. Mechanical, thermal, and water uptake characteristics of the PVC/ABS matrix and their wood composites were evaluated. In the case of PVC/ABS matrix, the blend at a mass ratio of 50/50 rendered the impact strength with a very high value of up to 65 kJ/m², noticeably higher than those of the parent resins, that is, 6 kJ/m² of PVC and 35 kJ/m² of ABS. Dynamic mechanical analysis thermograms showed two distinct glass transition temperatures (T_gs) that shifted toward each other indicating partial miscibility of the blends. Water absorption of the blends after 24 h immersion was low, that is, within the range of 0.04–0.2 wt % and exhibits a behavior closed to pseudo‐Fickian type. The obtained PVC/ABS wood composites exhibited an increase of flexural modulus as well as T_gs with an increase of woodflour content. Finally, impact strength of the PVC/ABS composites was significantly higher than those of PVC composites or polyethylene composites comparing at the same woodflour content. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Mechanical,flammability, and thermal properties of polyvinyl chloride‐wood composites with carbide slag

Carbide slag, an industrial waste produced by calcium carbide hydrolysis to prepare C₂H₂ gas, was successfully used as inorganic filler in the production of polyvinyl chloride (PVC)‐wood composites. carbide slag had an average diameter of 8.1 μm which thermally decomposed at about 450°C, and its main component was Ca(OH)₂. Incorporating carbide slag into PVC‐wood composites substantially decreased the flexural, tensile, and impact strength of the composites as a result of the poor interfacial adhesion between carbide slag and PVC matrix, which could be evidently observed from the scanning electron microscopy (SEM) study. To give carbide slag better use, silane coupling agent KH570 were chose to modify carbide slag. The results indicated that adding carbide slag modified by KH570 (MCS) into PVC‐wood composites could significantly improve its notched impact strength and flexural modulus. The thermogravimetric analysis (TGA) data showed that with the addition of MCS, composite had better thermal stability. It also turned out that with the addition of MCS, its smoke suppression property and flammability were enhanced effectively. To ensure sufficient properties of PVC‐wood composites, the optimal adding content of MCS was 20 phr and it leaded to remarkable performance (its flexural modulus was 3.4 GPa, notched impact strength was 3.87 KJ/m², limiting oxygen index value was 41.5% and smoke density ranting was 55.1%), all of which endowed PVC‐wood composites better utilization. All the results indicated that the preparation of PVC‐wood composites with carbide slag could resolve environmental pollution, reuse carbide slag in different fields, and provide a new method for resource utilization of carbide slag. POLYM. COMPOS., 38:2898–2906, 2017. © 2015 Society of Plastics Engineers     

Accelerated ultraviolet weathering of PVC/wood‐flour composites

Ultraviolet weathering performance of polyvinyl chloride (PVC) filled with different concentrations of wood flour was studied. Extruded PVC/wood‐flour composite samples were subjected to cyclic ultraviolet lamps/condensation exposures and assessed over a total of 400 and 2600 hours. Each assessment consisted of DRIFTFTIR and XPS collections, contact angle measurement, color measurement, and tensile property testing. The experimental results indicated that wood flours are effective chromophore materials since their incorporation into a rigid PVC matrix accelerated the degradation of the polymeric matrix. Photodegradation converted unfilled PVC samples to a colored material of lower extensibility. Although composite samples exhibited greater discoloration than unfilled PVC samples, they retained all their original strength and stiffness properties even after 2600 hours of cyclic UV irradiation/condensation exposures.     

