^{1}

^{*}

^{2}

^{3}

^{1}

^{1}

^{4}

^{3}

The aim of this work was to develop and characterize a polyester matrix composite material based on
*Canarium schweinfurthii* Engl core granule. The particle size and the mass fractions of these cores used as fillers in this composite were the two optimization parameters. The experimentation of the twelve sample areas was based on the following optimization parameters: Three particles sizes of 80 < T
_{1} < 160 μm, 160 < T
_{2} < 315 μm and 315 < T
_{3} < 630 μm and four mass fractions of 0%, 40%, 45% and 50%. The composites were produced by hand lay-up method. The physical and mechanical parameters concerned by this study are: absolute density, compressive stress at break, Young’s modulus in bending and coefficient of static friction with wood. Each of these parameters was determined by testing ten specimens per sampling area. It was found that the absolute density varies very little as a function of particle size and mass fraction. This absolute density is between 1200 and 1232 kg
·m<sup>-3</sup>, which allows us to admit that this composite belongs to the family of light materials. The maximum compressive stress at break was obtained for the formulation 40% filler of size T
_{3}. This compressive stress at maximum rupture is in the range of 199.14 MPa. From 0% to 45% of filler, the flexural Young’s modulus of the composite increases whatever the particle size. The highest value is obtained for T
_{2} particle size,
*i.e.* 13.11 GPa. The static friction coefficient of the composite on wood increases as the filler content varies from 0.30 to 0.42. Thus, in view of the properties obtained, this composite can be used as alternative solutions in industrial applications, for the manufacturing of shoe heel, house ceiling, floors for housing and table support.

Developing countries derive most of their income from agriculture. From this agriculture generally come plant by-products, among which plant hard shells and cores figure prominently. These hard cores include those of the Canarium schweinfurthii Engl, which is an oilseed of the Burseraceae family, with an ellipsoidal drupe that turns green when it grows and turns purplish at maturity [

In the literature, many works have been done on the Canarium schweinfurthii Engl cores. Yilleng et al. (2013) studied the use of these cores as activated carbon [

The development in science and technology required a variety of polymer with good properties and low cost. Therefore, polymer composites were considered to be among the more promising approaches to yield new materials and have been investigated extensively. In recent years, many studies have been dedicated to utilizing lignocellulosic fillers such as coconut shell, wood, pineapple leaf, palm kernel shell, etc. as fillers in order to replace synthetic fillers through utilization of natural fillers or reinforcement in thermoplastic and thermoset polymer composites in an attempt to minimize the cost, increase productivity and enhance mechanical properties of product [

Extensive studies on the preparation and properties of thermosetting and thermoplastic composites filled with jute, sisal, coconut shell, coir, bagasse, Rice-husk etc. have been investigated. The use of biomaterials in general and agro-waste in particular is a subject of great interest nowadays not only from the technological and scientific points of view but also socially and economically in terms of employment, cost and environmental issues [

So far no work has been done on the development of a composite based on these particulates. Unsaturated Polyester and urea formaldehyde resins are the two most available matrices in Cameroon, among which unsaturated polyester resins are used extensively in the composites industry because of their good mechanical properties, low cost and ease of use [

In the light of the above, the present study is channeled towards producing a composite material using a thermoset polymer (Unsaturated polyester) as the matrix and a lignocellulosic material (Canarium Schweinfurthii Engl cores (NCS) particulates) as the reinforcing filler so as to further establish the use of agricultural wastes as reinforcements in polymer matrices. Also the study tends to use mechanical and physical properties as criteria in establishing the possibility of using lignocellulosic materials as reinforcing fillers in thermoset polymers.

The fruits of Canarium Schweinfurthii Engl whose cores are exploited in this study come from the same tree in the Bayangam subdivision from West Cameroon Region;

After harvesting, separation of the core from the pulp was achieved by softening the pulp in hot water. The optimal couple: heating water temperature/holding time at this temperature, leading to softening of the fruit, is between 50˚C/10min and 55˚C/20min [

After obtaining the powdered particles, the sieve sizes 80, 160, 315 and 630 µm were used to determine the various usable grain sizes by sieve analysis method. About 5285.8 g of CS powder was put over the sieve shaker and shaken it for 20 min, after this operation, we have obtained a distribution of granule sizes according to the masses of granules, as presented in

In order to reduce the environmental pollution caused by these cores, we decided to use higher volume fractions of filler. The basic formulation result shown that, there was no good cohesion between the filler and the resin above 50% filler. So for the rest of our work, we decided to use the fractions 40%, 45% and 50% filler for the preparation of sample in comparison of a sample made up without incorporated filler (0%). Then for the formulation of the composite, 4 discontinuous ranges of filler content and 3 grain sizes were used according to

Size (µm) | 80 < T_{1} < 160 | 160 < T_{2} < 315 | 315 < T_{3} < 630 | T_{4} > 630 | Total |
---|---|---|---|---|---|

Mass (g) | 656.4 | 1602.2 | 1887.6 | 1139.6 | 5285.8 |

Mass (%) | 12.42 | 30.31 | 35.71 | 21.56 | 100 |

Sizes T_{1}, T_{2} and T_{3} have been used in this work.

