Research on OSB Panels from Waste Poplar Veneer

HUA Liang¹, PAN Mingzhu¹, JIU Zhengwan¹, HUA Yukun<sup>1

1</sup> Nanjing Forestry University, Nanjing 210037, Jiangsu, P.R. China
e-mail: jixie@njfu.edu.cn

Keywords: waste poplar veneer, Strand geometry, UF, OSB

ABSTRACT

Waste poplar veneers were crushed into strands and were divided into big, medium and small strands. After drying and mixing with urea-formaldehyde (UF) resin, the strands were oriented into a mat and hot pressed "OSB panels". The results showed that the big strands could be made into panels in appliance with the requirement of OSB/2 class in LY/T1580-2000, corresponding to the Chinese OSB national standard, and the medium and small strands could be made into panels satisfying the specifications of OSB/1. The waste poplar veneers after crushing are suitable to produce eligible UF resin OSB panels.

There are about 3 million m³ waste veneer per year in China .The overall objective of the project was to investigate the technology of manufacturing waste veneer OSB . The waste veneer was crushed into strands and divided into big, medium and small flakes; they occupies about 86%. After drying, mixing with urea-formaldehyde (UF) resin, forming and hot pressing, the "OSB panel" was made. The mechanical properties of the panels were measured. The results showed: the big flakes could be made the panels according with the request of OSB2,dencity 0.60 g/cm³ ,MOR 45 MPa , MOE 6632 MPa, IB 0.47 MPa, TS 12% . The medium and small flakes could be made the panels according with the request of OSB1. The waste veneer after crushing could be made eligible UF resin OSB: big strands UF resin 11%, hot temperature 160 ℃, hot pressing times 0.55 min / mm.

INTRODUCTION
With the quick increase of economy and peoples` living level in our country, more and more panels are needed. The annual yield was up to 74,285,600 m³, there to the plywood was 36.7% equal to 27,287,800 m³. During the processing of veneer manufacture, about 10% was small pieces of veneer, namely every year it will produce 3,000,000 m³ small pieces of veneer. The use of this veneer was for the raw material of particleboard or as fuel. This study is to explore whether this resource can be made into OSB or not.

EXPERIMENTAL METHODS

Material and method
The small pieces of Poplar veneer came from the plywood factory in Subei, with a totally weight of 105 kg, at first it was air-dried, then used in a small mill to make five different sized flakes. The size range and proportion of flakes were shown in Table 1. The moisture content was 8.9%. The resin was UF resin with a solid content of 48%. Table 2 was the test method using three factors and three levels orthonormal test. The factors: flake size, hot pressing time and resin content Three levels: flake size: big, medium and small; hot pressing time 0.40, 0.55, 0.70 min/mm; resin content 7, 9, 11%. The nominal thickness of panels was 10 mm, using the thickness gauge to control the thickness. The enacted density was 0.60 g/cm³.

Table 1: Flake size and proportion (veneer thickness 2.1mm)

 

Figure 1: Small mill

 Figure 2: Flake morphology after crushing

Table 2: Experiment plan

 The panel size pressed in lab was: S= 500 × 500 mm²                       

The measurement of experiment data
According to the request of the corresponding standard, the following physical and mechanical properties were tested: density, 24 h TS, modulus of elasticity (MOE) and MOR, internal bind (IB). The results were listed in Table 3.

 Table 3: Data collection

RESULTS AND DISCUSSION

IB (Internal Bond)
The influence of strand size on IB is shown in Table 4 and Fig. 4.

 Table 4: Influence of strand size on IB

 
Fig. 4: Influence of strand size on IB

From Fig. 4 we can see clearly that there was a strong influence from strand sizes on IB. The bigger the strand size, the smaller the IB.

Influence of using resin content on IB
The influence of using resin content on IB can be seen in Table 5 and Fig. 5.

Table 5: Influence of using resin content on IB

         
 
 
Figure 5: Influence of using resin content on IB

Fig. 5 showed that the maximum of IB appeared when the resin content was 9%.

Influence of hot pressing time on IB
Table 6 and Fig. 6 were the influence of hot pressing time on IB, respectively.

Table 6: Influence of hot pressing time on IB

 


Figure 6: Influence of hot pressing time on IB

From the figure we can see that IB decreased when increasing the hot pressing time, but the change is not significant, the hot pressing time is not the main contributor.
Comparing with the three factors that influence IB, we can obtain Table 7 and Fig. 7.

Table 7: Level difference analysis

 
Figure 7: Main influence factor analysis of IB

Fig. 7 shows that the strand sizes are the main factor to influence IB, the smaller one is resin content and the smallest influence is hot pressing time.ccording to the forestry industry standard of China LY/T 1580 – 2000 about the part of OSB, the OSB can be divided into four classes, shown in table 8.

Table 8: OSB classification

So the value of MOR in this study accorded with the request of OSB/2 completely, namely, it can be used as the bear load board under the room.