Thermal property improvement of ethylene‐octene copolymer through the combined introduction of filler and silane crosslink

In many applications, e.g., wire and cable insulation, hot water pipe, high‐temperature properties of polymer are essential. This article presents the use of silane crosslinking together with the addition of particular filler in improving the thermal and mechanical properties of ethylene‐octene copolymer (EOC). The effects of filler surface characteristics on siloxane network structure developed and final properties of the crosslinked products are discussed. The results show an increase in the decomposition temperature of EOC more than 50°C after modification. Only crosslinked composites are able to withstand the high‐temperature environment of aging test which is beyond the melting temperature of the matrix polymer. The crosslinked composites filled with calcium carbonate show superior properties to those with silica, due to a higher crosslink density and tighter network structure formed. The silane coupling mechanism and the presence of bound polymer on silica surfaces cause difficulties for the crosslink formation in the silica filled systems. However, an advantageous influence of both silane coupling and crosslink reaction in the silica filled composites is seen on the enhanced tensile strength and modulus of the materials. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Gas absorption with filled polymer systems

This paper deals with the gas absorption behavior of polymer systems. The emphasis is on the difference between filled and unfilled polymers to explain heterogeneous nucleation in filled polymers. A Foaming Process Simulator has been built to study the gas absorption. It consists of a test chamber that holds the polymer samples. The chamber can be pressurized with gas up to 5000 psi and heated up to 450°F. The gas pressure is monitored by a high‐accuracy pressure transducer and recorded by a data acquisition system. The amount of gas absorbed by a polymer is determined from the pressure change in the test chamber. A rotor applies shear to the polymer melt to investigate the shear effects. Two polymer systems were tested: HDPE with/without talc, and PVC with/without calcium carbonate. The fillers were well dispersed as verified with scanning electron microscope. The tests were done at the melt temperatures from 120°C to 177°C and a saturation pressure of about 18.9 MPa. It was found that the filled polymers absorb more gas compared to the unfilled ones. It is suggested that there is a certain amount of gas accumulated in the filler‐polymer interface. This accumulated gas helps to create cells during the foaming process.     

Performance of bamboo plastic composites with hybrid bamboo and precipitated calcium carbonate fillers

The influences of hybrid bamboo and precipitated calcium carbonate (PCC) fillers in a recycled polypropylene/polyethylene matrix on the properties of bamboo plastic composites were studied. Thermogravimetric and Fourier transform infrared analyses of both thermo‐mechanically refined bamboo fiber (RBF) and ground bamboo particle (GBP) showed relatively higher holocellulose content in RBF, and more effective silane grafting on the RBF surface. The raw PCC particles contained over 95% calcium carbonate, and had an agglomerated form consisting of particles with a mean diameter of about 1.2 microns. Compounding the PCC particles with the plastic resin helped separate and disperse them in the matrix. Measured flexural strength and modulus of PCC‐only‐filled composites increased significantly from 15 to 30% PCC content levels, while the tensile and impact strength of composites decreased with the addition of PCC. For composites with hybrid bamboo and PCC fillers, tensile and flexural moduli were improved with the increase of PCC content. After silane treatment, RBF‐filled composites showed noticeably increased mechanical properties compared with those of GBP‐filled composites. For modulus values, PCC–bamboo–polymer composites were 3–4 times higher than those of PCC–polymer composites at high PCC levels. POLYM. COMPOS., 2012. © 2011 Society of Plastics Engineers     

Comparative Study of the Cure Characteristics and Mechanical Properties of Natural Rubber Filled With Different Calcium Carbonate Resources

Bio‐waste materials such as eggshell (ES) and fishbone (FB) were used as new fillers compared with commercial calcium carbonate (CC) in natural rubber composite. The effect of their presence in the rubber mix on the rheometric study, morphology, mechanical properties, hardness, and abrasion resistance has been investigated at constant filler content (30 phr). The filler and their composites were characterized by Fourier‐transform infrared, X‐ray diffraction, thermogravimetric analysis, and scanning electron microscope (SEM). The results showed that the cure time and scorch time of the composites filled with CC and ES are lower than the composites filled FB filler. On the other hand, composites with ES and CC showed enhanced values of tensile, modulus at 100% and 300% elongation, hardness, and abrasion resistance. The morphological data revealed that CC and ES fillers are better dispersed in the rubber matrix than FB filler. J. VINYL ADDIT. TECHNOL., 26:309–315, 2020. © 2019 Society of Plastics Engineers