Aggregate size | %filler content | |||
---|---|---|---|---|

0 | 40 | 45 | 50 | |

T_{1} | 0T_{1} | 40T_{1} | 45T_{1} | 50T_{1} |

T_{2} | 0T_{2} | 40T_{2} | 45T_{2} | 50T_{2} |

T_{3} | 0T_{3} | 40T_{3} | 45T_{3} | 50T_{3} |

The samples have been codified as shown in

The volume fractions of the components were determined using the masses of each component through the principle of mixture law. Polyester and hardener were mixed in a container and stirred well for 1 - 2 minutes. Before the mixture was placed inside the mould, the mould has initially been polished with a release agent to prevent the composites from sticking onto the mould upon removal. Finally, the mixture was poured into the mould with four compartments of identical dimensions 150 mm × 75 mm × 12 mm, and left at room temperature for 3 hours until the mixture was hardened by hand lay-up method. When the composite was hardened, it was removed from the mould and placed inside an oven for 3 hours at 105˚C for curing.

The density was determined using pycnometers by the method of successive weighing according to standard NF P 94-054 [

The compression test was conducted using the universal compression testing machine. We used ten specimens of dimensions 15 mm × 15 mm × 15 mm, in each category.

The specimen was placed between two plates. The test consists of compressing this specimen until breakage.

By increasing the compressive force to be applied to the specimen until breakage in order to obtain the maximal compressive stress at breakage.

Flexural test was performed using three point bending method according to ASTM D790-03 procedure shown in

Ten specimens of each sample of section b × e = 15 × 1.2 mm^{2} and length L = 150 mm of our composite were subjected to 3-point bending. For this purpose,

Sample code | Designation |
---|---|

0CT | Composite realized with 0% of filler content |

40CT_{1} | composite with 40% of filler content of particle sizes between 80 and 160 µm. |

45CT_{1} | composite with 45% of filler content of particle sizes between 80 and 160 µm. |

50CT_{1} | composite with 50% of filler content of particle sizes between 80 and 160 µm. |

40CT_{2} | composite with 40% of filler content of particle sizes between 160 and 315 µm. |

45CT_{2} | composite with 45% of filler content of particle sizes between 160 and 315 µm. |

50CT_{2} | composite with 50% of filler content of particle sizes between 160 and 315 µm. |

40CT_{3} | composite with 40% of filler content of particle sizes between 315 and 630 µm. |

45CT_{3} | composite with 45% of filler content of particle sizes between 315 and 630 µm. |

50CT_{3} | composite with 50% of filler content of particle sizes between 315 and 630 µm. |

the universal bending-compression testing machine of CONTROLS brand was used. The tests carried out at room temperature consisted in imposing the load F in increments. For each value of F, the deflection y_{c} from point C was taken with the help of a digital comparator with a precision of 0.001. The slope α of the linear part of the curve of F as a function of y_{c} makes it possible to deduce the bending Young’s modulus E from Equation (1) below.

E = α L 3 48 I (1)

where I is the quadratic moment of the cross-section of the sample.

The static coefficient of friction was determined experimentally according to Coulomb’s law. For each test, a sample of mass m is placed on the AC side of _{max} at which the sample starts to move. The static friction coefficient μ_{s} is calculated by Equation (2).

μ s = F t F N = m g sin θ max m g cos θ max = tan θ max (2)

The mean value and standard deviation of the density for each sample used are presented in

It can be seen that there is a slight variation of the density in the sample field and it lies between 1200 and 1232.10 kg·m^{−3}.

After compression testing, the mean value and standard deviation of the maximal compressive stress for each sample used are presented in

It can be seen from

After this testing procedure, the mean value and standard deviation of the flexural Young modulus for different sample used are presented in

Sample | 0CT | 40CT_{1} | 45CT_{1} | 50CT_{1} | 40CT_{2} | 45CT_{2} | 50CT_{2} | 40CT_{3} | 45CT_{3} | 50CT_{3} |
---|---|---|---|---|---|---|---|---|---|---|

Mean value (kg·m^{−3}) | 1200 | 1221.93 | 1222.26 | 1232.10 | 1224.79 | 1228.84 | 1231.35 | 1223.08 | 1224.46 | 1228.84 |

Standard deviation | 0 | 2.37 | 2.74 | 3.3 | 2.18 | 3.22 | 4.3 | 3.87 | 3.3 | 3.61 |

Sample | 0CT | 40CT_{1} | 45CT_{1} | 50CT_{1} | 40CT_{2} | 45CT_{2} | 50CT_{2} | 40CT_{3} | 45CT_{3} | 50CT_{3} |
---|---|---|---|---|---|---|---|---|---|---|