MOE and MOR
Effect of strand size on MOE and MOR
The effect of strand size on MOE and MOR can be seen in Table 9 and Fig. 8 and 9.

Table 9: Effect of strand size on MOE and MOR  (MPa)

    

Figure 8: Effect of strand size on MOE

 

Figure 9: Effect of strand size on MOR

The Fig. 8 and 9 both show that there are significant influence of strand size on MOE and MOR, the bigger size has a better property, however, the medium and small size have no big difference.

Effect of resin content on MOE and MOR
The effect of resin content on MOE and MOR is shown in Table 10 and Fig. 10 and 11.

Table 10: Effect of resin content on MOE and MOR

  



Figure 10: Effect of resin content on MOR




Figure 11: Effect of resin content on MOE

When the resin content was 11%, the MOE and MOR appeared the maximum values as shown in Fig. 10 and 11.

Effect of hot pressing time on MOE and MOR
The effect of hot pressing time on MOE and MOR is shown in Table 11 and Fig. 12 and 13. 

Table 11: Effect of hot pressing time on MOE and MOR

     
      


Figure 12: Effect of hot pressing time on MOR

Figure 13: Effect of hot pressing time on MOE

From Fig. 12 and 13, we can see that there was no big difference of the hot pressing time on MOE and MOR.

Main influence factor analysis of MOE and MOR
Main influence factor analysis of MOE and MOR was shown in Table 12 and Fig. 14 and 15. 

Table 12: Main influence factor analysis of MOE and MOR

      


Figure 14: Comparison of the main influence factors of MOR
                                



 Figure 15: Comparison of the main influence factors of MOE

From Fig. 14 and 15, we obtained that the flake size was the main factor, secondly was resin content, the minimum was hot pressing time.

According to the forestry industry standard of the Peoples` Republic of China LY/T 1580 – 2000 about the regulation value of OSB/2 (general name depth is 10 mm) we compared the MOE and MOR. The values obtained from big size flake pressed boards are all beyond the standard; and only the resin content was 11% where the medium size flake pressed boards could accord to the request of standard.

TS (Tensile Strength)
Influence of flake size on TS
The influence of flake size on TS was shown in Table 13 and Fig. 16.

Table 13: Influence of flake size on TS

 
Figure 16: Influence of flake size on TS

The T increased with decreasing flake size as shown in Fig. 16.

Influence of resin content on TS
The influence of flake size on TS was shown in Table 14 and Fig. 17.

Table 14: Influence of resin content on TS

  

Figure 17: Influence of resin content on TS

Fig. 17 showed that TS increased when decreasing resin content.

Influence of hot pressing time on TS
The influence of hot pressing time on TS was shown in Table 15 and Fig.18.

Table 15: Influence of hot pressing time on TS

 


Figure 18: Influence of hot pressing time on TS

Fig.18 showed that TS increased when increasing hot pressing time.

Table 16 and Fig. 19 show the comparison of level difference of the three main influence factors.

Table 16: Comparison of main influence factor on TS

 


Figure 19: Comparison of main influence factor on TS

Fig. 19 showed that the flake size was the main factor, secondly was resin content, the minimum was hot pressing time.

According to the forestry industry standard of the Peoples` Republic of China LY/T 1580 – 2000 about the part of OSB, we compared the experiment value with the regulation value of this standard. Data analysis was shown in Table 17.

Table 17: Comparison of the experiment value and standard value

Table 17 shows that all experiment values are smaller than standard values, which accorded to the request.

Optimize test
According to the experiment result, the experiment plan was optimized (Table 18) and the property was measured (Table 19).

Table 18: Optimize test plan

Table 19: Main properties of optimized test

CONCLUSIONS

From the analysis of results, we obtained the optimized test plan. The waste veneer OSB had a better quality and superior property, which could achieve the use standard of OSB/2. Table 3 showed that the medium and small size flakes could also attain the standard of OSB/1.

The flakes that came from the crushed materials were tested, which accorded to the OSB standard (OSB/1 and OSB/2). The flake size was up to 80%. If we mass produce, the miller should be improved, which can enhance the efficiency of crushing the material and obtain a more uniformity flake size. We think that the pieces coming from the plywood remains can be made into OSB/1 and OSB/2. This can not only save the raw material but also decrease the dash giving off.

REFERENCES

Hua, Y., Chen, Z., and Zhou, D. (1993) Research of OSB World Forestry Research. The Scientific and Technological Commission, Ministry of Forestry: 1-174   

Hua, Y., Hong, Z. and Associates (1994) The Synthetic Utilization of Fast-Growing Poplar in Wood-Based Panels. Properties and Utilization of Fast-Growing Trees, China Forestry Publishing House.  Beijing : 185-189.

Lu, X. , Hua, Y. (1994) OSB Made with Poplar Slash. Properties and Utilization of Fast-Growing Trees, China Forestry Publishing House. Beijing: 303 -311.

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