Mean value (MPa) | 55 | 105.58 | 95.91 | 70.71 | 150.5 | 146.13 | 134.36 | 199.14 | 193.91 | 164.51 |

Standard deviation | 0 | 1.77 | 3.43 | 5.08 | 2.87 | 1.36 | 2.44 | 1.38 | 3.62 | 3.12 |

Sample | 0CT | 40CT_{1} | 45CT_{1} | 50CT_{1} | 40CT_{2} | 45CT_{2} | 50CT_{2} | 40CT_{3} | 45CT_{3} | 50CT_{3} |
---|---|---|---|---|---|---|---|---|---|---|

Mean value (GPa) | 3.56 | 12.54 | 9.12 | 6.39 | 10.93 | 13.11 | 8.99 | 7.35 | 9.31 | 5.78 |

Standard deviation | 0 | 2.47 | 1.6 | 1.31 | 2.28 | 1.98 | 2.06 | 2.45 | 1.08 | 3.21 |

It is observed that at 40% of filler content, formulation T_{1} is the stiffest, while at 45% of filler content, formulation T_{2} is the most rigid.

Up to 45% filler content, the Young’s modulus increases and reaches its maximum of 13.11 GPa at 45% filler content for a size of T_{2}.

The mean value and standard deviation of the friction coefficient for different sample on wood are presented in

The static friction coefficient of the composite on wood increases with the filler content and ranged from 0.30 to 0.42.

Sample | 0CT | 40CT_{1} | 45CT_{1} | 50CT_{1} | 40CT_{2} | 45CT_{2} | 50CT_{2} | 40CT_{3} | 45CT_{3} | 50CT_{3} |
---|---|---|---|---|---|---|---|---|---|---|

Mean value | 0.30 | 0.4 | 0.41 | 0.42 | 0.36 | 0.38 | 0.41 | 0.35 | 0.38 | 0.42 |

Standard deviation | 0 | 0.018 | 0.019 | 0.013 | 0.02 | 0.017 | 0.011 | 0.016 | 0.021 | 0.028 |

Properties | CS/polyester composite | Midrib Coconut Palm Leaf Reinforced Polyester Composite | Sisal/polyester composite | Bamboo/polyester composite | ||||
---|---|---|---|---|---|---|---|---|

% filler content | Grain size | |||||||

0 | 40 | 45 | 50 | |||||

Compressive stress at break (MPa) | 55 | 105.58 | 95.91 | 70.71 | T_{1} | 77.65 [ | ||

55 | 150.50 | 146.13 | 134.36 | T_{2} | ||||

55 | 199.14 | 193.91 | 164.51 | T_{3} | ||||

Young’s modulus in flexion (GPa) | 3.56 | 12.54 | 9.12 | 6.39 | T_{1} | 8.28 [ | 2.49 [ | 3.7 [ |

3.56 | 10.93 | 13.11 | 8.99 | T_{2} | ||||

3.56 | 7.35 | 9.31 | 5.78 | T_{3} |

literature, for unsaturated polyester matrix composites produced by hand lay-up method.

The present study centered on the production and the characterization of polyester/Canarium schweinfurthii Engl cores particulates. In order to achieve this objective, an experimental approach based on the formulation and elaboration of composite samples for which the size and filler content vary, was adopted. Polyester resin was used as a matrix. For the better achievement, this study has focused on shell conditioning and sample formulation. The composites were produced by hand lay-up method, and physical-chemical and mechanical tests were carried out on previously treated and conditioned samples at room temperature, and the physical and mechanical parameters were determined. It was observed that the density varied very little in the sample field from 1200 to 1232.10 kg·m^{−3}. Depending on the fillers proportions of Canarium schweinfurthii Engl cores, the greatest compressive stress at fracture was obtained at 40% fillers. Our findings also reveal that, the compressive stress at break is higher for T_{3} particles size, which leads us to the highest value of 199.14 MPa. Up to 45% filler content, the Young’s modulus increases and reaches its maximum of 13.11 GPa at 45% filler content for a size T_{2}. Basically, the static friction coefficient of the composite on wood increases with the filler content and varies from 0.30 to 0.42. Thus, in view of the properties obtained, this composite can be used as an alternative solution for structural materials in industrial applications, such as shoe heel, house ceiling, floors for housing and table support.

The authors declare no conflicts of interest regarding the publication of this paper.

Ndapeu, D., Tamwo, F., Nganou Koungang, M.B., Tchuen, G., Sikame Tagne, N.R., Bistac, S. and Njeugna, E. (2020) Elaboration and Characterization of a Composite Material Based on Canarium schweinfurthii Engl Cores with a Polyester Matrix. Materials Sciences and Applications, 11, 204-215. https://doi.org/10.4236/msa.2020.113014